Lithium-rich lithium ferrite material, method for manufacturing the same, and use

Abstract

This application provides a lithium-rich lithium ferrite material, a method for producing the same, and a use thereof, and belongs to the field of cathode materials. The lithium-rich lithium ferrite material comprises a core-shell structure particle, the core-shell structure particle comprising a core, a first coating layer covering the outside of the core, and a second coating layer covering the outside of the first coating layer, wherein the core is Li5FeO4, the first coating layer is a carbon layer, and the second coating layer is a mixed layer containing polyoxyethylene and a lithium salt, the mass ratio of the first coating layer to the core is (2:100) to (10:100), and the mass ratio of the second coating layer to the core is (3:100) to (13:100). This application helps to improve the stability of lithium ferrite in air and can also increase the ionic conductivity of the entire electrode.

Description

[Technical Field]

[0001] This invention relates to the technical field of positive electrode materials for lithium-ion batteries, and more specifically to lithium-rich lithium ferrite materials, methods for manufacturing the same, and uses thereof. [Background technology]

[0002] With the rapid development of the new energy sector in China, lithium-ion batteries are attracting widespread attention, but the issue of battery life in electric vehicles has traditionally been a key factor limiting further market entry for electric vehicles. Existing high-capacity anodes such as hard carbon anodes and silicon anodes have high capacity, but all of them form a large solid electrolyte interface (SEI) film, and the cathode has a large amount of Li + Because it consumes Li irreversibly, it has a serious impact on the overall capacity of the lithium-ion battery. Li consumed by the formation of the EI film + Supplementing this by pre-lithiumization is the most effective solution to the problem of low initial Coulombic efficiency in high-capacity anodes.

[0003] To further promote the use of a new generation of high-capacity anodes in future lithium-ion batteries, many pre-lithiation methods have been developed to enable batteries to adapt to high-capacity, low-initial-coulomb efficiency anodes and compensate for the loss of active lithium during the first cycle. Pre-lithiation strategies mainly include cathode pre-lithiation and anode pre-lithiation. Of these, anode pre-lithiation received widespread attention in the initial stages, while in recent years, cathode pre-lithiation strategies have attracted increasing attention due to their advantages such as high safety, low cost, easy synthesis, and high rechargeability.

[0004] Among the lithium replenishers used in the pre-lithiumization of the positive electrode, Li5FeO4 has a theoretical specific capacity of 864 mAh g. -1Theoretically, this is sufficient to significantly improve the capacity decay caused by the combination of existing cathodes with new anodes such as hard carbon or silicon-oxygen. Furthermore, Li5FeO4 is compatible with existing cathode materials, is compatible with existing binder systems, and can be added directly to cathode materials. In addition, Li5FeO4 is relatively inexpensive compared to other lithium replenishers, so its application as a lithium-rich additive for cathodes is promising. However, Li5FeO4 is very sensitive to water and CO2 in the air, has poor stability in air, and seriously impacts industrialization processes. [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In view of the technical challenges described in the background art, this application provides a lithium-rich lithium ferrite material, a method for manufacturing the same, and a method for using the same, in order to improve the stability of the lithium-rich lithium ferrite material in air. [Means for solving the problem]

[0006] In the first aspect, the embodiments of the present application are as follows: The present invention provides a lithium-rich lithium ferrite material comprising core-shell structure particles, wherein the core-shell structure particles comprise a core, a first coating layer covering the outside of the core, and a second coating layer covering the outside of the first coating layer, wherein the core is Li5FeO4, the first coating layer is a carbon layer, and the second coating layer is a mixed layer containing polyoxyethylene and a lithium salt, the mass ratio of the first coating layer to the core is (2:100) to (10:100), and the mass ratio of the second coating layer to the core is (3:100) to (13:100).

[0007] In the lithium-rich lithium ferrite material according to the present invention, the first coating layer and the second coating layer are sequentially provided outside the core containing Li5FeO4, the first coating layer being a carbon layer, and the second coating layer being a mixed layer containing polyoxyethylene (PEO) and a lithium salt. By sequentially providing the first and second coating layers outside the core, on the one hand, the double coating prevents the Li5FeO4 in the core from being affected by moisture and carbon dioxide in the air, thereby improving the stability of the lithium-rich lithium ferrite material in air. On the other hand, the outermost second coating layer is a mixed layer containing polyoxyethylene and a lithium salt, where polyoxyethylene can increase the conductivity of the material and improve the strength and uniformity of the coating layer, and the lithium salt can further increase the conductivity of the coating layer, thereby effectively improving the ionic conductivity of the lithium-rich lithium ferrite material.

[0008] In some embodiments, the mass ratio of the polyoxyethylene to the core is (0.5:100) to (5:100), and the mass ratio of the lithium salt to the core is (2:100) to (8:100).

[0009] In this embodiment, under the same conditions as other components, if the amount of polyoxyethylene used is too high, the lithium-rich lithium ferrite material particles will stick together, and if the amount of polyoxyethylene used is too low, complete and continuous coating becomes impossible. If the amount of lithium salt used is too high, the polyoxyethylene content in the mixed layer decreases, reducing the adhesive force between the carbon layer and the mixed layer, and also reducing the strength of the mixed layer. If the amount of lithium salt used is too low, the conductivity of the lithium-rich lithium ferrite material decreases.

[0010] In some embodiments, the mass ratio of the polyoxyethylene to the core is (0.5:100) to (2:100), and the mass ratio of the lithium salt to the core is (2:100) to (4:100).

[0011] In this embodiment, by adjusting the amount of polyoxyethylene and lithium salt used in the second coating layer, the mass ratio of the polyoxyethylene to the core can be set to (0.5:100) to (2:100), and the mass ratio of the lithium salt to the core can be set to (2:100) to (4:100). This provides a combination of conductivity, coating uniformity, and continuity, while minimizing adhesion between the lithium-rich lithium ferrite material particles.

[0012] In some embodiments, the mass ratio of the carbon layer to the core is (5:100) to (7:100).

[0013] In this embodiment, by setting the mass ratio of the carbon layer to the core to (5:100) to (7:100), it is possible to continuously and uniformly coat the core with the carbon layer, and on the other hand, to avoid the other properties of the manufactured lithium-rich lithium ferrite material being affected by an excessively high proportion of the carbon layer, thereby enabling the manufactured lithium-rich lithium ferrite material to have high capacity and stability while maintaining uniform coating of the core.

[0014] In some embodiments, the lithium salt is at least one selected from lithium bis(fluorosulfonyl)imide, lithium hexafluoride phosphate, and lithium fluoride.

[0015] In this example, at least one selected from lithium bis(fluorosulfonyl)imide, lithium hexafluoride phosphate, and lithium fluoride can effectively improve the conductivity of the mixed layer.

[0016] In some embodiments, the molecular weight of the polyoxyethylene is between 50,000 Da and 150,000 Da.

[0017] In this embodiment, high molecular weight polyoxyethylene forms a uniform and continuous polymer network structure, which is likely to result in better ionic conductivity. However, if the molecular weight of polyoxyethylene is too high, it becomes difficult to uniformly coat the surface of the carbon layer. Therefore, polyoxyethylene with a molecular weight of 50,000 Da to 150,000 Da is used.

[0018] In some embodiments, the D90 particle size of the core is 3 μm to 5.5 μm.

[0019] In this embodiment, by controlling the particle size of the core, it is advantageous that the particle size of the finally produced lithium-rich lithium ferrite material is also controlled within a narrow range. The lithium-rich lithium ferrite material with a small particle size is likely to be uniformly mixed with other components in the cathode active material and is further advantageously uniformly distributed on the current collector.

[0020] In some embodiments, the average thickness of the first coating layer is 5 nm to 10 nm, and the average thickness of the second coating layer is 5 nm to 10 nm.

[0021] In this embodiment, while performing continuous coating, it is realized to reduce the thickness of the coating layer, which is advantageous for ensuring the capacity of the lithium-rich lithium ferrite material, improving conductivity, and maintaining a small particle size of the lithium-rich lithium ferrite material.

[0022] In the second aspect, the embodiments of the present application include steps of providing a core and a coating solution, forming a first coating layer on the surface of the core to obtain an intermediate product, mixing the intermediate product and the coating solution to form a second coating layer on the surface of the first coating layer to obtain the lithium-rich lithium ferrite material, where the coating solution includes a solvent, polyoxyethylene, and a lithium salt, and provides a method for manufacturing the aforementioned lithium-rich lithium ferrite material.

[0023] In this example, the lithium-rich lithium ferrite material can be obtained simply by coating a core containing Li5FeO4 twice. The manufacturing method is simple, and a lithium-rich lithium ferrite material with a small particle size of 3 μm to 5.5 μm (D90 particle size) can be obtained. The manufactured lithium-rich lithium ferrite material has excellent stability in air and ionic conductivity.

[0024] In some embodiments, the step of forming the first coating layer on the surface of the core includes mixing the core with a carbon source and a grinding aid, ball milling, and then carbonizing it to obtain the intermediate product.

[0025] In this embodiment, by employing the ball milling method, the core and the carbon source are mixed more uniformly, and it is necessary to remove the grinding aid before the carbonization treatment. The carbonization treatment step forms a first coating layer (carbon layer) on the surface of the core, and an intermediate product can be obtained.

[0026] In some embodiments, the carbon source is at least one selected from polypropylene, glucose, and high-temperature coal pitch.

[0027] In this example, polypropylene, glucose, and high-temperature coal pitch are all readily available and inexpensive, making them advantageous for cost reduction. Among these, high-temperature coal pitch is particularly stable, and when used as a carbon source, it has the effect of significantly improving the stability of lithium-rich lithium ferrite materials.

[0028] In some embodiments, the carbonization treatment is performed at a temperature of 500°C to 700°C for 1.5 hours to 3 hours.

[0029] In this embodiment, if the carbonization temperature is too low, carbonization will not be sufficient, and if the carbonization temperature is too high, the structure of Li5FeO4 in the core will be affected. Therefore, in this embodiment, the carbonization temperature is set to 500°C to 700°C and the time to 1.5h to 3h, thereby ensuring the formation of a uniform carbon layer that does not affect the structure of the core.

[0030] In some embodiments, the manufacturing method further includes the step of forming the first coating layer on the surface of the core and manufacturing the core before obtaining an intermediate product, The process includes a step of calcining a first mixture of an iron source and a lithium source at 500°C to 700°C for 24 to 48 hours under an inert atmosphere.

[0031] In this embodiment, calcining the mixture of iron and lithium sources at 500°C to 700°C for 24 to 48 hours under an inert atmosphere is advantageous for complete reaction between the iron and lithium sources. If the calcination temperature is too low or the time is too short, the crystallinity of the product will be poor, while if the sintering temperature is too high or the time is too long, the structure will be destroyed. In either case, the lithium replenishment effect of the manufactured lithium-rich lithium ferrite material will be impaired.

[0032] In some embodiments, the iron source is Fe2O3.

[0033] In this embodiment, using Fe2O3 is advantageous for obtaining Li5FeO4 cores with small particle sizes compared to other iron sources such as iron hydroxide.

[0034] In some embodiments, the D90 particle diameter of the iron source is 400 nm or less.

[0035] In this embodiment, the particle size of the iron source affects the particle size of the core, and further affects the particle size of the lithium-rich lithium ferrite material finally produced. If the particle size of the iron source is too large, the particle size of the lithium-rich lithium ferrite material finally produced will also be large, which is unfavorable for the uniform distribution of the lithium-rich lithium ferrite material on the current collector. Preferably, the D90 particle size of the iron source is 200 nm to 400 nm, and when the D90 particle size of the iron source is 200 nm to 400 nm, it is advantageous to obtain a Li5FeO4 core with a small particle size.

[0036] In some embodiments, the lithium source is at least one selected from lithium oxide, lithium hydroxide, and lithium carbonate.

[0037] In this embodiment, lithium oxide, lithium hydroxide, and lithium carbonate are readily available and easy to mass-produce, improving the industrial applicability of this method.

[0038] In some embodiments, the lithium source is a second mixture of lithium oxide and lithium hydroxide.

[0039] In this embodiment, lithium carbonate has a high decomposition temperature and causes severe corrosion to the container, and when used alone as a lithium source, caking is severe. On the other hand, lithium oxide is expensive. Considering this, a second mixture of lithium hydroxide and lithium oxide is used as a lithium source to reduce costs and minimize caking.

[0040] In some embodiments, the lithium source is a second mixture obtained by mixing lithium oxide and lithium hydroxide in a molar ratio of (1.5 to 2.5):1.

[0041] In this embodiment, a second mixture of lithium oxide and lithium hydroxide in a molar ratio of (1.5 to 2.5):1 is used as the lithium source, thereby avoiding caking while reducing costs.

[0042] In some embodiments, the molar ratio of Fe to Li in the first mixture is (1:5.0) to (1:5.2).

[0043] In this embodiment, introducing an excess of lithium is advantageous in increasing the lithium content in the lithium replenisher and further improving the lithium replenishment effect.

[0044] In some embodiments, after mixing the intermediate product with the coating solution, the solvent is removed, the mixture is pulverized and sieved, and a second coating layer is formed on the surface of the first coating layer to obtain the lithium-rich lithium ferrite material.

[0045] In this example, the solvent may be acetonitrile or a solvent with similar polarity to acetonitrile. The presence of the solvent contributes to the uniform and continuous coating of polyoxyethylene and the lithium source onto the surface of the intermediate product. However, only the properties of polyoxyethylene itself are considered, and while high molecular weight polyoxyethylene readily forms a uniform and continuous polymer network structure, if the molecular weight of the polyoxyethylene is too high, it becomes difficult to dissolve the polyoxyethylene in solvents such as acetonitrile, further affecting the continuity and uniformity of the coating.

[0046] In a third aspect, an embodiment of the present application includes a current collector providing a positive electrode plate and an active material layer provided on at least one side of the current collector, wherein the active material layer includes a lithium-rich lithium ferrite material as described in any one of the preceding paragraphs or a lithium-rich lithium ferrite material manufactured by the manufacturing method described in any one of the preceding paragraphs.

[0047] In this embodiment, the active material layer of the positive electrode plate contains a lithium-rich lithium ferrite material. This significantly improves the stability of the lithium-rich lithium ferrite material in air, making it easier for lithium to be replenished. When a positive electrode plate containing lithium-rich lithium ferrite material is used in a battery, it is advantageous for achieving the overall capacity of the battery.

[0048] In some embodiments, the mass fraction of the lithium-rich lithium ferrite material in the active material layer is 2 wt% to 8 wt%. This is because Li consumed by SEI film formation. + It contributes to replenishing.

[0049] In a fourth aspect, an embodiment of the present application provides a secondary battery including the aforementioned positive electrode plate.

[0050] In this embodiment, since the secondary battery includes the above-mentioned positive electrode plate, a high capacity is maintained.

[0051] In a fifth aspect, an embodiment of the present application provides a power consumption device including the aforementioned secondary battery.

[0052] In this embodiment, the power consumption device includes the above-mentioned secondary battery, which has the advantage of a long service life.

[0053] The above description is merely an outline of the technical solution of the present application. In order to understand the technical means of the present application more clearly, and to make the above-mentioned objectives, other objectives, features, and advantages of the present application clearer and easier to understand, specific embodiments of the present application are given below, which can be implemented according to the contents of the instruction manual. [Brief explanation of the drawing]

[0054] To more clearly explain the technical solution of this application, the drawings used in this application are briefly described below. As is clear, the drawings described below represent only some embodiments of this application, and those skilled in the art can derive other drawings from these without any creative work.

[0055] [Figure 1] This is a schematic diagram of the structure of the lithium-rich lithium ferrite material in an embodiment of the present invention. [Figure 2] This is a schematic diagram of the process for manufacturing a lithium-rich lithium ferrite material in an embodiment of the present invention. [Figure 3]This is a schematic diagram of the manufacturing process flow for the lithium-rich lithium ferrite material in Example 1 of the present invention. [Figure 4] This is an SEM test chart of the lithium-rich lithium ferrite material manufactured in Example 1 of the present invention. [Figure 5] Figure 4 is a magnified view of a portion of the SEM test chart for lithium-rich lithium ferrite material shown in Figure 4. [Figure 6] These are the specific capacity data for the lithium-rich lithium ferrite materials manufactured in Examples 1 to 3 of this application. [Figure 7] This is an XRD test chart of Li5FeO4 before and after coating in Example 1 of the present application. [Modes for carrying out the invention]

[0056] The following descriptions will detail embodiments of the technical solution of the present application with reference to the drawings. The following embodiments are provided solely as examples to more clearly illustrate the technical solution of the present application and will not limit the scope of protection of the present application.

[0057] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art. Terms used herein are used solely to describe specific embodiments and are not intended to limit this application. The terms “including” and “having,” and their variations, in the description of the specification, claims, and drawings above, are intended to cover non-exclusive inclusion.

[0058] In the description of the embodiments of this application, the technical terms "first," "second," etc., are used solely to distinguish different subjects and are not to be understood as indicating or implying relative importance, or implicitly indicating the number, specific order, or primary / secondary relationship of the technical features shown. In the description of the embodiments of this application, "plural" means two or more unless otherwise clearly and specifically limited.

[0059] The “Examples” described herein mean that certain features, structures, or properties described with reference to the Examples may be included in at least one Example of the Application. The appearance of such phrase in various places in the Specification does not necessarily refer to the same Example, nor does it refer to mutually exclusive, independent, or alternative Examples. As those skilled in the art will understand both expressly and implicitly, the Examples described herein may be combined with other Examples.

[0060] In the description of the embodiments of this application, the term "and / or" merely describes the relationship between related objects, indicating that three types of relationships may exist. For example, in the case of A and / or B, three situations can be described: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the symbol " / " in this specification generally indicates that the preceding and succeeding related objects are in an "or" relationship.

[0061] In the description of the embodiments of this application, the term "multiple" means two or more (including two), similarly, "multiple sets" means two or more sets (including two sets), and "multiple sheets" means two or more sheets (including two sheets).

[0062] In the description of embodiments of the present application, the directions or positional relationships indicated by technical terms such as "center," "vertical direction," "horizontal direction," "length," "width," "thickness," "top," "bottom," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inside," "outside," "clockwise," "counterclockwise," "axial direction," "radial direction," and "circumferential direction" are based on the directions or positional relationships shown in the drawings and are merely intended to facilitate and simplify the description of embodiments of the present application. They do not indicate or imply that the devices or elements mentioned need to have a specific direction, or be configured and operated in a specific direction, and therefore should not be interpreted as limiting embodiments of the present application.

[0063] Li5FeO4 has high theoretical specific capacity, good compatibility with existing cathode materials and binders, and a relatively low price, making it promising for future applications. However, Li5FeO4 is highly sensitive to water and CO2 in the air, resulting in poor stability in air, which seriously impacts its industrialization process. To address the technical challenge of poor stability of lithium-rich lithium ferrite materials in air, this invention provides a lithium-rich lithium ferrite material, a method for manufacturing the same, a cathode plate, a secondary battery, and a power consumption device. By providing a carbon layer and a mixed layer consisting of polyoxyethylene and a lithium salt outside the core containing Li5FeO4, the technical effect of improving the stability of the lithium-rich lithium ferrite material in air is achieved, and furthermore, the electrical characteristics of the cathode plate, secondary battery, and power consumption device are also improved.

[0064] The power consumption devices according to the embodiments of this application may be, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, battery cars, electric vehicles, ships, spacecraft, etc. Among these, electric toys include stationary or mobile electric toys such as game consoles, electric vehicle toys, electric boat toys, and electric airplane toys, and spacecraft may include airplanes, rockets, space shuttles, and spacecraft.

[0065] As shown in Figure 1, in the first embodiment, the embodiment of the present application provides a lithium-rich lithium ferrite material comprising core-shell structure particles, the core-shell structure particles comprising a core, a first coating layer covering the outside of the core, and a second coating layer covering the outside of the first coating layer, wherein the core is Li5FeO4, the first coating layer is a carbon layer, and the second coating layer is a mixed layer containing polyoxyethylene and a lithium salt, the mass ratio of the first coating layer to the core is (2:100) to (10:100), and the mass ratio of the second coating layer to the core is (3:100) to (13:100).

[0066] In the lithium-rich lithium ferrite material according to the present invention, a first coating layer and a second coating layer are sequentially provided outside the core containing Li5FeO4. The first coating layer is a carbon layer, and the second coating layer is a mixed layer containing polyoxyethylene and a lithium salt. By sequentially providing the first and second coating layers outside the core, on the one hand, the double coating prevents the Li5FeO4 in the core from being affected by moisture and carbon dioxide in the air, thereby improving the stability of the lithium-rich lithium ferrite material in air. On the other hand, the outermost second coating layer is a mixed layer containing polyoxyethylene and a lithium salt, i.e., a solid electrolyte layer, which improves the overall electronic conductivity and ionic conductivity of the lithium-rich lithium ferrite material.

[0067] The mass ratio of the first coating layer to the core is (2:100) to (10:100), and the mass ratio of the second coating layer to the core is (3:100) to (13:100). In the first coating layer, because the specific capacity of the carbon layer is low, if the proportion of the carbon layer is too high, the overall capacity of the manufactured lithium-rich lithium ferrite material decreases, and if the proportion of the carbon layer is too low, complete and continuous coating cannot be achieved, and the core containing Li5FeO4 cannot be sufficiently isolated from the air. In the second coating layer, if the proportion of the mixed layer is too high, the particles of the manufactured lithium-rich lithium ferrite material will stick together, and the particle size of the lithium-rich lithium ferrite material will increase, and if the proportion of the mixed layer is too low, complete and continuous coating cannot be achieved, and the core containing Li5FeO4 cannot be sufficiently isolated from the air. Furthermore, the electronic conductivity and ionic conductivity of the entire lithium-rich lithium ferrite material are also affected. Therefore, if a complete and continuous coating layer can be formed, the proportion of the second coating layer should be kept as low as possible.

[0068] Specifically, the mass ratio of the first coating layer to the core may be 2:100, 4:100, 6:100, 8:100, 10:100, or any value between (2:100) and (10:100), but preferably (5:100) to (7:100). The mass ratio of the second coating layer to the core may be 3:100, 5:100, 7:100, 9:100, 11:100, 13:100, or any value between (3:100) and (13:100).

[0069] In some embodiments, the mass ratio of polyoxyethylene to core is (0.5:100) to (5:100), and the mass ratio of lithium salt to core is (2:100) to (8:100), preferably the mass ratio of polyoxyethylene to core is (0.5:100) to (2:100), and the mass ratio of lithium salt to core is (2:100) to (4:100).

[0070] Polyoxyethylene functions as a solid electrolyte that enhances the conductivity of the material, while also possessing some degree of adhesion, which can improve the strength and uniformity of the coating layer. Lithium salts can further improve the conductivity of the coating. Under the same conditions as other components, if the amount of polyoxyethylene used is too high, the lithium-rich lithium ferrite material particles will stick together, while if the amount of polyoxyethylene used is too low, a complete and continuous coating becomes impossible. If the amount of lithium salt used is too high, the polyoxyethylene content in the mixed layer decreases, reducing the adhesion between the carbon layer and the mixed layer, and also reducing the strength of the mixed layer. If the amount of lithium salt used is too low, the conductivity of the lithium-rich lithium ferrite material decreases.

[0071] Specifically, the mass ratio of polyoxyethylene to the core may be 0.5:100, 1:100, 2:100, 1.4:100, 3:100, 4:100, 5:100, or any value between (0.5:100) and (5:100), and the mass ratio of lithium salt to the core may be 2:100, 3:100, 4:100, 5:100, 6:100, 7:100, 8:100, or any value between (2:100) and (8:100).

[0072] In some embodiments, the lithium salt is at least one selected from lithium bis(fluorosulfonyl)imide, lithium hexafluoride phosphate, and lithium fluoride, specifically, one of lithium bis(fluorosulfonyl)imide, lithium hexafluoride phosphate, and lithium fluoride, a mixture of lithium bis(fluorosulfonyl)imide and lithium hexafluoride phosphate, a mixture of lithium hexafluoride phosphate and lithium fluoride, or a mixture of lithium bis(fluorosulfonyl)imide, lithium hexafluoride phosphate, and lithium fluoride.

[0073] In some embodiments, the molecular weight of the polyoxyethylene is between 50,000 Da and 150,000 Da, specifically 50,000 Da, 70,000 Da, 90,000 Da, 110,000 Da, 130,000 Da, 150,000 Da, or any value between 50,000 Da and 150,000 Da. This contributes to the formation of a uniform and continuous polymer network structure, resulting in better ionic conductivity.

[0074] In some embodiments, the core's D90 particle diameter is 3 μm to 5.5 μm, specifically 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, or any value between 3 μm and 5.5 μm.

[0075] In some embodiments, the average thickness of the first coating layer is 5 nm to 10 nm, and specifically, it may be 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, or any value between 5 nm and 10 nm.

[0076] In some embodiments, the average thickness of the second coating layer is 5 nm to 10 nm, and specifically, it may be 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, or any value between 5 nm and 10 nm.

[0077] In a second embodiment, the embodiment of the present application provides a method for manufacturing a lithium-rich lithium ferrite material as described in any one of the preceding paragraphs, the manufacturing method comprising the following steps as shown in Figure 2.

[0078] S1: Provides the core and coating liquid.

[0079] S2: A first coating layer is formed on the surface of the core to obtain an intermediate product.

[0080] S3: The intermediate product and coating solution are mixed to form a second coating layer on the surface of the first coating layer, thereby obtaining a lithium-rich lithium ferrite material.

[0081] The coating solution contains a solvent, polyoxyethylene, and a lithium salt.

[0082] In the manufacturing method of the present invention, a lithium-rich lithium ferrite material can be obtained by simply coating a core containing Li5FeO4 twice. The manufacturing method is simple, and a lithium-rich lithium ferrite material with a small particle size of 3 μm to 5.5 μm in D90 particle size can be obtained.

[0083] Specifically, in step S1, the method for manufacturing the core is: The process includes a step of calcining a first mixture of an iron source and a lithium source in an inert atmosphere at 500°C to 700°C for 24 to 48 hours. The calcination temperature may be 500°C, 550°C, 600°C, 650°C, 700°C, or any value between 500°C and 700°C, and the calcination time may be 24 hours, 28 hours, 32 hours, 36 hours, 40 hours, 44 hours, 48 ​​hours, or any value between 24 hours and 48 hours.

[0084] In some embodiments, the iron source and lithium source may be uniformly mixed by a mixer, and the mixing time may be adjusted according to the volume and rotation speed of the mixer to ensure that the iron source and lithium source are mixed as uniformly as possible.

[0085] In some embodiments, the first mixture may be sent to a sintering furnace for calcination during the calcination step, and an inert gas may be introduced beforehand. The amount of inert gas introduced is 5 m³. 3 / h~10m 3The temperature is set to / h, which ensures that the oxygen content in the sintering furnace is less than 1 ppm and the humidity is less than 5%, thus preventing carbon dioxide and water from reacting with the first mixture. Subsequently, the sintering furnace is heated at a rate of 3°C / min to 7°C / min to perform sintering.

[0086] In some embodiments, the iron source is Fe2O3, and the D90 particle size of the iron source is 400 nm or less, specifically any value of 400 nm, 350 nm, 300 nm, 250 nm, 200 nm, 150 nm, or 400 nm or less. Preferably, the D90 particle size of the iron source is 200 nm to 400 nm.

[0087] In some embodiments, the lithium source is at least one selected from lithium oxide, lithium hydroxide, and lithium carbonate. Preferably, the lithium source is a second mixture of lithium oxide and lithium hydroxide. Specifically, the lithium source is a mixture of lithium oxide and lithium hydroxide in a molar ratio of (1.5 to 2.5):1, for example, the molar ratio of lithium oxide to lithium hydroxide may be 1.5:1, 1.7:1, 1.9:1, 2.1:1, 2.3:1, 2.5:1, or any value between (1.5 to 2.5):1.

[0088] In some embodiments, the molar ratio of Fe to Li in the second mixture of the iron source and the lithium source is 1:(5.0~5.2), and specifically may be 1:5.0, 1:5.05, 1:5.1, 1:5.15, 1:5.2, or any value between 1:(5.0~5.2).

[0089] The Li5FeO4 obtained in this embodiment may be used after being pulverized, specifically by jet pulverization. For example, sintered Li5FeO4 may be jet-pulverized to maintain a dew point below -30°C and obtain a pure phase of Li5FeO4 with a particle size range of 3 μm to 5.5 μm.

[0090] Specifically, in step S2, the step of forming a first coating layer on the surface of the core includes mixing the core with a carbon source and a grinding aid, ball milling, and then carbonizing it to obtain an intermediate product.

[0091] In this embodiment, the core and carbon source are uniformly mixed by ball milling, and the ball milling may be set to a rotation speed of 300 rpm to 600 rpm, a time of 1 to 5 hours, and a ball / material ratio of (8 to 12):1. The grinding aid must be removed before the carbonization treatment. The grinding aid may be an alcohol compound, such as ethanol, and the means for removing the grinding aid may be to volatilize it by baking.

[0092] In some embodiments, the carbon source is at least one selected from polypropylene, glucose, and high-temperature coal pitch. For example, the carbon source may be polypropylene, glucose, high-temperature coal pitch, a mixture of polypropylene and glucose, a mixture of glucose and high-temperature coal pitch, and a mixture of all three: polypropylene, glucose, and high-temperature coal pitch.

[0093] Coal pitch is a multiphase system, and its basic components include aliphatic hydrocarbons, cycloalkanes, polycyclic hydrocarbons, fused cyclic hydrocarbons, and heterocyclic aromatic hydrocarbons. At room temperature, it is in the glass phase, and when heated, it softens and melts. For this reason, coal pitch is classified into low-temperature coal pitch (CTPD) below 75°C, medium-temperature coal pitch (CTPZ) between 75°C and 95°C, and high-temperature coal pitch (CTPG) above 95°C, depending on its softening point.

[0094] In some embodiments, the carbonization temperature is 500°C to 700°C, specifically 500°C, 550°C, 600°C, 650°C, 700°C, or any value between 500°C and 700°C, and the duration is 1.5h to 3h, specifically 1.5h, 2h, 2.5h, 3h, or any value between 1.5h and 3h.

[0095] In this application, the carbonization step involves placing a Li5FeO4 precursor coated with a carbon source into a sintering furnace and firing it at a high temperature. To reduce oxidation of the carbon source, it is necessary to introduce an inert gas beforehand. The amount of inert gas introduced is 3 m³. 3 / h~7m 3 The rate may be / h. This ensures that the oxygen content in the sintering furnace is less than 1 ppm and the humidity is less than 5%, preventing oxygen from reacting with water or the carbon source and affecting the carbonization process. Subsequently, the sintering furnace is heated to 500°C to 700°C at a heating rate of 3°C / min to 7°C / min, and maintained at this temperature for 1.5 to 3 hours to obtain an intermediate product. The intermediate product is then jet-pulverized, maintaining a dew point below -30°C, to obtain an intermediate product with a particle size of 3 μm to 5.5 μm.

[0096] Specifically, in step S3, the intermediate product and coating solution are mixed, the solvent is removed, and the mixture is pulverized and sieved to obtain a lithium-rich lithium ferrite material. Here, the solvent may be acetonitrile or a solvent with similar polarity to acetonitrile. The amount of solvent required is sufficient to completely dissolve the polyoxyethylene. If there is too much solvent, it can be removed later by baking, and the impact on the overall properties of the material will not be significant, but the time required for solvent removal will be longer, energy consumption will increase, and production efficiency and cost will be affected. On the other hand, if there is too little solvent, the polyoxyethylene cannot be completely dissolved, and the uniformity and continuity of the coating layer will be impaired.

[0097] Furthermore, in the coating solution, the mass ratio of polyoxyethylene to lithium salt is (20-50):100, specifically, it may be 20:100, 30:100, 40:100, 50:100, or any value between (20-50):100, preferably (30-40):100. When the ratio of polyoxyethylene to lithium salt is adjusted, the mass ratio of polyoxyethylene to core is (0.5:100) to (2:100), the mass ratio of lithium salt to core is (2:100) to (4:100), and the mass ratio of polyoxyethylene to lithium salt is (20-50):100, it is possible to further combine conductivity, coating uniformity and continuity, and avoid adhesion between lithium-rich lithium ferrite material particles.

[0098] Furthermore, while the solvent removal rate can be increased by raising the temperature, the temperature should not be too high in order to avoid damaging the structure of the lithium-rich lithium ferrite material. In addition, after the solvent has been removed, the lithium-rich lithium ferrite material may be crushed to reduce the particle size. Specifically, jet pulverization may be used as the crushing method.

[0099] In a third aspect, an embodiment of the present application provides a positive electrode plate comprising a positive electrode current collector and an active material layer provided on at least one side of the positive electrode current collector, wherein the active material layer includes a lithium-rich lithium ferrite material as described in any one of the preceding paragraphs or a lithium-rich lithium ferrite material manufactured by the manufacturing method described in any one of the preceding paragraphs.

[0100] In some embodiments, the mass fraction of lithium-rich lithium ferrite material in the active material layer is 2wt% to 8wt%, specifically 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, or any value between 2wt% and 8wt%, and the specific amount used may be determined according to the lithium replenishment efficiency.

[0101] In the fifth aspect, the embodiments of the present application provide a power consumption device, such as a vehicle, including the secondary battery of the above embodiments.

[0102] Hereinafter, several specific embodiments will be listed. However, the embodiments described below are illustrative and are only used for interpreting the present application, and are not to be understood as limiting the present application. When specific technologies or conditions are not specified in the embodiments, they shall be carried out according to the technologies or conditions described in the literature of this field or according to the product manuals. When the reagents or instruments used are not specified by the manufacturer, they are all ordinary products that can be obtained commercially.

[0103] 1. Manufacturing method Example 1 This example provides a method for manufacturing a lithium-rich lithium ferrite material including the following steps.

[0104] (1) Weigh nano-Fe2O3 with D90 of 300 nm, Li2O, and LiOH, and maintain Fe:Li = 1:5.1 (this ratio is the molar ratio of Fe element to Li element, the same below), and LiOH:Li2O in the lithium source = 1:2 (this ratio is the molar ratio of LiOH to Li2O, the same below). Put these into a mixer and stir for 30 min to mix uniformly to obtain a mixed raw material.

[0105] (2) Send the mixed raw material to a sintering furnace for calcination. Introduce high-purity nitrogen gas in advance, with the introduction amount of 5 m 3 / h, oxygen content less than 1 ppm, and humidity less than 5%. Then, heat the sintering furnace to 600 °C at a heating rate of 5 °C / min and hold for 36 h to obtain pure-phase Li5FeO4.

[0106] (3) Jet mill the sintered Li5FeO4 and maintain the dew point at -30 °C or lower to obtain pure-phase Li5FeO4 with a small particle size.

[0107] (4) 200 g of crushed Li5FeO4, 20 g of high-temperature coal pitch, and an appropriate amount of anhydrous ethanol were weighed, mixed uniformly, placed in a ball mill, and ball milling was performed for 3 hours at 450 rpm with a ball / material ratio of 10:1 to coat the Li5FeO4 with high-temperature coal pitch, thereby obtaining a Li5FeO4 precursor coated with high-temperature coal pitch.

[0108] (5) A Li5FeO4 precursor coated with high-temperature coal pitch is placed in a sintering furnace and calcined at high temperature, and high-purity nitrogen gas is introduced in advance, with an introduction volume of 5 m³. 3 The oxygen content was kept below 1 ppm and the humidity below 5% at a rate of 5°C / min in the sintering furnace, then the temperature was raised to 550°C, maintained for 2 hours, the product was jet-pulverized, and the dew point was kept below -30°C to obtain Li5FeO4@C, where the mass ratio of the carbon layer to the core Li5FeO4 is 6:100.

[0109] (6) Polyoxyethylene (molecular weight 100,000 Da) and LIFSI (lithium bis(fluorosulfonyl)imide) (polyoxyethylene monomer:LIFSI = 40:100 (this ratio is the mass ratio of polyoxyethylene monomer to lithium bis(fluorosulfonyl)imide, the same applies below)) were placed in anhydrous acetonitrile and stirred for 3 hours to completely dissolve and obtain a coating solution. Li5FeO4@C was placed in the coating solution (mass ratio of polyoxyethylene to Li5FeO4 is 1:100) and stirred until the acetonitrile was completely evaporated, and the product was jet-pulverized to obtain a lithium-rich lithium ferrite material (where the mass ratio of polyoxyethylene to Li5FeO4 is 1:100, the mass ratio of LIFSI to Li5FeO4 is 2.5:100, and the mass ratio of the second coating layer to Li5FeO4 is 3.5:100). SEM and XRD images are shown in Figures 4, 5, and 7.

[0110] Example 2 This embodiment provides a method for producing a lithium-rich lithium ferrite material, and differs from Example 1 only in that the carbon layer content is reduced until the mass ratio of the carbon layer to the core Li5FeO4 becomes 2:100.

[0111] Example 3 This embodiment provides a method for producing a lithium-rich lithium ferrite material, and differs from Example 1 only in that the carbon layer content is increased until the mass ratio of the carbon layer to the core Li5FeO4 becomes 8:100.

[0112] Example 4 This embodiment provides a method for producing a lithium-rich lithium ferrite material, and differs from Example 1 only in that the carbon layer content is increased until the mass ratio of the carbon layer to the core Li5FeO4 becomes 10:100.

[0113] Example 5 This embodiment provides a method for producing a lithium-rich lithium ferrite material, comprising the following steps.

[0114] (1) D90 weighed out 300 nm nano Fe2O3, Li2O, and LiOH, maintained Fe:Li = 1:5.1 and LiOH:Li2O = 1:2 in the lithium source, placed these in a mixer, stirred for 30 minutes to homogeneously mix, and obtained a mixed raw material.

[0115] (2) The mixed raw materials are sent to a sintering furnace and calcined, and high-purity nitrogen gas is introduced in advance, with an introduction volume of 5 m³. 3 The oxygen content was reduced to less than 1 ppm and the humidity to less than 5% per hour. Then, the sintering furnace was heated to 600°C at a heating rate of 5°C / min and maintained at this temperature for 36 hours to obtain the pure phase Li5FeO4.

[0116] (3) The sintered Li5FeO4 was jet-pulverized and the dew point was maintained below -30°C to obtain a pure phase of Li5FeO4 with small particle size.

[0117] (4) 200 g of pulverized Li5FeO4, 20 g of polypropylene, and an appropriate amount of anhydrous ethanol were weighed, mixed uniformly, placed in a ball mill, and ball milling was performed for 3 hours at 450 rpm with a ball / material ratio of 10:1 to coat the Li5FeO4 with polypropylene, thereby obtaining a polypropylene-coated Li5FeO4 precursor.

[0118] (5) A Li5FeO4 precursor coated with polypropylene is placed in a sintering furnace and calcined at a high temperature, and high-purity nitrogen gas is introduced in advance, with an introduction volume of 5 m³. 3 The oxygen content was reduced to less than 1 ppm and the humidity to less than 5% per hour. Then, the sintering furnace was heated to 400°C at a heating rate of 5°C / min, maintained at this temperature for 2 hours, the product was jet-pulverized, and the dew point was kept below -30°C to obtain Li5FeO4@C, where the mass ratio of the carbon layer to the core Li5FeO4 is 6:100.

[0119] (6) Polyoxyethylene (molecular weight 100,000 Da) and LIFSI (polyoxyethylene monomer: LIFSI = 40%) were placed in anhydrous acetonitrile and stirred for 3 hours to completely dissolve. Li5FeO4@C was added to the mixture and stirred until the acetonitrile was completely evaporated. The product was then jet-pulverized to obtain a lithium-rich lithium ferrite material (where the mass ratio of polyoxyethylene to Li5FeO4 is 1:100, the mass ratio of LIFSI to Li5FeO4 is 2.5:100, and the mass ratio of the second coating layer to Li5FeO4 is 3.5:100).

[0120] Example 6 This embodiment provides a method for producing a lithium-rich lithium ferrite material, and differs from Example 5 only in that the carbon layer content is reduced until the mass ratio of the carbon layer to the core Li5FeO4 becomes 2:100.

[0121] Example 7 This embodiment provides a method for producing a lithium-rich lithium ferrite material, and differs from Example 5 only in that the carbon layer content is increased until the mass ratio of the carbon layer to the core Li5FeO4 becomes 8:100.

[0122] Example 8 This embodiment provides a method for producing a lithium-rich lithium ferrite material, and differs from Example 5 only in that the carbon layer content is increased until the mass ratio of the carbon layer to the core Li5FeO4 becomes 10:100.

[0123] Example 9 This embodiment provides a method for producing a lithium-rich lithium ferrite material, comprising the following steps.

[0124] (1) D90 weighed out 300 nm nano Fe2O3, Li2O, and LiOH, maintained Fe:Li = 1:5.1 and LiOH:Li2O = 1:2 in the lithium source, placed these in a mixer, stirred for 30 minutes to homogeneously mix, and obtained a mixed raw material.

[0125] (2) The mixed raw materials are sent to a sintering furnace and calcined, and high-purity nitrogen gas is introduced in advance, with an introduction volume of 5 m³. 3 The oxygen content was reduced to less than 1 ppm and the humidity to less than 5% per hour. Then, the sintering furnace was heated to 600°C at a heating rate of 5°C / min and maintained at this temperature for 36 hours to obtain the pure phase Li5FeO4.

[0126] (3) The sintered Li5FeO4 was jet-pulverized and the dew point was maintained below -30°C to obtain a pure phase of Li5FeO4 with small particle size.

[0127] (4) 200 g of pulverized Li5FeO4, 60 g of glucose, and an appropriate amount of anhydrous ethanol were weighed, mixed uniformly, placed in a ball mill, and ball milling was performed for 3 hours at 450 rpm with a ball / material ratio of 10:1 to coat the Li5FeO4 with glucose, thereby obtaining a glucose-coated Li5FeO4 precursor.

[0128] (5) The glucose-coated Li5FeO4 precursor is placed in a sintering furnace and calcined at a high temperature, and high-purity nitrogen gas is introduced in advance, with an introduction volume of 5 m³. 3 The oxygen content was reduced to less than 1 ppm and the humidity to less than 5% per hour. Then, the sintering furnace was heated to 400°C at a heating rate of 5°C / min, maintained at this temperature for 2 hours, the product was jet-pulverized, and the dew point was kept below -30°C to obtain Li5FeO4@C, where the mass ratio of the carbon layer to the core Li5FeO4 is 6:100.

[0129] (6) An appropriate amount of polyoxyethylene (molecular weight 100,000 Da) and LIFSI (polyoxyethylene monomer: LIFSI = 40:100) were placed in anhydrous acetonitrile and stirred for 3 hours to completely dissolve. Li5FeO4@C was added to the mixture and stirred until the acetonitrile was completely evaporated. The product was then jet-pulverized to obtain a lithium-rich lithium ferrite material (the mass ratio of polyoxyethylene to Li5FeO4 was 1%, the mass ratio of LIFSI to Li5FeO4 was 2.5:100, and the mass ratio of the second coating layer to Li5FeO4 was 3.5:100).

[0130] Example 10 This embodiment provides a method for producing a lithium-rich lithium ferrite material, and differs from Example 9 only in that the carbon layer content is reduced until the mass ratio of the carbon layer to the core Li5FeO4 becomes 2:100.

[0131] Example 11 This embodiment provides a method for producing a lithium-rich lithium ferrite material, and differs from Example 9 only in that the carbon layer content is increased until the mass ratio of the carbon layer to the core Li5FeO4 becomes 8:100.

[0132] Example 12 This embodiment provides a method for producing a lithium-rich lithium ferrite material, and differs from Example 9 only in that the carbon layer content is increased until the mass ratio of the carbon layer to the core Li5FeO4 becomes 10:100.

[0133] Example 13 This embodiment provides a method for producing a lithium-rich lithium ferrite material, differing from Example 1 only in that the mass ratio of polyoxyethylene to Li5FeO4 is 0.5:100, the mass ratio of LIFSI to Li5FeO4 is 2.5:100, and the mass ratio of the second coating layer to Li5FeO4 is 3:100.

[0134] Example 14 This embodiment provides a method for producing a lithium-rich lithium ferrite material, differing from Example 1 only in that the mass ratio of polyoxyethylene to Li5FeO4 is 1:100, the mass ratio of LIFSI to Li5FeO4 is 2:100, and the mass ratio of the second coating layer to Li5FeO4 is 3:100.

[0135] Example 15 This embodiment provides a method for producing a lithium-rich lithium ferrite material, differing from Example 1 only in that the mass ratio of polyoxyethylene to Li5FeO4 is 2:100, the mass ratio of LIFSI to Li5FeO4 is 6:100, and the mass ratio of the second coating layer to Li5FeO4 is 8:100.

[0136] Example 16 This embodiment provides a method for producing a lithium-rich lithium ferrite material, differing from Example 1 only in that the mass ratio of polyoxyethylene to Li5FeO4 is 5:100, the mass ratio of LIFSI to Li5FeO4 is 8:100, and the mass ratio of the second coating layer to Li5FeO4 is 13:100.

[0137] Example 17 This embodiment provides a method for producing a lithium-rich lithium ferrite material, and differs from Example 1 in that in step (5), a Li5FeO4 precursor coated with high-temperature coal pitch is placed in a sintering furnace and calcined at a high temperature, the sintering furnace is heated to 500°C at a heating rate of 5°C / min and maintained for 2 hours, the product is jet-pulverized, the dew point is maintained below -30°C to obtain Li5FeO4@C, and finally, a lithium-rich lithium ferrite material is obtained.

[0138] Example 18 This embodiment provides a method for producing a lithium-rich lithium ferrite material, and differs from Example 1 in that in step (5), a Li5FeO4 precursor coated with high-temperature coal pitch is placed in a sintering furnace and calcined at a high temperature, the sintering furnace is heated to 700°C at a heating rate of 5°C / min and maintained for 2 hours, the product is jet-pulverized, the dew point is maintained below -30°C to obtain Li5FeO4@C, and finally, a lithium-rich lithium ferrite material is obtained.

[0139] Example 19 This embodiment provides a method for producing a lithium-rich lithium ferrite material, and differs from Example 1 in that in step (5), a Li5FeO4 precursor coated with high-temperature coal pitch is placed in a sintering furnace and calcined at a high temperature, the sintering furnace is heated to 450°C at a heating rate of 5°C / min and maintained for 2 hours, the product is jet-pulverized, the dew point is maintained below -30°C to obtain Li5FeO4@C, and finally, a lithium-rich lithium ferrite material is obtained.

[0140] Example 20 This embodiment provides a method for producing a lithium-rich lithium ferrite material, and differs from Example 1 in that in step (1), Fe:Li is maintained at 1:5.2 to obtain a mixed raw material, and finally, a lithium-rich lithium ferrite material is obtained.

[0141] Example 21 This embodiment provides a method for producing lithium-rich lithium ferrite material, and differs from Example 1 in that in step (1), Fe:Li = 1:5.0 is maintained to obtain a mixed raw material, and finally, a lithium-rich lithium ferrite material is obtained.

[0142] Example 22 This embodiment provides a method for producing a lithium-rich lithium ferrite material, and differs from Example 1 in that in step (1), Fe:Li is maintained at 1:5.3 to obtain a mixed raw material, and finally, a lithium-rich lithium ferrite material is obtained.

[0143] Example 23 This embodiment provides a method for producing a lithium-rich lithium ferrite material, and differs from Example 1 only in that in step (1), Fe:Li is maintained at 1:4.9 to obtain a mixed raw material, and finally, a lithium-rich lithium ferrite material is obtained.

[0144] Example 24 This embodiment provides a method for producing a lithium-rich lithium ferrite material, differing from Example 1 only in that in step (6), the polyoxyethylene monomer:LIFSI = 30:100, and finally, a lithium-rich lithium ferrite material is obtained.

[0145] Example 25 This embodiment provides a method for producing a lithium-rich lithium ferrite material, differing from Example 1 only in that in step (6), the polyoxyethylene monomer:LIFSI = 50:100, and finally, a lithium-rich lithium ferrite material is obtained.

[0146] Example 26 This embodiment provides a method for producing a lithium-rich lithium ferrite material, differing from Example 1 only in that in step (6), the polyoxyethylene monomer:LIFSI = 20:100, and finally, a lithium-rich lithium ferrite material is obtained.

[0147] Comparative Example 1 This comparative example provides a method for producing a lithium-rich lithium ferrite material, differing from Example 1 only in that it does not include step (6).

[0148] Comparative Example 2 This comparative example provides a method for producing a lithium-rich lithium ferrite material, differing from Example 1 only in that it does not include steps (4) and (5).

[0149] Comparative Example 3 This comparative example provides a method for producing a lithium-rich lithium ferrite material, and differs from Example 1 only in that the Fe2O3 in step (1) is replaced with iron hydroxide.

[0150] Comparative Example 4 This comparative example provides a method for producing a lithium-rich lithium ferrite material, and differs from Example 1 only in that the polyoxyethylene in step (1) is replaced with lithium titanium aluminum phosphate.

[0151] 2.Measurement method Particle size measurement: The particle size of the lithium-rich lithium ferrite materials produced in the examples and comparative examples was measured using a laser particle size analyzer, and the results are shown in Table 1.

[0152] Capacity measurement: Electrochemical properties of button half-cells: Lithium-rich lithium ferrite material produced in Examples and Comparative Examples, or the pure phase Li5FeO4 obtained in Example 2, was used as the positive electrode material. A slurry was prepared by mixing the above positive electrode material, conductive carbon black, and the adhesive PVDF (polyvinylidene fluoride) in an 8:1:1 ratio. This slurry was uniformly applied to aluminum foil to create a positive electrode plate (all manufacturing processes, including electrode material mixing and application, were performed in air). A metallic lithium sheet was used as the negative electrode plate, 1 mol / L LiPF6 as the electrolyte, and EC:DMC:EMC = 1:1:1 (volume ratio) as the solvent. The battery case, positive and negative electrode plates, separator (PE double-layer ceramic separator), dome, and gasket were assembled in a vacuum glove box to create a button cell. Electrochemical properties were measured, and the capacity was measured under conditions of 3.3~4.3V. The results are shown in Table 1 and Figure 6.

[0153] [Table 1]

[0154] 3. Analysis of measurement results for each example and comparative example Table 1 and Figure 6 show that in all of Examples 1 to 26, lithium-rich lithium ferrite materials with excellent capacity and small particle size were obtained, with Example 1 having the highest capacity. A comparison of Examples 1 to 4, Examples 5 to 8, and Examples 9 to 12 revealed that capacity decreases when the carbon layer content is too high or too low. A comparison of Example 1 with Examples 13 to 16 revealed that capacity decreases when the content of the second coating layer is too high or too low. Furthermore, a comparison of Example 1 with Examples 13 to 14 revealed that capacity also decreases when the ratio of polyoxyethylene to lithium salt in the second coating layer is unreasonable. A comparison of Examples 1, 5, and 9 showed that while normal carbon sources improve battery capacity, the capacity improvement effect is more pronounced in the case of high-temperature coal pitch.

[0155] From Table 1 and Figure 6, a comparison of Example 1 with Comparative Examples 1 and 2 revealed that when both the carbon layer and the second coating layer containing polyoxyethylene and lithium salt are coated, the capacity improvement is far greater than when the carbon layer is coated alone or when the second coating layer containing polyoxyethylene and lithium salt is coated alone. A comparison of Example 1 with Comparative Example 3 showed that using iron oxide as the carbon source is advantageous for obtaining a small-particle-size lithium-rich lithium ferrite material, while using iron hydroxide results in an increase in particle size and a significant decrease in capacity of the lithium-rich lithium ferrite. Examples of solid electrolytes stable in normal air include lithium titanium aluminum phosphate (LATP), lithium aluminum germanium phosphate (LAGP), and lithium lanthanum zirconium oxide (LLZO). A comparison of Example 1 with Comparative Example 4 showed that using a normal solid electrolyte in this application does not significantly improve battery capacity.

[0156] Furthermore, this application is not limited to the embodiments described above. The embodiments described above are merely illustrative, and any embodiment that has substantially the same configuration as the technical concept and exhibits the same effects within the scope of the technical solution of this application is included within the scope of this application. In addition, other forms obtained by adding various modifications to the embodiments that a person skilled in the art could conceive, or by combining some of the components of the embodiments, are also included within the scope of this application, as long as they do not depart from the spirit of this application. [Explanation of symbols]

[0157] The following symbols are used in the drawings shown below. 1 Li5FeO4 2. Carbon layer 3. Mixed layer containing polyoxyethylene and lithium salt

Claims

1. The material comprises core-shell structure particles, the core-shell structure particles comprising a core, a first coating layer covering the outside of the core, and a second coating layer covering the outside of the first coating layer. The aforementioned core is Li ５ FeO ４ The first coating layer is a carbon layer, and the second coating layer is a mixed layer containing polyoxyethylene and a lithium salt. A lithium-rich lithium ferrite material characterized in that the mass ratio of the first coating layer to the core is (2:100) to (10:100), and the mass ratio of the second coating layer to the core is (3:100) to (13:100).

2. The mass ratio of the polyoxyethylene to the core is (0.5:100) to (5:100), and the mass ratio of the lithium salt to the core is (2:100) to (8:100). Optionally, the mass ratio of the polyoxyethylene to the core is (0.5:100) to (2:100), the mass ratio of the lithium salt to the core is (2:100) to (4:100), and / or the mass ratio of the carbon layer to the core is (2:100) to (8:100). And / or, the mass ratio of the carbon layer to the core is (5:100) to (7:100), and / or, the lithium salt is at least one selected from lithium bis(fluorosulfonyl)imide, lithium hexafluoride phosphate, and lithium fluoride. The lithium-rich lithium ferrite material according to claim 1, characterized in that the molecular weight of the polyoxyethylene is 50,000 Da to 150,000 Da.

3. The D90 particle diameter of the core is 3 μm to 5.5 μm. and / or, the average thickness of the first coating layer is 5 nm to 10 nm. The lithium-rich lithium ferrite material according to claim 1 or 2, characterized in that the average thickness of the second coating layer is 5 nm to 10 nm.

4. The steps include providing the core and the coating liquid, The steps include forming a first coating layer on the surface of the core to obtain an intermediate product, The step of mixing the intermediate product with the coating solution to form a second coating layer on the surface of the first coating layer to obtain the lithium-rich lithium ferrite material includes the step of The method for producing a lithium-rich lithium ferrite material according to any one of claims 1 to 3, characterized in that the coating solution comprises a solvent, polyoxyethylene, and a lithium salt.

5. The step of forming the first coating layer on the surface of the core includes mixing the core with a carbon source and a grinding aid, ball milling, and then carbonizing it to obtain the intermediate product. The carbon source is optionally selected from polypropylene, glucose, and high-temperature coal pitch. The manufacturing method according to claim 4, characterized in that, optionally, the carbonization treatment is performed at a temperature of 500°C to 700°C and for a time of 1.5 hours to 3 hours.

6. The manufacturing method further includes the step of manufacturing the core, which is to form the first coating layer on the surface of the core and obtain an intermediate product, The process includes a step of calcining a first mixture of an iron source and a lithium source in an inert atmosphere at 500°C to 700°C for 24 to 48 hours. Optionally, the iron source is Fe ２ O ３ And, Optionally, the D90 particle size of the iron source is 400 nm or less. And / or, the D90 particle size of the iron source is 200 nm to 400 nm. The lithium source is optionally selected from lithium oxide, lithium hydroxide, and lithium carbonate, Optionally, the lithium source is a second mixture of lithium oxide and lithium hydroxide. Optionally, the lithium source is the second mixture obtained by mixing lithium oxide and lithium hydroxide in a molar ratio of (1.5:1) to (2.5:1). The manufacturing method according to claim 4 or 5, characterized in that, optionally, the molar ratio of Fe to Li in the first mixture is (1:5.0) to (1:5.2).

7. The manufacturing method according to any one of claims 4 to 6, characterized in that after mixing the intermediate product with the coating solution, the solvent is removed, the mixture is pulverized and sieved, a second coating layer is formed on the surface of the first coating layer, and the lithium-rich lithium ferrite material is obtained.

8. The manufacturing method according to any one of claims 4 to 7, characterized in that, in the coating liquid, the mass ratio of the polyoxyethylene to the lithium salt is (20 to 50):100, preferably (30 to 40):

100.

9. The current collector and the active material layer provided on at least one side of the current collector, wherein the active material layer includes the lithium-rich lithium ferrite material described in any one of claims 1 to 3 or the lithium-rich lithium ferrite material manufactured by the manufacturing method described in any one of claims 4 to 8. A positive electrode plate characterized in that, optionally, the mass fraction of the lithium-rich lithium ferrite material in the active material layer is 2 wt% to 8 wt%.

10. A secondary battery characterized by including the positive electrode plate described in claim 9.

11. A power consumption device characterized by including the secondary battery described in claim 10.

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