Battery cell, battery device, and electric device

Abstract

The application discloses a battery monomer, a battery device and a power utilization device. The battery monomer comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode current collector and a composite positive electrode film layer located on at least one side of the positive electrode current collector, the composite positive electrode film layer comprises a first positive electrode film layer and a second positive electrode film layer, the first positive electrode film layer is located between the positive electrode current collector and the second positive electrode film layer, the first positive electrode film layer comprises a first positive electrode active material, and the second positive electrode film layer comprises a second positive electrode active material; the volume distribution particle size Dv 1 99 of the first positive electrode active material is less than the volume distribution particle size Dv 2 99 of the second positive electrode active material, and Dv 1 99≤10 μm. The battery monomer provided by the application has improved cycle performance.

Description

Technical Field

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

[0002] Batteries are widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, electric car toys, electric toy ships, electric toy airplanes, and power tools.

[0003] In the development of battery cells, improving the cycle life of battery cells is one of the urgent problems to be solved. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a battery cell, a battery device, and an electrical device.

[0005] In a first aspect, embodiments of this application provide a battery cell, the battery cell including a positive electrode sheet, the positive electrode sheet including a positive current collector and a composite positive electrode film layer located on at least one side of the positive current collector, the composite positive electrode film layer including a first positive electrode film layer and a second positive electrode film layer, the first positive electrode film layer being located between the positive current collector and the second positive electrode film layer, the first positive electrode film layer including a first positive electrode active material, and the second positive electrode film layer including a second positive electrode active material; the volume distribution particle size Dv of the first positive electrode active material is provided. 1 99 is less than the volume distribution particle size Dv of the second positive electrode active material. 2 99, and Dv 1 99≤10μm.

[0006] According to an embodiment of this application, the first positive electrode active material in the first positive electrode film layer has a smaller particle size and defines its volumetric particle size distribution Dv. 1 99 Within a specific range, according to this design, the first positive electrode film layer located on the surface of the negative electrode current collector contains positive electrode active material with smaller particle size. During compression, the small particles of positive electrode active material can distribute the pressure more evenly. Therefore, the first positive electrode film layer can act as a buffer layer to relieve pressure and reduce the squeezing damage of the large particles of positive electrode active material in the second positive electrode film layer to the current collector under high compaction, so that the positive electrode current collector maintains high mechanical strength, thereby improving the cycle performance of the battery cell while increasing the battery cell capacity.

[0007] In some embodiments, 5μm≤Dv 1 99≤7μm.

[0008] In some embodiments, 20μm≤Dv 2 99≤24μm.

[0009] In some embodiments, the particle size distribution (Dv) of the first positive electrode active material 1 90-Dv 1 10) / Dv 1 50 is 1.05-1.35, where Dv 1 10 represents the particle size corresponding to a cumulative volume distribution percentage of 10% for the first positive electrode active material, Dv. 1 50 represents the particle size corresponding to the cumulative volume distribution percentage of the first positive electrode active material reaching 50%, Dv 1 90 is the particle size corresponding to the cumulative volume distribution percentage of the first positive electrode active material reaching 90%.

[0010] In some embodiments, 2μm≤Dv 1 50≤4μm.

[0011] In some embodiments, the tap density of the first positive electrode active material is 1.5 g / cm³. 3 -2.3g / cm 3 .

[0012] In some embodiments, the thickness of the first positive electrode film is 10 μm-20 μm.

[0013] In some embodiments, the particle size distribution (Dv) of the second positive electrode active material 2 90-Dv 2 10) / Dv 2 50 is 2.2-2.8, where Dv 2 10 represents the particle size corresponding to a cumulative volume distribution percentage of 10% for the second positive electrode active material, Dv. 2 50 represents the particle size corresponding to the cumulative volume distribution percentage of the second positive electrode active material reaching 50%, Dv 2 90 is the particle size corresponding to the cumulative volume distribution percentage of the second positive electrode active material reaching 90%.

[0014] In some embodiments, 4μm≤Dv 2 50≤6μm.

[0015] In some embodiments, the tap density of the second positive electrode active material is 2.5 g / cm³. 3 -3g / cm 3 .

[0016] In some embodiments, the thickness of the second positive electrode film is 70 μm-110 μm.

[0017] In some embodiments, the first positive electrode film layer includes a first conductive agent.

[0018] In some embodiments, the second positive electrode film layer includes a second conductive agent.

[0019] In some embodiments, the first conductive agent comprises carbon nanotubes.

[0020] In some embodiments, the diameter of the carbon nanotubes is 50 nm to 100 nm.

[0021] In some embodiments, the length of the carbon nanotubes is 1 μm-15 μm.

[0022] In some embodiments, the carbon nanotubes account for 50%-80% of the total mass of the conductive agent.

[0023] In some embodiments, the mass content of the first conductive agent in the first positive electrode film is 0.7%-1.8% based on the total mass of the first positive electrode film.

[0024] In some embodiments, the mass content of the second conductive agent in the second positive electrode film is 0.6%-1.2% based on the total mass of the second positive electrode film.

[0025] In some embodiments, the first positive electrode film layer includes a first binder.

[0026] In some embodiments, the second positive electrode film layer includes a second binder.

[0027] In some embodiments, the mass content of the first binder in the first positive electrode film layer is 1.2%-1.8% based on the total mass of the first positive electrode film layer.

[0028] In some embodiments, the mass content of the second binder in the second positive electrode film layer is 0.5%-1.3% based on the total mass of the second positive electrode film layer.

[0029] In some embodiments, the compaction density of the composite positive electrode film is 3.6 g / cm³. 3 -3.75g / cm 3 .

[0030] In some embodiments, the porosity of the composite positive electrode film is 15%-20%.

[0031] In some embodiments, the first positive electrode active material comprises a first layered lithium-containing transition metal oxide having a single-particle morphology.

[0032] In some embodiments, the second positive electrode active material includes a second layered lithium-containing transition metal oxide having a single-particle morphology and a third layered lithium-containing transition metal oxide having a secondary-particle morphology.

[0033] In some embodiments, at least one of the first layered lithium-containing transition metal oxide, the second layered lithium-containing transition metal oxide, and the third layered lithium-containing transition metal oxide satisfies the following condition: it includes Ni element, and the molar percentage of Ni element in the transition metal elements of the layered lithium-containing transition metal oxide is greater than or equal to 80%.

[0034] In some embodiments, the first layered lithium-containing transition metal oxide, the second layered lithium-containing transition metal oxide, and the third layered lithium-containing transition metal oxide all satisfy the following condition: they include Ni element, and the molar percentage of Ni element in the transition metal elements of the layered lithium-containing transition metal oxide is greater than or equal to 80%.

[0035] Secondly, embodiments of this application provide a battery device, including a single battery cell from the first aspect of this application.

[0036] Thirdly, embodiments of this application provide an electrical device, including a battery cell from the first aspect of this application or a battery device from the second aspect of this application. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly described 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.

[0038] Figure 1 The diagram shows the structural features of a vehicle provided in some embodiments of this application.

[0039] Figure 2 This is an exploded schematic diagram of a battery provided for some embodiments of this application.

[0040] Figure 3 for Figure 2 The diagram shows an exploded view of the battery module.

[0041] Figure 4 This is a cross-sectional SEM image of the positive electrode sheet in Embodiment 1 of this application.

[0042] Figure 5 This is a cross-sectional SEM image of the positive electrode sheet in Comparative Example 1 of this application.

[0043] The accompanying drawings are not necessarily drawn to scale.

[0044] The reference numerals in the attached drawings are explained as follows: 1. Vehicle; 2. Battery unit; 3. Controller; 4. Motor; 5. Housing; 5a. First housing section; 5b. Second housing section; 5c. Reception space; 6. Battery module; 7. Battery cell. Detailed Implementation

[0045] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery cell, battery device, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0046] 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.

[0047] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0048] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0049] 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.

[0050] Unless otherwise specified, in this application, the terms "first," "second," etc., are used to distinguish different objects, rather than to describe a specific order or primary / secondary relationship.

[0051] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0052] In the description of the embodiments of this application, 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.

[0053] Unless otherwise stated, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0054] Unless otherwise stated, the values ​​of the parameters mentioned in this application can be determined using various testing methods commonly used in the art, for example, according to the testing methods given in the embodiments of this application. Unless otherwise stated, the test temperature for each parameter is 25°C.

[0055] The battery device mentioned in the embodiments of this application can be a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in this application can include battery cells, battery modules, or battery packs.

[0056] A single battery cell is the smallest unit that makes up a battery, and it can independently perform the functions of charging and discharging. When there are multiple battery cells, they are connected in series, parallel, or mixed connections through a busbar.

[0057] In some embodiments, the battery device may be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module.

[0058] In some embodiments, the battery device may be a battery pack, which includes a housing and individual battery cells, with the individual battery cells or battery modules housed within the housing.

[0059] 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.

[0060] In some embodiments, the battery device may be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0061] The technical solutions described in the embodiments of this application are applicable to battery devices and electrical devices that use battery devices.

[0062] Battery devices can be used as the power source for electrical devices or as energy storage units for electrical devices. Electrical devices can be, but are not limited to, mobile devices (such as mobile phones, tablets, laptops, etc.), vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0063] Electrical devices can choose the type of battery device according to their usage needs, such as individual battery cells, battery modules, or battery packs.

[0064] For ease of explanation, the following embodiments will use a vehicle as an example of an electrical device.

[0065] Figure 1 The diagram shows the structural features of a vehicle provided in some embodiments of this application.

[0066] like Figure 1 As shown, a battery device 2 is installed inside the vehicle 1. The battery device 2 can be located at the bottom, front, or rear of the vehicle 1. The battery device 2 can be used to power the vehicle 1; for example, the battery device 2 can serve as the operating power source for the vehicle 1.

[0067] The vehicle 1 may also include a controller 3 and a motor 4. The controller 3 is used to control the battery device 2 to supply power to the motor 4, for example, for the power needs of the vehicle 1 during starting, navigation and driving.

[0068] In some embodiments, the battery device 2 can not only serve as the operating power source for the vehicle 1, but also as the driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0069] Figure 2 This is a schematic diagram of a battery explosion provided for some embodiments of this application. For example... Figure 2 As shown, the battery device 2 includes a housing 5 and battery cells (not shown), with the battery cells housed within the housing 5.

[0070] The housing 5 is used to house individual battery cells, and the housing 5 can have various structures. In some embodiments, the housing 5 may include a first housing portion 5a and a second housing portion 5b, which overlap each other, and together define a housing space 5c for housing the individual battery cells. The second housing portion 5b may be a hollow structure with one end open, and the first housing portion 5a may be a plate-like structure, with the first housing portion 5a covering the open side of the second housing portion 5b to form a housing 5 with the housing space 5c; alternatively, both the first housing portion 5a and the second housing portion 5b may be hollow structures with one side open, with the open side of the first housing portion 5a covering the open side of the second housing portion 5b to form a housing 5 with the housing space 5c. Of course, the first housing portion 5a and the second housing portion 5b can have various shapes, such as cylinders, cuboids, etc.

[0071] To improve the sealing performance after the first housing part 5a and the second housing part 5b are connected, a sealing element, such as sealant or sealing ring, can also be provided between the first housing part 5a and the second housing part 5b.

[0072] Assuming that the first box section 5a covers the top of the second box section 5b, the first box section 5a can also be called the upper box cover, and the second box section 5b can also be called the lower box.

[0073] In battery device 2, there can be one or more battery cells. If there are multiple battery cells, they can be connected in series, in parallel, or in a mixed configuration. A mixed configuration means that multiple battery cells are connected in both series and parallel configurations. Multiple battery cells can be directly connected in series, in parallel, or in a mixed configuration, and then the whole assembly of multiple battery cells is housed in housing 5. Alternatively, multiple battery cells can first be connected in series, in parallel, or in a mixed configuration to form battery module 6, and then multiple battery modules 6 can be connected in series, in parallel, or in a mixed configuration to form a whole assembly, which is then housed in housing 5.

[0074] Figure 3 for Figure 2 The diagram shows an exploded view of the battery module.

[0075] like Figure 3 As shown, in some embodiments, there are multiple battery cells 7, which are first connected in series, parallel, or mixed to form a battery module 6. The multiple battery modules 6 are then connected in series, parallel, or mixed to form a whole and housed in a casing.

[0076] Multiple battery cells 7 in battery module 6 can be electrically connected through a busbar component to achieve parallel, series, or mixed connection of multiple battery cells 7 in battery module 6.

[0077] The battery cells mentioned in the embodiments of this application can be lithium-ion battery cells or sodium-ion battery cells.

[0078] The electrode assembly can be a wound structure or a stacked structure, and the embodiments of this application are not limited in this regard. The electrode assembly generally includes a positive electrode, a negative electrode, and a separator.

[0079] High capacity is one of the important directions for improving the performance of battery cells. There are two main strategies for improving the capacity of battery cells: one is to improve the specific capacity of the active material itself, and the other is to optimize the electrode structure and increase the proportion of active material in the electrode, such as increasing the compaction density of the active material and increasing the thickness of the active material layer.

[0080] Increasing compaction density is one of the effective means to improve the capacity of a single battery cell. However, high compaction density can also have a negative impact on the battery cell. In particular, under extreme compaction conditions, the positive electrode film layer needs to be subjected to high pressure. During the compaction process, large active material particles will squeeze the surface of the current collector, causing damage to the current collector. This leads to a decrease in the mechanical strength of the current collector and affects the cycle life of the battery cell.

[0081] In view of this, this application provides a battery cell that, by optimizing the structure of the positive electrode, can effectively reduce the damage to the current collector under high pressure and density conditions, thereby improving the cycle performance of the battery cell.

[0082] [Positive electrode plate]

[0083] The positive electrode includes a positive current collector and a composite positive electrode film layer located on at least one side of the positive current collector. The composite positive electrode film layer includes a first positive electrode film layer and a second positive electrode film layer, with the first positive electrode film layer located between the positive current collector and the second positive electrode film layer. The first positive electrode film layer includes a first positive electrode active material, and the second positive electrode film layer includes a second positive electrode active material. The volume distribution particle size Dv of the first positive electrode active material is... 1 99 is less than the volume distribution particle size Dv of the second positive electrode active material. 2 99, and Dv 1 99≤10μm.

[0084] The positive electrode sheet in this application uses a composite positive electrode film structure design. The first positive electrode active material in the first positive electrode film layer has a smaller particle size and its volume particle size distribution Dv is defined. 199 Within a specific range, according to this design, the first positive electrode film layer located on the surface of the negative electrode current collector contains positive electrode active material with smaller particle size. During compression, the small particles of positive electrode active material can distribute the pressure more evenly. Therefore, the first positive electrode film layer can act as a buffer layer to relieve pressure and reduce the squeezing damage of the large particles of positive electrode active material in the second positive electrode film layer to the current collector under high compaction, so that the positive electrode current collector maintains high mechanical strength, thereby improving the cycle performance of the battery cell while increasing the battery cell capacity.

[0085] In this embodiment, the volume distribution particle size Dv of the first positive electrode active material is... 1 99 ≤ 10 μm, for example, can be 10 μm, 9 μm, 8 μm, 7 μm, 6 μm, 5 μm, 4 μm, 3 μm, 2 μm, 1 μm, or any range of the above values, and can be selected as 5 μm-7 μm. This limits the volume distribution particle size Dv of the first positive electrode active material. 1 When the temperature is within the above range, the extrusion damage to the surface of the positive electrode current collector can be reduced, giving the positive electrode current collector higher mechanical strength; at the same time, the composite positive electrode film layer can have higher porosity, which is conducive to the rapid transport of active ions, giving the battery cell higher fast charging performance.

[0086] In some embodiments, the particle size distribution (Dv) of the first positive electrode active material 1 90-Dv 1 10) / Dv 1 50 is between 1.05 and 1.35, for example, it can be 1.05, 1.10, 1.15, 1.20, 1.25, 1.30, 1.35, or any range of the above values.

[0087] Particle size distribution refers to the size uniformity of the first positive electrode active material particles. Limiting the particle size distribution of the first positive electrode active material to the above range results in a more uniform particle size distribution and higher size uniformity. This allows the first positive electrode film layer to have suitable porosity under high pressure and density conditions, which is beneficial for improving the wetting of the positive electrode film layer by the electrolyte, increasing the ion transport rate, and improving the cycle performance and rate performance of the battery cell.

[0088] In some embodiments, the volume distribution particle size Dv of the first positive electrode active material 1 50 can be 2μm-4μm, for example, it can be 2.0μm, 2.2μm, 2.5μm, 2.8μm, 3.0μm, 2.5μm, 2.8μm, 4.0μm, or any range of the above values.

[0089] In some embodiments, the tap density of the first positive electrode active material can be 1.5 g / cm³. 3 -2.3g / cm3 For example, it can be 1.5g / cm³. 3 1.6g / cm 3 1.7g / cm 3 1.8g / cm 3 1.9g / cm 3 2.0g / cm 3 2.1g / cm 3 2.2g / cm 3 2.3g / cm 3 , or a range consisting of any of the above values.

[0090] Limiting the tap density of the first positive electrode active material to the above range is beneficial to improving the capacity and energy density of the battery cell.

[0091] In some embodiments, the thickness of the first positive electrode film can be 10μm-20μm, for example, it can be 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 8μm, 19μm, 20μm, or any range of the above values.

[0092] By limiting the thickness of the first positive electrode film layer to the above range, the first positive electrode film layer can provide a good buffering effect and reduce the squeezing damage of large particles on the positive electrode current collector. At the same time, the positive electrode film layer can have a suitable porosity and compaction density, which is beneficial to improving the energy density and cycle performance of the battery cell.

[0093] In some embodiments, the volume distribution particle size Dv of the second positive electrode active material 2 99 can be 20μm-24μm, for example, 20μm, 21μm, 22μm, 23μm, 24μm, or any combination of the above values. This defines the volume distribution particle size Dv of the second positive electrode active material. 2 Within the aforementioned range, the composite cathode film can achieve a high compaction density while maintaining a suitable porosity, enabling the battery cell to have a high capacity while also improving cycle performance.

[0094] In some embodiments, the particle size distribution (Dv) of the second positive electrode active material 2 90-Dv 2 10) / Dv 2 50 can be 2.2-2.8, for example, it can be 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, or any range of the above values.

[0095] The particle size distribution of the second positive electrode active material is limited to the above range. The particles of the second positive electrode active material have a wider particle size distribution, which makes the particles of different sizes in the second positive electrode active material have a better gradation. This can improve the compaction density of the second positive electrode film layer, which is beneficial to improving the energy density of the battery cell.

[0096] In some implementations, the volume distribution particle size Dv of the second positive electrode active material 2 50 can be 4μm-6μm, for example, it can be 4.0μm, 4.1μm, 4.2μm, 4.3μm, 4.4μm, 4.5μm, 4.6μm, 4.7μm, 4.8μm, 4.9μm, 5.0μm, 5.1μm, 5.2μm, 5.3μm, 5.4μm, 5.5μm, 5.6μm, 5.7μm, 5.8μm, 5.9μm, 6.0μm, or any range of the above values.

[0097] In some embodiments, the tap density of the second positive electrode active material can be 2.5 g / cm³. 3 -3g / cm 3 For example, it can be 2.5g / cm³. 3 2.6g / cm 3 2.7g / cm 3 2.8g / cm 3 2.9g / cm 3 3.0g / cm 3 , or a range consisting of any of the above values.

[0098] Limiting the tap density of the second positive electrode active material to the above range is beneficial to improving the capacity and energy density of the battery cell.

[0099] In some embodiments, the thickness of the second positive electrode film can be 70μm-110μm, for example, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm, 100μm, 105μm, 110μm, or any range of the above values.

[0100] In some embodiments, the composite positive electrode film may further include a conductive agent.

[0101] In some embodiments, the first positive electrode film layer may include a first conductive agent, and the second positive electrode film layer may include a second conductive agent. The first conductive agent and the second conductive agent may be the same or different, and may be the same.

[0102] As an example, the first conductive agent and the second conductive agent may each independently include one or more of superconducting carbon (Super P), acetylene black, carbon black, Ketjen black (KB), carbon dots, carbon nanotubes (CNT), graphene, and carbon nanofibers.

[0103] In some embodiments, the first conductive agent may include carbon nanotubes (CNTs). The small particle size and narrow particle size distribution of the first positive electrode active material in the first positive electrode film layer result in low porosity and a longer diffusion path for active ions. Carbon nanotubes have a high aspect ratio and good conductivity; adding carbon nanotubes to the first positive electrode film layer can improve its porosity, facilitating rapid ion transport, enhancing ion transport stability, and ultimately improving the cycle performance of the battery cell.

[0104] In some embodiments, the diameter of the carbon nanotubes can be 50nm-100nm, for example, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm, or any range of the above values.

[0105] In some embodiments, the length of the carbon nanotubes can be 1μm-15μm, for example, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, or any range of the above values.

[0106] In some embodiments, the mass percentage of carbon nanotubes can be 50%-80% based on the total mass of the first conductive agent, for example, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or any range of the above values.

[0107] In some implementations, based on the total mass of the first positive electrode film, the mass content of the first conductive agent in the first positive electrode film can be 0.7%-1.8%, for example, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, or any range of the above values. A content of the first conductive agent in the first positive electrode film within the above-mentioned units is beneficial for improving the conductivity of the composite positive electrode film, reducing internal resistance, and improving the electrochemical performance of the battery cell.

[0108] In some embodiments, based on the total mass of the second positive electrode film, the mass content of the second conductive agent in the second positive electrode film can be 0.6%-1.2%, for example, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, or any of the above-mentioned values. The content of the second conductive agent in the second positive electrode film within the above-mentioned units is beneficial for improving the conductivity of the composite positive electrode film, reducing internal resistance, and improving the electrochemical performance of the battery cell.

[0109] In some embodiments, the composite positive electrode film layer may further include a binder.

[0110] In some embodiments, the first positive electrode film layer may include a first adhesive, and the second positive electrode film layer may include a second adhesive. The first adhesive and the second adhesive may be the same or different, and may optionally be the same.

[0111] As an example, the first adhesive and the second adhesive may each independently include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0112] In some embodiments, based on the total mass of the first positive electrode film, the mass content of the first binder in the first positive electrode film can be 1.2%-1.8%, for example, it can be 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, or any range of the above values.

[0113] In some embodiments, based on the total mass of the second positive electrode film, the mass content of the second binder in the second positive electrode film can be 0.5%-1.3%, for example, it can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, or any range of the above values.

[0114] Since the first positive electrode active material in the first positive electrode film layer is composed of small particles, appropriately increasing the binder content in the first positive electrode film layer is beneficial to improving the bonding effect, reducing the shedding of the first positive electrode active material during positive electrode bending, cutting, and charge-discharge cycles, and improving the cycle stability of the battery cell.

[0115] In some embodiments, the compaction density of the composite positive electrode film is 3.6 g / cm³. 3 -3.75g / cm 3 For example, it can be 3.60 g / cm³. 3 3.62g / cm 3 3.65g / cm 3 3.68g / cm 3 3.70g / cm 3 3.72g / cm 3 3.75g / cm 3 , or a range consisting of any of the above values.

[0116] According to the embodiments of this application, by adjusting the structural design of the positive electrode sheet, the positive electrode sheet can have a high compaction density, thereby increasing the capacity and energy density of the battery cell, and the battery cell can also have high cycle performance.

[0117] In some embodiments, the porosity of the composite positive electrode film can be 15%-20%, for example, 15%, 16%, 17%, 18%, 19%, 20%, or any range of the above values.

[0118] When the porosity of the composite positive electrode film is within the above range, the positive electrode sheet has good electrolyte wettability, which is conducive to the rapid transport of active ions and can improve the cycle performance and rate performance of the battery cell.

[0119] In this application, the volume distribution particle size Dv of the first positive electrode active material is... 1 10. Dv 1 50. Dv 1 90. Dv 1 99 and the volume distribution particle size Dv of the second positive electrode active material 2 10. Dv 2 50. Dv 2 90. Dv 1 99 has a meaning known in the art, Dv 1 10 or Dv 2 10 refers to the particle size corresponding to when the cumulative volume distribution percentage of the first or second positive electrode active material reaches 10%, Dv 1 50 or Dv 2 50 refers to the particle size corresponding to when the cumulative volume distribution percentage of the first or second positive electrode active material reaches 50%, Dv 1 90 or Dv 2 90 refers to the particle size corresponding to when the cumulative volume distribution percentage of the first or second positive electrode active material reaches 90%, Dv 1 99 or Dv 2 99 refers to the particle size corresponding to a cumulative volume distribution percentage of 99% for either the first or second positive electrode active material. The volume distribution particle size can be determined using methods and instruments known in the art, such as laser diffraction particle size analysis, referring to standard GB / T19077-2016, using a laser particle size analyzer (e.g., Malvern Master Size 3000).

[0120] In this application, the tap density of the first positive electrode active material and the second positive electrode active material has a meaning known in the art, referring to the density measured after the powder has been tapped under specified conditions. Tap density can be determined using instruments and methods known in the art. For example, it can be determined using a powder tap density tester according to GB / T 5162-2006. The testing instrument can be the Dandong Baite BT-301, with the following testing parameters: vibration frequency 250±15 times / minute, amplitude 3±0.2mm, number of vibrations 5000 times, and a 25mL graduated cylinder.

[0121] In this application, the compaction density of the composite positive electrode film layer has a meaning known in the art, referring to the density of the powder material after compaction under a certain pressure, which can be measured using methods and instruments known in the art. For example, the compaction density can be calculated as follows: Compaction density of the composite positive electrode film layer = Areal density of the composite positive electrode film layer / Thickness of the composite positive electrode film layer. The areal density of the composite positive electrode film layer is the coating mass of the positive electrode active material per unit area. The thickness of the composite positive electrode film layer has a meaning known in the art and can be tested using methods known in the art, such as using a micrometer (e.g., Mitutoyo 293-100 type, with an accuracy of 0.1 μm).

[0122] In this application, the porosity of the composite positive electrode film has a well-known meaning in the art and can be tested using methods and equipment known in the art. For example, a positive electrode sheet coated on one side and cold-pressed (if it is a negative electrode sheet coated on both sides, the composite positive electrode film layer on one side can be wiped off first) is cut into small circular samples of a certain area, and the apparent volume V1 of the positive electrode sheet is calculated. Referring to GB / T24586-2009, an inert gas (such as helium or nitrogen) is used as the medium, and the gas replacement method is adopted to measure the true volume V2 of the positive electrode sheet using a true density meter. The porosity of the composite positive electrode film layer = (V1-V2) / V1×100%. Multiple positive electrode sheet samples (such as 30 sheets) with good appearance and no powder shedding at the edges can be tested, and the average value of the results is taken, which can improve the accuracy of the test results. The testing instrument can be a Micromeritics AccuPyc II 1340 true density meter.

[0123] In this application, the various parameter tests for the first positive electrode active material and the second positive electrode active material can be performed directly on the first positive electrode active material and the second positive electrode active material, or samples can be taken from the battery cell for testing.

[0124] When the test sample is obtained from a single battery cell, as an example, the sampling can be performed according to the following steps: Discharge the battery cell (generally to leave it fully discharged), remove the positive electrode after disassembling the battery cell, and soak the positive electrode in dimethyl carbonate (DMC) for a certain period of time (e.g., 2-10 hours); then remove the positive electrode and dry it at a certain temperature and time (e.g., 60°C, 4 hours), and remove the dried positive electrode; bake the dried positive electrode at a certain temperature and time (e.g., 400°C, 2 hours), select a region from the baked positive electrode, and sample the positive active material (sampling can be done by scraping powder with a blade); sieve the collected positive active material (e.g., sieve it through a 200-mesh sieve), and finally obtain a positive active material sample that can be used to test the material parameters described above in this application.

[0125] In some embodiments, the first positive electrode active material and the second positive electrode active material can both include layered lithium-containing transition metal oxides.

[0126] In some embodiments, the first positive electrode active material may include a first layered lithium-containing transition metal oxide having a single-particle morphology.

[0127] In some other embodiments, the second positive electrode active material may include a second layered lithium-containing transition metal oxide having a single-particle morphology and a third layered lithium-containing transition metal oxide having a secondary-particle morphology.

[0128] Examples of layered lithium-containing transition metal oxides may include one or more of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and their respective modified compounds.

[0129] In some embodiments, the layered lithium-containing transition metal oxide may include Ni. The molar amount of Ni may account for more than 80% of the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide; alternatively, the molar amount of Ni may account for more than 90% of the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide.

[0130] It is understood that the first layered lithium-containing transition metal oxide, the second layered lithium-containing transition metal oxide, and the third layered lithium-containing transition metal oxide can all meet the above-mentioned requirements for Ni element and content, or at least one of them can meet the above-mentioned requirements for Ni element and content, preferably all of them meet the above-mentioned requirements for Ni element and content.

[0131] The higher the Ni content in layered lithium-containing transition metal oxides, the higher the energy density of the battery cell.

[0132] In some embodiments, layered lithium-containing transition metal oxides may include Li a Ni b Co c M d O e A f Wherein, 0 < a ≤ 1.2; 0.8 ≤ b < 1; 0 < c < 1; 0 < d < 1; b + c + d = 1; 1 ≤ e ≤ 2; 0 ≤ f ≤ 1; M includes, but is not limited to, one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B; A includes, but is not limited to, one or more of N, F, S, and Cl. This can further improve the energy density of individual battery cells.

[0133] In some embodiments, as an example, layered lithium-containing transition metal oxides may include, but are not limited to, LiNi. 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiNi 0.9 Co 0.06 Mn 0.04 O2, LiNi 0.92 Co 0.06 Mn 0.02 O2, LiNi 0.96 Co 0.02 Mn 0.02 O2, LiNi 0.96 Co 0.02 Mn 0.02 O2N 0.02 One or more of them.

[0134] During the charging and discharging process of a battery cell, Li undergoes insertion / extraction and consumption, resulting in varying molar Li content at different discharge states. In the examples of positive electrode active materials in this application, the molar Li content refers to the initial state of the material, i.e., the state before feeding. After charge-discharge cycles, the molar Li content may change when the positive electrode active material is applied to the battery cell.

[0135] In some embodiments, the positive electrode active material may further include one or more of lithium phosphate, Prussian blue compounds, polyanionic compounds, and sodium transition metal oxides.

[0136] If the positive electrode active material is one or more of lithium phosphate and layered lithium transition metal oxide, then the positive electrode active material can be used in lithium-ion battery cells; if the positive electrode active material is one or more of Prussian blue compounds, polyanionic compounds, and sodium transition metal oxide, then the positive electrode material can be used in sodium-ion battery cells.

[0137] In some embodiments, as an example, sodium transition metal oxides may include, but are not limited to:

[0138] Na 1-x Cu h Fe k Mn l M 1 m O 2-y M 1 It is one or more of Li, Be, B, Mg, Al, K, Ca, Ti, Co, Ni, Zn, Ga, Sr, Y, Nb, Mo, In, Sn, and Ba, 0 <x≤0.33,0<h≤0.24,0≤k≤0.32,0<l≤0.68,0≤m<0.1,h+k+l+m=1,0≤y<0.2;

[0139] Na 0.67 Mn 0.7 Ni z M 2 0.3-z O2, where M 2 It is one or more of Li, Mg, Al, Ca, Ti, Fe, Cu, Zn and Ba, 0 <z≤0.1;

[0140] Na a Li b Ni c Mn d Fe e O2, of which 0.67 <a≤1,0<b<0.2,0<c<0.3,

[0141] 0.67 <d+e<0.8,b+c+d+e=1。

[0142] In some embodiments, as an example, the polyanionic compound may include, but is not limited to:

[0143] A 1 f M 3 g (PO4) i O j X 1 3-j Where A is one or more of H, Li, Na, K, and NH4, and M3 is one or more of Ti, Cr, Mn, Fe, Co, Ni, V, Cu, and Zn, X 1 is one or more of F, Cl, and Br, 0 < f ≤ 4, 0 < g ≤ 2, 1 ≤ i ≤ 3, 0 ≤ j ≤ 2;

[0144] Na n M 4 PO4X 2 , where M 4 is one or more of Mn, Fe, Co, Ni, Cu, and Zn, X 2 is one or more of F, Cl, and Br, 0 < n ≤ 2;

[0145] Na p M 5 q (SO4)3, where M 5 is one or more of Mn, Fe, Co, Ni, Cu, and Zn, 0 < p ≤ 2, 0 < q ≤ 2;

[0146] Na s Mn t Fe 3-t (PO4)2(P2O7), where 0 < s ≤ 4, 0 ≤ t ≤ 3, for example, t is 0, 1, 1.5, 2, or 3.

[0147] In some embodiments, by way of example, Prussian blue - type compounds may include, but are not limited to:

[0148] A u M 6 v [M 7 (CN)6] w ·xH2O, where A is H + , NH4 + , an alkali - metal cation, or an alkaline - earth metal cation, M 6 and M 7 are each independently one or more of transition - metal cations, 0 < u ≤ 2, 0 < v ≤ 1, 0 < w ≤ 1, 0 < x < 6. For example, A is H + , Li + , Na + , K + , NH4 + , Rb + , Cs + , Fr + , Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , and Ra2+ One or more of them, M 6 and M 7 Each is an independently selected cation of one or more transition metal elements chosen from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn, and W. Optionally, A is Li. + Na + and K + One or more of them, M 6 It is a cation of one or more transition metal elements selected from Mn, Fe, Co, Ni, and Cu, M 7 It is a cation of one or more transition metal elements selected from Mn, Fe, Co, Ni and Cu.

[0149] In the examples of positive electrode active materials in this application, the molar content of O is only a theoretical value. Oxygen release from the crystal lattice will cause the molar content of O to change, and the actual molar content of O will fluctuate.

[0150] The modified compounds for the above-mentioned positive electrode active materials can be obtained by doping and / or surface coating of the positive electrode active materials.

[0151] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be made by forming a metal material, such as aluminum, aluminum alloy, copper, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, on the polymer substrate. The polymer substrate may include polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), and other substrates.

[0152] In some embodiments, the thickness of the positive current collector is from 4 μm to 20 μm. It is optionally from 6 μm to 18 μm, and more preferably from 8 μm to 16 μm.

[0153] 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.

[0154] In this application, the thickness of each layer of the positive electrode sheet can be measured and analyzed using SEM (Scanning Electron Microscopy) of the cross-section of the positive electrode sheet, or it can be measured using a laser thickness gauge. This application allows for microscopic morphology observation of the cross-section of the positive electrode sheet, including the microscopic morphology of the positive current collector, the first positive electrode film layer, and the interfaces between different layers, thereby determining the thickness of each layer and the compression of the positive electrode film layer on the surface of the positive current collector. In this application, the cross-section of the positive electrode sheet refers to a cross-section formed by slicing along the thickness direction of the positive electrode sheet. Microscopic morphology observation of the cross-section of the positive electrode sheet can be combined with compositional analysis, such as energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis, to determine the elemental composition of each layer of the positive electrode sheet. In addition, focused electron beam (FIB) microscopes (such as the FEI Scios 2HiVa instrument) and ion section polishers (such as the JEOL IB-09010CP argon ion section polisher) can be used to polish the section to obtain a clear section.

[0155] [Negative electrode plate]

[0156] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer located on at least one side of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0157] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector. The negative electrode current collector can be made of materials such as metal foil, carbon-coated metal foil, or porous metal plate, and copper foil is an option.

[0158] As an example, the negative electrode active material may include one or more of the following: artificial graphite, natural graphite, mesophase micro carbon spheres, hard carbon, soft carbon, silicon, and silicon-carbon composites.

[0159] Silicon-based composite materials can be prepared by methods known in the art. For example, they can be prepared by vapor deposition using graphite and silicon materials as raw materials.

[0160] In some embodiments, the negative electrode film layer may further include a negative electrode conductive agent. As an example, the negative electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0161] In some embodiments, the negative electrode film layer may further include a negative electrode binder. As an example, the negative electrode binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0162] In some embodiments, the negative electrode film layer may also include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc.

[0163] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. Examples of metal foils include copper foil, copper alloy foil, aluminum foil, and aluminum alloy foil. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one side of the polymeric material substrate. Examples of metal materials include, but are not limited to, one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Examples of polymeric material substrates include, but are not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0164] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet may also include a conductive undercoat layer sandwiched between the negative electrode current collector and the negative electrode film layer and located on the surface of the negative electrode current collector, which may be composed of a conductive agent and a binder; in some embodiments, the negative electrode sheet may also include a protective layer covering the surface of the negative electrode film layer.

[0165] The negative electrode sheet can be prepared as follows: The negative electrode active material, negative electrode binder, negative electrode conductive agent, and optional other additives are dispersed in a solvent and stirred evenly to form a negative electrode slurry; the negative electrode slurry is coated onto a negative electrode current collector, and after drying, rolling, and other processes, a negative electrode sheet is formed. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0166] [Electrolytes]

[0167] A single battery cell includes an electrolyte.

[0168] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and an organic solvent.

[0169] In some embodiments, the electrolyte includes anion, which 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 (PO2F2) - ), hexafluorophosphate anion (PF6) - ), tetrafluoroborate anion (BF4) - ), hexafluoroarsenate anion (AsF6) - ), trifluoromethanesulfonate anion (CF3SO3) - One or more of the following.

[0170] In some embodiments, the electrolyte includes cations, which may include one or more of lithium ions and sodium ions.

[0171] In some embodiments, the concentration of the electrolyte salt may be 0.3 mol / L or higher, optionally 0.7 mol / L or higher, and further optionally 4 mol / L or lower, optionally 2.5 mol / L or lower, or 1.7 mol / L or lower. When the concentration of the electrolyte salt is within the above range, the electrolyte can have a suitable ionic conductivity.

[0172] Organic solvents may include, but are not limited to, one or more of esters, ethers, sulfones, and nitriles. 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.

[0173] As an 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, H(CF2)2OCH3, C4F9O CH3, H(CF2)2OCH2CH3, H(CF2)2OCH2CF3, H(CF2)2CH2O(CF2)2H, CF3CHFCF2OCH3, CF3CHFCF2OCH2CH3, 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-trifluoromethyl One or more of the following: decafluoropentyl methyl ether, 4-trifluoromethyl decafluoropentyl ethyl ether, 4-trifluoromethyl decafluoropentyl propyl ether, 5-trifluoromethyl dodecylfluorohexyl methyl ether, 5-trifluoromethyl dodecylfluorohexyl ethyl ether, 5-trifluoromethyl dodecylfluorohexyl propyl ether, 6-trifluoromethyl tetradecafluoroheptyl methyl ether, 6-trifluoromethyl tetradecafluoroheptyl ethyl ether, 6-trifluoromethyl tetradecafluoroheptyl propyl ether, 7-trifluoromethyl hexadecylfluorooctyl methyl ether, 7-trifluoromethyl hexadecylfluorooctyl ethyl ether, and 7-trifluoromethyl hexadecylfluorooctyl propyl ether.

[0174] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, additives that improve battery low-temperature power performance, etc.

[0175] [Isolation Component]

[0176] In some embodiments, the electrode assembly further includes a spacer disposed between the positive electrode and the negative electrode.

[0177] 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.

[0178] 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.

[0179] 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.

[0180] Example

[0181] The following embodiments describe the disclosure of 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 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.

[0182] Example 1

[0183] Positive electrode tab

[0184] The first positive electrode active material with a single-particle morphology, LiNi, is selected. 0.9 Co 0.05 Mn 0.05 O2, conductive agent Super P, conductive agent carbon nanotubes (80 nm in diameter and 10 μm in length), and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 97.2:0.6:0.9:1.3 in the solvent N-methylpyrrolidone (NMP). The mixture is stirred thoroughly at a speed of 600 r / s until homogeneous. Then, the mixture is wetted, kneaded, and dispersed to obtain the first positive electrode slurry. The viscosity of the first positive electrode slurry is adjusted to 12000 mPa·s. The first positive electrode slurry is then uniformly coated onto the surface of the positive electrode current collector aluminum foil and dried in an oven at 100°C, with the water content controlled to be less than 150 ppm, to form the first positive electrode film layer.

[0185] Take the second positive electrode active material LiNi 0.9 Co 0.05 Mn 0.05O2, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 98:1:1 in the solvent N-methylpyrrolidone (NMP). The second positive electrode active material comprises a second-layered lithium-containing transition metal oxide (LiNi) with a single-particle morphology. 0.9 Co 0.05 Mn 0.05 O2 and LiNi, a third-layer lithium-containing transition metal oxide with a secondary particle morphology 0.9 Co 0.05 Mn 0.05 The mass ratio of O2, the second layered lithium-containing transition metal oxide, and the third layered lithium-containing transition metal oxide is 3:7. The mixture is thoroughly stirred and homogenized at 600 r / s, then wetted, kneaded, and dispersed to obtain the second positive electrode slurry. The viscosity of the second positive electrode slurry is adjusted to 12000 mPa·s, and the slurry is uniformly coated onto the surface of the first positive electrode film. The film is then dried in an oven at 100°C, controlling the water content to be less than 150 ppm, to form the second positive electrode film. Finally, the film is cold-pressed and slit to obtain the positive electrode sheet.

[0186] The specific parameters of each part of the positive electrode are detailed in Table 1.

[0187] Negative electrode tab

[0188] A negative electrode slurry is prepared by uniformly mixing graphite (a negative electrode active material), conductive carbon black (a conductive agent), sodium carboxymethyl cellulose (CMC-Na) (a thickener), and styrene-butadiene rubber (SBR) (a binder) in deionized water at a mass ratio of 95:1:1:3. The negative electrode slurry is then uniformly coated onto copper foil (a negative electrode current collector), and the negative electrode sheet is obtained by cold pressing and slitting.

[0189] Separator film

[0190] A polyethylene (PE) film with a thickness of 12μm was selected.

[0191] Electrolyte

[0192] Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a mass ratio of 3:7, and then mixed with the electrolyte salt lithium hexafluorophosphate (LiPF6) to obtain an electrolyte solution with a LiPF6 concentration of 1 mol / L.

[0193] Battery cell

[0194] The positive electrode, negative electrode, and separator are stacked in sequence and injected with electrolyte to obtain a battery cell.

[0195] Example 2-23

[0196] The preparation method of the battery cell is similar to that in Example 1, except that the parameters of the positive electrode are different. For details of the parameter adjustments, please refer to Table 1.

[0197] Comparative Examples 1-2

[0198] The preparation method of the battery cell is similar to that in Example 1, except that the parameters of the positive electrode are different. For details of the parameter adjustments, please refer to Table 1.

[0199]

[0200]

[0201] Test section

[0202] 1. Elongation at break of the positive electrode sheet

[0203] The positive electrode sheet was cut into 50mm×15mm size and tested on a fully automatic tensile testing machine. The tensile rate was 2mm / min. The maximum displacement before the positive electrode sheet broke was recorded as L. The elongation at break (%) = (L-50) / 50×100%.

[0204] 2. Cyclic performance

[0205] At 25°C, the battery cells were charged to 4.25V at 0.5C and then discharged to 2.8V at 0.5C, and the discharge capacity C0 of the first cycle was recorded. The battery cells were then charged and discharged in the same manner, and the discharge capacity C of the battery cells was tested every 50 cycles. n The test is stopped when the discharge capacity of a single battery cell reaches 80% of the discharge capacity of the first cycle, and the number of cycles is recorded.

[0206] 3. Storage test

[0207] At 25℃, the battery cells were charged at 0.5C to 4.25V to reach 100% SOC, then discharged at 0.5C to 2.8V, and the initial discharge capacity C0 was recorded. Afterward, the cells were charged at 0.5C to 97% SOC and stored at 60℃ for 100 days. After removal from the furnace, the cells were allowed to stand at room temperature for at least 2 hours, then charged at 0.5C to 100% SOC, and then discharged at 0.5C to 2.8V, and the discharge capacity C of the battery cells was recorded. n The storage capacity retention rate after 100 days at 60℃ and 97% SOC is calculated using the following formula: Storage capacity retention rate (%) = C n / C0×100%.

[0208] The performance test results are detailed in Table 2.

[0209] Table 2

[0210]

[0211]

[0212] Combination Figure 4 and Figure 5 As can be seen from the cross-sectional SEM images of the positive electrode sheets in Example 1 and Comparative Example 1, the positive active material layer in this application example exerts a lower degree of compression on the positive current collector. Combined with the data in Table 1, the positive electrode sheet in Example 1 has a higher elongation at break, which indicates that the current collector in Example 1 has higher mechanical strength and better processing performance.

[0213] As can be seen from Examples 1-8 and Comparative Example 2, when the particle size of the first positive electrode active material in the first positive electrode film layer is too large, the elongation at break of the positive electrode sheet will decrease, and the cycle performance of the battery cell will also be affected.

[0214] As can be seen from Examples 1 and 9-12, by adjusting the SPAN value of the first positive electrode active material particles and the second positive electrode active material particles, the composite positive electrode film can have a suitable porosity and compaction density, which is beneficial to improving the cycle performance of the battery cell.

[0215] As can be seen from Examples 1 and 13-16, the conductivity of the composite positive electrode film can be adjusted by changing the content and type of conductive agent, thereby further improving the cycle performance of the battery cell.

[0216] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, characterized in that, The positive electrode includes a positive current collector and a composite positive electrode film layer located on at least one side of the positive current collector, the composite positive electrode film layer comprising: The first positive electrode film layer includes the first positive electrode active material; The second positive electrode film layer includes the second positive electrode active material; The first positive electrode film layer is located between the positive electrode current collector and the second positive electrode film layer, and the volume distribution particle size Dv of the first positive electrode active material is... 1 99 is less than the volume distribution particle size Dv of the second positive electrode active material. 2 99, and Dv 1 99≤10μm.

2. The battery cell according to claim 1, characterized in that, 5μm≤Dv 1 99≤7μm; and / or 20μm≤Dv 2 99≤24μm。 3. The battery cell according to claim 1 or 2, characterized in that, The particle size distribution (Dv) of the first positive electrode active material 1 90-Dv 1 10) / Dv 1 50 is 1.05-1.35, where Dv 1 10 represents the particle size corresponding to a cumulative volume distribution percentage of 10% for the first positive electrode active material, Dv. 1 50 represents the particle size corresponding to the cumulative volume distribution percentage of the first positive electrode active material reaching 50%, Dv 1 90 is the particle size corresponding to the cumulative volume distribution percentage of the first positive electrode active material reaching 90%.

4. The battery cell according to claim 3, characterized in that, 2μm≤Dv 1 50≤4μm。 5. The battery cell according to any one of claims 1-4, characterized in that, The tap density of the first positive electrode active material is 1.5 g / cm³. 3 -2.3g / cm 3 .

6. The battery cell according to any one of claims 1-5, characterized in that, The thickness of the first positive electrode film is 10μm-20μm.

7. The battery cell according to any one of claims 1-6, characterized in that, The particle size distribution (Dv) of the second positive electrode active material 2 90-Dv 2 10) / Dv 2 50 is 2.2-2.8, where Dv 2 10 represents the particle size corresponding to a cumulative volume distribution percentage of 10% for the second positive electrode active material, Dv. 2 50 represents the particle size corresponding to the cumulative volume distribution percentage of the second positive electrode active material reaching 50%, Dv 2 90 is the particle size corresponding to the cumulative volume distribution percentage of the second positive electrode active material reaching 90%.

8. The battery cell according to claim 7, characterized in that, 4μm≤Dv 2 50≤6μm。 9. The battery cell according to any one of claims 1-8, characterized in that, The tap density of the second positive electrode active material is 2.5 g / cm³. 3 -3g / cm 3 .

10. The battery cell according to any one of claims 1-9, characterized in that, The thickness of the second positive electrode film is 70μm-110μm.

11. The battery cell according to any one of claims 1-10, characterized in that, The first positive electrode film layer includes a first conductive agent, and / or The second positive electrode film layer includes a second conductive agent.

12. The battery cell according to claim 11, characterized in that, The first conductive agent includes carbon nanotubes.

13. The battery cell according to claim 12, characterized in that, The carbon nanotubes have a diameter of 50 nm to 100 nm; and / or The length of the carbon nanotubes is 1μm-15μm.

14. The battery cell according to claim 12 or 13, characterized in that, Based on the total mass of the conductive agent, the carbon nanotubes account for 50%-80% of the mass.

15. The battery cell according to any one of claims 11-14, characterized in that, Based on the total mass of the first positive electrode film, the mass content of the first conductive agent in the first positive electrode film is 0.7%-1.8%; and / or Based on the total mass of the second positive electrode film, the mass content of the second conductive agent in the second positive electrode film is 0.6%-1.2%.

16. The battery cell according to any one of claims 1-15, characterized in that, The first positive electrode film layer includes a first binder, and / or The second positive electrode film layer includes a second binder.

17. The battery cell according to claim 16, characterized in that, Based on the total mass of the first positive electrode film, the mass content of the first binder in the first positive electrode film is 1.2%-1.8%; and / or Based on the total mass of the second positive electrode film, the mass content of the second binder in the second positive electrode film is 0.5%-1.3%.

18. The battery cell according to any one of claims 1-17, characterized in that, The compaction density of the composite positive electrode film is 3.6 g / cm³. 3 -3.75g / cm 3 ; and / or The porosity of the composite positive electrode film is 15%-20%.

19. The battery cell according to any one of claims 1-18, characterized in that, The first positive electrode active material comprises a first layered lithium-containing transition metal oxide having a single-particle morphology; and / or The second positive electrode active material includes a second layered lithium-containing transition metal oxide with a single-particle morphology and a third layered lithium-containing transition metal oxide with a secondary-particle morphology.

20. The battery cell according to claim 19, characterized in that, At least one of the first layered lithium-containing transition metal oxide, the second layered lithium-containing transition metal oxide, and the third layered lithium-containing transition metal oxide satisfies the following condition: it includes Ni element, and the molar percentage of Ni element in the transition metal elements of the layered lithium-containing transition metal oxide is greater than or equal to 80%.

21. The battery cell according to claim 20, characterized in that, The first layered lithium-containing transition metal oxide, the second layered lithium-containing transition metal oxide, and the third layered lithium-containing transition metal oxide all satisfy the following condition: they include Ni element, and the molar percentage of Ni element in the transition metal elements of the layered lithium-containing transition metal oxide is greater than or equal to 80%.

22. A battery device, characterized in that, Includes the battery cell according to any one of claims 1 to 21.

23. An electrical appliance, characterized in that, Includes the battery cell according to any one of claims 1 to 21 or the battery device according to claim 22.

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