Battery cell, battery apparatus, electrical apparatus, composite positive electrode material and preparation method therefor

Abstract

A battery cell, a battery apparatus, an electrical apparatus, a composite positive electrode material and a preparation method therefor. The battery cell comprises a positive electrode sheet and a negative electrode sheet. The positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer stacked on at least one surface of the positive electrode current collector. The positive electrode active layer comprises a composite positive electrode material. The composite positive electrode material comprises a core and a coating layer coating the surface of the core. The core comprises a lithium-manganese-based positive electrode active material. The coating layer comprises a thiocyanate. The positive electrode of the battery cell uses the composite positive electrode material in which the lithium-manganese-based positive electrode active material is coated with the thiocyanate. On the basis of the effect of the thiocyanate, the capacity retention rate, specific capacity, and initial Coulombic efficiency of the battery cell can be improved.

Description

Battery cells, battery devices, electrical devices, composite cathode materials and their preparation methods

[0001] This application claims priority to Chinese Patent Application No. 202411697463.8, filed on November 25, 2024, with the Chinese Patent Office, entitled "Battery cell, battery device, power device, composite cathode material and preparation method thereof", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application belongs to the field of battery technology, specifically relating to a battery cell, battery device, power-consuming device, composite cathode material and its preparation method. Background Technology

[0003] With the booming development of new energy vehicles, battery drive systems have become an important factor affecting the performance and cost of new energy vehicles. Due to their high energy density, low memory effect, and high operating voltage, batteries have become the preferred power source for battery drive systems.

[0004] Lithium-manganese-based cathode active materials are mainly composed of elements such as lithium, manganese, and oxygen. Compared with traditional lithium cobalt oxide and ternary materials, lithium-manganese-based cathode active materials have higher energy density and lower cost, making them a promising next-generation cathode material for lithium-ion batteries. However, their application in lithium-ion batteries presents challenges. On the one hand, the anion redox process of lithium-manganese-based cathode active materials is prone to oxygen release, and on the other hand, side reactions can easily occur on the surface of the lithium-manganese-based cathode active material, leading to battery degradation and affecting battery performance. Summary of the Invention

[0005] The purpose of this application is to provide a battery cell, a battery device, an electrical device, a composite cathode material and its preparation method, aiming to solve the technical problem of how to reduce oxygen release from lithium manganese-based cathode active materials in order to improve the cycle charge and discharge performance of batteries.

[0006] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:

[0007] In a first aspect, embodiments of this application provide a battery cell including a positive electrode and a negative electrode. The positive electrode includes a positive current collector and a positive active layer stacked on at least one surface of the positive current collector. The positive active layer contains a composite positive electrode material, which includes a core and a coating layer covering the surface of the core. The core includes a lithium manganese-based positive active material, and the coating layer includes a thiocyanate.

[0008] By using a composite cathode material in the battery cell that coats lithium manganese-based cathode active material with thiocyanate, the anion redox activity of the lithium manganese-based cathode active material is activated during the charging and discharging of the battery cell, and the lattice oxygen O 2- It is easily oxidized to peroxide ions (O2). 2- The thiocyanate ions (SCN) in the thiocyanate coating on the surface - It can form a redox pair, which couples with the redox anions of lithium manganese-based cathode active materials, enabling O2 to... 2- The oxygen is promptly reduced to lattice oxygen, thereby reducing the risk of oxygen release from the lithium manganese-based cathode active material. This process makes the battery cells less prone to degradation and can improve the capacity retention rate of the battery cells. At the same time, the thiocyanate coating on the surface of the lithium manganese-based cathode active material can reduce the risk of side reactions on the surface of the lithium manganese-based cathode active material. Therefore, this unique composite cathode material can not only improve the battery capacity retention rate, but also further improve the battery specific capacity and initial coulombic efficiency.

[0009] In some embodiments, the thiocyanate includes at least one of alkali metal thiocyanates, alkaline earth metal thiocyanates, and transition metal thiocyanates.

[0010] The above-mentioned types of thiocyanates, when coated on the surface of lithium manganese-based cathode active materials, can not only significantly improve the charge and discharge performance of the battery, but these thiocyanates are also widely available and easy to obtain.

[0011] In some embodiments, the alkali metal thiocyanate includes at least one of NaSCN, KSCN, and RbSCN;

[0012] Alternatively, the alkaline earth metal thiocyanate includes at least one of Mg(SCN)2, Ca(SCN)2 and Sr(SCN)2;

[0013] Alternatively, the transition metal thiocyanate may include at least one of Fe(SCN)3 and Cu(SCN)2.

[0014] The aforementioned thiocyanate is coated on the surface of the lithium manganese-based cathode active material. The metal atoms of the thiocyanate in the coating layer can be incorporated into the lattice of the lithium manganese-based cathode active material through the annealing process, thereby improving the structural stability and ion diffusion performance of the lithium manganese-based cathode active material.

[0015] In some embodiments, the mass ratio of the thiocyanate to the lithium manganese-based positive electrode active material is (0.1-10):100;

[0016] And / or, the thickness of the coating layer is 0.1 nm-50 nm.

[0017] Coating the lithium manganese-based cathode active material with thiocyanate at a mass ratio of 0.1 to 10:100 can significantly improve the performance of the lithium manganese-based cathode active material, thereby enhancing the electrochemical performance of the battery. The coating thickness ranges from 0.1 nm to 50 nm, forming a composite cathode material with a stable core-shell structure.

[0018] In some embodiments, the general chemical formula of the lithium manganese-based positive electrode active material is xLi2MnO3·(1-x)LiMO2; wherein M includes at least one of Ni, Co, Mn, Cr, Fe, Al, Nb, Zr, Mo, Ta, and Ru, and 0 < x < 1.

[0019] The lithium-manganese-based cathode active material of the above chemical formula, as a lithium-rich manganese cathode material, not only has the characteristics of high specific capacity and high energy density, but also low cost, good thermal stability, and better cycle performance.

[0020] In some embodiments, the battery cell includes a solid-state battery cell, and a solid electrolyte layer is disposed between the positive electrode and the negative electrode.

[0021] Lithium-manganese-based cathode active materials, when used in solid-state battery cells, can achieve higher energy density, more stable charge and discharge, and better cycle life and safety performance.

[0022] In some embodiments, the positive electrode active layer contains a solid electrolyte, and both the solid electrolyte and the electrolyte in the solid electrolyte layer are sulfide electrolytes.

[0023] Sulfide electrolytes have the advantages of high ionic conductivity and good thermal stability, but they are prone to side reactions with lithium manganese-based cathode active materials. However, the lithium manganese-based cathode active material of the battery cell in this application is coated with thiocyanate, which can reduce the risk of side reactions between the two. Therefore, the battery cell of this application makes comprehensive use of the advantages of both, and can better improve the charge and discharge performance of solid-state battery cells containing lithium manganese-based cathode active materials and sulfide electrolytes.

[0024] In some embodiments, the particle size D of the solid electrolyte is... V 50 is less than 1μm.

[0025] By adding solid electrolytes with the above-mentioned particle size to the positive electrode active layer, the solid electrolytes and composite positive electrode materials can be better contacted and mixed, thereby improving the overall ionic conductivity of the positive electrode.

[0026] In some embodiments, the positive electrode active layer further contains a conductive agent and a binder, and the mass ratio of the composite positive electrode material, the solid electrolyte, the conductive agent and the binder is (50-99):(0.1-50):(0.1-5):(0.1-5).

[0027] The positive electrode active material layer formed according to the above mass ratio can not only form a good ion-conducting network in the positive electrode active layer of the positive electrode sheet, but also has good stability and is not easy to fall off.

[0028] Secondly, embodiments of this application provide a battery device, including the battery cell provided in the first aspect of embodiments of this application.

[0029] By employing the battery cells provided in the embodiments of this application, such a battery device has excellent charge and discharge performance.

[0030] Thirdly, embodiments of this application provide an electrical device, including a battery cell provided in the first aspect of embodiments of this application or a battery device provided in the second aspect of embodiments of this application, wherein the battery cell or the battery device is used to store or provide electrical energy.

[0031] By employing the battery cells or battery devices provided in the embodiments of this application, the electrical devices have good charging and discharging performance and can operate better.

[0032] Fourthly, embodiments of this application provide a composite cathode material, the composite cathode material comprising a core and a coating layer covering the surface of the core, the core comprising a lithium manganese-based cathode active material, and the coating layer comprising thiocyanate.

[0033] Thiocyanate is coated onto the surface of a lithium-manganese-based cathode active material to form a core-shell composite cathode material. Based on the redox action of thiocyanate, it can couple with the anions of the lithium-manganese-based cathode active material, thereby reducing the risk of oxygen release from the lithium-manganese-based cathode active material. Simultaneously, the thiocyanate coating on the surface of the lithium-manganese-based cathode active material can reduce surface side reactions and improve electronic conductivity. Therefore, this unique composite cathode material, when used in lithium-ion batteries, can improve battery capacity retention, specific capacity, and initial coulombic efficiency.

[0034] In some embodiments, the thiocyanate includes at least one of alkali metal thiocyanates, alkaline earth metal thiocyanates, and transition metal thiocyanates.

[0035] The above-mentioned types of thiocyanates, when coated on the surface of lithium manganese-based cathode active materials, can not only significantly improve the charge and discharge performance of the battery, but these thiocyanates are also widely available and easy to obtain.

[0036] In some embodiments, the alkali metal thiocyanate includes at least one of NaSCN, KSCN, and RbSCN;

[0037] Alternatively, the alkaline earth metal thiocyanate includes at least one of Mg(SCN)2, Ca(SCN)2 and Sr(SCN)2;

[0038] Alternatively, the transition metal thiocyanate may include at least one of Fe(SCN)3 and Cu(SCN)2.

[0039] The aforementioned thiocyanate is coated on the surface of the lithium manganese-based cathode active material. The metal atoms of the thiocyanate in the coating layer can be incorporated into the lattice of the lithium manganese-based cathode active material through the annealing process, thereby improving the structural stability and ion diffusion performance of the lithium manganese-based cathode active material.

[0040] In some embodiments, the mass ratio of the thiocyanate to the lithium manganese-based positive electrode active material is (0.1-10):100;

[0041] And / or, the thickness of the coating layer is 0.1 nm-50 nm.

[0042] Coating lithium manganese-based cathode active materials with thiocyanate at a mass ratio of 0.1 to 10:100 can significantly improve their performance. The coating thickness ranges from 0.1 nm to 50 nm, forming a composite cathode material with a stable core-shell structure.

[0043] In some embodiments, the general chemical formula of the lithium manganese-based positive electrode active material is xLi2MnO3·(1-x)LiMO2; wherein M includes at least one of Ni, Co, Mn, Cr, Fe, Al, Nb, Zr, Mo, Ta, and Ru, and 0 < x < 1.

[0044] The lithium-manganese-based cathode active material of the above chemical formula, as a lithium-rich manganese cathode material, not only has the characteristics of high specific capacity and high energy density, but also low cost, good thermal stability, and better cycle performance.

[0045] Fifthly, embodiments of this application provide a method for preparing a composite cathode material, comprising:

[0046] Provides lithium manganese-based cathode active materials and thiocyanates;

[0047] The thiocyanate is coated onto the surface of the lithium manganese-based cathode active material to form a coating layer, thereby obtaining a composite cathode material.

[0048] By coating the surface of lithium manganese-based cathode active material with thiocyanates of the above-mentioned general chemical structure to form a coating layer, a composite cathode material with a core-shell structure is formed. This preparation method is not only simple and easy to prepare on a large scale, but the resulting composite cathode material can also significantly improve the electrochemical performance of lithium manganese-based cathode active material.

[0049] In some embodiments, the step of coating the thiocyanate onto the surface of the lithium manganese-based cathode active material to form a coating layer includes:

[0050] The thiocyanate and the lithium manganese-based positive electrode active material are dry-mixed and then heat-treated at 280–320°C in an oxygen atmosphere.

[0051] The above-mentioned dry heat treatment coating process can efficiently coat thiocyanate onto the surface of lithium manganese-based cathode active material to form a stable core-shell structure composite cathode material.

[0052] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0053] 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:

[0054] Figure 1 is a schematic diagram of the structure of a single battery cell according to an embodiment of this application;

[0055] Figure 2 is an exploded view of the battery cell shown in Figure 1;

[0056] Figure 3 is a schematic diagram of one embodiment of the battery module of this application;

[0057] Figure 4 is a schematic diagram of one embodiment of the battery pack of this application;

[0058] Figure 5 is an exploded view of the battery pack shown in Figure 4.

[0059] Figure 6 is a schematic diagram of one embodiment of an electrical device that uses a secondary battery as a power source, as described in the present application.

[0060] Explanation of reference numerals in the attached drawings: 10-cell battery; 11-casing; 12-top cover assembly; 13-electrode assembly; 20-battery module; 30-battery pack; 31-upper casing; 32-lower casing. Detailed Implementation

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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). "At least one" refers to one or more (including one, two, three, etc.).

[0067] 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.

[0068] 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.

[0069] With the dwindling availability of traditional energy resources, the development of new energy storage devices is receiving increasing attention. Among these, secondary batteries are not only used in energy storage systems for hydropower, thermal power, wind power, and solar power plants, but are also widely applied in electric vehicles such as electric bicycles, electric motorcycles, and electric cars. As the application areas of secondary batteries as power batteries continue to expand, the market demand is also constantly increasing, while the performance requirements for these batteries are becoming increasingly stringent.

[0070] Taking lithium-ion batteries (LIBs) as an example, they include positive electrode plates, negative electrode plates, and electrolytes. The positive electrode plate uses lithium-ion positive electrode active materials. Lithium-manganese-based positive electrode active materials, as a new generation of positive electrode active materials for lithium-ion batteries, have higher energy density and lower cost compared to traditional lithium cobalt oxide and ternary materials. However, when applied to lithium-ion batteries, the anion redox process easily causes oxygen release problems. Specifically, when lithium-manganese-based positive electrode active materials are charged to high voltage, anion redox is activated, releasing lattice oxygen (O). 2- It is oxidized to peroxide ions O2 2- During long-term cycling, it is easy to release oxygen. Moreover, the surface of lithium manganese-based cathode active materials is prone to side reactions. For example, the oxygen released by lithium manganese-based cathode active materials may oxidize the electrolyte (such as sulfide electrolyte), causing a decrease in electrolyte conductivity. At the same time, it will also destroy the crystal structure of the lithium manganese-based cathode active material itself, resulting in a continuous increase in interfacial impedance and rapid capacity decay.

[0071] Currently, the commonly used oxide (such as Li3BO3, Li2ZrO3) coating strategy improves lithium manganese-based cathode active materials. Although it can reduce the surface side reactions of lithium manganese-based cathode active materials to a certain extent, it cannot solve the oxygen release problem of lithium manganese-based cathode active materials.

[0072] Therefore, based on the oxygen release mechanism of lithium manganese-based cathode active materials, this application seeks suitable redox pairs to promptly reduce peroxide ions generated during charging of lithium manganese-based cathode active materials to lattice oxygen, thereby better solving the oxygen release problem of lithium manganese-based cathode active materials. Based on this, embodiments of this application coat the surface of lithium manganese-based cathode active materials with thiocyanate, thereby forming a core-shell structured composite cathode material to improve the performance of lithium manganese-based cathode active materials, and provide battery cells and related devices using this composite cathode material. The specific technical solution is as follows.

[0073] [Composite cathode materials and their preparation methods]

[0074] The composite cathode material provided in this application embodiment has a core-shell structure. The composite cathode material in this application embodiment includes: (1) a core, including a lithium manganese-based cathode active material; and (2) a coating layer, which coats the surface of the core, and the material of the coating layer includes thiocyanate.

[0075] Thiocyanates are compounds that include thiocyanate ions (SCN). - The compound is based on the coating of thiocyanate, through which a redox pair (SCN) is formed. - / (SCN)3 - The function of O2 is to couple with the anion redox reaction of lithium manganese-based cathode active material, thereby enabling O2 to... 2- The oxygen is promptly reduced to lattice oxygen, thus mitigating the risk of oxygen release from lithium manganese-based cathode active materials. Simultaneously, the coating layer reduces the risk of surface side reactions on lithium manganese-based cathode active materials and improves electronic conductivity.

[0076] In some embodiments, thiocyanates are compounds formed from metal ions and thiocyanate ions. Specifically, thiocyanates include at least one of alkali metal thiocyanates, alkaline earth metal thiocyanates, and transition metal thiocyanates. Coating the surface of lithium manganese-based cathode active materials with these types of thiocyanates not only significantly improves the charge-discharge performance of the battery, but these thiocyanates are also widely available and readily accessible.

[0077] In some embodiments, the alkali metal thiocyanate includes at least one of NaSCN, KSCN, and RbSCN; the alkaline earth metal thiocyanate includes at least one of Mg(SCN)2, Ca(SCN)2, and Sr(SCN)2; and the transition metal thiocyanate includes at least one of Fe(SCN)3 and Cu(SCN)2. The above-mentioned thiocyanates are coated on the surface of the lithium manganese-based cathode active material. The metal atoms of the thiocyanate in the coating layer can be incorporated into the lattice of the lithium manganese-based cathode active material through an annealing process, thereby improving the structural stability and ion diffusion performance of the lithium manganese-based cathode active material.

[0078] In some embodiments, the mass ratio of thiocyanate to lithium manganese-based cathode active material is (0.1–10):100. Exemplarily, in the composite cathode material, the mass ratio of thiocyanate to lithium manganese-based cathode active material can be 0.1:100, 0.5:100, 1:100, 2:100, 5:100, 6:100, 8:100, etc., for example, a mass ratio of thiocyanate to lithium manganese-based cathode active material of 0.1–5:100. Coating with thiocyanate according to the above mass ratio can effectively improve the performance of the lithium manganese-based cathode active material.

[0079] In some embodiments, the coating thickness of the composite cathode material is 0.1 nm to 50 nm. For example, the coating thickness formed by thiocyanate in the composite cathode material can be 0.1 nm, 0.5 nm, 1 nm, 2 nm, 5 nm, 10 nm, 20 nm, 25 nm, 30 nm, 40 nm, 50 nm, etc. For instance, the coating thickness on the core surface can be 1 nm to 10 nm. A lithium manganese-based cathode active material with a coating layer within the above thickness range can form a composite cathode material with a stable core-shell structure.

[0080] In some embodiments, the core of the composite cathode material contains a lithium manganese-based cathode active material with the general chemical formula xLi₂MnO₃·(1-x)LiMO₂; wherein M includes at least one of Ni, Co, Mn, Cr, Fe, Al, Nb, Zr, Mo, Ta, and Ru, and 0 < x < 1. The lithium manganese-based cathode active material with the above general chemical formula, as a lithium-rich manganese cathode material, not only possesses high specific capacity and high energy density, but also exhibits low cost, good thermal stability, and better cycle performance.

[0081] This application also provides a method for preparing a composite cathode material. Specifically, the preparation method of this application prepares the above-mentioned composite cathode material, and the steps include:

[0082] S01: Provides lithium manganese-based cathode active materials and thiocyanates;

[0083] S02: Thiocyanate is coated onto the surface of lithium manganese-based cathode active material to form a coating layer, thus obtaining a composite cathode material.

[0084] By coating the surface of lithium manganese-based cathode active material with thiocyanates of the above-mentioned general chemical structure to form a coating layer, a composite cathode material with a core-shell structure is formed. This preparation method is not only simple and easy to prepare on a large scale, but the resulting composite cathode material can also significantly improve the electrochemical performance of lithium manganese-based cathode active material.

[0085] In step S01, the specific types and proportions of lithium manganese-based positive electrode active materials and thiocyanates are described above.

[0086] In step S02, the step of coating the lithium manganese-based cathode active material with thiocyanate to form a coating layer includes: dry mixing the thiocyanate and the lithium manganese-based cathode active material, followed by heat treatment at 280–320°C in an oxygen atmosphere. This dry heat treatment coating process allows for the efficient coating of thiocyanate onto the surface of the lithium manganese-based cathode active material, forming a stable core-shell structured composite cathode material.

[0087] For example, the preparation method of the composite cathode material in this application includes: weighing thiocyanate and lithium manganese-based cathode active material powder in proportion, uniformly mixing them using a dry coating device, and then heat-treating the resulting uniformly mixed material at 280-320°C for 1-2 hours in an oxygen atmosphere to obtain the above-mentioned core-shell structured composite cathode material.

[0088] [Battery cell]

[0089] This application provides a battery cell. Specifically, it includes: (1) a positive electrode sheet, which includes a positive current collector and a positive active layer disposed on at least one surface of the positive current collector, that is, a positive active layer is disposed on one surface of the positive current collector or both opposite surfaces are disposed on a positive active layer. (2) a negative electrode sheet. Specifically, the positive active layer in the positive electrode sheet contains the composite positive electrode material of this application embodiment.

[0090] The positive electrode of the battery cell in this application embodiment uses a composite positive electrode material unique to this application embodiment. When the battery cell is charged to a high voltage, the lithium manganese-based positive electrode active material anion redox in the core of the composite positive electrode material is activated, and the lattice oxygen O 2- It is oxidized to peroxide ions O2 2- At this time, the O2 on the surface 2- It will be promptly reported by SCN - Timely reduction to lattice oxygen prevents the release of oxygen from the lithium-rich manganese surface. Meanwhile, SCN... - It is oxidized to (SCN)3 - During the discharge process, (SCN)3 -It can also be reduced to SCN - This process reduces the risk of oxygen release from the lithium manganese-based cathode active material during long-term cycling, making the battery cells less prone to degradation and improving their capacity retention. Simultaneously, the thiocyanate coating on the surface of the lithium manganese-based cathode active material reduces the risk of surface side reactions. Therefore, this unique composite cathode material not only improves battery capacity retention but also further enhances the battery's specific capacity and initial coulombic efficiency.

[0091] The composite cathode material in the cathode sheet includes a core and a coating layer covering the surface of the core. The core includes a lithium manganese-based cathode active material, and the coating layer includes thiocyanate.

[0092] The thiocyanates include at least one of alkali metal thiocyanates, alkaline earth metal thiocyanates, and transition metal thiocyanates. For example, alkali metal thiocyanates include at least one of NaSCN, KSCN, and RbSCN; alkaline earth metal thiocyanates include at least one of Mg(SCN)2, Ca(SCN)2, and Sr(SCN)2; and transition metal thiocyanates include at least one of Fe(SCN)3 and Cu(SCN)2.

[0093] In some embodiments, in the composite cathode material of the cathode sheet, the mass ratio of thiocyanate to lithium manganese-based cathode active material is (0.1–10):100; the thickness of the coating layer is 0.1 nm–50 nm. Such a composite cathode material enables the battery cell to have better electrochemical performance.

[0094] In some embodiments, the general chemical formula of the lithium manganese-based positive electrode active material is xLi2MnO3·(1-x)LiMO2; wherein M includes at least one of Ni, Co, Mn, Cr, Fe, Al, Nb, Zr, Mo, Ta, and Ru, and 0 < x < 1.

[0095] In some embodiments, the battery cell can be a liquid battery cell or a solid battery cell. To achieve higher energy density and more stable charging and discharging, the battery cells in this application embodiment include solid battery cells. In this solid battery cell, a solid electrolyte layer is disposed between the positive and negative electrode plates. The use of lithium-manganese-based positive electrode active materials in solid battery cells can achieve higher energy density, better cycle life, and improved safety performance.

[0096] In some embodiments, for a solid-state battery cell, the positive electrode active layer contains a solid electrolyte, and both the solid electrolyte and the electrolyte in the solid electrolyte layer are sulfide electrolytes. Sulfide electrolytes have the advantages of high ionic conductivity and good thermal stability, but they are prone to side reactions with lithium manganese-based positive electrode active materials. In contrast, the lithium manganese-based positive electrode active material of the battery cell of this application is coated with thiocyanate. Thiocyanate and sulfide electrolyte have good stability. Coating the surface of the lithium manganese-based positive electrode active material with thiocyanate can improve the interfacial stability between the lithium manganese-based positive electrode active material and the sulfide electrolyte, thereby reducing the risk of side reactions. Therefore, the battery cell of this application comprehensively utilizes the advantages of both, which can not only reduce the risk of oxygen release from the lithium manganese-based positive electrode active material, making its crystal structure less prone to damage, but also reduce the risk of sulfide electrolyte decomposition, thus better improving the charge and discharge performance of the solid-state battery cell containing lithium manganese-based positive electrode active material and sulfide electrolyte.

[0097] The solid electrolyte in the positive electrode active layer and the electrolyte in the solid electrolyte layer can be the same or different. For sulfide electrolytes, they can include one or more of the following: silver sulfide-germanium sulfide electrolytes, LGPS-type sulfide electrolytes, and lithium sulfide-phosphorus pentasulfide complex-type sulfide electrolytes.

[0098] Among them, the silver-germanium sulfide type electrolyte includes the chemical formula Li 6±s P 1-j A j S 5±s-t B t X 1±s Sulfide electrolytes, wherein 0≤j<1, 0≤t<1, 0≤s<1, A is selected from one or more elements from Ge, Si, Sn, and Sb, B is one or more elements from O, Se, and Te, and X is selected from one or more elements from Cl, Br, I, and F; LGPS type sulfide electrolytes include those with the chemical formula Li 10±δ5 Ge 1-g G g P 2-q Q q S 12-w W w The sulfide electrolytes, wherein 0≤δ5<1, 0≤g≤1, 0≤q≤2, 0≤w<1, G is selected from one or two elements from Si and Sn, Q is Sb, and W is selected from one or more elements from O, Se, Te, Cl, Br, I, and F; lithium sulfide pentaphosphine disulfide complex sulfide electrolytes include those with the chemical formula (100-uv)Li2S·uP2S5·vM m N nA sulfide electrolyte, where 0 < u < 100, 0 ≤ v < 100, 0 ≤ u + v < 100, 0 ≤ m < 4, 0 ≤ n < 6, M is selected from one or more elements of Li, B, Ge, Si, Sn, and Sb, and N is selected from one or more elements of S, Se, Te, O, Cl, Br, I, and F.

[0099] In some embodiments, the particle size D of the solid electrolyte in the positive electrode active layer V 50 is less than 1 μm. By adding the solid electrolyte with the above particle size to the positive electrode active layer, such a solid electrolyte and the composite positive electrode material can better contact and mix, thereby improving the overall ionic conductivity of the positive electrode.

[0100] And the particle size D of the solid electrolyte in the solid electrolyte layer V 50 can be 1 nm to 20 μm, for example, 50 nm to 1 μm.

[0101] The size of the particulate material is called the particle size. The percentage of particles in different particle size ranges in the total amount is called the particle size distribution, and the volume distribution particle size is the particle size calculated cumulatively in terms of particle volume. For example, Dv50 represents the average particle size corresponding to when the cumulative volume particle size distribution percentage in a sample reaches 50%. In specific embodiments, a particle size tester can be used to test the average particle size. For the particle size test of the embodiments of the present application: it can be measured in accordance with GB / T 19077-2016 "Laser Diffraction Method for Particle Size Distribution" using a Mastersizer 2000E type laser particle size analyzer from Malvern Instruments Limited, UK.

[0102] In some embodiments, the positive electrode active layer further contains a conductive agent and a binder, and the mass ratio of the composite positive electrode material, solid electrolyte, conductive agent, and binder is (50 to 99):(0.1 to 50):(0.1 to 5):(0.1 to 5). The positive electrode active material layer formed according to the above mass ratio can not only form a good ionic conduction network in the positive electrode active layer of the positive electrode sheet, but also has good stability of the positive electrode active layer and is not easily detached.

[0103] In some embodiments, the conductive agent in the positive electrode active layer 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, it can be selected from at least one of SP, KS-6, acetylene black, branched Ketjen black ECP, SFG-6, vapor-grown carbon fiber VGCF, carbon nanotubes CNTs, and graphene and their composite conductive agents. The binder can be a binder commonly used in the art, selected from at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene-propylene terpolymer, ethylene-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.

[0104] In some embodiments, the positive current collector may be a metal foil, a foamed metal, or a composite current collector. For example, as a metal foil, silver-treated aluminum or stainless steel, stainless steel, copper, aluminum, nickel, carbon electrodes, carbon, nickel, or titanium, etc., may be used. The foamed metal may be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. The composite current collector may include a polymeric material base layer and a metal layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymeric material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0105] In some embodiments, the negative electrode sheet may be a metal battery cell containing only a negative current collector, i.e., the corresponding battery cell is a metal battery cell without a negative electrode active material such as silicon carbide. Alternatively, the negative electrode sheet may include a negative current collector and a negative electrode active layer disposed on at least one surface of the negative current collector. As an example, the negative current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material is disposed on either or both of the two opposite surfaces of the negative current collector.

[0106] The negative electrode current collector can be a metal foil, a foamed metal, or a composite current collector. For example, the metal foil can be silver-treated aluminum or stainless steel, stainless steel, copper, aluminum, nickel, carbon electrodes, carbon, nickel, or titanium, etc. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloys, or foamed carbon, etc. The composite current collector can include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.). In some embodiments, the positive electrode current collector can be made of aluminum foil, and the negative electrode current collector can be made of copper foil.

[0107] The negative electrode active layer contains a negative electrode active material. As an example, the negative electrode active material can be a negative electrode active material known in the art for use in battery cells. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as battery negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0108] The negative electrode active layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). The negative electrode active layer may also optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the negative electrode active layer may also optionally include other additives, such as dispersants, thickeners (e.g., sodium carboxymethyl cellulose), etc.

[0109] In this embodiment, the battery cell can be a rechargeable battery cell, which refers to a battery cell that can be recharged after discharge to activate the active materials and continue to be used. The battery cell can be a lithium-ion battery cell.

[0110] In this embodiment, the battery cell may include a battery casing and an electrode assembly encapsulated within the battery casing. The shape of the battery cell is not particularly limited; it may be cylindrical, square, or any other arbitrary shape. Figure 1 shows a square-structured battery cell 10.

[0111] In some embodiments, as shown in FIG2, the outer packaging of the battery cell 10 may include a housing 11 and a top cover assembly 12. The housing 11 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and the side plates enclosing a receiving cavity. The housing 11 has an opening communicating with the receiving cavity, and the top cover assembly 12 is used to cover the opening to close the receiving cavity.

[0112] The preparation method of the battery cell 10 is well known. For liquid battery cells, the positive electrode, separator, and negative electrode contained in the battery cell of this application embodiment can be formed into an electrode assembly 13 by a winding process. The electrode assembly 13 is encapsulated in a receiving cavity. The electrolyte is immersed in the electrode assembly 13. The number of electrode assemblies 13 contained in the battery cell 10 can be one or more, which can be adjusted according to actual needs. In some embodiments, the positive electrode, separator, negative electrode, and electrolyte can be assembled to form the battery cell 10. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly 13 by a winding process, the electrode assembly 13 is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, standing, formation, shaping, and other processes, the battery cell 10 is obtained.

[0113] The method for preparing the battery cell 10 is well known. For solid-state battery cells, the positive electrode, solid electrolyte layer, and negative electrode are directly assembled into an all-solid-state battery cell.

[0114] [Battery Device]

[0115] This application provides a battery device. The battery device includes the battery cell described above. By employing the battery cell provided in this application, the battery device exhibits excellent cycle performance, specific capacity, and initial coulombic efficiency, enabling it to perform charge and discharge efficiently.

[0116] The battery apparatus 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 connected in series, parallel, or mixed connections via a busbar.

[0117] In some embodiments, the battery device of this application may include any one of a battery cell, a battery module, or a battery pack.

[0118] A battery module is assembled from a single battery cell, meaning it can contain multiple single battery cells. The specific number can be adjusted according to the application and capacity of the battery module.

[0119] In some embodiments, FIG3 is a schematic diagram of a battery module 20 as an example. In the battery module 20, a plurality of battery cells 10 may be arranged sequentially along the length direction of the battery module 20. Of course, they can also be arranged in any other manner. Furthermore, the plurality of battery cells 10 can be fixed by fasteners.

[0120] Optionally, the battery module 20 may also include a housing with a receiving space in which multiple battery cells 10 are received.

[0121] A battery pack refers to an assembly of the aforementioned battery cells 10, meaning it can contain multiple battery cells 10. These multiple battery cells 10 can be assembled into the aforementioned battery module 20. The specific number of battery cells 10 or battery modules 20 contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0122] As shown in the embodiment, Figures 4 and 5 are schematic diagrams of a battery pack 30 as an example. The battery pack 30 may include a battery compartment and multiple battery modules 20 disposed within the battery compartment. The battery compartment includes an upper compartment 31 and a lower compartment 32, the upper compartment 31 covering the lower compartment 32 and forming a closed space for accommodating the battery modules 20. The multiple battery modules 20 can be arranged in any manner within the battery compartment.

[0123] Electrical appliances

[0124] This application provides an electrical device. The electrical device includes a single battery cell or a battery device provided in this application, which is used to store or provide electrical energy. Based on the use of the single battery cell or battery device provided in this application, the electrical device can operate more effectively.

[0125] Electrical devices can be, but are not limited to, mobile devices (such as mobile phones, portable devices, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, electric vehicles, electric toys, power tools, etc.), electric trains, ships, satellites and spacecraft, energy storage systems, etc. The type of electrical device can be selected from individual battery cells, battery modules, or battery packs according to its usage requirements.

[0126] Figure 6 is a schematic diagram of an example electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0127] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use rechargeable batteries as their power source.

[0128] Example

[0129] 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.

[0130] Example 1

[0131] battery cell

[0132] 1) Positive electrode plate

[0133] Lithium manganese-based cathode active material Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 and sodium thiocyanate powder were mixed in a dry coating apparatus at a mass ratio of 100:1. The resulting mixture was then heat-treated at 300°C for 1 hour in an oxygen atmosphere to obtain sodium thiocyanate-coated Li. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 composite cathode material.

[0134] The composite cathode material obtained above was weighed with sulfide electrolyte Li6PS5Cl (Dv50 of 700nm), conductive agent VGCF, and binder PTFE in a mass ratio of 70:26:3:1. The mixture was then mixed in a double planetary mixer. The mixed powder was then heated and kneaded into a lumpy material in an internal mixer. The mixture was then hot-rolled at 80°C to form a self-supporting positive electrode active layer. Finally, it was hot-rolled with current collector aluminum foil to obtain the positive electrode sheet.

[0135] 2) Negative electrode plate

[0136] InLi alloy anode is used.

[0137] 3) Solid electrolyte layer

[0138] The material is a sulfide electrolyte, Li6PS5Cl.

[0139] 4) Assembly

[0140] First, 100 mg of the sulfide electrolyte Li6PS5Cl was weighed and added to a solid-state battery mold. Pressure was applied to obtain an electrolyte sheet (i.e., a solid electrolyte layer). Then, a positive electrode was placed on one side of the electrolyte sheet, and a negative electrode was added to the other side. The mixture was then pressurized at 500 MPa for 5 minutes to assemble a single all-solid-state battery cell. The battery testing window was 2.0–4.8 V vs Li, and the testing temperature was 25 °C.

[0141] Examples 2-8

[0142] See Table 1 for the differences from Example 1.

[0143] Comparative Example 1

[0144] The difference from Example 1 is that the lithium manganese-based positive electrode active material in the positive electrode sheet does not have a coating layer on its surface; otherwise, it is the same as Example 1.

[0145] Comparative Example 2

[0146] The difference from Example 1 is that the surface coating material of the lithium manganese-based positive electrode active material in the positive electrode sheet is Li2ZrO3, while all other aspects are the same as in Example 1.

[0147] Performance testing

[0148] (1) Initial discharge capacity test: The assembled all-solid-state battery cell was charged to 4.18V (4.8V for lithium potential) at a current density of 0.1C, allowed to stand for 10 minutes, and then discharged to 1.38V (2.0V for lithium potential) at a current density of 0.1C to obtain the initial discharge capacity of the battery. The battery was tested at 25℃, where 1C = 200mA / g.

[0149] (2) Initial Coulombic Efficiency: The initial Coulombic efficiency of the battery can be obtained by dividing the initial discharge capacity obtained by testing at 0.1C by the initial charge capacity.

[0150] (3) Cycle capacity retention test: The assembled all-solid-state 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.

[0151] The test results are shown in Table 2.

[0152] Table 1

[0153] Table 2

[0154] The data in the table above shows that, compared to the comparative examples, coating the surface of the lithium manganese-based cathode active material with thiocyanate in Examples 1-8 can significantly improve the specific capacity, initial coulombic efficiency, and capacity retention of the battery cells. By appropriately adjusting the coating weight and the type of thiocyanate, the battery performance can be further improved. Among them, Example 5 with potassium thiocyanate coating and Example 6 with magnesium thiocyanate coating have better performance, and Example 6 has the best overall performance.

[0155] 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 and a negative electrode. The positive electrode includes a positive current collector and a positive active layer stacked on at least one surface of the positive current collector. The positive active layer contains a composite positive electrode material. The composite positive electrode material includes a core and a coating layer covering the surface of the core. The core includes a lithium manganese-based positive active material, and the coating layer includes a thiocyanate.

2. The battery cell as described in claim 1, characterized in that, The thiocyanate includes at least one of alkali metal thiocyanates, alkaline earth metal thiocyanates, and transition metal thiocyanates.

3. The battery cell as described in claim 2, characterized in that, The alkali metal thiocyanate includes at least one of NaSCN, KSCN and RbSCN; Alternatively, the alkaline earth metal thiocyanate includes at least one of Mg(SCN)2, Ca(SCN)2 and Sr(SCN)2; Alternatively, the transition metal thiocyanate may include at least one of Fe(SCN)3 and Cu(SCN)2.

4. The battery cell according to any one of claims 1-3, characterized in that, The mass ratio of the thiocyanate to the lithium manganese-based positive electrode active material is (0.1-10):100; And / or, the thickness of the coating layer is 0.1 nm-50 nm.

5. The battery cell according to any one of claims 1-4, characterized in that, The general chemical formula of the lithium manganese-based positive electrode active material is xLi2MnO3·(1-x)LiMO2; wherein M includes at least one of Ni, Co, Mn, Cr, Fe, Al, Nb, Zr, Mo, Ta, and Ru, and 0 < x < 1.

6. The battery cell according to any one of claims 1-5, characterized in that, The battery cell includes a solid-state battery cell, and a solid electrolyte layer is disposed between the positive electrode and the negative electrode.

7. The battery cell as described in claim 6, characterized in that, The positive electrode active layer contains a solid electrolyte, and both the solid electrolyte and the electrolyte in the solid electrolyte layer are sulfide electrolytes.

8. The battery cell as described in claim 7, characterized in that, The particle size D of the solid electrolyte V 50 is less than 1μm.

9. The battery cell according to any one of claims 7-8, characterized in that, The positive electrode active layer also contains a conductive agent and a binder, and the mass ratio of the composite positive electrode material, the solid electrolyte, the conductive agent and the binder is (50-99):(0.1-50):(0.1-5):(0.1-5).

10. A battery device, characterized in that, Includes the battery cell as described in any one of claims 1-9.

11. An electrical appliance, characterized in that, Includes a battery cell as described in any one of claims 1-9 or a battery device as described in claim 10, wherein the battery cell or the battery device is used to store or provide electrical energy.

12. A composite cathode material, characterized in that, The composite cathode material includes a core and a coating layer covering the surface of the core. The core includes a lithium manganese-based cathode active material, and the coating layer includes thiocyanate.

13. The composite cathode material as described in claim 12, characterized in that, The thiocyanate includes at least one of alkali metal thiocyanates, alkaline earth metal thiocyanates, and transition metal thiocyanates.

14. The composite cathode material as described in claim 13, characterized in that, The alkali metal thiocyanate includes at least one of NaSCN, KSCN and RbSCN; Alternatively, the alkaline earth metal thiocyanate includes at least one of Mg(SCN)2, Ca(SCN)2 and Sr(SCN)2; Alternatively, the transition metal thiocyanate may include at least one of Fe(SCN)3 and Cu(SCN)2.

15. The composite cathode material according to any one of claims 12-14, characterized in that, The mass ratio of the thiocyanate to the lithium manganese-based positive electrode active material is (0.1-10):100; And / or, the thickness of the coating layer is 0.1 nm-50 nm.

16. The composite cathode material according to any one of claims 12-15, characterized in that, The general chemical formula of the lithium manganese-based positive electrode active material is xLi2MnO3·(1-x)LiMO2; wherein M includes at least one of Ni, Co, Mn, Cr, Fe, Al, Nb, Zr, Mo, Ta, and Ru, and 0 < x < 1.

17. A method for preparing a composite cathode material, characterized in that, include: Provides lithium manganese-based cathode active materials and thiocyanates; The thiocyanate is coated onto the surface of the lithium manganese-based cathode active material to form a coating layer, thereby obtaining a composite cathode material.

18. The preparation method according to claim 17, characterized in that, The step of coating the thiocyanate onto the surface of the lithium manganese-based positive electrode active material to form a coating layer includes: The thiocyanate and the lithium manganese-based positive electrode active material are dry-mixed and then heat-treated at 280–320°C in an oxygen atmosphere.

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