Positive electrode active material, positive electrode sheet, battery cell, battery, and power using device

Abstract

Provided are a positive electrode active material, a positive electrode sheet, a battery monomer (10), a battery (400), and an electric device, belonging to the technical field of secondary batteries. The positive electrode active material comprises a lithium-rich manganese-based material and a lithium-containing phosphate, the lithium-rich manganese-based material comprises solid particles and hollow particles, and the hollow particles comprise a shell and a cavity arranged on the inner side of the shell. The rate performance and the volumetric energy density of the battery monomer can be considered.

Description

Positive electrode active material, positive electrode sheet, battery cell, battery and electrical device Technical Field

[0001] This application relates to the field of secondary battery technology, and in particular to a positive electrode active material, a positive electrode sheet, a battery cell, a battery, and an electrical device. Background Technology

[0002] In recent years, secondary 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.

[0003] As a component of batteries, the positive electrode active material is crucial to battery performance. Therefore, how to provide a positive electrode active material that balances the volumetric energy density and rate performance of battery cells is a pressing technical problem that needs to be solved. Summary of the Invention

[0004] This application is made in view of the above-mentioned technical problems, and aims to provide a positive electrode active material that balances the volumetric energy density and rate performance of a single battery cell.

[0005] To achieve the above objectives, this application provides a positive electrode active material, a positive electrode sheet, a battery cell, a battery, and an electrical device.

[0006] In a first aspect, a positive electrode active material is provided, comprising a lithium-rich manganese-based material and a lithium-containing phosphate, wherein the lithium-rich manganese-based material comprises solid particles and hollow particles, and the hollow particles comprise a shell and a cavity disposed inside the shell.

[0007] In the embodiments of this application, the positive electrode active material includes a lithium-rich manganese-based material and a lithium-containing phosphate. The synergy between the lithium-rich manganese-based material and the lithium-containing phosphate improves the cycle performance of the battery cell. The lithium-rich manganese-based material includes solid particles and hollow particles. This synergy increases the contact area between the electrolyte and the lithium-rich manganese-based material in the battery cell, facilitating lithium-ion transport and thus improving the rate performance of the battery cell. Furthermore, it increases the compaction density of the positive electrode sheet, thereby increasing the volumetric energy density of the battery cell. Therefore, the embodiments of this application can balance both the volumetric energy density and rate performance of the battery cell.

[0008] In some embodiments, in the lithium-rich manganese-based material, the ratio of the mass A of the solid particles to the mass B of the hollow particles is 1:1 ≤ A:B ≤ 9:1; optionally, 7:3 ≤ A:B ≤ 8:2; and / or, in the lithium-rich manganese-based material, the ratio of the number E of the solid particles to the number F of the hollow particles is 70:30 ≤ E:F ≤ 96:4; optionally, 85:15 ≤ E:F ≤ 90:10.

[0009] In the above technical solution, the mass ratio of solid particles to hollow particles in the lithium-rich manganese-based material satisfies 1:1 ≤ A:B ≤ 9:1, and / or, the ratio of the number of solid particles E to the number of hollow particles F is 70:30 ≤ E:F ≤ 96:4. This provides a suitable contact area between the lithium-rich manganese-based material and the electrolyte, which is beneficial for lithium-ion transport and thus improves the rate performance of the battery cell. Simultaneously, the lithium-rich manganese-based material has a suitable volume, which helps increase the compaction density of the positive electrode sheet and improves the volumetric energy density of the battery cell. Optionally, 7:3 ≤ A:B ≤ 8:2, which helps to balance the rate performance and volumetric energy density of the battery cell. Optionally, 85:15 ≤ E:F ≤ 90:10, which further helps to balance the rate performance and volumetric energy density of the battery cell.

[0010] In some embodiments, the volume average particle size D of the solid particles V 50 is 2μm to 8μm; optionally, it is 3μm to 6μm.

[0011] In the above technical solution, the volume average particle size D of the solid particles V The particle size is 2μm to 8μm. This has two advantages: firstly, solid particles have a suitable specific surface area, which is beneficial for increasing the contact area between the electrolyte and the solid particles in the lithium-rich manganese-based material, facilitating the transport of more lithium ions per unit time, and improving the rate performance of the battery cell; secondly, solid particles have a suitable volume, which is beneficial for increasing the compaction density of the positive electrode sheet, thereby improving the volumetric energy density of the battery cell. Optionally, the volume average particle size D of the solid particles... V The thickness of the 50 is 3μm to 6μm, which is beneficial to further improve the rate performance and volumetric energy density of the battery cells.

[0012] In some embodiments, the volume average particle size D of the hollow particles V 50 is 5μm to 15μm; optionally, it is 7μm to 12μm.

[0013] In the above technical solution, the volume average particle size D of the hollow particles VThe particle size is 5μm to 15μm. On one hand, hollow particles have a suitable specific surface area, which is beneficial for increasing the contact area between the electrolyte and the lithium-rich manganese-based material, thus facilitating the transport of more lithium ions per unit time and improving the rate performance of the battery cell. On the other hand, the volume occupied by hollow particles is relatively suitable, which is beneficial for increasing the volumetric energy density of the battery cell. Optionally, the volume average particle size D of the hollow particles... V The thickness of 50 is 7μm to 12μm, which is beneficial for balancing the rate performance and volumetric energy density of the battery cells.

[0014] In some embodiments, the volume average particle size D of the hollow particles V 50 is greater than the volume average particle size D of the solid particles. V 50; Optionally, the volume average particle size D of the hollow particles V 50 and the volume average particle size D of the solid particles v The difference between the number of hollow particles and the number of solid particles is 3 μm to 10 μm; further optionally, the difference is 4 μm to 8 μm; and / or, the number-average particle size of the hollow particles is greater than the number-average particle size of the solid particles; optionally, the difference between the number-average particle size of the hollow particles and the number-average particle size of the solid particles is 3 μm to 10 μm; further optionally, the difference is 4 μm to 8 μm.

[0015] In the above technical solution, the volume average particle size D of the hollow particles V 50 is greater than the volume average particle size D of solid particles V 50; and / or, the number average particle size of the hollow particles is larger than that of the solid particles, so that the solid particles can fill the gaps between the hollow particles, which is beneficial to increasing the compaction density of the positive electrode sheet, thereby improving the energy density of the battery cell. Optionally, the volume average particle size D of the hollow particles... V 50 and the volume average particle size D of solid particles V The difference between the number average particle size and the number average particle size of the hollow particles is 3μm to 10μm or, more preferably, 4μm to 8μm; and / or, the difference between the number average particle size of the hollow particles and the number average particle size of the solid particles is 3μm to 10μm or, more preferably, 4μm to 8μm, which is beneficial to achieve a reasonable combination of solid and hollow particles, better fill the gaps between hollow particles, thereby improving the compaction density of the positive electrode sheet and increasing the energy density of the battery cell.

[0016] In some embodiments, the cavity size of the hollow particle is 2μm to 10μm; optionally, it is 4μm to 7μm.

[0017] In the above technical solution, the cavity size of the hollow particles is 2μm to 10μm. On the one hand, the hollow particles have a suitable specific surface area, which is beneficial for transporting more lithium ions per unit time and improving the rate performance of the battery cell; on the other hand, the volume occupied by the hollow particles is suitable, which is beneficial for improving the volumetric energy density of the battery cell. Optionally, the cavity size of the hollow particles is 4μm to 7μm, which is beneficial for balancing the rate performance and volumetric energy density of the battery cell.

[0018] In some embodiments, the volume average particle size D of the lithium phosphate is... V 50 is 0.3μm to 1.5μm; optionally, it is 0.6μm to 1.2μm.

[0019] In the above technical solution, by setting the volume average particle size of the lithium phosphate in the positive electrode active material to no more than 1.5 μm, it is beneficial to reduce the volume of the lithium phosphate and improve the volumetric energy density of the battery cell; the volume average particle size of the lithium phosphate to no less than 0.3 μm is beneficial to maintain a suitable contact area between the lithium phosphate and the electrolyte, thereby improving the rate performance of the battery cell. Optionally, the volume average particle size D of the lithium phosphate... V The thickness of 50 is 0.6μm to 1.2μm, which is beneficial for further balancing the rate performance and volumetric energy density of the battery cells.

[0020] In some embodiments, the mass percentage of the lithium-rich manganese-based material is P, based on the total mass of the positive electrode active material, where 10wt% ≤ P < 100wt%, and optionally, 30wt% ≤ P ≤ 70wt%.

[0021] In the above technical solution, by reasonably setting the mass ratio of lithium-rich manganese-based materials in the positive electrode active material, it is beneficial to balance the volumetric energy density and rate performance of the battery cell.

[0022] In some embodiments, the specific capacity of the lithium-rich manganese-based material is Q≥153mAh / g; optionally, Q≥158mAh / g.

[0023] In the above technical solution, the specific capacity Q of the lithium-rich manganese-based material is ≥153 mAh / g, which is beneficial to improving the energy density of the battery cell. Optionally, Q ≥158 mAh / g is beneficial to further improve the energy density of the battery cell.

[0024] In some embodiments, the general formula of the lithium-rich manganese-based material is nLi₂MnO₃·(1-n)Li 1+ x1 Ni x2 Mn x3 M 1 x4O2, where 0.1≤n≤0.3, 0≤x1≤0.1, 0.3≤x2<1, 0<x3≤0.7, 0≤x4≤0.1, M 1 It includes one or more of Na, Mg, Al, Ca, Ba, V, Zn, Ti, Fe, Co, Cr, Nb, W, Mo, Zr, Ta, and Hf. This allows for flexible selection of lithium-rich manganese-based materials according to actual needs.

[0025] In some embodiments, the lithium phosphate has the general formula Li 1+y1 Fe y2 Mn y3 M 2 y4 PO4, where 0≤y1≤0.1, 0≤y2≤1, 0≤y3≤1, 0≤y4≤0.1, M 2 This includes one or more transition metal elements other than Fe and Mn, as well as non-transition metal elements. This allows for flexible selection of lithium-containing phosphates based on actual needs.

[0026] In a second aspect, a positive electrode sheet is provided, comprising the positive electrode active material of the first aspect and any possible implementation thereof.

[0027] In one possible implementation, the compaction density of the positive electrode sheet is 2.70 g / cm³. 3 ~2.90g / cm 3 Optionally, it is 2.75 g / cm³. 3 ~2.85g / cm 3 In this way, the battery cell has a high volumetric energy density.

[0028] Thirdly, a battery cell is provided, the battery cell including the positive electrode sheet of the second aspect and any possible implementation thereof.

[0029] Fourthly, a battery is provided, the battery comprising the battery cell described in the third aspect.

[0030] Fifthly, an electrical device is provided, the electrical device comprising the battery described in the fourth aspect.

[0031] In the embodiments of this application, the positive electrode active material includes a lithium-rich manganese-based material and a lithium-containing phosphate. The synergy between the lithium-rich manganese-based material and the lithium-containing phosphate improves the cycle performance of the battery cell. The lithium-rich manganese-based material includes solid particles and hollow particles. This synergy increases the contact area between the electrolyte and the lithium-rich manganese-based material in the battery cell, facilitating lithium-ion transport and thus improving the rate performance of the battery cell. Furthermore, it increases the compaction density of the positive electrode sheet, thereby increasing the volumetric energy density of the battery cell. Therefore, the embodiments of this application can balance both the volumetric energy density and rate performance of the battery cell. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort. In the drawings, the drawings are not drawn to scale.

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

[0034] Figure 2 is a schematic diagram of the exploded structure of a battery cell according to an embodiment of this application.

[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 according to an embodiment of this application.

[0037] Figure 5 is a schematic diagram of the exploded structure of a battery according to an embodiment of this application.

[0038] Figure 6 is a schematic diagram of an electrical device according to an embodiment of this application. Detailed Implementation

[0039] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the positive electrode active material, positive electrode sheet, battery cell, battery, and power device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0040] In the description of this application, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," etc., indicating orientation or positional relationships are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[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 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.

[0043] 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.

[0044] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0045] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0046] In recent years, power batteries have seen significant development due to their high energy density and long lifespan, finding widespread application in power tools, electronic products, electric vehicles, aerospace, and other fields. Typically, a power battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, prevents short circuits while allowing ions to pass through, ensuring the normal electrochemical reaction of the power battery.

[0047] This application takes a lithium-ion battery as an example. A lithium-ion battery is a typical power battery. Because it relies on the chemical reaction of lithium ions being inserted and extracted between the positive and negative electrodes for charging and discharging, it is also known as a rocking chair battery. During the charging process of a lithium-ion battery, lithium ions are extracted from the positive electrode, move through the electrolyte, and are inserted into the active material of the negative electrode; while during the discharging process, lithium ions are extracted from the negative electrode, move through the electrolyte, and are inserted into the active material of the positive electrode.

[0048] It should be understood that the “lithium intercalation” or “intercalation” process described in this application refers to the process in which lithium ions are intercalated into the positive electrode active material or the negative electrode active material due to an electrochemical reaction, while the “de-lithium extraction”, “de-lithium extraction”, or “de-intercalation” process described in this application refers to the process in which lithium ions are extracted from the positive electrode active material or the negative electrode active material due to an electrochemical reaction.

[0049] The positive electrode active materials for lithium-ion batteries typically use lithium-containing transition metal oxides and compounds, such as lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, ternary materials, and lithium-rich manganese-based materials. Among these, lithium-rich manganese-based materials, which primarily use inexpensive manganese, have lower material costs and higher specific capacity, thus improving the energy density of lithium-ion batteries. However, as the charge and discharge process progresses, the structure of lithium-rich manganese-based materials changes, leading to poorer cycle performance and other characteristics of the battery.

[0050] In some processing methods, positive electrode active materials are prepared by mixing lithium-containing phosphates (such as lithium iron phosphate) with lithium-rich manganese-based materials to improve the cycle performance of the battery. However, batteries obtained by this processing method have poor rate performance.

[0051] Therefore, this application provides a positive electrode active material, including a lithium-rich manganese-based material and a lithium-containing phosphate. The lithium-rich manganese-based material includes solid particles and hollow particles. The combination of solid and hollow particles increases the contact area between the lithium-rich manganese-based material and the electrolyte, thereby facilitating lithium-ion transport and improving the rate performance of the battery cell.

[0052] [Positive electrode active material]

[0053] This application provides a positive electrode active material, including a lithium-rich manganese-based material and a lithium-containing phosphate.

[0054] Lithium-rich manganese-based materials include both solid and hollow particles.

[0055] Hollow particles consist of a shell and a cavity disposed inside the shell. In other words, hollow particles can be understood as particles with cavities disposed inside.

[0056] Solid particles can be understood as particles without internal cavities. When solid particles and hollow particles have the same particle size, hollow particles have a larger specific surface area; when solid particles and hollow particles have the same mass, hollow particles have a larger surface area.

[0057] Lithium-rich manganese-based materials have high specific capacity, and lithium phosphate-containing materials have relatively stable structures. Both lithium-rich manganese-based materials and lithium phosphate-containing cathode active materials have suitable specific capacity and stability. When cathode active materials are used to prepare battery cells, the resulting battery cells can have high energy density and better cycle performance.

[0058] Compared to lithium-rich manganese-based materials, which are all solid particles, the lithium-rich manganese-based material in this application includes both solid and hollow particles, thus having a larger specific surface area. This results in a larger contact area between the lithium-rich manganese-based material and the electrolyte in the battery cell, which is beneficial for lithium-ion transport and thus helps improve the rate performance of the battery cell.

[0059] The rate performance of a single battery cell is related to lithium-ion transport. Generally speaking, the more lithium-ions transported per unit time, the better the rate performance of the battery cell.

[0060] Furthermore, compared to lithium-rich manganese-based materials which are all hollow particles, the lithium-rich manganese-based materials in this application include both solid and hollow particles, which helps to reduce the space occupied by the positive electrode active material, thereby helping to improve the volumetric energy density of the battery cell.

[0061] The shapes of the solid and hollow particles in this application embodiment may include: spherical, near-spherical (e.g., ellipsoidal), irregular, and other shapes.

[0062] In the embodiments of this application, the positive electrode active material includes lithium-rich manganese-based material and lithium phosphate, which is beneficial to improving the cycle performance of the battery cell; the lithium-rich manganese-based material includes solid particles and hollow particles. The combination of solid particles and hollow particles is beneficial to improving the rate performance of the battery cell while having a high energy density, thereby helping to balance the volumetric energy density and rate performance of the battery cell.

[0063] In some embodiments, in the lithium-rich manganese-based material, the ratio of the mass A of solid particles to the mass B of hollow particles is 1:1 ≤ A:B ≤ 9:1, for example, A:B is a range consisting of 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, and any of the above values; and / or, in the lithium-rich manganese-based material, the ratio of the number E of hollow particles to the number F of solid particles is 70:30 ≤ E:F ≤ 96:4, for example, E:F is a range consisting of 7:3, 5:1, 10:1, 13:1, 24:1, and any of the above values.

[0064] The mass A of the solid particles and the mass B of the hollow particles can be obtained by weighing. For example, in the preparation of positive electrode active materials, lithium-rich manganese-based materials and lithium-containing phosphates are mixed to obtain the positive electrode active materials. The lithium-rich manganese-based materials are obtained by mixing solid lithium-rich manganese-based materials with hollow lithium-rich manganese-based materials. In the preparation of lithium-rich manganese-based materials, a certain mass of hollow particles and a certain mass of solid particles can be weighed separately (e.g., using a balance) to obtain the masses of the hollow and solid particles, and then the hollow and solid particles are mixed.

[0065] Alternatively, the positive electrode sheet can be cut to obtain cross-sections of solid and hollow particles. The volume ratio of the solid and hollow particles is calculated using the diameter of the cross-sections, and then the mass ratio is calculated using the volume ratio and the average density of the two particles.

[0066] The ratio E:F of the number of solid particles (E) to the number of hollow particles (F) can be calculated based on the ratio A:B between the mass of solid particles (A) and the mass of hollow particles (B), as well as the particle size or volume and average density of the solid and hollow particles. Alternatively, the ratio of solid to hollow particles can be obtained by cutting the positive electrode sheet to obtain a cross-section, and then observing the cross-section using a scanning electron microscope or other methods.

[0067] When the ratio of A to B is not less than 1:1, the battery cell can have a high volumetric energy density; when the ratio of A to B is not greater than 9:1, the lithium-rich manganese-based material and the electrolyte have a suitable contact area, which is conducive to the transport of lithium ions, thereby improving the rate performance of the battery cell.

[0068] Optionally, 7:3 ≤ A:B ≤ 8:2, for example, A:B can be 7:3, 3:1, 8:2, or any of the above values. This helps to further balance the rate performance and volumetric energy density of individual battery cells.

[0069] Optionally, 85:15 ≤ E:F ≤ 90:10, for example, E:F can be 85:15, 7:1, 9:1, or any of the above values. This helps to further balance the rate performance and volumetric energy density of individual battery cells.

[0070] In some embodiments, the volume average particle size D of the solid particles V 50 is 2μm to 8μm; optionally, it is 3μm to 6μm. For example, the volume average particle size D of solid particles. V 50 represents 2μm, 3μm, 4μm, 5.5μm, 6μm, 8μm, or any other value within the above range.

[0071] D V 50 can refer to the particle size corresponding to particles whose cumulative volumetric particle size distribution percentage reaches 50%.

[0072] Volume average particle size D of solid particles V 50 and the volume average particle size D of hollow particles V The particle size can be measured using a laser particle size analyzer. For example, the powder particles are first dispersed in an appropriate amount of solvent to form a dispersion; then the dispersion is placed in a laser particle size analyzer to measure the particle size. Optionally, the powder particles can be lithium-rich manganese-based material powder from the preparation process, or powder obtained through an electrode (e.g., powder of positive electrode active material obtained from a positive electrode by removing binders and other substances using a specific method).

[0073] The volume average particle size D of solid particles VWith a particle size of not less than 2 μm, solid particles possess a suitable specific surface area, which is beneficial for increasing the contact area between the electrolyte and the solid particles, facilitating the transport of more lithium ions per unit time, and improving the rate performance of the battery cell; when the volume average particle size D of the solid particles is... V When the particle size is no greater than 8μm, solid particles have a suitable volume, which is beneficial to improving the compaction density of the positive electrode sheet and thus improving the volumetric energy density of the battery cell.

[0074] Optionally, the volume average particle size D of the solid particles V The thickness of 50 is 3μm to 6μm, which is beneficial for balancing the rate performance and volumetric energy density of battery cells.

[0075] In some embodiments, the volume average particle size D of the hollow particles V 50 represents a particle size ranging from 5 μm to 15 μm. For example, the volume average particle size D of hollow particles... V 50 can be 5μm, 6μm, 7μm, 8μm, 10μm, 12μm, 13μm, 15μm or any other value within the above range.

[0076] The volume average particle size D of hollow particles V With a particle size of not less than 5 μm, hollow particles possess a suitable specific surface area, which is beneficial for increasing the contact area between the electrolyte and the hollow particles, facilitating the transport of more lithium ions per unit time, and improving the rate performance of the battery cell; when the volume average particle size D of the hollow particles is... V When the particle size is no greater than 15μm, it is beneficial to reduce the volume occupied by hollow particles, thereby improving the energy density of the battery cell.

[0077] Optionally, the volume average particle size D of the hollow particles V The thickness of 50 is 7μm to 12μm, which is beneficial for balancing the rate performance and volumetric energy density of the battery cells.

[0078] In some embodiments, the volume average particle size D of the hollow particles V 50 is greater than the volume average particle size D of solid particles V 50; and / or, the number average particle size of hollow particles is greater than that of solid particles.

[0079] Number-average particle size can refer to the particle size corresponding to the cumulative number of particles that account for 50% of the total particle size distribution.

[0080] Alternatively, the number-average particle size can be measured using the same testing method as the volume-average particle size. For example, it can be obtained by laser particle size analyzer.

[0081] Optionally, the number-average particle size can be measured indirectly or directly in the following ways: By cutting the positive electrode sheet to obtain a cross-section, and observing the cross-section using a scanning electron microscope; or by measuring the number and size (particle size) of hollow and solid particles in a specific region or the entire region to determine the average size (particle size) of the hollow and solid particles.

[0082] In this embodiment, solid particles have a smaller volume compared to hollow particles. Solid particles can fill the gaps between hollow particles, which helps to increase the compaction density of the positive electrode sheet and thus improve the energy density of the battery cell.

[0083] Optionally, the volume average particle size D of the hollow particles V 50 and the volume average particle size D of solid particles V The difference between the number average particle size and the number average particle size of the hollow particles is 3μm to 10μm; and / or, the difference between the number average particle size and the number average particle size of the solid particles is 3μm to 10μm, for example, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm or other values ​​within the above range. In this way, the solid particles can better fill the gaps between the hollow particles, which is beneficial for further improving the compaction density of the positive electrode sheet and the energy density of the battery cell.

[0084] Optionally, the volume average particle size D of the hollow particles V 50 and the volume average particle size D of solid particles V The difference between the number average particle size and the number average particle size of the hollow particles is 4μm to 8μm; and / or, the difference between the number average particle size of the hollow particles and the number average particle size of the solid particles is 4μm to 8μm. This allows the solid particles to better fill the gaps between the hollow particles, achieving a reasonable combination of larger-diameter hollow particles and smaller-diameter solid particles, thereby improving the compaction density of the positive electrode sheet and the energy density of the battery cell.

[0085] In some embodiments, the cavity size of the hollow particle is 2 μm to 10 μm. For example, the cavity size of the hollow particle is 2 μm, 3 μm, 4 μm, 6 μm, 7 μm, 9 μm, 10 μm or any other value within the above range.

[0086] Hollow particles can include particles of various shapes. For example, hollow particles can be spherical or ellipsoidal.

[0087] For a spherical hollow particle, the size of the cavity can be understood as the inner diameter of the hollow particle. The hollow particle has a shell and a cavity inside the shell. The diameter of the shell is the outer diameter of the hollow particle, and the size of the cavity inside the shell is the inner diameter of the hollow particle.

[0088] For ellipsoidal hollow particles, the size of the cavity can be understood as the average of the maximum and minimum dimensions of the cavity. For example, if the cross-section of an ellipsoidal hollow particle is an ellipse, then the size of the cavity is the average of the dimensions of the major and minor axes of the ellipse.

[0089] For other irregular hollow particles, the size of the cavity can be understood as the average of the maximum and minimum dimensions of the cavity.

[0090] The following explanation uses a spherical hollow particle as an example to illustrate the measurement of the cavity size of a hollow particle. The cavity size of a hollow particle can be measured using the following method: The hollow particle is cut using an argon ion beam polisher to obtain a cross-section; multiple images of this cross-section are obtained at the same magnification using a scanning electron microscope; the inner diameters of the particle cross-sections in the images are statistically analyzed, and the average value of these multiple inner diameters is calculated. This average value is taken as the cavity diameter of the hollow particle.

[0091] When the cavity size of the hollow particles is not less than 2μm, the hollow particles have a suitable specific surface area, which is beneficial to increasing the contact area between the electrolyte and the hollow particles, which is beneficial to transporting more lithium ions per unit time and improving the rate performance of the battery cell. When the cavity size of the hollow particles is not greater than 10μm, the hollow particles have a suitable volume, which is beneficial to increasing the compaction density of the positive electrode sheet, thereby improving the volumetric energy density of the battery cell.

[0092] Optionally, the cavity size of the hollow particles is 4μm to 7μm. This is beneficial for balancing the rate performance and volumetric energy density of the battery cell.

[0093] In some embodiments, the volume average particle size D of lithium phosphate is... V 50 is 0.3μm to 1.5μm, for example, 0.3μm, 0.6μm, 0.8μm, 1.0μm, 1.2μm, 1.5μm or any other value outside the above range.

[0094] The volume average particle size D of lithium phosphate V When the particle size of lithium phosphate is not more than 1.5 μm, it has a suitable volume, which is beneficial to improving the compaction density of the positive electrode and the volumetric energy density of the battery cell. When the volume average particle size of lithium phosphate is not less than 0.3 μm, it is beneficial to maintain a suitable contact area between lithium phosphate and electrolyte, which is beneficial to improving the rate performance of the battery cell.

[0095] Optionally, the volume average particle size D of the lithium phosphate is... V The thickness is 0.6μm to 1.2μm. This is beneficial for further improving the rate performance and volumetric energy density of the battery cells.

[0096] In some embodiments, the mass percentage of lithium-rich manganese-based material is P based on the total mass of the positive electrode active material, where 10wt% ≤ P < 100wt%, for example, P is 10wt%, 20wt%, 30wt%, 50wt%, 70wt%, 80wt%, 90wt%, 95wt%, or any other value within the above range.

[0097] The mass ratio of lithium-rich manganese-based materials is the ratio of the mass of lithium-rich manganese-based materials to the mass of positive electrode active materials.

[0098] Optionally, the mass percentage of lithium-rich manganese-based materials can be calculated using the particle size and average density of solid and hollow particles in the lithium-rich manganese-based materials, as well as the particle size and average density of lithium phosphate-containing particles. Optionally, it can also be obtained using other testing methods, which are not limited in this application embodiment.

[0099] When P is not less than 10 wt%, the cathode material contains an appropriate amount of lithium-rich manganese-based material, which is beneficial to improving the energy density of the battery cell; when P is less than 100 wt%, the cathode material contains some lithium phosphate, which is beneficial to improving the cycle performance of the battery cell.

[0100] Optionally, 30wt% ≤ P ≤ 70wt%. This helps to further balance the energy density and cycle performance of individual battery cells.

[0101] Optionally, the positive electrode active material may also include other materials, such as lithium cobalt oxide, etc., which is not limited in this application embodiment.

[0102] In some embodiments, the specific capacity Q of the lithium-rich manganese-based material is ≥153 mAh / g, for example, 153 mAh / g, 158 mAh / g, 163 mAh / g or greater. This is beneficial for improving the energy density of the battery cell.

[0103] Specific capacity refers to the ratio of the amount of electricity that an active material can release to the mass of the active material.

[0104] The specific capacity of lithium-rich manganese-based materials can be measured using the following method. Lithium-rich manganese-based materials are used as the positive electrode active material to prepare lithium-ion batteries. The lithium-ion batteries are then subjected to charge-discharge tests. The specific capacity of the lithium-rich manganese-based material is the ratio of the discharge capacity of the lithium-ion battery obtained from the charge-discharge test to the mass of the lithium-rich manganese-based material. The charge-discharge test method is as follows: Under a constant temperature environment of 25℃, the lithium-ion battery is discharged at 1 / 3C to 2.5V; after standing for 5 minutes, it is charged at 1 / 3C to 4.35V, and then charged at a constant voltage of 4.35V until the current ≤0.05C; after standing for 5 minutes, it is discharged again at 1 / 3C to 2.5V. The amount of electricity released by the lithium-ion battery during this discharge process is the discharge capacity.

[0105] Optionally, the specific capacity of the lithium-rich manganese-based material is Q≥158mAh / g. This is beneficial for further improving the energy density of the battery cell.

[0106] In the embodiments of this application, different specific capacities can be achieved by selecting different types of lithium-rich manganese-based materials.

[0107] In some embodiments, the general formula of lithium-rich manganese-based materials is nLi₂MnO₃·(1-n)Li 1+x1 Ni x2 Mn x3 M 1 x4 O2, where 0.1≤n≤0.3, 0≤x1≤0.1, 0.3≤x2<1, 0<x3≤0.7, 0≤x4≤0.1, M 1 It includes one or more of Na, Mg, Al, Ca, Ba, V, Zn, Ti, Fe, Co, Cr, Nb, W, Mo, Zr, Ta, and Hf. This allows for flexible selection of lithium-rich manganese-based materials based on specific needs.

[0108] In some embodiments, the lithium-rich manganese-based material can be 0.1Li₂MnO₃·0.9LiNi. 0.5 Mn 0.5 O2, 0.2Li2MnO3·0.8LiNi 0.5 Mn 0.5 O2, 0.25Li2MnO3·0.75LiNi 0.5 Mn 0.5 O2 and 0.15Li2MnO3·0.85LiNi 0.5 Mn 0.5 O2, 0.3Li2MnO3·0.7LiNi 0.5 Mn 0.5 At least one of O2.

[0109] In some embodiments, the lithium-rich manganese-based material can be 0.2Li₂MnO₃·0.8LiNi. 0.5 Mn 0.45 Mg 0.05 O2, 0.2Li2MnO3·0.8LiNi 0.5 Mn 0.45 Al 0.05 O2, 0.2Li2MnO3·0.8LiNi 0.5 Mn 0.45 V 0.05 O2, 0.2Li2MnO3·0.8LiNi 0.5 Mn 0.45 Ti 0.05 O2, 0.2Li2MnO3·0.8LiNi 0.5 Mn 0.45 Co 0.05 O2, 0.2Li2MnO3·0.8LiNi 0.5 Mn 0.45 Nb 0.05 O2, 0.2Li2MnO3·0.8LiNi 0.5 Mn 0.45 W 0.05 O2, 0.2Li2MnO3·0.8LiNi 0.5 Mn 0.45 Mo 0.05 O2, 0.2Li2MnO3·0.8LiNi 0.5 Mn 0.45 Zr 0.05 O2, 0.2Li2MnO3·0.8LiNi 0.5 Mn 0.45 Ta 0.05 At least one of O2.

[0110] In some embodiments, M 1 In the case of Na, sodium ions can replace some of the lithium ion positions.

[0111] It should be noted that the general formula for lithium-rich manganese-based materials given in the embodiments of this application can be a general formula under ideal conditions. Ideally, this could include adding lithium-rich manganese-based materials that satisfy the above general formula during the preparation of the positive electrode active material. After the battery cell is prepared from the positive electrode active material, due to various factors such as lithium ion insertion / extraction or lithium ion consumption, the actual lithium ion content may be lower than that of the general formula for lithium-rich manganese-based materials. Similarly, the actual oxygen ion content may also be lower.

[0112] In some embodiments, the general formula for lithium phosphate is Li 1+y1 Fe y2 Mny3 M 2 y4 PO4, where 0≤y1≤0.1, 0≤y2≤1, 0≤y3≤1, 0≤y4≤0.1, M 2 This includes one or more transition metal elements other than Fe and Mn, as well as non-transition metal elements. This allows for flexible selection of lithium-containing phosphates based on actual needs.

[0113] In some embodiments, the lithium phosphate may be LiFePO4, Li 1.1 FePO4, LiMnPO4, LiMn 0.5 Fe 0.5 PO4, LiFe 0.5 Mn 0.45 Mg 0.05 PO4, LiFe 0.5 Mn 0.45 Al 0.05 PO4, LiFe 0.5 Mn 0.45 V 0.05 PO4, LiFe 0.5 Mn 0.45 Ti 0.05 PO4, LiFe 0.5 Mn 0.45 Co 0.05 PO4, LiFe 0.5 Mn 0.45 Nb 0.05 PO4, LiFe 0.5 Mn 0.45 W 0.05 PO4, LiFe 0.5 Mn 0.45 Mo 0.05 PO4, LiFe 0.5 Mn 0.45 Zr 0.05 PO4, LiFe 0.5 Mn 0.45 Ta 0.05 At least one of PO4.

[0114] Similarly, as described above, the general formula for lithium phosphates actually measured may be Li 1+a Fe 1-x2- y2 Mn x2 M2 y2 PO 4+b a<0, b<0.

[0115] In some embodiments, lithium phosphates can be modified by surface coating. For example, for LiFePO4, its conductivity can be improved by coating its surface with carbon or polymers. Alternatively, the material can be modified by doping it with metal cations or other ions. For example, for LiFePO4, it can be doped with high-valence metal cations to improve its conductivity.

[0116] [Positive electrode plate]

[0117] This application provides a positive electrode sheet, including the positive active material in any of the above possible embodiments.

[0118] The positive electrode sheet may include a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector, wherein the positive electrode material layer includes a positive electrode active material.

[0119] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0120] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum 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.).

[0121] In some embodiments, the compaction density of the positive electrode sheet under a pressure of 400 kN is 2.7 g / cm³. 3 ~2.9g / cm 3 Optionally, it is 2.75 g / cm³. 3 ~2.85g / cm 3 For example, the compaction density of the positive electrode sheet under a pressure of 400 kN is 2.7 g / cm³. 3 2.75g / cm 3 2.8g / cm 3 2.85g / cm 3 2.9g / cm 3 This helps to increase the energy density of individual battery cells.

[0122] The compaction density of the positive electrode sheet may vary after cold pressing under different pressures. Optionally, the cold pressing pressure of the positive electrode sheet shall not exceed 800 kN.

[0123] In some embodiments, the positive electrode material layer includes a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0124] In some embodiments, the positive electrode material layer includes 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.

[0125] 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, additive 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.

[0126] [Negative electrode plate]

[0127] A negative electrode typically includes a negative current collector and a negative electrode material layer disposed on at least one surface of the negative current collector, wherein the negative electrode material layer includes a negative electrode active material.

[0128] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0129] 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.).

[0130] 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 include at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may include 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.

[0131] In some embodiments, the negative electrode material layer may optionally include an adhesive. The adhesive may include 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).

[0132] In some embodiments, the negative electrode material layer may optionally include a conductive agent. 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.

[0133] In some embodiments, the negative electrode material may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0134] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as 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.

[0135] [Electrolytes]

[0136] 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.

[0137] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0138] In some embodiments, the electrolyte salt may include 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.

[0139] In some embodiments, the solvent may include at least one selected from 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.

[0140] 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.

[0141] [Isolation Component]

[0142] 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.

[0143] In some embodiments, the material of the separator may include at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a separator film, which may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator film is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0144] In some embodiments, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly by a winding process or a stacking process.

[0145] [Battery cell]

[0146] This application provides a battery cell including the positive electrode sheet in any of the above embodiments.

[0147] The embodiments of this application do 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 10 as an example.

[0148] Figure 2 is an exploded structural diagram of a battery cell according to an embodiment of this application. In some embodiments, the battery cell may include an outer packaging. The outer packaging can be used to encapsulate electrode components and electrolyte. Referring to Figure 2, the outer packaging may include a housing 21 and a cover plate 22. The housing 21 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 21 has an opening communicating with the receiving cavity, and the cover plate 22 can cover the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator can be formed into an electrode assembly 23 by a winding process or a stacking process. The electrode assembly 23 is encapsulated in the receiving cavity. Electrolyte is immersed in the electrode assembly 23. The number of electrode assemblies 23 in the battery cell 10 can be one or more, which can be selected according to specific actual needs.

[0149] 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.

[0150] In some implementations, the battery cells 10 can be assembled into a battery module, and the number of battery cells 10 contained in the battery module can be one or more, the specific number of which can be selected according to the application and capacity of the battery module.

[0151] Figure 3 is a schematic diagram of a battery module 300 according to an embodiment of this application. Referring to Figure 3, in the battery module 300, a plurality of battery cells 10 can be arranged sequentially along the length direction of the battery module 300. Of course, they can also be arranged in any other arbitrary manner.

[0152] In some embodiments, the battery module 300 can also be assembled into a battery, and the number of battery modules 300 contained in the battery can be one or more, the specific number of which can be selected according to the application and capacity of the battery.

[0153] [Battery]

[0154] This application provides a battery comprising the battery cell described in the above embodiments.

[0155] Figure 4 is a schematic diagram of a battery according to an embodiment of this application, and Figure 5 is a schematic diagram of a battery according to an embodiment of this application. As an example, referring to Figures 4 and 5, the battery 400 may include a battery case and a plurality of battery modules 300 disposed within the battery case. The battery case includes an upper casing 401 and a lower casing 402, the upper casing 401 covering the lower casing 402 and forming a closed space for accommodating the battery modules 300. The plurality of battery modules 300 may be arranged in any manner within the battery case.

[0156] The battery cells 10 can be directly assembled into a battery 400. Alternatively, the battery cells 10 do not need to be assembled into a battery module first; they can be directly assembled into a battery 400. The number of battery cells included in the battery is not limited in this embodiment.

[0157] [Electrical appliances]

[0158] This application provides an electrical device, including the battery described in the above embodiments.

[0159] Figure 6 is a schematic diagram of an electrical device according to an embodiment of this application. As an example, the electrical device is a vehicle.

[0160] 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.

[0161] Example

[0162] Example 1

[0163] In Example 1, the positive electrode active material includes a lithium-rich manganese-based material and a lithium-containing phosphate. The lithium-containing phosphate is lithium iron phosphate (LiFePO4), and the lithium-rich manganese-based material is 0.2Li₂MnO₃·0.8LiNi₂. 0.5 Mn 0.5 O2.

[0164] Lithium iron phosphate D V The thickness is 0.5 μm, and the specific capacity of the lithium-rich manganese-based material is 158 mAh / g. Based on the total mass of the positive electrode active material, the mass content of the lithium-rich manganese-based material in the positive electrode active material is 50 wt%.

[0165] In lithium-rich manganese-based materials, the mass ratio of solid particles to hollow particles (A:B) is 8:2. The mass ratio of solid particles (D) is... V 50 is 5μm, D of hollow particles V The diameter of 50 is 9μm, and the cavity size of the hollow particle is 4μm.

[0166] Examples 2-4

[0167] The difference between Examples 2-4 and Example 1 is that A and B are different.

[0168] In Examples 2-4, the ratios of A to B are 7:3, 9:1, and 5:5, respectively.

[0169] Examples 5-8

[0170] The difference between Examples 5-8 and Example 1 is that the volume average particle size D of the solid particles is... V 50 different.

[0171] In Examples 5-8, the volume average particle size D of the solid particles V The sizes 50 are 2μm, 3μm, 6μm, and 8μm.

[0172] Examples 9-12

[0173] The difference between Examples 9-12 and Example 1 is that the volume average particle size D of the hollow particles is... V 50 different.

[0174] In Examples 9-12, the volume average particle size D of the hollow particles V The 50 values ​​are: 6μm, 7μm, 12μm, and 15μm.

[0175] Examples 13-15

[0176] The difference between Examples 13-14 and Example 1 is that the size of the cavity of the hollow particle is different.

[0177] In Examples 13-14, the cavity dimensions of the hollow particles were 2 μm and 7 μm, respectively.

[0178] The difference between Example 15 and Example 1 is that the volume average particle size D of the hollow particles is... V 50. The dimensions of the cavity of hollow particles, and the volume average particle size D of hollow particles. V 50 and the volume average particle size D of solid particles V The difference of 50 is different.

[0179] In Example 15, the volume average particle size D of the hollow particles V 50 is 15μm, the cavity size of the hollow particle is 10μm, and the volume average particle size D of the hollow particle is... V 50 and the volume average particle size D of solid particles V The difference of 50 is 10 μm.

[0180] Examples 16-17

[0181] The difference between Examples 16-17 and Example 1 is that the specific capacity of the lithium-rich manganese-based materials is different.

[0182] In Examples 16 and 17, the specific capacities of the lithium-rich manganese-based materials were 153 mAh / g and 163 mAh / g, respectively.

[0183] Accordingly, in Examples 16 and 17, the lithium-rich manganese-based materials were 0.25Li₂MnO₃·0.75LiNi, respectively. 0.5Mn 0.5 O2 and 0.15Li2MnO3·0.85LiNi 0.5 Mn 0.5 O2.

[0184] Examples 18-21

[0185] The difference between Examples 18-21 and Example 1 is that the volume average particle size D of lithium iron phosphate is... V 50 are different.

[0186] In Examples 18-21, the volume average particle size D of lithium iron phosphate was... V The 50 values ​​are: 0.5μm, 0.6μm, 1.2μm, and 1.5μm.

[0187] Examples 22-23

[0188] The difference between Examples 22-23 and Example 1 is that the mass ratio of lithium-rich manganese-based material to positive electrode active material is different.

[0189] In Examples 22-23, the mass ratios of lithium-rich manganese-based material to positive electrode active material were 30 wt% and 70 wt%, respectively.

[0190] Examples 24-25

[0191] The difference between Examples 24-25 and Example 1 lies in the type of lithium phosphate contained. In Examples 24-25, the lithium phosphate contained is LiFe, respectively. 0.5 Mn 0.45 Mg 0.05 PO4, LiMn 0.5 Fe 0.5 PO4.

[0192] Comparative Example 1

[0193] The difference between Comparative Example 1 and Example 1 is that the lithium-rich manganese-based materials are all solid particles.

[0194] Comparative Example 2

[0195] The difference between Comparative Example 2 and Example 1 is that the lithium-rich manganese-based materials are all hollow particles.

[0196] Battery cells were prepared using the above-mentioned positive electrode active material, and the performance of the battery cells was tested. Specific parameters and test results are shown in Table 1. The preparation and testing methods for the battery cells are described below.

[0197] [Preparation of battery cells]

[0198] (1) Preparation of positive electrode sheet

[0199] The positive electrode active material, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 94:4:2. N-methylpyrrolidone was added as a solvent, and the mixture was thoroughly stirred and mixed under vacuum to obtain a uniform positive electrode slurry. The positive electrode slurry was then uniformly coated onto both surfaces of an untreated positive electrode current collector aluminum foil, ensuring identical coating quality on both surfaces. After drying, cold pressing, and slitting, the positive electrode sheet was obtained.

[0200] (2) Preparation of negative electrode sheet

[0201] Artificial graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and binder sodium carboxymethyl cellulose (CMC) were mixed in a mass ratio of 95:1.5:3.1:0.4. Deionized water was added as a solvent, and the mixture was stirred thoroughly to obtain a uniform negative electrode slurry. The negative electrode slurry was then uniformly coated onto both surfaces of the untreated negative electrode current collector copper foil, followed by drying and cold pressing to a density of 1.65 g / cm³. 3 The negative electrode sheet is obtained by cutting.

[0202] (3) Preparation of electrolyte

[0203] In an argon-atmospheric glove box with a water content of <10 ppm, ethylene carbonate (EC), polycarbonate (PC), and dimethyl carbonate (DMC) were mixed in a mass ratio of EC:PC:DMC = 3:3:3. LiPF6 was then added, and the mixture was stirred until homogeneous to obtain the electrolyte. The concentration of LiPF6 in the electrolyte was 1 mol / L.

[0204] (4) Assembly of battery cells

[0205] The positive electrode, polyethylene (PE) separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to isolate them. The stacked components are then wound to form an electrode assembly. The electrode assembly is placed in the battery casing, dried, and then injected with electrolyte. After formation and settling processes, a lithium-ion battery cell is obtained.

[0206] [Performance Testing of Individual Battery Cells]

[0207] (1) Ratio Performance Test

[0208] At 25℃, a single lithium-ion battery cell is charged at a constant current rate of 0.1C to 4.35V, then charged at a constant voltage rate to a current of 0.05C, left to stand for 5 minutes, and then discharged at a constant current rate of 0.1C to 2.5V. The discharge capacity at this point is recorded as the 0.1C discharge capacity. After standing for 30 minutes, the secondary battery is charged at a constant current rate of 0.1C to 4.35V, then charged at a constant voltage rate to a current of 0.05C, left to stand for 5 minutes, and then discharged at a constant current rate of 2C to 2.5V. The discharge capacity at this point is recorded as the 2C discharge capacity.

[0209] The rate performance of a battery is R = 2C discharge capacity / 0.1C discharge capacity × 100%.

[0210] (2) Volumetric energy density test

[0211] At 25°C, a single lithium-ion battery cell is charged at a constant current of 0.33C to 4.35V, then charged at a constant voltage of 4.35V until the current is less than 0.05C, and then discharged at 0.33C to 2.5V to obtain the discharge energy E; the dimensions of the battery are measured using vernier calipers, and the volume V is calculated.

[0212] Volumetric energy density K = E / V.

[0213] As an example, the battery cell model in this embodiment is 406080, and the battery thickness T is approximately 4 mm, varying with the compaction density of the positive electrode sheet; the actual measured thickness shall prevail. The width W of the battery cell is 60 mm; the height H is 80 mm. The volumetric energy density is then calculated.

[0214] (3) Compacted density measurement

[0215] After the positive electrode sheet is cold-pressed (cold-pressing pressure is 400KN), the electrode sheet thickness T is measured. The compaction density ρ is calculated based on the thickness T and the areal density m of the positive electrode sheet. 压 The calculation formula is as follows: ρ 压 =m / (TT) 箔 Where m is the areal density of the electrode (g / cm³). 2 T 箔 The thickness of the positive current collector is 1 cm.

[0216] In Table 1, the volume average particle size D of the solid particles is... V 50 is represented by D1, where D is the volume average particle size of the hollow particles. V 50 is represented by D2, where D is the volume average particle size of hollow particles. V 50 and the volume average particle size D of solid particles V The difference of 50 is represented by D3, the cavity size of the hollow particles is represented by D4, and the volume average particle size of lithium iron phosphate is D. V50 is represented by D5, the mass ratio of lithium-rich manganese-based material to positive electrode active material is represented by P, the specific capacity of lithium-rich manganese-based material is represented by Q, and the compaction density of the positive electrode sheet is represented by ρ. 压 The energy density of a single battery cell is represented by K, and the rate performance of a single battery cell is represented by R.

[0217] Table 1. Specific parameters and test results for the examples and comparative examples.

[0218]

[0219]

[0220]

[0221] Combining Example 1 and Comparative Example 1, incorporating solid and hollow particles into the lithium-rich manganese-based material is beneficial for improving the rate performance of the battery cell; combining Example 1 and Comparative Example 2, incorporating solid and hollow particles into the lithium-rich manganese-based material is beneficial for improving the volumetric energy density of the battery cell. Therefore, the technical solution of this application embodiment is beneficial for balancing the volumetric energy density and rate performance of the battery cell.

[0222] In conjunction with Examples 2-4, by rationally setting the mass ratio of solid particles to hollow particles, it is beneficial to balance the rate performance and energy density of the battery cell. In conjunction with Examples 5-8, 9-12, 13-15, and 18-21, by rationally setting the particle size of hollow particles, solid particles, and the particle size of lithium phosphate, it is beneficial to balance the rate performance and energy density of the battery cell. In conjunction with Examples 16-17, selecting a suitable lithium-rich manganese-based material is beneficial to improving the energy density of the battery cell. In conjunction with Examples 22-23, by rationally setting the mass ratio of lithium-rich manganese-based material to positive electrode active material, it is beneficial to balance the rate performance and energy density of the battery cell. In conjunction with Examples 24-25, various different materials can be selected as the lithium phosphate.

[0223] 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 positive electrode active material, characterized in that, The materials include lithium-rich manganese-based materials and lithium-containing phosphates. The lithium-rich manganese-based materials include solid particles and hollow particles. The hollow particles include a shell and a cavity disposed inside the shell. The general formula of the lithium-rich manganese-based materials is nLi₂MnO₃•(1-n)Li. 1+x1 Ni x2 Mn x3 M1 x4 O2, wherein 0.1≤n≤0.3, 0≤x1≤0.1, 0.3≤x2<1, 0<x3≤0.7, 0≤x4≤0.1, and M1 includes one or more of Na, Mg, Al, Ca, Ba, V, Zn, Ti, Fe, Co, Cr, Nb, W, Mo, Zr, Ta, and Hf; in the lithium-rich manganese-based material, the ratio of the number of solid particles E to the number of hollow particles F is 70:30≤E:F≤96:

4.

2. The positive electrode active material according to claim 1, characterized in that, In the lithium-rich manganese-based material, the ratio of the mass A of the solid particles to the mass B of the hollow particles is 1:1 ≤ A:B ≤ 9:1; and / or, the ratio of the number E of the solid particles to the number F of the hollow particles is 85:15 ≤ E:F ≤ 90:

10.

3. The positive electrode active material according to claim 2, characterized in that, The ratio of the mass A of the solid particle to the mass B of the hollow particle is 7:3 ≤ A:B ≤ 8:

2.

4. The positive electrode active material according to claim 1, characterized in that, The volume average particle size D of the solid particles V 50 is 2μm~8μm.

5. The positive electrode active material according to claim 4, characterized in that, The volume average particle size D of the solid particles V 50 is 3μm~6μm.

6. The positive electrode active material according to claim 1, characterized in that, The volume average particle size D of the hollow particles V 50 represents 5μm to 15μm.

7. The positive electrode active material according to claim 6, characterized in that, The volume average particle size D of the hollow particles V 50 is 7μm~12μm.

8. The positive electrode active material according to any one of claims 1-7, characterized in that, The volume average particle size D of the hollow particles V 50 is greater than the volume average particle size D of the solid particles. V 50; and / or, the number-average particle size of the hollow particles is greater than the number-average particle size of the solid particles.

9. The positive electrode active material according to claim 8, characterized in that, The volume average particle size D of the hollow particles V 50 and the volume average particle size D of the solid particles V The difference between 50 and 3μm is 10μm.

10. The positive electrode active material according to claim 9, characterized in that, The volume average particle size D of the hollow particles V 50 and the volume average particle size D of the solid particles V The difference between 50 and 8 μm is 4 μm to 8 μm.

11. The positive electrode active material according to claim 8, characterized in that, The difference between the number-average particle size of the hollow particles and the number-average particle size of the solid particles is 3 μm to 10 μm.

12. The positive electrode active material according to claim 11, characterized in that, The difference between the number-average particle size of the hollow particles and the number-average particle size of the solid particles is 4 μm to 8 μm.

13. The positive electrode active material according to any one of claims 1-7, characterized in that, The cavity of the hollow particle has a size of 2μm to 10μm.

14. The positive electrode active material according to claim 13, characterized in that, The cavity of the hollow particle has a size of 4μm to 7μm.

15. The positive electrode active material according to any one of claims 1-7, characterized in that, The volume average particle size D of the lithium phosphate V 50 ranges from 0.3μm to 1.5μm.

16. The positive electrode active material according to claim 15, characterized in that, The volume average particle size D of the lithium phosphate V 50 ranges from 0.6μm to 1.2μm.

17. The positive electrode active material according to any one of claims 1-7, characterized in that, Based on the total mass of the positive electrode active material, the mass percentage of the lithium-rich manganese-based material is P, where 10wt%≤P<100wt%.

18. The positive electrode active material according to claim 17, characterized in that, 30wt%≤P≤70wt%.

19. The positive electrode active material according to any one of claims 1-7, characterized in that, The specific capacity Q of the lithium-rich manganese-based material is ≥153mAh / g.

20. The positive electrode active material according to claim 19, characterized in that, Q≥158mAh / g.

21. The positive electrode active material according to any one of claims 1-7, characterized in that, The general formula of the lithium phosphate is Li 1+y1 Fe y2 Mn y3 M 2 y4 PO4, where 0≤y1≤0.1, 0≤y2≤1, 0≤y3≤1, 0≤y4≤0.1, M 2 It includes one or more transition metal elements other than Fe and Mn, as well as non-transition metal elements.

22. A positive electrode plate, characterized in that, Includes the positive electrode active material as described in any one of claims 1-21.

23. The positive electrode sheet according to claim 22, characterized in that, The compaction density of the positive electrode sheet is 2.70 g / cm³. 3 ~2.90g / cm 3 .

24. The positive electrode sheet according to claim 23, characterized in that, The compaction density of the positive electrode sheet is 2.75 g / cm³. 3 ~2.85g / cm 3 .

25. A single battery cell, characterized in that, The battery cell includes a positive electrode sheet as described in any one of claims 22-24.

26. A battery, characterized in that, The battery includes the battery cell as described in claim 25.

27. An electrical appliance, characterized in that, The electrical device includes the battery as described in claim 26.

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