Battery cell, battery device, power consuming device, and energy storage device

Abstract

Embodiments of the present application provide a battery monomer, a battery device, a power consumption device and an energy storage device. The battery monomer comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, the positive electrode film layer comprises a positive electrode active material, and the positive electrode active material comprises layered transition metal oxide particles, the layered transition metal oxide particles comprise components with a general formula of Li a M b O c , wherein 0.8≤a≤1.3, 0.8 The battery monomer has good thermal safety performance and high energy density.

Description

Technical Field

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

[0002] As market demand for longer driving ranges of electrical devices increases, higher requirements are being placed on the energy density of individual battery cells. To meet the demands for long driving range and high efficiency, high-energy-density cathode materials are widely used. However, these materials often suffer from insufficient thermal safety performance under extreme conditions such as high temperatures, which can easily lead to battery thermal runaway and subsequent safety hazards. Therefore, how to improve energy density while ensuring thermal safety performance has become a crucial issue that current battery material technology urgently needs to address. Summary of the Invention

[0003] This application aims to at least address one of the technical problems existing in the background art. Therefore, one object of this application is to provide a battery cell, battery device, power supply device, and energy storage device to improve the thermal safety performance of high-capacity positive electrode active materials.

[0004] A first aspect of this application provides a battery cell, the battery cell including a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive electrode film layer disposed on at least one side of the surface of the positive current collector, the positive electrode film layer including a positive electrode active material, the positive electrode active material including layered transition metal oxide particles, the layered transition metal oxide particles including particles of the general formula Li a M b O c The composition includes 0.8≤a≤1.3, 0.8<b≤1, 1.5<c≤2, and M includes one or more of Ni, Co, Mn, and Al; in the cross-section of the layered transition metal oxide particles, the molar ratio of Li to M near the surface is greater than the molar ratio of Li to M near the center of the particles.

[0005] To meet the demands for long-lasting and high-efficiency applications, high-energy-density cathode materials such as layered transition metal oxides are widely used. However, these materials often suffer from insufficient thermal safety performance under extreme conditions such as high temperatures, making them prone to battery thermal runaway. Specifically, research shows that at high temperatures (160℃-250℃), lithium-ion desorption leads to a decrease in the stability of the chemical bond (MO bond) between M and O elements. Consequently, layered transition metal oxides in the lithium-ion desorption state are prone to releasing oxygen. The released oxygen reacts with the electrolyte, lithium in the negative electrode, and the negative electrode active material, generating a large amount of heat and leading to battery thermal runaway.

[0006] The applicant's research found that by ensuring "the molar ratio of Li to M elements near the surface of the layered transition metal oxide particles is greater than that near the particle center," the battery cell can achieve both high energy density and good thermal safety performance. Although the mechanism is not yet clear, experiments suggest this may be related to surface lithium replenishment of the layered transition metal oxide particles. Lithium ions are extracted more rapidly and in greater quantities at the particle surface, leading to more severe oxygen release. Therefore, by increasing the molar ratio of Li to M elements at the particle surface, and through in-situ lithium replenishment targeting the deeply delithiated particle surface region, the stability of the MO bond is improved, thereby increasing the oxygen release temperature of the cathode active material. This improves the thermal safety performance of the high-capacity cathode active material, achieving a balance between thermal safety and high energy density in the battery cell.

[0007] In some embodiments, the surface of the layered transition metal oxide particles is further provided with a coating layer, the coating layer comprising a solid electrolyte.

[0008] In some embodiments, the coating layer disposed on the surface of the layered transition metal oxide particles can intercept oxygen released from the layered transition metal oxide particles to a certain extent, thereby further improving the thermal safety performance of the battery cell.

[0009] In some embodiments, the coating layer on the surface of layered transition metal oxide particles can replenish lithium to the particles under high temperatures, thereby improving the thermal safety performance of the battery cell. However, lithium replenishment materials often have poor ionic conductivity, sacrificing the battery's kinetic performance. This application presents a novel solid electrolyte material capable of replenishing lithium, which, when used as a coating layer for layered transition metal oxides, improves both the thermal safety performance and the battery's kinetic performance.

[0010] In some embodiments, the solid electrolyte includes one or more of lithium titanium aluminum phosphate oxide, lithium aluminum phosphate oxide, and tantalum-doped lithium lanthanum zirconium oxide.

[0011] In some embodiments, the tantalum-doped lithium lanthanum zirconium oxide has the general formula shown in Formula I, Li 6.4 La3Zr y1 Ta y2 O 12 Equation I, 0 < y1 < 2 and 0 < y2 < 2.

[0012] In some embodiments, the general formula of the lithium aluminum titanium phosphate oxide is shown in Formula II, Li x1 Al x2 Ti x3(PO4)3, 1.5≤x1<3, 0.2≤x2<2 and 0≤x3<1.8 Formula II; the lithium aluminum phosphate oxide is Li3Al2(PO4)3.

[0013] The applicant's research found that when the solid electrolyte is selected from the above range, it not only has good ionic conductivity, which can improve the thermal safety performance of the battery cell while taking into account the kinetic performance, but also has a good lithium replenishment effect. That is, at high temperature, it can replenish lithium to the deeply delithiated layered transition metal oxide, improve the stability of MO bond, and thus increase the oxygen release temperature of the positive electrode active material, thereby achieving a balance between the thermal safety performance, kinetic performance and high energy density of the battery cell.

[0014] In some embodiments, the thickness of the coating layer is from 0.02 μm to 2 μm.

[0015] In the embodiments of this application, when the coating thickness is within the above-mentioned range, the thermal safety performance of the battery cell can be further improved.

[0016] In some embodiments, the layered transition metal oxide particles are doped with La, Zr and Ta elements.

[0017] In the embodiments of this application, the thermal safety performance and kinetic performance of the battery cell are further improved by doping with the above-mentioned elements.

[0018] In some embodiments, in the cross-section of the layered transition metal oxide particles, the mass contents of La, Zr, and Ta elements near the surface are greater than the mass contents of La, Zr, and Ta elements near the center.

[0019] In the embodiments of this application, the thermal safety performance and dynamic performance of the battery cell are further improved by the element distribution within the above-mentioned range.

[0020] In some embodiments, the layered transition metal oxide particles are doped with Al, Ti and P elements, and M includes one or more of Ni, Co and Mn.

[0021] In the embodiments of this application, the thermal safety performance and kinetic performance of the battery cell are further improved by doping with the above-mentioned elements.

[0022] In some embodiments, in the cross-section of the layered transition metal oxide particles, the mass contents of Al, Ti, and P elements near the surface are greater than the mass contents of Al, Ti, and P elements near the center.

[0023] In the embodiments of this application, the thermal safety performance and dynamic performance of the battery cell are further improved by the element distribution within the above-mentioned range.

[0024] In some embodiments, the layered transition metal oxide particles are doped with Al, Ti, and P elements, wherein in the cross-section of the layered transition metal oxide particles, the molar ratio of Li to P elements near the surface is greater than the molar ratio of Li to P elements near the center.

[0025] In the embodiments of this application, the thermal safety performance and dynamic performance of the battery cell are further improved by the element distribution within the above-mentioned range.

[0026] In some embodiments, the layered transition metal oxide particles are doped with Al, Ti and P elements, and M includes one or more of Ni, Co and Mn. In the cross-section of the layered transition metal oxide particles, the molar ratio of Al to Ti near the surface is greater than that near the center.

[0027] In the embodiments of this application, the thermal safety performance and dynamic performance of the battery cell are further improved by the element distribution within the above-mentioned range.

[0028] In some embodiments, in the cross-section of the layered transition metal oxide particles, in the outer region 1 μm-3 μm from the surface toward the geometric center, the molar ratio of Al, Ti, and P is (1-2):(0-1):3:3.

[0029] In the embodiments of this application, the thermal safety performance and dynamic performance of the battery cell are further improved by the element distribution within the above-mentioned range.

[0030] In some embodiments, in the cross-section of the layered transition metal oxide particles, in the core region with a diameter of 3μm-10μm centered on the geometric center, the molar ratio of Al, Ti, and P is (0.2-1):(1-1.8):3.

[0031] In this embodiment, the elemental distribution within the aforementioned range further improves the thermal safety and kinetic performance of the battery cell. Furthermore, since the oxygen release rate in the core region is relatively low, there is no need to dope with high-lithium-content lithium titanium aluminum phosphate or lithium aluminum phosphate, thereby reducing production costs.

[0032] In some embodiments, in the cross-section of the layered transition metal oxide particles, in the core region with a diameter of 3μm-7μm centered on the geometric center, the molar ratio of Al, Ti, and P is (0.2-0.8):(1.2-1.8):3; in the outer layer region with a diameter of 1μm-3μm from the surface toward the geometric center, the molar ratio of Al, Ti, and P is (1.2-2):(0-0.8):3; and in the intermediate region between the core region and the outer layer region, the thickness is 1μm-3μm, and the molar ratio of Al, Ti, and P in the intermediate region is (0.8-1.2):(0.8-1.2):3.

[0033] In this embodiment, the elemental distribution within the aforementioned range further improves the thermal safety and kinetic performance of the battery cell. Furthermore, since the oxygen release rate is relatively low in the core and intermediate regions, there is no need to dope with high-lithium-content lithium titanium aluminum phosphate or lithium aluminum phosphate, thereby reducing production costs.

[0034] In some embodiments, the Dv50 of the positive electrode active material is 10μm-15μm.

[0035] In the embodiments of this application, when the Dv50 of the positive electrode active material is within the above-mentioned range, the kinetic performance of the battery cell can be further improved while ensuring thermal safety performance.

[0036] An embodiment of the second aspect of this application provides a method for preparing a positive electrode active material, comprising: coating layered transition metal oxide particles with a solid electrolyte to obtain a coated product; and sintering the coated product once to obtain a positive electrode active material; wherein the solid electrolyte comprises one or more of lithium aluminum titanium phosphate oxide, lithium aluminum phosphate oxide, and tantalum-doped lithium lanthanum zirconium oxide.

[0037] In the embodiments of this application, the cathode material prepared by the above method exhibits good thermal safety performance, kinetic performance, and high energy density. Although the mechanism is not yet clear, experiments suggest that this may be because the first sintering not only ensures the stable coating layer on the particle surface and replenishes lithium on the particle surface, resulting in a higher molar ratio of Li to M near the surface of the layered transition metal oxide particles compared to the particle center; in some cases, it also allows the solid electrolyte to diffuse into the particle interior through solid-phase diffusion, further improving the lithium replenishment effect of the solid electrolyte on the layered transition metal oxide particles, thereby improving the thermal safety performance of the high-energy-density cathode active material. Furthermore, the solid electrolyte used has high ionic conductivity, achieving a balance between good thermal safety performance, kinetic performance, and high energy density.

[0038] In some embodiments, the tantalum-doped lithium lanthanum zirconium oxide has the general formula shown in Formula I, Li 6.4 La3Zr y1 Ta y2 O 12 Equation I, 0 < y1 < 2 and 0 < y2 < 2.

[0039] In some embodiments, the general formula of the lithium aluminum titanium phosphate oxide is shown in Formula II, Li x1 Al x2 Ti x3 (PO4)3, 1.5≤x1<3, 0.2≤x2<2 and 0≤x3<1.8 Formula II; the lithium aluminum phosphate oxide is Li3Al2(PO4)3.

[0040] The applicant's research found that when the solid electrolyte is selected from the above range, it not only has good ionic conductivity, which can improve the thermal safety performance of the battery cell while taking into account the kinetic performance, but also has a good lithium replenishment effect. That is, at high temperature, it replenishes lithium to the deeply delithiated layered transition metal oxide, improves the stability of MO bond, and thus increases the oxygen release temperature of the positive electrode active material, thereby achieving a balance between the thermal safety performance, kinetic performance and high energy density of the battery cell.

[0041] In some embodiments, the layered transition metal oxide particles comprise Li a M b O c The composition includes 0.8 ≤ a < 1, 0.8 < b ≤ 1, 1.5 < c ≤ 2, and M includes one or more of Ni, Co, Mn, and Al.

[0042] In some embodiments, based on the mass of the positive electrode active material, the mass percentage of the solid electrolyte is 1.5%-10%.

[0043] In the embodiments of this application, when the mass ratio of the solid electrolyte is within the above range, the battery cell simultaneously has good thermal safety performance, kinetic performance and high energy density.

[0044] In some embodiments, based on the mass of the positive electrode active material, the mass percentage of the solid electrolyte is 3%-7%.

[0045] In the embodiments of this application, when the mass ratio of the solid electrolyte is within the above range, the battery cell simultaneously has good thermal safety performance, kinetic performance and high energy density.

[0046] In some embodiments, the Dv50 of the positive electrode active material is 10μm-15μm.

[0047] In the embodiments of this application, when the Dv50 of the positive electrode active material is within the above-mentioned range, the kinetic performance of the battery cell can be further improved while ensuring thermal safety performance.

[0048] In some embodiments, the temperature of the first sintering is 600℃-1000℃.

[0049] In the embodiments of this application, when the temperature of the first sintering is within the above range, the battery cell has good thermal safety performance, good kinetic performance and high energy density.

[0050] In some embodiments, the sintering time is 2h-8h.

[0051] In the embodiments of this application, when the sintering time is within the above range, the battery cell has good thermal safety performance, good kinetic performance and high energy density.

[0052] A third aspect of this application provides a method for preparing a positive electrode active material, comprising: heat-treating a first mixture containing a layered transition metal oxide precursor to obtain a sintered product; mixing the sintered product with a solid electrolyte and performing a second heat treatment to obtain the positive electrode active material, wherein the solid electrolyte comprises one or more of lithium aluminum titanium phosphate and lithium aluminum phosphate.

[0053] In the embodiments of this application, the cathode material prepared by the above method exhibits good thermal safety performance, kinetic performance, and high energy density. Although the mechanism is not yet clear, experiments suggest that this may be because a solid electrolyte is added during the formation of the layered transition metal oxide and sintered together. This allows the solid electrolyte to be doped into the interior of the layered transition metal oxide particles, resulting in a higher molar ratio of Li to M near the surface of the particles compared to the ratio near the particle center. This further enhances the lithium replenishment effect of the solid electrolyte on the layered transition metal oxide particles, thereby improving the thermal safety performance of the high-energy-density cathode active material. Furthermore, the solid electrolyte used has high ionic conductivity, achieving a balance between good thermal safety performance, kinetic performance, and high energy density.

[0054] In some embodiments, the general formula of the lithium aluminum titanium phosphate oxide is shown in Formula II, Li x1 Al x2 Ti x3 (PO4)3, 1.5≤x1<3, 0.2≤x2<2 and 0≤x3<1.8 Formula II; the lithium aluminum phosphate oxide is Li3Al2(PO4)3.

[0055] The applicant's research found that when the solid electrolyte is selected from the above range, it not only has good ionic conductivity, which can improve the thermal safety and kinetic performance of the positive electrode active material, but also has a good lithium replenishment effect. That is, at high temperature, it replenishes lithium to the deeply delithiated layered transition metal oxide, improves the stability of MO bond, and thus increases the oxygen release temperature of the positive electrode active material, thereby achieving a balance between thermal safety, kinetic performance and high energy density.

[0056] In some embodiments, the layered transition metal oxide includes the general formula Li a M b O c The composition includes 0.8 ≤ a < 1, 0.8 < b ≤ 1, 1.5 < c ≤ 2, and M includes one or more of Ni, Co, Mn, and Al.

[0057] In some embodiments, based on the mass of the positive electrode active material, the mass percentage of the solid electrolyte added before the second heat treatment is 1.5%-10%.

[0058] In the embodiments of this application, by introducing a solid electrolyte before the second heat treatment, the prepared positive electrode active material has good thermal safety performance, kinetic performance and high energy density.

[0059] In some embodiments, the temperature of the heat treatment is 600℃-1000℃, the time of the heat treatment is 6h-10h, the temperature of the second heat treatment is 800℃-1000℃, and the time of the second heat treatment is 2h-8h.

[0060] In the embodiments of this application, the positive electrode active material prepared under the above heat treatment conditions has good thermal safety performance, kinetic performance and high energy density.

[0061] In some embodiments, the first mixture also includes a solid electrolyte, and the mass percentage of the solid electrolyte added to the first mixture is 0.1%-10% based on the mass of the positive electrode active material.

[0062] In the embodiments of this application, by adding solid electrolytes within the above-mentioned mass ratio range to the first mixture, the prepared positive electrode active material has good thermal safety performance, kinetic performance and high energy density.

[0063] In some embodiments, the solid electrolyte includes one or more of lithium aluminum titanium phosphate and lithium aluminum phosphate, wherein the molar ratio of Li to phosphorus in the solid electrolyte added before the second heat treatment is greater than the molar ratio of Li to phosphorus in the solid electrolyte added before the heat treatment.

[0064] In this embodiment, since the degree of oxygen release inside the particles is relatively low, doping with lithium titanium aluminum phosphate oxide with a lower Li content at a position closer to the inside of the particles can reduce the cost of the material while ensuring good thermal safety performance, kinetic performance and high energy density.

[0065] In some embodiments, the heat treatment of the first mixture containing the layered transition metal oxide precursor to obtain a sintered product comprises: performing a first heat treatment on the first mixture containing the layered transition metal oxide precursor, and then performing a second heat treatment on the mixture and a solid electrolyte to obtain the sintered product.

[0066] In the embodiments of this application, the positive electrode active material prepared under the above heat treatment conditions has good thermal safety performance, kinetic performance and high energy density.

[0067] In some embodiments, the first mixture includes a solid electrolyte, wherein the molar ratio of Li to P in the solid electrolyte added before the re-heat treatment is greater than the molar ratio of Li to P in the first mixture.

[0068] In this embodiment, since the degree of oxygen release inside the particles is relatively low, doping with lithium titanium aluminum phosphate oxide with a lower Li content at a position closer to the inside of the particles can reduce the cost of the material while ensuring good thermal safety performance, kinetic performance and high energy density.

[0069] In some embodiments, based on the mass of the positive electrode active material, the mass percentage of the solid electrolyte added before the second heat treatment is 0.1%-10%.

[0070] In the embodiments of this application, by adding solid electrolytes within the above-mentioned mass ratio range before re-heat treatment, the prepared positive electrode active material has good thermal safety performance, kinetic performance and high energy density.

[0071] In some embodiments, the temperature of the first heat treatment is 700°C-900°C, and the temperature of the second heat treatment is 800°C-1000°C.

[0072] In the embodiments of this application, the positive electrode active material prepared under the above heat treatment conditions has good thermal safety performance, kinetic performance and high energy density.

[0073] An embodiment of the fourth aspect of this application provides a battery device comprising a battery cell as described in any of the embodiments of the first aspect or a battery cell obtained by the preparation method described in any of the embodiments of the second or third aspect. The battery device includes one or more of a battery module, a battery pack, and an energy storage battery.

[0074] An embodiment of the fifth aspect of this application provides an electrical device that includes the battery device in any of the embodiments of the fourth aspect described above, the battery device being used to provide electrical energy.

[0075] An embodiment of the sixth aspect of this application provides an energy storage device, which includes the battery device of any of the embodiments of the fourth aspect described above, the battery device being used to store electrical energy.

[0076] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0077] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the various drawings denote the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings depict only some embodiments disclosed in this application and should not be construed as limiting the scope of this application.

[0078] Figure 1 This is a schematic diagram of the vehicle structure according to some embodiments of this application;

[0079] Figure 2 This is an exploded structural diagram of a battery according to some embodiments of this application;

[0080] Figure 3 This is an exploded structural diagram of a battery cell according to some embodiments of this application;

[0081] Figure 4 The DSC test results are for Comparative Example 4, Example 1, Example 7, and Example 21 of this application;

[0082] Explanation of reference numerals in the attached figures:

[0083] 1000 vehicles;

[0084] Battery unit 100, controller 200, motor 300;

[0085] Box 10, Part 11, Part 2 12;

[0086] Battery cell 20, end cap 21, electrode terminal 21a, housing 22, electrode assembly 23, tab 23a. Detailed Implementation

[0087] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0088] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0089] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0090] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. In the description of the embodiments of this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0091] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0092] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0093] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0098] As market demand for longer driving ranges of electrical devices increases, higher requirements are being placed on the energy density of individual battery cells. To meet the demands for long driving range and high efficiency, high-energy-density cathode materials are widely used. However, these materials often suffer from insufficient thermal safety performance under extreme conditions such as high temperatures, which can easily lead to battery thermal runaway and subsequent safety hazards. Therefore, how to improve energy density while ensuring thermal safety performance has become a crucial issue that current battery material technology urgently needs to address.

[0099] A first aspect of this application provides a battery cell, the battery cell including a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive electrode film layer disposed on at least one side of the surface of the positive current collector, the positive electrode film layer including a positive electrode active material, the positive electrode active material including layered transition metal oxide particles, the layered transition metal oxide particles including particles of the general formula Li a M b O c The composition includes 0.8≤a≤1.3, 0.8<b≤1, 1.5<c≤2, and M includes one or more of Ni, Co, Mn, and Al; in the cross-section of the layered transition metal oxide particles, the molar ratio of Li to M near the surface is greater than the molar ratio of Li to M near the center of the particles.

[0100] In this paper, "Layered transition metal oxides Li a M b O c Alkali metals (Al-I) are a class of inorganic compounds with a layered crystal structure, typically composed of alkali metal ions (such as lithium) embedded between layers of transition metal oxides. Their basic structural unit is a two-dimensional layered framework formed by oxygen-octahedral coordinated transition metals, allowing for reversible insertion and extraction of alkali metal ions between layers. Due to their excellent ionic conductivity and high specific capacity, these materials are widely used in cathode materials for lithium-ion batteries.

[0101] In some embodiments, a is a range of values ​​between 0.8, 0.9, 1.0, 1.1, 1.2, 1.3 or any two of them, b is a range of values ​​between 0.85, 0.90, 0.95, 1.0 or any two of them, and c is a range of values ​​between 1.6, 1.7, 1.8, 1.9, 2.0 or any two of them.

[0102] In some embodiments, Li a M b O c The value is LiCoO2, meaning a is 1, b is 1, and c is 2.

[0103] In some embodiments, Li a M b O c Lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide, such as LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.85 Co 0.1 Mn 0.05 O2, LiNi 0.9 Co 0.05 Mn 0.05 O2, LiNi 0.91 Co 0.05 Mn 0.04 O2, LiNi 0.95 Co 0.03 Mn 0.02 O2, etc.

[0104] In this paper, "near the surface of the cross-section of layered metal oxide particles" refers to the molar ratio of Li to M elements within a region extending from the surface towards the particle center, such as 0nm-30nm, 0-100nm, 0nm-200nm, 0nm-300nm, 0nm-400nm, or 0nm-500nm. "Near the particle center" refers to a region with a radius of, for example, 30nm, 100nm, 200nm, 300nm, 400nm, 500nm, 1μm, 2μm, 3μm, 4μm, or 5μm, centered approximately at the center of the particle cross-section, and where the two regions do not overlap for the same particle cross-section. The molar ratio of Li to M elements can be detected using conventional techniques in the art. As an example, a battery cell is disassembled to obtain the positive electrode sheet, which is then cut using an ion beam to expose the cross-sectional region of the positive electrode active material particles. Subsequently, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) was used to map the cross-section of the particles to obtain the elemental distribution and relative molar ratios in different regions.

[0105] To meet the demands for long-lasting and high-efficiency applications, high-energy-density cathode materials such as layered transition metal oxides are widely used. However, these materials often suffer from insufficient thermal safety performance under extreme conditions such as high temperatures, making them prone to battery thermal runaway. Specifically, research shows that at high temperatures (160℃-250℃), lithium-ion desorption leads to a decrease in the stability of the chemical bond (MO bond) between M and O elements. Consequently, layered transition metal oxides in the lithium-ion desorption state are prone to releasing oxygen. The released oxygen reacts with the electrolyte, lithium in the negative electrode, and the negative electrode active material, generating a large amount of heat and leading to battery thermal runaway.

[0106] The applicant's research found that by ensuring "the molar ratio of Li to M elements near the surface of the layered transition metal oxide particles is greater than that near the particle center," the battery cell can achieve both high energy density and good thermal safety performance. Although the mechanism is not yet clear, experiments suggest this may be related to surface lithium replenishment of the layered transition metal oxide particles. Lithium ions are extracted more rapidly and in greater quantities at the particle surface, leading to more severe oxygen release. Therefore, by increasing the molar ratio of Li to M elements at the particle surface, and through in-situ lithium replenishment targeting the deeply delithiated particle surface region, the stability of the MO bond is improved, thereby increasing the oxygen release temperature of the cathode active material. This improves the thermal safety performance of the high-capacity cathode active material, achieving a balance between thermal safety and high energy density in the battery cell.

[0107] In some embodiments, the surface of the layered transition metal oxide particles is further provided with a coating layer, the coating layer comprising a solid electrolyte.

[0108] In some embodiments, the coating layer disposed on the surface of the layered transition metal oxide particles can intercept oxygen released from the layered transition metal oxide particles to a certain extent, thereby further improving the thermal safety performance of the battery cell.

[0109] In some embodiments, the coating layer on the surface of layered transition metal oxide particles can replenish lithium to the particles under high temperatures, thereby improving the thermal safety performance of the battery cell. However, lithium replenishment materials often have poor ionic conductivity, sacrificing the battery's kinetic performance. This application presents a novel solid electrolyte material capable of replenishing lithium, which, when used as a coating layer for layered transition metal oxides, improves both the thermal safety performance and the battery's kinetic performance.

[0110] In some embodiments, the solid electrolyte includes one or more of lithium titanium aluminum phosphate oxide, lithium aluminum phosphate oxide, and tantalum-doped lithium lanthanum zirconium oxide.

[0111] In some embodiments, the tantalum-doped lithium lanthanum zirconium oxide has the general formula shown in Formula I, Li 6.4 La3Zr y1 Ta y2 O 12 Equation I, 0 < y1 < 2 and 0 < y2 < 2.

[0112] In this paper, tantalum-doped lithium lanthanum zirconium oxide Li 6.4 La3Zr y1 Ta y2 O 12 This refers to a type of garnet-type solid electrolyte where zirconium is partially replaced by tantalum to optimize crystal structure and ionic conductivity. Ideally, the sum of y1 and y2 should be 2.

[0113] In some embodiments, y1 is a numerical range of 0.2, 0.5, 0.8, 1.1, 1.4, 1.7, or any two of them.

[0114] In some embodiments, y2 is a numerical range of 1.8, 1.5, 1.2, 0.9, 0.6, 0.3, or any two of them.

[0115] In some embodiments, the general formula of the lithium aluminum titanium phosphate oxide is shown in Formula II, Li x1 Al x2 Ti x3 (PO4)3, 1.5≤x1<3, 0.2≤x2<2 and 0≤x3<1.8 Formula II; the lithium aluminum phosphate oxide is Li3Al2(PO4)3.

[0116] In this paper, lithium titanium aluminum oxide Li x1 Al x2 Ti x3 (PO4)3 is a type of NASICON-type solid electrolyte. It can be understood that, ideally, x2 = x1 - 1, x3 = 2 - x2.

[0117] In some embodiments, x1 is a numerical range of 1.5, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, or any two of them.

[0118] In some embodiments, x2 is a numerical range of 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8 or any two of these.

[0119] In some embodiments, x3 is a numerical range of 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.7 or any two of these.

[0120] The applicant's research found that when the solid electrolyte is selected from the above range, it not only has good ionic conductivity, which can improve the thermal safety performance of the battery cell while taking into account the kinetic performance, but also has a good lithium replenishment effect. That is, at high temperature, it can replenish lithium to the deeply delithiated layered transition metal oxide, improve the stability of MO bond, and thus increase the oxygen release temperature of the positive electrode active material, thereby achieving a balance between the thermal safety performance, kinetic performance and high energy density of the battery cell.

[0121] In some embodiments, the thickness of the coating layer is from 0.02 μm to 2 μm.

[0122] In some embodiments, the thickness of the coating layer is 0.02 μm, 0.09 μm, 0.16 μm, 0.23 μm, 0.30 μm, 0.37 μm, 0.44 μm, 0.51 μm, 0.58 μm, 0.65 μm, 0.72 μm, 0.79 μm, 0.86 μm, 0.93 μm, 1.00 μm, 1.07 μm, 1.14 μm, 1.21 μm, 1.28 μm, 1.35 μm, 1.42 μm, 1.49 μm, 1.56 μm, 1.63 μm, 1.70 μm, 1.77 μm, 1.84 μm, 1.91 μm, 1.98 μm, 2.00 μm, or any value range between the two.

[0123] In the embodiments of this application, when the coating thickness is within the above-mentioned range, the thermal safety performance of the battery cell can be further improved.

[0124] In some embodiments, the layered transition metal oxide particles are doped with La, Zr and Ta elements.

[0125] In this paper, as an example, the doping of the above-mentioned elements can be achieved by doping tantalum-doped lithium lanthanum zirconium oxide as shown in Formula I into layered transition metal oxide particles.

[0126] In the embodiments of this application, the thermal safety performance and kinetic performance of the battery cell are further improved by doping with the above-mentioned elements.

[0127] In some embodiments, in the cross-section of the layered transition metal oxide particles, the mass contents of La, Zr, and Ta elements near the surface are greater than the mass contents of La, Zr, and Ta elements near the center.

[0128] In this paper, as an example, tantalum-doped lithium lanthanum zirconium oxide as shown in Formula I can be diffused from the surface of the layered transition metal oxide particles into the particle interior via solid-phase diffusion, such that the mass contents of La, Zr, and Ta elements near the surface of the layered transition metal oxide particles are greater than the mass contents of La, Zr, and Ta elements near the center.

[0129] In the embodiments of this application, the thermal safety performance and dynamic performance of the battery cell are further improved by the element distribution within the above-mentioned range.

[0130] In some embodiments, the layered transition metal oxide particles are doped with Al, Ti and P elements, and M includes one or more of Ni, Co and Mn.

[0131] In this paper, as an example, the above-mentioned elements can be doped by doping layered transition metal oxides with lithium titanium aluminum phosphate or lithium aluminum phosphate as shown in Formula II.

[0132] In the embodiments of this application, the thermal safety performance and kinetic performance of the battery cell are further improved by doping with the above-mentioned elements.

[0133] In some embodiments, in the cross-section of the layered transition metal oxide particles, the mass contents of Al, Ti, and P elements near the surface are greater than the mass contents of Al, Ti, and P elements near the center.

[0134] In this paper, as an example, lithium titanium aluminum phosphate or lithium aluminum phosphate as shown in Formula II can be diffused from the surface of the layered transition metal oxide particles into the particle interior through solid-phase diffusion, such that the mass contents of Al, Ti and P elements near the surface of the layered transition metal oxide particles are greater than the mass contents of Al, Ti and P elements near the center.

[0135] In the embodiments of this application, the thermal safety performance and dynamic performance of the battery cell are further improved by the element distribution within the above-mentioned range.

[0136] In some embodiments, the layered transition metal oxide particles are doped with Al, Ti, and P elements, wherein in the cross-section of the layered transition metal oxide particles, the molar ratio of Li to P elements near the surface is greater than the molar ratio of Li to P elements near the center.

[0137] In this paper, as an example, lithium titanium aluminum phosphate or lithium aluminum phosphate as shown in Formula II can be diffused from the surface of the layered transition metal oxide particles into the particle interior through solid-phase diffusion, such that in the cross section of the layered transition metal oxide particles, the molar ratio of Li to P elements near the surface is greater than the molar ratio of Li to P elements near the center.

[0138] In the embodiments of this application, the thermal safety performance and dynamic performance of the battery cell are further improved by the element distribution within the above-mentioned range.

[0139] In some embodiments, the layered transition metal oxide particles are doped with Al, Ti and P elements, and M includes one or more of Ni, Co and Mn. In the cross-section of the layered transition metal oxide particles, the molar ratio of Al to Ti near the surface is greater than that near the center.

[0140] In this paper, as an example, lithium titanium aluminum phosphate or lithium aluminum phosphate as shown in Formula II can be diffused from the surface of the layered transition metal oxide particles into the particle interior through solid-phase diffusion, such that in the cross section of the layered transition metal oxide particles, the molar ratio of Al to Ti near the surface is greater than the molar ratio of Al to Ti near the center.

[0141] In the embodiments of this application, the thermal safety performance and dynamic performance of the battery cell are further improved by the element distribution within the above-mentioned range.

[0142] In some embodiments, in the cross-section of the layered transition metal oxide particles, in the outer region 1 μm-3 μm from the surface toward the geometric center, the molar ratio of Al, Ti, and P is (1-2):(0-1):3:3.

[0143] In this paper, the term "geometric center" refers to the center of symmetry of the mass or volume distribution of a particle in all directions of three-dimensional space, and can usually be approximated as the centroid of the particle. In an ideal spherical particle, the geometric center is the center of the sphere. This term is used as a reference point to describe the internal structure or compositional distribution of a particle.

[0144] In this paper, as an example, the above elemental distribution can be achieved by doping lithium titanium aluminum phosphate or lithium aluminum phosphate with the corresponding elemental proportions during the formation of the corresponding regions of layered transition metal oxide particles. The higher the lithium content in lithium titanium aluminum phosphate or lithium aluminum phosphate, the better the lithium replenishment effect.

[0145] In some embodiments, in the cross-section of the layered transition metal oxide particles, within a range of 1.0 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2.0 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3.0 μm, or any range between these values, or any range between these values, the molar ratio of Al, Ti, and P is 1.00:0.0:3, 1.00:0.2:3, 1.00:0.4:3, 1.00:0.6:3, 1.00:0.8:3, 1.00:1.0:3, 1.25:0.0:3, 1.25:0.2:3, ... 1.25:0.4:3, 1.25:0.6:3, 1.25:0.8:3, 1.25:1.0:3, 1.50:0.0:3, 1.50:0.2:3, 1.50:0.4:3, 1.50:0.6:3, 1.50:0.8:3, 1.50:1.0:3, 1.75:0.0:3, 1.75:0.2:3, 1.75:0.4:3, 1.75:0.6:3, 1.75:0.8:3, 1.75:1.0:3, 2.00:0.0:3, 2.00:0.2:3, 2.00:0.4:3, 2.00:0.6:3, 2.00:0.8:3, 2.00:1.0:3.

[0146] In the embodiments of this application, the thermal safety performance and dynamic performance of the battery cell are further improved by the element distribution within the above-mentioned range.

[0147] In some embodiments, in the cross-section of the layered transition metal oxide particles, in the core region with a diameter of 3μm-10μm centered on the geometric center, the molar ratio of Al, Ti, and P is (0.2-1):(1-1.8):3.

[0148] In this paper, as an example, the above elemental distribution can be achieved by doping lithium titanium aluminum phosphate or lithium aluminum phosphate with the corresponding elemental proportions during the formation of the corresponding regions of layered transition metal oxide particles.

[0149] In some embodiments, in the core region of the cross-section of the layered transition metal oxide particles, with a diameter of 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm, 7.0 μm, 8.0 μm, 9.0 μm, 10.0 μm or any value between the two centered on the geometric center, the molar ratio of Al, Ti and P is 0.2:1.0:3, 0.3:1.2:3, 0.4:1.3:3, 0.5:1.4:3, 0.6:1.5:3, 0.7:1.6:3, 0.8:1.7:3, 0.9:1.8:3, 1.0:1.8:3 or any value between the two centered on the geometric center.

[0150] In this embodiment, the elemental distribution within the aforementioned range further improves the thermal safety and kinetic performance of the battery cell. Furthermore, since the oxygen release rate in the core region is relatively low, there is no need to dope with high-lithium-content lithium titanium aluminum phosphate or lithium aluminum phosphate, thereby reducing production costs.

[0151] In some embodiments, in the cross-section of the layered transition metal oxide particles, in the core region with a diameter of 3μm-7μm centered on the geometric center, the molar ratio of Al, Ti, and P is (0.2-0.8):(1.2-1.8):3; in the outer layer region with a diameter of 1μm-3μm from the surface toward the geometric center, the molar ratio of Al, Ti, and P is (1.2-2):(0-0.8):3; and in the intermediate region between the core region and the outer layer region, the thickness is 1μm-3μm, and the molar ratio of Al, Ti, and P in the intermediate region is (0.8-1.2):(0.8-1.2):3.

[0152] In this paper, as an example, the above elemental distribution can be achieved by doping lithium titanium aluminum phosphate or lithium aluminum phosphate with the corresponding elemental proportions during the formation of the corresponding regions of layered transition metal oxide particles.

[0153] In some embodiments, in the cross-section of the lithium-containing layered transition metal oxide particles, in the core region with a diameter of 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm, 7.0 μm or any value between the two centered on the geometric center, the molar ratio of Al, Ti, and P can be 0.2:1.2:3, 0.3:1.3:3, 0.4:1.4:3, 0.5:1.5:3, 0.6:1.6:3, 0.7:1.7:3, 0.8:1.8:3 or any value between the two centered on the geometric center; in the outer region from the surface to the direction towards the geometric center, the molar ratio of Al, Ti, and P can be 1.0 μm, 1.5 μm, 2.0 μm, 2.5 μm, 3.0 μm or any value between the two centered on the geometric center. The molar ratio of Al, Ti, and P can be 1.2:0.0:3, 1.3:0.2:3, 1.4:0.3:3, 1.5:0.4:3, 1.6:0.5:3, 1.7:0.6:3, 1.8:0.7:3, 2.0:0.8:3, or any value range between two of these. The thickness of the intermediate region located between the core region and the outer region is 1.0 μm, 1.5 μm, 2.0 μm, 2.5 μm, 3.0 μm, or any value range between two of these. In the intermediate region, the molar ratio of Al, Ti, and P can be 0.8:0.8:3, 0.9:0.9:3, 1.0:1.0:3, 1.1:1.1:3, 1.2:1.2:3, or any value range between two of these.

[0154] In this embodiment, the elemental distribution within the aforementioned range further improves the thermal safety and kinetic performance of the battery cell. Furthermore, since the oxygen release rate is relatively low in the core and intermediate regions, there is no need to dope with high-lithium-content lithium titanium aluminum phosphate or lithium aluminum phosphate, thereby reducing production costs.

[0155] In some embodiments, the Dv50 of the positive electrode active material is 10μm-15μm.

[0156] In this document, the term "volume average particle size Dv50" has a well-known meaning in the art, referring to the particle size corresponding to a cumulative volume distribution percentage of 50% for the material. The volume distribution particle size Dv50 of the positive electrode active material can be tested 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. The positive electrode active material can be freshly prepared or obtained by scraping powder from the positive electrode film after disassembling a battery cell. For example, the positive electrode sheet is disassembled, and positive electrode film powder is scraped off as the sample to be tested. The sample is then measured according to GB / T19077-2016 / ISO 13320:2009.

[0157] In some embodiments, the Dv50 of the positive electrode active material is 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, or 15 μm.

[0158] In the embodiments of this application, when the Dv50 of the positive electrode active material is within the above-mentioned range, the kinetic performance of the battery cell can be further improved while ensuring thermal safety performance.

[0159] An embodiment of the second aspect of this application provides a method for preparing a positive electrode active material, comprising: coating layered transition metal oxide particles with a solid electrolyte to obtain a coated product; and sintering the coated product once to obtain a positive electrode active material; wherein the solid electrolyte comprises one or more of lithium aluminum titanium phosphate oxide, lithium aluminum phosphate oxide, and tantalum-doped lithium lanthanum zirconium oxide.

[0160] In the embodiments of this application, the cathode material prepared by the above method exhibits good thermal safety performance, kinetic performance, and high energy density. Although the mechanism is not yet clear, experiments suggest that this may be because the first sintering not only ensures the stable coating layer on the particle surface and replenishes lithium on the particle surface, resulting in a higher molar ratio of Li to M near the surface of the layered transition metal oxide particles compared to the particle center; in some cases, it also allows the solid electrolyte to diffuse into the particle interior through solid-phase diffusion, further improving the lithium replenishment effect of the solid electrolyte on the layered transition metal oxide particles, thereby improving the thermal safety performance of the high-energy-density cathode active material. Furthermore, the solid electrolyte used has high ionic conductivity, achieving a balance between good thermal safety performance, kinetic performance, and high energy density.

[0161] In some embodiments, the tantalum-doped lithium lanthanum zirconium oxide has the general formula shown in Formula I, Li 6.4 La3Zr y1 Ta y2 O 12 Equation I, 0 < y1 < 2 and 0 < y2 < 2.

[0162] In this paper, tantalum-doped lithium lanthanum zirconium oxide Li 6.4 La3Zr y1 Ta y2 O 12 This refers to a type of garnet-type solid electrolyte where zirconium is partially replaced by tantalum to optimize crystal structure and ionic conductivity. Ideally, the sum of y1 and y2 should be 2.

[0163] In some embodiments, y1 is a numerical range of 0.2, 0.5, 0.8, 1.1, 1.4, 1.7, or any two of them.

[0164] In some embodiments, y2 is a numerical range of 1.8, 1.5, 1.2, 0.9, 0.6, 0.3, or any two of them.

[0165] In some embodiments, the general formula of the lithium aluminum titanium phosphate oxide is shown in Formula II, Li x1 Al x2 Ti x3 (PO4)3, 1.5≤x1<3, 0.2≤x2<2 and 0≤x3<1.8 Formula II; the lithium aluminum phosphate oxide is Li3Al2(PO4)3.

[0166] In this paper, lithium titanium aluminum oxide Li x1 Al x2 Ti x3 (PO4)3 is a type of NASICON-type solid electrolyte. It can be understood that, ideally, x2 = x1 - 1, x3 = 2 - x2.

[0167] In some embodiments, x1 is a numerical range of 1.5, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, or any two of them.

[0168] In some embodiments, x2 is a numerical range of 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8 or any two of these.

[0169] In some embodiments, x3 is a numerical range of 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.7 or any two of these.

[0170] The applicant's research found that when the solid electrolyte is selected from the above range, it not only has good ionic conductivity, which can improve the thermal safety performance of the battery cell while taking into account the kinetic performance, but also has a good lithium replenishment effect. That is, at high temperature, it replenishes lithium to the deeply delithiated layered transition metal oxide, improves the stability of MO bond, and thus increases the oxygen release temperature of the positive electrode active material, thereby achieving a balance between the thermal safety performance, kinetic performance and high energy density of the battery cell.

[0171] In some embodiments, the layered transition metal oxide particles comprise Li a M b O c The composition includes 0.8 ≤ a < 1, 0.8 < b ≤ 1, 1.5 < c ≤ 2, and M includes one or more of Ni, Co, Mn, and Al.

[0172] In this paper, "Layered transition metal oxides Li a M b O c Alkali metals (Al-I) are a class of inorganic compounds with a layered crystal structure, typically composed of alkali metal ions (such as lithium) embedded between layers of transition metal oxides. Their basic structural unit is a two-dimensional layered framework formed by oxygen-octahedral coordinated transition metals, allowing for reversible insertion and extraction of alkali metal ions between layers. Due to their excellent ionic conductivity and high specific capacity, these materials are widely used in cathode materials for lithium-ion batteries.

[0173] In some embodiments, a is a range of values ​​between 0.8, 0.9, 1.0, 1.1, 1.2, 1.3 or any two of them, b is a range of values ​​between 0.85, 0.90, 0.95, 1.0 or any two of them, and c is a range of values ​​between 1.6, 1.7, 1.8, 1.9, 2.0 or any two of them.

[0174] In some embodiments, Li a M b O c The value is LiCoO2, meaning a is 1, b is 1, and c is 2.

[0175] In some embodiments, Li a M b O c Lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide, such as LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.85 Co 0.1 Mn 0.05 O2, LiNi 0.9 Co 0.05 Mn 0.05 O2, LiNi0.91 Co 0.05 Mn 0.04 O2, LiNi 0.95 Co 0.03 Mn 0.02 O2, etc.

[0176] In some embodiments, based on the mass of the positive electrode active material, the mass percentage of the solid electrolyte is 1.5%-10%.

[0177] In some embodiments, based on the mass of the positive electrode active material, the mass percentage of the solid electrolyte can be 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, 10.0%, or any value range between the two.

[0178] In the embodiments of this application, when the mass ratio of the solid electrolyte is within the above range, the battery cell simultaneously has good thermal safety performance, kinetic performance and high energy density.

[0179] In some embodiments, based on the mass of the positive electrode active material, the mass percentage of the solid electrolyte is 3%-7%.

[0180] In the embodiments of this application, when the mass ratio of the solid electrolyte is within the above range, the battery cell simultaneously has good thermal safety performance, kinetic performance and high energy density.

[0181] In some embodiments, the Dv50 of the positive electrode active material is 10μm-15μm.

[0182] In this document, the term "volume average particle size Dv50" has a well-known meaning in the art, referring to the particle size corresponding to a cumulative volume distribution percentage of 50% for the material. The volume distribution particle size Dv50 of the positive electrode active material can be tested 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. The positive electrode active material can be freshly prepared or obtained by scraping powder from the positive electrode film after disassembling a battery cell. For example, disassembling the battery, taking the positive electrode sheet, scraping the positive electrode film powder as the sample to be tested, and then measuring the sample according to GB / T19077-2016 / ISO 13320:2009.

[0183] In some embodiments, the Dv50 of the positive electrode active material is 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, or 15 μm.

[0184] In the embodiments of this application, when the Dv50 of the positive electrode active material is within the above-mentioned range, the kinetic performance of the battery cell can be further improved while ensuring thermal safety performance.

[0185] In some embodiments, the temperature of the first sintering is 600℃-1000℃.

[0186] In some embodiments, the temperature of the first sintering is 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, or any value between two of these.

[0187] In the embodiments of this application, when the temperature of the first sintering is within the above range, the battery cell has good thermal safety performance, good kinetic performance and high energy density.

[0188] In some embodiments, layered transition metal oxide particles are coated with a solid electrolyte to obtain a coated product; the coated product is then subjected to a single sintering to obtain a positive electrode active material, wherein the solid electrolyte is Li. x1 Al x2 Ti x3 (PO4)3, 1.5≤x1<3, 0.2≤x2<2 and 0≤x3<1.8, or Li3Al2(PO4)3, wherein the positive electrode active material is prepared by sintering in the range of 600℃-1000℃, and the solid electrolyte can play the role of supplementing lithium to the layered transition metal oxide particles under high temperature.

[0189] In some embodiments, layered transition metal oxide particles are coated with a solid electrolyte to obtain a coated product; the coated product is then subjected to a single sintering to obtain a positive electrode active material, wherein the solid electrolyte is Li. 6.4 La3Zr y1 Ta y2 O 12 0 < y1 < 2 and 0 < y2 < 2, wherein the first sintering is in the range of 800℃-1000℃, and in the positive electrode active material prepared, the solid electrolyte can play the role of supplementing lithium to the layered transition metal oxide particles under high temperature.

[0190] In some embodiments, the sintering time is 2h-8h.

[0191] In some embodiments, the sintering time is 2h, 3h, 4h, 5h, 6h, 7h, 8h or any range between the two.

[0192] In the embodiments of this application, when the sintering time is within the above range, the battery cell has good thermal safety performance, good kinetic performance and high energy density.

[0193] A third aspect of this application provides a method for preparing a positive electrode active material, comprising: heat-treating a first mixture containing a layered transition metal oxide precursor to obtain a sintered product; mixing the sintered product with a solid electrolyte and performing a second heat treatment to obtain the positive electrode active material, wherein the solid electrolyte comprises one or more of lithium aluminum titanium phosphate and lithium aluminum phosphate.

[0194] In the embodiments of this application, the cathode material prepared by the above method exhibits good thermal safety performance, kinetic performance, and high energy density. Although the mechanism is not yet clear, experiments suggest that this may be because a solid electrolyte is added during the formation of the layered transition metal oxide and sintered together. This allows the solid electrolyte to be doped into the interior of the layered transition metal oxide particles, resulting in a higher molar ratio of Li to M near the surface of the particles compared to the ratio near the particle center. This further enhances the lithium replenishment effect of the solid electrolyte on the layered transition metal oxide particles, thereby improving the thermal safety performance of the high-energy-density cathode active material. Furthermore, the solid electrolyte used has high ionic conductivity, achieving a balance between good thermal safety performance, kinetic performance, and high energy density.

[0195] In some embodiments, the general formula of the lithium aluminum titanium phosphate oxide is shown in Formula II, Li x1 Al x2 Ti x3 (PO4)3, 1.5≤x1<3, 0.2≤x2<2 and 0≤x3<1.8 Formula II; the lithium aluminum phosphate oxide is Li3Al2(PO4)3.

[0196] In some embodiments, x1 is a numerical range of 1.5, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, or any two of them.

[0197] In some embodiments, x2 is a numerical range of 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8 or any two of these.

[0198] In some embodiments, x3 is a numerical range of 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.7 or any two of these.

[0199] The applicant's research found that when the solid electrolyte is selected from the above range, it not only has good ionic conductivity, which can improve the thermal safety and kinetic performance of the positive electrode active material, but also has a good lithium replenishment effect. That is, at high temperature, it replenishes lithium to the deeply delithiated layered transition metal oxide, improves the stability of MO bond, and thus increases the oxygen release temperature of the positive electrode active material, thereby achieving a balance between thermal safety, kinetic performance and high energy density.

[0200] In some embodiments, the layered transition metal oxide includes the general formula Li a M b O c The composition includes 0.8 ≤ a < 1, 0.8 < b ≤ 1, 1.5 < c ≤ 2, and M includes one or more of Ni, Co, Mn, and Al.

[0201] In this paper, "Layered transition metal oxides Li a M b O c Alkali metals (Al-I) are a class of inorganic compounds with a layered crystal structure, typically composed of alkali metal ions (such as lithium) embedded between layers of transition metal oxides. Their basic structural unit is a two-dimensional layered framework formed by oxygen-octahedral coordinated transition metals, allowing for reversible insertion and extraction of alkali metal ions between layers. Due to their excellent ionic conductivity and high specific capacity, these materials are widely used in cathode materials for lithium-ion batteries.

[0202] In some embodiments, a is a range of values ​​between 0.8, 0.9, 1.0, 1.1, 1.2, 1.3 or any two of them, b is a range of values ​​between 0.85, 0.90, 0.95, 1.0 or any two of them, and c is a range of values ​​between 1.6, 1.7, 1.8, 1.9, 2.0 or any two of them.

[0203] In some embodiments, Li a M b O c The value is LiCoO2, meaning a is 1, b is 1, and c is 2.

[0204] In some embodiments, Li a M b O c Lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide, such as LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.85 Co 0.1 Mn0.05 O2, LiNi 0.9 Co 0.05 Mn 0.05 O2, LiNi 0.91 Co 0.05 Mn 0.04 O2, LiNi 0.95 Co 0.03 Mn 0.02 O2, etc.

[0205] In some embodiments, based on the mass of the positive electrode active material, the mass percentage of the solid electrolyte added before the second heat treatment is 1.5%-10%.

[0206] In this paper, it can be understood that the solid electrolyte introduced before the second heat treatment is doped into the positive electrode active material through the second heat treatment.

[0207] In some embodiments, based on the mass of the positive electrode active material, the mass percentage of the solid electrolyte added before the second heat treatment can be 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, 10.0%, or any value range between the two.

[0208] In the embodiments of this application, by introducing a solid electrolyte before the second heat treatment, the prepared positive electrode active material has good thermal safety performance, kinetic performance and high energy density.

[0209] In some embodiments, the temperature of the heat treatment is 600℃-1000℃, the time of the heat treatment is 6h-10h, the temperature of the second heat treatment is 800℃-1000℃, and the time of the second heat treatment is 2h-8h.

[0210] In some embodiments, the temperature of the heat treatment is 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, or any range between two of these values; the time of the heat treatment is 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, 10h, or any range between two of these values; the temperature of the second heat treatment is 800°C, 825°C, 850°C, 875°C, 900°C, 925°C, 950°C, 975°C, 1000°C, or any range between two of these values; and the time of the second heat treatment is 2h, 3h, 4h, 5h, 6h, 7h, 8h, or any range between two of these values.

[0211] In the embodiments of this application, the positive electrode active material prepared under the above heat treatment conditions has good thermal safety performance, kinetic performance and high energy density.

[0212] In some embodiments, the first mixture also includes a solid electrolyte, and the mass percentage of the solid electrolyte added to the first mixture is 0.1%-10% based on the mass of the positive electrode active material.

[0213] In this paper, it can be understood that since the particles of the positive electrode active material gradually increase in size, the earlier the solid electrolyte is added, the closer the added electrolyte is to the center of the particles. That is, the solid electrolyte added in the first mixture is closer to the center of the particles than the solid electrolyte added before the second sintering.

[0214] In some embodiments, the first mixture also includes a solid electrolyte, and the mass percentage of the solid electrolyte added to the first mixture, based on the mass of the positive electrode active material, is 0.1%, 0.3%, 0.5%, 0.8%, 1.0%, 1.5%, 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, 10.0%, or any value range between the two.

[0215] In the embodiments of this application, by adding solid electrolytes within the above-mentioned mass ratio range to the first mixture, the prepared positive electrode active material has good thermal safety performance, kinetic performance and high energy density.

[0216] In some embodiments, the solid electrolyte includes one or more of lithium aluminum titanium phosphate and lithium aluminum phosphate, wherein the molar ratio of Li to phosphorus in the solid electrolyte added before the second heat treatment is greater than the molar ratio of Li to phosphorus in the solid electrolyte added before the heat treatment.

[0217] In this paper, it can be understood that since the particles of the positive electrode active material gradually increase in size, the earlier the solid electrolyte is added, the closer the added electrolyte is to the center of the particle. In other words, the solid electrolyte added before heat treatment is closer to the center of the particle than the solid electrolyte added before the second sintering.

[0218] In this embodiment, since the degree of oxygen release inside the particles is relatively low, doping with lithium titanium aluminum phosphate oxide with a lower Li content at a position closer to the inside of the particles can reduce the cost of the material while ensuring good thermal safety performance, kinetic performance and high energy density.

[0219] In some embodiments, the heat treatment of the first mixture containing the layered transition metal oxide precursor to obtain a sintered product comprises: performing a first heat treatment on the first mixture containing the layered transition metal oxide precursor, and then performing a second heat treatment on the mixture and a solid electrolyte to obtain a sintered product.

[0220] In the embodiments of this application, the positive electrode active material prepared under the above heat treatment conditions has good thermal safety performance, kinetic performance and high energy density.

[0221] In some embodiments, the first mixture includes a solid electrolyte, wherein the molar ratio of Li to P in the solid electrolyte added before the re-heat treatment is greater than the molar ratio of Li to P in the first mixture.

[0222] In this paper, it can be understood that since the particles of the positive electrode active material gradually increase in size, the earlier the solid electrolyte is added, the closer the added electrolyte is to the center of the particle.

[0223] In this embodiment, since the degree of oxygen release inside the particles is relatively low, doping with lithium titanium aluminum phosphate oxide with a lower Li content at a position closer to the inside of the particles can reduce the cost of the material while ensuring good thermal safety performance, kinetic performance and high energy density.

[0224] In some embodiments, based on the mass of the positive electrode active material, the mass percentage of the solid electrolyte added before the second heat treatment is 0.1%-10%.

[0225] In some embodiments, based on the mass of the positive electrode active material, the mass percentage of the solid electrolyte added before the second heat treatment is 0.1%, 0.3%, 0.5%, 0.8%, 1.0%, 1.5%, 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, 10.0%, or any value range between the two.

[0226] In the embodiments of this application, by adding solid electrolytes within the above-mentioned mass ratio range before re-heat treatment, the prepared positive electrode active material has good thermal safety performance, kinetic performance and high energy density.

[0227] In some embodiments, the temperature of the first heat treatment is 700°C-900°C, and the temperature of the second heat treatment is 800°C-1000°C.

[0228] In some embodiments, the temperature of the first heat treatment is 700°C, 720°C, 740°C, 760°C, 780°C, 800°C, 820°C, 840°C, 860°C, 880°C, 900°C or any range between two of these values, and the temperature of the second heat treatment is 800°C, 820°C, 840°C, 860°C, 880°C, 900°C, 920°C, 940°C, 960°C, 980°C, 1000°C or any range between two of these values.

[0229] In the embodiments of this application, the positive electrode active material prepared under the above heat treatment conditions has good thermal safety performance, kinetic performance and high energy density.

[0230] An embodiment of the fourth aspect of this application provides a battery device comprising a battery cell as described in any of the embodiments of the first aspect or a battery cell obtained by the preparation method described in any of the embodiments of the second or third aspect. The battery device includes one or more of a battery module, a battery pack, and an energy storage battery.

[0231] An embodiment of the fifth aspect of this application provides an electrical device that includes the battery device in any of the embodiments of the fourth aspect described above, the battery device being used to provide electrical energy.

[0232] An embodiment of the sixth aspect of this application provides an energy storage device, which includes the battery device of any of the embodiments of the fourth aspect described above, the battery device being used to store electrical energy.

[0233] Typically, a battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0234] [Positive electrode plate]

[0235] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including the positive electrode active material of the first aspect of this application.

[0236] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0237] 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.).

[0238] In some embodiments, the positive electrode film 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.

[0239] In some embodiments, the positive electrode film 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.

[0240] 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.

[0241] [Negative electrode plate]

[0242] 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.

[0243] 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.

[0244] 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.).

[0245] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in battery cells. 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 battery negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0246] In some embodiments, the negative electrode film layer may optionally include an adhesive. The adhesive 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).

[0247] 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.

[0248] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0249] 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 a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0250] [Electrolytes]

[0251] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0252] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0253] 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.

[0254] 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.

[0255] 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.

[0256] [Isolation membrane]

[0257] 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.

[0258] 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.

[0259] The battery cells disclosed in this application can be used, but are not limited to, in electrical devices or energy storage devices such as vehicles, ships, or aircraft. A power system comprising the battery cells and battery devices disclosed in this application can be used to construct such an electrical device or energy storage device. This helps to alleviate lithium plating on the negative electrode of high-energy-density batteries, improving battery performance stability and battery life.

[0260] This application provides an electrical device that uses a battery as a power source. The electrical device can be, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0261] This application also provides an energy storage device that uses a battery as a power source. The energy storage device can be, but is not limited to, an energy storage container, an energy storage cabinet, an energy storage power station, an energy storage battery pack, or a portable energy storage system.

[0262] For ease of explanation, the following embodiments will be described using a vehicle 1000 as an example of an electrical device according to an embodiment of this application.

[0263] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of a vehicle provided in some embodiments of this application. The vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A battery device 100 is installed inside the vehicle 1000, and the battery device 100 can be located at the bottom, front, or rear of the vehicle 1000. The battery device 100 can be used to power the vehicle 1000; for example, the battery device 100 can serve as the operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery device 100 to supply power to the motor 300, for example, to meet the power needs of the vehicle 1000 during starting, navigation, and driving.

[0264] In some embodiments of this application, the battery device 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0265] Please refer to Figure 2 , Figure 2This is an exploded structural diagram of a battery device provided in some embodiments of this application. The battery device 100 includes a housing 10 and a battery cell 20, with the battery cell 20 housed within the housing 10. The housing 10 provides a space for the battery cell 20 and can have various structures. In some embodiments, the housing 10 may include a first portion 11 and a second portion 12, which overlap each other, jointly defining a space for accommodating the battery cell 20. The second portion 12 may be a hollow structure with one open end, and the first portion 11 may be a plate-like structure, covering the open side of the second portion 12 so that the first portion 11 and the second portion 12 jointly define the space. Alternatively, the first portion 11 and the second portion 12 may both be hollow structures with one open side, with the open side of the first portion 11 covering the open side of the second portion 12. Of course, the housing 10 formed by the first portion 11 and the second portion 12 can have various shapes, such as a cylinder, a cuboid, etc.

[0266] In the battery device 100, there can be multiple battery cells 20, which can be connected in series, parallel, or in a mixed configuration. A mixed configuration means that multiple battery cells 20 are connected in both series and parallel connections. Multiple battery cells 20 can be directly connected in series, parallel, or in a mixed configuration, and then the entire assembly of the multiple battery cells 20 is housed within the housing 10. Alternatively, the battery device 100 can also consist of multiple battery cells 20 first connected in series, parallel, or in a mixed configuration to form battery modules, and then these battery modules are connected in series, parallel, or in a mixed configuration to form a whole, which is also housed within the housing 10. The battery device 100 may also include other structures; for example, it may include a busbar component for electrical connection between the multiple battery cells 20.

[0267] Each battery cell 20 can be a secondary battery or a primary battery; it can also be a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited to these. The battery cell 20 can be cylindrical, flat, cuboid, or other shapes.

[0268] Please refer to Figure 3 , Figure 3 This is an exploded structural diagram of a battery cell provided in some embodiments of this application. The battery cell 20 refers to the smallest unit that makes up a battery device. For example... Figure 3 The battery cell 20 includes an end cap 21, a housing 22, an electrode assembly 23, and other functional components.

[0269] End cap 21 refers to a component that covers the opening of housing 22 to isolate the internal environment of battery cell 20 from the external environment. The shape of end cap 21 can be adapted to the shape of housing 22 to fit it. Optionally, end cap 21 can be made of a material with certain hardness and strength (such as aluminum alloy), so that end cap 21 is not easily deformed under pressure and impact, giving battery cell 20 higher structural strength and improved safety performance. Functional components such as electrode terminals 21a can be provided on end cap 21. Electrode terminals 21a can be used for electrical connection with electrode assembly 23 for outputting or inputting electrical energy into battery cell 20. In some embodiments, end cap 21 can also be provided with a pressure relief mechanism for releasing internal pressure when the internal pressure or temperature of battery cell 20 reaches a threshold. The material of end cap 21 can also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc. In some embodiments, an insulating element may be provided on the inner side of the end cap 21. The insulating element can be used to isolate the electrical connection components within the housing 22 from the end cap 21 to reduce the risk of short circuits. For example, the insulating element may be made of plastic, rubber, etc.

[0270] The housing 22 is a component used to cooperate with the end cap 21 to form the internal environment of the battery cell 20. This internal environment can accommodate the electrode assembly 23, electrolyte, and other components. The housing 22 and the end cap 21 can be independent components. An opening can be provided on the housing 22, and the end cap 21 closes the opening to form the internal environment of the battery cell 20. Alternatively, the end cap 21 and the housing 22 can be integrated. Specifically, the end cap 21 and the housing 22 can form a common connecting surface before other components are inserted into the housing. When it is necessary to encapsulate the interior of the housing 22, the end cap 21 closes the housing 22. The housing 22 can be of various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shape of the housing 22 can be determined according to the specific shape and size of the electrode assembly 23. The housing 22 can be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc.

[0271] Electrode assembly 23 is the component in the battery cell 20 where electrochemical reactions occur. The casing 22 may contain one or more electrode assemblies 23. The electrode assembly 23 is mainly formed by winding or stacking positive and negative electrode plates, and typically a separator is provided between the positive and negative electrode plates. The portions of the positive and negative electrode plates containing active material constitute the main body of the electrode assembly, while the portions of the positive and negative electrode plates without active material each constitute a tab 23a. The positive and negative tabs may be located together at one end of the main body or separately at both ends of the main body. During the charging and discharging process of the battery, the positive and negative active materials react with the electrolyte, and the tabs 23a connect to the electrode terminals to form a current loop.

[0272] 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.

[0273] I. Preparation Example

[0274] 1. Preparation of lithium titanium aluminum phosphate / lithium aluminum phosphate (LATP)

[0275] Li was placed in an argon-protected glove box. 1.2 Al 0.2 Ti 1.8 Li₂ was prepared by mixing (PO₄)₃ with a certain amount of lithium metal powder and heating the mixture at 300°C on a heating stage. 1.5 Al 0.5 Ti 1.5 (PO4)3, Li2AlTi(PO4)3, Li 2.5 Al 1.5 Ti 0.5 (PO4)3, Li3Al2(PO4)3, the specific reaction conditions are as follows:

[0276] Control of Li in the mixture 1.2 Al 0.2 Ti 1.8 Li was prepared by mixing (PO4)3 and lithium metal in a molar ratio of 1:0.4 and maintaining the mixture at 300°C for 40 min under an argon atmosphere. 1.5 Al 0.5 Ti 1.5 (PO4)3;

[0277] Control of Li in the mixture 1.2 Al 0.2 Ti 1.8 The molar ratio of (PO4)3 to lithium metal was 1:1. Li2AlTi(PO4)3 was prepared by holding it at 300℃ for 70 min under an argon atmosphere.

[0278] Control of Li in the mixture 1.2 Al 0.2 Ti 1.8 Li was prepared by mixing (PO4)3 and lithium metal in a molar ratio of 1:1.8 and maintaining the mixture at 300°C for 110 min under an argon atmosphere. 2.5 Al 1.5 Ti 0.5 (PO4)3;

[0279] Control of Li in the mixture1.2 Al 0.2 Ti 1.8 Li3Al2(PO4)3 was prepared by mixing (PO4)3 with lithium metal in a molar ratio of 1:2.4 and holding the mixture at 300℃ for 150 min under an argon atmosphere.

[0280] 2. Preparation of positive electrode active materials

[0281] 2.1 Preparation of Comparative Examples 1-3 and Preparation Examples 1-19

[0282] Using N-methylpyrrolidone (NMP) as a solvent, NMP was mixed with a solid electrolyte to prepare a solid electrolyte sol with a mass concentration of 50%-70%; the obtained sol was then mixed with a ternary material (LiNi). 0.9 Co 0.05 Mn 0.05 After thorough mixing with O2, a single sintering process is performed to obtain the positive electrode active material. The specific parameters are shown in Table 1 below.

[0283] Table 1

[0284]

[0285] 2.2 Preparation Examples 20-22

[0286] 2.21 Preparation Example 20

[0287] Inner layer: using ternary material (LiNi) 0.9 Co 0.05 Mn 0.05 O2) precursors and Li 1.5 Al 0.5 Ti 1.5 (PO4)3 (based on the mass of the positive electrode active material, with a mass ratio of 1.33%) was mixed and subjected to a first heat treatment (900℃, 8h) to obtain the first product;

[0288] Middle layer: The first product is mixed with Li2AlTi(PO4)3 (based on the mass of the positive electrode active material, the mass ratio is 1.33%), and subjected to a second heat treatment (900℃, 5h) to obtain the second product;

[0289] Outer layer: The second product is reacted with Li 2.5 Al 1.5 Ti 0.5 (PO4)3 (based on the mass of the positive electrode active material, with a mass ratio of 1.33%) was mixed and subjected to a third heat treatment (900℃, 5h) to obtain the positive electrode active material.

[0290] 2.22 Preparation Example 21

[0291] Inner layer: using ternary material (LiNi)0.9 Co 0.05 Mn 0.05 O2) precursors and Li 1.5 Al 0.5 Ti 1.5 (PO4)3 (based on the mass of the positive electrode active material, with a mass ratio of 2.5%) was mixed and subjected to a first heat treatment (900℃, 8h) to obtain the first product;

[0292] Outer layer: The first product is mixed with Li2AlTi(PO4)3 (based on the mass of the positive electrode active material, the mass ratio is 2.5%) and subjected to a second heat treatment (900℃, 5h) to obtain the positive electrode active material.

[0293] 2.23 Preparation Example 22

[0294] Inner layer: for ternary materials (LiNi) 0.9 Co 0.05 Mn 0.05 The precursor of O2 was subjected to a first heat treatment (900℃, 8h) to obtain the sintered product;

[0295] Outer layer: The sintered product is combined with Li 2.5 Al 1.5 Ti 0.5 (PO4)3 (5% by mass based on the mass of the positive electrode active material) is mixed and subjected to a second heat treatment (900℃, 5h) to obtain the positive electrode active material.

[0296] II. Implementation Examples

[0297] Example 1

[0298] (1) Preparation of positive electrode sheet

[0299] Preparation of positive electrode slurry:

[0300] The positive electrode active material prepared in Preparation Example 1, conductive agent CNT, conductive agent SP, binder PVDF, surfactant (polyvinylpyrrolidone), and solvent NMP were uniformly mixed in a weight ratio of 98.04 : 0.5 : 0.5 : 0.9 : 0.06 : 80, coated on both sides of aluminum foil, and then cold-pressed and cut to obtain the positive electrode sheet.

[0301] (2) Preparation of negative electrode sheet

[0302] Silicon carbide material, conductive carbon black, conductive agent CNT, binder SBR, carboxymethyl cellulose (CMC), and solvent deionized water are uniformly mixed in a weight ratio of 79.83:9.67:0.5:8.8:1.2:50, coated on both sides of copper foil, and then cold-pressed and cut to obtain the negative electrode sheet.

[0303] (3) Separating membrane

[0304] A polyethylene film with a thickness of 13 μm was used as the separator.

[0305] (4) Preparation of electrolyte

[0306] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), lithium hexafluorophosphate (LiPF6) was dissolved in organic solvents ethylene carbonate, diethyl carbonate, and dimethyl carbonate (volume ratio 1:1:1) and stirred until homogeneous to obtain an electrolyte with a LiPF6 concentration of 1 mol / L.

[0307] (5) Preparation of battery cells

[0308] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The cells are then wound together to obtain the battery cell. The battery cell is then welded with tabs and installed in an aluminum casing. Electrolyte is then injected and the casing is sealed. After processes such as settling, cold pressing, formation, shaping, and capacity testing, a lithium-ion secondary battery is obtained.

[0309] Example 2-22

[0310] The battery preparation methods in Examples 2-22 are basically the same as those in Example 1, except that the preparation methods of the positive electrode active material are different, and the positive electrode active materials prepared in Examples 2-22 are used respectively.

[0311] Comparative Examples 1-3

[0312] The battery preparation methods of Comparative Examples 1-3 are basically the same as those of Example 1, except that the preparation methods of the positive electrode active materials are different, and the positive electrode active materials prepared by Comparative Examples 1-3 are used respectively.

[0313] Comparative Example 4

[0314] The battery preparation method of Comparative Example 4 is basically the same as that of Example 1, except that the preparation method of the positive electrode active material is different, using LiNi 0.9 Co 0.05 Mn 0.05 O2 is used as the positive electrode active material to prepare battery cells.

[0315] III. Battery Performance Testing

[0316] (1) DSC test

[0317] At 25℃, the battery cells were charged at a constant current of 0.5C to a cutoff voltage of 4.35V, and then charged at a constant voltage of 4.35V to 0.05C. The fully charged battery cells were disassembled to obtain the fully charged positive and negative electrode sheets, which were then cleaned. The electrode sheets were then cut into small round pieces with a diameter of 5mm and placed in a stainless steel sealed crucible commonly used in DSC (Differential Scanning Calorimeter) equipment. 1.5μL of the appropriate electrolyte was injected, and the threads of the sealed crucible were tightened. Finally, the crucible was placed in a Netzsch DSC300 Caliris Classic instrument for testing, with a heating rate of 10℃ / min and a temperature range of 30℃-460℃. Based on the test results, the vertical axis of the DSC curve represents the heat generation rate in mW, and the area of ​​the DSC curve integrated with the horizontal axis represents the heat generation.

[0318] (2) Thermal safety test

[0319] At 25℃, the battery cells are charged at a constant current of 0.5C to the cutoff voltage of 4.35V, and then charged at a constant voltage of 4.35V to 0.05C. The fully charged battery cells are then fixed to the large surface area using a heating plate (JK-HP-180A / 180B), and a 220V / 3A signal is input to the heating plate to heat the battery cells at this constant power until the hard-shell cell fails or the heating time reaches 2 hours. The thermal runaway test is passed if the cell's safety valve is opened directionally without cracking of the large surface or side casing. If no thermal runaway occurs after 2 hours of heating, the thermal safety test is passed.

[0320] (3) Dynamic performance test

[0321] At 25°C, the battery cells were charged at a constant current of 0.5C to a cutoff voltage of 4.35V, and then charged at a constant voltage of 4.35V to 0.05C. They were then discharged at a constant current of 0.02C to a cutoff voltage of 2.5V, and the full discharge capacity C0 of the battery cells was recorded.

[0322] At 25°C, the battery cells were charged at a constant current of 0.5C to a cutoff voltage of 4.35V, and then charged at a constant voltage of 4.35V to 0.05C. They were then discharged at a constant current of 2C to a cutoff voltage of 2.5V, and the full discharge capacity C1 of the battery cells was recorded.

[0323] The 2C discharge capacity retention rate of a single battery cell is calculated using the formula: 2C discharge capacity retention rate = (C1 / C0) × 100% to evaluate the kinetic performance of the battery cell.

[0324] (4) Weight energy density

[0325] The battery cells were left to stand at 25°C for 2 hours. Then, at 25°C, they were charged at 0.33C (0.33C) to the charging cutoff voltage of 4.35V. After standing for 10 minutes, they were charged at a constant voltage of 4.35V until the current reached 0.05C, at which point charging was stopped. The battery cells were then left to stand at 25°C for 1 hour. Then, at 25°C, they were discharged at 0.33C to the discharge cutoff voltage of 2.5V. The total discharge energy of the battery cells was recorded as E0 (Wh). The weight of the battery cells was measured as M0 (kg). The weight energy density of the battery cells = discharge energy E0 / weight M0 (Wh / kg).

[0326] IV. Analysis of Test Results for Each Embodiment and Comparative Example

[0327] The performance parameters of the positive electrode active material and the battery cell were measured according to the above method, and the DSC test results are as follows: Figure 4 As shown, the results of thermal safety performance and kinetic performance are shown in Tables 2-5 below.

[0328] Table 2

[0329]

[0330] Figure 4 The results are the DSC test results for Comparative Examples 4, 1, 7, and 21 of this application. Figure 4 As can be seen, compared with Comparative Example 4, Examples 1, 7, and 21 can all reduce the heat generation of the battery cell or increase the critical temperature for thermal runaway of the battery cell.

[0331] The positive electrode active materials prepared in the examples were characterized by scanning electron microscopy and energy dispersive spectroscopy. The results showed that in the cross-section of the layered transition metal oxide particles, the total molar ratio of Li to M elements (Ni, Co, Mn) near the surface was greater than that near the particle center. In contrast, in the comparative examples, the total molar ratio of Li to M elements (Ni, Co, Mn) near the surface of the layered transition metal oxide particles was less than or equal to that near the particle center. The experimental results indicate that the battery cells in the examples of this application have better thermal safety performance.

[0332] The gravimetric energy density of the battery cell in Example 1, measured using the method described above, is 426 Wh / kg. Experimental results indicate that the battery cell in this embodiment possesses high energy density.

[0333] As can be seen from Comparative Examples 1-4 and Examples 1, 3 and 5, coating the surface of layered transition metal oxide particles with tantalum-doped lithium lanthanum zirconium oxide (Li) is a highly effective method. 6.4 La3Zr y1 Ta y2 O 12 0 < y1 < 2 and 0 < y2 < 2, Lithium aluminum titanium phosphate oxide Li x1 Al x2 Ti x3 (PO4)3, 1.5≤x1<3, 0.2≤x2<2 and 0≤x3<1.8 or lithium aluminum phosphate oxide LiAl3Ti2(PO4)3 and sintering can significantly improve the thermal safety performance of battery cells while taking into account kinetic performance.

[0334] As can be seen from Examples 1-6, when the primary sintering temperature is between 600℃ and 900℃, the thermal safety performance of the battery cell can be significantly improved while taking into account the kinetic performance.

[0335] Table 3

[0336]

[0337] As shown in Examples 8-11, when the solid electrolyte mass percentage is in the range of 1.5%-10%, the battery cell exhibits good thermal safety and kinetic performance. When the solid electrolyte mass percentage is in the range of 3%-7%, the battery cell achieves a better thermal safety test pass rate while maintaining good kinetic performance.

[0338] Table 4

[0339]

[0340] As shown in Examples 12-19, this application provides a method for preparing a positive electrode active material, comprising: coating layered transition metal oxide particles with a solid electrolyte to obtain a coated product; and sintering the coated product once to obtain the positive electrode active material; wherein the solid electrolyte includes one or more of lithium aluminum titanium phosphate oxide, lithium aluminum phosphate oxide, and tantalum-doped lithium lanthanum zirconium oxide. The positive electrode active material prepared by this method has good thermal safety performance, kinetic performance, and high energy density.

[0341] As can be seen from Examples 8-11, when the primary sintering temperature is 800℃-1000℃ and the primary sintering time is within the range of 2h-8h, the battery cells have a better thermal safety test pass rate while ensuring kinetic performance.

[0342] Table 5

[0343]

[0344] As shown in Examples 20-22, this application provides a method for preparing a cathode material, comprising: heat-treating a first mixture containing a layered transition metal oxide precursor to obtain a sintered product; mixing the sintered product with a solid electrolyte and performing a second heat treatment to obtain a cathode active material, wherein the solid electrolyte includes one or more of lithium aluminum titanium phosphate and lithium aluminum phosphate. The cathode active material prepared by this method has good thermal safety performance, kinetic performance, and high energy density.

[0345] As can be seen from Comparative Example 4 and Example 22, the positive electrode active material prepared in the embodiments of this application has good thermal safety performance, kinetic performance and high energy density.

[0346] As can be seen from Comparative Example 4 and Example 21, the positive electrode active material prepared in the embodiments of this application has good thermal safety performance, kinetic performance and high energy density, and reduces production costs.

[0347] As can be seen from Comparative Example 4 and Example 20, the positive electrode active material prepared in the embodiments of this application has good thermal safety performance, kinetic performance and high energy density, and further reduces production costs.

[0348] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, characterized in that, The battery cell includes a positive electrode sheet, which includes a positive current collector and a positive electrode film layer disposed on at least one side of the surface of the positive current collector. The positive electrode film layer includes a positive electrode active material, which includes layered transition metal oxide particles, and the layered transition metal oxide particles include particles with the general formula Li. a M b O c The composition includes 0.8 ≤ a ≤ 1.3, 0.8 < b ≤ 1, 1.5 < c ≤ 2, and M includes one or more of Ni, Co, Mn, and Al. In the cross-section of the layered transition metal oxide particles, the molar ratio of Li to M elements near the surface is greater than that near the particle center. The layered transition metal oxide particles described herein satisfy one or two of the following conditions: (1) The surface of the layered transition metal oxide particles is further provided with a coating layer, the coating layer comprising a solid electrolyte, the solid electrolyte comprising lithium titanium aluminum phosphate oxide, the general formula of which is shown in Formula II, Li x1 Al x2 Ti x3 (PO4)3, 2≤x1<3, 0.2≤x2<2 and 0<x3<1.8 Equation II; (2) The layered transition metal oxide particles are doped with a solid electrolyte, which includes one or more of lithium titanium aluminum phosphate and lithium aluminum phosphate. The general formula of the lithium titanium aluminum phosphate is shown in Formula III. x4 Al x5 Ti x6 (PO4)3, 1.5≤x4<3, 0.2≤x5<2 and 0<x6<1.8 Formula III; the lithium aluminum phosphate oxide is Li3Al2(PO4)3, wherein in the cross section of the layered transition metal oxide particles, the molar ratio of Li to P near the surface is greater than the molar ratio of Li to P near the center.

2. The battery cell according to claim 1, characterized in that, The thickness of the coating layer is from 0.02 μm to 2 μm.

3. The battery cell according to claim 1, characterized in that, When the layered transition metal oxide particles satisfy condition (2), in the cross section of the layered transition metal oxide particles, in the outer layer region from the surface to the geometric center in the direction of 1μm-3μm, the molar ratio of Al, Ti and P elements is (1-2):(0-1):

3.

4. The battery cell according to claim 1, characterized in that, When the layered transition metal oxide particles satisfy condition (2), in the cross section of the layered transition metal oxide particles, in the core region with a diameter of 3μm-10μm centered on the geometric center, the molar ratio of Al, Ti and P elements is (0.2-1):(1-1.8):

3.

5. The battery cell according to claim 1, characterized in that, When the layered transition metal oxide particles satisfy condition (2), in the core region with a diameter of 3μm-7μm centered on the geometric center of the layered transition metal oxide particles, the molar ratio of Al, Ti and P elements is (0.2-0.8):(1.2-1.8):

3. In the outer region 1 μm-3 μm from the surface toward the geometric center, the molar ratio of Al, Ti, and P is (1.2-2):(0-0.8):3; The thickness of the intermediate region located between the core region and the outer region is 1μm-3μm, and the molar ratio of Al, Ti and P elements in the intermediate region is (0.8-1.2):(0.8-1.2):

3.

6. The battery cell according to claim 1, characterized in that, The Dv50 of the positive electrode active material is 10μm-15μm.

7. A battery device, characterized in that, Includes the battery cell as described in any one of claims 1 to 6.

8. An electrical device, characterized in that, The electrical device includes the battery device as described in claim 7, the battery device being used to provide electrical energy.

9. An energy storage device, characterized in that, The energy storage device includes the battery device as described in claim 7, the battery device being used to store electrical energy.

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