Battery cell, positive electrode sheet, and electric device

Abstract

The present application discloses a battery cell, a positive electrode sheet, and an electric device. The battery cell comprises a positive electrode sheet. The positive electrode sheet comprises a current collector, and a positive electrode active material layer arranged on at least one side of the surface of the current collector. Under the condition that the state of charge (SOC) of the battery cell is 0%, the compaction density of a single-sided film layer of the positive electrode sheet is 3.55-3.80 g / cm3, and the volume‑based particle size distribution of a positive electrode active material in the positive electrode active material layer satisfies: Dv99≤23 μm. The technical solution of the present application increases the energy density of batteries while prolonging the service life of the batteries.

Description

Battery cells, positive electrode plates and electrical devices

[0001] Related applications

[0002] This application claims priority to Chinese patent application No. 202510307416.6, filed on March 14, 2025, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of battery technology, specifically to a battery cell, a positive electrode sheet, and an electrical device. Background Technology

[0004] In recent years, with the increasingly wide range of applications, batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace.

[0005] With the application and promotion of batteries, higher requirements have been placed on battery energy density and lifespan. Summary of the Invention

[0006] This application addresses the aforementioned issues and aims to provide a battery cell, a positive electrode, and an electrical device. The goal is to improve battery energy density while extending battery life.

[0007] To achieve the above objectives, in a first aspect, this application provides a battery cell including a positive electrode sheet, wherein the positive electrode sheet includes a current collector and a positive active material layer disposed on at least one side of the surface of the current collector;

[0008] Wherein, under the condition that the state of charge (SOC) of the battery cell is 0%, the compaction density of the single-sided film layer of the positive electrode sheet is 3.55–3.80 g / cm³. 3 The volume distribution particle size of the positive electrode active material in the positive electrode active material layer satisfies: Dv99≤23μm.

[0009] Therefore, the high positive electrode compaction density in the technical solution of this application is beneficial to improving the energy density of the battery. At the same time, by controlling the Dv99 of the positive active material in the positive active material layer within the aforementioned suitable range, the particle size of larger particles can be controlled, avoiding the current collector being squeezed, deformed, or even damaged by larger positive active material particles under high compaction density, thereby extending the battery's service life.

[0010] In any embodiment, the positive electrode active material satisfies at least one of the following conditions: (1) the volume distribution particle size of the positive electrode active material satisfies: 18μm≤Dv99≤23μm; (2) the volume distribution particle size of the positive electrode active material satisfies: 4.5μm≤Dv50≤9.5μm; (3) the particle size distribution span (Dv90-Dv10) / Dv50 of the positive electrode active material is 1.23~2.70. Therefore, on the one hand, by controlling the particle size distribution of the positive electrode active material, matching positive electrode active material particles of different sizes is achieved, increasing the compaction density of the positive electrode film, thereby improving the energy density of the battery. On the other hand, by controlling the particle size distribution of the positive electrode active material, the current collector is prevented from being squeezed, deformed, or even damaged by larger positive electrode active material particles under high compaction density conditions.

[0011] In any embodiment, the positive electrode active material comprises a lithium-containing transition metal oxide. This material has a high specific capacity, which can improve the energy density of the battery cell.

[0012] In any embodiment, the lithium-containing transition metal oxide includes Li m Ni a Co b Mn c M d The material for O2, M, includes at least one of Zr, Al, Cu, Mg, Zn, Ti, V, Ga, Sn, Ge, B, Ta, Mo, W, Nb, Sb, Sr, and La; wherein a+b+c+d=1, 0.8≤m≤1.2, 0.5≤a<1, 0≤b≤0.5, 0≤c<0.3, and 0≤d<0.2. This material has a high specific capacity and a relatively stable crystal structure, which is beneficial for improving the compaction density of the positive electrode film, thereby increasing the energy density and lifespan of the battery cell.

[0013] In any embodiment, the positive electrode active material includes a first lithium-containing transition metal oxide with a primary particle morphology and a second lithium-containing transition metal oxide with a secondary particle morphology. The particle size matching effect between the positive electrode active material particles with different morphologies is utilized to fully utilize the packing space of the positive electrode active material, thereby increasing the compaction density of the positive electrode film.

[0014] In any embodiment, the mass ratio of the second lithium-containing transition metal oxide to the first lithium-containing transition metal oxide is 6:4 to 8:2. Using this suitable ratio is beneficial for increasing the compaction density of the cathode film.

[0015] In any embodiment, the first lithium-containing transition metal oxide includes Li m1 Ni a1 Co b1 Mn c1M d1 O₂, wherein M comprises at least one of Zr, Al, Cu, Mg, Zn, Ti, V, Ga, Sn, Ge, B, Ta, Mo, W, Nb, Sb, Sr and La; wherein a1+b1+c1+d1=1, 0.8≤m1≤1.2, 0.8≤a1<1, 0≤b1≤0.2, 0≤c1<0.2, 0≤d1<0.2; and / or, the second lithium-containing transition metal oxide comprises Li m2 Ni a2 Co b2 Mn c2 M d2 O₂, wherein M comprises at least one of Zr, Al, Cu, Mg, Zn, Ti, V, Ga, Sn, Ge, B, Ta, Mo, W, Nb, Sb, Sr and La; wherein a2+b2+c2+d2=1, 0.8≤m2≤1.2, 0.8≤a2<1, 0≤b2≤0.2, 0≤c2<0.2, 0≤d2<0.2. The adoption of the first lithium-containing transition metal oxide material and the second lithium-containing transition metal oxide material with high nickel content is beneficial to increasing the energy density of battery cells.

[0016] In any embodiment, the first lithium-containing transition metal oxide and the second lithium-containing transition metal oxide satisfy: the absolute value of the difference between a1 and a2 is less than 0.1. The adoption of the first lithium-containing transition metal oxide material and the second lithium-containing transition metal oxide material with similar nickel contents is conducive to uniform structure of the positive electrode film layer, and under the condition of high compaction density of the positive electrode film layer, facilitates uniform stress distribution and reduces damage to a current collector.

[0017] In any embodiment, the current collector satisfies at least one of the following conditions: (1) the tensile strength of the current collector is 250 to 330 MPa; (2) the thickness T of the current collector is 10 to 15 μm; (3) the ratio of the volume distribution particle diameter Dv99 of the positive electrode active material in the positive electrode active material layer to the thickness T of the current collector satisfies the following condition: 1<Dv99 / T<2. When the tensile strength of the current collector is within a suitable range, it is beneficial to reducing deformation and fracture of the current collector under the high compaction density condition of the positive electrode film layer. When the thickness of the current collector is within the suitable range, it is beneficial to providing a good bearing effect and preventing the current collector from being broken or damaged by compression under the high compaction density condition. When the ratio of the volume distribution particle diameter Dv99 of the positive electrode active material to the thickness of the current collector is within the above-mentioned suitable range, it is beneficial to preventing the current collector from being extruded to deform or even damaged by larger particles of the positive electrode active material under the condition of high compaction density, thereby prolonging the service life of a battery.

[0018] In any embodiment, the current collector is made of aluminum foil, which comprises aluminum, silicon, and iron. The aluminum content in the aluminum foil is greater than or equal to 99.3% by mass, the silicon content is 0.05% to 0.20% by mass, and the iron content is 0.20% to 0.40% by mass. A suitable element ratio in this material helps to improve the tensile strength of the current collector and reduces deformation and breakage of the current collector under high pressure and density conditions of the positive electrode film.

[0019] In any embodiment, the elongation at break of the positive electrode is 1.6% to 2.4%. This is beneficial for extending the battery's lifespan.

[0020] Secondly, this application provides a positive electrode sheet, comprising a current collector and a positive active material layer disposed on at least one side of the surface of the current collector; wherein, under the condition that the state of charge (SOC) of the battery cell is 0%, the compaction density of a single-sided film layer of the positive electrode sheet is 3.55–3.80 g / cm³. 3 The volume distribution particle size of the positive electrode active material in the positive electrode active material layer satisfies: Dv99≤23μm.

[0021] Using a high positive electrode compaction density is beneficial for improving the energy density of the battery. At the same time, by controlling the Dv99 of the positive active material in the positive active material layer within the aforementioned suitable range, the particle size of larger particles can be controlled, avoiding the current collector being squeezed, deformed, or even damaged by larger positive active material particles under high compaction density, thereby extending the battery's lifespan.

[0022] In any embodiment, the positive electrode active material satisfies at least one of the following conditions: (1) the volume distribution particle size of the positive electrode active material satisfies: 18μm≤Dv99≤23μm; (2) the volume distribution particle size of the positive electrode active material satisfies: 4.5μm≤Dv50≤9.5μm; (3) the particle size distribution span (Dv90-Dv10) / Dv50 of the positive electrode active material is 1.23~2.70. Therefore, on the one hand, by controlling the particle size distribution of the positive electrode active material, matching positive electrode active material particles of different sizes is achieved, increasing the compaction density of the positive electrode film, thereby improving the energy density of the battery. On the other hand, by controlling the particle size distribution of the positive electrode active material, the current collector is prevented from being squeezed, deformed, or even damaged by larger positive electrode active material particles under high compaction density conditions.

[0023] In any embodiment, the positive electrode active material comprises a lithium-containing transition metal oxide. This material has a high specific capacity, which can improve the energy density of the battery cell.

[0024] In any embodiment, the lithium-containing transition metal oxide includes Lim Ni a Co b Mn c M d The material for O2, M, includes at least one of Zr, Al, Cu, Mg, Zn, Ti, V, Ga, Sn, Ge, B, Ta, Mo, W, Nb, Sb, Sr, and La; wherein a+b+c+d=1, 0.8≤m≤1.2, 0.5≤a<1, 0≤b≤0.5, 0≤c<0.3, and 0≤d<0.2. This material has a high specific capacity and a relatively stable crystal structure, which is beneficial for improving the compaction density of the positive electrode film, thereby increasing the energy density and lifespan of the battery cell.

[0025] In any embodiment, the positive electrode active material includes a first lithium-containing transition metal oxide with a primary particle morphology and a second lithium-containing transition metal oxide with a secondary particle morphology. The particle size matching effect between the positive electrode active material particles with different morphologies is utilized to fully utilize the packing space of the positive electrode active material, thereby increasing the compaction density of the positive electrode film.

[0026] In any embodiment, the mass ratio of the second lithium-containing transition metal oxide to the first lithium-containing transition metal oxide is 6:4 to 8:2. Using this suitable ratio is beneficial for increasing the compaction density of the cathode film.

[0027] In any embodiment, the first lithium-containing transition metal oxide includes Li m1 Ni a1 Co b1 Mn c1 M d1 The material of O2, M includes at least one of Zr, Al, Cu, Mg, Zn, Ti, V, Ga, Sn, Ge, B, Ta, Mo, W, Nb, Sb, Sr, and La; wherein a1+b1+c1+d1=1, 0.8≤m1≤1.2, 0.8≤a1<1, 0≤b1≤0.2, 0≤c1<0.2, and 0≤d1<0.2; and / or, the second lithium-containing transition metal oxide includes Li m2 Ni a2 Co b2 Mn c2 M d2a material of O2, M comprises at least one of Zr, Al, Cu, Mg, Zn, Ti, V, Ga, Sn, Ge, B, Ta, Mo, W, Nb, Sb, Sr and La; wherein a2+b2+c2+d2=1, 0.8≤m2≤1.2, 0.8≤a2<1, 0≤b2≤0.2, 0≤c2<0.2, 0≤d2<0.2. Adoption of the first lithium-containing transition metal oxide material and the second lithium-containing transition metal oxide material with the above high nickel content is beneficial to increasing the energy density of the battery cell.

[0028] In any embodiment, the first lithium-containing transition metal oxide and the second lithium-containing transition metal oxide satisfy that the absolute value of the difference between a1 and a2 is less than 0.1. Adoption of the first lithium-containing transition metal oxide material and the second lithium-containing transition metal oxide material with similar nickel contents is beneficial to making the structure of the positive electrode film layer uniform, and under the condition of high compaction density of the positive electrode film layer, is beneficial to uniform stress distribution and reducing damage to the current collector.

[0029] In any embodiment, the current collector satisfies at least one of the following conditions: (1) the tensile strength of the current collector is 250 to 330 MPa; (2) the thickness T of the current collector is 10 to 15 μm; (3) the ratio of the volume distribution particle size Dv99 of the positive electrode active material in the positive electrode active material layer to the thickness T of the current collector satisfies the following condition: 1<Dv99 / T<2. When the tensile strength of the current collector is within a suitable range, it is beneficial to reducing deformation and fracture of the current collector under the high compaction density condition of the positive electrode film layer. When the thickness of the current collector is within the suitable range, it is beneficial to providing a good bearing effect and avoiding the current collector being broken or damaged by compression under the high compaction density condition. When the ratio of the volume distribution particle size Dv99 of the positive electrode active material to the thickness of the current collector is within the above suitable range, it is beneficial to avoiding the situation that the current collector is extruded and deformed or even damaged by larger particles of the positive electrode active material under the condition of high compaction density, thereby prolonging the service life of the battery.

[0030] In any embodiment, the material of the current collector comprises aluminum foil, the aluminum foil comprises aluminum, silicon and iron, the mass proportion of aluminum in the aluminum foil is greater than or equal to 99.3%, the mass proportion of silicon in the aluminum foil is 0.05% to 0.20%, and the mass proportion of iron in the aluminum foil is 0.20% to 0.40%. The suitable element ratio in the material is beneficial to improving the tensile strength of the current collector and reducing deformation and fracture of the current collector under the high compaction density condition of the positive electrode film layer.

[0031] In any embodiment, the elongation at break of the positive electrode plate is 1.6% to 2.4%. Thereby, it is beneficial to prolonging the service life of the battery.

[0032] In a third aspect, the present application provides an electric device, comprising the battery cell according to the first aspect of the present application. Attached Figure Description

[0033] Figure 1 is a schematic diagram of a battery cell according to an embodiment of this application;

[0034] Figure 2 is an exploded view of a battery cell according to an embodiment of this application shown in Figure 1;

[0035] Figure 3 is a schematic diagram of a battery module according to an embodiment of this application;

[0036] Figure 4 is a schematic diagram of a battery pack according to an embodiment of this application;

[0037] Figure 5 is an exploded view of the battery pack of one embodiment of this application shown in Figure 4;

[0038] Figure 6 is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to an embodiment of this application.

[0039] Explanation of reference numerals in the attached diagram: 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0040] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the battery cell, positive electrode, and electrical device of this application. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0041] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0042] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0043] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0044] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0045] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0046] The battery mentioned in the embodiments of this application can be a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in this application can include battery cells, battery modules, or battery packs.

[0047] A battery cell is the smallest unit that makes up a battery, and it can independently perform the functions of charging and discharging. When there are multiple battery cells, they are connected in series, parallel, or mixed through a busbar. This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 shows a square battery cell 5 as an example.

[0048] In some embodiments, the battery can be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. In some embodiments, the battery can be a battery pack, which includes a housing and battery cells, with the battery cells or battery modules housed in the housing. In some embodiments, the housing can be part of the vehicle's chassis structure. For example, a portion of the housing can be at least a part of the vehicle's floor, or a portion of the housing can be at least a part of the vehicle's crossbeams and longitudinal beams.

[0049] In some implementations, the battery can be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0050] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0051] Figure 3 shows a battery module 4 as an example. Referring to Figure 3, in the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 5 can be fixed in place using fasteners.

[0052] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0053] In some embodiments, the aforementioned battery cells and battery modules can also be assembled into a battery pack. The number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0054] Figures 4 and 5 show a battery pack 1 as an example. Referring to Figures 4 and 5, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0055] In one embodiment of this application, a battery cell is provided.

[0056] A single battery cell includes electrode components and an electrolyte.

[0057] The electrode assembly includes a positive electrode and a negative electrode. During the charging and discharging process of the battery, active ions move back and forth between the positive and negative electrode plates, inserting and extracting.

[0058] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0059] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0060] In some embodiments, referring to FIG2, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. A positive electrode sheet, a negative electrode sheet, and a separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell 5 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0061] In a first aspect, this application provides a battery cell including a positive electrode sheet, wherein the positive electrode sheet includes a current collector and a positive active material layer disposed on at least one side of the surface of the current collector, wherein, under the condition that the state of charge (SOC) of the battery cell is 0%, the compaction density of a single-sided film layer of the positive electrode sheet is 3.55–3.80 g / cm³. 3 The volume distribution particle size of the positive electrode active material in the positive electrode active material layer satisfies: Dv99≤23μm.

[0062] Therefore, the high positive electrode compaction density in the technical solution of this application is beneficial to improving the energy density of the battery. At the same time, by controlling the Dv99 of the positive active material in the positive active material layer within the aforementioned suitable range, the particle size of larger particles can be controlled, avoiding the current collector being squeezed, deformed, or even damaged by larger positive active material particles under high compaction density, thereby extending the battery's service life.

[0063] In this application, by way of example, under the condition that the state of charge (SOC) of the battery cell is 0%, the compaction density of the single-sided film layer of the positive electrode sheet can be 3.55 g / cm³. 3 3.6g / cm 3 3.65g / cm 3 3.7g / cm 3 3.75g / cm 3 3.80g / cm 3 Or a range of values ​​consisting of any two of the above values.

[0064] The compaction density of the electrode is a well-known concept in the art and can be tested using methods known in the art. With the state of charge (SOC) of the battery cell at 0%, the electrode is removed from the battery, and a certain area of ​​the electrode is taken. The mass and thickness of the electrode and the current collector after removing the film layer are measured respectively. The compaction density of the electrode is calculated according to the following formula: Electrode compaction density = (Electrode mass - Current collector mass) / [(Electrode thickness - Current collector thickness) × Electrode area].

[0065] In this application, the volumetric distribution particle size Dv99 represents the particle size corresponding to a cumulative volumetric distribution percentage of 99%, which can be determined using instruments and methods known in the art. For example, it can be conveniently determined using a laser particle size analyzer, referring to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method. The testing instrument can be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0066] In some embodiments, the positive electrode active material satisfies at least one of the following conditions: (1) the volume distribution particle size of the positive electrode active material satisfies: 18μm≤Dv99≤23μm; (2) the volume distribution particle size of the positive electrode active material satisfies: 4.5μm≤Dv50≤9.5μm; (3) the particle size distribution span (Dv90-Dv10) / Dv50 of the positive electrode active material is 1.23~2.70. Thus, on the one hand, by controlling the particle size distribution of the positive electrode active material, matching positive electrode active material particles of different sizes is achieved, increasing the compaction density of the positive electrode film, thereby improving the energy density of the battery. On the other hand, by controlling the particle size distribution of the positive electrode active material, the current collector is prevented from being squeezed, deformed, or even damaged by larger positive electrode active material particles under high compaction density conditions.

[0067] For example, the volume distribution particle size Dv99 of the positive electrode active material can be any range consisting of two values ​​from 18 μm, 19 μm, 20 μm, 21 μm, 21.5 μm, 22 μm, 22.5 μm, 23 μm, or higher. The volume distribution particle size Dv50 of the positive electrode active material can be any range consisting of two values ​​from 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, or higher. The particle size distribution span (Dv90-Dv10) / Dv50 of the positive electrode active material can be any range consisting of two values ​​from 1.23, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, or higher.

[0068] In this application, the volumetric particle size Dv50 represents the particle size corresponding to a cumulative volumetric distribution percentage of 50%, which can be determined using instruments and methods known in the art. For example, it can be conveniently determined using a laser particle size analyzer, referring to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method. The testing instrument can be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0069] In some embodiments, the positive electrode active material comprises a lithium-containing transition metal oxide. This material has a high specific capacity, which can improve the energy density of the battery cell.

[0070] In some embodiments, the lithium-containing transition metal oxide includes Li m Ni a Co b Mn c M dThe material for O2, M, includes at least one of Zr, Al, Cu, Mg, Zn, Ti, V, Ga, Sn, Ge, B, Ta, Mo, W, Nb, Sb, Sr, and La; wherein a+b+c+d=1, 0.8≤m≤1.2, 0.5≤a<1, 0≤b≤0.5, 0≤c<0.3, and 0≤d<0.2. This material has a high specific capacity and a relatively stable crystal structure, which is beneficial for improving the compaction density of the positive electrode film, thereby increasing the energy density and lifespan of the battery cell.

[0071] In some implementations, m can be a range of values ​​consisting of any two values, such as 0.8, 0.9, 1.0, 1.1, 1.2, or higher.

[0072] In some implementations, 'a' can be a range of values ​​consisting of any two values ​​from 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 0.98, 0.99, or above.

[0073] In some implementations, b can be a range of values ​​consisting of any two values, such as 0, 0.1, 0.2, 0.3, 0.4, 0.5, or higher.

[0074] In some implementations, c can be a range of values ​​consisting of any two values, such as 0, 0.05, 0.1, 0.15, 0.2, 0.25, or more.

[0075] In some implementations, d can be a range of values ​​consisting of any two values, such as 0, 0.05, 0.1, 0.15, or higher.

[0076] The chemical formula of lithium-containing transition metal oxides can be confirmed using any method and testing equipment in the field. For example, the following is an example: Specifically, the battery is disassembled to obtain the positive electrode. After the positive electrode film is peeled off from the current collector, it is dissolved in N-methylpyrrolidone solvent. After the binder, dispersant, etc. in the positive electrode film are dissolved in the solvent, it is filtered and dried to obtain the sample to be tested. It is digested with HF and added to an ICP-OES instrument to detect the content of Li, Ni, Co, Mn, Al, and M elements, so as to obtain the specific molar ratio of the element content and the specific chemical composition.

[0077] In some embodiments, the positive electrode active material includes a first lithium-containing transition metal oxide with a primary particle morphology and a second lithium-containing transition metal oxide with a secondary particle morphology. The particle size matching effect between the positive electrode active material particles with different morphologies is utilized to fully utilize the packing space of the positive electrode active material, thereby increasing the compaction density of the positive electrode film.

[0078] In this application, the term "particle with primary particle morphology" refers to a primary particle, which is the smallest unit of a particle within a certain observation range. A primary particle may contain defects of any form, but it is impossible to further define smaller particles within a primary particle. Primary particles may aggregate under physical forces such as van der Waals forces, but such aggregation is easily deaggregated under external forces such as ultrasound, stirring, and rolling, so that the main component morphology of the active material in the film layer remains primary particles.

[0079] In this application, the term "secondary particle morphology" refers to secondary particles, which are formed by the aggregation of primary particles. They are not easily dispersed under external forces such as ultrasound. However, after cutting the cross-section of the secondary particles, it can be seen that the secondary particles are formed by the aggregation of numerous primary particles.

[0080] The morphology of primary and secondary particles can be determined by observing the particle morphology of the cross-section along the thickness direction of the positive electrode sheet.

[0081] In some embodiments, the mass ratio of the second lithium-containing transition metal oxide to the first lithium-containing transition metal oxide is 6:4 to 8:2. This suitable ratio allows for full utilization of the packing space of the positive electrode active material, thereby increasing the compaction density of the positive electrode film. For example, the mass ratio of the second lithium-containing transition metal oxide to the first lithium-containing transition metal oxide can be 6:4, 7:4, 8:4, 6:2, 7:2, 8:2, or any two of these values ​​within a range.

[0082] In some embodiments, the first lithium-containing transition metal oxide includes Li m1 Ni a1 Co b1 Mn c1 M d1 The material of O2, M includes at least one of Zr, Al, Cu, Mg, Zn, Ti, V, Ga, Sn, Ge, B, Ta, Mo, W, Nb, Sb, Sr, and La; wherein a1+b1+c1+d1=1, 0.8≤m1≤1.2, 0.8≤a1<1, 0≤b1≤0.2, 0≤c1<0.2, and 0≤d1<0.2; the second lithium-containing transition metal oxide includes Li m2 Ni a2 Co b2 Mn c2 M d2a material of O2, M comprises at least one of Zr, Al, Cu, Mg, Zn, Ti, V, Ga, Sn, Ge, B, Ta, Mo, W, Nb, Sb, Sr and La; wherein a2+b2+c2+d2=1, 0.8≤m2≤1.2, 0.8≤a2<1, 0≤b2≤0.2, 0≤c2<0.2, 0≤d2<0.2. The adoption of the first lithium-containing transition metal oxide material and the second lithium-containing transition metal oxide material with high nickel content is beneficial for improving the energy density of the battery cell.

[0083] In some embodiments, the first lithium-containing transition metal oxide and the second lithium-containing transition metal oxide satisfy: the absolute value of the difference between a1 and a2 is less than 0.1. The adoption of the first lithium-containing transition metal oxide material and the second lithium-containing transition metal oxide material with similar nickel contents is beneficial for making the structure of the positive electrode film layer uniform, and under the condition of high compaction density of the positive electrode film layer, is beneficial for uniform stress distribution and reducing damage to the current collector.

[0084] In some embodiments, the current collector satisfies at least one of the following conditions: (1) the tensile strength of the current collector is 250 to 330 MPa; (2) the thickness T of the current collector is 10 to 15 μm; (3) the ratio of the volume distribution particle diameter Dv99 of the positive electrode active material in the positive electrode active material layer to the thickness T of the current collector satisfies the following condition: 1<Dv99 / T<2. When the tensile strength of the current collector is in a suitable range, it is beneficial for reducing deformation and fracture of the current collector under the high compaction density condition of the positive electrode film layer. When the thickness of the current collector is within the suitable range, it is beneficial for providing a good bearing effect and avoiding the current collector being broken or damaged by compression under the high compaction density condition. When the ratio of the volume distribution particle diameter Dv99 of the positive electrode active material to the thickness of the current collector is within the above suitable range, it is beneficial for avoiding the situation that the current collector is extruded and deformed or even damaged by larger particles of the positive electrode active material under the condition of high compaction density, thereby prolonging the service life of the battery.

[0085] Exemplarily, the tensile strength of the current collector may be 250 MPa, 260 MPa, 270 MPa, 280 MPa, 290 MPa, 300 MPa, 310 MPa, 320 MPa, 330 MPa, or a numerical range formed by any two of the above values. The thickness T of the current collector may be 10 μm, 11 μm, 12 μm, 13 μm, 15 μm, or a numerical range formed by any two of the above values. Dv99 / T may be 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or a numerical range formed by any two of the above values.

[0086] In this application, tensile strength refers to the maximum stress value that a material can withstand before breaking. The tensile strength of the current collector in the embodiments of this application can be tested using instruments and methods known in the art. The specific conditions and requirements for the tensile test can be performed in accordance with relevant standards, such as the relevant provisions and requirements in the Chinese National Standard GB / T 228.1—2021 "Metallic Materials - Tensile Testing - Part 1: Test Method at Room Temperature". As an example, the following method can be used for testing: Lay the current collector flat on a horizontal table and cut it into sections, each section being approximately 15 cm in length; turn on the tensile testing machine, pass the current collector through the upper and lower clamps, step on the air valve to clamp the upper clamp first, maintaining a weak connection, and then clamp the lower clamp. The test is performed by pulling both clamps outward until the current collector breaks in the middle. The test is completed, and the stress at which the positive current collector breaks is output as the tensile strength, with a tensile rate of 5 mm / min.

[0087] In some embodiments, the current collector is made of aluminum foil, which comprises aluminum, silicon, and iron. The aluminum content in the aluminum foil is greater than or equal to 99.3% by mass, the silicon content is 0.05% to 0.20% by mass, and the iron content is 0.20% to 0.40% by mass. This appropriate elemental ratio helps improve the tensile strength of the current collector and reduces deformation and breakage under high pressure density conditions of the positive electrode film. For example, the mass percentage of silicon in the aluminum foil can be any two values ​​from 0.05%, 0.1%, 0.15%, 0.2%, or higher. The mass percentage of iron in the aluminum foil can be any two values ​​from 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, or higher. The mass percentage of aluminum in the aluminum foil can be any two values ​​from 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, or higher. Aluminum foil usually also contains unavoidable impurity elements, and the sum of the mass percentages of each element and the impurity elements is 100%.

[0088] In this application, the content of aluminum, silicon, and iron in the aluminum foil can be tested using instruments and methods known in the art. For example, the aluminum foil can be placed in an appropriate amount of concentrated nitric acid solvent for digestion and digested using the plate digestion method. Finally, the solvent is dissolved and extracted with hydrochloric acid, and the resulting solution is brought to an appropriate volume and then quantitatively tested using an inductively coupled plasma optical emission spectrometer (ICP-OES).

[0089] In some embodiments, the elongation at break of the positive electrode sheet is 1.6% to 2.4%. Generally, the higher the elongation at break, the better the ductility of the material, allowing it to undergo plastic deformation under external forces, thereby reducing stress concentration and extending the battery's lifespan. Exemplarily, the elongation at break of the positive electrode sheet can be 1.6%, 1.7%, 1.8%, 1.9%, 1.95%, 2%, 2.05%, 2.1%, 2.15%, 2.2%, 2.25%, 2.3%, 2.35%, 2.4%, or any two of the above values ​​within a range.

[0090] In this application, the elongation at break is the ratio of the increase in length of the material before fracture to the original length. The specific test method for the elongation at break is as follows: take a tensile specimen with an original length of L0, stretch the tensile specimen on a tensile testing machine until fracture, and the length of the tensile specimen before fracture is Lh. Then the elongation at break of the tensile specimen is Δh=(Lh-L0) / L0×100%. The specific conditions and requirements for the tensile test can be carried out with reference to relevant standards, such as the relevant provisions and requirements in the Chinese National Standard GB / T 228.1—2021 "Metallic materials, tensile testing—Part 1: Test method at room temperature".

[0091] In some embodiments, the positive electrode active material layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0092] In some embodiments, the positive electrode active material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0093] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0094] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0095] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0096] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0097] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0098] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0099] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0100] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0101] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0102] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or entirely solid.

[0103] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0104] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0105] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0106] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0107] In some embodiments, the battery cell also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0108] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0109] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0110] Secondly, this application provides a positive electrode sheet, comprising a current collector and a positive active material layer disposed on at least one side of the surface of the current collector; wherein, under the condition that the state of charge (SOC) of the battery cell is 0%, the compaction density of a single-sided film layer of the positive electrode sheet is 3.55–3.80 g / cm³. 3 The volume distribution particle size of the positive electrode active material in the positive electrode active material layer satisfies: Dv99 ≤ 23 μm. Using a high positive electrode compaction density is beneficial for improving the energy density of the battery. Simultaneously, by controlling the Dv99 of the positive electrode active material in the positive electrode active material layer within the aforementioned suitable range, the particle size of larger particles can be controlled, avoiding the current collector being squeezed, deformed, or even damaged by larger positive electrode active material particles under high compaction density conditions, thereby extending the battery's lifespan.

[0111] For example, when the state of charge (SOC) of the battery cell is 0%, the compaction density of the single-sided film layer of the positive electrode can be 3.55 g / cm³. 3 3.6g / cm 3 3.65g / cm 3 3.7g / cm 3 3.75g / cm 3 3.80g / cm 3 Or a range of values ​​consisting of any two of the above values.

[0112] In some embodiments, the positive electrode active material satisfies at least one of the following conditions: (1) the volume distribution particle size of the positive electrode active material satisfies: 18μm≤Dv99≤23μm; (2) the volume distribution particle size of the positive electrode active material satisfies: 4.5μm≤Dv50≤9.5μm; (3) the particle size distribution span (Dv90-Dv10) / Dv50 of the positive electrode active material is 1.23~2.70. Thus, on the one hand, by controlling the particle size distribution of the positive electrode active material, matching positive electrode active material particles of different sizes is achieved, increasing the compaction density of the positive electrode film, thereby improving the energy density of the battery. On the other hand, by controlling the particle size distribution of the positive electrode active material, the current collector is prevented from being squeezed, deformed, or even damaged by larger positive electrode active material particles under high compaction density conditions.

[0113] For example, the volume distribution particle size Dv99 of the positive electrode active material can be any range consisting of two values ​​from 18 μm, 19 μm, 20 μm, 21 μm, 21.5 μm, 22 μm, 22.5 μm, 23 μm, or higher. The volume distribution particle size Dv50 of the positive electrode active material can be any range consisting of two values ​​from 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, or higher. The particle size distribution span (Dv90-Dv10) / Dv50 of the positive electrode active material can be any range consisting of two values ​​from 1.23, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, or higher.

[0114] In some embodiments, the positive electrode active material comprises a lithium-containing transition metal oxide. This material has a high specific capacity, which can improve the energy density of the battery cell.

[0115] In some embodiments, the lithium-containing transition metal oxide includes Li m Ni a Co b Mn c M d The material for O2, M, includes at least one of Zr, Al, Cu, Mg, Zn, Ti, V, Ga, Sn, Ge, B, Ta, Mo, W, Nb, Sb, Sr, and La; wherein a+b+c+d=1, 0.8≤m≤1.2, 0.5≤a<1, 0≤b≤0.5, 0≤c<0.3, and 0≤d<0.2. This material has a high specific capacity and a relatively stable crystal structure, which is beneficial for improving the compaction density of the positive electrode film, thereby increasing the energy density and lifespan of the battery cell.

[0116] In some implementations, m can be a range of values ​​consisting of any two values, such as 0.8, 0.9, 1.0, 1.1, 1.2, or higher.

[0117] In some implementations, 'a' can be a range of values ​​consisting of any two values ​​from 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 0.98, 0.99, or above.

[0118] In some implementations, b can be a range of values ​​consisting of any two values, such as 0, 0.1, 0.2, 0.3, 0.4, 0.5, or higher.

[0119] In some implementations, c can be a range of values ​​consisting of any two values, such as 0, 0.05, 0.1, 0.15, 0.2, 0.25, or more.

[0120] In some implementations, d can be a range of values ​​consisting of any two values, such as 0, 0.05, 0.1, 0.15, or higher.

[0121] In some embodiments, the positive electrode active material includes a first lithium-containing transition metal oxide with a primary particle morphology and a second lithium-containing transition metal oxide with a secondary particle morphology. The particle size matching effect between the positive electrode active material particles with different morphologies is utilized to fully utilize the packing space of the positive electrode active material, thereby increasing the compaction density of the positive electrode film.

[0122] In some embodiments, the mass ratio of the second lithium-containing transition metal oxide to the first lithium-containing transition metal oxide is 6:4 to 8:2. Using this suitable ratio is beneficial for increasing the compaction density of the cathode film. For example, the mass ratio of the second lithium-containing transition metal oxide to the first lithium-containing transition metal oxide can be any range of two values ​​from 6:4, 7:4, 8:4, 6:2, 7:2, 8:2, to 6:2.

[0123] In some embodiments, the first lithium-containing transition metal oxide includes Li m1 Ni a1 Co b1 Mn c1 M d1 The material of O2, M includes at least one of Zr, Al, Cu, Mg, Zn, Ti, V, Ga, Sn, Ge, B, Ta, Mo, W, Nb, Sb, Sr, and La; wherein a1+b1+c1+d1=1, 0.8≤m1≤1.2, 0.8≤a1<1, 0≤b1≤0.2, 0≤c1<0.2, and 0≤d1<0.2; the second lithium-containing transition metal oxide includes Li m2 Ni a2 Co b2 Mn c2 M d2 The material M for O2 includes at least one of Zr, Al, Cu, Mg, Zn, Ti, V, Ga, Sn, Ge, B, Ta, Mo, W, Nb, Sb, Sr, and La; wherein a² + b² + c² + d² = 1, 0.8 ≤ m² ≤ 1.2, 0.8 ≤ a² < 1, 0 ≤ b² ≤ 0.2, 0 ≤ c² < 0.2, and 0 ≤ d² < 0.2. Using the aforementioned high-nickel-content first and second lithium-containing transition metal oxide materials is beneficial for improving the energy density of individual battery cells.

[0124] In some embodiments, the first lithium-containing transition metal oxide and the second lithium-containing transition metal oxide satisfy: the absolute value of the difference between a1 and a2 is less than 0.1. Using the first lithium-containing transition metal oxide material and the second lithium-containing transition metal oxide material with similar nickel contents is beneficial to achieving uniform structure of the positive electrode film layer. Under the condition of high compaction density of the positive electrode film layer, it is beneficial to uniform stress distribution and reduces damage to the current collector.

[0125] In some embodiments, the current collector satisfies at least one of the following conditions: (1) the tensile strength of the current collector is 250 to 330 MPa; (2) the thickness T of the current collector is 10 to 15 μm; (3) the ratio of the volume distribution particle diameter Dv99 of the positive electrode active material in the positive electrode active material layer to the thickness T of the current collector satisfies the following condition: 1 < Dv99 / T < 2. When the tensile strength of the current collector is within a suitable range, it is beneficial to reducing deformation and fracture of the current collector under the condition of high compaction density of the positive electrode film layer. When the thickness of the current collector is within the suitable range, it is beneficial to providing a good bearing effect and preventing the current collector from being broken or damaged by compression under the high compaction density condition. When the ratio of the volume distribution particle diameter Dv99 of the positive electrode active material to the thickness of the current collector is within the above suitable range, it is beneficial to preventing the current collector from being extruded, deformed and even damaged by larger particles of the positive electrode active material under the condition of high compaction density, thereby prolonging the service life of the battery.

[0126] Exemplarily, the tensile strength of the current collector can be 250 MPa, 260 MPa, 270 MPa, 280 MPa, 290 MPa, 300 MPa, 310 MPa, 320 MPa, 330 MPa, or any numerical range formed by any two of the above values. The thickness T of the current collector can be 10 μm, 11 μm, 12 μm, 13 μm, 15 μm, or any numerical range formed by any two of the above values. Dv99 / T can be 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or any numerical range formed by any two of the above values.

[0127] In some embodiments, the current collector is made of aluminum foil, which comprises aluminum, silicon, and iron. The aluminum content in the aluminum foil is greater than or equal to 99.3% by mass, the silicon content is 0.05% to 0.20% by mass, and the iron content is 0.20% to 0.40% by mass. This appropriate elemental ratio helps improve the tensile strength of the current collector and reduces deformation and breakage under high pressure density conditions of the positive electrode film. For example, the mass percentage of silicon in the aluminum foil can be any two values ​​from 0.05%, 0.1%, 0.15%, 0.2%, or higher. The mass percentage of iron in the aluminum foil can be any two values ​​from 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, or higher. The mass percentage of aluminum in the aluminum foil can be any two values ​​from 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, or higher. Aluminum foil usually also contains unavoidable impurity elements, and the sum of the mass percentages of each element and the impurity elements is 100%.

[0128] In some embodiments, the elongation at break of the positive electrode is 1.9% to 2.4%. This is beneficial for extending the battery's lifespan. Exemplarily, the elongation at break of the positive electrode can be any range of two values: 1.9%, 1.95%, 2%, 2.05%, 2.1%, 2.15%, 2.2%, 2.25%, 2.3%, 2.35%, 2.4%, or any two of the above values.

[0129] This application also provides a battery device, including the battery cell provided in this application.

[0130] As the electrical device, a single battery cell, a battery module, or a battery pack can be selected according to its usage requirements.

[0131] Figure 6 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the individual battery cells, a battery pack or battery module can be used.

[0132] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0133] This application also provides an electrical device, including the battery device provided in this application.

[0134] Example

[0135] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0136] Example 1

[0137] 1. Preparation of positive electrode sheet

[0138] The positive electrode consists of a positive current collector and a positive electrode film layer. The positive electrode film layer is disposed on both sides of the positive current collector, which is an aluminum foil with a thickness of 13 μm. The aluminum foil contains aluminum, silicon, iron, and trace elements. Aluminum accounts for 99.5% of the mass of the aluminum foil, silicon accounts for 0.1% by mass, iron accounts for 0.30% by mass, and trace elements include Cu (0.012%), Ti (0.01%), and V (0.01%) by mass, with the remainder being unavoidable impurities. The tensile strength of the aluminum foil is 265 MPa.

[0139] The positive electrode film layer comprises a film layer formed by uniformly coating a positive electrode slurry (solvent being N-methylpyrrolidone NMP) onto the surface of a positive electrode current collector, followed by drying and cold pressing. The positive electrode film layer comprises positive electrode active material, binder polyvinylidene fluoride (PVDF), and conductive agent acetylene black in a weight ratio of 90:5:5.

[0140] Among them, the volume distribution particle size of the positive electrode active material is 20 μm for Dv99, 5.5 μm for Dv50, and the particle size distribution span (Dv90-Dv10) / Dv50 is 2.54.

[0141] The positive electrode active material comprises a first lithium-containing transition metal oxide with a primary particle morphology and a second lithium-containing transition metal oxide with a secondary particle morphology; the mass ratio of the second lithium-containing transition metal oxide to the first lithium-containing transition metal oxide is 7:3. Both the first and second lithium-containing transition metal oxides have the chemical formula LiNi. 0.92 Co 0.05 Mn 0.025 Al 0.005 O2.

[0142] When the state of charge (SOC) of the battery cell is 0%, the compaction density of the single-sided film layer of the positive electrode is 3.7 g / cm³. 3 .

[0143] The elongation at break of the positive electrode is 2.2%.

[0144] 2. Preparation of negative electrode sheet

[0145] The negative electrode sheet includes a negative current collector and a negative electrode film layer. The negative electrode film layer is disposed on both sides of the negative current collector, and the negative current collector is copper foil.

[0146] The active material artificial graphite, conductive agent carbon black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are dissolved in deionized water at a weight ratio of 90:8:0.8:1.2 and mixed evenly to prepare a negative electrode slurry. The negative electrode slurry is uniformly coated onto the negative electrode current collector copper foil once or multiple times, and then dried, cold-pressed, and slit to obtain the negative electrode sheet.

[0147] 3. Preparation of electrolyte:

[0148] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1 were mixed, and then 5% fluoroethylene carbonate (FEC) was added to obtain an organic solvent. LiPF6 lithium salt was added and dissolved in the organic solvent, and the mixture was stirred evenly to obtain an electrolyte with a lithium salt concentration of 1 mol / L.

[0149] 4. Preparation of lithium-ion batteries:

[0150] The positive electrode, polypropylene separator, and negative electrode are stacked in sequence, with the polypropylene separator acting as a separator between the positive and negative electrodes. They are then wound to obtain a bare cell. Tabs are welded onto the bare cell, which is then placed in an aluminum casing and baked at 80°C to remove moisture. Electrolyte is then injected and the casing is sealed, resulting in a non-charged battery. This non-charged battery then undergoes a series of processes including settling, hot and cold pressing, formation, shaping, and capacity testing to obtain the lithium-ion battery product.

[0151] The parameters of Examples 1 to 10 and Comparative Examples 1 to 2 of this application are as shown in Tables 1 and 2.

[0152] Performance testing:

[0153] The batteries from Examples 1 to 11 and Comparative Examples 1-2 were subjected to the following tests:

[0154] (1) Test of elongation at break of positive electrode sheet:

[0155] A positive electrode sheet tensile specimen with an initial length of L0 is taken. The preload force of the tensile testing machine is 1N, and the tensile rate is 5mm / min. The tensile specimen is stretched on the tensile testing machine until it breaks. The length of the tensile specimen before fracture is Lh. Then the elongation at break of the tensile specimen is Δh=(Lh-L0) / L0×100%.

[0156] (1) Energy density test:

[0157] At 25℃, the battery is charged at a constant current and constant voltage of 0.33C to the designed upper limit voltage of 4.17V, with a cutoff current of 0.05C. After standing for 30 minutes, it is discharged at 0.33C to the designed lower limit voltage of 2.8V. The discharge energy P (Wh) and the cell weight m (kg) are recorded. Then the energy density (Wh / kg) = P / m.

[0158] (2) Cyclic performance test:

[0159] At 25°C, charge each battery cell at a constant current of 1C to the charging cutoff voltage of 4.17V, then charge at a constant current of 0.05C to the charging cutoff voltage of 4.17V, and let it rest for 30 minutes; then discharge at a constant current of 1C to 2.8V, and let it rest for 30 minutes. This constitutes one charge-discharge cycle. Repeat the above charge-discharge cycle steps until the cycle capacity retention rate (i.e., Cn / C0×100%) is 80%, and record the number of cycles.

[0160] Table 2. Parameters of the current collector

[0161] Table 3 Battery performance parameters

[0162] As can be seen from the results in Table 1-3, in Comparative Example 1, although the lower compaction density of the positive electrode sheet resulted in less damage to the positive electrode sheet and good elongation at break, the energy density of the battery decreased excessively. In Comparative Example 2, the positive electrode active material DV99 used was relatively large, resulting in a lower elongation at break of the positive electrode sheet, which could not balance the cycle performance of the battery.

[0163] In Examples 1-10 of this application, the compaction density of a single-sided film layer of the positive electrode sheet is 3.55–3.80 g / cm³. 3 Under high energy density conditions, by adjusting the positive electrode active material DV99≤23μm, high energy density is achieved while also ensuring high elongation at break of the positive electrode sheet, thus ensuring good cycle performance of the battery and extending its service life.

[0164] As can be seen from Examples 1, 6, and 7, using a combination of a first lithium-containing transition metal oxide and a second lithium-containing transition metal oxide, i.e., using a combination of primary and secondary particles, is beneficial to further fully utilize the stacking space of the positive electrode active material, increase the compaction density, and the combination of primary and secondary particles is beneficial to uniform stress dispersion, thereby further improving the elongation at break of the positive electrode sheet and improving the cycle performance of the battery.

[0165] As can be seen from Examples 1 and 8-10, adjusting the iron content in the current collector and adjusting the thickness of the current collector are beneficial to further improving the battery cycle performance.

[0166] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, characterized in that, It includes a positive electrode sheet, wherein the positive electrode sheet includes a current collector and a positive active material layer disposed on at least one side of the surface of the current collector; Wherein, under the condition that the state of charge (SOC) of the battery cell is 0%, the compaction density of the single-sided film layer of the positive electrode sheet is 3.55–3.80 g / cm³. 3 The volume distribution particle size of the positive electrode active material in the positive electrode active material layer satisfies: Dv99≤23μm.

2. The battery cell according to claim 1, characterized in that, The positive electrode active material satisfies at least one of the following conditions: (1) The volume distribution particle size of the positive electrode active material satisfies: 18μm≤Dv99≤23μm; (2) The volume distribution particle size of the positive electrode active material satisfies: 4.5m≤Dv50≤9.5μm; (3) The particle size distribution range (Dv90-Dv10) / Dv50 of the positive electrode active material is 1.23 to 2.

70.

3. The battery cell according to claim 1, characterized in that, The positive electrode active material includes lithium-containing transition metal oxides.

4. The battery cell according to claim 3, characterized in that, The lithium-containing transition metal oxide includes Li m Ni a Co b Mn c M d The material of O2, M includes at least one of Zr, Al, Cu, Mg, Zn, Ti, V, Ga, Sn, Ge, B, Ta, Mo, W, Nb, Sb, Sr, and La; wherein a+b+c+d=1, 0.8≤m≤1.2, 0.5≤a<1, 0≤b≤0.5, 0≤c<0.3, and 0≤d<0.

2.

5. The battery cell according to any one of claims 1 to 4, characterized in that, The positive electrode active material includes a first lithium-containing transition metal oxide with a primary particle morphology and a second lithium-containing transition metal oxide with a secondary particle morphology.

6. The battery cell according to claim 5, characterized in that, The mass ratio of the second lithium-containing transition metal oxide to the first lithium-containing transition metal oxide is 6:4 to 8:

2.

7. The battery cell according to claim 5, characterized in that, The first lithium-containing transition metal oxide includes Li m1 Ni a1 Co b1 Mn c1 M d1 The material of O2, M includes at least one of Zr, Al, Cu, Mg, Zn, Ti, V, Ga, Sn, Ge, B, Ta, Mo, W, Nb, Sb, Sr, and La; wherein a1+b1+c1+d1=1, 0.8≤m1≤1.2, 0.8≤a1<1, 0≤b1≤0.2, 0≤c1<0.2, 0≤d1<0.2; and / or, The second lithium-containing transition metal oxide includes Li m2 Ni a2 Co b2 Mn c2 M d2 The material of O2, M includes at least one of Zr, Al, Cu, Mg, Zn, Ti, V, Ga, Sn, Ge, B, Ta, Mo, W, Nb, Sb, Sr, and La; wherein a² + b² + c² + d² = 1, 0.8 ≤ m² ≤ 1.2, 0.8 ≤ a² < 1, 0 ≤ b² ≤ 0.2, 0 ≤ c² < 0.2, and 0 ≤ d² < 0.

2.

8. The battery cell according to claim 7, characterized in that, The first lithium-containing transition metal oxide and the second lithium-containing transition metal oxide satisfy the following condition: the absolute value of the difference between a1 and a2 is less than 0.

1.

9. The battery cell according to any one of claims 1 to 4, characterized in that, The current collector satisfies at least one of the following conditions: (1) The tensile strength of the current collector is 250-330 MPa; (2) The thickness T of the current collector is 10-15 μm; (3) The ratio between the volume distribution particle size Dv99 of the positive electrode active material in the positive electrode active material layer and the thickness T of the current collector satisfies the following condition: 1 <Dv99 / T<2。 10. The battery cell according to any one of claims 1 to 4, characterized in that, The current collector is made of aluminum foil, which contains aluminum, silicon and iron. The aluminum content in the aluminum foil is greater than or equal to 99.3% by mass, the silicon content in the aluminum foil is 0.05% to 0.20% by mass, and the iron content in the aluminum foil is 0.20% to 0.40% by mass.

11. The battery cell according to any one of claims 1 to 4, characterized in that, The elongation at break of the positive electrode sheet is 1.6% to 2.4%.

12. A positive electrode plate, characterized in that, Includes a current collector and a positive electrode active material layer disposed on at least one side of the surface of the current collector; Wherein, under the condition that the state of charge (SOC) of the battery cell is 0%, the compaction density of the single-sided film layer of the positive electrode sheet is 3.55–3.80 g / cm³. 3 The volume distribution particle size of the positive electrode active material in the positive electrode active material layer satisfies: Dv99≤23um.

13. The positive electrode sheet according to claim 12, characterized in that, The positive electrode active material satisfies at least one of the following conditions: (1) The volume distribution particle size of the positive electrode active material satisfies: 18μm≤Dv99≤23μm; (2) The volume distribution particle size of the positive electrode active material satisfies: 4.5μm≤Dv50≤9.5μm; (3) The particle size distribution range (Dv90-Dv10) / Dv50 of the positive electrode active material is 1.23 to 2.

70.

14. The positive electrode sheet according to claim 12, characterized in that, The positive electrode active material includes lithium-containing transition metal oxides.

15. The positive electrode sheet according to claim 14, characterized in that, The lithium-containing transition metal oxide includes Li m Ni a Co b Mn c M d The material of O2, M includes at least one of Zr, Al, Cu, Mg, Zn, Ti, V, Ga, Sn, Ge, B, Ta, Mo, W, Nb, Sb, Sr, and La; wherein a+b+c+d=1, 0.8≤m≤1.2, 0.5≤a<1, 0≤b≤0.5, 0≤c<0.3, and 0≤d<0.

2.

16. The positive electrode sheet according to any one of claims 12 to 15, characterized in that, The positive electrode active material includes a first lithium-containing transition metal oxide with a primary particle morphology and a second lithium-containing transition metal oxide with a secondary particle morphology.

17. The positive electrode sheet according to claim 16, characterized in that, The mass ratio of the second lithium-containing transition metal oxide to the first lithium-containing transition metal oxide is 6:4 to 8:

2.

18. The positive electrode sheet according to claim 16, characterized in that, The first lithium-containing transition metal oxide includes Li m1 Ni a1 Co b1 Mn c1 M d1 The material of O2, M includes at least one of Zr, Al, Cu, Mg, Zn, Ti, V, Ga, Sn, Ge, B, Ta, Mo, W, Nb, Sb, Sr, and La; wherein a1+b1+c1+d1=1, 0.8≤m1≤1.2, 0.8≤a1<1, 0≤b1≤0.2, 0≤c1<0.2, 0≤d1<0.2; and / or, The second lithium-containing transition metal oxide includes Li m2 Ni a2 Co b2 Mn c2 M d2 The material of O2, M includes at least one of Zr, Al, Cu, Mg, Zn, Ti, V, Ga, Sn, Ge, B, Ta, Mo, W, Nb, Sb, Sr, and La; wherein a² + b² + c² + d² = 1, 0.8 ≤ m² ≤ 1.2, 0.8 ≤ a² < 1, 0 ≤ b² ≤ 0.2, 0 ≤ c² < 0.2, and 0 ≤ d² < 0.

2.

19. The positive electrode sheet according to claim 18, characterized in that, The first lithium-containing transition metal oxide and the second lithium-containing transition metal oxide satisfy the following condition: the absolute value of the difference between a1 and a2 is less than 0.

1.

20. The positive electrode sheet according to any one of claims 12 to 15, characterized in that, The current collector satisfies at least one of the following conditions: (1) The tensile strength of the current collector is 250-330 MPa; (2) The thickness T of the current collector is 10-15 μm; (3) The ratio between the volume distribution particle size Dv99 of the positive electrode active material in the positive electrode active material layer and the thickness T of the current collector satisfies the following condition: 1 <Dv99 / T<2。 21. The positive electrode sheet according to any one of claims 12 to 15, characterized in that, The current collector is made of aluminum foil, which contains aluminum, silicon and iron. The aluminum content in the aluminum foil is greater than or equal to 99.3% by mass, the silicon content in the aluminum foil is 0.05% to 0.20% by mass, and the iron content in the aluminum foil is 0.20% to 0.40% by mass.

22. The positive electrode sheet according to any one of claims 12 to 15, characterized in that, The elongation at break of the positive electrode sheet is 1.6% to 2.4%.

23. An electrical appliance, characterized in that, Includes the battery cell as described in any one of claims 1 to 11.

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