Battery cells, battery devices and power-consuming devices

Abstract

The present application discloses a battery cell, a battery device, and an electrical device. The battery cell includes a positive electrode plate, which includes a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector. The positive electrode film layer includes a positive electrode active material and a conductive agent, with part of the conductive agent located on the surface of the positive electrode active material. The positive electrode active material includes a core and a coating material coated on at least part of the surface of the core. The core includes a lithium-containing transition metal oxide, which includes nickel, with the molar proportion of nickel in the transition metal elements being greater than or equal to 50% and less than 100%. The coating material includes a metal element. The positive electrode active material includes primary particles having a particle size of 8 μm or less, with the number of primary particles having a particle size of 8 μm or less accounting for greater than or equal to 99%. The conductive agent includes carbon nanotubes, which include carbon nanotube aggregates, and the number of carbon nanotube aggregates within a range of 5 μm is less than or equal to 16.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery cell, a battery device, and an electrical device. Background Art

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

[0003] In the development process of battery cells, how to make battery cells have both high energy density and high dynamic performance is one of the problems that need to be solved urgently. Summary of the Invention

[0004] In response to the above technical problems, the present application provides a battery cell, a battery device and an electrical device.

[0005] In a first aspect, an embodiment of the present application provides a battery cell, comprising a positive electrode plate, the positive electrode plate comprising a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector, the positive electrode film layer comprising a positive electrode active material and a conductive agent, part of the conductive agent covering the surface of the positive electrode active material; the positive electrode active material comprising a core body and a coating material coated on at least a portion of the surface of the core body, the core body comprising a lithium-containing transition metal oxide, the lithium-containing transition metal oxide comprising a Ni element, based on the total molar amount of the transition metal elements in the lithium-containing transition metal oxide, the molar proportion of the Ni element is greater than or equal to 50% and less than 100%; the coating material comprises a metal element; the positive electrode active material comprises primary particles with a particle size of less than or equal to 8 μm, based on the total number of particles of the positive electrode active material, the number of the primary particles with a particle size of less than or equal to 8 μm accounts for greater than or equal to 99%; the conductive agent comprises carbon nanotubes, the carbon nanotubes comprise carbon nanotube agglomerates, and the positive electrode film layer has a particle size of 5 μm. The number of the carbon nanotube aggregates within a range of 5 μm is less than or equal to 16.

[0006] According to the embodiments of the present application, transition metal oxides with high Ni content have high capacity, which can enable battery cells to have higher energy density. By ensuring that the proportion of primary particles in the positive electrode active material is within the above range and limiting the primary particle size to 8 μm or less, the primary particles with this particle size are single crystals. Single crystal particles can provide the positive electrode active material with a higher compaction density, thereby shortening the diffusion distance of lithium ions in the positive electrode active material and increasing the lithium ion migration rate, thereby improving the dynamic performance of the battery cell. Furthermore, by coating the lithium-containing transition metal oxide with a coating material containing a metal element and partially covering the surface of the positive electrode active material with a conductive agent, the conductivity of the positive electrode active material can be improved. The contact points between the conductive agent and the positive electrode active material particles can be increased, forming a continuous conductive network. By limiting the number of carbon nanotube aggregates within the above range, the transmission rate of active ions can be further increased, the internal resistance can be reduced, and the lithium ion migration rate can be increased, thereby improving the dynamic performance of the battery cell.

[0007] The embodiments of the present application can compensate for the defect of decreased conductivity of the positive electrode active material due to increased Ni content and decreased Co content in high-nickel lithium-containing transition metal oxides by simultaneously controlling the particle size range of the positive electrode active material, the conductive agent, and the coating treatment of the positive electrode active material, so that the positive electrode active material can have both high capacity and high ion transfer rate, thereby making the battery cell strong, high energy density, and high dynamic performance.

[0008] In some embodiments, the primary particles include first particles with a particle size greater than or equal to 0.5 μm and less than or equal to 2 μm, and the first particles account for 85%-93% of the total number of primary particles. This can increase the lithium ion migration rate and improve the dynamic performance of the battery cell. At the same time, the positive electrode active material can have a higher compaction density, which is conducive to further improving the energy density of the battery cell.

[0009] In some embodiments, the primary particles further include secondary particles with a particle size of less than 0.5 μm and greater than or equal to 0.3 μm, with the secondary particles comprising 3%-6% of the total number of primary particles. This helps increase the compaction density of the positive electrode active material and the energy density of the battery cell; it also further shortens the diffusion distance of lithium ions and improves the dynamic performance of the battery cell.

[0010] In some embodiments, the primary particles further include third particles having a particle size of less than 0.3 μm, and the third particles account for less than or equal to 0.3% of the total number of primary particles. This helps reduce agglomeration of the positive electrode active material particles and reduces side reactions between the positive electrode active material and the electrolyte, enabling the battery cell to have high energy density and high kinetic performance while also improving cycle performance.

[0011] In some embodiments, the primary particles further include fourth particles having a particle size greater than 2 μm and less than or equal to 3 μm, and the fourth particles account for 2.5%-8% of the total number of primary particles. This facilitates ensuring that the positive electrode plate has a high compaction density while maintaining an appropriate porosity, improving the electrolyte wettability of the positive electrode plate, and enabling the battery cell to have high energy density and high dynamic performance while also improving cycle performance.

[0012] In some embodiments, the primary particles further include fifth particles having a particle size greater than 3 μm and less than or equal to 8 μm, with the fifth particles comprising less than or equal to 1.5% of the total number of primary particles. This allows the positive electrode active material to have a more concentrated particle size distribution, further shortening the lithium ion transmission path, increasing the lithium ion diffusion rate, and thereby improving the dynamic performance of the battery cell.

[0013] In some embodiments, the core may include a lithium-containing transition metal oxide having the following chemical formula: Li a Ni b Co c M d Q e O f , where M includes one or both of Mn and Al, and Q includes one or more of Mo, W, Sb, Nb, V, Zr, Sr, and Y; 0.8 ≤ a ≤ 1.1, 0.7 ≤ b < 1, 0.04 ≤ c < 1, 0.05 ≤ d < 1, 0.001 ≤ e ≤ 0.1, b + c + d + e = 1, and 1.8 ≤ f ≤ 2.2. This allows the positive electrode active material to achieve both high capacity and high conductivity, further improving the energy density and kinetic performance of the battery cell.

[0014] In some embodiments, 0.8≤b≤0.92, 0.04≤c≤0.12, 0.05≤d≤0.15, and 0.001≤e≤0.005. This allows the positive electrode active material to have both high capacity and high conductivity, thereby further improving the energy density and kinetic performance of the battery cell.

[0015] In some embodiments, the metal elements in the metal oxide include one or more of Al, Co, B, Ti, Nb, Sb, Sr, and Y. This can further improve the conductivity of the positive electrode active material, reduce the internal resistance of the battery cell, increase the ion transfer rate, and thus improve the dynamic performance of the battery cell.

[0016] In some embodiments, based on the total mass of the positive electrode active material, the mass percentage of the metal element in the positive electrode active material is 0.1%-0.9%, thereby further improving the dynamic performance of the battery.

[0017] In some embodiments, the coating material forms a coating layer on at least a portion of the surface of the core, and the coating layer has a thickness greater than 0 and less than or equal to 150 nm. Optionally, the coating layer has a thickness of 50 nm to 100 nm. This allows the positive electrode active material to have high capacity while also improving ionic conductivity, enabling the battery cell to achieve both high energy density and high kinetic performance.

[0018] In some embodiments, the volume distribution particle size Dv2 of the positive electrode active material is 0.5 μm-1.4 μm. Thus, the positive electrode film layer can have a suitable compaction density and porosity, which is beneficial to further improve the energy density and dynamic performance of the battery cell.

[0019] In some embodiments, the volume distribution particle size Dv50 of the positive electrode active material is 2 μm-3 μm. Thus, the positive electrode film layer can have a suitable compaction density and porosity, which is conducive to further improving the energy density and dynamic performance of the battery cell.

[0020] In some embodiments, the volume distribution particle size Dv90 of the positive electrode active material is 5 μm-6 μm. Thus, the positive electrode film layer can have a suitable compaction density and porosity, which is conducive to further improving the energy density and dynamic performance of the battery cell.

[0021] In some embodiments, the volume distribution particle size Dv99 of the positive electrode active material is 7 μm-10 μm. This allows the positive electrode film layer to have a suitable compaction density and porosity, which is beneficial for further improving the energy density and dynamic performance of the battery cell.

[0022] In some embodiments, the tap density of the positive electrode active material is 1.4 g / cm 3 -1.8g / cm 3 .

[0023] In some embodiments, at a pressure of 4T, the compaction density of the positive electrode active material is 3.3 g / cm 3 -3.6g / cm 3 .

[0024] In some embodiments, the specific surface area of ​​the positive electrode active material is 0.6 m 2 / g-1m 2 This helps to make the positive electrode film layer have a higher compaction density, thereby improving the energy density of the battery cell.

[0025] In some embodiments, the powder resistivity of the positive electrode active material at 12 MPa is less than or equal to 10,000 Ω·cm. This improves the conductivity of the positive electrode active material, thereby further reducing the internal resistance of the battery cell and improving the dynamic performance.

[0026] In some embodiments, the positive electrode active material includes a positive electrode active material having a surface covered with the conductive agent and a positive electrode active material not having a surface covered with the conductive agent. The mass percentage of the positive electrode active material having a surface covered with the conductive agent is 20%-50% based on the total mass of the positive electrode active material. This helps further improve the conductivity of the positive electrode active material, thereby improving the dynamic performance of the battery cell.

[0027] In some embodiments, the carbon nanotubes include carbon nanotube aggregates, and the positive electrode film has a thickness of 5 μm. The number of carbon nanotube agglomerates within a range of 5 μm is less than or equal to 16. This is beneficial for improving the ion diffusion and transmission rate of the positive electrode film layer and improving the cycle performance of the battery cell.

[0028] In some embodiments, the conductive agent in the positive electrode film has a mass percentage of 1% to 2% based on the total mass of the positive electrode film, thereby improving the conductivity of the positive electrode active material and, in turn, the dynamic performance of the battery cell.

[0029] In a second aspect, an embodiment of the present application provides a battery device, comprising the battery cell of the embodiment of the first aspect of the present application.

[0030] In a third aspect, an embodiment of the present application provides an electrical device, comprising a battery cell according to an embodiment of the first aspect of the present application or a battery device according to an embodiment of the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] To more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on the drawings without inventive effort.

[0032] Figure 1 Schematic diagram of a battery cell provided in some embodiments of the present application.

[0033] Figure 2 Schematic diagram of an electrical device provided in some embodiments of the present application.

[0034] Figure 3 This is a scanning electron microscope (SEM) image of the positive electrode film layer in one embodiment of the present application.

[0035] Figure 4 This is a SEM image of the positive electrode active material in one embodiment of the present application.

[0036] Figure 5 This is a statistical diagram of the particle size distribution of the positive electrode active material in one embodiment of the present application.

[0037] Figure 6 This is a SEM image of the positive electrode film layer in another embodiment of the present application.

[0038] In the accompanying drawings, the drawings are not necessarily drawn to scale. DETAILED DESCRIPTION

[0039] Below, the embodiments of the battery cells, battery devices, and electrical devices of the present application are described in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially the same structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0040] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0041] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0042] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of this application.

[0043] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which 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 may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0044] 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 a primary-secondary relationship.

[0045] In this application, the terms "plurality" and "multiple" refer to two or more.

[0046] In the description of the embodiments of the present application, unless otherwise specified, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, a first feature being "above," "above," and "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is at a higher level than the second feature. A first feature being "below," "below," and "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0047] Unless otherwise specified, the terms used in this application have the common meanings that are commonly understood by those skilled in the art.

[0048] Unless otherwise stated, the numerical values ​​of the various parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in the examples of this application. Unless otherwise stated, the test temperature of each parameter is 25°C.

[0049] The battery cells mentioned in the embodiments of this application can independently realize the functions of charging and discharging. The battery cells can be cylindrical, rectangular or other shapes, etc., and the embodiments of this application are not limited to this. Figure 1 As an example, a battery cell 5 having a rectangular parallelepiped structure is shown.

[0050] The battery apparatus mentioned in the embodiments of the present application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells, which are connected in series, parallel, or hybrid via a busbar.

[0051] In some embodiments, a battery cell assembly (Battery Cell Assembly) is generally formed by arranging a plurality of battery cells.

[0052] As an example, the battery cell assembly may be a battery module (Battery Module), which is formed by arranging and fixing multiple battery cells to form an independent module. As an example, the battery module may be formed by bundling multiple battery cells with a cable tie.

[0053] In some embodiments, the battery device may be a battery pack, which includes a case and one or more battery cell assemblies, wherein the battery cell assemblies are housed in the case.

[0054] As an example, the battery cell assembly may be a battery module, and the battery cell assembly may be accommodated in the box by fixing the battery module in the box.

[0055] As an example, the battery cell assembly may also be housed in the box by directly fixing the plurality of battery cells to the box.

[0056] As an example, the housing may include a first housing and a second housing. The first housing and the second housing engage to form an enclosed space within the housing to house the battery cell assembly. Enclosed here means covered or closed, and can be either sealed or unsealed. The first housing may be a top cover or a bottom plate.

[0057] As an example, the box may include a top cover, a frame, and a bottom plate, wherein the top cover and the bottom plate are respectively connected to the frame to form a closed space inside the box to accommodate the battery cell assembly.

[0058] In some embodiments, the box body can be used as a part of the chassis structure of the vehicle. For example, part of the box body can become at least a part of the floor of the vehicle, or part of the box body can become at least a part of the cross beam and longitudinal beam of the vehicle.

[0059] In some embodiments, the battery device may be an energy storage device, including an energy storage container, an energy storage cabinet, and the like.

[0060] The technical solutions described in the embodiments of the present application are applicable to battery devices and electrical devices using battery devices.

[0061] Battery devices can be used as power sources or energy storage units for electrical devices. These devices include, but are not limited to, mobile devices (e.g., mobile phones, tablets, laptops), vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks), electric trains, ships, satellites, and energy storage systems.

[0062] The electric device can select the type of battery device according to its usage requirements, such as a battery cell, a battery module, or a battery pack.

[0063] For the convenience of description, the following embodiments are described by taking a vehicle as an example of an electrical device.

[0064] Figure 2 1 is a schematic diagram of an exemplary electric device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.

[0065] The battery cells mentioned in the embodiments of the present application may be lithium-ion battery cells or sodium-ion battery cells.

[0066] A battery cell typically includes a shell and an electrode assembly within the shell. The electrode assembly generally includes a positive electrode sheet, a negative electrode sheet, and a separator. The separator is located between the positive electrode sheet and the negative electrode sheet, and serves to isolate the positive and negative electrodes and transmit active ions.

[0067] The electrode assembly can be a wound structure or a laminated structure, which is not limited in the present embodiment. The electrode assembly generally includes a positive electrode sheet, a negative electrode sheet, and a separator.

[0068] The positive electrode sheet includes a positive electrode film layer containing positive electrode active materials. For lithium-containing transition metal oxide positive electrode active materials, the energy density can be improved by increasing the proportion of Ni. As the proportion of Ni increases, the content of Co decreases accordingly, which also helps to reduce the cost of battery cells. However, the reduction in Co content will lead to poor conductivity of the positive electrode active material and slow ion diffusion rate, affecting the kinetic performance of the battery cell. Therefore, how to improve the energy density of battery cells without deteriorating the kinetic performance of battery cells is one of the current problems that need to be solved urgently.

[0069] In view of this, an embodiment of the present application provides a battery cell, which can achieve both high energy density and high dynamic performance by adjusting the parameter design of the positive electrode plate.

[0070] [Positive electrode]

[0071] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector, the positive electrode film layer includes a positive electrode active material and a conductive agent, and part of the conductive agent is covered on the surface of the positive electrode active material; the positive electrode active material includes a core body and a coating material coated on at least part of the surface of the core body, the core body includes a lithium-containing transition metal oxide, the lithium-containing transition metal oxide contains Ni element, based on the total molar amount of the transition metal elements in the lithium-containing transition metal oxide, the molar proportion of Ni element is greater than or equal to 50% and less than 100%; the coating material includes a metal element; the positive electrode active material includes primary particles with a particle size of less than or equal to 8μm, and based on the total number of particles of the positive electrode active material, the number of primary particles accounts for greater than or equal to 99%; the conductive agent includes carbon nanotubes, the carbon nanotubes include carbon nanotube agglomerates, and the positive electrode film layer has a particle size of 5μm. The number of carbon nanotube aggregates within 5 μm is less than or equal to 16.

[0072] In the embodiments of the present application, transition metal oxides with high Ni content have high capacity, which can enable the battery cell to have a higher energy density. By ensuring that the proportion of primary particles in the positive electrode active material is within the above range and limiting the primary particle size to 8 μm or less, the primary particles with this particle size are single crystals. Single crystal particles can give the positive electrode active material a higher compaction density, thereby shortening the diffusion distance of lithium ions in the positive electrode active material and increasing the migration rate of lithium ions, thereby improving the dynamic performance of the battery cell. Furthermore, by coating the lithium-containing transition metal oxide with a coating material containing a metal element and partially covering the surface of the positive electrode active material with a conductive agent, the conductivity of the positive electrode active material can be improved. The contact points between the conductive agent and the positive electrode active material particles can be increased, forming a continuous conductive network, reducing internal resistance, thereby further increasing the migration rate of lithium ions and, in turn, improving the dynamic performance of the battery cell.

[0073] Carbon nanotube aggregates are particles formed by the aggregation of individual carbon nanotubes. These aggregates can fill the voids in the positive electrode film, clogging the electrolyte pathway and impacting the transport and diffusion of active ions. By keeping the density of CNT aggregates in the positive electrode film within the above range and reducing the number of aggregates, it helps maintain a clear electrolyte pathway, enhance electrolyte wettability, and improve the cycling performance of the battery cells.

[0074] In the present application, the number of carbon nanotube aggregates in the positive electrode film layer can be measured using methods and instruments known in the art. For example, the positive electrode film layer can be tested using a scanning electron microscope (SEM), and the number of CNT aggregates can be visually counted through the obtained SEM images. Figure 3 As shown in the SEM image of the positive electrode film layer, CNT agglomerates are distributed in the gaps between the positive electrode active material particles and show obvious aggregation characteristics. By statistically analyzing the SEM image, the number of CNT agglomerates in a certain size area in the positive electrode film layer can be obtained.

[0075] The embodiments of the present application can compensate for the defect of decreased conductivity of the positive electrode active material due to increased Ni content and decreased Co content in high-nickel lithium-containing transition metal oxides by simultaneously controlling the particle size range of the positive electrode active material, the conductive agent, and the coating treatment of the positive electrode active material, so that the positive electrode active material can have both high capacity and high ion transfer rate, thereby making the battery cell strong, high energy density, and high dynamic performance.

[0076] In some embodiments, the primary particles include first particles having a particle size greater than or equal to 0.5 μm and less than or equal to 2 μm. Based on the total number of primary particles, the number of the first particles accounts for 85%-93%, for example, it can be 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, or a range consisting of any of the above values.

[0077] By ensuring that the proportion of first particles with a particle size greater than or equal to 0.5 μm and less than or equal to 2 μm in the primary particles is within the above range, the overall particle size of the primary particles is smaller and has a more concentrated particle size distribution, which is beneficial to further shorten the diffusion distance of lithium ions, increase the lithium ion migration rate, and improve the kinetic performance of the battery cell; at the same time, the positive electrode active material can have a higher compaction density, which is beneficial to further improve the energy density of the battery cell.

[0078] In some embodiments, the primary particles also include second particles having a particle size less than 0.5 μm and greater than or equal to 0.3 μm. Based on the total number of primary particles, the number of second particles accounts for 3%-5%, for example, it can be 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0%, or a range consisting of any of the above values.

[0079] By ensuring that the proportion of second particles with a particle size of less than 0.5 μm and greater than or equal to 0.3 μm in the primary particles is within the above range, a small amount of smaller particles are present in the positive electrode active material, and the second particles with smaller particle sizes can fill the gaps in the first particles, which is beneficial to improving the compaction density of the positive electrode active material and the energy density of the battery cell; at the same time, it can further shorten the diffusion distance of lithium ions and improve the kinetic performance of the battery cell.

[0080] In some embodiments, the primary particles further include third particles having a particle size less than 0.3 μm. Based on the total number of primary particles, the number of the second particles accounts for less than or equal to 0.3%, for example, 0.3%, 0.2%, 0.1%, or any of the above values.

[0081] By ensuring that the proportion of third particles with a particle size of less than 0.3 μm in the primary particles is within the above range, the content of extremely small particles in the positive electrode active material can be reduced, which is beneficial to reducing the agglomeration of the positive electrode active material particles. At the same time, the side reactions between the positive electrode active material and the electrolyte can be reduced, so that the battery cell has high energy density and high kinetic performance while taking into account improved cycle performance.

[0082] In some embodiments, the primary particles also include fourth particles having a particle size greater than 2 μm and less than or equal to 3 μm. Based on the total number of primary particles, the number of fourth particles accounts for 5%-8%, for example, it can be 5.0%, 5.2%, 5.5%, 5.8%, 6.0%, 6.2%, 6.5%, 6.8%, 7.0%, 7.2%, 7.5%, 7.8%, 8.0%, or a range consisting of any of the above values.

[0083] By ensuring that the fourth particles in the primary particles with a particle size greater than 2 μm and less than or equal to 3 μm are within the above-mentioned range, a small amount of larger particles are present in the positive electrode active material. The fourth particles with a larger particle size can enable the positive electrode active material to have a certain porosity after compaction, which is beneficial for the positive electrode plate to have a suitable porosity while having a high compaction density, improve the electrolyte wettability of the positive electrode plate, and enable the battery cell to have high energy density and high dynamic performance while taking into account improved cycle performance.

[0084] In some embodiments, the primary particles also include fifth particles having a particle size greater than 3 μm and less than or equal to 8 μm. Based on the total number of primary particles, the number of fifth particles accounts for less than or equal to 1.5%, for example, it can be 1.5%, 1.4%, 1.3%, 1.2%, 1.1%, 1.0%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, or a range consisting of any of the above values.

[0085] By ensuring that the proportion of fifth particles having a particle size greater than 3 μm and less than or equal to 8 μm in the primary particles is within the above range, the content of large particles in the positive electrode active material can be reduced, and the positive electrode active material can have a more concentrated particle size distribution, which is beneficial to further shorten the transmission path of lithium ions, increase the lithium ion diffusion rate, and thereby improve the kinetic performance of the battery cell.

[0086] According to the embodiments of the present application, by controlling the distribution of particles of different particle size intervals in the primary particles within the above range, the positive electrode active material can have a concentrated particle size distribution to shorten the lithium ion transmission path. At the same time, the positive electrode active material can have a high compaction density and a suitable porosity, thereby enabling the battery cell to have high energy density and high kinetic performance while also taking into account improved cycle performance. It is understood that the particle size distribution of the primary particles can be adjusted by controlling the sintering time, sintering temperature, pulverization parameters, screening parameters, etc. during the preparation process of the positive electrode active material.

[0087] In the present application, the particle size of the positive electrode active material particles refers to the measured average particle size of the positive electrode active material particles, which can be tested by the following method: the battery cell is fully discharged, the battery cell is disassembled to obtain the positive electrode plate, the positive electrode film powder is scraped from the positive electrode plate, and the obtained powder is heat-treated (such as 600°C, 120min) to remove the conductive agent to obtain the positive electrode active material particles, and the positive electrode active material particles are tested using a scanning electron microscope to obtain the microscopic morphology of the positive electrode active material. Figure 4 The SEM images of the positive electrode active materials in some embodiments of the present application are shown. It can be seen that the positive electrode active materials present a single particle morphology. By performing statistical analysis on the SEM images of the positive electrode active materials, the particle size distribution of the primary particles in the positive electrode materials can be obtained. Figure 5 The particle size distribution and cumulative curve of the positive electrode active secondary material in one embodiment of the present application are shown. It can be seen that the particle size distribution of the positive electrode material is mainly concentrated in the first particle size of 0.5μm to 2μm, and the particle size of the positive electrode material is relatively small. The particle size distribution diagram can be used to obtain the respective proportions of the second particle size less than 0.5μm and greater than or equal to 0.3μm, the third particle size less than 0.3μm, the fourth particle size greater than 2μm and less than or equal to 3μm, and the fifth particle size greater than 3μm and less than or equal to 8μm in the positive electrode active material.

[0088] In some embodiments, the core comprises a lithium-containing transition metal oxide having the following chemical formula: Li a Ni b Co c M d Q e O f , M includes one or two of Mn and Al, Q includes one or more of Mo, W, Sb, Nb, V, Zr, Sr, and Y; 0.8≤a≤1.1, 0.7≤b<1, 0.04≤c<1, 0.05≤d<1, b+c+d=1, 0.001≤e≤0.01, 1.8≤f≤2.2. By further limiting the chemical composition of the core body within the above range, it is beneficial to further improve the capacity of the positive electrode active material, thereby improving the energy density of the battery cell. In addition, by doping the lithium-containing transition metal oxide with doping elements, it is beneficial to improve the conductivity of the lithium-containing transition metal oxide, thereby improving the conductive properties of the positive electrode active material, reducing the internal resistance, and thus improving the kinetic performance of the battery cell.

[0089] In some embodiments, 0.8≤b≤0.92, 0.04≤c≤0.12, 0.05≤d≤0.15, 0.001≤e≤0.005. Alternatively, 0.8≤b≤0.88, 0.04≤c≤0.09, 0.09≤d≤0.12, 0.002≤e≤0.005.

[0090] According to the embodiments of the present application, by limiting the proportion of each element in the above-mentioned core body to the above-mentioned range, the positive electrode active material can have both high capacity and high conductivity, which is conducive to further improving the energy density and kinetic performance of the battery cell.

[0091] In some embodiments, the metal elements in the cladding material may include one or more of Al, Co, B, Ti, Nb, Sb, Sr, and Y. The cladding material may include one or more oxides formed from the above metal elements.

[0092] According to the embodiments of the present application, the oxides of the above-mentioned metal elements have high ionic conductivity. Using them as the coating material of the core of the positive electrode active material can further improve the conductivity of the positive electrode active material, reduce the internal resistance of the battery cell, increase the ion transfer rate, and thus improve the dynamic performance of the battery cell.

[0093] In some embodiments, the mass percentage of the metal element in the positive electrode active material may be 0.1%-0.9% based on the total mass of the positive electrode active material. As an example, the mass percentage of the metal element in the positive electrode active material may be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or a range consisting of any of the above values. Alternatively, the mass percentage of the metal element in the positive electrode active material may be 0.3%-0.8% based on the total mass of the positive electrode active material.

[0094] According to the embodiments of the present application, by limiting the content of the metal elements in the coating layer in the positive electrode active material to the above range, it is beneficial to further improve the dynamic performance of the battery. When the content of the metal elements is low, the ionic conductivity of the positive electrode active material is low, the internal resistance of the battery cell increases, and it is not conducive to improving the dynamic performance of the battery cell. When the content of the metal elements is high, the ionic conductivity of the positive electrode active material can be further improved, but the content of the active material that can contribute to the capacity decreases, resulting in a decrease in the energy density of the battery cell.

[0095] In some embodiments, the coating material forms a coating layer on at least a portion of the surface of the core body, and the coating layer has a thickness greater than 0 and less than or equal to 150 nm. As an example, the coating layer can have a thickness of 150 nm, 140 nm, 130 nm, 120 nm, 110 nm, 100 nm, 90 nm, 80 nm, 70 nm, 60 nm, 50 nm, 40 nm, 30 nm, 20 nm, 10 nm, 5 nm, 1 nm, or a range consisting of any of the above values. Alternatively, the coating layer can have a thickness of 50 nm to 100 nm.

[0096] According to the embodiments of the present application, the coating layer thickness within the above range can improve the ionic conductivity of the positive electrode active material while maintaining a high capacity, allowing the battery cell to achieve both high energy density and high kinetic performance. When the coating layer thickness is thin, the content of the metal element that can improve ionic conductivity is low, and the ionic conductivity of the positive electrode active material is low, which is not conducive to improving the kinetic performance of the battery cell. When the coating layer thickness is thick, the proportion of active material decreases, resulting in a decrease in the energy density of the battery cell.

[0097] In the present application, the thickness of the coating layer can be measured by methods and instruments known in the art. For example, a transmission electron microscope (TEM) image of the positive electrode active material in the positive electrode film layer can be obtained. The TEM image can reveal the structure of the coating layer on the surface of the positive electrode active material particles, and the thickness of the coating layer can be measured. The elemental composition and positional distribution of each element in the coating layer can be measured by methods and instruments known in the art. For example, the positive electrode active material can be treated with an ion beam cutter (CP), and then the positive electrode active material after ion beam cutting can be tested using TOF-SIMS (time-of-flight secondary ion mass spectrometry) to determine the element position and distribution.

[0098] In this application, the elemental composition of the positive electrode active material can be determined by methods known in the art. For example, the following method can be used: 0.2 g of positive electrode active material powder is placed in a 100 mL beaker, 10 mL of 10% w / w nitric acid solution is added, and the mixture is heated and digested at 120°C for 0.5 hours. The solution is then brought to volume in a 100 mL volumetric flask. 1 mL of the solution is then pipetted into a 100 mL volumetric flask and brought to volume to obtain a test solution. The mass fraction of each element in the test solution is determined using an inductively coupled plasma optical emission spectrometer (ICP-OES, instrument brand: Agilent 5800).

[0099] In some embodiments, the volume distribution particle size Dv2 of the positive electrode active material may be 0.5 μm-1.4 μm. As an example, the volume distribution particle size Dv2 of the positive electrode active material may be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, or a range consisting of any of the above values. Alternatively, the volume distribution particle size Dv2 of the positive electrode active material may be 0.9 μm-1.2 μm.

[0100] In some embodiments, the volume distribution particle size Dv50 of the positive electrode active material may be 2 μm to 3 μm. As an example, the volume distribution particle size Dv50 of the positive electrode active material may be 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3.0 μm, or a range consisting of any of the above values. Alternatively, the volume distribution particle size Dv50 of the positive electrode active material may be 2.2 μm to 2.8 μm.

[0101] In some embodiments, the volume distribution particle size Dv90 of the positive electrode active material may be 5 μm to 6 μm. As an example, the volume distribution particle size Dv90 of the positive electrode active material may be 5.0 μm, 5.1 μm, 5.2 μm, 5.3 μm, 5.4 μm, 5.5 μm, 5.6 μm, 5.7 μm, 5.8 μm, 5.9 μm, 6.0 μm, or a range consisting of any of the above values. Alternatively, the volume distribution particle size Dv99 of the positive electrode active material may be 7.5 μm to 9 μm.

[0102] In some embodiments, the volume distribution particle size Dv99 of the positive electrode active material may be 7 μm to 10 μm. As an example, the volume distribution particle size Dv99 of the positive electrode active material may be 7.0 μm, 7.2 μm, 7.5 μm, 7.8 μm, 8.0 μm, 8.2 μm, 8.5 μm, 8.8 μm, 9.0 μm, 9.2 μm, 9.5 μm, 9.8 μm, 10.0 μm, or a range consisting of any of the above values. Alternatively, the volume distribution particle size Dv99 of the positive electrode active material may be 7.5 μm to 9 μm.

[0103] In this application, the volume distribution particle sizes Dv2, Dv50, and Dv99 of the positive electrode active material are all well-known in the art and represent the particle sizes corresponding to the cumulative distribution percentages of the positive electrode active material reaching 2%, 50%, and 99%, respectively. According to the embodiments of this application, by limiting the volume distribution particle size of the positive electrode active material to the above ranges, the positive electrode film layer can have an appropriate compaction density and porosity, which is conducive to further improving the energy density and dynamic performance of the battery cell.

[0104] The volume distribution particle sizes Dv2, Dv50, and Dv99 of the positive electrode active material can be measured using methods and instruments known in the art, for example, laser diffraction particle size analysis, referring to standard GB / T19077-2016, using a laser particle size analyzer (e.g., Malvern Master Size 3000).

[0105] In some embodiments, the tap density of the positive electrode active material may be 1.4 g / cm 3 -1.8g / cm 3As an example, the tap density of the positive electrode active material can be 1.4 g / cm 3 , 1.5g / cm 3 , 1.6g / cm 3 , 1.7g / cm 3 , 1.8g / cm 3 , or any range of the above values. Optionally, the tap density of the positive electrode active material can be 1.5 g / cm 3 -1.7g / cm 3 .

[0106] According to the embodiment of the present application, by limiting the tap density of the positive electrode active material to the above range, it is beneficial to make the positive electrode film layer have a higher compaction density, thereby improving the energy density of the battery cell.

[0107] The tap density of the positive electrode active material is a well-known meaning in the art, which refers to the density measured after the powder is tapped under specified conditions. The tap density can be measured using instruments and methods known in the art. For example, it can be measured using a powder tap density tester with reference to GB / T5162-2006. The test instrument can be Dandong Better BT-301, and the test parameters are as follows: vibration frequency 250±15 times / min, amplitude 3±0.2mm, vibration number 5000 times, and graduated cylinder 25mL.

[0108] In some embodiments, at a pressure of 4T, the compaction density of the positive electrode active material can be 3.3 g / cm 3 -3.6g / cm 3 As an example, at a pressure of 4T, the compaction density of the positive electrode active material can be 3.3g / cm 3 、3.4g / cm 3 、3.5g / cm 3 、3.6g / cm 3 , or a range consisting of any of the above values. Optionally, at a pressure of 4T, the compaction density of the positive electrode active material can be 3.4g / cm 3 -3.5g / cm 3 .

[0109] According to the embodiment of the present application, the compaction density of the positive electrode active material is within the above range, which is beneficial to increasing the proportion of active material in the positive electrode film layer, thereby increasing the energy density of the battery cell.

[0110] The compaction density of the positive electrode active material can be measured by methods and instruments known in the art. For example, the compaction density can be measured using an electronic pressure tester (e.g., UTM7305) in accordance with standard GB / T24533-2009. An exemplary test method is as follows: 1 g of the positive electrode active material is weighed and placed on a plate with a bottom area of ​​1.327 cm2 In the mold, a certain pressure is applied and maintained for 30 seconds, then the pressure is released and maintained for 10 seconds, and then the powder compaction density of the positive electrode active material under the pressure is recorded and calculated. In this application, the compaction pressure can be 4T.

[0111] In some embodiments, the BET specific surface area of ​​the positive electrode active material may be 0.6 m 2 / g-1m 2 As an example, the specific surface area of ​​the positive electrode active material can be 0.6 m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1.0m 2 / g. Optionally, the specific surface area of ​​the active material can be 0.7m 2 / g-0.9m 2 / g.

[0112] According to the embodiments of the present application, the specific surface area of ​​the positive electrode active material is within the above range, and it has more contact sites with the electrolyte, which is beneficial to improving the electrolyte wettability of the positive electrode sheet and improving the cycle performance of the battery cell.

[0113] The specific surface area of ​​the positive electrode active material is well known in the art and can be measured using methods and instruments known in the art. For example, it can be measured using the instruments and methods specified in GB / T 19587-2017.

[0114] In some embodiments, the powder resistivity of the positive electrode active material at 12 MPa may be less than or equal to 10,000 Ω·cm. As an example, the powder resistivity of the positive electrode active material at 12 MPa may be 10,000 Ω·cm, 9,000 Ω·cm, 8,000 Ω·cm, 7,000 Ω·cm, 6,000 Ω·cm, 5,000 Ω·cm, 4,000 Ω·cm, 3,000 Ω·cm, 2,000 Ω·cm, 1,000 Ω·cm, 900 Ω·cm, 500 Ω·cm, 100 Ω·cm, 50 Ω·cm, or a range consisting of any of the foregoing values. Alternatively, the powder resistivity of the positive electrode active material at 12 MPa may be 5,000 Ω·cm-8,000 Ω·cm.

[0115] According to the embodiments of the present application, by limiting the powder resistivity of the positive electrode active material to the above range, the positive electrode active material has better conductivity, which is beneficial to further reduce the internal resistance of the battery cell and improve the dynamic performance.

[0116] The powder resistivity of the positive electrode active material is well known and can be measured using methods and instruments known in the art. For example, it can be measured using a powder resistivity tester (ST2722) in accordance with GB / T30835-2014.

[0117] In this application, the elemental composition, volume distribution particle size, tap density, compacted density, specific surface area and powder resistivity of the positive electrode active material can be tested directly on the positive electrode active material sample, or by sampling from the battery cell to obtain a test sample.

[0118] When the test sample is sampled from a battery cell, as an example, the sampling can be carried out in the following steps: discharge the battery cell (generally make the battery in a fully discharged state), disassemble the battery cell and remove the positive electrode sheet, and soak the positive electrode sheet in dimethyl carbonate (DMC) for a certain time (for example, 2 to 10 hours); then take out the positive electrode sheet and dry it at a certain temperature and time (for example, 60°C, 4h), and take out the positive electrode sheet after drying; bake the dried positive electrode sheet at a certain temperature and time (for example, 400°C, 2h), and select an area from the baked positive electrode sheet to sample the positive electrode active material (a blade can be used to scrape the powder for sampling); sieve the collected positive electrode active material (for example, sieve it with a 200-mesh sieve), and finally obtain a positive electrode active material sample that can be used to test the various material parameters mentioned above in this application.

[0119] In some embodiments, the positive electrode active material may include a positive electrode active material having a surface covered with a conductive agent and a positive electrode active material not having a surface covered with a conductive agent. The positive electrode active material having a surface covered with a conductive agent accounts for 20% to 50% of the total amount of the positive electrode active material. For example, the positive electrode active material having a surface covered with a conductive agent accounts for 20%, 25%, 30%, 35%, 40%, 45%, 50%, or a range consisting of any of the foregoing values, optionally 25% to 45%, based on the total amount of the positive electrode active material.

[0120] According to the embodiments of the present application, by ensuring that the proportion of the positive electrode active material with the surface covered by the conductive agent is within the above range, the conductive agent can better form a conductive network in the positive electrode film layer, which is conducive to further improving the conductivity of the positive electrode active material and thus improving the dynamic performance of the battery cell. When the proportion of the positive electrode active material with the surface covered by the conductive agent is low, the conductivity of the positive electrode active material is low and the dynamic performance of the battery cell is poor; when the proportion of the positive electrode active material with the surface covered by the conductive agent is high, the conductive agent located in the gaps between the positive electrode active material particles is reduced, the transmission of lithium ions in the positive electrode active material is hindered, and the dynamic performance of the battery cell is reduced.

[0121] In this application, the mass percentage of the positive electrode active material whose surface is not covered with the conductive agent can be detected by the SEM image of the positive electrode film layer. For example, a certain area (such as 10 μm) can be taken from the SEM image of the positive electrode film layer. 2 ), count the amount of positive electrode active material covered with a conductive agent and the amount of positive electrode active material not covered with a conductive agent in that area, and then calculate the respective percentages. Sampling can be performed in different areas of the SEM image, and the final results are averaged. Figure 6 An SEM image of the positive electrode film layer in one embodiment of the present application is shown. It can be seen that the surface of some positive electrode active materials in the positive electrode film layer is covered with a conductive agent (the positive electrode active materials marked with red numbers are covered with a conductive agent on the surface, and the positive electrode active materials marked with blue numbers are not covered with a conductive agent on the surface). The proportion of each part is obtained by counting the positive electrode active material particles in the SEM image.

[0122] In the present application, the proportion of the positive electrode active material with the conductive agent on the surface can be adjusted by adjusting the amount of conductive agent added, the content of the dispersant in the positive electrode film layer, and the mixing parameters when the positive electrode active material and the dispersant are mixed, such as the slurry stirring speed, the standing time, and the slurry viscosity.

[0123] In some embodiments, the mass percentage of the conductive agent in the positive electrode film layer may be 1%-2% based on the total mass of the positive electrode film layer. As an example, the mass percentage of the conductive agent in the positive electrode film layer may be 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, or a range consisting of any of the above values.

[0124] According to the embodiments of the present application, limiting the content of the conductive agent to the above range is conducive to improving the conductivity of the positive electrode active material, thereby improving the dynamic performance of the battery cell. When the conductive agent content is low, the conductivity of the positive electrode active material is poor, and the dynamic performance of the battery cell is low; when the conductive agent content is high, the proportion of active material decreases, resulting in a decrease in the energy density of the battery cell.

[0125] In some embodiments, the conductive agent may further include one or more of superconducting carbon (Super P), acetylene black, carbon black, Ketjen black (KB), carbon dots, graphene, and carbon nanofibers.

[0126] In some embodiments, the positive electrode film layer further includes a dispersant. Based on the total mass of the positive electrode film layer, the mass percentage of the dispersant in the positive electrode film layer may be 0.1%-0.8%. As an example, the mass percentage of the dispersant in the positive electrode film layer may be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, or any range thereof.

[0127] According to the embodiment of the present application, by adjusting the content ratio of the dispersant in the positive electrode film layer within the above range, it is beneficial to improve the uniformity of dispersion of the conductive agent and the positive electrode active material in the positive electrode film layer, thereby improving the cycle performance of the battery cell.

[0128] In some embodiments, the dispersant may include one or more of N-methylpyrrolidone (NMP), dimethyl sulfoxide, polyacrylic acid (PAA), polyacrylamide (PAM), polyvinyl alcohol (PVA), and polyethylene glycol (PEG).

[0129] In some embodiments, the positive electrode film layer may further include a binder.

[0130] As an example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0131] In some implementations, the weight percentage of the binder in the positive electrode film layer is greater than or equal to 0.5%, which is conducive to obtaining good bonding performance.

[0132] In this application, the thickness of each layer of the positive electrode sheet can be measured and analyzed by SEM (scanning electron microscopy) of the cross-section of the positive electrode sheet, and can also be measured using a laser thickness gauge. In this application, the cross-section of the positive electrode sheet can be microscopically observed, and the micromorphology of the positive electrode current collector, the first positive electrode film layer, and the first positive electrode film layer in the positive electrode sheet, as well as the interfaces between the different layers, can be observed to determine the thickness of each layer and the compression of the positive electrode film layer on the surface of the positive electrode current collector. In this application, the cross-section of the positive electrode sheet refers to the cross-section formed by slicing along the thickness direction of the positive electrode sheet. The cross-section of the positive electrode sheet can be microscopically observed and combined with compositional analysis, such as energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis to determine the types of elements, to confirm the elemental composition of each layer of the positive electrode sheet. In addition, the cross section can be polished using instruments such as a focused electron beam (FIB) electron microscope (such as FEI Scios 2HiVa equipment, etc.), an ion cross section polisher (such as JEOL's IB-09010 CP argon ion cross section polisher, etc.) to obtain a clear cross section.

[0133] In some embodiments, the positive electrode active material may include one or more of layered lithium-containing transition metal oxides, common lithium-containing phosphates, Lushi Blue compounds, polyanion compounds, and sodium transition metal oxides, which are different from the above materials.

[0134] If the positive electrode active material is one or more of lithium-containing phosphates and layered lithium-containing transition metal oxides, 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, polyanion compounds, and sodium transition metal oxides, the positive electrode material can be used in sodium-ion battery cells.

[0135] The lithium-containing phosphate may include one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, and modified compounds thereof.

[0136] Examples of layered lithium-containing transition metal oxides may include one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and modified compounds thereof.

[0137] In some embodiments, the layered lithium-containing transition metal oxide may include a Ni element. The molar amount of the Ni element may account for more than 70% of the total molar amount of the transition metal elements in the layered lithium-containing transition metal oxide; alternatively, the molar amount of the Ni element may account for more than 80% of the total molar amount of the transition metal elements in the layered lithium-containing transition metal oxide; more alternatively, the molar amount of the Ni element may account for more than 90% of the total molar amount of the transition metal elements in the layered lithium-containing transition metal oxide.

[0138] The higher the content of Ni element in the layered lithium-containing transition metal oxide, the higher the energy density of the battery cell.

[0139] In some embodiments, the layered lithium-containing transition metal oxide may include Li a Ni b Co c M d O e A f , where 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; and A includes, but is not limited to, one or more of N, F, S, and Cl. This can further increase the energy density of the battery cell.

[0140] In some embodiments, as an example, the layered lithium-containing transition metal oxide may include but is not limited to LiNi0.8 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 .

[0141] The charge and discharge process of a battery cell is accompanied by the intercalation and deintercalation of Li, and the molar content of Li in the battery cell varies at different discharge states. The molar content of Li in the examples of this application regarding the positive electrode active materials refers to the initial state of the material, i.e., the state before the materials are added. The molar content of Li in the positive electrode active materials used in the battery cell may change after charge and discharge cycles.

[0142] In some embodiments, as examples, sodium transition metal oxides may include, but are not limited to:

[0143] Na 1-x Cu h Fe k Mn l M 1 m O 2-y , where M 1 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;

[0144] Na 0.67 Mn 0.7 Ni z M 2 0.3-z O2, where M2 is one or more of Li, Mg, Al, Ca, Ti, Fe, Cu, Zn and Ba, 0< z ≤0.1;

[0145] Na a Li b Ni c Mn d Fe e O2, of which 0.67< a ≤1,0< b <0.2,0< c <0.3,0.67< d + e <0.8, b + c + d + e =1.

[0146] In some embodiments, the polyanionic compound may include, but is not limited to, for example:

[0147] A 1 f M 3 g (PO4) i O j X 1 3-j , wherein A is one or more of H, Li, Na, K and NH4, M 3 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;

[0148] 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;

[0149] 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;

[0150] Na s Mn t Fe 3-t (PO4)2(P2O7), where 0< s ≤4,0≤ t ≤3, e.g. t is 0, 1, 1.5, 2, or 3.

[0151] In some embodiments, Prussian blue compounds may include, but are not limited to:

[0152] A u M 6 v [M 7 (CN)6] w · x H2O, where A is H + NH4 + , one or more of alkali metal cations and alkaline earth metal cations, M 6 and M 7 Each independently is one or more 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 Ra 2+ One or more of M 6 and M 7 Each is independently a cation of one or more transition metal elements selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn and W. Optionally, A is Li + 、Na + and K + One or more of M 6 It is a cation of one or more transition metal elements among Mn, Fe, Co, Ni and Cu, M 7 It is a cation of one or more transition metal elements among Mn, Fe, Co, Ni and Cu.

[0153] In the examples of the present application regarding the positive electrode active materials, the molar content of O is only a theoretical value. Lattice oxygen release will cause the molar content of O to change, and the actual molar content of O will fluctuate.

[0154] The modified compounds of the above-mentioned positive electrode active materials may be used to perform doping modification and / or surface coating modification on the positive electrode active materials.

[0155] In some embodiments, the positive electrode 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 alloys, copper, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, on a polymer substrate. The polymer substrate may include polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), and the like.

[0156] In some embodiments, the thickness of the positive electrode current collector is 4 μm to 20 μm, optionally 6 μm to 18 μm, and further optionally 8 μm to 16 μm.

[0157] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0158] [Negative electrode]

[0159] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer located on at least one side of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0160] As an example, the negative electrode current collector has two surfaces that face each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two facing 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 sheet, with copper foil being an option.

[0161] As an example, the negative electrode active material may include one or more of artificial graphite, natural graphite, mesophase carbon microspheres, hard carbon, soft carbon, silicon, and silicon-carbon composite materials.

[0162] The silicon-based composite material can be prepared by methods known in the art. For example, it can be prepared by a vapor deposition method using graphite and silicon materials as raw materials.

[0163] 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.

[0164] In some embodiments, the negative electrode film layer may further include a negative electrode binder. For 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, water-based 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).

[0165] In some embodiments, the negative electrode film layer may further include other additives, such as thickeners, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, and the like.

[0166] 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 polymer base layer and a metal layer formed on at least one side of the polymer base layer. By way of example, the metal material may include, but is not limited to, one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. By way of example, the polymer base layer may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0167] The negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode plate may further include a conductive primer 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. The primer layer may be composed of, for example, a conductive agent and a binder. In some embodiments, the negative electrode plate may further include a protective layer covering the surface of the negative electrode film layer.

[0168] 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 to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector and, after drying and roll pressing, forms the negative electrode sheet. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0169] [Electrolytes]

[0170] The battery cells include an electrolyte.

[0171] In some embodiments, the electrolyte is an electrolyte solution including an electrolyte salt and an organic solvent.

[0172] In some embodiments, the electrolyte includes anions, which may include bis(fluorosulfonyl)imide anions (FSI - ), bis(trifluoromethanesulfonyl)imide anion (TFSI - ), dioxalatoborate anion (BOB - ), difluorooxalatoborate anion (DFOB - ), difluorobis(oxaloyl)phosphate anion (DFOP - ), tetrafluorooxalophosphate anion (TFOP - ), difluorophosphate anion (PO2F2 - ), hexafluorophosphate anion (PF6 - ), tetrafluoroborate anion (BF4 - ), hexafluoroarsenate anion (AsF6 - ), trifluoromethanesulfonate anion (CF3SO3 - ) one or more.

[0173] In some embodiments, the electrolyte includes cations, which may include one or more of lithium ions and sodium ions.

[0174] In some embodiments, the concentration of the electrolyte salt may be greater than 0.3 mol / L, and may be greater than 0.7 mol / L. The concentration of the electrolyte salt may further be less than 4 mol / L, and may be less than 2.5 mol / L or less than 1.7 mol / L. When the concentration of the electrolyte salt is within the above range, the electrolyte solution can have suitable ionic conductivity.

[0175] Organic solvent can include but not limited to one or more in esters, ethers, sulfones, nitrile etc.Ester can include but not limited to one or more in carbonate, phosphate, carboxylate, sulfate, sulfonate etc.Carbonate can comprise cyclic carbonate and / or chain carbonate, alternatively, carbonate can comprise cyclic carbonate and chain carbonate simultaneously.Chain carbonate can comprise low-viscosity polar chain carbonate, aliphatic branched-chain carbonate etc.

[0176] As an example, the organic solvent may include, but is not limited to, ethylene carbonate (EC), propylene carbonate (PC), butylene 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), tetraethylene glycol dimethyl ether (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 trifluoromethyl decafluoropentyl methyl ether, 4-trifluoromethyl decafluoropentyl ethyl ether, 4-trifluoromethyl decafluoropentyl propyl ether, 5-trifluoromethyl dodecafluorohexyl methyl ether, 5-trifluoromethyl dodecafluorohexyl ethyl ether, 5-trifluoromethyl dodecafluorohexyl propyl ether, 6-trifluoromethyl tetradecafluoroheptyl methyl ether, 6-trifluoromethyl tetradecafluoroheptyl ethyl ether, 6-trifluoromethyl tetradecafluoroheptyl propyl ether, 7-trifluoromethyl hexafluorooctyl methyl ether, 7-trifluoromethyl hexafluorooctyl ethyl ether, and 7-trifluoromethyl hexafluorooctyl propyl ether.

[0177] 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, or additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature power performance.

[0178] [Isolator]

[0179] In some embodiments, the electrode assembly further includes a separator disposed between the positive electrode sheet and the negative electrode sheet.

[0180] In some embodiments, the separator includes a separator. The present application has no particular limitation on the type of separator, and any known porous structure membrane with good chemical and mechanical stability can be selected.

[0181] In some embodiments, the material of the separator may include at least one of glass fiber, non-woven 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 separate component located between the positive and negative electrodes, or it may be attached to the surface of the positive and negative electrodes. The surface of the separator may also be coated with an inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating.

[0182] In some embodiments, the separator is a solid electrolyte, which is disposed between the positive electrode and the negative electrode, and serves to transport ions and isolate the positive and negative electrodes.

[0183] In some embodiments, the battery cell may further include an outer packaging for housing the electrode assembly formed by assembling the negative electrode sheet, separator, and positive electrode sheet. The outer packaging may be a hard shell, such as a hard plastic shell, aluminum shell, or steel shell. Alternatively, the outer packaging may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as one or more of aluminum-plastic film, polypropylene, polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0184] The preparation methods of battery cells are well known. For example, the assembly methods of battery cells include but are not limited to button cells, molded cells, hard-shell cells, soft-pack cells, etc.

[0185] Example

[0186] The following examples describe the present disclosure in more detail. These examples are intended to be illustrative only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing. The instruments used in the examples are commercially available.

[0187] Example 1

[0188] Positive electrode

[0189] Preparation of positive electrode active material precursor: nickel sulfate, cobalt sulfate and manganese sulfate were mixed in a molar ratio of 0.82:0.08:0.10 to form a sulfate solution; under nitrogen atmosphere, sodium hydroxide solution was added to adjust the pH value of the sulfate solution to 10, 4g / L ammonia water was added, and the reaction was carried out at 60℃ for 48h to prepare the precursor Ni0.82 Co 0.08 Mn 0.10 (OH)2, precursor Ni 0.82 Co 0.08 Mn 0.10 The volume distribution particle size Dv50 of (OH)2 is 3 μm;

[0190] Preparation of core material: Ni precursor 0.82 Co 0.08 Mn 0.10 (OH)2, lithium source LiOH·H2O and doping element source ZrO2, Mo2O3 were mixed in a molar ratio of 1:1.02:0.003:0.001, and then reacted at 850℃ under pure oxygen for 15h to obtain a sintered product. The sintered product was subjected to air flow milling to obtain the core material LiNi 0.82 Co 0.08 Mn 0.1 Zr 0.003 Mo 0.001 O2;

[0191] Preparation of positive electrode active material: core material LiNi 0.82 Co 0.08 Mn 0.1 Zr 0.003 Mo 0.001 O2, Al2O3, MoO3 and Co(OH)2 were mixed in a mass ratio of 1:0.003:0.003:0.004, and then reacted at 720℃ under pure oxygen for 10h to prepare the positive electrode active material. The chemical formula of the core of the positive electrode active material is LiNi 0.82 Co 0.08 Mn 0.1 Zr 0.003 Mo 0.001 O2; the metal elements in the coating layer include Al, Mo and Co. The volume distribution particle size of the positive electrode active material is Dv2 0.8μm, Dv50 is 2.8μm, Dv90 is 5.6μm, Dv99 is 8μm, and the tap density is 1.7g / cm 3 , compacted density is 3.4g / cm 3 , with a specific surface area of ​​0.8m 2 / g, powder resistivity is 6500Ω·cm. In the positive electrode active material, the number of primary particles with a particle size of less than or equal to 8μm accounts for 99%;

[0192] Preparation of positive electrode sheets: The positive electrode active material, binder polyvinylidene fluoride (PVDF), conductive agent CNT, and dispersant polyacrylic acid prepared above were mixed in a mass ratio of 97:1:1.5:0.5, and then added into N-methylpyrrolidone (NMP) and stirred and dispersed evenly to obtain a positive electrode slurry. The positive electrode slurry was coated on both sides of a positive electrode current collector aluminum foil with a thickness of 13 μm, dried at 120°C, and then cold pressed and cut to obtain positive electrode sheets.

[0193] The specific parameters of each part of the positive electrode are shown in Table 1.

[0194] Negative electrode

[0195] Graphite, silicon oxide, sodium carboxymethyl cellulose, styrene-butadiene rubber and acetylene black were mixed in a mass ratio of 89:7:1:1:2, deionized water was added, and the mixture was stirred evenly in a blender. The slurry was then coated on both sides of an 8-micron-thick copper foil, dried in an oven at 120°C, cold pressed, and cut to obtain negative electrode sheets.

[0196] Isolation film

[0197] A polyethylene (PE) film with a thickness of 12 μm was selected.

[0198] electrolyte

[0199] Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a mass ratio of 3:7, and an electrolyte salt, lithium bis(fluorosulfonyl)imide (LIFSI), was added and mixed to obtain an electrolyte solution, wherein the concentration of lithium bis(fluorosulfonyl)imide was 1 mol / L.

[0200] battery cells

[0201] The positive electrode sheet, negative electrode sheet and separator are stacked in order, ensuring that the positive and negative electrode sheets cannot contact each other, and then they are wound using a winding needle to obtain an electrode assembly. The electrode assembly is placed in a square aluminum shell, and the electrolyte is injected. The battery is placed in a standing position, formed, and charged to obtain a battery cell.

[0202] Example 2-Example 6

[0203] The preparation method of the battery cell is similar to that of Example 1, except that the particle size parameters of the positive electrode active material are adjusted. The specific parameter adjustments are detailed in Table 1.

[0204] Comparative Example 1

[0205] The preparation method of the battery cell is similar to that of Example 1, except that the particle size parameters of the positive electrode active material are adjusted. The specific parameter adjustments are detailed in Table 1.

[0206] Table 1

[0207]

[0208] Example 7-Example 11

[0209] The preparation method of the battery cell is similar to that of Example 1, except that the chemical composition parameters of the positive electrode active material are adjusted. The specific parameter adjustments are detailed in Table 2.

[0210] Comparative Example 2

[0211] The preparation method of the battery cell is similar to that of Example 1, except that the chemical composition parameters of the positive electrode active material are adjusted. The specific parameter adjustments are detailed in Table 2.

[0212] Table 2

[0213]

[0214] Examples 12-15

[0215] The preparation method of the battery cell is similar to that of Example 1, except that the parameters of the conductive agent are adjusted. The specific parameter adjustments are detailed in Table 3.

[0216] Table 3

[0217]

[0218] Test section

[0219] 1. Cycle performance

[0220] At 25°C, charge the battery cell to 4.3V at 0.33C, then charge it to 0.05C at a constant voltage of 4.3V, and then discharge it to 2.8V at 0.33C, and record the first cycle discharge capacity C0; then charge the battery cell to 4.3V at a rate of 1C0, then charge it to 0.05C at a constant voltage of 4.3V, and then discharge it to 2.8V at 1C0, and record the first cycle discharge capacity C1. Continue to charge and discharge the battery cell at a rate of 1C0 in the above manner, and record the discharge capacity of the battery cell in the 1000th cycle as C 1000 , cycle capacity retention rate (%) = C 1000 / C1×100%.

[0221] 2. Internal resistance DCR

[0222] At 25°C, charge the battery at a constant current of 0.33C to a cutoff voltage of 4.3V. Then charge at a constant voltage of 4.3V to a current of 0.05C, at which point the battery is fully charged. After the fully charged battery rests for 5 minutes, discharge it at a current of 0.33C to a SOC of 90%. Record the voltage V1. Then discharge it at a current of 4C for 30 seconds. Record the voltage V2. Calculate the battery's charge and discharge internal resistance (DCR) as (V2 - V1) / discharge current.

[0223] 3. Energy density

[0224] At 25°C, the battery cell is charged at a constant current of 0.33C to a cut-off voltage of 4.3V, and then charged at a constant voltage of 4.3V to a current of 0.05C. At this time, the battery cell is fully charged. After the fully charged secondary battery is left to stand for 5 minutes, it is discharged at a constant current of 0.33C to a cut-off voltage of 2.8V. The discharge capacity at this time is the actual capacity of the battery cell at 0.33C, recorded as C0;

[0225] The battery cell is then charged at a constant current of 0.33C0 to a cut-off voltage of 4.3V, and continued to be charged at a constant voltage to a current of 0.05C. At this time, the battery cell is fully charged. After the fully charged battery cell is allowed to stand for 5 minutes, it is discharged at a constant current of 0.33C0 to a cut-off voltage of 2.8V. The discharge energy Q (Wh) of the secondary battery is obtained, and the volume of the battery cell is measured as V (L). The volume energy density of the battery cell (Wh / L) = Q / V.

[0226] The performance test data is detailed in Table 4.

[0227] Table 4

[0228]

[0229] Combined with the data in Table 1 and Table 2, the embodiments of the present application can improve the cycle performance and kinetic performance of the battery cell while maintaining high energy density by adjusting the positive electrode active material and the conductive agent.

[0230] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, characterized in that: The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector, the positive electrode film layer includes a positive electrode active material and a conductive agent, and part of the conductive agent covers the surface of the positive electrode active material; The positive electrode active material includes a core body and a coating material coated on at least a portion of the surface of the core body, wherein the core body includes a lithium-containing transition metal oxide, the lithium-containing transition metal oxide includes a Ni element, and based on the total molar amount of the transition metal elements in the lithium-containing transition metal oxide, the molar proportion of the Ni element is greater than or equal to 50% and less than 100%; the coating material includes a metal element; The positive electrode active material includes primary particles with a particle size of 8 μm or less, and the number of the primary particles with a particle size of 8 μm or less accounts for greater than or equal to 99% based on the total number of particles of the positive electrode active material; The conductive agent includes carbon nanotubes, and the carbon nanotubes include carbon nanotube aggregates. The number of the carbon nanotube aggregates within a range of 5 μm×5 μm in the positive electrode film layer is less than or equal to 16.

2. The battery cell according to claim 1, wherein: The primary particles include first particles having a particle size greater than or equal to 0.5 μm and less than or equal to 2 μm. Based on the total number of the primary particles, the first particles account for 85%-93% of the total number of the primary particles.

3. The battery cell according to claim 1, characterized in that The primary particles further include second particles having a particle size of less than 0.5 μm and greater than or equal to 0.3 μm. Based on the total number of the primary particles, the number of the second particles accounts for 3%-6%.

4. The battery cell according to claim 1, wherein: The primary particles further include third particles having a particle size of less than 0.3 μm. Based on the total number of the primary particles, the third particles account for less than or equal to 0.3%.

5. The battery cell according to claim 1, characterized in that The primary particles further include fourth particles having a particle size greater than 2 μm and less than or equal to 3 μm. Based on the total number of the primary particles, the fourth particles account for 2.5%-8%.

6. The battery cell according to claim 1, characterized in that The primary particles further include fifth particles having a particle size greater than 3 μm and less than or equal to 8 μm. Based on the total number of the primary particles, the number of the fifth particles accounts for less than or equal to 1.5%.

7. The battery cell according to claim 1, characterized in that The core comprises a lithium-containing transition metal oxide having the following chemical formula: Li a Ni b Co c M d Q e O f , M includes one or two of Mn and Al, Q includes one or more of Mo, W, Sb, Nb, V, Zr, Sr, and Y; 0.8≤a≤1.1, 0.7≤b<1, 0.04≤c<1, 0.05≤d<1, b+c+d=1, 0.001≤e≤0.01, and 1.8≤f≤2.

2.

8. The battery cell according to claim 7, characterized in that 0.8≤b≤0.92,0.04≤c≤0.12,0.05≤d≤0.15,0.001≤e≤0.

005.

9. The battery cell according to claim 7 or 8, characterized in that: The metal elements include one or more of Al, Co, B, Ti, Nb, Sb, Sr, and Y.

10. The battery cell according to claim 1, characterized in that Based on the total mass of the positive electrode active material, the mass percentage of the metal element is 0.1%-0.9%.

11. The battery cell according to claim 1, characterized in that The coating material forms a coating layer on at least a portion of the surface of the core body, and the thickness of the coating layer is greater than 0 and less than or equal to 150 nm.

12. The battery cell according to claim 11, characterized in that The thickness of the coating layer is 50nm-100nm.

13. The battery cell according to claim 1, characterized in that The positive electrode active material satisfies at least one of the following conditions (1) to (8): (1) The volume distribution particle size Dv2 of the positive electrode active material is 0.5 μm-1.4 μm; (2) The volume distribution particle size Dv50 of the positive electrode active material is 2 μm-3 μm; (3) The volume distribution particle size Dv90 of the positive electrode active material is 5 μm-6 μm; (4) The volume distribution particle size Dv99 of the positive electrode active material is 7 μm-10 μm; (5) The tap density of the positive electrode active material is 1.4 g / cm 3 -1.8g / cm 3 ; (6) Under a pressure of 4T, the compaction density of the positive electrode active material is 3.3g / cm 3 -3.6g / cm 3 ; (7) The BET specific surface area of ​​the positive electrode active material is 0.6 m 2 / g-1m 2 / g; (8) The powder resistivity of the positive electrode active material at 12 MPa is less than or equal to 10,000 Ω·cm.

14. The battery cell according to claim 1, characterized in that The positive electrode active material includes a positive electrode active material whose surface is covered with the conductive agent and a positive electrode active material whose surface is not covered with the conductive agent. Based on the total amount of the positive electrode active material, the amount of the positive electrode active material whose surface is covered with the conductive agent accounts for 20%-50%.

15. The battery cell according to claim 1, characterized in that Based on the total mass of the positive electrode film layer, the mass percentage of the conductive agent in the positive electrode film layer is 1%-2%.

16. A battery device, characterized in that: The invention comprises the battery cell according to any one of claims 1 to 15.

17. An electrical device, characterized in that: The battery cell comprises the battery cell according to any one of claims 1 to 15 or the battery device according to claim 16.

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