A composite cathode material, a battery cell and its preparation method, a battery device, and an electrical device.

Abstract

This application relates to the field of battery technology, and more particularly to a composite cathode material, a battery cell, a method for preparing the same, a battery device, and an electrical device. The battery cell includes a cathode electrode, which includes a cathode active layer. The cathode active layer includes a composite cathode material, which includes a core, a first shell layer covering the outer surface of the core, and a second shell layer covering the outer surface of the first shell layer. The core includes a lithium-rich manganese-based cathode material, the first shell layer includes a fluoride, and the second shell layer includes a first solid electrolyte. The battery cell provided by this application, due to the core-shell structure of the composite cathode material, allows the first and second shell layers to form a good physical barrier. This confines oxygen generated by the lithium-rich manganese-based cathode material within the shell layer, preventing oxygen from diffusing to other parts of the battery. This allows the battery to maintain a high capacity during long-term use and extends its lifespan.

Description

Technical Field

[0001] This application belongs to the field of battery technology, and particularly relates to a composite cathode material, a battery cell and its preparation method, a battery device, and an electrical device. Background Technology

[0002] Currently, judging from market trends, the application of power batteries is becoming increasingly widespread. Power batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars. With the continuous expansion of power battery applications, people are placing higher demands on the lifespan of new energy vehicles. This demand translates into requirements for battery cycle performance.

[0003] The above statements are for the purpose of providing background information in relation to this application only and do not necessarily constitute prior art. Summary of the Invention

[0004] The purpose of this application is to provide a composite cathode material, a battery cell and its preparation method, a battery device, and an electrical device, aiming to solve the problem of unsatisfactory cycle life of battery cells.

[0005] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:

[0006] In a first aspect, this application provides a battery cell including a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive active layer disposed on at least one side of the positive current collector, the positive active layer including a composite positive electrode material, the composite positive electrode material including a core, a first shell layer covering the outer surface of the core and a second shell layer covering the outer surface of the first shell layer, the core including a lithium-rich manganese-based positive electrode material, the first shell layer including a fluoride, and the second shell layer including a first solid electrolyte.

[0007] In this application's technical solution, the composite cathode material has a core-shell structure, specifically a single-core double-shell structure. On one hand, the shell layer, composed of the first and second shell layers, forms a good physical barrier, thus confining the oxygen generated by the anion redox reaction of the lithium-rich manganese-based cathode material within the shell layer, preventing oxygen from diffusing to other parts of the battery. This reduces the negative impact of oxygen on battery performance. Furthermore, because oxygen is not easily released, the anion redox reaction can proceed under relatively stable conditions, improving the reversibility of the redox reaction. Therefore, during charging, sufficient oxygen elements participate in the redox reaction in the composite cathode material, enabling it to store more energy. This allows the battery to maintain a high capacity during long-term use and extends its lifespan. On the other hand, fluorides have high stability and chemical inertness; therefore, the first shell layer containing fluorides can effectively isolate the lithium-rich manganese-based cathode material. The contact between the fluoride and the first solid electrolyte suppresses side reactions between the lithium-rich manganese-based cathode material and other components such as the electrolyte, thus significantly reducing the risk of structural damage and performance degradation of the composite cathode material caused by side reactions. This has a significant positive effect on improving the cycle life of the battery. On the other hand, both the fluoride and the first solid electrolyte have good ionic conductivity, so they work together to form a stable and continuous ion conduction network. This double-shell structure makes the transport of lithium ions between different material interfaces smoother, which can significantly improve the transport kinetics of lithium ions in the lithium-rich manganese-based cathode material, increase the speed and efficiency of lithium ion transport, and reduce energy loss caused by interface resistance. In this way, lithium ions can be transported smoothly in the composite cathode material, thereby reducing structural changes and side reactions of the composite cathode material. This can reduce the capacity decay of the battery during cycling, thereby extending the cycle life of the battery.

[0008] In some embodiments, the fluoride includes lithium-containing fluorides. These fluorides have good ion conduction properties, thereby improving the ionic conductivity of the composite cathode material.

[0009] In some embodiments, the fluoride includes at least one of Li3AlF6, Li3GaF6, Li3ScF6, Li2ZrF6, and LiBF4.

[0010] These fluorides have a high voltage window and chemical stability, making them less likely to react with lithium-rich manganese-based cathode materials or other components in the battery, thereby effectively improving the structural stability of the composite cathode material.

[0011] In some embodiments, the mass percentage of fluoride is 0.1%-5% based on the total mass of the core described above.

[0012] By controlling the mass percentage of fluoride within the above range, a stable and uniform first shell layer can be constructed on the core surface, which can effectively isolate the lithium-rich manganese-based cathode material from the electrolyte and the external environment, reduce the occurrence of side reactions, and help improve the cycle life of the battery.

[0013] In some embodiments, the lithium-rich manganese-based cathode material includes a first lithium-rich manganese-based cathode material and a second lithium-rich manganese-based cathode material, wherein the first lithium-rich manganese-based cathode material has a layered structure and the second lithium-rich manganese-based cathode material has a spinel structure.

[0014] The first lithium-rich manganese-based cathode material with a layered structure has a high capacity and can provide high energy storage for the battery. The second lithium-rich manganese-based cathode material with a spinel structure does not undergo anion redox reactions, which means that the second lithium-rich manganese-based cathode material does not release oxygen during charging and discharging, and is not prone to capacity decay. The combination of these two gives the battery high capacity and cycle life.

[0015] In some embodiments, the core includes a core and a transition layer covering the core, wherein the core is formed of a first lithium-rich manganese-based cathode material and the transition layer is formed of a second lithium-rich manganese-based cathode material.

[0016] The second lithium-rich manganese-based cathode material has good ion diffusion capability and does not release oxygen during charging and discharging. Thus, the second lithium-rich manganese-based cathode material is coated on the outer surface of the first lithium-rich manganese-based cathode material, which can further suppress oxygen release, reduce the risk of capacity decay, and improve the cycle capacity of the battery.

[0017] In some embodiments, the thickness of the transition layer is 0.1 nm to 10 nm.

[0018] Within this range, the release of oxygen from the core can be effectively reduced, thereby avoiding battery capacity degradation and improving battery cycle life.

[0019] In some embodiments, the chemical formula of the first lithium-rich manganese-based cathode material is xLi2MnO3·(1-x)LiMO2, wherein M includes at least one of Ni, Co, Mn, Cr, Fe, Al, Nb, Zr, Mo, and Ta, and 0≤x≤1.

[0020] These first lithium-rich manganese-based cathode materials have high specific capacity, thereby improving the energy density of the battery.

[0021] In some embodiments, the chemical formula of the second lithium-rich manganese-based cathode material is LiN. y Mn z O4, where y+z=2, and N includes at least one of Ni, Co, Cr, Fe, Al, Nb, Zr, Mo, and Ta.

[0022] These second lithium-rich manganese-based cathode materials do not release oxygen during charging and discharging, thus improving battery safety.

[0023] In some embodiments, the mass percentage of the first solid electrolyte is 0.1%-5% based on the total mass of the core described above.

[0024] By controlling the mass percentage of the first solid electrolyte within the aforementioned range, a stable and uniform shell can be constructed on the core surface, thereby effectively isolating the lithium-rich manganese-based cathode material from the electrolyte and the external environment, reducing the occurrence of side reactions, which helps to improve the cycle life of the battery.

[0025] In some embodiments, the thickness of the first shell layer is 0.1 nm to 20 nm.

[0026] In some embodiments, the thickness of the second shell layer is 0.1 nm to 20 nm.

[0027] With the thicknesses of the first and second shells within the aforementioned range, not only can they provide a good transport channel for lithium ions, enabling them to quickly insert into and extract from the core of the lithium-rich manganese-based cathode material, but they can also effectively suppress the occurrence of side reactions between the lithium-rich manganese-based cathode material and the electrolyte, thereby improving the cycle life of the battery.

[0028] In some embodiments, the first solid electrolyte includes a first sulfide solid electrolyte.

[0029] The first sulfide solid electrolyte has high ionic conductivity and chemical stability, which can improve the ion conduction rate and stability of the composite cathode material, thus giving the battery a high charge and discharge rate and safety performance.

[0030] In some embodiments, the particle size of the first solid electrolyte is 1 nm-20 μm.

[0031] Within this particle size range, the contact area between the first solid electrolyte and the fluoride can be effectively increased, thereby allowing lithium ions to migrate more smoothly between the two and improving the lithium ion conduction efficiency inside the battery.

[0032] In some embodiments, the particle size of the composite cathode material is 10 nm-10 μm.

[0033] Within this particle size range, the composite cathode material has an appropriate ion diffusion path, allowing lithium ions to diffuse into and out of the composite cathode material more quickly during charging and discharging, thereby improving the battery's charge and discharge rate and rate performance.

[0034] In some embodiments, the above-mentioned positive electrode active layer further includes a second solid electrolyte, a conductive agent, and a binder. Based on the total mass of the positive electrode active layer, the content of the composite positive electrode material is 50%-99%, the content of the second solid electrolyte is 0.1%-49%, the content of the binder is 0.1%-5%, and the content of the conductive agent is 0.1%-5%.

[0035] The positive electrode has high ion and electron conductivity, which allows lithium ions to migrate smoothly within the positive electrode, thereby increasing the energy density of the battery. In addition, the presence of binder makes the positive electrode less likely to fall off or break during charging and discharging, thus improving the safety of the battery.

[0036] In some embodiments, the second solid electrolyte includes a second sulfide solid electrolyte.

[0037] The second sulfide solid electrolyte has high ionic conductivity and chemical stability, which can improve the ion conduction rate and stability of the positive electrode, thus giving the battery a high charge and discharge rate and safety performance.

[0038] In some embodiments, the particle size of the second solid electrolyte is 1 nm-20 μm.

[0039] Within this particle size range, the composite cathode material and the second solid electrolyte have a better contact effect, which helps to improve the ion conduction efficiency inside the cathode sheet, thereby improving the charge and discharge rate and rate performance of the battery.

[0040] Secondly, this application provides a method for preparing a battery cell, comprising the following steps:

[0041] Provides a core comprising a lithium-rich manganese-based cathode material;

[0042] The core, lithium salt, K source and fluorine source are mixed and then heat-treated to form a first shell containing fluoride on the surface of the core, thus obtaining an intermediate material; wherein the K source includes at least one of Al source, Ga source, Sc source, Zr source and B source;

[0043] The intermediate material is mixed with the first solid electrolyte to form a second shell by coating the first solid electrolyte on the outer surface of the first shell, so as to prepare a composite cathode material.

[0044] A positive electrode composite containing a composite positive electrode material is prepared, and the positive electrode composite is disposed on at least one surface of a positive electrode current collector to form a positive electrode active layer, so as to prepare a positive electrode sheet;

[0045] The positive electrode and the negative electrode are assembled to prepare a single battery cell.

[0046] The method for preparing a battery cell provided in this application first involves heat-treating the core and fluoride raw material components such as lithium source, K source and fluorine source, so that the formed fluoride coats the outer surface of the core. Then, the obtained material is mixed with a first solid electrolyte, so that the first solid electrolyte coats the outer surface of the first shell to form a second shell, thereby obtaining a single-core double-shell composite positive electrode material. The composite positive electrode material is then mixed with other components in the positive electrode active layer to obtain a positive electrode sheet. Finally, the positive electrode sheet and the negative electrode sheet are assembled, thereby effectively preparing a battery cell with the performance of the battery cell described above.

[0047] In some embodiments, after heat treatment of the mixture of the core, lithium salt, K source, and fluorine source, the following steps are further included:

[0048] The heat-treated mixture is mixed with a first solid electrolyte to coat the outer surface of the fluoride, thereby preparing a composite cathode material.

[0049] The heat-treated mixture is mixed with the first solid electrolyte, so that the first solid electrolyte can coat the outer surface of the fluoride to obtain a single-core double-shell composite cathode material, which effectively improves the ionic conductivity of the lithium-rich manganese-based cathode material.

[0050] In some embodiments, the fluorine source includes fluorine-containing inorganic materials; during the heat treatment process, the fluorine source removes oxygen atoms and lithium atoms from the surface portion of the lithium-rich manganese-based cathode material, thereby forming a first lithium-rich manganese-based cathode material with a layered structure and a second lithium-rich manganese-based cathode material with a spinel structure.

[0051] During the heat treatment process, lithium salt, K source and fluorine source react to form fluoride. Under the action of fluorine source, lithium atoms and oxygen atoms can be removed from the core surface, i.e. the surface of the lithium-rich manganese-based cathode material, thereby forming a first lithium-rich manganese-based cathode material with a layered structure and a second lithium-rich manganese-based cathode material with a spinel structure.

[0052] Thirdly, this application provides a composite cathode material, which includes a core, a first shell layer covering the outer surface of the core, and a second shell layer covering the outer surface of the first shell layer. The core includes a lithium-rich manganese-based cathode material, the first shell layer includes a fluoride, and the second shell layer includes a first solid electrolyte.

[0053] The composite cathode material exhibits a single-core, double-shell structure. On one hand, the first and second shells form a strong physical barrier, trapping oxygen generated by anion redox reactions in the lithium-rich manganese-based cathode material within the shells. This prevents oxygen from diffusing to other parts of the battery, reducing the negative impact of oxygen on battery performance. Furthermore, because oxygen is not easily released, the anion redox reaction can proceed under relatively stable conditions, improving its reversibility. During charging, sufficient oxygen participates in the redox reaction, allowing the lithium-rich manganese-based cathode material to store more energy. This enables the battery to maintain a high capacity over long-term use, extending its lifespan. On the other hand, fluorides possess high stability and chemical inertness; therefore, the fluoride-containing first shell effectively isolates the lithium-rich manganese-based cathode material. The contact between manganese-based cathode materials and the external environment can suppress side reactions between lithium-rich manganese-based cathode materials and other components such as electrolytes. This significantly reduces the risk of structural damage and performance degradation of composite cathode materials caused by side reactions, which plays a significant positive role in improving the cycle life of batteries. On the other hand, both fluoride and the first solid electrolyte have good ionic conductivity, so the two work together to form a stable and continuous ion conduction network. This double-shell structure makes the transport of lithium ions between different material interfaces smoother, which can significantly improve the transport kinetics of lithium ions in lithium-rich manganese-based cathode materials, and increase the speed and efficiency of lithium ion transport. In this way, lithium ions can be transported smoothly in composite cathode materials, thereby reducing structural changes and side reactions of composite cathode materials. This can reduce the capacity decay of batteries during cycling, thereby extending the cycle life of batteries.

[0054] In some embodiments, the lithium-rich manganese-based cathode material includes a first lithium-rich manganese-based cathode material and a second lithium-rich manganese-based cathode material, wherein the first lithium-rich manganese-based cathode material has a layered structure and the second lithium-rich manganese-based cathode material has a spinel structure.

[0055] The first lithium-rich manganese-based cathode material with a layered structure has a high capacity, while the second lithium-rich manganese-based cathode material with a spinel structure does not undergo anionic redox reactions. This means that the second lithium-rich manganese-based cathode material does not release oxygen during charging and discharging, and is not prone to capacity decay. The combination of these two factors gives the lithium-rich manganese-based cathode material not only a high capacity, but also significantly improves the cycle life of the battery when used in batteries.

[0056] In some embodiments, the core includes a core and a transition layer covering the core, wherein the core is formed of a first lithium-rich manganese-based cathode material and the transition layer is formed of a second lithium-rich manganese-based cathode material.

[0057] The second lithium-rich manganese-based cathode material has good ion diffusion capability and does not release oxygen during charging and discharging. Thus, the second lithium-rich manganese-based cathode material is coated on the outer surface of the first lithium-rich manganese-based cathode material, which can further suppress oxygen release, reduce the risk of capacity decay, and improve the cycle capacity of the battery.

[0058] Fourthly, this application provides a battery device including multiple battery cells from the above embodiments.

[0059] Fifthly, this application provides an energy storage device, including multiple battery cells or multiple battery devices according to the above embodiments, wherein the battery cells or battery devices are used to store or provide electrical energy.

[0060] Sixthly, this application provides an electrical device, including a battery cell, a battery device, or an energy storage device as described in the above embodiments, wherein the battery cell or battery device is used to store or provide electrical energy. Attached Figure Description

[0061] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0062] Figure 1 This is a schematic diagram of the structure of the cathode material provided in the embodiments of this application;

[0063] Figure 2 This is an exploded view of the battery device provided in the embodiments of this application;

[0064] Figure 3 This is an exploded view of a single battery cell provided in an embodiment of this application;

[0065] Figure 4 This is a schematic diagram of one embodiment of an electrical device that uses a battery cell as a power source, as described in the present application.

[0066] The following are the labeling elements in the figure:

[0067] 40. Positive electrode materials;

[0068] 41. Kernel; 411. Core; 412. Transition layer;

[0069] 42. Shell, 421. First shell, 422. Second shell;

[0070] 100. Battery device;

[0071] 10. Box body; 11. First box body; 12. Second box body;

[0072] 20. Battery cell modules;

[0073] 30. Battery cell, 31. Casing, 32. Electrode assembly, 33. Cover plate. Detailed Implementation

[0074] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0075] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0076] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0077] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0078] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0079] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0080] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0081] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0082] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0083] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0084] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0085] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0086] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0087] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0088] Lithium-rich manganese-based cathode materials are promising next-generation cathode materials for lithium-ion batteries due to their high specific capacity (>280 mAh / g), energy density (>1000 Wh / kg), low cost, and good thermal stability. Their application in lithium-ion batteries is expected to simultaneously improve both energy density and safety.

[0089] However, lithium-rich manganese cathode materials exhibit relatively low electronic and ionic conductivity, resulting in sluggish anion redox kinetics during charge and discharge. Furthermore, they are prone to side reactions with electrolytes such as sulfide electrolytes. This leads to low discharge capacity (<100 mAh / g) when applied to all-solid-state lithium-ion batteries, significantly lower than their theoretical capacity. In addition, the anion redox reaction in lithium-rich manganese cathode materials generates oxygen, which causes continuous capacity and voltage decay in lithium-ion batteries. This makes it difficult to achieve the required cycle life, thus hindering the practical application of lithium-rich manganese cathode materials in lithium-ion batteries.

[0090] Based on the above background, this application provides a battery cell that uses a core-shell structured composite cathode material. The shell composed of the first shell layer and the second shell layer can form a good physical barrier, which can bind the oxygen generated by the lithium-rich manganese-based cathode material inside the shell layer, preventing oxygen from diffusing to other parts of the battery. It can also suppress the occurrence of side reactions between the lithium-rich manganese-based cathode material and the electrolyte. This allows the battery to maintain a high capacity during long-term use, thereby extending the battery's service life.

[0091] In this application, the battery cell includes a solid-state battery cell, which includes a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode.

[0092] [Positive electrode plate]

[0093] The positive electrode includes a positive current collector and a positive active layer disposed on at least one side of the positive current collector. The positive active layer includes a composite positive electrode material. The positive electrode material includes a core, a first shell covering the outer surface of the core, and a second shell covering the outer surface of the first shell. The core includes a lithium-rich manganese-based positive electrode material. The first shell includes a fluoride. The second shell includes a first solid electrolyte.

[0094] Figure 1 This is a schematic diagram of the structure of a composite cathode material 40 as an example. The composite cathode material 40 includes a core 41 and a shell 42, with the shell 42 covering the outer surface of the core 41. In some embodiments, the surface of the core 41 is covered by the shell 42, which includes a first shell 421 and a second shell 422. The second shell 422 is disposed on the side of the first shell 421 away from the core 41. The first shell 421 includes a fluoride, and the second shell 422 includes a first solid electrolyte. For ease of distinction, the shell containing the fluoride is defined as the first shell 421, and the shell containing the first solid electrolyte is defined as the second shell 422.

[0095] Specifically, shell 42 includes at least two sub-shells, namely a first shell 421 and a second shell 422. The first shell 421 directly covers the outer surface of the core 41, and the second shell 422 is disposed outside the first shell 421, that is, the first shell 421 is disposed between the core 41 and the second shell 422. Here, the first shell 421 and the second shell 422 can be in direct contact or separated by a gap.

[0096] The composite cathode material has a core-shell structure, where the first shell containing fluoride and the second shell containing the first solid electrolyte form a good physical barrier. This traps the oxygen generated by the anion redox reaction of the lithium-rich manganese-based cathode material inside the shell, preventing oxygen from diffusing to other parts of the battery and thus reducing the negative impact of oxygen on battery performance. Moreover, because oxygen is not easily released, the anion redox reaction can proceed under relatively stable conditions, improving the reversibility of the redox reaction. As a result, during charging, there is sufficient oxygen in the composite cathode material to participate in the redox reaction, allowing the lithium-rich manganese-based cathode material to store more energy. This enables the battery to maintain a high capacity during long-term use and extends its lifespan.

[0097] Both the fluoride and the first solid electrolyte have good ionic conductivity, providing an efficient channel for lithium-ion transport in the composite cathode material. By coating the first solid electrolyte on the outer layer of the fluoride, the ion transport path is further optimized, and the ion conduction efficiency is improved, allowing lithium ions to migrate more quickly in the cathode, thereby improving the charge and discharge performance of the battery. Moreover, the first solid electrolyte can work synergistically with the fluoride to form a stable and continuous ion conduction network. This double-shell structure makes the transport of ions between different material interfaces smoother, reducing energy loss and charge transfer resistance caused by interface resistance, resulting in better cycle performance of the battery.

[0098] Both fluorides and the first solid electrolyte possess good ionic conductivity, thus improving the transport kinetics of lithium ions in lithium-rich manganese-based cathode materials. This means that lithium ions have a higher transport speed and efficiency, allowing them to be inserted and extracted more rapidly into the composite cathode material. This enables the battery to complete the charge and discharge process in a shorter time, contributing to improved charge and discharge capabilities. Simultaneously, the smoother transport of lithium ions within the composite cathode material reduces structural changes and side reactions. Good ion conduction helps reduce capacity and voltage decay of the cathode during cycling, thereby extending the battery's cycle life.

[0099] Solid-state batteries use solid electrolytes instead of liquid electrolytes, which improves battery safety and energy density. However, lithium-rich manganese-based cathode materials are prone to side reactions with solid electrolytes such as sulfide solid electrolytes, resulting in lower discharge capacity when used in sulfide solid-state batteries. Furthermore, because the electrolyte in solid-state batteries is non-liquid, the ion conductivity between the cathode and the solid electrolyte is slightly insufficient.

[0100] Based on this, the embodiments of this application employ a single-core, double-shell composite cathode material, with fluoride placed between the core and the first solid electrolyte. Fluoride possesses high stability, chemical inertness, and a wide electrochemical window, which significantly suppresses side reactions between the lithium-rich manganese-based cathode material and the electrolyte, thereby improving the structural stability of the composite cathode material. This significantly reduces the risk of structural damage and performance degradation of the composite cathode material due to side reactions. Furthermore, the good interfacial compatibility between the first shell and the core, and between the second shell and the first shell, reduces interfacial resistance and polarization, which plays a significant positive role in improving the battery's initial coulombic efficiency, charge-discharge efficiency, and cycle life. Simultaneously, the presence of the first solid electrolyte improves the contact between the cathode electrode and the solid electrolyte layer contained in the battery, allowing lithium ions to migrate more smoothly between the cathode electrode and the solid electrolyte layer.

[0101] The aforementioned "positive active layer disposed on at least one side of the positive current collector" means that the positive active layer can be disposed on one surface of the positive current collector along its own thickness direction, or it can be disposed on two surfaces of the positive current collector along its own thickness direction.

[0102] This application does not impose any particular limitation on the positive electrode current collector, as long as it can achieve the purpose of this application. In some embodiments, the positive electrode current collector may be a conductive carbon sheet, a metal foil, a carbon-coated metal foil, a porous metal plate, or a composite current collector. The conductive carbon material of the conductive carbon sheet may be one or more of Super P, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers. The metal materials of the metal foil, carbon-coated metal foil, and porous metal plate are each independently selected from at least one of copper, aluminum, nickel, and stainless steel. The composite current collector may be a composite current collector formed by combining a metal foil with a polymer base film.

[0103] In some embodiments, the fluoride includes lithium-containing fluorides.

[0104] Lithium-containing fluorides exhibit high operating voltage and good cycle stability, making the structure of the composite cathode material less prone to damage during charge and discharge, which helps improve the battery's cycle performance. Simultaneously, lithium-containing fluorides possess good ionic conductivity, thereby enhancing the ion conduction capacity of the composite cathode material and reducing interfacial resistance, thus improving the battery's charge-discharge capacity and cycle life.

[0105] In some embodiments, the fluoride includes at least one of Li3AlF6, Li3GaF6, Li3ScF6, Li2ZrF6, and LiBF4.

[0106] These fluorides have a high voltage window and chemical stability, making them less likely to react with lithium-rich manganese-based cathode materials, as well as with the first solid electrolyte and other components in the battery. This allows for the construction of a stable interface layer between the core and the fluoride, and between the fluoride and the first solid electrolyte, reducing interface resistance and polarization, and improving the battery's charge / discharge efficiency and cycle life.

[0107] In some embodiments, the mass percentage of fluoride is 0.1%-5% based on the total mass of the core described above. For example, the mass percentage of fluoride can be typical but not limiting values ​​such as 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%.

[0108] Controlling the mass percentage of fluoride within the aforementioned range can, on the one hand, fully leverage its ion-conducting advantages and effectively improve the ion conduction efficiency of lithium-rich manganese-based cathode materials; on the other hand, it allows for the construction of a uniform and stable first shell layer on the core surface, effectively isolating the lithium-rich manganese-based cathode material from the first solid electrolyte and the external environment, reducing the occurrence of side reactions. Furthermore, the fluoride-containing shell layer can prevent oxygen release, thereby improving battery safety and cycle performance.

[0109] In some embodiments, the lithium-rich manganese-based cathode material includes a first lithium-rich manganese-based cathode material and a second lithium-rich manganese-based cathode material, wherein the first lithium-rich manganese-based cathode material has a layered structure and the second lithium-rich manganese-based cathode material has a spinel structure.

[0110] The first lithium-rich manganese-based cathode material with a layered structure has a high capacity and can provide high energy storage for the battery. The second lithium-rich manganese-based cathode material with a spinel structure does not undergo anion redox reactions, which means that the second lithium-rich manganese-based cathode material does not release oxygen during charging and discharging, and is not prone to capacity decay. The combination of these two gives the battery high capacity and cycle life.

[0111] In some embodiments, the core includes a core and a transition layer covering the core, wherein the core is formed of a first lithium-rich manganese-based cathode material and the transition layer is formed of a second lithium-rich manganese-based cathode material.

[0112] Please see Figure 1 In some embodiments, a shell 42 covers the outer surface of a core 41, and the core 41 includes a core 411 and a transition layer 412 covering the outer surface of the core 411. For ease of distinction, the core containing a first lithium-rich manganese-based cathode material with a layered structure is defined as the core 411, and the core containing a second lithium-rich manganese-based cathode material with a spinel structure is defined as the transition layer 412. The core 41 includes the core 411. In some embodiments, the core 41 may only include the core 411, while in other embodiments, the core 41 may also include other sub-cores.

[0113] Please see Figure 1 In some embodiments, the core 41 further includes a transition layer 412, which is disposed on the outer side of the core 411, i.e., between the core 411 and the shell 42. In some embodiments, the transition layer 412 may be bonded in situ to the outer surface layer of the core 411.

[0114] The first lithium-rich manganese-based cathode material and the second lithium-rich manganese-based cathode material exhibit good compatibility. Their excellent interfacial contact reduces interfacial resistance and polarization, thereby improving the battery's charge-discharge efficiency and cycle stability. Simultaneously, the second lithium-rich manganese-based cathode material possesses superior ion diffusion capabilities and is less prone to oxygen release during charge-discharge. Therefore, by coating the first lithium-rich manganese-based cathode material with the second lithium-rich manganese-based cathode material, the battery's cycle capacity is further reduced, improving lithium-ion transport performance and suppressing oxygen release.

[0115] In some embodiments, the thickness of the transition layer is 0.1 nm to 10 nm. For example, the thickness of the transition layer can be a typical but non-limiting value such as 0.1 nm, 0.5 nm, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, etc.

[0116] Within this range, the ion transport differences between the first lithium-rich manganese-based cathode material and the second lithium-rich manganese-based cathode material can be balanced, achieving good synergy between the two structural materials, thereby optimizing the ion transport performance of the cathode material. At the same time, the transition layer can build a certain physical barrier for the core, which can bind the oxygen generated by the anion redox of the first lithium-rich manganese-based cathode material inside the core, preventing oxygen from escaping, reducing the release of oxygen in the core, thereby avoiding battery capacity decay and improving battery cycle life.

[0117] In some embodiments, the chemical formula of the first lithium-rich manganese-based cathode material is xLi2MnO3·(1-x)LiMO2, wherein M includes at least one of Ni, Co, Mn, Cr, Fe, Al, Nb, Zr, Mo, and Ta, and 0≤x≤1.

[0118] These first lithium-rich manganese-based cathode materials have a high voltage plateau, good thermal stability, and high specific capacity and safety, thus providing a significant positive effect on improving the energy density and safety of batteries.

[0119] In some embodiments, the chemical formula of the second lithium-rich manganese-based cathode material is LiN. y Mn z O4, where y+z=2, and N includes at least one of Ni, Co, Cr, Fe, Al, Nb, Zr, Mo, and Ta.

[0120] These second lithium-rich manganese-based cathode materials have high ion diffusion capabilities and do not release oxygen during charging and discharging, thereby improving battery safety.

[0121] In some embodiments, the mass percentage of the first solid electrolyte is 0.1%-5% based on the total mass of the core described above. For example, the mass percentage of the first solid electrolyte can be typical but not limiting values ​​such as 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%.

[0122] By controlling the mass percentage of the first solid electrolyte within the aforementioned range, its ion conduction advantages can be fully utilized without significantly increasing the overall mass of the composite cathode material. This allows for the construction of a continuous ion conduction network around the core, enabling lithium ions to migrate more rapidly within the cathode sheet and improving the battery's charge-discharge performance and rate performance. Furthermore, within this range, a stable second shell can be constructed on the core surface, preventing the escape of oxygen generated by the anion redox reaction in the lithium-rich manganese-based cathode material, thereby reducing the negative impact of oxygen on battery performance.

[0123] In some embodiments, the thickness of the first shell layer is 0.1 nm to 20 nm. For example, the thickness of the first shell layer can be a typical but non-limiting value such as 0.1 nm, 0.5 nm, 1 nm, 3 nm, 5 nm, 8 nm, 10 nm, 12 nm, 15 nm, 18 nm, 20 nm, etc.

[0124] Within the aforementioned thickness range, the first shell layer provides less obstruction to lithium-ion diffusion, allowing lithium-ions to pass through it more quickly. It also promotes good interfacial contact between the core and the first shell layer, and between the first shell layer and the second shell layer, reducing interfacial resistance and improving charge transfer efficiency. This helps improve the battery's charge and discharge performance.

[0125] In some embodiments, the thickness of the second shell layer is 0.1 nm to 20 nm. For example, the thickness of the second shell layer can be typical but not limiting values ​​such as 0.1 nm, 0.5 nm, 1 nm, 3 nm, 5 nm, 8 nm, 10 nm, 12 nm, 15 nm, 18 nm, and 20 nm.

[0126] Within the aforementioned thickness range, the second shell provides better mechanical protection for the core, preventing oxygen generated during charging from easily escaping. This allows the battery to maintain high capacity over long-term use, thereby improving cycle performance. Furthermore, a suitable thickness range reduces the path length and resistance for lithium-ion transport, enabling faster lithium-ion migration and thus improving charge / discharge rates and rate performance.

[0127] In some embodiments, the first solid electrolyte includes a first sulfide solid electrolyte.

[0128] The first sulfide solid electrolyte has high ionic conductivity and chemical stability, which can improve the ion conduction rate and stability of the cathode material, thus giving the battery a high charge and discharge rate and safety performance.

[0129] In some embodiments, the particle size of the first solid electrolyte is 1 nm to 20 μm. For example, the particle size of the first solid electrolyte can be typical but not limiting values ​​such as 1 nm, 5 nm, 10 nm, 50 nm, 100 nm, 500 nm, 1 μm, 5 μm, 10 μm, 15 μm, and 20 μm.

[0130] Within this particle size range, the contact area between the first solid electrolyte and the fluoride can be effectively increased, thereby allowing lithium ions to migrate more smoothly between the two and improving the lithium ion conduction efficiency inside the battery.

[0131] In some embodiments, the particle size of the first solid electrolyte is 50 nm to 1 μm. For example, the particle size of the first solid electrolyte can be typical but not limiting values ​​such as 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, and 1 μm.

[0132] Within this range, sufficient contact between the first solid electrolyte and the fluoride can be effectively promoted, thereby maximizing the contact area between the two. This not only promotes the transport of ions between the first solid electrolyte and the fluoride, enabling lithium ions to migrate more quickly from the composite cathode material and improving the battery's charge and discharge capacity, but also reduces the internal resistance of the cathode sheet, thereby reducing energy loss and increasing the battery's discharge capacity.

[0133] In some embodiments, the particle size of the composite cathode material is 10 nm to 10 μm. Exemplarily, the particle size of the composite cathode material can be typical but not limiting values ​​such as 10 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, and 10 μm.

[0134] In some embodiments, the particle size of the composite cathode material is 100 nm to 5 μm. For example, the particle size of the composite cathode material can be typical but not limiting values ​​such as 100 nm, 150 nm, 250 nm, 350 nm, 450 nm, 550 nm, 650 nm, 750 nm, 850 nm, 950 nm, 1 μm, 1.5 μm, 2.5 μm, 3.5 μm, 4.5 μm, and 5 μm.

[0135] Within this particle size range, the composite cathode material has an appropriate ion diffusion path, allowing lithium ions to diffuse into and out of the composite cathode material more quickly during charging and discharging, thereby improving the battery's charge and discharge rate and rate performance.

[0136] In some embodiments, the composite cathode material can be a single-crystal cathode material, which has good crystal structure integrity, thus improving its ionic conductivity and reducing structural damage and capacity decay during charge and discharge, thereby improving the battery's cycle performance. The composite cathode material can also be a polycrystalline cathode material, which has a higher specific capacity, thus improving the battery's energy density. Of course, the composite cathode material can also include both single-crystal and polycrystalline cathode materials.

[0137] In some embodiments, the above-mentioned positive electrode active layer further includes a second solid electrolyte, a conductive agent, and a binder. Based on the total mass of the positive electrode active layer, the content of the composite positive electrode material is 50%-99%, the content of the second solid electrolyte is 0.1%-49%, the content of the binder is 0.1%-5%, and the content of the conductive agent is 0.1%-5%.

[0138] For example, the content of the composite cathode material can be typical but not limiting values ​​such as 50%, 60%, 70%, 80%, 90%, 95%, 99%.

[0139] For example, the content of the second solid electrolyte can be typical but not limiting values ​​such as 0.1%, 1%, 5%, 10%, 20%, 30%, 40%, 49%.

[0140] For example, the content of the adhesive can be typical but not limiting values ​​such as 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%.

[0141] As an example, the adhesive may be a commonly used adhesive in the art, including but not limited to at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, hydrogenated nitrile rubber, styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS), and fluorinated acrylate resins.

[0142] For example, the content of the conductive agent can be typical but not limiting values ​​such as 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%.

[0143] As an example, the conductive agent can be a conductive material commonly used in the art, including but not limited to at least one of graphite, carbon nanotubes, nanofibers, carbon black, and graphene. Specifically, the conductive agent may include at least one of SP, KS-6, acetylene black, branched Ketjen black ECP, SFG-6, vapor-grown carbon fibers (VGCF), carbon nanotubes (CNTs), and graphene and their composite conductive agents.

[0144] In some embodiments, the above-mentioned positive electrode active layer further includes a second solid electrolyte, a conductive agent, and a binder. Based on the total mass of the positive electrode active layer, the content of the positive electrode material in the positive electrode active layer is 69%-94%, the content of the second solid electrolyte is 5%-30%, the content of the binder is 0.1%-5%, and the content of the conductive agent is 0.1%-5%.

[0145] For example, the content of the positive electrode material in the positive electrode active layer can be typical but not limiting values ​​such as 69%, 75%, 78%, 82%, 85%, 88%, 90%, and 94%.

[0146] For example, the content of the second solid electrolyte can be typical but not limiting values ​​such as 5%, 8%, 15%, 18%, 25%, 28%, 30%.

[0147] By controlling the content of each component within the above range, the positive electrode sheet is endowed with high ion conductivity and electronic conductivity, allowing lithium ions to migrate smoothly within the positive electrode sheet, thereby improving the energy density of the battery. Furthermore, the presence of the binder prevents the positive electrode sheet from detaching or breaking during charging and discharging, thus improving battery safety.

[0148] In some embodiments, the second solid electrolyte includes a second sulfide solid electrolyte.

[0149] The second sulfide solid electrolyte has high ionic conductivity and chemical stability, which can improve the ion conduction rate and stability of the positive electrode, thus giving the battery a high charge and discharge rate and safety performance.

[0150] In some embodiments, the particle size of the second solid electrolyte is 1 nm to 20 μm. For example, the particle size of the second solid electrolyte can be typical but not limiting values ​​such as 1 nm, 5 nm, 10 nm, 50 nm, 100 nm, 500 nm, 1 μm, 5 μm, 10 μm, 15 μm, and 20 μm.

[0151] The particle size of the second solid electrolyte is within this range, which allows for better contact between the composite cathode material and the second solid electrolyte. This helps to improve the ion conduction efficiency inside the cathode sheet, thereby improving the charge and discharge rate and rate performance of the battery.

[0152] In some embodiments, the particle size of the second solid electrolyte is 50 nm - 1 μm. Exemplarily, the particle size of the second solid electrolyte can be typical but non-limiting values such as 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 μm, etc.

[0153] The particle size of the second solid electrolyte is within this range, so as to increase its contact sites with the composite cathode material, achieve close contact between the second solid electrolyte and the composite cathode material, and be more conducive to improving the ion and electron transport efficiency at the interface between the two. In addition, the good contact effect between the two can reduce the interface resistance and improve the charge-discharge efficiency and rate performance of the battery.

[0154] In some embodiments, the battery cell includes, in addition to the positive electrode sheet, a negative electrode sheet and a solid electrolyte layer disposed between the positive electrode sheet and the negative electrode sheet. During the charge and discharge process of the battery, active ions are embedded and extracted back and forth between the positive electrode sheet and the negative electrode sheet. The solid electrolyte layer plays a role in conducting ions and preventing short circuit between the positive and negative electrodes between the positive electrode sheet and the negative electrode sheet.

[0155] [Negative electrode sheet]

[0156] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material, and the negative electrode active material is coated on the negative electrode current collector. The negative electrode current collector of the negative electrode sheet can use at least one of pure lithium, lithium alloy, and lithium metal composite oxide. The lithium alloy can include any one or more of aluminum (Al), magnesium (Mg), potassium (K), sodium (Na), calcium (Ca), strontium (Sr), barium (Ba), silicon (Si), germanium (Ge), antimony (Sb), lead (Pb), indium (In), and zinc (Zn). The lithium metal composite oxide can include a composite of lithium and an oxide (MeO x ) of any one metal (Me) selected from silicon (Si), tin (Sn), zinc (Zn), magnesium (Mg), cadmium (Cd), cerium (Ce), nickel (Ni), tungsten (W), and iron (Fe). For example, the lithium metal composite oxide can be Li x Fe2O3 (0 < x ≤ 1) or Li x WO2 (0 < x ≤ 1).

[0157] In some embodiments, the negative electrode current collector can have a protective layer. The protective layer can include any material as long as the material has lithium ion conductivity, does not interfere with the operation of the battery, and does not react with lithium. For example, a ceramic protective layer, a lithiated polyacrylic acid protective layer, etc. can be provided. The negative electrode current collector of the embodiments of the present application can use any protective layer as long as the protective layer improves the safety of the negative electrode current collector.

[0158] In addition, pure lithium or pure lithium alloy can be used as the negative electrode current collector in the embodiments of this application, or the negative electrode active material can be coated onto the negative electrode current collector and dried for use.

[0159] In some embodiments, the negative electrode sheet may only include a negative current collector and not a negative active material.

[0160] In some embodiments, the negative electrode sheet can be a metal sheet, such as a lithium sheet or a lithium alloy sheet, or it can be prepared by a dry method, such as by pressing the negative electrode active material, or by a wet method.

[0161] In the battery cell of this application embodiment, the negative electrode current collector can be formed to have a thickness of 2 μm to 1000 μm. In order to increase the bonding force between the negative electrode current collector and the negative electrode active material or solid electrolyte, a micro-sized uneven structure can be formed on the surface of the negative electrode current collector, and the negative electrode current collector can be constructed in any of various forms (e.g., film, sheet, foil, mesh, porous body, foam body or non-woven body).

[0162] The aforementioned negative electrode active materials can be carbon (e.g., non-graphitized carbon or graphitic carbon), lithium metal, lithium alloys, silicon alloys, tin alloys, conductive polymers (e.g., polyacetylene), metal oxides (e.g., SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, or Bi2O5), or metal composite oxides (e.g., Li). x Fe2O3 (0≤x≤1), Li x WO2(0≤x≤1)).

[0163] [Solid electrolyte layer]

[0164] The solid electrolyte layer is formed by a third solid electrolyte.

[0165] The third solid electrolyte may include at least one of the following: third sulfide solid electrolyte, oxide electrolyte, and organic solid electrolyte.

[0166] In some embodiments, the first sulfide solid electrolyte, the second sulfide solid electrolyte, and the third sulfide solid electrolyte each independently include at least one of silver-germanium sulfide type electrolyte, lithium-germanium-phosphorus-sulfide electrolyte, and lithium-phosphorus pentasulfide complex electrolyte.

[0167] In some embodiments, the chemical formula of the argentite-germanium ore type electrolyte is Li 6±s P 1-j A j S 5±s-t B tX 1±s , where 0 ≤ j < 1, 0 ≤ t < 1, 0 ≤ s < 1, A includes at least one of Ge, Si, Sn, and Sb, B includes at least one of O, Se, and Te, and X includes at least one of Cl, Br, I, and F.

[0168] These argyrodite-type electrolytes have good electron transport ability and chemical stability, and have good compatibility with other materials such as composite cathode materials, which is beneficial to improving the overall electrochemical performance of the battery.

[0169] In some embodiments, the chemical formula of the lithium germanium phosphorus sulfur-based electrolyte is Li 10±δ5 Ge 1-g G g P 2-q Q q S 12-w W w , where 0 ≤ δ5 < 1, 0 ≤ g ≤ 1, 0 ≤ q ≤ 2, 0 ≤ w < 1, G includes at least one of Si and Sn, Q includes Sb, and W includes at least one of O, Se, Te, Cl, Br, I, and F.

[0170] These lithium germanium phosphorus sulfur-based electrolytes have high ionic conductivity and a wide electrochemical window, and have good compatibility with electrode materials, which is beneficial to improving the comprehensive electrochemical performance of the battery.

[0171] In some embodiments, the chemical formula of the lithium sulfide phosphorus pentasulfide composite electrolyte is (100 - u - v)Li2S·uP2S5·vR m T n , where 0 < u < 100, 0 ≤ v < 100, 0 ≤ u + v < 100, 0 ≤ m < 4, 0 ≤ n < 6, R includes at least one of Li, B, Ge, Si, Sn, and Sb, and T includes at least one of S, Se, Te, O, Cl, Br, I, and F.

[0172] These lithium sulfide phosphorus pentasulfide composite electrolytes have good structural stability, high ionic conductivity, and good compatibility with electrode materials, which has an obvious positive effect on the cycle performance and charge-discharge ability of the battery.

[0173] In some embodiments, the oxide electrolyte includes at least one of perovskite solid electrolyte, sodium superionic conductor solid electrolyte (NASICON), lithium superionic conductor solid electrolyte (LISICON), and lithium lanthanum zirconium oxide solid electrolyte (LLZO).

[0174] In some embodiments, the organic solid electrolyte contains polyethylene oxide (PEO).

[0175] In some embodiments, the thickness of the solid electrolyte layer can be selected differently depending on the properties of the desired battery cell. In one embodiment, the thickness of the solid electrolyte layer can be 0.1 μm-1000 μm; in another embodiment, the thickness of the solid electrolyte layer can be 1 μm-500 μm; in yet another embodiment, the thickness of the solid electrolyte layer can be 20 μm-30 μm; this application does not limit this.

[0176] The second aspect of this application provides a method for preparing a battery cell, comprising the following steps:

[0177] Step S10: Provide a core, which includes a lithium-rich manganese-based cathode material;

[0178] Step S20: After mixing the core, lithium salt, K source and fluorine source, heat treatment is performed to form a first shell containing fluoride on the surface of the core to obtain an intermediate material, wherein the K source includes at least one of Al source, Ga source, Sc source, Zr source and B source.

[0179] Step S30: Mix the intermediate material with the first solid electrolyte to form a second shell by coating the first solid electrolyte on the outer surface of the first shell, so as to prepare a composite cathode material.

[0180] Step S40: Prepare a positive electrode composite containing composite positive electrode material, and place the positive electrode composite on at least one surface of the positive electrode current collector to form a positive electrode active layer, so as to prepare a positive electrode sheet;

[0181] Step S50: Assemble the positive electrode and the negative electrode to prepare a single battery cell;

[0182] The method for preparing a battery cell provided in this application first involves heat-treating the core and fluoride raw material components such as lithium source, K source and fluorine source, so that the formed fluoride coats the outer surface of the core. Then, the obtained material is mixed with a first solid electrolyte, so that the first solid electrolyte coats the outer surface of the first shell to form a second shell, thereby obtaining a single-core double-shell composite positive electrode material. The composite positive electrode material is then mixed with other components in the positive electrode active layer to obtain a positive electrode sheet. Finally, the positive electrode sheet and the negative electrode sheet are assembled, thereby effectively preparing a battery cell with the performance of the battery cell described above.

[0183] In some embodiments, in step S10, the lithium-rich manganese-based cathode material includes a first lithium-rich manganese-based cathode material. The selection of the first lithium-rich manganese-based cathode material is as described above and will not be repeated here.

[0184] In some embodiments, in step S20, lithium salt, K source and fluorine source are used to form fluoride.

[0185] Lithium salts include lithium-soluble salts, such as nitrates.

[0186] K sources include soluble salts corresponding to the element K, such as nitrates. For example, Al sources include aluminum nitrate (Al(NO3)3). K sources also include acids corresponding to the element K, such as boric acid, which is a B source.

[0187] The fluorine source includes fluorine-containing inorganic substances, including but not limited to ammonium fluoride (NH4F). For example, the concentration of ammonium fluoride can be 0.5-0.8 mol / L.

[0188] In some embodiments, the specific process of mixing the core, lithium salt, K source and fluorine source and then performing heat treatment in step S20 to form a first shell containing fluoride on the surface of the core is as follows:

[0189] Based on the mass ratio of fluoride and the stoichiometric ratio of fluoride formation, the core, lithium salt, and K source are mixed for 25-35 minutes. Then, the fluoride source is added to the mixture, and the mixture is treated at 75℃-85℃ for 4-6 hours. Subsequently, the reaction powder is collected by centrifugation and drying. Finally, the collected reaction powder is heat-treated at 400℃-500℃ for 4-6 hours to form a first shell containing fluoride on the surface of the core.

[0190] In the above process, lithium salt, K source and fluorine source react to form fluoride, and under the action of fluorine source, lithium atoms and oxygen atoms can be removed from the core surface, that is, the surface of the first lithium-rich manganese-based cathode material, thereby forming a second lithium-rich manganese-based cathode material with spinel structure in situ on the surface of the first lithium-rich manganese-based cathode material.

[0191] In some embodiments, the specific steps of mixing the intermediate material with the first solid electrolyte in step S30, so that the first solid electrolyte coats the outer surface of the first shell to form a second shell, are as follows:

[0192] The intermediate material and the first solid electrolyte are mixed and treated at a speed of 3000 rpm-3500 rpm for 1 h-1.5 h, so that the first solid electrolyte is coated on the outer surface of the fluoride to prepare the cathode material.

[0193] For example, the mixing process can be carried out using a mechanical blending machine.

[0194] The heat-treated mixture is mixed with the first solid electrolyte, so that the first solid electrolyte can coat the outer surface of the fluoride to obtain a single-core double-shell cathode material, which effectively improves the ionic conductivity of the lithium-rich manganese-based cathode material.

[0195] In some embodiments, the specific process of preparing a positive electrode composite containing a composite positive electrode material and depositing the positive electrode composite on at least one surface of the positive electrode current collector to form a positive electrode active layer in step S40 is as follows:

[0196] The composite positive electrode material, the second solid electrolyte, the conductive agent, and the binder are mixed in a certain mass ratio. The uniformly mixed powder is then heated and kneaded into a lumpy material in an internal mixer. The mixture is then hot-rolled at 70℃-90℃ to form a self-supporting sheet (positive electrode active layer). Finally, the self-supporting sheet is combined with the positive electrode current collector hot roller to obtain the positive electrode sheet.

[0197] The quality of the composite cathode material, the second solid electrolyte, the conductive agent, and the binder are as described above and will not be repeated here.

[0198] As an example, the mixing process can be carried out using a dual planetary mixer.

[0199] In some embodiments, the specific process of assembling the positive electrode and the negative electrode in step S50 is as follows:

[0200] The third solid electrolyte is placed in the battery mold and pressurized to obtain an electrolyte sheet. Then, the positive electrode is placed on one side of the electrolyte sheet and the negative electrode is placed on the other side of the electrolyte sheet, that is, in the order of "positive electrode - electrolyte sheet - negative electrode". The battery is then pressurized at 500MPa for 5 minutes to assemble a single battery cell.

[0201] Thirdly, this application provides a composite cathode material, which includes a core, a first shell layer covering the outer surface of the core, and a second shell layer covering the outer surface of the first shell layer. The core includes a lithium-rich manganese-based cathode material, the first shell layer includes a fluoride, and the second shell layer includes a first solid electrolyte.

[0202] The composite cathode material exhibits a core-shell structure, specifically a single-core, double-shell structure. On one hand, the first and second shell layers form a strong physical barrier, confining the oxygen generated by anion redox reactions in the lithium-rich manganese-based cathode material within the shell, preventing oxygen diffusion to other parts of the battery and thus reducing the negative impact of oxygen on battery performance. Furthermore, because oxygen is not easily released, the anion redox reaction can proceed under relatively stable conditions, improving the reversibility of the redox reaction. This ensures sufficient oxygen participation in the redox reaction during charging, allowing the lithium-rich manganese-based cathode material to store more energy. This enables the battery to maintain a high capacity over long-term use, extending its lifespan. On the other hand, fluorides possess high stability and chemical inertness; therefore, the fluoride-containing shell effectively isolates the lithium-rich manganese-based cathode material from the external environment. The contact between the fluoride and the first solid electrolyte effectively suppresses side reactions between the lithium-rich manganese-based cathode material and other components such as the electrolyte. This significantly reduces the risk of structural damage and performance degradation of the composite cathode material caused by side reactions, which plays a significant positive role in improving the cycle life of the battery. Furthermore, both the fluoride and the first solid electrolyte have good ionic conductivity, so they work together to form a stable and continuous ion conduction network. This double-shell structure makes the transport of lithium ions between different material interfaces smoother, which can significantly improve the transport kinetics of lithium ions in the lithium-rich manganese-based cathode material, increase the speed and efficiency of lithium ion transport, and reduce energy loss caused by interface resistance. In this way, lithium ions can be transported smoothly in the composite cathode material, thereby reducing structural changes and side reactions in the composite cathode material. This can reduce the capacity decay of the battery during cycling, thereby extending the cycle life of the battery.

[0203] In some embodiments, the lithium-rich manganese-based cathode material includes a first lithium-rich manganese-based cathode material and a second lithium-rich manganese-based cathode material, wherein the first lithium-rich manganese-based cathode material has a layered structure and the second lithium-rich manganese-based cathode material has a spinel structure.

[0204] The first lithium-rich manganese-based cathode material with a layered structure has a high capacity, while the second lithium-rich manganese-based cathode material with a spinel structure does not undergo anionic redox reactions. This means that the second lithium-rich manganese-based cathode material does not release oxygen during charging and discharging, and is not prone to capacity decay. The combination of these two factors gives the lithium-rich manganese-based cathode material not only a high capacity, but also significantly improves the cycle life of the battery when used in batteries.

[0205] In some embodiments, the core includes a core and a transition layer covering the core, wherein the core is formed of a first lithium-rich manganese-based cathode material and the transition layer is formed of a second lithium-rich manganese-based cathode material.

[0206] The second lithium-rich manganese-based cathode material has good ion diffusion capability and does not release oxygen during charging and discharging. Thus, the second lithium-rich manganese-based cathode material is coated on the outer surface of the first lithium-rich manganese-based cathode material, which can further suppress oxygen release, reduce the risk of capacity decay, and improve the cycle capacity of the battery.

[0207] A fourth aspect of this application provides a battery device comprising a plurality of battery cells described in the above embodiments.

[0208] The battery device mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells, which are connected in series, parallel, or mixed connections via a busbar.

[0209] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0210] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0211] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cell assemblies housed within the housing.

[0212] As an example, the battery cell assembly can be a battery module, and the battery cell assembly can be housed in the housing by fixing the battery module in the housing.

[0213] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0214] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0215] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0216] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0217] The fifth aspect of this application provides an energy storage device, including a plurality of battery cells or a plurality of battery devices as described above, wherein the battery cells or battery devices are used to store or provide electrical energy.

[0218] In some embodiments, the energy storage device includes one or more battery clusters to increase the voltage and capacity of the energy storage device. A battery cluster may include multiple battery units connected in series via a busbar to increase the voltage of the energy storage device. When the energy storage device includes multiple battery clusters, the battery clusters are connected in parallel to increase the capacity of the energy storage device.

[0219] Energy storage devices can be used in energy storage power stations, wind power generation systems, solar power generation systems, mobile power systems, or temporary power supply systems. Energy storage devices can store electrical energy as needed and output it when appropriate. For example, an energy storage device can store electrical energy during off-peak hours and provide power to relevant users or electrical equipment during peak hours. The energy storage system provided in this application embodiment can be any power system that requires energy storage devices.

[0220] In some embodiments, the energy storage device is an energy storage container or an energy storage cabinet.

[0221] In some embodiments, the energy storage device may include a cabinet and one or more battery clusters housed within the cabinet.

[0222] In some embodiments, the energy storage device may include modules such as a thermal management module, a main control module, a central control module, a power distribution module, and a fire protection module.

[0223] As an example, the thermal management module may include a liquid cooling unit that supplies coolant to each battery device via piping to regulate the temperature of the individual battery cells.

[0224] As an example, the main control module can serve as the battery management unit for the battery cluster, used to monitor and manage the battery cluster. The main control module can monitor information such as the current, voltage, power, or temperature of the battery cluster. For instance, it can control the charging and discharging current and voltage of the battery cluster. The main control module includes modules such as an auxiliary battery management unit (SBMU) and a fusion switch.

[0225] As an example, the central control module can serve as the battery management unit for an energy storage device, used to monitor and manage the device. The central control module can monitor information such as the energy storage device's current, voltage, power, state of charge, or temperature. For instance, it can control the charging and discharging current and voltage of the energy storage device. As an example, the central control module includes modules such as an Insulation Monitoring Module (IMM), a Master Battery Management Unit (MBMU), an Ethernet (ETH) module, and a fiber optic conversion module.

[0226] As an example, the fire protection module includes a control panel, detectors, alarm devices, etc., used to detect, alarm, or extinguish fires in the energy storage system.

[0227] As an example, a power distribution module can be used to distribute power to modules in an energy storage device that require electricity.

[0228] The sixth aspect of this application provides an electrical device, including a battery cell or a battery device as described in the above embodiments, wherein the battery cell or battery device is used to store or provide electrical energy.

[0229] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use individual battery cells, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships, and spacecraft. For example, spacecraft include airplanes, rockets, space shuttles, and spacecraft.

[0230] The following description, with appropriate reference to the accompanying drawings, describes the battery cell, battery device, and power consumption device provided in the embodiments of this application.

[0231] Figure 2 This is an exploded view of a battery device 100 as an example. The battery device 100 includes a housing 10 and battery cell assemblies 20, with the battery cell assemblies 20 housed within the housing 10. The housing 10 provides a space for housing the battery cell assemblies 20 and can have various structures. In some embodiments, the housing 10 may include a first housing 11 and a second housing 12, which overlap each other, collectively defining a closed space for housing the battery cell assemblies 20. Of course, the housing 10 formed by the first housing 11 and the second housing 12 can have various shapes, such as a cylinder, a cuboid, etc. Multiple battery cell assemblies 20 can be arranged in any manner within the battery housing.

[0232] In the battery device 100, there can be one or more battery cell components 20. Multiple battery cell components 20 can be connected in series, parallel, or in a mixed manner. A mixed connection means that multiple battery cell components 20 are connected in both series and parallel. Multiple battery cell components 20 can be directly connected in series, parallel, or in a mixed manner, and then the whole formed by multiple battery cell components 20 is housed in the housing 10. Of course, the battery device 100 can also be formed by first connecting multiple battery cell components 20 in series, parallel, or in a mixed manner to form a battery module, such as a battery module or battery pack. Multiple battery modules are then connected in series, parallel, or in a mixed manner to form a whole and housed in the housing 10.

[0233] Battery cell assembly 20 includes multiple battery cells 30. Figure 3 This is an exploded view of a single battery cell 30 as an example. The single battery cell 30 includes a housing 31, a cover plate 33, an electrode assembly 32, and other functional components.

[0234] The housing 31 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 31 is a hollow structure with an opening at one end, and the housing 31 is used to cooperate with the cover plate 33 to form an internal environment for accommodating the electrode assembly 32, electrolyte, and other functional components. The housing 31 can be of various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shape of the housing 31 can be determined according to the specific shape and size of the electrode assembly 32. The material of the housing 31 can be, but is not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and is not limited here. The cover plate 33 is a component that covers the opening of the housing 31 to isolate the internal environment of the battery cell 30 from the external environment. The material of the cover plate 33 can be, but is not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and is not limited here.

[0235] Figure 4 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0236] Example

[0237] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0238] Example 1

[0239] This embodiment provides a composite cathode material and a battery cell.

[0240] [Composite cathode material]

[0241] The composite cathode material includes a core, a first shell layer covering the outer surface of the core, and a second shell layer covering the outer surface of the first shell layer; the core includes a core material and a transition layer covering the outer surface of the core material, the core material including a first lithium-rich manganese-based cathode material (Li). 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2), the transition layer includes a second lithium-rich manganese-based cathode material (LiNi). 0.25 Co 0.25 Mn 1.5 The first shell includes a fluoride (Li3AlF6), and the second shell includes a first solid electrolyte (Li6PS5Cl). The thickness of the transition layer is X nm, the mass ratio of the fluoride to the core is 1 wt%, the thickness of the first shell is X nm, the mass ratio of the first solid electrolyte to the core is 3 wt%, and the thickness of the second shell is X nm.

[0242] The preparation process of the above composite cathode material is as follows:

[0243] Step 1: First, weigh 1 kg of lithium-rich manganese-based cathode material Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 was placed in a 3L reactor, and 2L of deionized water was added, with continuous stirring. Then, 10.92g of LiNO3 and 19.63g of Al(NO3)3·9H2O were added to the reactor according to the stoichiometric ratio, and stirring was continued for 0.5h. Subsequently, a 0.6mol / L NH4F solution was added to the reactor at a rate of 5ml / min using a peristaltic pump, and the resulting mixture was stirred in the reactor at 80℃ for 5h. After centrifugation, drying, and collection of the reaction powder, the collected powder was heat-treated at 500℃ for 5h to obtain a fluoride-coated lithium-rich manganese-based cathode material, i.e., the first shell layer is formed on the surface of the core.

[0244] Step 2: Add the above-mentioned fluoride-coated lithium-rich manganese-based cathode material and 30g of the first solid electrolyte (Li6PS5Cl) into a mechanical fusion machine and run it at 3000rpm for 1h to obtain the above-mentioned composite cathode material.

[0245] [Preparation of the positive electrode sheet]

[0246] The composite cathode material prepared in Example 1, the second solid electrolyte (Li6PS5Cl, D50 particle size of 700nm), the conductive agent VGCF, and the binder PTFE (polytetrafluoroethylene) were mixed in a mass ratio of 70:26:3:1 and mixed evenly in a double planetary mixer. Then, the evenly mixed powder was heated and kneaded into a lumpy material in an internal mixer, and then hot-rolled at 80°C to form a self-supporting sheet (positive electrode active layer). Finally, the self-supporting sheet was hot-rolled to combine with the current collector Al foil to obtain the positive electrode sheet.

[0247] [Preparation of the negative electrode sheet]

[0248] InLi alloy is used as the negative electrode.

[0249] [Third Solid Electrolyte]

[0250] Li6PS5Cl(LPSCl) sulfide electrolyte was used as the third solid electrolyte.

[0251] [Preparation of battery cells]

[0252] Weigh 100mg of the third solid electrolyte and add it to the battery mold. Pressurize to obtain an electrolyte sheet. Then place the positive electrode sheet on one side of the electrolyte sheet and the negative electrode sheet on the other side of the electrolyte sheet, i.e., arrange them in the order of "positive electrode sheet-electrolyte sheet-negative electrode sheet". Pressurize at 500MPa for 5min to assemble into a battery cell.

[0253] Examples 2-11

[0254] Examples 2-11 provide a composite cathode material and a battery cell, wherein the main difference between the battery cell and Example 1 is that the composite cathode material is different, specifically: at least one of the following is different: the type of fluoride, the content of fluoride, the type of first solid electrolyte, the content of first solid electrolyte, the thickness of the transition layer, the thickness of the first shell layer, and the thickness of the second shell layer, as detailed in Table 1.

[0255] Table 1

[0256]

[0257] In Table 1:

[0258] C represents the first lithium-rich manganese-based cathode material, C1 represents the material Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2;

[0259] D represents the second lithium-rich manganese-based cathode material, and D1 represents LiNi. 0.25 Co 0.25 Mn1.5 O4;

[0260] E represents fluoride, and W1 represents the mass ratio of fluoride to the core.

[0261] F represents the first solid electrolyte, and W2 represents the mass ratio of the first solid electrolyte to the core.

[0262] H1 represents the thickness of the transition layer; H2 represents the thickness of the first shell layer; H3 represents the thickness of the second shell layer.

[0263] Comparative Example 1

[0264] This comparative example provides a single battery cell, which differs from Example 1 in that the positive electrode material is only Li. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2.

[0265] Comparative Example 2

[0266] This comparative example provides a single battery cell, which differs from Example 1 in that: the shell is formed of Li2ZrO3, and the mass ratio of Li2ZrO3 to the core is 3wt%.

[0267] Performance testing

[0268] (1) Initial charge and discharge capacity

[0269] The testing process for the 0.1C initial charge / discharge capacity is as follows:

[0270] The battery cells were charged to 4.18V (4.8V for lithium) at a current density of 0.1C, allowed to stand for 10 minutes, and then discharged to 1.38V (2.0V for lithium) at a current density of 0.1C. The initial discharge capacity and initial charge capacity of the battery were obtained. The battery was tested at 25℃, where 1C = 200mA / g.

[0271] (2) First Coulomb efficiency

[0272] The initial Coulomb efficiency is calculated using the following formula:

[0273]

[0274] (3) Capacity retention rate after 200 cycles

[0275] The testing process for cycle performance is as follows:

[0276] The battery cells were first subjected to constant current charge-discharge for 3 cycles at a current density of 0.1C to obtain the initial discharge capacity and initial coulombic efficiency. Then, a long-cycle test was conducted at a current density of 0.33C for 200 cycles to calculate the battery's cycle capacity retention. The battery voltage test window was 2.0–4.8V vs. Li. + / Li, the battery was tested at 25°C, where 1C = 200mA / g.

[0277] The performance parameters of the battery cells provided in Examples 1-11 and Comparative Examples 1-2 are shown in Table 2.

[0278] Table 2

[0279]

[0280] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, characterized in that, The device includes a positive electrode sheet, which includes a positive current collector and a positive active layer disposed on at least one side of the positive current collector. The positive active layer includes a composite positive electrode material, which includes a core, a first shell layer covering the outer surface of the core, and a second shell layer covering the outer surface of the first shell layer. The core includes a lithium-rich manganese-based positive electrode material, the first shell layer includes a fluoride, and the second shell layer includes a first solid electrolyte.

2. The battery cell as described in claim 1, characterized in that, The fluorides include lithium-containing fluorides.

3. The battery cell as described in claim 1 or 2, characterized in that, The fluoride includes at least one of Li3AlF6, Li3GaF6, Li3ScF6, Li2ZrF6, and LiBF4.

4. The battery cell according to any one of claims 1 to 3, characterized in that, Based on the total mass of the core, the fluoride accounts for 0.1%-5% of the total mass.

5. The battery cell according to any one of claims 1 to 4, characterized in that, The lithium-rich manganese-based cathode material includes a first lithium-rich manganese-based cathode material and a second lithium-rich manganese-based cathode material. The first lithium-rich manganese-based cathode material has a layered structure, and the second lithium-rich manganese-based cathode material has a spinel structure.

6. The battery cell as described in claim 5, characterized in that, The core includes a core and a transition layer covering the core. The core is made of the first lithium-rich manganese-based cathode material, and the transition layer is made of the second lithium-rich manganese-based cathode material.

7. The battery cell as described in claim 6, characterized in that, The thickness of the transition layer is 0.1 nm to 10 nm.

8. The battery cell according to any one of claims 5 to 7, characterized in that, The first lithium-rich manganese-based cathode material has the chemical formula xLi2MnO3·(1-x)LiMO2, wherein M includes at least one of Ni, Co, Mn, Cr, Fe, Al, Nb, Zr, Mo, and Ta, and 0≤x≤1; and / or The chemical formula of the second lithium-rich manganese-based cathode material is LiN. y Mn z O4, where y+z=2, and N includes at least one of Ni, Co, Cr, Fe, Al, Nb, Zr, Mo, and Ta.

9. The battery cell according to any one of claims 1 to 8, characterized in that, Based on the total mass of the core, the mass percentage of the first solid electrolyte is 0.1%-5%.

10. The battery cell according to any one of claims 1 to 9, characterized in that, The thickness of the first shell layer is 0.1 nm-20 nm; and / or The thickness of the second shell is 0.1nm-20nm.

11. The battery cell according to any one of claims 1 to 10, characterized in that, The first solid electrolyte includes a first sulfide solid electrolyte; and / or The particle size of the first solid electrolyte is 1 nm-20 μm.

12. The battery cell according to any one of claims 1 to 11, characterized in that, The particle size of the composite cathode material is 10 nm-10 μm.

13. The battery cell according to any one of claims 1 to 12, characterized in that, The positive electrode active layer further includes a second solid electrolyte, a conductive agent, and a binder. Based on the total mass of the positive electrode active layer, the content of the composite positive electrode material is 50%-99%, the content of the second solid electrolyte is 0.1%-49%, the content of the binder is 0.1%-5%, and the content of the conductive agent is 0.1%-5%.

14. The battery cell as described in claim 13, characterized in that, The second solid electrolyte includes a second sulfide solid electrolyte; and / or The particle size of the second solid electrolyte is 1 nm-20 μm.

15. A method for preparing a single battery cell, characterized in that, Includes the following steps: A core is provided, the core comprising a lithium-rich manganese-based cathode material; The core, lithium salt, K source, and fluorine source are mixed and then heat-treated to form a first shell layer containing fluoride on the surface of the core, thereby obtaining an intermediate material; wherein the K source includes at least one of Al source, Ga source, Sc source, Zr source, and B source. The intermediate material is mixed with the first solid electrolyte, so that the first solid electrolyte coats the outer surface of the first shell to form a second shell, in order to prepare a composite cathode material. A positive electrode composite containing the composite positive electrode material is prepared, and the positive electrode composite is disposed on at least one surface of the positive electrode current collector to form a positive electrode active layer, so as to prepare a positive electrode sheet; The positive electrode and the negative electrode are assembled to prepare a single battery cell.

16. The method for preparing a single battery cell as described in claim 15, characterized in that, The fluorine source includes fluorine-containing inorganic materials; during the heat treatment process, the fluorine source removes oxygen atoms and lithium atoms from the surface portion of the lithium-rich manganese-based cathode material, thereby forming a first lithium-rich manganese-based cathode material with a layered structure and a second lithium-rich manganese-based cathode material with a spinel structure.

17. A composite cathode material, characterized in that, The composite cathode material includes a core, a first shell layer covering the outer surface of the core, and a second shell layer covering the outer surface of the first shell layer. The core includes a lithium-rich manganese-based cathode material, the first shell layer includes a fluoride, and the second shell layer includes a first solid electrolyte.

18. The composite cathode material as described in claim 17, characterized in that, The lithium-rich manganese-based cathode material includes a first lithium-rich manganese-based cathode material and a second lithium-rich manganese-based cathode material. The first lithium-rich manganese-based cathode material has a layered structure, and the second lithium-rich manganese-based cathode material has a spinel structure.

19. The composite cathode material as described in claim 18, characterized in that, The core includes a core and a transition layer covering the core. The core is made of the first lithium-rich manganese-based cathode material, and the transition layer is made of the second lithium-rich manganese-based cathode material.

20. A battery device, characterized in that, It includes multiple battery cells as described in any one of claims 1-14 or multiple battery cells prepared by the preparation method as described in any one of claims 15-16.

21. An energy storage device, characterized in that, It includes multiple battery cells as described in any one of claims 1-14, multiple battery cells prepared by the preparation method as described in any one of claims 15-16, or multiple battery devices as described in claim 20.

22. An electrical appliance, characterized in that, It includes the battery cell as described in any one of claims 1-14, the battery cell prepared by the preparation method as described in any one of claims 15-16, the battery device as described in claim 20, or the energy storage device as described in claim 21.

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