Battery cell, battery, and electric device

Abstract

The application discloses a battery monomer, a battery and a power utilization device. The battery monomer provided by the application comprises a positive pole piece, the positive pole piece comprises a current collector and an active material film layer which are arranged in a stack, the active material film layer comprises a composite conductive agent, the composite conductive agent comprises: one-dimensional carbon material, including first carbon nanotubes and second carbon nanotubes, the specific surface area of the first carbon nanotubes is less than or equal to 100 m 2 / g, and the specific surface area of the second carbon nanotubes is greater than or equal to 800 m 2 / g; and two-dimensional carbon material, including one or more of conductive graphite and graphene. The two types of carbon nanotubes with different specific surface areas are cross-paired, the space of the positive pole piece can be fully utilized, the two-dimensional carbon material is further matched, the contact area of the carbon nanotubes can be further increased, the use amount of the composite conductive agent can be reduced while the conductivity of the positive pole piece is improved, and the energy density of the battery is improved.

Description

Technical Field

[0001] This application relates to the field of batteries, and in particular to a battery cell, a battery, and an electrical device. Background Technology

[0002] Battery cells possess characteristics such as high capacity and long lifespan, and are therefore widely used in electronic devices, such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools. Due to the significant advancements in battery cell technology, higher performance requirements have been placed on them.

[0003] The energy density of individual battery cells still needs to be improved. Summary of the Invention

[0004] This application provides a battery cell, a battery, and an electrical device that can improve the energy density of the battery cell.

[0005] In a first aspect, this application provides a battery cell, which includes a positive electrode sheet, the positive electrode sheet including a current collector and an active material film layer stacked together; the active material film layer includes a composite conductive agent, a binder and active material particles; the composite conductive agent includes:

[0006] One-dimensional carbon materials, including first carbon nanotubes and second carbon nanotubes, wherein the specific surface area of ​​the first carbon nanotubes is ≤100 m². 2 / g, the specific surface area of ​​the second carbon nanotube is ≥800m² 2 / g;

[0007] Two-dimensional carbon materials, including one or more of conductive graphite and graphene.

[0008] Therefore, one-dimensional carbon nanotubes possess good electrical conductivity and a specific surface area ≤100m². 2 The high space utilization of the first carbon nanotubes ( / g) helps reduce the volume percentage of the composite conductive agent in the active material film, resulting in a specific surface area ≥800m². 2 The second carbon nanotube, with a surface area difference of ≥700m², can form a more conductive network, which is more conducive to long-range electron transport. 2 The cross-combination of two types of carbon nanotubes per g can fully utilize the space of the positive electrode while achieving good conductivity. At the same time, the combination with two-dimensional carbon materials can increase the contact area of ​​carbon nanotubes. The active material particles are surrounded and wrapped by the composite conductive agent, and the electrons released or absorbed by the active material particles can be stably transported from more directions and over shorter distances. Thus, the conductivity of the positive electrode can be improved while reducing the amount of composite conductive agent used, and the space utilization rate is improved, thereby increasing the energy density of the battery.

[0009] In some embodiments, the mass content of the first carbon nanotube in the active material film layer is 0.2% to 0.5%.

[0010] Therefore, given the relatively small specific surface area of ​​the first carbon nanotubes, using first carbon nanotubes within the aforementioned mass content range can reduce the consumption of binder while still achieving a certain level of conductivity in the electrode. Simultaneously, the electrode exhibits good cohesion and adhesion. Furthermore, the lower cost of first carbon nanotubes reduces formulation costs.

[0011] In some embodiments, the mass content of the second carbon nanotube in the active material film layer is 0.05% to 0.1%.

[0012] Therefore, a very small amount of second carbon nanotubes with a large specific surface area can be combined with first carbon nanotubes with a small specific surface area within the aforementioned mass content range to form a carbon nanotube cross region with better conductivity. This can better cover the active material particles, improve conductivity and space utilization, and further enhance energy density.

[0013] When the mass content of the second carbon nanotube in the active material film is within the above-mentioned range, and it is combined with other conductive agents, a battery cell with good high-temperature storage performance, high-temperature capacity retention rate and long cycle retention rate can also be obtained.

[0014] In some embodiments, the mass content of the two-dimensional carbon material in the active material film layer is 0.3% to 0.5%.

[0015] Therefore, based on the selection of carbon nanotubes mentioned above, by combining them with two-dimensional carbon materials with a mass content of 0.3% to 0.5%, it is possible to form an anisotropic multidimensional conductive network using a small amount of composite conductive agent, thereby reducing the amount of composite conductive agent required while maintaining good conductivity.

[0016] Furthermore, based on this, the combination of the aforementioned two-dimensional carbon material with a mass fraction of 0.2% to 0.5% of first carbon nanotubes and a mass fraction of 0.05% to 0.1% of second carbon nanotubes can achieve high energy density, better storage performance at high temperatures, low volume expansion rate, and good cycle performance.

[0017] In some embodiments, the mass content of the composite conductive agent in the active material film layer is 0.55% to 1.1%.

[0018] Therefore, the composite conductive agent formed by combining different carbon nanotubes and two-dimensional carbon materials has good conductivity and can reduce the mass content of the conductive agent in the active material film. For example, the mass content of the composite conductive agent in the active material film can be controlled within the above range, thereby increasing the mass content of the active material particles and improving the energy density of the battery cell.

[0019] Furthermore, on the other hand, positive electrode sheets with the mass content of composite conductive agent in the active material film layer controlled within the above range can still have good electrode adhesion and cohesion, low elongation, and improved high-temperature storage performance and cycle performance of battery cells.

[0020] In some embodiments, the composite conductive agent and binder have a surface coverage of 3% to 40% on the active material particles.

[0021] Thus, the conductive agent-binder domain, composed of the conductive agent and the binder, covers the surface of the active particles or fills the spaces between them. Appropriate coverage can reduce ion transport paths while ensuring electron transport, thereby improving electrical performance.

[0022] In some implementations, during Raman spectroscopy testing of two-dimensional carbon materials, I d / I g The value is 0.5 to 0.9, I d This indicates that the Raman displacement is at 1300 cm. -1 ~1400cm -1 The d-peak intensity within the range, I g This indicates that the Raman shift is at 1530 cm. -1 ~1630cm -1 The intensity of the g peak within the range.

[0023] Therefore, I of two-dimensional carbon materials d / I g Within the aforementioned range, appropriate structural defects and graphitization levels, combined with the surface coverage of the active material particles, can further reduce the impedance of the positive electrode, thereby giving the positive electrode better conductivity.

[0024] In some embodiments, the minimum length of the second carbon nanotube is ≥10μm, and the maximum diameter is 1nm to 3nm.

[0025] Therefore, the second carbon nanotube, with its large specific surface area, thinner diameter, and longer length, can form a more continuous electron transport path. On the other hand, its higher surface energy allows it to connect and encapsulate more first carbon nanotubes, active material particles, and binders, which helps to reduce the amount of composite conductive agents and binders used.

[0026] In some embodiments, the maximum length of the first carbon nanotube is ≤20μm and the minimum diameter is 30nm~150nm.

[0027] Therefore, the first carbon nanotube, which has a larger diameter and shorter length, has better mechanical stability and thermal conductivity, which is conducive to heat dissipation and can improve the capacity retention rate of the battery at high temperatures. The short and thick first carbon nanotube also facilitates the penetration of electrolyte.

[0028] In some embodiments, the first carbon nanotube and the second carbon nanotube each independently include multi-walled carbon nanotubes, single-walled carbon nanotubes, or combinations thereof.

[0029] In some embodiments, the conductive graphite is flake graphite with a specific surface area of ​​10 m². 2 / g~30m 2 / g, with an average flake diameter of 1μm to 10μm.

[0030] Therefore, under cold pressing of the positive electrode sheet, two-dimensional flake graphite can promote the slippage of active particles, reduce the effect of particles on the substrate, and reduce the elongation of the positive electrode sheet. The combination of flake graphite with the above-mentioned specific surface area and sheet diameter range with one-dimensional carbon materials is more conducive to improving conductivity while reducing the elongation of the positive electrode sheet.

[0031] In some embodiments, the binder content in the active material film layer is 0.3% to 0.7% by mass.

[0032] Therefore, by using the composite conductive agent of the present application, the amount of binder can be reduced, the mass content of the binder is lower, the side reaction gas generation under high cutoff voltage can be reduced, and the cell volume expansion can be suppressed.

[0033] In some embodiments, the mass content of active substance particles in the active substance film layer is 97.7% to 99.15%.

[0034] Therefore, a higher mass content of the positive electrode active material can improve the energy density of the battery.

[0035] In some embodiments, the average particle size Dv50 of the active material particles is 3 μm to 5 μm, and the specific surface area is 0.5 m². 2 / g~1m 2 / g.

[0036] Therefore, the compaction density of small-particle positive electrode active material is relatively low. The combination of the small-particle positive electrode active material with the composite conductive agent can effectively improve the compaction density of the positive electrode sheet formed by the small particles, so as to obtain a higher energy density.

[0037] In some embodiments, the active material particles include a matrix material and a carbon material coated on at least a portion of the surface of the matrix material; the average particle size Dv50 of the active material particles is 4 μm to 15 μm, and the specific surface area is 5 m². 2 / g~20m 2 / g.

[0038] In some embodiments, the active material particles include one or more of lithium nickel cobalt manganese oxide materials, lithium nickel manganese oxide materials, lithium manganese oxide materials, lithium cobalt oxide materials, lithium-rich manganese-based materials, lithium iron phosphate materials, and lithium manganese iron phosphate materials.

[0039] In some embodiments, the binder has a weight-average molecular weight of 2,000,000 to 4,000,000 and a crystallinity of 15% to 55%.

[0040] Therefore, using the aforementioned binders with high weight-average molecular weight and suitable crystallinity can further reduce the amount of binder added to the active material film layer, thereby increasing energy density. The synergistic effect of the aforementioned binders with suitable weight-average molecular weight and crystallinity ranges, along with carbon nanotubes, can simultaneously reduce the amount of both added, further improving battery performance.

[0041] Furthermore, even with a low addition amount, the positive electrode sheet exhibits good adhesion and cohesion, which helps maintain the structural stability of the positive electrode sheet, improves the problem of poor interparticle contact caused by the expansion and contraction of the main material, and enhances cycle performance and storage performance.

[0042] In some embodiments, the adhesive includes an adhesive with fluorinated functional groups, which includes one or more of PVDF, carboxylated polyvinylidene fluoride, polyhexafluoroethylene, polytetrafluoroethylene, and polyhexafluoropropylene-polyvinylidene fluoride copolymer.

[0043] In some embodiments, the compaction density of the positive electrode sheet is 3.0 g / cm³. 3 ~3.6g / cm 3 .

[0044] In some embodiments, the positive electrode sheet has a compaction density of 3.3 g / cm³. 3 The elongation rate is less than 0.7%.

[0045] In some implementations, the bonding force of the positive electrode sheet is >15 N / m.

[0046] In some implementations, the cohesive force of the positive electrode is >100 N / m.

[0047] In some embodiments, the battery cell further includes a negative electrode sheet, which includes a current collector and a negative electrode active material layer containing negative electrode active material stacked together. The negative electrode active material layer includes graphite, conductive carbon black, styrene-butadiene rubber and sodium carboxymethyl cellulose in a weight ratio of (95.8-98):(0.4-1):(0.6-2.0):(1.0-1.2).

[0048] In some embodiments, the battery cell further includes an electrolyte comprising an organic solvent and an electrolyte salt, wherein the solvent comprises ethylene carbonate and ethyl methyl carbonate in a volume ratio of (2-5):(5-8).

[0049] Secondly, embodiments of this application provide a battery including a housing and a battery cell according to any embodiment of the first aspect of this application, wherein the battery cell is housed within the housing.

[0050] Thirdly, embodiments of this application provide an electrical device configured to receive electrical energy supplied by a battery from any embodiment of the second aspect of this application. Attached Figure Description

[0051] 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.

[0052] Figure 1 This is a schematic diagram of a secondary battery cell according to one embodiment of this application;

[0053] Figure 2 This is a schematic diagram of the structure of a battery pack according to one embodiment of this application;

[0054] Figure 3 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;

[0055] Figure 4 This is an electron microscope image of the active material film layer of the positive electrode sheet of the battery cell in Example 1;

[0056] Figure 5 This is an electron microscope image of the active material film layer of the positive electrode sheet of the battery cell in Example 1.

[0057] The annotations in the attached figures are explained as follows:

[0058] 1 battery pack; 5 individual secondary battery cells.

[0059] The accompanying drawings are not necessarily drawn to scale. Detailed Implementation

[0060] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the conductive paste, current collector, secondary battery, 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 a full understanding of this application by those skilled in the art 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 also 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 of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

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

[0066] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0067] Unless otherwise specified, in this disclosure, the terms "first," "second," etc., are used to distinguish different objects, rather than to describe a specific order or primary / secondary relationship.

[0068] In this disclosure, the terms "multiple" or "a variety" refer to two or more kinds.

[0069] In the description of the embodiments of this disclosure, unless otherwise specified, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0070] Unless otherwise stated, the test temperature for all parameters mentioned in this disclosure is 25°C.

[0071] The secondary battery cell mentioned in the embodiments of this disclosure can independently perform charge and discharge functions. After discharge, it can be reactivated by charging to allow for continued use. The secondary battery cell can be cylindrical, cuboid, or other shapes, and the embodiments of this disclosure are not limited in this regard. Figure 1 This is a cuboid-shaped secondary battery cell used as an example.

[0072] The secondary battery cells provided in the embodiments of this disclosure may include, but are not limited to, lithium battery cells and sodium battery cells, such as lithium-ion battery cells, sodium-ion battery cells, lithium metal battery cells, sodium metal battery cells, etc. The secondary battery cells provided in the embodiments of this disclosure include electrode assemblies.

[0073] The electrode assembly can be a wound structure or a stacked structure, and this disclosure does not limit this. The secondary battery cell also includes an outer packaging, which can be used to encapsulate the electrode assembly. The outer packaging can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging can also be a flexible package, such as a pouch. The material of the flexible package can be plastic, such as one or more of aluminum-plastic film, polypropylene, polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0074] The battery apparatus mentioned in the embodiments of this disclosure may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple secondary battery cells connected in series, parallel, or mixed connections via a busbar. In some embodiments, the battery cell assembly is typically formed by arranging multiple secondary battery cells.

[0075] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple secondary battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple secondary battery cells together with cable ties.

[0076] In some implementations, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0077] 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.

[0078] As an example, the battery cell assembly can also be housed within a housing by directly fixing multiple secondary battery cells to the housing. As an example, the housing may include a first housing and a second housing. The first and second housings are fastened together to form a closed space inside the housing for accommodating the battery cell assembly. Here, "closed" refers to covering or shutting off; it can be sealed or not sealed. The first housing may be a top cover or a bottom plate.

[0079] 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.

[0080] In some implementations, 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.

[0081] The technical solutions described in this disclosure are applicable to various electrical devices that use secondary battery cells or battery devices, such as, but not limited to, mobile devices (e.g., mobile phones, tablets, 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. The secondary battery cells or battery devices are used to store or provide electrical energy. The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0082] To enhance the competitiveness of battery cells, increasingly higher energy density is required. Maximizing compaction density within a limited volume is a feasible method to improve energy density. However, increasing compaction density is constrained by various factors, including the properties of the main material itself (true density, morphology, particle size, etc.) and the formulation of the positive electrode sheet. Positive electrode sheets generally consist of active material particles, conductive agents, and binders. To increase the proportion of active material particles, the compaction density of the positive electrode sheet can be improved by optimizing the characteristics and dosage of the conductive agent.

[0083] In view of the above problems, this application proposes a battery cell, which includes a positive electrode sheet, and the positive electrode sheet includes a current collector and an active material film layer stacked together; the active material film layer includes a composite conductive agent, a binder and active material particles; the composite conductive agent includes a one-dimensional carbon material, including a first carbon nanotube and a second carbon nanotube, wherein the specific surface area of ​​the first carbon nanotube is ≤100m². 2 / g, the specific surface area of ​​the second carbon nanotube is ≥800m² 2 / g; One-dimensional carbon materials, carbon nanotubes, exhibit good electrical conductivity and a specific surface area ≤100m². 2 The high space utilization of the first carbon nanotubes ( / g) helps reduce the volume percentage of the composite conductive agent in the active material film, resulting in a specific surface area ≥800m². 2 The second carbon nanotube, with a surface area difference of ≥700m², can form a more conductive network, which is more conducive to long-range electron transport. 2 The cross-combination of two types of carbon nanotubes per g can fully utilize the space of the positive electrode while achieving good conductivity. At the same time, it is combined with two-dimensional carbon materials, including one or more of conductive graphite and graphene. The active material particles are surrounded and wrapped by the composite conductive agent. Electrons released or absorbed by the active material particles can be stably transported from more directions and over shorter distances. This can improve the conductivity of the positive electrode while reducing the amount of composite conductive agent used, and improve the space utilization rate, thereby increasing the energy density of the battery.

[0084] The technical solution of this application will now be described in detail.

[0085] battery cell

[0086] In a first aspect, this application proposes a battery cell, which includes a positive electrode sheet, the positive electrode sheet including a current collector and an active material film layer stacked together; the active material film layer includes a composite conductive agent, a binder, and active material particles; the composite conductive agent includes a one-dimensional carbon material, including a first carbon nanotube and a second carbon nanotube, wherein the specific surface area of ​​the first carbon nanotube is ≤100m². 2 / g, 20m optional 2 / g~100m 2 / g; Specific surface area of ​​the second carbon nanotube ≥800m² 2 / g, 810m optional 2 / g~1200m 2 / g; Two-dimensional carbon materials, including one or more of conductive graphite and graphene.

[0087] One-dimensional carbon materials, such as carbon nanotubes, exhibit good electrical conductivity. First-type carbon nanotubes with a specific surface area ≤100 m² / g have high space utilization, which helps reduce the volume percentage of composite conductive agents in the active material film. Second-type carbon nanotubes with a specific surface area ≥800 m² / g can form more conductive networks, further facilitating long-range electron transport. Combining two types of carbon nanotubes with a specific surface area difference ≥700 m² / g allows for efficient use of the positive electrode space while achieving good conductivity. Furthermore, combining them with two-dimensional carbon materials increases the contact area of ​​the carbon nanotubes. Simultaneously, the active material particles are surrounded by the composite conductive agent, allowing electrons released or absorbed by the active material particles to be stably transported from more directions and over shorter distances. This reduces the amount of composite conductive agent used while improving the conductivity of the positive electrode, enhancing space utilization, and increasing the battery's energy density. For example, the specific surface area of ​​the first-type carbon nanotube can be 20 m² / g. 2 / g、40m 2 / g、60m 2 / g、80m 2 / g, 100m 2 / g or a range consisting of any two of the above values.

[0088] For example, the specific surface area of ​​the second carbon nanotube can be 800 m². 2 / g、810m 2 / g、820m 2 / g、840m 2 / g、860m 2 / g、880m 2 / g、900m 2 / g、920m 2 / g、940m 2 / g、960m2 / g、980m 2 / g, 1000m 2 / g、1020m 2 / g、1040m 2 / g、1060m 2 / g、1080m 2 / g、1100m 2 / g、1120m 2 / g、1140m 2 / g、1160m 2 / g、1180m 2 / g、1200m 2 / g or a range consisting of any two of the above values.

[0089] [Positive electrode plate]

[0090] In some embodiments, the battery cell includes a positive electrode sheet, which includes a current collector and an active material film layer stacked together; the active material film layer includes a composite conductive agent, a binder, and active material particles; the composite conductive agent includes:

[0091] One-dimensional carbon materials, including first carbon nanotubes and second carbon nanotubes, wherein the specific surface area of ​​the first carbon nanotubes is ≤100 m². 2 / g optional 20m 2 / g~100m 2 / g; Specific surface area of ​​the second carbon nanotube ≥800m² 2 / g, 810m optional 2 / g~1200m 2 / g;

[0092] Two-dimensional carbon materials, including one or more of conductive graphite and graphene.

[0093] One-dimensional carbon materials, such as carbon nanotubes, exhibit good electrical conductivity and a specific surface area ≤100 m². 2 The high space utilization of the first carbon nanotubes ( / g) helps reduce the volume percentage of the composite conductive agent in the active material film, resulting in a specific surface area ≥800m². 2 The second carbon nanotube, with a surface area difference of ≥700m², can form a more conductive network, which is more conducive to long-range electron transport. 2The cross-combination of two types of carbon nanotubes per g can fully utilize the electrode space while achieving good conductivity. At the same time, the combination with two-dimensional carbon materials can increase the contact area of ​​carbon nanotubes. Meanwhile, the active material particles can be better surrounded and wrapped by the composite conductive agent. Electrons released or absorbed by the active material particles can be stably transported from more directions and over shorter distances. Thus, the conductivity of the electrode can be improved while reducing the amount of composite conductive agent used, and the space utilization rate is improved, thereby increasing the energy density of the battery.

[0094] For example, the specific surface area of ​​the first carbon nanotube can be 20 m². 2 / g、40m 2 / g、60m 2 / g、80m 2 / g, 100m 2 / g or a range consisting of any two of the above values.

[0095] For example, the specific surface area of ​​the second carbon nanotube can be 810 m². 2 / g、820m 2 / g、840m 2 / g、860m 2 / g、880m 2 / g、900m 2 / g、920m 2 / g、940m 2 / g、960m 2 / g、980m 2 / g, 1000m 2 / g、1020m 2 / g、1040m 2 / g、1060m 2 / g、1080m 2 / g、1100m 2 / g、1120m 2 / g、1140m 2 / g、1160m 2 / g、1180m 2 / g、1200m 2 / g or a range consisting of any two of the above values.

[0096] In the embodiments of this application, specific surface area has a meaning known in the art and can be detected using equipment and methods known in the art. For example, as a specific example, one-dimensional carbon material is dried in a vacuum drying oven at 200°C for 2 hours; then, nitrogen or argon is used as the adsorption gas, and adsorption-desorption curves with relative pressure P / P0 of 0 to 0.99 are plotted using a specific surface area and porosity analyzer, and its specific surface area is calculated using the BET method. When the test sample is a positive electrode sheet, a suitable solvent can be used to dissolve the positive electrode active material layer, ultrasonically disperse it, centrifuge to remove other particles, and then dry it to obtain the corresponding material to be tested.

[0097] In some embodiments, the mass content of the first carbon nanotube in the active material film layer is 0.2% to 0.5%.

[0098] Given the relatively small specific surface area of ​​the first carbon nanotubes, using first carbon nanotubes within the aforementioned mass content range can reduce the consumption of binder while still achieving a certain level of conductivity in the electrode. Simultaneously, the electrode exhibits good cohesion and adhesion. Furthermore, the lower cost of first carbon nanotubes can reduce formulation costs.

[0099] In some embodiments, the mass content of the second carbon nanotube in the active material film layer is 0.05% to 0.1%.

[0100] A very small amount of second carbon nanotubes with a large specific surface area can be combined with first carbon nanotubes with a small specific surface area within the aforementioned mass content range to form a carbon nanotube cross region with better conductivity. This can better cover the active material particles, improve conductivity and space utilization, and further enhance energy density.

[0101] When the mass content of the second carbon nanotube in the active material film is within the above-mentioned range, and it is combined with other conductive agents, a battery cell with good high-temperature storage performance, high-temperature capacity retention rate and long cycle retention rate can also be obtained.

[0102] For example, the mass content of the first carbon nanotube in the active material film layer can be 0.2%, 0.22%, 0.24%, 0.26%, 0.28%, 0.3%, 0.32%, 0.34%, 0.36%, 0.38%, 0.4%, 0.42%, 0.44%, 0.46%, 0.48%, 0.5%, or any range of two of the above values.

[0103] For example, the mass content of the second carbon nanotube in the active material film layer can be 0.05%, 0.051%, 0.053%, 0.055%, 0.057%, 0.059%, 0.061%, 0.063%, 0.065%, 0.067%, 0.069%, 0.071%, 0.073%, 0.075%, 0.077%, 0.079%, 0.081%, 0.083%, 0.085%, 0.087%, 0.089%, 0.091%, 0.093%, 0.095%, 0.097%, 0.099%, 0.1%, or any range of two of the above values.

[0104] In some embodiments, the mass content of the two-dimensional carbon material in the active material film layer is 0.3% to 0.5%.

[0105] Based on the selection of carbon nanotubes mentioned above, by combining them with two-dimensional carbon materials with a mass content of 0.3% to 0.5%, it is possible to form an anisotropic multidimensional conductive network using a small amount of composite conductive agent. This reduces the amount of composite conductive agent required while maintaining good conductivity.

[0106] Furthermore, based on this, the combination of the aforementioned two-dimensional carbon material with a mass fraction of 0.2% to 0.5% of first carbon nanotubes and a mass fraction of 0.05% to 0.1% of second carbon nanotubes can achieve high energy density, better storage performance at high temperatures, and low volume expansion rate.

[0107] For example, the mass content of two-dimensional carbon material in the active material film layer can be 0.3%, 0.32%, 0.34%, 0.36%, 0.38%, 0.4%, 0.42%, 0.44%, 0.46%, 0.48%, 0.5%, or any range of two of the above values.

[0108] In some embodiments, the composite conductive agent and binder have a surface coverage of 3% to 40% on the active material particles.

[0109] The conductive agent-binder domain, composed of a conductive agent and a binder, covers the surface of the active particles or fills the spaces between them. Appropriate coverage can reduce ion transport paths while ensuring electron transport, thereby improving electrical performance.

[0110] The surface coverage of the positive electrode active material particles can be tested using the following method: 1) At an environment of (25±3)℃, the electrode sheet coated with positive electrode active material particles is removed from the finished battery cell. The residual electrolyte on the surface of the electrode sheet is wiped off with lint-free paper; 2) The removed electrode sheet is observed using a scanning electron microscope (SEM) in backscatter mode, where the SEM voltage is set to 10.0kV, the working distance of the center of the field of view is kept at 10mm, and the magnification is set to 1000x; 3) Elemental analysis of the observed electrode sheet is performed using EDS, and the area ratio of carbon element in the image is calculated and recorded as the surface coverage of the positive electrode active material particles.

[0111] For example, the surface coverage of the composite conductive agent and binder on the active material particles can be 3%, 5%, 7%, 9%, 11%, 13%, 15%, 17%, 19%, 21%, 23%, 25%, 27%, 29%, 31%, 33%, 35%, 37%, 39%, or any combination of two of the above values.

[0112] In some implementations, during Raman spectroscopy testing of two-dimensional carbon materials, I d / I g The value is 0.5 to 0.9, I d This indicates that the Raman displacement is at 1300 cm. -1 ~1400cm -1 The d-peak intensity within the range, I g This indicates that the Raman shift is at 1530 cm. -1 ~1630cm -1 The intensity of the g peak within the range.

[0113] I of two-dimensional carbon materials d / I g Within the aforementioned range, suitable structural defects and graphitization levels, combined with the surface coverage of the active material particles, can further reduce the impedance of the electrode, giving it better conductivity and capacity retention.

[0114] The Raman spectrum of the composite conductive agent can be measured using a Raman spectrometer. During the test, the d-peak and g-peak intensities at 100 points are acquired, and the L / Ig ratio at these 100 points is calculated. The 30 largest and 30 smallest L / Ig values ​​are removed, and the average of the remaining 40 L / Ig values ​​is taken as the Ia / Ig ratio of the composite conductive agent. A Horiba LabRAM HR800 Raman spectrometer can be used. The test conditions are: excitation wavelength 532 nm, grating 600 lines, objective lens 50x, integration time 10 s, 3 iterations, and area scan.

[0115] For example, I d / I gIt can be 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, or a range of any two of the above values.

[0116] In some embodiments, the minimum length of the second carbon nanotube is ≥10μm, and the maximum diameter is 1nm to 3nm.

[0117] The second carbon nanotube, with its large specific surface area, thinner diameter, and longer length, can form a more continuous electron transport path. On the other hand, its higher surface energy allows it to connect and encapsulate more first carbon nanotubes, active material particles, and binders, thus playing an auxiliary bonding role and helping to reduce the amount of composite conductive agent and binder required.

[0118] For example, the minimum length of the second carbon nanotube can be 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, 22μm, 24μm, 26μm, 28μm, 30μm, 32μm, 34μm, 36μm, 38μm, 40μm, 42μm, 44μm, 46μm, 48μm, 50μm, 52μm, 54μm, 56μm, 58μm, 60μm, 62μm, 64μm, 66μm, 68μm, 70μm, or any range of two of the above values.

[0119] For example, the maximum diameter of the second carbon nanotube can be 1 nm, 1.2 nm, 1.4 nm, 1.6 nm, 1.8 nm, 2.0 nm, 2.2 nm, 2.4 nm, 2.6 nm, 2.8 nm, 3.0 nm, or any range of two of the above values.

[0120] In some embodiments, the maximum length of the first carbon nanotube is ≤20μm, optionally ≤10μm, and the minimum diameter is 30nm~150nm.

[0121] The first carbon nanotube, which has a larger diameter and shorter length, has better mechanical stability and thermal conductivity, which is conducive to heat dissipation and can improve the capacity retention rate of the battery at high temperatures. The short and thick first carbon nanotube also facilitates the penetration of electrolyte.

[0122] For example, the maximum length of the first carbon nanotube can be 2μm, 4μm, 6μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm or any range of two of the above values.

[0123] For example, the minimum diameter of the first carbon nanotube can be 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 110nm, 120nm, 130nm, 140nm, 150nm, or any range of two of the above values.

[0124] In the embodiments of this application, the length and diameter of carbon nanotubes have meanings known in the art and can be detected using equipment and methods known in the art.

[0125] For example, the maximum length and minimum diameter of the first carbon nanotube are dimensional parameters specific to a single first carbon nanotube material, referring to data obtained from measurements based on the same first carbon nanotube. For instance, the dimensions of the first carbon nanotube can be measured using scanning electron microscopy (SEM) images. Specifically, a portion of the positive electrode active material layer can be peeled off from the positive electrode sheet to expose its interior. Then, an SEM image of the surface of the positive electrode active material layer can be obtained. The SEM voltage is set to 10.0 kV, and at the same magnification (e.g., 100,000x, the specific magnification can be adjusted based on whether the carbon nanotubes can be clearly measured), the actual dimensions of the first carbon nanotube, including its length and diameter, can be measured in the SEM image. The maximum length can be the maximum length of the first carbon nanotube in the SEM image, and the minimum diameter is the minimum distance between the edge points of the inner wall of the first carbon nanotube in the SEM image.

[0126] For example, the minimum length and maximum diameter of the second carbon nanotube are dimensional parameters specific to a single second carbon nanotube material, referring to data obtained from measurements based on the same second carbon nanotube. For instance, the dimensions of the second carbon nanotube can be measured using scanning electron microscopy (SEM) images. Specifically, a portion of the positive electrode active material layer can be peeled off from the positive electrode sheet to expose its interior. Then, an SEM image of the surface of the positive electrode active material layer can be obtained. The SEM voltage is set to 10.0 kV, and the actual dimensions of the second carbon nanotube, including its length and diameter, are measured in the SEM image at the same magnification (e.g., 100,000x, the specific magnification can be adjusted based on whether the carbon nanotube can be clearly measured). The minimum length can be the minimum length of the second carbon nanotube in the SEM image, and the maximum diameter is the maximum distance between the edge points of the inner wall of the second carbon nanotube in the SEM image.

[0127] In some embodiments, the first carbon nanotube and the second carbon nanotube each independently include multi-walled carbon nanotubes, single-walled carbon nanotubes, or combinations thereof.

[0128] In some embodiments, the conductive graphite is flake graphite with a specific surface area of ​​10 m². 2 / g~30m2 / g, with an average flake diameter of 1μm to 10μm.

[0129] Under cold pressing of the electrode, two-dimensional flake graphite can promote the slippage of active particles, reduce the effect of particles on the substrate, and reduce the elongation of the electrode. The combination of flake graphite with the above-mentioned specific surface area and flake diameter range with one-dimensional carbon materials is more conducive to improving conductivity while reducing the elongation of the electrode.

[0130] For example, the specific surface area of ​​flake graphite can be 10 m². 2 / g、12m 2 / g、14m 2 / g, 16m 2 / g、18m 2 / g、20m 2 / g、22m 2 / g、24m 2 / g、26m 2 / g、28m 2 / g、30m 2 / g or a range consisting of any two of the above values.

[0131] For example, the average flake diameter of the flake graphite can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm or any range of two of the above values.

[0132] In some embodiments, the mass content of the composite conductive agent in the active material film layer is 0.55% to 1.1%.

[0133] For example, the mass content of the composite conductive agent in the active material film layer can be 0.55%, 0.57%, 0.59%, 0.61%, 0.63%, 0.65%, 0.67%, 0.69%, 0.71%, 0.73%, 0.75%, 0.77%, 0.79%, 0.81%, 0.83%, 0.85%, 0.87%, 0.89%, 0.91%, 0.93%, 0.95%, 0.97%, 0.99%, 1.01%, 1.03%, 1.05%, 1.07%, 1.09%, 1.1%, or any range of two of the above values.

[0134] The composite conductive agent formed by combining different carbon nanotubes and two-dimensional carbon materials has good conductivity and can reduce the mass content of the conductive agent in the active material film. For example, if the mass content of the composite conductive agent in the active material film can be controlled within the above range, the mass content of the active material particles can be increased, thereby increasing the energy density of the battery cell.

[0135] Furthermore, on the other hand, positive electrode sheets with the mass content of composite conductive agent in the active material film layer controlled within the above range can still have good electrode adhesion and cohesion, low elongation, and improved high-temperature storage performance and cycle performance of battery cells.

[0136] In some embodiments, the binder content in the active material film layer is 0.3% to 0.7% by mass.

[0137] Based on the composite conductive agent of the present application, the amount of binder can be reduced. The lower mass content of the binder can reduce the side reaction gas generation under high cutoff voltage and suppress the cell volume expansion.

[0138] For example, the mass content of the binder in the active material film layer can be 0.3%, 0.32%, 0.34%, 0.36%, 0.38%, 0.4%, 0.42%, 0.44%, 0.46%, 0.48%, 0.5%, 0.52%, 0.54%, 0.56%, 0.58%, 0.6%, 0.62%, 0.64%, 0.66%, 0.68%, 0.7%, or a range of any two of the above values.

[0139] In some embodiments, the mass content of active substance particles in the active substance film layer is 97.7% to 99.15%.

[0140] A higher mass content of positive electrode active material can improve the energy density of the battery.

[0141] For example, the mass content of active substance particles in the active substance film layer can be 97.7%, 97.72%, 97.74%, 97.76%, 97.78%, 97.8%, 97.82%, 97.84%, 97.86%, 97.88%, 97.9%, 97.92%, 97.94%, 97.96%, 97.98%, 98.0 ... 8.02%, 98.04%, 98.06%, 98.08%, 98.1%, 98.12%, 98.14%, 98.16%, 98.18%, 98.2%, 98.22%, 98.24%, 98.26%, 98.28%, 98.3%, 98.32%, 98.34%, 98.36%, 98.38%, 98.4%, 9 8.42%, 98.44%, 98.46%, 98.48%, 98.5%, 98.52%, 98.54%, 98.56%, 98.58%, 98.6%, 98.62%, 98.64%, 98.66%, 98.68%, 98.7%, 98.72%, 98.74%, 98.76%, 98.78%, 98.8%, 9 8.82%, 98.84%, 98.86%, 98.88%, 98.9%, 98.92%, 98.94%, 98.96%, 98.98%, 99.0%, 99.02%, 99.04%, 99.06%, 99.08%, 99.1%, 99.12%, 99.14%, 99.15%, or a range consisting of any two of the above values.

[0142] In some embodiments, the active material film layer also includes a dispersant, the mass content of which is 0.25% to 0.5%.

[0143] For example, the mass content of the dispersant in the active material film layer can be 0.25%, 0.30%, 0.35%, 0.40%, 0.45%, 0.50%, or any range of two of the above values.

[0144] In some embodiments, the dispersant includes one or more of acrylate-acrylonitrile copolymer, hydrogenated butyronitrile, and PVDF.

[0145] In some embodiments, the average particle size Dv50 of the active material particles is 3 μm to 5 μm, and the specific surface area is 0.5 m². 2 / g~1m 2 / g.

[0146] Small particle positive electrode active materials have low compaction density. The combination of the aforementioned small particle positive electrode active materials with small specific surface area and composite conductive agents can effectively improve the compaction density of the electrode formed by small particles, thereby obtaining higher energy density.

[0147] For example, the average particle size Dv50 of the active material particles can be 3 μm, 3.2 μm, 3.4 μm, 3.6 μm, 3.8 μm, 4.0 μm, 4.2 μm, 4.4 μm, 4.6 μm, 4.8 μm, 5.0 μm, or any range of two of the above values.

[0148] For example, the specific surface area of ​​the active material particles can be 0.5 m². 2 / g, 0.55m 2 / g, 0.6m 2 / g, 0.65m 2 / g, 0.7m 2 / g, 0.75m 2 / g, 0.8m 2 / g, 0.85m 2 / g, 0.9m 2 / g, 0.95m 2 / g、1m 2 / g or a range consisting of any two of the above values.

[0149] In some embodiments, the active material particles include a matrix material and a carbon material coated on at least a portion of the surface of the matrix material; the average particle size Dv50 of the active material particles is 4 μm to 15 μm, and the specific surface area is 5 m². 2 / g~20m 2 / g.

[0150] For example, the average particle size Dv50 of the active material particles can be 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm or any range of two of the above values.

[0151] For example, the specific surface area of ​​the active material particles can be 5m². 2 / g、6m 2 / g、7m 2 / g、8m 2 / g、9m 2 / g, 10m 2 / g、11m 2 / g、12m 2 / g、13m 2 / g、14m 2 / g, 15m 2 / g, 16m 2 / g、17m 2 / g、18m 2 / g、19m 2 / g、20m 2 / g or a range consisting of any two of the above values.

[0152] In some embodiments, the active material particles include one or more of lithium nickel cobalt manganese oxide materials, lithium nickel manganese oxide materials, lithium manganese oxide materials, lithium cobalt oxide materials, lithium-rich manganese-based materials, lithium iron phosphate materials, and lithium manganese iron phosphate materials.

[0153] In some embodiments, the binder has a weight-average molecular weight of 2,000,000 to 4,000,000 and a crystallinity of 15% to 55%.

[0154] Using the aforementioned binders with high weight-average molecular weight and suitable crystallinity can further reduce the amount of binder added to the active material film layer, thereby increasing energy density. The synergistic effect of the binders within the aforementioned weight-average molecular weight and crystallinity ranges, along with carbon nanotubes, can simultaneously reduce the amount of both added, further improving battery performance.

[0155] Furthermore, even with a low addition amount, the electrode exhibits good adhesion and cohesion, which helps maintain the structural stability of the electrode, improves the problem of poor interparticle contact caused by the expansion and contraction of the main material, and enhances cycle performance and storage performance.

[0156] For example, the weight-average molecular weight of the adhesive can be 2,000,000, 2,050,000, 2,100,000, 2,150,000, 2,200,000, 2,250,000, 2,300,000, 2,350,000, 2,400,000, 2,450,000, 2,500,000, 2,550,000, 2,600,000, 2,650,000, 2,700,000, 2,750,000, 2,800,000, 2,850,000, 2,900,000, 2,950,000, or 300. 0000, 3050000, 3100000, 3150000, 3200000, 3250000, 3300000, 3350000, 3400000, 3450000, 3500000, 3550000, 3600000, 3650000, 3700000, 3750000, 3800000, 3850000, 3900000, 3950000, 4000000, or a range consisting of any two of the above values.

[0157] For example, the crystallinity of the adhesive can be 15%, 17%, 19%, 21%, 23%, 25%, 27%, 29%, 31%, 33%, 35%, 37%, 39%, 41%, 43%, 45%, 47%, 49%, 51%, 53%, 55%, or a range of any two of the above values.

[0158] In some embodiments, the adhesive includes an adhesive with fluorinated functional groups, which includes one or more of PVDF, carboxylated polyvinylidene fluoride, polyhexafluoroethylene, polytetrafluoroethylene, and polyhexafluoropropylene-polyvinylidene fluoride copolymer.

[0159] In some embodiments, the compaction density of the positive electrode sheet is 3.0 g / cm³. 3 ~3.6g / cm 3 By selecting the aforementioned composite conductive agent and binder, positive electrode sheets within the aforementioned compaction density range can be obtained.

[0160] For example, the compaction density of the positive electrode sheet can be 3.0 g / cm³. 3 3.05g / cm 3 3.1g / cm 3 3.15g / cm 3 3.2g / cm 3 3.25g / cm 3 3.3g / cm 3 3.35g / cm 3 3.4g / cm 3 3.45g / cm 3 3.5g / cm 3 3.55g / cm 3 3.6g / cm 3 Or a range consisting of any two of the above values.

[0161] In some embodiments, the positive electrode sheet has a compaction density of 3.3 g / cm³. 3 The elongation is <0.7%, optionally ≤0.65%, and further optionally ≤0.6%. The positive electrode sheet has an elongation of 3.3 g / cm³. 3 The low elongation at the bottom can reduce deformation during rolling or cell manufacturing processes, resulting in better stability.

[0162] For example, the positive electrode sheet has a compaction density of 3.3 g / cm³. 3 The elongation rate can be 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.69%, or any range of two of the above values.

[0163] In some embodiments, the bonding strength of the positive electrode sheet is >15 N / m, optionally >21 N / m, and further optionally ≥25 N / m. Although the amount of binder used in this application is relatively small, the synergistic effect of the composite conductive agent and the binder in the embodiments of this application can enable the positive electrode sheet to still have good bonding strength, alleviate the shedding of active material particles in the active material film layer during charging and discharging, and improve the cycle performance of the battery.

[0164] For example, the bonding force of the positive electrode sheet can be 16 N / m, 17 N / m, 18 N / m, 19 N / m, 20 N / m, 21 N / m, 22 N / m, 23 N / m, 24 N / m, 25 N / m, 26 N / m, 27 N / m, 28 N / m, 29 N / m, 30 N / m or any range of two of the above values.

[0165] In some embodiments, the cohesive strength of the positive electrode sheet is >100 N / m, optionally >108 N / m, and further optionally ≥124 N / m. Similarly, in some embodiments of this application, the positive electrode sheet can improve the battery energy density while meeting the requirements for adhesion and cohesive strength of the electrode sheet by reducing the amount of composite conductive agent and further using a low amount of binder.

[0166] For example, the cohesive force of the positive electrode can be 101 N / m, 102 N / m, 104 N / m, 106 N / m, 108 N / m, 110 N / m, 112 N / m, 114 N / m, 116 N / m, 118 N / m, 120 N / m, 122 N / m, 124 N / m, 126 N / m, 128 N / m, 130 N / m, 132 N / m, 134 N / m, 136 N / m, 138 N / m, 140 N / m or any range of two of the above values.

[0167] In some embodiments, the current collector of the positive electrode can be a metal foil or a composite current collector. Examples of metal foils include stainless steel foil, carbon-coated aluminum foil, aluminum foil, nickel foil, and titanium foil. The composite current collector can include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. Examples of metal materials include, but are not limited to, one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Examples of polymer substrates include, but are not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene.

[0168] [Negative electrode plate]

[0169] In some embodiments, the battery cell further includes a negative electrode sheet, which includes a current collector and a negative electrode active material layer containing negative electrode active material stacked together.

[0170] In some embodiments, the negative electrode active material may include one or more of lithium, lithium alloy, graphite, mesophase micro carbon spheres, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and metal oxides.

[0171] Optionally, the mass fraction of lithium in the lithium alloy can be above 90%. Optionally, other elements in the lithium alloy can be one or more of In, Mg, Al, Zn, Sn, Ag, Au, Ga, Pt, and Fe. Optionally, the lithium alloy can be, but is not limited to, In-Li alloy, Li-Mg alloy, Li-Al alloy, Li-Zn alloy, and Li-Fe alloy. Optionally, the silicon-based material can be, but is not limited to, one or more of elemental silicon, silicon oxide, silicon-carbon composite material, silicon-nitrogen composite, and silicon alloy material. Optionally, the tin-based material can be, but is not limited to, one or more of elemental tin, tin oxide, and tin alloy material. Optionally, the metal oxide can be, but is not limited to, one or more of TiO2, MoO2, In2O3, Al2O3, Cu2O, VO2, Ga2O3, Sb2O5, and Bi2O5.

[0172] In some implementations, the current collector can be a metal foil, a three-dimensional porous current collector, or a composite current collector.

[0173] For example, the metal foil may be copper foil, copper alloy foil, nickel foil, nickel alloy foil, aluminum foil, or aluminum alloy foil. For example, the three-dimensional porous current collector may be copper mesh, nickel mesh, aluminum mesh, copper foam, nickel foam, or aluminum foam. For example, the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. For example, the metal material may include, but is not limited to, one or more of copper, copper alloys, aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer material base layer may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0174] In some embodiments, the negative electrode active material layer further includes a conductive agent, which may include, but is not limited to, one or more of conductive graphite (such as KS-6, SFG-6), superconducting carbon, acetylene black, conductive carbon black (such as SP), Ketjen black (such as ECP), carbon dots, carbon nanotubes, graphene, carbon nanofibers, and vapor-grown carbon fibers (VGCF).

[0175] In some embodiments, the negative electrode active material layer further includes a binder, which may include, but is not limited to, one or more of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, polyacrylic acid, polymethacrylic acid, sodium polyacrylate, polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), carboxymethyl chitosan (CMCS), sodium carboxymethyl cellulose, methyl vinyl silicone rubber, nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), thermoplastic styrene-butadiene rubber (SBS), isoprene rubber, styrene-butadiene rubber, cis-butadiene rubber (BR), ethyl cellulose, fluororubber, and acrylate rubber.

[0176] In some embodiments, the negative electrode active material layer comprises graphite, conductive carbon black, styrene-butadiene rubber, and sodium carboxymethyl cellulose in a weight ratio of (95.8–98):(0.4–1):(0.6–2.0):(1.0–1.2).

[0177] Electrolyte

[0178] In some embodiments, the battery cell also includes an electrolyte, which comprises an organic solvent and an electrolyte salt.

[0179] In some embodiments, the organic solvent may include, but is not limited to, one or more of esters, ethers, sulfones, nitriles, etc.

[0180] Esters may include, but are not limited to, one or more of carbonates, phosphate esters, carboxylic esters, sulfate esters, and sulfonates. Carbonates may include cyclic carbonates and / or chain carbonates; optionally, carbonates may include both cyclic and chain carbonates. Chain carbonates may include low-viscosity polar chain carbonates, aliphatic branched carbonates, etc.

[0181] For example, organic solvents may include, but are not limited to, ethylene carbonate (EC), propylene carbonate (PC), butene carbonate, ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), diethyl sulfone (ESE), dimethyl ether tetraethylene glycol (TEGDME), ethylene glycol dimethyl ether (... DME), 1,3-dioxolane (DOL), trimethyl phosphate, 3-methoxypropionitrile, 2-trifluoromethylhexafluoropropyl methyl ether, 2-trifluoromethylhexafluoropropyl ethyl ether, 2-trifluoromethylhexafluoropropyl propyl ether, 3-trifluoromethyloctafluorobutyl methyl ether, 3-trifluoromethyloctafluorobutyl ethyl ether, 3-trifluoromethyloctafluorobutyl propyl ether, 4-trifluoromethyldecafluoropentyl methyl ether, 4-trifluoromethyldecafluoropentyl ethyl ether, 4-trifluoromethyldecafluoropentyl propyl ether, 5-trifluoromethyldodecylfluorohexyl methyl ether, 5-trifluoromethyldodecylfluorohexyl ethyl ether, 5-trifluoromethyldodecylfluorohexyl propyl ether, 6-trifluoromethyltetradecylfluoroheptyl methyl ether, 6-trifluoromethyltetradecylfluoroheptyl ethyl ether, 6-trifluoromethyltetradecylfluoroheptyl propyl ether, 7-trifluoromethylhexadecylfluorooctyl methyl ether, 7-trifluoromethylhexadecylfluorooctyl ethyl ether, 7-trifluoromethylhexadecylfluorooctyl propyl ether.

[0182] In some embodiments, the organic solvent includes ethylene carbonate and ethyl methyl carbonate in a volume ratio of (2-5):(5-8).

[0183] For example, ethylene carbonate and methyl ethyl carbonate can be in a ratio of 2:8, 3:7, 4:6, 5:5, or any range of two of the above values.

[0184] In some embodiments, the electrolyte salt comprises anion and cation, and the anion may include bis(fluorosulfonyl)imide anion (FSI). - ), bis(trifluoromethanesulfonyl)imide anion (TFSI) - ), dioxaborate anion (BOB) - ), difluorooxalate borate anion (DFOB) - ), difluorodioxanol phosphate anion (DFOP) - ), tetrafluorooxalate phosphate anion (TFOP) - ), difluorophosphate anion (PO2F) 2- ), hexafluorophosphate anion (PF6) -), tetrafluoroborate anion (BF4) - ), hexafluoroarsenate anion (AsF6) - ), trifluoromethanesulfonate anion (CF3SO4) 3- One or more of the following.

[0185] In some embodiments, the cation may include one or more of lithium ions and sodium ions.

[0186] In some embodiments, the mass percentage of the electrolyte salt in the electrolyte can be 8% or more, for example, 10% or more, optionally 10% to 20%, and further optionally 12% to 15%. When the concentration of the electrolyte salt is within the above range, the electrolyte can have a suitable ionic conductivity.

[0187] [Isolation Component]

[0188] In some embodiments, the battery cell also includes a separator disposed between the positive electrode and the negative electrode.

[0189] In some embodiments, the separator includes a separator membrane. This application does not impose any particular limitation on the type of separator membrane; any known porous membrane with good chemical and mechanical stability can be selected.

[0190] In some embodiments, the material of the separator may include at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may 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 may be the same or different, without particular limitation. The separator may be a single component located between the positive and negative electrodes, or it may 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 may also be applied to the surface of the separator.

[0191] 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.

[0192] Battery

[0193] Secondly, embodiments of this application provide a battery including a housing and a battery cell according to any embodiment of the first aspect of this application, wherein the battery cell is housed within the housing.

[0194] Figure 2This is a schematic diagram illustrating the structure of a battery pack as an example. The battery pack may include a battery compartment and multiple battery modules housed within it. The battery compartment comprises an upper body and a lower body, with the upper body covering the lower body and forming a closed space for accommodating the battery modules. The multiple battery modules can be arranged in any manner within the battery compartment.

[0195] Electrical appliances

[0196] A third aspect of this application provides an electrical device, which includes at least one of the battery cell, battery module, or battery pack described in this application. The battery cell, battery module, or battery pack can be used as the power source for the electrical device or as the energy storage unit of the electrical device. The electrical device can be, 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.

[0197] Electrical devices can be equipped with individual battery cells, battery modules, or battery packs depending on their usage requirements.

[0198] Figure 3 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0199] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0200] Example

[0201] The following embodiments describe the contents disclosed in this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of the embodiments of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0202] Example 1

[0203] 1. Preparation of positive electrode sheet

[0204] The positive electrode consists of a positive current collector and an active material film. The positive current collector is aluminum foil, and the NCM positive electrode material (chemical formula LiNi) is used. 0.6 Co 0.2 Mn 0.2 O2, Dv50 is 3.2μm, specific surface area is 0.55m² 2 The following components were mixed uniformly in a certain proportion: NCM positive electrode material (g), sheet-like conductive graphite powder, first carbon nanotube powder, second carbon nanotube slurry (prepared by mixing deionized water and dispersant hydrogenated nitrile butyrate), and binder PVDF (weight average molecular weight 3,000,000, crystallinity 55%), with N-methylpyrrolidone (NMP) as solvent, to obtain a positive electrode slurry. The positive electrode slurry was then uniformly coated onto a positive electrode current collector, followed by drying, cold pressing, and slitting to obtain the positive electrode sheet. The mass contents of the NCM positive electrode material, composite conductive agent, and binder PVDF in the active material film layer were 98.54%, 0.86%, and 0.6%, respectively.

[0205] Before feeding, the maximum length of the first carbon nanotube is 10 μm, and the minimum length of the second carbon nanotube is 30 μm. The length of the carbon nanotube will change during the stirring of the slurry.

[0206] In this embodiment, the composite conductive agent in the positive electrode sheet includes: a first carbon nanotube with a specific surface area of ​​100 m². 2 / g, maximum tube length 6μm, minimum tube diameter 60nm, and mass content in the active material film layer is 0.4%;

[0207] The second carbon nanotube has a specific surface area of ​​800 m². 2 / g, minimum tube length 10μm, maximum tube diameter 2nm, and mass content in active material film layer is 0.06%;

[0208] Flake graphite, with a specific surface area of ​​20 m². 2 / g, with an average sheet diameter of 3.5μm, and a mass content of 0.4% in the active material film layer.

[0209] 2. Preparation of negative electrode sheet

[0210] The negative electrode sheet includes a negative current collector and a negative active material layer. The negative current collector is a copper foil. The active material artificial graphite, conductive carbon black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are dissolved in deionized water at a weight ratio of 97.2:0.8:0.8:1.2 and mixed evenly to prepare a negative electrode slurry. The negative electrode slurry is evenly coated on the negative current collector copper foil, and then dried, cold-pressed, and slit to obtain the negative electrode sheet.

[0211] 3. Separating membrane

[0212] A polyethylene film with a thickness of 13 μm was used as the separator.

[0213] 4. Preparation of electrolyte

[0214] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed uniformly at a volume ratio of 3:7. 12.5 wt% LiPF6 lithium salt was added and dissolved in the organic solvent and stirred until uniform to obtain the electrolyte.

[0215] 5. Battery manufacturing

[0216] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. They are then wound to obtain a bare cell. Tabs are welded onto the bare cell, which is then placed in an aluminum casing and baked at 80°C to remove moisture. Electrolyte is then injected and the casing is sealed, resulting in a non-charged battery. This non-charged battery then undergoes a series of processes including settling, hot and cold pressing, formation, shaping, and capacity testing to obtain a lithium-ion battery.

[0217] Comparative Example 1

[0218] Lithium-ion batteries were prepared using a method similar to that of Example 1, except that a conductive agent with a specific surface area of ​​60 m² was used. 2 The conductive carbon black has a weight-average molecular weight of 1,100,000, and the binder PVDF has a weight-average molecular weight of 1.10 million. The mass contents of the NCM cathode material (same as in Example 1), conductive agent, and binder PVDF in the active material film layer are 96.30%, 2.5%, and 1.2%, respectively.

[0219] Comparative Example 2

[0220] Lithium-ion batteries were prepared using a method similar to that of Example 1, except that the conductive agent did not contain second carbon nanotubes, but was replaced with an equal amount of first carbon nanotubes.

[0221] Comparative Example 3

[0222] Lithium-ion batteries were prepared using a method similar to that of Example 1, except that the conductive agent did not contain flake graphite, but was replaced with an equal amount of first carbon nanotubes.

[0223] Comparative Example 4

[0224] Lithium-ion batteries were prepared using a method similar to that of Example 1, except that the conductive agent did not contain flake graphite, but was replaced with an equal amount of carbon black.

[0225] Comparative Example 5: A lithium-ion battery was prepared using a method similar to that of Example 1. The difference from Example 1 was that the second carbon nanotube had a shorter tube length, with a maximum tube length of 20 μm during feeding, and a specific surface area of ​​500 m². 2 / g, the maximum length of the second carbon nanotube in the positive electrode is 10μm.

[0226] Examples 2-7

[0227] Example 2: A lithium-ion battery was prepared using a method similar to that of Example 1. The difference from Example 1 was that the amount of the first carbon nanotube was increased and the amount of the second carbon nanotube was decreased, while the mass content of the composite conductive agent in the positive electrode film remained unchanged.

[0228] Example 3: A lithium-ion battery was prepared using a method similar to that of Example 1. The difference from Example 2 was that the amount of the first carbon nanotube was further increased and the amount of the second carbon nanotube was reduced, while the mass content of the composite conductive agent in the positive electrode film remained unchanged.

[0229] Example 4: A lithium-ion battery was prepared using a method similar to that of Example 1. The difference from Example 1 was that the amount of the first carbon nanotube was reduced and the amount of the second carbon nanotube was increased, while the mass content of the composite conductive agent in the positive electrode film remained unchanged.

[0230] Example 5: A lithium-ion battery was prepared using a method similar to that of Example 1. The difference from Example 4 is that the amount of the first carbon nanotube was further reduced and the amount of the second carbon nanotube was increased, while the mass content of the composite conductive agent in the positive electrode film remained unchanged.

[0231] Example 6: A lithium-ion battery was prepared using a method similar to that of Example 1. The difference from Example 1 was that the amount of the first carbon nanotube was reduced, while the mass content of the composite conductive agent in the positive electrode film remained unchanged.

[0232] The parameters of some variations in the above embodiments and comparative examples are shown in Table 1.

[0233] Table 1

[0234]

[0235]

[0236] Performance testing

[0237] 1. Compacted density test

[0238] Take a single-sided coated and cold-pressed positive electrode sheet (if it is a double-sided coated positive electrode sheet, the positive electrode film on one side can be wiped off first), and cut it into small round pieces with an area of ​​S1 (e.g., 3mm*3mm). Weigh the pieces and record the weight as M1. Then wipe off the positive electrode film of the weighed positive electrode sheet, weigh the positive current collector, and record the weight as M0. The areal density of the positive electrode active material layer = (weight of the positive electrode sheet M1 - weight of the positive current collector M0) / S1. The compacted density of the positive electrode active material layer = areal density of the positive electrode active material layer / thickness of the positive electrode active material layer.

[0239] 2. At a compaction density of 3.3 g / cm³ 3 Electrode elongation test

[0240] Take the coated and dried positive electrode sheet that has not yet been cold-pressed, and cut it into samples with a length of 1000 mm. Adjust the roller press to cold-press the electrode sheet until the sample compaction density reaches the preset 3.3 g / cm³. 3 The length of the electrode after cold pressing was measured to be L, and the length difference before and after cold pressing was ΔL = L - 1000. Therefore, the compaction density is 3.3 g / cm³. 3 The electrode elongation is δ2 = (L - 1000 mm) / 1000 mm * 100%.

[0241] 3. Electrode adhesion test

[0242] Referring to the national standard "Test Method for 180° Peel Strength of Adhesives", the adhesion test process of the embodiments and comparative examples in this application is as follows: A sample with a width of 30mm and a length of 100-160mm is cut with a blade. Special double-sided adhesive tape is applied to the steel plate, with a tape width of 20mm and a length of 90-150mm. The previously cut electrode sample is then attached to the double-sided adhesive tape, with the test side facing down, and rolled three times in the same direction using a pressure roller. A paper strip with a width equal to the electrode and a length 80-200mm longer than the sample is inserted under the electrode and secured with wrinkle adhesive. The power of the Sansi tensile testing machine (sensitivity 1N) is turned on; the indicator light illuminates. The limit block is adjusted to a suitable position, and the end of the steel plate without the electrode attached is secured with the lower clamp. The paper strip is folded upwards and secured with the upper clamp. The position of the upper clamp is adjusted using the "up" and "down" buttons on the manual controller attached to the tensile testing machine. The test is then performed, and the values ​​are read. Three tests are conducted, and the average value is taken.

[0243] 4. Electrode cohesion test

[0244] The cohesive strength test process for the embodiments and comparative examples of this application is as follows: A sample with a width of 30mm and a length of 100-160mm is cut with a blade. Special double-sided adhesive tape is attached to the steel plate, with a tape width of 20mm and a length of 90-150mm. The previously cut electrode sample is attached to the double-sided adhesive tape. Half of the 20mm wide and 90-150mm long green adhesive tape is attached to the electrode surface, and then rolled three times in the same direction with a pressure roller. The remaining half of the green adhesive tape is then attached to the electrode. A paper strip with a width equal to the electrode and a length 80-200mm longer than the sample length is inserted below the electrode. The power of the Sansi tensile testing machine (sensitivity 1N) is turned on; the indicator light illuminates. The limit block is adjusted to a suitable position, and the end of the steel plate without the electrode attached is fixed with the lower clamp. The paper strip is folded upwards and fixed with the upper clamp. The position of the upper clamp is adjusted using the "up" and "down" buttons on the manual controller provided with the tensile testing machine. The test is then performed, and the values ​​are read. The test is performed three times, and the average value is taken.

[0245] 5. Electrode resistance test

[0246] Cut 3mm x 3mm small circles from the left, center, and right sides of the electrode. Turn on the indicator light of the Yuaneng Technology electrode resistance meter, place the probe at the appropriate position on the film resistance meter, and click the "Start" button. Once the reading stabilizes, take the reading. Test two positions for each small circle, and finally calculate the average of the six measurements, which is the film resistance of that electrode.

[0247] 6. Energy density test

[0248] At 25°C, within the voltage range of 2.5 to 4.5V, charge the battery at a 1C rate to 100% SOC and discharge it at a 1C rate to 0% SOC, recording the actual discharge energy at these times. At 25°C, accurately measure the cell volume as 790mL. The ratio of the actual discharge energy to the battery volume is the volumetric energy density.

[0249] 7. Cyclic performance test

[0250] Under constant temperature of 25℃, the voltage is charged at 0.33C to 4.5V at a range of 2.5 to 4.5V, and then charged at a constant voltage of 4.5V until the current is ≤0.05mA. After standing for 30 minutes, the voltage is discharged at 0.33C to 2.5V. The capacity is recorded as Dn (n=0,1,2……). The discharge capacity is recorded after 500cls. The capacity retention rate is (D500 / D1)*100%.

[0251] The performance test results are shown in Tables 2 and 3.

[0252] Table 2

[0253]

[0254] Table 3

[0255]

[0256] As can be seen from the data in Tables 1-3, the battery cells used in the embodiments of this application include those with a specific surface area ≤100m². 2 / g of first carbon nanotubes, specific surface area ≥800m² 2 The composite conductive agent, composed of / g of second carbon nanotubes and two-dimensional carbon materials, improves the energy density of the battery cell and enhances cycle performance while maintaining high energy density.

[0257] Including energy density, Comparative Example 1 used carbon black as the conductive agent, and its mass fraction of conductive agent was much higher than that of the Example. However, the resulting positive electrode sheet had lower adhesion and cohesion than the Example, and lower conductivity and cycle performance. Comparative Example 2 used a conductive agent that did not contain second carbon nanotubes, resulting in high electrode resistance, poor electrode cohesion, and lower cycle performance than the Example. Comparative Example 3 used a conductive agent that did not contain flake graphite, resulting in a large positive electrode sheet elongation, but cycle performance was also lower than the Example. Comparative Example 4 used a conductive agent that did not contain flake graphite, replacing the flake graphite with an equal amount of conductive carbon black particles. The resulting positive electrode sheet had low cohesion, high elongation, and lower cycle performance than the Example. In Comparative Example 5, the specific surface area of ​​the second carbon nanotubes in the composite conductive agent was <800 m². 2 / g, the synergistic effect with the first carbon nanotube and sheet graphite is not as good as in Example 1, and the performance of the resulting battery cell is not as good as in Example 1.

[0258] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. A battery cell, characterized in that, The positive electrode includes a positive electrode sheet, which comprises a current collector and an active material film layer stacked together; the active material film layer comprises a composite conductive agent, a binder, and active material particles; the composite conductive agent comprises: One-dimensional carbon material, comprising a first carbon nanotube and a second carbon nanotube, wherein the specific surface area of ​​the first carbon nanotube is ≤100 m². 2 / g, the specific surface area of ​​the second carbon nanotube is ≥800m² 2 / g; Two-dimensional carbon materials, including one or more of conductive graphite and graphene.

2. The battery cell according to claim 1, characterized in that, The composite conductive agent must satisfy at least one of the following characteristics: (1) The mass content of the first carbon nanotube in the active material film layer is 0.2% to 0.5%; (2) The mass content of the second carbon nanotube in the active material film layer is 0.05% to 0.1%; (3) The mass content of the two-dimensional carbon material in the active material film layer is 0.3% to 0.5%.

3. The battery cell according to claim 1, characterized in that, The composite conductive agent and the binder have a surface coverage of 3% to 40% on the active material particles.

4. The battery cell according to claim 1, characterized in that, In the Raman spectroscopy test of the two-dimensional carbon material, I d / I g The value is 0.5 to 0.9, I d This indicates that the Raman displacement is at 1300 cm. -1 ~1400cm -1 The d-peak intensity within the range, I g This indicates that the Raman shift is at 1530 cm. -1 ~1630cm -1 The intensity of the g peak within the range.

5. The battery cell according to claim 1, characterized in that, The one-dimensional carbon material must satisfy at least one of the following characteristics: (4) The minimum tube length of the second carbon nanotube is ≥10μm and the maximum tube diameter is 1nm~3nm; (5) The maximum length of the first carbon nanotube is ≤20μm and the minimum diameter is 30nm~150nm; (6) The first carbon nanotube and the second carbon nanotube each independently include multi-walled carbon nanotubes, single-walled carbon nanotubes or combinations thereof.

6. The battery cell according to claim 1, characterized in that, The conductive graphite is flake graphite, and the specific surface area of ​​the flake graphite is 10 m². 2 / g~30m 2 / g, with an average flake diameter of 1μm to 10μm.

7. The battery cell according to any one of claims 1 to 6, characterized in that, The active material film layer must satisfy at least one of the following characteristics: (7) The composite conductive agent has a mass content of 0.55% to 1.1% in the active material film layer; (8) The binder has a mass content of 0.3% to 0.7% in the active material film layer; (9) The mass content of the active substance particles in the active substance film layer is 97.7% to 99.15%.

8. The battery cell according to any one of claims 1 to 7, characterized in that, The active substance particles include at least one of the following: (10) The average particle size Dv50 of the active substance particles is 3μm to 5μm, and the specific surface area is 0.5m². 2 / g~1m 2 / g; (11) The active material particles comprise a matrix material and a carbon material coated on at least a portion of the surface of the matrix material; the average particle size Dv50 of the active material particles is 4 μm to 15 μm, and the specific surface area is 5 m². 2 / g~20m 2 / g.

9. The battery cell according to claim 8, characterized in that, The active material particles include one or more of the following: lithium nickel cobalt manganese oxide, lithium nickel manganese oxide, lithium manganese oxide, lithium cobalt oxide, lithium-rich manganese-based materials, lithium iron phosphate, and lithium manganese iron phosphate.

10. The battery cell according to any one of claims 1 to 9, characterized in that, The binder has a weight-average molecular weight of 2,000,000 to 4,000,000 and a crystallinity of 15% to 55%.

11. The battery cell according to any one of claims 1 to 10, characterized in that, The adhesive includes adhesives with fluorine-functional groups, which include one or more of PVDF, carboxylated polyvinylidene fluoride, polyhexafluoroethylene, polytetrafluoroethylene, and polyhexafluoropropylene-polyvinylidene fluoride copolymer.

12. The battery cell according to any one of claims 1 to 11, characterized in that, The positive electrode sheet must satisfy at least one of the following characteristics: (12) The compaction density of the positive electrode sheet is 3.0 g / cm³. 3 ~3.6g / cm 3 ; (13) The positive electrode sheet has a compaction density of 3.3 g / cm³. 3 The elongation is less than 0.7%; (14) The bonding force of the positive electrode sheet is >15 N / m; (15) The cohesive force of the positive electrode sheet is >100N / m.

13. A battery, characterized in that, It includes a housing and at least one battery cell as described in any one of claims 1 to 12, wherein the battery cell is housed within the housing.

14. An electrical appliance, characterized in that, The electrical device is configured to receive electrical energy supplied from the battery of claim 13.

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