Composite positive electrode material and preparation method therefor, positive electrode, battery and electric device

Abstract

A composite positive electrode material and a preparation method therefor, a positive electrode, a battery and an electric device. The composite positive electrode material comprises a core body and coating layer, wherein the core body contains a lithium-rich manganese-based positive electrode material; and at least part of the surface of the core body is coated with the coating layer, and the coating layer comprises a perovskite material and a fast ion conductor material.

Description

Composite positive electrode material and preparation method thereof, positive electrode, battery and electrical device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202410268464.4 filed on March 8, 2024, entitled “Composite positive electrode material and preparation method thereof, positive electrode, battery and electrical device,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application belongs to the field of battery technology, and specifically relates to a composite positive electrode material and a preparation method thereof, a positive electrode, a battery, and an electrical device. Background Art

[0004] Lithium-ion batteries, due to their high energy density and low self-discharge, are rapidly gaining popularity in electric vehicles, consumer electronics, and energy storage devices. As lithium-ion battery applications become more widespread, the requirements for their electrochemical properties, such as cycle performance, are becoming increasingly stringent.

[0005] The cathode material of lithium-ion batteries has a significant impact on the battery's electrochemical performance. For example, lithium-rich manganese-based cathode materials not only impart high energy density to batteries, but also significantly influence cycling performance. However, lithium-rich manganese-based cathode materials have poor cycling stability, which can easily degrade the cycling and storage performance of battery cells. Summary of the Invention

[0006] In view of the above problems, the present application provides a composite positive electrode material and a preparation method thereof, a positive electrode, a battery and an electrical device to improve the battery cycle performance and storage performance.

[0007] In a first aspect, an embodiment of the present application provides a composite positive electrode material, which includes a core body and a coating layer, wherein the core body contains a lithium-rich manganese-based positive electrode material; the coating layer is coated on at least a portion of the surface of the core body, and the coating layer includes a perovskite material and a fast ion conductor material.

[0008] Therefore, the embodiment of the present application can significantly improve the modification effect of the coating layer on the lithium-rich manganese-based positive electrode material by coating the lithium-rich manganese-based positive electrode material with the perovskite material and the fast ion conductor material, and improve the crystal structure stability of the composite positive electrode material and the interface stability between the composite positive electrode material and the electrolyte, thereby significantly improving the electrochemical properties of the battery, such as the cycle performance and storage performance. The perovskite material and the fast ion conductor material work together to change the performance of the coating layer. The coating layer can effectively mitigate the deoxidation effect, so that the lattice structure stability of the lithium-rich manganese-based positive electrode material can be effectively improved, thereby improving the cycle performance and storage performance of the battery. On the other hand, the perovskite material and the fast ion conductor material work together, and the coating layer can effectively reduce the risk of side reactions between the perovskite material and the active lithium; it can also further improve the kinetic performance, which is beneficial to improving the first-cycle coulomb efficiency of the battery.

[0009] In some embodiments, based on the total mass of the composite positive electrode material, the ratio of the mass content of the perovskite material to the mass content of the core body is (0.2 to 0.8): 100. By selecting and controlling the content of the perovskite material in the composite positive electrode material within this range, the slow deoxygenation synergistic effect between the perovskite and the lithium-rich manganese-based positive electrode material in the core body can be improved, so as to further improve the stability of the crystal structure of the lithium-rich manganese-based positive electrode material in the core body, thereby significantly improving the cycle performance and storage performance of the composite positive electrode material. Moreover, the perovskite content in this range can also effectively adjust the thickness of the coating layer and the stability of the contact interface with the electrode liquid, reducing the gas production phenomenon of the positive electrode; and the gram capacity of the composite positive electrode material is improved.

[0010] In some embodiments, the ratio of the mass content of the perovskite material to the mass content of the core body is (0.25 to 0.7): 100. This range can further improve the cycle performance and storage performance of the battery.

[0011] In some embodiments, based on the total mass of the composite positive electrode material, the ratio of the mass content of the fast ion conductor material to the mass content of the core is (0.05 to 10):100. By selecting and controlling the content of the fast ion conductor material in the composite positive electrode material within this range, the synergistic effect between the fast ion conductor material and the lithium-rich manganese-based positive electrode material in the core can be improved, and the synergistic effect between the fast ion conductor material and the perovskite material can also be improved, further improving the excellent coating protection performance of the lithium-rich manganese-based positive electrode material, thereby further improving the stability of the crystal structure of the lithium-rich manganese-based positive electrode material in the core, and improving the interface stability between the composite positive electrode material and the electrolyte, thereby significantly improving the cycle performance and storage performance of the battery and reducing the gas production of the positive electrode; it can also reduce side reactions with active lithium, which is beneficial to improving the first-cycle coulombic efficiency of the battery.

[0012] In some embodiments, the ratio of the mass content of the fast ion conductor material to the mass content of the core is (0.1 to 0.5): 100. This range can further improve the cycle performance and storage performance of the battery.

[0013] In some embodiments, the perovskite material has a cubic phase crystal structure. 2- The transport is isotropic and can act as an oxygen buffer layer to slow down the oxygen release problem of lithium-rich manganese-based positive electrode materials, and improve the gas production and interface stability of the material; especially when the perovskite material has an oxygen-deficient cubic phase crystal structure, it can effectively reduce the oxygen release problem of lithium-rich manganese-based positive electrode materials, thereby improving the gas production and interface stability of the material.

[0014] In some embodiments, the perovskite material includes a compound with a molecular formula of ABX3, A includes one or more elements selected from La, Sr, Ca, Al, Zn, Zr, and K, B includes one or more elements selected from Fe, Ti, Mo, Ga, Ru, Zr, Ir, Co, W, Si, Mn, Nb, Ta, Ge, Cr, and Al, and X includes one or more elements selected from O, F, and Cl.

[0015] In some embodiments, ABX3 includes one or more of LaFeO3, LaTiO3, LaMoO3, LaGaO3, LaRuO3, LaIrO3, LaAlO3, LaGaO3, SrTiO3, SrZrO3, SrCrO3, SrCoO3, SrGeO3, SrMnO3, LaCoO3, ZnTaO3, ZnIrO3, and KNbO3.

[0016] In some embodiments, the total content of elements A and B in the perovskite material in the composite cathode material is 1500 ppm to 6000 ppm. When the total content of elements A and B in the perovskite material is within the above range, it is beneficial to form an oxygen-deficient cubic perovskite structure with element X, which is beneficial to further improve the oxygen release problem of the lithium-rich manganese-based cathode material during high-temperature storage and enhance the structural stability of the lithium-rich manganese-based cathode material.

[0017] In some embodiments, the total content of elements A and B in the perovskite material in the composite cathode material is 1900 ppm to 5500 ppm. The above range can further improve the structural stability of the lithium-rich manganese-based cathode material.

[0018] In some embodiments, the content of element X in the perovskite material in the composite cathode material is 440 ppm to 1800 ppm. When the content of element X in the perovskite material is within the above range, it is conducive to forming an oxygen-deficient cubic perovskite structure with elements A and B, which is conducive to further improving the oxygen release problem of the lithium-rich manganese-based cathode material during high-temperature storage and improving the structural stability of the lithium-rich manganese-based cathode material.

[0019] In some embodiments, the content of the X element in the perovskite material in the composite cathode material is 550 ppm to 1600 ppm. The above range can further improve the structural stability of the lithium-rich manganese-based cathode material.

[0020] In some embodiments, the ionic conductivity of the fast ion conductor material is 10 -5 S / cm to 10 -2 S / cm. The above materials can further improve the migration rate of lithium ions.

[0021] In some embodiments, the ionic conductivity of the fast ion conductor material is 10 -5 S / cm to 6×10 -3 S / cm. The above materials can further improve the migration rate of lithium ions.

[0022] In some embodiments, the fast ion conductor material includes one or more of lithium phosphate Li3PO4, lithium borate Li3BO3, lithium sulfate Li2SO4, and lithium silicate Li2SiO3; further optionally, the fast ion conductor material includes one or more of lithium phosphate Li3PO4, lithium sulfate Li2SO4, and lithium silicate Li2SiO3.

[0023] In some embodiments, the content of Li element in the fast ion conductor material in the composite positive electrode material is 80ppm to 19000ppm; when the content of Li element is within the above range, it is beneficial to form a fast ion conductor crystal structure with other elements, providing abundant pathways for the diffusion of lithium ions; and improving the binding energy with transition metal ions, thereby improving the structural stability of the lithium-rich manganese-based positive electrode material.

[0024] In some embodiments, the content of Li element in the fast ion conductor material in the composite positive electrode material is 150 ppm to 1000 ppm; when the content of Li element is within the above range, the structural stability of the lithium-rich manganese-based positive electrode material can be further improved.

[0025] In some embodiments, the total content of P, B, S, and Si in the fast ion conductor material in the composite cathode material is 100 ppm to 28,000 ppm. When the total content of P, B, S, and Si is within this range, it facilitates the formation of a fast ion conductor crystal structure with other elements, such as Li and O, providing abundant pathways for the diffusion of lithium ions. It also increases the binding energy with transition metal ions, thereby improving the structural stability of the lithium-rich manganese-based cathode material.

[0026] In some embodiments, the total content of P, B, S, and Si in the fast ion conductor material in the composite cathode material is 250 ppm to 1500 ppm. When the total content of P, B, S, and Si is within the above range, the structural stability of the lithium-rich manganese-based cathode material can be further improved.

[0027] In some embodiments, the lithium-rich manganese-based cathode material comprises a molecular formula of Li[Li x Ni a Co b Mn c M d ]O2 compounds, wherein x+a+b+c+d=1, x>0, a+b+c+d<1, 0≤b<1, and M includes one or more of Mg, Nb, Cr, Ce, Fe, Ta, Al, V, Ti, Zr, Sn and Mo. The lithium-rich manganese-based positive electrode materials shown in these structural formulas have a high gram capacity, so that the composite positive electrode material has a high gram capacity, and can further enhance the synergy with the functional materials in the coating layer, thereby improving the lattice stability of the lithium-rich manganese-based positive electrode material, further alleviating the oxygen release phenomenon of the composite positive electrode material and the dissolution phenomenon of metal ions, and improving the cycle performance and storage performance of the composite positive electrode material.

[0028] In some embodiments, the coating layer has a thickness of 0.05 μm to 1.00 μm. By controlling the coating layer thickness within this range, the slow deoxygenation synergistic effect between the perovskite material and / or fast ion conductor material and the lithium-rich manganese-based cathode material in the core body can be enhanced, the effect of relieving metal ion dissolution can be alleviated, and the stability of the crystal structure of the lithium-rich manganese-based cathode material and the stability of the interface with the electrolyte can be improved.

[0029] In some embodiments, the dislocation density of the composite cathode material is 1.55×10 11 cm -2 to 3.7×10 11 cm -2 ; Controlling the dislocation density of the composite positive electrode material within the above range can significantly reduce the stacking faults compared to the dislocation density in other ranges, thereby significantly improving the voltage attenuation problem of the composite positive electrode material 10 during the battery cycle and relatively improving the voltage stability of the composite positive electrode material.

[0030] In some embodiments, the microstress of the composite positive electrode material is 0.3% to 5.0%; optionally 0.3% to 1.0%; the microstress of the composite positive electrode material is controlled within the above range, which can significantly improve the balance within or between the grains in the composite positive electrode material, thereby significantly alleviating the stress accumulation phenomenon of the composite positive electrode material particles during the charge and discharge cycle, thereby improving the stability of the particle structure of the composite positive electrode material, and significantly reducing the occurrence of secondary ball rupture caused by excessive stress in the composite positive electrode material; and can reduce the fatigue and lattice mismatch of the bulk structure of the composite positive electrode material during high-temperature cycling.

[0031] In some embodiments, the BET surface area of ​​the composite cathode material is 0.7 m 2 / g to 3.8m 2 / g; optional 1.35m 2 / g to 3.0m 2 / g; the specific surface area of ​​the composite positive electrode material is controlled within the above range. Compared with the specific surface area in other ranges, the contact area between the composite positive electrode material particles and the electrolyte can be appropriate. On the basis of giving full play to the high gram capacity of the composite positive electrode material, the stability of the contact interface between the composite positive electrode material and the electrolyte can be relatively improved, and the side reactions of the contact interface can be reduced, thereby significantly improving the long-term performance of the composite positive electrode material including the cycle performance; it can also reduce the gas production under high-temperature storage.

[0032] In some embodiments, the composite cathode material has a Dv50 particle size of 6.5 μm to 11 μm; optionally, 7 μm to 10.5 μm. Controlling the Dv50 particle size of the composite cathode material within the above range can increase the compaction density of the composite cathode material particles and improve the structural stability of the composite cathode material particles, while also improving other electrochemical properties of the composite cathode material, including the initial reversible capacity.

[0033] In some embodiments, a composite cathode material, ascorbic acid, and water are mixed to form a mixed system, wherein the composite cathode material has a mass content of 2.0 wt% and the ascorbic acid has a mass content of 0.2 wt%. The mixed system is then mixed with nitric acid in a volume ratio of 1:2. After mixing, the amount of Mn dissolved in the composite cathode material, DM, is measured, wherein DM is ≤ 140 μg / L, and can optionally be ≤ 80 μg / L. When the amount of Mn dissolved in the composite cathode material is within the above range, the amount of Mn dissolved is relatively small, the lithium-rich manganese-based cathode material has high structural stability, good cycle stability, and can effectively improve the cycle performance and storage performance of the battery.

[0034] In a second aspect, an embodiment of the present application provides a method for preparing a composite positive electrode material, comprising:

[0035] mixing the cathode material particles and the functional precursor to obtain a mixture;

[0036] The mixture is sintered so that the functional precursor is sintered into a coating layer, which is coated on at least a portion of the surface of the positive electrode material particles to form a composite positive electrode material, wherein the coating layer includes a perovskite material and a fast ion conductor material.

[0037] In a third aspect, an embodiment of the present application provides a positive electrode comprising a composite positive electrode material according to any embodiment of the first aspect of the present application or a composite positive electrode material prepared by a preparation method according to any embodiment of the second aspect of the present application.

[0038] In a fourth aspect, an embodiment of the present application provides a battery comprising the positive electrode of any embodiment of the third aspect of the present application.

[0039] In a fifth aspect, an embodiment of the present application provides an electrical device comprising a battery according to any embodiment of the fourth aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0041] FIG1 is a schematic structural diagram of a composite cathode material according to some embodiments of the present application;

[0042] FIG2 is a schematic structural diagram of a positive electrode in some embodiments of the present application;

[0043] FIG3 is another schematic structural diagram of a positive electrode according to some embodiments of the present application;

[0044] FIG4 is a schematic structural diagram of an embodiment of a battery cell according to the present application;

[0045] FIG5 is an exploded schematic diagram of the battery cell shown in FIG4 ;

[0046] FIG6 is a schematic structural diagram of an embodiment of a battery module according to the present application;

[0047] FIG7 is a schematic structural diagram of an embodiment of a battery pack according to the present application;

[0048] FIG8 is a schematic diagram of the exploded structure of the battery pack shown in FIG7 ;

[0049] FIG9 is a schematic diagram of an embodiment of an electrical device including a battery according to an embodiment of the present application as a power source;

[0050] FIG10 is a scanning electron microscope (SEM) image of the composite positive electrode material of Example 1 of the present application.

[0051] The figure numbers in the specific implementation manner are as follows: 10, composite positive electrode material, 11, core body, 12, coating layer; 20, positive electrode, 21, current collector, 22, active layer; 30, battery cell, 31, shell, 32, electrode assembly, 33, cover plate; 40, battery module; 50, battery pack, 51, box, 52, lower box. DETAILED DESCRIPTION

[0052] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0054] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0055] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0056] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0057] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0058] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0059] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0060] With the rapid popularization of lithium-ion batteries, especially in electric vehicles, the requirements for the cycle performance of lithium-ion batteries are becoming increasingly higher.

[0061] The positive electrode is one of the most important components of a battery, containing positive electrode active materials. This positive electrode active material has a significant impact on the electrochemical performance of the battery, such as the battery's cycle performance and energy density.

[0062] The emergence of lithium-rich manganese-based cathode materials has significantly improved the energy density of batteries. However, the elements in these materials may be separated from their original lattice positions, making the crystal framework unstable. This leads to poor structural stability of the materials and reduced battery cycle performance.

[0063] In related technologies, in order to improve the structural stability of lithium-rich manganese-based positive electrode materials, a coating layer is usually set on the surface of the lithium-rich manganese-based positive electrode materials to perform coating modification on them. However, the coating effect is not ideal and the structural stability of the lithium-rich manganese-based positive electrode materials cannot be effectively improved.

[0064] In order to further solve the above problems, an embodiment of the present application provides a composite positive electrode material containing a coating layer, wherein the coating layer includes a perovskite material and a fast ion conductor material. The above materials can enhance the modification effect of the coating layer on the lithium-rich manganese-based positive electrode material, and improve the crystal structure stability of the composite positive electrode material, thereby significantly improving the electrochemical properties of the battery, including cycle performance and storage performance.

[0065] Composite cathode materials

[0066] In a first aspect, an embodiment of the present application provides a composite positive electrode material.

[0067] The composite positive electrode material 10 of the embodiment of the present application has a core-shell structure. In some embodiments, the structure of the composite positive electrode material 10 of the embodiment of the present application is shown in Figure 1. The composite positive electrode material 10 includes a core 11 and a coating layer 12 coating the core 11. The core 11 contains a lithium-rich manganese-based positive electrode material, and the coating layer 12 is coated on at least a portion of the surface of the core 11. The coating layer 12 includes a functional material, and the functional material includes a perovskite material and a fast ion conductor material.

[0068] The core-shell structure of the composite positive electrode material 10 in the embodiment of the present application refers to a core body 11 and a shell layer coating the core body 11, that is, a coating layer 12. Coating the core body 11 means that the coating layer 12 forms a film layer enclosing the surface of the core body 11. The core body 11 contains a lithium-rich manganese-based positive electrode material, which can be understood as the material of the core body 11 being entirely lithium-rich manganese-based positive electrode material. Of course, in addition to containing the lithium-rich manganese-based positive electrode material, it can also contain other components, such as lithium-supplementing materials that are beneficial to increasing the capacity of the lithium-rich manganese-based positive electrode material, or additives that can synergistically work with the coating layer 12 to reduce the oxygen release of the lithium-rich manganese-based positive electrode material.

[0069] The embodiment of the present application can significantly improve the modification effect of the coating layer 12 on the lithium-rich manganese-based positive electrode material by coating the lithium-rich manganese-based positive electrode material with perovskite material and fast ion conductor material, improve the crystal structure stability of the composite positive electrode material 10, and the interface stability between the composite positive electrode material 10 and the electrolyte, thereby significantly improving the electrochemical properties of the battery such as the cycle performance and storage performance.

[0070] The possible mechanism of action of the embodiments of the present application is speculated to be as follows:

[0071] In the related art, lithium-rich manganese-based positive electrode materials have an oxygen release phenomenon, which is specifically manifested as the oxygen on the surface of the lithium-rich manganese-based positive electrode material easily escapes from the lattice position, causing the instability of its crystal skeleton, thereby reducing the cycle performance of the battery. Moreover, the escaped oxygen has a high reactivity and will reduce the stability of the interface between the electrode and the electrolyte. For example, it will corrode the lithium-rich manganese-based positive electrode material in the electrode at the interface between the electrode and the electrolyte, resulting in an unstable solid electrolyte interface (Solid Electrolyte Interphase, SEI) film and the corresponding proton generation. The protons will continue to etch the material, accelerating these adverse reactions, such as the occurrence of gassing and other adverse phenomena. In order to alleviate the oxygen release phenomenon of the lithium-rich manganese-based positive electrode material and further improve the stability of the structure and electrochemical performance of the lithium-rich manganese-based positive electrode material, the embodiment of the present application makes the coating layer 12 contain a perovskite material, thereby improving the synergistic effect between the coating layer 12 and the lithium-rich manganese-based positive electrode material. In particular, when the perovskite material is an oxygen-deficient structure, it can effectively alleviate the oxygen release problem of the lithium-rich manganese-based positive electrode material, improve the modification effect of the coating layer 12 on the lithium-rich manganese-based positive electrode material, significantly alleviate the oxygen release phenomenon of the lithium-rich manganese-based positive electrode material, and improve the crystal structure stability of the composite positive electrode material 10, thereby significantly improving the electrochemical properties of the battery, such as the cycle performance and storage performance.

[0072] In the related art, the lithium-rich manganese-based positive electrode material also has the dissolution of metal ions such as manganese ions. The dissolution of metal ions will lead to the instability of the crystal skeleton, which will lead to a decrease in the cycle performance of the battery. Moreover, the metal ions dissolve from the lattice position into the electrolyte, and may migrate to the surface of the negative electrode through the electrolyte, causing damage to the SEI film, resulting in further deterioration of the cycle performance. In the embodiment of the present application, the coating layer 12 includes a fast ion conductor material. The fast ion conductor material can combine with the metal ions, stabilize the metal ions in the lithium-rich manganese-based positive electrode material, reduce the risk of metal ion dissolution, thereby improving the crystal structure stability of the composite positive electrode material 10, and thus significantly improving the electrochemical properties of the battery including cycle performance and storage performance. The fast ion conductor is ion conductive, and the carriers can be cations, anions or ion vacancies. Its ionic conductivity can be ≥10 -9 S / cm, and can provide abundant lithium ion diffusion pathways, which is beneficial to the migration of lithium ions in fast ion conductors. The bond type of lithium ions in the fast ion conductor lattice is mainly ionic bond, and the Coulomb attraction between lithium ions and the fixed ions in the lattice is relatively small, which is beneficial to the rapid migration of lithium ions and further improves the kinetic performance of the battery.

[0073] Although perovskite materials can effectively alleviate the oxygen release problem of lithium-rich manganese-based positive electrode materials, the perovskite materials themselves may undergo side reactions with active lithium, resulting in limited improvement in gram capacity or even a possible decrease; and the kinetic performance of the perovskite materials themselves is relatively poor, which limits the improvement in the kinetic performance of lithium-rich manganese-based positive electrode materials.

[0074] Furthermore, when the coating layer 12 includes a perovskite material and a fast ion conductor material, the perovskite material and the fast ion conductor material work together to change the performance of the coating layer 12. The coating layer 12 can effectively mitigate the deoxidation effect, thereby effectively improving the lattice structure stability of the lithium-rich manganese-based positive electrode material, thereby improving the battery's cycling performance and storage performance. Furthermore, the perovskite material and the fast ion conductor material work together to effectively reduce the risk of side reactions between the perovskite material and active lithium; they can also further improve the kinetic performance, which is conducive to improving the battery's first-cycle coulombic efficiency.

[0075] [Lithium-rich manganese-based cathode materials]

[0076] In the embodiment, the molecular formula of the lithium-rich manganese-based positive electrode material contained in the core 11 of the composite positive electrode material 10 can be expressed as Li[Li x Ni a Co b Mn c M d ]O2, wherein x+a+b+c+d=1, x>0, a+b+c+d<1, 0≤b<1, and M includes one or more of Mg, Nb, Cr, Ce, Fe, Ta, Al, V, Ti, Zr, Sn and Mo. In the exemplary embodiment, the lithium-rich manganese-based positive electrode material may specifically include Li 1.2 Mn 0.48 Co 0.1 Ni 0.2 Ti 0.02 O2、Li 1.2 Mn 0.48 Co 0.1 Ni 0.2 Zr 0.02 O2、Li 1.2 Mn 0.48 Co 0.1 Ni 0.2 Mo 0.02 O2、Li 1.2 Mn 0.48 Co 0.1 Ni 0.2 V 0.02O2, etc. The lithium-rich manganese-based positive electrode materials shown in these structural formulas have a high gram capacity, which makes the composite positive electrode material 10 have a high gram capacity, and can further enhance the lattice stability of the lithium-rich manganese-based positive electrode material with the functional materials in the coating layer 12, further alleviate the oxygen release phenomenon and metal ion dissolution phenomenon of the composite positive electrode material 10, and improve the cycle performance and storage performance of the composite positive electrode material 10.

[0077] In the embodiment, the gram capacity of the composite positive electrode material 10 is 210 mAh / g to 220 mAh / g, for example, 210 mAh / g, 212 mAh / g, 213 mAh / g, 214 mAh / g, 215 mAh / g, 216 mAh / g, 217 mAh / g, 218 mAh / g, 219 mAh / g, 220 mAh / g, or a range consisting of any two of the above values.

[0078] During the charge and discharge process, active ions such as Li are intercalated and deintercalated, and consumed in battery cells. The molar content of Li in battery cells varies at different discharge states. The molar content of Li in the examples of the composite positive electrode material 10 in the present embodiment refers to the material's initial state, i.e., the state before the materials are added. When the composite positive electrode material 10 is used in a battery system, the molar content of Li may change after charge and discharge cycles.

[0079] In the examples of the composite positive electrode material 10 in the embodiments of the present application, the molar content of oxygen O is only a theoretical value. The release of oxygen from the lattice will cause the molar content of oxygen O to change. In reality, the molar content of oxygen O will fluctuate.

[0080] The core 11 in the composite positive electrode material 10 can be of regular morphology or irregular morphology. For example, in the exemplary embodiment, the core 11 can be spherical or spherical-like in shape, and of course it can also be of other morphologies. Moreover, its particle size and the thickness of the coating layer 12 can jointly affect the particle size of the composite positive electrode material 10. For example, in the embodiment, the average particle size of the core 11 can be 5μm to 11μm, optionally 6μm to 8μm. In the exemplary embodiment, it can be a typical but non-limiting particle size range consisting of any two values ​​such as 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, and 11μm. Selecting and controlling the particle size of the core 11 within the above range can not only increase the content ratio of lithium-rich manganese-based positive electrode material in the composite positive electrode material 10, but also increase the gram capacity of the composite positive electrode material 10. Moreover, the core body 11 with a particle size in this range can match the content of the functional material in the lithium-rich manganese-based positive electrode material with that in the coating layer 12 relative to other particle size ranges, thereby improving the lattice stabilization role of the coating layer 12 on the basis of making the composite positive electrode material 10 have a relatively high gram capacity, and improving the inhibition of the oxygen release of the lithium-rich manganese-based positive electrode material and / or the dissolution of metal ions, thereby further alleviating the capacity decay of the lithium-rich manganese-based positive electrode material, and further improving the cycle performance of the composite positive electrode material 10 and the stability of the electrolyte interface. In addition, the particle size range of the core body 11 can also be used together with the coating layer 12 to adjust the particle size of the composite positive electrode material 10, such as the Dv50 particle size of the composite positive electrode material 10 can be 6.5 to 11 μm, thereby improving the properties of the composite positive electrode material 10, including the compaction density.

[0081] In an embodiment of the present application, the average particle size of the core body 11 can be calculated by methods and equipment known in the art. For example, a transmission electron microscope (TEM) can be used to scan a cross-sectional photograph of the composite positive electrode material 10, and then the particle size of the core body 11 can be measured. 50 sample particles are tested and the average value is taken as the average particle size.

[0082] In an embodiment of the present application, the chemical formula of the composite positive electrode material 10 and the content of the added elements can be measured by methods and equipment known in the art. For example, referring to EPA6010D-2014, the chemical formula of the composite positive electrode material 10 and the content of the added elements can be measured by methods and equipment known in the art. For example, by inductively coupled plasma atomic emission spectrometry (ICP-OES) testing, the instrument model: ThermoICAP7400 equipment is used for measurement. As an example, the following steps can be followed: first, a certain mass (for example, 1 g) of the composite positive electrode material 10 is weighed in a beaker, and a certain volume (for example, 25 mL) of an acid (for example, HNO3) solution of a certain concentration (for example, a concentration of 25% by volume) is added to the composite positive electrode material 10 to dissolve the composite positive electrode material 10, and diluted with a certain volume (for example, 475 mL) of deionized water, and then the diluted liquid is placed in the ThermoICAP7400 equipment for target element analysis and calculation, and the content of the target element and the chemical formula of the composite positive electrode material 10 are obtained by calculation.

[0083] [Perovskite materials]

[0084] The perovskite material may be a perovskite material with a cubic crystal structure, and its molecular formula may be ABX3. The above perovskite material has high symmetry. 2- The transport of oxygen is isotropic, and it can act as an oxygen buffer layer to mitigate the oxygen release problem of lithium-rich manganese-based cathode materials, improving the material's gas production and interface stability. In particular, when the perovskite material has an oxygen-deficient cubic phase crystal structure, it can effectively mitigate the oxygen release problem of lithium-rich manganese-based cathode materials, thereby improving the material's gas production and interface stability. Moreover, the chemical properties of the above-mentioned perovskite material are stable and have acid resistance and acid corrosion resistance. It can reduce the corrosion of side reaction products in the electrolyte, such as hydrofluoric acid HF, and can significantly improve the interface stability between the lithium-rich manganese-based cathode material and the electrolyte, thereby improving the cycle stability of the lithium-rich manganese-based cathode material.

[0085] The core 11 contained in the composite positive electrode material 10 of the embodiment of the present application contains a lithium-rich manganese-based positive electrode material, which gives the composite positive electrode material 10 a high gram capacity. Furthermore, A and B in the ABX3 perovskite can be selected from specific elements, A includes a first element, A can include one or more elements of La, Sr, Ca, Al, Zn, Zr, K, B includes a second element different from the first element, B can include one or more elements of Fe, Ti, Mo, Ga, Ru, Zr, Ir, Co, W, Si, Mn, Nb, Ta, Ge, Cr, Al, and X includes one or more elements of O, F, and Cl; ABX3 perovskite has a relatively regular cubic phase perovskite structure with relatively high crystal symmetry, and X 2-The transport isotropy is relatively higher, so this specific ABX3 perovskite can form an oxygen buffer layer relatively better in the coating layer 12. Since the coating layer 12 can play a better role as an oxygen buffer layer, it can significantly suppress the oxygen release phenomenon of the lithium-rich manganese-based positive electrode material in the core 11, improve the stability of the crystal structure of the lithium-rich manganese-based positive electrode material, thereby effectively alleviating the capacity decay of the lithium-rich manganese-based positive electrode material, so as to significantly improve the cycle performance of the composite positive electrode material 10. Due to the oxygen slow-release effect of the coating layer 12, the amount of oxygen in the composite positive electrode material 10 that escapes into the electrolyte can be effectively reduced; in addition, the chemical properties of the above-mentioned ABX3 perovskite, such as acid resistance, are more stable than other perovskites, thereby enhancing the acid corrosion resistance, such as the corrosion of HF, a side reaction product of the electrolyte. Therefore, through the combined effect of the oxygen release effect of the coating layer 12 and its own good chemical stability, the stability of the interface between the positive electrode 20 containing the composite positive electrode material 10 and the electrolyte is effectively improved, the gas production of the positive electrode 20 is reduced, and the reliability of the battery is improved.

[0086] In the embodiment, based on the element types A and B in the ABX3 perovskite contained in the coating layer 12 of the composite positive electrode material 10 of each embodiment above, the valence of the A ion can be +2 or +3, and the valence of the B ion can be +3 or +4; the ionic radius r of the element represented by X is x The ionic radius r of the element shown in B B Satisfy r x / r B ≥2.7, 2.7≤(r A / r B ) / ln(r A / r B )≤3.6. Furthermore, the ionic radius r of the element represented by A A Can be 70pm≤r A ≤150pm; ionic radius r of the element indicated by B B Can be 40pm≤r B ≤100pm, and r A >r BFurther, the sum of the valence of the A ion and the valence of the B ion may be 6. For example, the ABX3 perovskite may include one or more of LaFeO3, LaTiO3, LaMoO3, LaGaO3, LaRuO3, LaMnO3, LaIrO3, LaAlO3, LaGaO3, SrTiO3, SrZrO3, SrCrO3, SrCoO3, SrGeO3, SrMnO3, LaCoO3, ZnTaO3, ZnIrO3, and KNbO3. Furthermore, the ABX3 perovskite may specifically include one or more of LaFeO3, LaTiO3, LaMoO3, LaGaO3, LaRuO3, LaIrO3, LaAlO3, LaGaO3, SrTiO3, SrZrO3, SrCrO3, SrCoO3, SrGeO3, SrMnO3, LaCoO3, ZnTaO3, ZnIrO3, and KNbO3. Alternatively, the ABX3 perovskite may specifically include one or more of LaFeO3, LaTiO3, LaMoO3, LaGaO3, LaRuO3, SrTiO3, SrZrO3, LaIrO3, LaAlO3, and LaCoO3.

[0087] The above ABX3 perovskites have higher O 2- The high transport isotropy and crystal symmetry can enhance the role of the coating layer 12 as an oxygen buffer layer, thereby improving the slow deoxygenation effect of the coating layer 12, further improving the stability of the crystal structure of the lithium-rich manganese-based positive electrode material, and thus further alleviating the capacity decay of the lithium-rich manganese-based positive electrode material, thereby significantly improving the cycle performance of the composite positive electrode material 10. Moreover, these types of ABX3 perovskites have stronger acid resistance, thereby further improving the stability of the interface between the positive electrode 20 containing the composite positive electrode material 10 and the electrolyte, and reducing the gas generation phenomenon of the positive electrode 20.

[0088] In the embodiment, the mass ratio of the ABX3 perovskite contained in the coating layer 12 of the composite positive electrode material 10 of each embodiment above to the core body 11 can be (0.2 to 0.8):100, and can be optionally (0.25 to 0.7):100. In exemplary embodiments, the mass ratio can be 0.2:100, 0.25:100, 0.3:100, 0.4:100, 0.5:100, 0.6:100, 0.7:100, 0.8:100, and the like, which are typical but non-limiting ratios. The mass ratio of the ABX3 perovskite contained in the coating layer 12 of the composite positive electrode material 10 of each embodiment above to the core body 11 refers to the ratio of the mass content of the perovskite material to the mass content of the core body 11 based on the total mass of the composite positive electrode material 10.

[0089] By controlling the ABX3 perovskite content in the composite cathode material 10 within this range, the slow deoxygenation synergistic effect between the ABX3 perovskite and the lithium-rich manganese-based cathode material in the core 11 can be enhanced, further improving the stability of the crystal structure of the lithium-rich manganese-based cathode material in the core 11, and significantly improving the cycling performance and storage performance of the composite cathode material 10. Furthermore, the ABX3 perovskite content within this range can effectively adjust the thickness of the coating layer 12 and the stability of the contact interface with the electrode liquid, reducing gassing of the positive electrode 20; and the gram capacity of the composite cathode material 10 is increased.

[0090] In the embodiment, the total content of elements A and B in the perovskite material in the composite positive electrode material 10 is 1500ppm to 6000ppm, optionally 1900ppm to 5500ppm or 1500 to 4500ppm. In the exemplary embodiment, it can be a typical but non-limiting content range consisting of any two values ​​such as 1500ppm, 1900ppm, 2000ppm, 2500ppm, 3000ppm, 3500ppm, 4000ppm, 4500ppm, 5000ppm, 5500ppm, 6000ppm. When the total content of elements A and B in the perovskite material is within the above range, it is beneficial to form an oxygen-deficient cubic phase perovskite structure with element X, which is beneficial to further improve the oxygen release problem of lithium-rich manganese-based positive electrode materials during high-temperature storage and enhance the structural stability of lithium-rich manganese-based positive electrode materials.

[0091] In the embodiment, the content of element X in the perovskite material in the composite positive electrode material 10 is 440 ppm to 1800 ppm, and can be optionally 550 ppm to 1600 ppm. In an exemplary embodiment, the content can be 440 ppm, 500 ppm, 550 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1100 ppm, 1200 ppm, 1300 ppm, 1400 ppm, 1500 ppm, 1600 ppm, or any two values, which are typical but non-limiting content ranges.

[0092] When the content of element X in the perovskite material is within the above range, it is conducive to forming an oxygen-deficient cubic phase perovskite structure with elements A and B, which is conducive to further improving the oxygen release problem of lithium-rich manganese-based positive electrode materials during high-temperature storage and enhancing the structural stability of lithium-rich manganese-based positive electrode materials.

[0093] In the embodiment of the present application, the total content of element A, element B, and element X in the composite positive electrode material 10 can be determined using conventional methods for element content. As an example, with reference to EPA 6010D-2014, the measurement is performed by inductively coupled plasma atomic emission spectrometry (ICP-OES) using a Thermo ICAP 7400 instrument.

[0094] [Fast ion conductor materials]

[0095] Fast ion conductor materials can increase the abundance of lithium ion diffusion pathways, which is beneficial to improving the migration rate of lithium ions; and fast ion conductor materials can also combine with transition metal ions and increase the formation of oxygen defects, which can further alleviate the dissolution of transition metal ions and oxygen.

[0096] Fast ion conductor materials are beneficial to improving the migration rate of lithium ions, especially when the ionic conductivity of fast ion conductor materials is ≥10 -9 S / cm, optional 10 -9 S / cm to 10 -2 S / cm, optional 10 -5 S / cm to 10 -2 S / cm, optional 10 -5 S / cm to 6×10 -3 S / cm, which can further improve the migration rate of lithium ions. For example, the ionic conductivity of fast ion conductor materials can be 10 -9 S / cm, 10 -8 S / cm, 10 -7 S / cm, 10 -6 S / cm, 10 -5 S / cm, 10 -4 S / cm, 10 -3 S / cm, 10 -2 Typical but non-limiting ranges are formed by any two values ​​such as S / cm.

[0097] In an embodiment, the fast ion conductor material may include one or more of phosphate, borate, sulfate and silicate; specifically, the fast ion conductor material includes Li m YO n , Y includes one or more elements selected from P, B, S, and Si, m represents the molar amount of Li relative to 1 mol Y, and n represents the molar amount of O relative to 1 mol Y; optionally, Li m YO nIncluding one or more of lithium phosphate Li3PO4, lithium borate Li3BO3, lithium sulfate Li2SO4, and lithium silicate Li2SiO3. Optionally, the fast ion conductor material may include one or more of phosphate, sulfate, and silicate. The above-mentioned fast ion conductor material can increase the rich lithium ion diffusion path, which is beneficial to improving the migration rate of lithium ions; the above-mentioned fast ion conductor material can also have a strong binding effect with metal ions, such as complexation reaction. For example, the anionic ligand in the fast ion conductor material can complex transition metal ions. Due to the large binding energy, the metal ions are locked and not easily migrated. It can further increase the formation of oxygen defects, further reduce the dissolution of metal ions and oxygen in the lithium-rich manganese-based positive electrode material, and improve the lattice structure stability of the lithium-rich manganese-based positive electrode material. Moreover, the fast ion conductor material and the perovskite material work together to effectively reduce the risk of side reactions between the coating layer 12 and the active lithium; it can also further improve the kinetic performance and enhance the specific capacity of the lithium-rich manganese-based positive electrode material. In addition, the fast ion conductor material and the perovskite material work together to form the coating layer 12, which can improve the interface stability between the composite positive electrode material 10 and the electrolyte, reduce the risk of side reactions, thereby reducing the gas production of the positive electrode 20 and improving the reliability of the battery.

[0098] In the embodiment, the mass ratio of the fast ion conductor material contained in the coating layer 12 of the composite positive electrode material 10 of each embodiment to the core body 11 is (0.05 to 10):100, which can be (0.1 to 0.5):100. In the exemplary embodiment, it can be 0.05:100, 0.1:100, 0.15:100, 0.2:100, 0.25:100, 0.3:100, 0.4:100, 0.5:100, 0. .6:100, 0.7:100, 0.8:100, 1:100, 1.2:100, 1.5:100, 2:100, 2.2:100, 2.5:100, 2.8:100, 3:100, 3.2:100, 3.5:100, 3.8:100, 4:100, 4.2:100, 4.5:100, 5:100, etc. are typical but non-limiting ranges consisting of any two ratios.

[0099] The mass ratio of the fast ion conductor material contained in the coating layer 12 of the composite positive electrode material 10 to the core 11 refers to the ratio of the mass content of the fast ion conductor material to the mass content of the core 11 based on the total mass of the composite positive electrode material 10 .

[0100] By selecting and controlling the content of the fast ion conductor material in the composite positive electrode material 10 within this range, the synergistic effect between the fast ion conductor material and the lithium-rich manganese-based positive electrode material in the core 11 can be improved, and the synergistic effect between the fast ion conductor material and the perovskite material can also be improved, further improving the excellent coating protection performance of the lithium-rich manganese-based positive electrode material, so as to further improve the stability of the crystal structure of the lithium-rich manganese-based positive electrode material in the core 11, and improve the interface stability between the composite positive electrode material 10 and the electrolyte, so as to significantly improve the cycle performance and storage performance of the battery, and reduce the gas production of the positive electrode 20; it can also reduce the side reaction with active lithium, improve the specific capacity performance of the lithium-rich manganese-based positive electrode material, and improve the first-cycle coulomb efficiency of the battery.

[0101] In the embodiment, the content of Li element in the fast ion conductor material in the composite positive electrode material 10 is 80ppm to 19000ppm, and can be optionally 150ppm to 1000ppm. In the exemplary embodiment, it can be 80ppm, 150ppm, 200ppm, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, 1100ppm, 1200ppm, 1300ppm, 1400ppm, 1500ppm, 2000ppm, 3000ppm, 4000ppm, 5000ppm, 6000ppm, 7000ppm, 8000ppm, 10000ppm, 11000ppm, 12000ppm, 15000ppm, 16000ppm, 17000ppm, 18000ppm, 19000ppm, etc., which is a typical but non-limiting content range composed of any two values. When the content of Li element is within the above range, it is beneficial to form a fast ion conductor crystal structure with other elements, providing abundant pathways for the diffusion of lithium ions; and improving the binding energy with transition metal ions, thereby improving the structural stability of lithium-rich manganese-based positive electrode materials.

[0102] In the embodiment, the total content of P, B, S and Si elements in the fast ion conductor material in the composite positive electrode material 10 is 100ppm to 28000ppm, and can be optionally 250ppm to 1500ppm. In the exemplary embodiment, it can be a typical but non-limiting content range composed of any two values ​​such as 100ppm, 500ppm, 1000ppm, 1200ppm, 1500ppm, 2000ppm, 3000ppm, 4000ppm, 4500ppm, 5000ppm, 6000ppm, 7000ppm, 8000ppm, 9000ppm, 10000ppm, 11000ppm, 12000ppm, 13000ppm, 14000ppm, 15000ppm, 20000ppm, 25000ppm, 28000ppm.

[0103] When the total content of P, B, S and Si elements is within the above range, it is beneficial to form a fast ion conductor crystal structure with other elements such as Li and O, providing abundant pathways for the diffusion of lithium ions; and improving the binding energy with transition metal ions, thereby improving the structural stability of lithium-rich manganese-based positive electrode materials.

[0104] In the embodiment of the present application, the total content of Li, P, B, S, and Si in the composite positive electrode material 10 can be measured using conventional methods for elemental content. As an example, ICP emission spectrometry (inductively coupled plasma emission spectrometry) can be used for measurement. The specific test process refers to the standard test method EPA6010D-2014.

[0105] In an embodiment, transition metal ions in the lithium-rich manganese-based positive electrode material may be dissolved, such as iron ions and manganese ions. The amount of manganese ions dissolved is detected to confirm the structural stability of the lithium-rich manganese-based positive electrode material. Specifically, the dissolution amount DM of the Mn element in the composite positive electrode material 10, wherein DM≤140μg / L, can be optionally ≤70μg / L; in an exemplary embodiment, it can be a typical but non-limiting content range consisting of any two values ​​such as 0μg / L, 10μg / L, 20μg / L, 30μg / L, 40μg / L, 50μg / L, 60μg / L, 70μg / L, 80μg / L, 90μg / L, 100μg / L, 110μg / L, 120μg / L, 130μg / L, 140μg / L. When the dissolution amount of the Mn element in the composite positive electrode material 10 is within the above range, the dissolution amount is relatively small, the lithium-rich manganese-based positive electrode material has high structural stability and good cycle stability, and can effectively improve the cycle performance and storage performance of the battery.

[0106] The dissolution amount test of the Mn element can be carried out by the following method: the composite positive electrode material 10, ascorbic acid and water are mixed into a mixed system, the mass content of the composite positive electrode material 10 is 2.0wt%, and the mass content of ascorbic acid is 0.2wt%; the mixed system and nitric acid are mixed in a volume ratio of 1:2, and after mixing, the dissolution amount DM of the Mn element in the composite positive electrode material 10 is determined by inductively coupled plasma optical emission spectroscopy (ICP-OES).

[0107] Specifically, the dissolution test process of the Mn element is as follows:

[0108] ① Weigh 1±0.01g of sample;

[0109] ② Add 50 mL of ultrapure water to a 150 mL beaker, add 0.1 ± 0.01 g of ascorbic acid powder (VC), and sonicate for 5 minutes until completely dissolved.

[0110] ③ Measure 50 mL of the prepared 0.2 wt% VC solution and add it to another beaker. Place a magnetic rod in the beaker and seal it for magnetic stirring at 500 rpm. The process is as follows: magnetic stirring for 5 minutes, let it stand for 24 minutes, and magnetic stirring for 1 minute.

[0111] ④Pipette the stirred solution and filter 4 mL of the filtrate into a test tube;

[0112] ⑤ Add 2 mL of nitric acid to a 100 mL glass volumetric flask, and then pipette 1 mL of the filtrate from the previous test tube into the glass volumetric flask to make up the volume;

[0113] ⑥ Use inductively coupled plasma optical emission spectroscopy (ICP-OES) to test the dissolution amount of Mn element, input the dilution ratio and constant volume / sample mass, and record the experimental result Mn / ppm.

[0114] The above test process can simulate the Mn dissolution of the battery in a high-temperature storage environment to reflect the Mn dissolution situation.

[0115] Based on the core 11 and coating 12 contained in the above-mentioned composite positive electrode material 10, the dislocation density, microstress, specific surface area and particle size of the composite positive electrode material 10 can be improved by adjusting and controlling the particle size of the core 11 and the material and thickness of the coating 12, thereby further improving the mechanical properties of the composite positive electrode material 10 including structural strength and the electrochemical properties including voltage stability and stability of the contact interface with the electrolyte.

[0116] In an embodiment, the thickness range of the coating layer 12 can be adjusted by controlling the total content of the perovskite material and / or the fast ion conductor material in the composite positive electrode material 10. For example, in an embodiment, the thickness of the coating layer 12 contained in the composite positive electrode material 10 can be controlled to be 0.05 μm to 1 μm, optionally 0.1 μm to 0.8 μm, and further 0.1 to 0.4 μm. In exemplary embodiments, the thickness range can be 0.05 to 0.1 μm, 0.1 to 0.2 μm, 0.2 to 0.3 μm, 0.3 to 0.4 μm, 0.4 to 0.5 μm, 0.5 to 0.6 μm, 0.6 to 0.7 μm, 0.7 to 0.8 μm, 0.8 to 0.9 μm, 0.9 to 1 μm, and the like, which are typical but non-limiting thickness ranges. By controlling the thickness of the coating layer 12 within this range, the slow deoxygenation synergistic effect between the perovskite material and / or fast ion conductor material and the lithium-rich manganese-based positive electrode material in the core 11 can be enhanced, and the effect of relieving metal ion dissolution can be alleviated. This improves the stability of the crystal structure of the lithium-rich manganese-based positive electrode material and the stability of the interface with the electrolyte. As shown in the table below, the relevant performance of the batteries in Examples B1 to B4 is superior to that of the batteries in Examples B5 and B6. At the same time, the high gram capacity of the composite positive electrode material 10 can also be taken into account.

[0117] In the embodiments of the present application, the thickness of the coating layer 12 can be measured by scanning a cross-sectional photograph of the coating layer 12 with a transmission electron microscope (TEM) and then measuring the distance between the inner wall and the outer wall of the coating layer 12; or by using a scanning electron microscope (SEM) and EDS. For example, a sample preparation glue and the composite positive electrode material 10 powder are evenly mixed and then coated on a copper foil to obtain a sample, wherein the weight of the powder is 5 times that of the sample preparation glue, and then dried at 60°C for 30 minutes. The prepared sample is cut into 6mm*6mm pieces with scissors, fixed on a sample stage, and placed in an ion polisher. The sample edge is adjusted parallel to the centering line X-axis and the Y-axis position is 40-60μm for cutting. After cutting, an energy dispersive spectrometer (EDS) combined with a scanning electron microscope (SEM) is used to select a suitable particle section on the cut sample, and a linear scan of the characteristic element content of the coating layer 12 is performed along the particle diameter direction. The radius of the measured particle is R, and the distance from the site where the element content of the coating layer 12 begins to increase compared to the particle core 11 to the center of the particle is L1. The thickness L of the coating layer 12 is (R-L1) μm.

[0118] As shown in the embodiment, the dislocation density of the composite positive electrode material 10 in each of the above embodiments can be 1.55×10 11 to 3.7×10 11 cm -2 , optional 1.8×10 11 to 3.2×10 11 cm -2 , in this example, it can be 1.55×1011 to 1.8×10 11 cm -2 , 1.8×10 11 to 2.0×10 11 cm -2 , 2.0×10 11 to 2.5×10 11 cm -2 , 2.5×10 11 to 3.0×10 11 cm -2 , 3.0×10 11 to 3.2×10 11 cm -2 , 3.2×10 11 to 3.5×10 11 cm -2 Typical but non-limiting dislocation density ranges are shown. The dislocation density quantifies the dislocations contained in the crystals of the composite positive electrode material 10, specifically the total length of the dislocation lines contained in the unit volume of the crystals. Controlling the dislocation density of the composite positive electrode material 10 within the above range can significantly reduce stacking faults compared to dislocation densities in other ranges, thereby significantly improving the voltage decay problem of the composite positive electrode material 10 during battery cycling and relatively improving the voltage stability of the composite positive electrode material 10.

[0119] In the embodiment of the present application, the dislocation density of the composite positive electrode material 10 can be calculated by methods and equipment known in the art. For example, the dislocation density of the composite positive electrode material 10 is measured based on XRD test β = (1 / D) 2 ×10 16 , where D = Kλ / Bcosθ, K = 0.9, λ = 1.5406, B is the half-height width of the composite cathode material 10 (hkl) crystal plane in the XRD diffraction pattern, and θ is the diffraction angle.

[0120] In the embodiments, the microstress of the composite positive electrode material 10 of each of the above embodiments may be 0.3% to 5.0%, optionally 0.3% to 1.0%. In exemplary embodiments, the microstress range may be a typical but non-limiting range consisting of any two values ​​such as 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, and 5%. Microstress refers to stress acting between the microstructures of the composite positive electrode material 10, also known as microresidual stress, and specifically refers to stress existing between or within grains in the composite positive electrode material 10 due to factors such as deformation, phase change, and expansion of multiphase materials. The microstress of the composite positive electrode material 10 is controlled within the above range, which can significantly improve the balance within or between the grains in the composite positive electrode material 10, thereby significantly alleviating the stress accumulation phenomenon of the composite positive electrode material 10 particles during the charge and discharge cycle, thereby improving the stability of the particle structure of the composite positive electrode material 10, and significantly reducing the occurrence of secondary ball rupture caused by excessive stress in the composite positive electrode material 10; and can reduce the fatigue and lattice mismatch of the bulk structure of the composite positive electrode material 10 during high-temperature cycling.

[0121] In an embodiment of the present application, the micro stress of the composite positive electrode material 10 can be calculated by methods and equipment known in the art. For example, by X-ray diffraction pattern (XRD) test fitting. As an example, the following steps can be followed: first set the XRD test conditions: use a Cu target, set the tube voltage (e.g., 40V), set the tube current (e.g., 40mA), set the scan speed (e.g., <2° / min), set the 2θ scan range (e.g., 15°-70°), set the step size (e.g., 0.02°), set the emission slit (DS) (e.g., 1mm), set the anti-scattering slit (SS) (e.g., 8mm), and use a graphite monochromator. The micro stress is obtained after fitting the XRD pattern: MS = (Bhkl*Cosθhkl) / (4sinθhkl), where θhkl is the diffraction angle of the composite cathode material 10(hkl) crystal plane in the XRD pattern, and Bhkl is the half-height width of the composite cathode material 10(hkl) crystal plane in the XRD pattern.

[0122] In the embodiment, the BET specific surface area of ​​the composite positive electrode material 10 in each of the above embodiments can be 0.7 m 2 / g to 3.8m 2 / g, optional 1.35m 2 / g to 3.0m 2 / g; optional 1.35m 2 / g to 2.3m 2 / g, in this example, it can be 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1.0m 2 / g, 1.2m 2 / g, 1.35m 2 / g, 1.5m 2 / g, 1.8m 2 / g, 2m 2 / g, 2.3m 2 / g, 2.5m 2 / g, 2.8m 2 / g, 3.2m 2 / g, 3.5m 2 / g, 3.8m 2 / g and other typical but non-limiting specific surface area ranges. Among them, the BET specific surface area refers to the total area of ​​the composite positive electrode material 10 per unit mass. The specific surface area of ​​the composite positive electrode material 10 is controlled within the above range. Compared with the specific surface area in other ranges, the contact area between the composite positive electrode material 10 particles and the electrolyte can be appropriate. On the basis of giving full play to the high gram capacity of the composite positive electrode material 10, the stability of the contact interface between the composite positive electrode material 10 and the electrolyte can be relatively improved, and the side reactions of the contact interface can be reduced, thereby significantly improving the long-term performance of the composite positive electrode material 10, including the cycle performance; on the basis of improving the gram capacity performance of the composite positive electrode material 10, the gas production under high-temperature storage can also be reduced.

[0123] In the embodiments of the present application, the BET specific surface area of ​​the composite positive electrode material 10 can be tested using any known method. For example, the specific surface area of ​​the composite positive electrode material 10 can be tested with reference to GB / T19587-2017 "Determination of the specific surface area of ​​solid substances by the gas adsorption BET method". As an example, the specific surface area of ​​the composite positive electrode material 10 is measured using the TriStarII3020 device. The composite positive electrode material 10 is dispersed in a dispersant, such as ethanol, and after ultrasonication for 30 minutes, the material is placed in a vacuum drying oven to dry. Finally, the specific surface area of ​​the composite positive electrode material 10 is measured using a specific surface area tester.

[0124] In the embodiments, the composite positive electrode material 10 of each embodiment can be controlled by the particle size of its core 11 and the thickness of the coating layer 12, and the Dv50 particle size of the composite positive electrode material 10 can be 6.5μm to 11μm, optionally 7μm to 10.5μm. In the exemplary embodiment, it can be a typical but non-limiting particle size range consisting of any two values ​​such as 6.5μm, 7μm, 8μm, 9μm, 10μm, and 11μm. Controlling the Dv50 particle size of the composite positive electrode material 10 within the above range can increase the compaction density of the composite positive electrode material 10 particles and improve the structural stability of the composite positive electrode material 10 particles, and can simultaneously improve other electrochemical properties of the composite positive electrode material 10, including the first reversible capacity.

[0125] In the embodiments of the present application, the volume average particle size Dv50 of the material has a meaning well known in the art. The volume average particle size Dv50 of the material refers to the particle size corresponding to 50% in the volume distribution. It can be detected using equipment and methods well known in the art. A certain amount of composite material is taken as a sample, and the volume average particle size Dv50 is tested using a Malvern 300 laser particle size analyzer according to the test standard GB / T19077-2016 / ISO13320:2009 particle size distribution laser diffraction method.

[0126] Preparation method of composite positive electrode material

[0127] In a second aspect, the present invention provides a method for preparing the composite positive electrode material 10 of the present invention. The composite positive electrode material 10 of the present invention comprises the following steps:

[0128] Step S10: mixing the positive electrode material particles with the functional precursor to obtain a mixture;

[0129] Step S20: sintering the mixture to sinter the functional precursor into a coating layer 12, which is coated on at least a portion of the surface of the positive electrode material particles to form a composite positive electrode material 10, wherein the coating layer 12 includes a perovskite material and a fast ion conductor material.

[0130] The preparation method of the composite positive electrode material 10 of the embodiment of the present application adopts a functional precursor as a raw material, and directly forms a coating layer 12 containing a perovskite material and a fast ion conductor material on the surface of the positive electrode material particles containing a lithium-rich manganese-based positive electrode material, thereby generating the composite positive electrode material 10 of the embodiment of the present application with a core-shell structure as described above. Therefore, the positive electrode material particles as the core body 11 give the prepared composite positive electrode material 10 high electrochemical properties including gram capacity. The formed coating layer 12 can effectively improve the crystal structure stability of the lithium-rich manganese-based positive electrode material in the core body 11, alleviate the capacity decay of the lithium-rich manganese-based positive electrode material, and significantly improve the cycle performance of the composite positive electrode material 10. Moreover, the formed coating layer 12 has stable chemical properties, effectively enhances the stability of the interface between the prepared composite positive electrode material 10 and the electrolyte, and reduces gas production. In addition, the conditions for forming the coating layer 12 on the surface of the positive electrode material particles in the preparation method of the composite positive electrode material 10 of the embodiment of the present application are controllable, so that the prepared composite positive electrode material 10 has stable performance and high efficiency, and is suitable for industrial large-scale production and application.

[0131] Step S10:

[0132] The positive electrode material particles in step S10 are the core 11 contained in the composite positive electrode material 10 of the embodiment of the above application as shown in FIG1 . Therefore, the positive electrode material particles in step S10 are lithium-rich manganese-based positive electrode materials. Since the positive electrode material particles in step 10 are the core 11 contained in the composite positive electrode material 10 of the embodiment of the above application as shown in FIG1 . Therefore, the components contained, the particle size, etc. of the positive electrode material particles are the same as the components contained, the particle size, etc. of the core 11 contained in the composite positive electrode material 10 above.

[0133] The positive electrode material particles may be prepared according to a conventional positive electrode material preparation method, or may be prepared according to an improved conventional positive electrode material preparation method. For example, in the exemplary embodiment, when the positive electrode material particles are lithium-rich manganese-based positive electrode materials, specifically lithium-rich manganese-based positive electrode material particles, they may be prepared according to a conventional lithium-rich manganese-based positive electrode material preparation method, specifically lithium-rich manganese-based positive electrode material preparation method, or may be commercially available.

[0134] For example, the preparation method of lithium-rich manganese-based positive electrode materials is as follows: the raw material precursors (such as lithium salts, Me elements, compounds of M elements, etc.) and ball-milled zirconium beads are placed in a drum ball mill mixer according to a ball-to-material ratio of 25 to 80 for mixing, the Li / Me molar ratio is 1.3 to 1.4, Me is the total molar amount of nickel, cobalt, and manganese, the mixed material is placed in a muffle furnace for sintering, the sintering temperature is 780°C to 900°C, the heating rate is 2°C / min to 5°C / min, the sintering time is 10h to 15h, the sintering atmosphere is air, and the sintered material is mechanically ground and vibrated to obtain a lithium-rich manganese-based positive electrode material.

[0135] The functional precursor in step S10 can form the functional material in the coating layer 12 contained in the composite positive electrode material 10 of the above-mentioned embodiment of the application. For example, the functional precursor includes a perovskite precursor, and the perovskite precursor can form the perovskite material in the coating layer 12 contained in the composite positive electrode material 10 of the above-mentioned embodiment of the application. The perovskite precursor can be specifically selected and controlled according to the type of perovskite material. Specifically, the corresponding ABX3 perovskite precursor can be selected and controlled according to the type of ABX3 perovskite in the coating layer 12 contained in the composite positive electrode material 10 of the above-mentioned embodiment of the application.

[0136] Perovskite precursors may include lanthanum chloride (cation valence is +3), lanthanum nitrate, lanthanum acetate, strontium chloride (cation valence is +2), strontium nitrate, calcium oxide, calcium hydroxide, calcium chloride, calcium sulfate, aluminum fluoride (cation valence is +3), aluminum oxide, aluminum sulfate, zinc oxide (cation valence is +2), zinc chloride, zinc nitrate, zinc sulfate, zirconium fluoride (cation valence is +2, +3 or +4), zirconium chloride, titanium chloride, dioxygen One or more of titanium dioxide, titanium nitrate, titanium sulfate, tungsten oxide (cation valence is +2), tungstic acid, silicon dioxide, manganese chloride, manganese dioxide, cobalt nitrate, cobalt hydroxide (cation valence is +2 or +3), cobalt sulfate, gallium hydroxide (cation valence is +3), molybdenum oxide, niobium oxide, lanthanum chlorate, lanthanum cobaltate, lanthanum titanate, zirconium titanate, strontium titanate, ferric oxide, ruthenium oxide, iridium oxide, chromium oxide, germanium oxide, tantalum oxide, potassium hydroxide, etc. These precursors can be sintered during the sintering process in step S20 to generate the corresponding ABX3 perovskite mentioned above.

[0137] The fast ion conductor precursor can form the fast ion conductor material in the coating layer 12 contained in the composite positive electrode material 10 of the above-mentioned application embodiment. The fast ion conductor precursor can be selected and controlled according to the type of fast ion conductor material. Specifically, the fast ion conductor precursor corresponding to the type of fast ion conductor in the coating layer 12 contained in the composite positive electrode material 10 of the above-mentioned application embodiment can be selected and controlled.

[0138] The fast ion conductor precursor may include one or more of lithium phosphate, lithium hydrogen phosphate, lithium borate, boric acid, lithium sulfate, silicon dioxide, and lithium silicate.

[0139] The fast ion conductor precursor and the perovskite precursor are mixed and sintered together. The fast ion conductor precursor is sintered into a fast ion conductor, and the perovskite precursor is sintered into a perovskite material. The fast ion conductor precursor and the perovskite precursor may also react with each other, so that the synergistic effect between the coating layer and the lithium-manganese-rich positive electrode material is further enhanced.

[0140] In the embodiment, the mixing process of the positive electrode material particles and the functional precursor can be a dry mixing process or a solution mixing process.

[0141] The dry mixing process may be to directly mix the cathode material particles and the powder of the functional precursor without a solvent. In an embodiment, the dry mixing process may be to directly stir or ball-mill the mixture of the cathode material particles and the functional precursor.

[0142] The solution mixing process is relative to the dry mixing process described above. For example, in the embodiment, the functional precursor is prepared into a solution and then mixed with the positive electrode material particles to form a mixture slurry, which is then dried to remove the solvent, so that the functional precursor can form a precursor coating layer 12 to coat the surface of the positive electrode material particles. Alternatively, the functional precursor and the positive electrode material particles are mixed with a solvent to prepare a mixture slurry, which is then dried to remove the solvent, so that the functional precursor can form a precursor coating layer 12 to coat the surface of the positive electrode material particles.

[0143] During the mixing process of step S10 , the mass content and thickness of the coating layer 12 generated in step S20 can be adjusted by controlling the mixing ratio of the positive electrode material particles and the functional precursor.

[0144] For example, in the embodiment, by controlling the mixing ratio of the positive electrode material particles and the functional precursor, the mass ratio of the positive electrode material particles to the perovskite precursor in the functional precursor satisfies the mass ratio of the core 11 contained in the composite positive electrode material 10 of the above-mentioned embodiment of the application to the perovskite material in the coating layer 12, which is 100:(0.2-0.8), and can be optionally 100:(0.25-0.7). That is, in the embodiment, in step S10, the positive electrode material particles and the perovskite precursor are mixed according to a mass ratio of the positive electrode material particles to the perovskite material of 100:(0.2-0.8), and can be optionally 100:(0.25-0.7).

[0145] For example, in the embodiment, the mass ratio of the positive electrode material particles to the fast ion conductor precursor in the functional precursor satisfies the mass ratio of the core 11 to the fast ion conductor material in the coating layer 12 contained in the composite positive electrode material 10 of the above-mentioned embodiment of the application, which is 100:(0.05-10), and can be optionally 100:(0.1-5). That is, in the embodiment, in step S10, the positive electrode material particles and the fast ion conductor precursor are mixed according to a mass ratio of the positive electrode material particles to the fast ion conductor material of 100:(0.05-10), and can be optionally 100:(0.1-5).

[0146] By controlling the mixing process within the above-mentioned ratio range, the thickness of the coating layer 12 generated in step S20 can be controlled within the thickness range of 0.05 to 1 μm as mentioned above, and the content of elements contained in the generated perovskite material and fast ion conductor material can be within the required range, thereby improving the crystal structure stability of the lithium-rich manganese-based positive electrode material, improving the protective effect of the coating layer 12, and improving the stability of the interface between the composite positive electrode material 10 and the electrolyte.

[0147] Step 20:

[0148] During the sintering process of step 20, the functional precursor will be sintered to generate the functional material in the coating layer 12 contained in the composite positive electrode material 10 of the embodiment of the above application, and can form a coating layer 12 containing perovskite material and fast ion conductor material to coat the positive electrode material particles.

[0149] In the embodiment, the sintering temperature can be controlled to be 500°C to 750°C. This temperature range enables the perovskite precursor to be completely sintered to form a perovskite-containing material, and the fast ion conductor precursor to be sintered to form a fast ion conductor and coat the positive electrode material particles. At this sintering temperature, the sintering time should be sufficient. For example, in the embodiment, when the sintering temperature is 500°C to 750°C, the sintering time is 6h to 10h.

[0150] In an embodiment, the sintering process can be controlled to increase the temperature to the sintering process temperature at a heating rate of 2°C / min to 5°C / min. Controlling the heating rate within this range can effectively regulate the growth of perovskite crystals, enhance the oxygen buffer effect of the perovskite-containing coating layer 12, further reduce the oxygen release phenomenon of the lithium-rich manganese-based positive electrode material in the core body 11, and improve the stability of the interface between the composite positive electrode material 10 and the electrolyte.

[0151] In the embodiment, the sintering atmosphere may be air, and the sintered material is subjected to mechanical grinding and vibration screening to obtain the composite positive electrode material 10 .

[0152] positive electrode

[0153] In a third aspect, embodiments of the present application provide a positive electrode 20. In some embodiments, as shown in Figures 2 and 3, the positive electrode 20 of the present application includes a current collector 21 and an active layer 22 disposed on at least one side of the current collector 21. The active layer 22 is combined with the current collector 21. In the positive electrode 20 of the present application embodiment, the positive electrode material contained in the active layer 22 includes the composite positive electrode material 10 of the above-mentioned embodiment of the present application.

[0154] Since the positive electrode material contained in the active layer 22 of the positive electrode 20 of the embodiment of the present application includes the composite positive electrode material 10 of the embodiment of the present application, the positive electrode 20 of the embodiment of the present application not only has a high energy density, but also has good cycle performance, and its contact interface with the electrolyte is stable, which can effectively reduce gas production.

[0155] The current collector 21 included in the positive electrode 20 of the present embodiment refers to a structure or component used to collect current. In the embodiments, the current collector 21 included in the positive electrode 20 of the present embodiment includes, but is not limited to, a metal current collector, a carbon current collector, a conductive resin current collector, a metal-resin composite current collector, and more specifically, copper, nickel, titanium, iron, and their respective alloys, stainless steel, carbon fiber, carbon nanotubes (CNTs), graphite, and the like. In the embodiments, the current collector 21 can also be a dense film layer or a porous film layer.

[0156] The active layer 22 included in the positive electrode 20 of the present embodiment refers to a film layer containing a positive electrode material. In the embodiment, the active layer 22 included in the positive electrode 20 of the present embodiment is combined with the current collector 21 and can be laminated on the surface of the current collector 21. When the surface layer of the current collector 21 has a porous structure or the current collector 21 itself has a porous structure, the active layer 22 can be at least partially embedded in the current collector 21.

[0157] In an embodiment, when the active layer 22 is laminated on the surface of the current collector 21, it can be bonded to one surface of the current collector 21, as shown in Figure 2. When the current collector 21 has two opposing surfaces, that is, when it is a membrane structure, the active layer 22 can be bonded to two opposing surfaces of the current collector 21, as shown in Figure 3.

[0158] In the embodiment, the active layer 22 contained in the positive electrode 20 of the embodiment of the present application contains, in addition to the composite positive electrode material 10 of the embodiment of the present application, also includes necessary components such as the composite positive electrode material 10 and other components. The other components may include a binder or may further contain a conductive agent, other additives and other components.

[0159] In embodiments, when the active layer 22 contains a binder, the binder may include one or more of an oil-soluble binder, a water-soluble binder, an emulsion-type binder, and the like. In exemplary embodiments, the oil-soluble binder may include one or more of polyvinylidene fluoride, polyimide, polytetrafluoroethylene, polybutyl acrylate, and polyacrylonitrile; in exemplary embodiments, the water-soluble binder may include one or more of carboxymethyl cellulose, carboxymethyl cellulose salts, polyacrylic acid, polyacrylates, polyvinyl alcohol, sodium alginate, and cyclodextrin; and in exemplary embodiments, the emulsion-type binder may include one or more of styrene-butadiene rubber, vinyl acetate resin, acrylic resin, and chlorinated rubber. In some embodiments, the binder comprises ≤5% by mass based on the total mass of the active layer 22.

[0160] In an embodiment, when the active layer 22 contains a conductive agent, the conductive agent may include one or more of acetylene black (SP), carbon nanotubes, conductive carbon black (super-P), Ketjen black, carbon fiber, graphene, etc. In some embodiments, the weight percentage of the conductive agent based on the total weight of the active layer 22 is ≤5%.

[0161] In the embodiment, when the active layer 22 contains other additives, the additives may include but are not limited to functional components such as lithium supplements.

[0162] The materials such as the composite positive electrode material 10 , the binder and the conductive agent can be selected specifically according to the application or production requirements of the positive electrode 20 .

[0163] The positive electrode 20 of the embodiment of the present application can be prepared according to the conventional preparation method of the positive electrode 20, for example, it may include the following steps: preparing a slurry containing the above-mentioned composite positive electrode material 10 and a binder and a solvent or further containing components such as a conductive agent and other additives, and forming the slurry into a film (wet film) on the current collector 21; then performing a drying process to evaporate the solvent, thereby drying the wet film; and then rolling the dried film layer to form an active layer 22, thereby obtaining the positive electrode 20.

[0164] Battery

[0165] In a fourth aspect, the present invention further provides a battery. The battery comprises a positive electrode 20 and a negative electrode, wherein the positive electrode 20 is the positive electrode 20 described in the above embodiment of the present invention.

[0166] Since the battery of the embodiment of the present application contains the positive electrode 20 of the embodiment of the present application, the battery of the embodiment of the present application has good cycle performance, low gas production, and relatively high safety on the basis of electrochemical properties such as high energy density.

[0167] In the embodiment, the negative electrode contained in the battery of the embodiment of the present application can be a conventional negative electrode. For example, in the embodiment, it can be a negative electrode that matches the positive electrode 20 of the embodiment of the present application.

[0168] [negative electrode]

[0169] In some embodiments, the negative electrode includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and comprising a negative electrode active material. For example, the negative electrode current collector has two opposing surfaces in the thickness direction of the negative electrode current collector, and the negative electrode film layer is disposed on either or both of the two opposing surfaces of the negative electrode current collector.

[0170] The negative electrode active material can be any negative electrode active material known in the art for use in battery cells. For example, the negative electrode active material may include, but is not limited to, one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials may include one or more of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxide, and tin alloys.

[0171] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. The present application does not particularly limit the type of negative electrode conductive agent. For example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the negative electrode conductive agent based on the total weight of the negative electrode film layer is ≤5%.

[0172] In some embodiments, the negative electrode film layer may further optionally include a negative electrode binder. The present application embodiment does not particularly limit the type of negative electrode binder. As an example, the negative electrode binder may include one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, the mass percentage of the negative electrode binder is ≤5% based on the total weight of the negative electrode film layer.

[0173] In some embodiments, the negative electrode film layer may optionally include other additives. For example, the other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, and the like. In some embodiments, the weight percentage of the other additives is ≤ 2% based on the total weight of the negative electrode film layer.

[0174] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0175] The negative electrode film layer is typically formed by coating the negative electrode slurry onto the negative electrode current collector, drying it, and cold pressing it. The negative electrode slurry is typically formed by dispersing the negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0176] The negative electrode does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode of the embodiments of the present application further includes a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode of the embodiments of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0177] Of course, the battery of the present invention may include other necessary components or auxiliary components in addition to the above-mentioned electrodes. For example, when the battery of the present invention is an ion battery, the battery of the present invention may include components or parts such as a separator and an electrolyte.

[0178] [Diaphragm]

[0179] The battery cell also includes a separator.

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

[0181] In some embodiments, the material of the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0182] [Electrolyte]

[0183] During the charge and discharge process of the battery cell, active ions are intercalated and released back and forth between the positive electrode 20 and the negative electrode, and the electrolyte plays a role in conducting active ions between the positive and negative electrodes. The embodiments of this application do not specifically limit the type of electrolyte, and can be selected according to actual needs.

[0184] The electrolyte solution includes an electrolyte salt and a solvent. The types of the electrolyte salt and the solvent are not particularly limited and can be selected according to actual needs.

[0185] As an example, the electrolyte salt may include, but is not limited to, one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0186] As an example, the solvent may include, but is not limited to, one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS) and diethyl sulfone (ESE).

[0187] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, or additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature power performance.

[0188] In the embodiments, the batteries of the above embodiments may include any one of a battery cell, a battery module, and a battery pack.

[0189] A battery cell is a battery cell comprising a battery housing and an electrode assembly (also known as a bare cell) encapsulated within the housing. The shape of a battery cell is not particularly limited and can be cylindrical, square, or any other shape. In one example, the battery cell may be a square-shaped battery cell 30 as shown in FIG4 .

[0190] In some embodiments, as shown in Figure 5, the outer packaging of the battery cell 30 may include a shell 31 and a cover plate 33. The shell 31 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 31 has an opening connected to the receiving cavity, and the cover plate 33 is used to cover the opening to close the receiving cavity. The positive electrode 20, diaphragm and negative electrode contained in the battery cell 30 of the embodiment of the present application can be formed into an electrode assembly 32 through a winding process and / or a lamination process. The electrode assembly 32 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 32. The number of electrode assemblies 32 contained in the battery cell 30 can be one or more, which can be adjusted according to actual needs.

[0191] In some embodiments, the preparation method of the battery cell 30 may be to assemble the positive electrode 20, separator, negative electrode, and electrolyte of the embodiment of the above-mentioned application to form the battery cell 30. As an example, the positive electrode 20, separator, and negative electrode of the embodiment of the above-mentioned application may be wound or laminated to form an electrode assembly 32. The electrode assembly 32 is placed in an outer package, dried, and then injected with electrolyte. The battery cell 30 is obtained through vacuum packaging, static standing, chemical formation, and shaping. Since the battery cell 30 contains the positive electrode 20 of the embodiment of the above-mentioned application, the electrode assembly 32 may be wound or laminated to form an electrode assembly 32. The electrode assembly 32 may be placed in an outer package, dried, and then injected with electrolyte. The battery cell 30 may be obtained through vacuum packaging, static standing, chemical formation, and shaping.

[0192] In the embodiment, when the battery of the embodiment of the present application is a battery module, the battery module refers to being assembled from the battery cells 30, that is, it can contain multiple battery cells 30, and the specific number can be adjusted according to the application and capacity of the battery module.

[0193] In some embodiments, FIG6 is a schematic diagram of an exemplary battery module 40. As shown in FIG6 , in the battery module 40, multiple battery cells 30 may be arranged sequentially along the length of the battery module 40. Of course, any other arrangement is also possible. Furthermore, the multiple battery cells 30 may be secured using fasteners.

[0194] Optionally, the battery module 40 may further include a housing having an accommodation space, and the plurality of battery cells 30 may be accommodated in the accommodation space.

[0195] A battery pack is assembled from the battery cells 30 described above, and may contain multiple battery cells 30, wherein multiple battery cells 30 may be assembled into the battery module 40 described above. The specific number of battery cells 30 or battery modules 40 contained in a battery pack may be adjusted according to the application and capacity of the battery pack.

[0196] In the embodiment, Figures 7 and 8 are schematic diagrams of an exemplary battery pack 50. The battery pack 50 may include a battery box and multiple battery modules 40 disposed within the battery box. The battery box includes an upper box body 51 and a lower box body 52. ​​The upper box body 51 covers the lower box body 52 and forms an enclosed space for accommodating the battery modules 40. The multiple battery modules 40 may be arranged in any manner within the battery box.

[0197] Electrical devices

[0198] In the fifth aspect, the embodiments of the present application also provide an electric device. The electric device of the embodiments of the present application includes a power supply unit or an energy storage unit, and of course may also include other auxiliary components or necessary components. Among them, the power supply unit or energy storage unit contains the battery of the above-mentioned embodiment of the application. The battery contained in the power supply unit or energy storage unit may be one or more. When there are multiple batteries, multiple batteries can form a battery module or battery pack. Since the electric device of the embodiments of the present application contains the battery of the above-mentioned embodiment of the application, the power supply unit or energy storage unit of the electric device of the embodiments of the present application has high energy density, good cycle performance, long service life, and high safety, and the electric device of the embodiments of the present application has a long standby or battery life time and high safety in use.

[0199] Figure 9 is a schematic diagram of an exemplary electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of this device, a battery pack or battery module may be used.

[0200] As another example, the electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be lightweight and thin, and may use a secondary battery as a power source.

[0201] In the embodiment, when the electrical device includes an energy storage unit, the electrical device may be an energy storage device, and the energy storage device includes the energy storage unit, and of course may also include other auxiliary components or necessary components. Among them, the energy storage unit contains the battery of the embodiment of the above text application. The battery contained in the energy storage unit may be one or more. When there are multiple batteries, multiple batteries can form a battery module or battery pack. Since the energy storage device of the embodiment of the present application contains the battery of the embodiment of the above text application, the energy storage device has high energy storage density, good cycle performance, long service life, and high safety.

[0202] Example

[0203] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0204] Example 1

[0205] Composite positive electrode material and preparation method thereof

[0206] This embodiment provides a composite positive electrode material and a method for preparing the same. The composite positive electrode material comprises lithium-rich manganese-based positive electrode material particles coated with a coating comprising LaAlO3 and Li3PO4. The relevant parameters of the lithium-rich manganese-based positive electrode material particles and the coating are shown in the following table.

[0207] The preparation method of the composite positive electrode material comprises the following steps:

[0208] S1. Preparation of lithium-rich manganese-based positive electrode material particles: According to the molecular formula Li 1.17 Mn 0.58 Ni 0.24 Ti 0.01 The molar ratio of elements contained in the O2 lithium-rich manganese-based positive electrode material is as follows: Li2CO3 lithium salt, MnSO4·H2O manganese salt, CoSO4·7H2O cobalt salt, and TiO2 precursor compounds are accurately weighed, and each precursor compound is mixed with ball-milled zirconium beads in a drum ball mill mixer according to a ball material of 60:1 to obtain a precursor mixture; the precursor mixture is placed in a muffle furnace for sintering treatment, the sintering temperature is 800℃, the heating rate is 2℃ / min, the sintering time is 10h, the sintering atmosphere is air, and the sintered material is mechanically ground and vibrated to obtain a molecular formula Li 1.17 Mn 0.58 Ni 0.24 Ti 0.01 O2-rich lithium manganese-based cathode material particles;

[0209] S2. Preparation of perovskite coating on the surface of lithium-rich manganese-based cathode material particles:

[0210] The perovskite precursor material aluminum sulfate and the fast ion conductor precursor material lithium hydrogen phosphate are placed in a drum ball mill mixer and mixed for 10 hours. Subsequently, the lithium-rich manganese-based positive electrode material particles obtained in S1 are added to the drum ball mill mixer and mixed again for 10 hours. The mixture is then placed in a muffle furnace for sintering. The sintering temperature is 700°C, the heating rate is 3°C / min, the sintering time is 9 hours, and the sintering atmosphere is air. After sintering, the material is mechanically ground and vibrated to obtain a composite positive electrode material of perovskite-coated lithium-rich manganese-based positive electrode material.

[0211] Example 2 to Example 4

[0212] The positive electrodes provided in Examples 2 to 4 are different from those in Example 1 in that the mass ratio of the perovskite material to the core body is adjusted.

[0213] Example 5 to Example 8

[0214] The positive electrodes provided in Examples 5 to 8 are different from those in Example 1 in that the mass ratio of the fast ion conductor material to the core is adjusted.

[0215] Example 9 to Example 13

[0216] The positive electrodes provided in Examples 9 to 13 are different from those in Example 1 in that the type of perovskite material is adjusted.

[0217] Example 14 to Example 16

[0218] The positive electrodes provided in Examples 14 to 16 are different from those in Example 1 in that the material of the fast ion conductor is adjusted.

[0219] Comparative Example 1

[0220] The positive electrode provided in Comparative Example 1 is different from that in Example 1 in that no coating layer is provided.

[0221] Comparative Example 2

[0222] The positive electrode provided in Comparative Example 2 is different from that in Example 1 in that the coating layer includes a fast ion conductor.

[0223] Comparative Example 3

[0224] The positive electrode provided in Comparative Example 3 is different from that in Example 1 in that the coating layer includes a perovskite material.

[0225] Positive electrode and battery examples

[0226] This embodiment provides a positive electrode and a battery cell (full battery) containing the positive electrode. The battery cell of this embodiment includes an electrode assembly formed by a positive electrode, a separator, and a negative electrode, and also includes an electrolyte. The positive electrode contains the composite positive electrode material described in the above embodiment.

[0227] Preparation of the positive electrode: The composite positive electrode material in the above embodiment is placed in a mixing tank and premixed for 30 minutes. Then, the conductive agent acetylene black (SP) and the binder polyvinylidene fluoride (PVDF) are added for secondary dry mixing for 30 minutes. Then, the solvent N-methylpyrrolidone (NMP) is added and rapidly stirred under vacuum conditions to form a slurry. The mass ratio of composite positive electrode material: acetylene black: polyvinylidene fluoride is 96:2:2, and the solid content of the slurry is 70% by weight. The slurry is evenly coated on both sides of a 12μm thick aluminum foil. The coated electrode is dried in an oven at 100-130℃ for half an hour and then removed. The positive electrode material loading of the electrode is 21.5mg / cm 2 ; The positive electrode taken out is subjected to roller cold pressing treatment to obtain the positive electrode.

[0228] Preparation of the negative electrode: The negative electrode materials artificial graphite, hard carbon, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are fully stirred and mixed evenly in a deionized water solvent system according to a weight ratio of 90:5:2:2:1, and then coated on a copper foil, dried, and cold-pressed to obtain the negative electrode.

[0229] Separator: A polyethylene porous polymer film with a thickness of 12 μm.

[0230] Electrolyte: 1 mol / L lithium salt LiPF6, and the solvent includes EC + EMC + DMC with a volume ratio of 1:1:1.

[0231] Battery cell: Stack the positive electrode, separator, and negative electrode in sequence, with the separator in the middle of the positive and negative electrodes to play an isolation role, and wind them to obtain a bare battery core; place the bare battery core in an outer package, inject the prepared basic electrolyte, and encapsulate it to obtain a full battery.

[0232] Performance testing of the full battery cell:

[0233] (1) Battery gas generation detection method:

[0234] At 60 °C, store the full battery in a 100% charged state (SOC). Measure the open circuit voltage (OCV) and AC internal resistance (IMP) of the battery before, during, and after storage to monitor the SOC, and measure the volume of the battery. Among them, after storing the full battery for every 48 h, take it out, let it stand for 1 h, and then test the OCV and IMP. After cooling to room temperature, measure the volume of the battery core by the drainage method. The drainage method is to first measure the gravity F1 of the battery alone with a balance that can automatically perform unit conversion of the dial data, and then place the battery completely in deionized water (with a known density of 1 g / cm 3 ) and measure the gravity F2 of the battery at this time. The buoyancy F_float of the battery is F1 - F2. Then, according to Archimedes' principle F_float = ρgV_drain, where V_drain is the drainage volume, calculate the battery volume V = V_drain = (F1 - F2) / ρg.

[0235] After each volume test, charge the battery. Charge it at a constant current of 0.5C to 4.45V, and then charge it at a constant voltage of 4.45V until the current drops to 0.05C. After the charging is completed, put it into the furnace and continue the test.

[0236] After storing for 30 days, measure the volume of the battery, and calculate the ratio of the increase in the battery volume after storage to the battery capacity relative to the battery volume before storage, that is, the gas generation per unit volume mL / Ah.

[0237] (2) Battery cell cycle retention rate (%):

[0238] Take a full battery cell as the test object, in a constant temperature environment of 25°C, at a voltage of 2.5V to 4.45V, at a rate of 0.5C, then charge at a constant voltage at 4.45V to a current ≤ 0.05mA, let it stand for 5 minutes, and then discharge at a rate of 0.2C to 2.5V, record the discharge capacity, repeat the previous process, and obtain the capacity retention rate after a specified number of cycles, for example 500 cycles, capacity retention rate = first cycle discharge capacity / discharge capacity at a specified number of cycles × 100%.

[0239] (3) Testing method for measuring storage performance of battery cells:

[0240] In a constant temperature environment of 25°C, let it stand for 5 minutes, discharge it to 2.5V at 1 / 3C, let it stand for 5 minutes, charge it to 4.5V at 1 / 3C, then charge it at constant voltage at 4.5V to a current of ≤0.05mA, let it stand for 5 minutes. The charge capacity at this time is recorded as C0. Then discharge it to 2.8V at 1 / 3C. The discharge capacity at this time is the initial gram capacity, recorded as D0.

[0241] The battery was then charged at a constant current of 0.33C to 4.5V and constant voltage to a current ≤ 0.05mA, left to stand for 5 minutes, and finally placed in a high and low temperature box at 60°C. It was left to stand for 1 hour until the battery temperature reached the target temperature and then stored. After 15 days, the battery was taken out and the previous process was repeated in a constant temperature environment of 25°C. The capacity Dn (n = 0, 1, 2...) was recorded every 15 days, and the capacity retention rate after 60 days of storage was calculated as: (D4-D0) / D0*100%.

[0242] Test results

[0243] The test results are shown in Tables 1 to 4.

[0244] Table 1

[0245] In Table 1,

[0246] The composite positive electrode material in Comparative Example 1 is a core lithium manganese-based positive electrode material, and its molecular formula is Li 1.17 Mn 0.58 Ni 0.24 Ti 0.01 O2.

[0247] The composite positive electrode materials in Comparative Examples 2 and 3 and Examples 1 to 16 include a core body and a coating layer, and the molecular formula of the core body lithium manganese-based positive electrode material is Li 1.17 Mn 0.58 Ni 0.24 Ti 0.01 O2.

[0248] The initial gram capacity of the composite positive electrode material in Comparative Example 1 is 214.5 mAH / g, and the initial gram capacity of the composite positive electrode material in Comparative Example 3 is 210.3 mAH / g. The perovskite material in Comparative Example 3 may undergo side reactions with active lithium, resulting in a slight deterioration in the gram capacity; the coating layer in Example 1 includes perovskite material and fast ion conductor material. The combined effect of the two can reduce the risk of side reactions between the perovskite material and active lithium, and can further improve the kinetic performance, increase the gram capacity, and is beneficial to improving the first-cycle coulombic efficiency of the battery. The initial gram capacity of the composite positive electrode material in Example 1 is 216.6 mAH / g.

[0249] The composite positive electrode material of the embodiment of the present application has an appropriate range of dislocation density, microstress and specific surface area, so that the composite positive electrode material of the embodiment of the present application has good mechanical properties such as particle structure strength, and the electrochemical properties such as voltage stability and stability of the contact interface with the electrolyte are improved.

[0250] Table 2

[0251] As can be seen from Table 2,

[0252] In Comparative Example 1, no coating layer is provided on the surface of the lithium-rich manganese-based positive electrode material, and its cycle performance and storage performance are relatively poor, and the storage gas production is relatively high.

[0253] Compared with Comparative Example 1, Comparative Example 2 sets a coating layer on the surface of the lithium-rich manganese-based positive electrode material, and the coating layer includes a fast ion conductor; Comparative Example 3 sets a coating layer on the surface of the lithium-rich manganese-based positive electrode material, and the coating layer includes a perovskite material, which improves the performance of the composite positive electrode material to a certain extent and can improve the storage performance and cycle performance of the battery cell, but the improvement effect is not significant.

[0254] Compared to Comparative Example 2, where the coating layer only includes a fast ion conductor, and Comparative Example 3, where the coating layer only includes a perovskite material, Examples 1 to 16 simultaneously provide a fast ion conductor material and a perovskite material on the surface of the lithium-rich manganese-based positive electrode material. The battery cells have relatively higher storage performance and cycle performance, and relatively low gas production. As shown in Figure 10, which is a scanning electron microscope (SEM) image of the composite positive electrode material of Example 1, the surface coating of the composite positive electrode material is uniform, providing excellent protection for the lithium-rich manganese-based positive electrode material and improving its performance.

[0255] By regulating the mass ratio of perovskite material to core body, the oxygen release problem of lithium-rich manganese-based positive electrode materials can be further improved, and the stability of the crystal structure of lithium-rich manganese-based positive electrode materials can be improved; especially when the mass ratio of perovskite material to core body is 0.2:100 to 0.8:100, and can be further selected as 0.25:100 to 0.8:100, the oxygen release problem can be further improved; when it can be further selected as 0.25:100 to 0.70:100, the oxygen release problem of the composite positive electrode material is significantly improved.

[0256] By regulating the mass ratio of the fast ion conductor material to the core body, the combined effect of the fast ion conductor material and the perovskite material can further improve the storage performance and cycle performance of the battery cell; especially when the mass ratio of the fast ion conductor material to the core body is 0.05:100 to 10:100, and can be further selected as 0.1:100 to 10:100, the storage performance and cycle performance can be further improved, and the gas production can be further reduced; when it can be further selected as 0.1:100 to 0.5:100, the storage performance and cycle performance can be further improved.

[0257] By regulating at least one of the type of perovskite material and the material of the fast ion conductor, the storage performance and cycle performance of the battery cell can be further improved.

[0258] Example 17 and Example 18

[0259] The positive electrodes provided in Examples 17 and 18 are different from those provided in Example 1 in that the material of the core is adjusted.

[0260] Example 19 and Example 20

[0261] The positive electrodes provided in Examples 19 and 20 are different from those in Example 1 in that the Dv50 of the composite positive electrode material is adjusted.

[0262] Table 3

[0263] Table 4

[0264] It can be seen from Tables 3 and 4 that by regulating the core material and the particle size Dv50 of the composite positive electrode material, the cycle performance and storage performance of the battery cell can be improved to a certain extent, and the gas production can be regulated.

[0265] Although illustrative embodiments have been shown and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on the present application, and that changes, substitutions, and modifications may be made to the embodiments without departing from the spirit, principles, and scope of the present application.

Claims

1. A composite cathode material comprising: a core body comprising a lithium-rich manganese-based cathode material; as well as The coating layer is coated on at least a portion of the surface of the core body, and the coating layer includes a perovskite material and a fast ion conductor material.

2. The composite cathode material according to claim 1, wherein Based on the total mass of the composite positive electrode material, the ratio of the mass content of the perovskite material to the mass content of the core body is (0.2 to 0.8):

100.

3. The composite cathode material according to claim 2, wherein The ratio of the mass content of the perovskite material to the mass content of the core body is (0.25 to 0.7):

100.

4. The composite cathode material according to any one of claims 1 to 3, wherein Based on the total mass of the composite positive electrode material, the ratio of the mass content of the fast ion conductor material to the mass content of the core body is (0.05 to 10):

100.

5. The composite cathode material according to claim 4, wherein The ratio of the mass content of the fast ion conductor material to the mass content of the core body is (0.1 to 0.5):

100.

6. The composite cathode material according to any one of claims 1 to 5, wherein The perovskite material has a cubic phase crystal structure.

7. The composite cathode material according to claim 6, wherein The perovskite material includes a compound with a molecular formula of ABX3, A includes one or more elements selected from La, Sr, Ca, Al, Zn, Zr, and K, B includes one or more elements selected from Fe, Ti, Mo, Ga, Ru, Zr, Ir, Co, W, Si, Mn, Nb, Ta, Ge, Cr, and Al, and X includes one or more elements selected from O, F, and Cl.

8. The composite cathode material according to claim 7, wherein The ABX3 includes one or more of LaFeO3, LaTiO3, LaMoO3, LaGaO3, LaRuO3, LaIrO3, LaAlO3, LaGaO3, SrTiO3, SrZrO3, SrCrO3, SrCoO3, SrGeO3, SrMnO3, LaCoO3, ZnTaO3, ZnIrO3, and KNbO3.

9. The composite cathode material according to any one of claims 6 to 8, wherein The total content of elements A and B in the perovskite material in the composite cathode material is 1500 ppm to 6000 ppm; or The content of the X element in the perovskite material in the composite positive electrode material is 440 ppm to 1800 ppm.

10. The composite cathode material according to claim 9, wherein The total content of elements A and B in the perovskite material in the composite cathode material is 1900 ppm to 5500 ppm; or The content of the X element in the perovskite material in the composite positive electrode material is 550 ppm to 1600 ppm.

11. The composite cathode material according to any one of claims 1 to 10, wherein The ionic conductivity of the fast ion conductor material is 10 -5 S / cm to 10 -2 S / cm.

12. The composite cathode material according to claim 11, wherein The ionic conductivity of the fast ion conductor material is 10 -5 S / cm to 6×10 -3 S / cm.

13. The composite cathode material according to any one of claims 1 to 12, wherein The fast ion conductor material includes one or more of lithium phosphate Li3PO4, lithium borate Li3BO3, lithium sulfate Li2SO4, and lithium silicate Li2SiO3.

14. The composite cathode material according to claim 13, wherein The content of Li element in the fast ion conductor material in the composite positive electrode material is 80 ppm to 19000 ppm; or The total content of P, B, S and Si elements in the fast ion conductor material in the composite positive electrode material is 100 ppm to 28000 ppm.

15. The composite cathode material according to claim 14, wherein The content of Li element in the fast ion conductor material in the composite positive electrode material is 150ppm to 1000ppm; or The total content of P, B, S and Si elements in the fast ion conductor material in the composite positive electrode material is 250 ppm to 1500 ppm.

16. The composite cathode material according to any one of claims 1 to 15, wherein The lithium-rich manganese-based positive electrode material includes a molecular formula of Li[Li x Ni a Co b Mn c M d ]O2 compounds, wherein x+a+b+c+d=1, x>0, a+b+c+d<1, 0≤b<1, and M includes one or more of Mg, Nb, Cr, Ce, Fe, Ta, Al, V, Ti, Zr, Sn and Mo.

17. The composite cathode material according to any one of claims 1 to 16, wherein The coating layer has a thickness of 0.05 μm to 1.00 μm.

18. The composite cathode material according to any one of claims 1 to 17, wherein The composite cathode material satisfies one or more of the following conditions: (1) The dislocation density of the composite positive electrode material is 1.55×10 11 cm -2 to 3.7×10 11 cm -2 ; (2) The microstress of the composite positive electrode material is 0.3% to 5.0%; (3) The specific surface area of ​​the composite positive electrode material is 0.7 m 2 / g to 3.8m 2 / g; (4) The Dv50 particle size of the composite positive electrode material is 6.5 μm to 11 μm.

19. The composite cathode material according to claim 18, wherein The composite cathode material satisfies one or more of the following conditions: (1) The microstress of the composite positive electrode material is 0.3% to 1.0%; (2) The specific surface area of ​​the composite positive electrode material is 1.35 m 2 / g to 3.0m 2 / g; (3) The Dv50 particle size of the composite positive electrode material is 7 μm to 10.5 μm.

20. The composite cathode material according to any one of claims 1 to 19, wherein The composite cathode material, ascorbic acid and water are mixed to form a mixed system, wherein the mass content of the composite cathode material is 2.0 wt %, and the mass content of the ascorbic acid is 0.2 wt %; The mixed system and nitric acid are mixed in a volume ratio of 1:2, and the dissolution amount DM of the Mn element in the composite positive electrode material is measured after mixing, wherein: DM≤140μg / L.

21. The composite cathode material according to claim 20, wherein DM≤80μg / L.

22. A method for preparing a composite positive electrode material, comprising: mixing the cathode material particles and the functional precursor to obtain a mixture; The mixture is sintered to sinter the functional precursor into a coating layer, which is coated on at least a portion of the surface of the positive electrode material particles to form a composite positive electrode material, wherein the coating layer includes a perovskite material and a fast ion conductor material.

23. A positive electrode comprising the composite positive electrode material according to any one of claims 1 to 21 or the composite positive electrode material prepared by the preparation method according to claim 22.

24. A battery comprising the positive electrode according to claim 23.

25. An electrical device comprising the battery according to claim 24.

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