Lithium-rich metal oxide and preparation method thereof, positive plate, battery monomer and battery

Abstract

The invention provides a lithium-rich metal oxide and a preparation method thereof, a positive plate, a battery monomer and a battery. A lithium-rich metal oxide including a lithium-rich metal oxide core; the coating layer comprises an organic matter layer and a carbonaceous material, the lithium-rich metal oxide core is coated with the organic matter layer, and at least part of the carbonaceous material is embedded into the organic matter layer. The lithium-rich metal oxide disclosed by the invention has relatively high stability and conductivity, and is beneficial to improving the performance of the battery monomer.

Description

Lithium-rich metal oxide and preparation method thereof, positive electrode sheet, battery cell and battery Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a lithium-rich metal oxide and a preparation method thereof, a positive electrode sheet, a battery cell and a battery. Background Art

[0002] With the increasing severity of environmental pollution, the new energy industry has attracted more and more attention. In the new energy industry, battery technology is an important factor in its development.

[0003] Lithium-rich metal oxides, as materials for the positive electrode sheets of battery cells, are crucial to their performance. Therefore, developing a lithium-rich metal oxide that balances stability and conductivity to improve battery performance is a pressing technical challenge.

[0004] Summary of the Invention

[0005] The present application is made in view of the above-mentioned problems, and its purpose is to provide a lithium-rich metal oxide that takes into account both stability and conductivity to improve the performance of battery cells.

[0006] In order to achieve the above-mentioned objectives, the present application provides a lithium-rich metal oxide and a preparation method thereof, a positive electrode sheet, a battery cell and a battery.

[0007] In a first aspect, the present application provides a lithium-rich metal oxide, comprising a lithium-rich metal oxide core; a coating layer, wherein the coating layer comprises an organic layer and a carbonaceous material, the organic layer coating the lithium-rich metal oxide core, and at least a portion of the carbonaceous material is embedded in the organic layer.

[0008] The present application provides a lithium-rich metal oxide, comprising a lithium-rich metal oxide core and a coating layer, the coating layer comprising an organic layer and a carbonaceous material, the organic layer coating the lithium-rich metal oxide core, and the carbonaceous material being embedded in the organic layer. The lithium ion content in the lithium-rich metal oxide core is higher than that of general lithium-containing metal oxides. Selecting the lithium-rich metal oxide core to prepare the positive electrode material is beneficial to improving the charging capacity of the battery cell. The organic layer coating the lithium-rich metal oxide core can reduce the risk of the lithium-rich metal oxide core reacting with water, carbon dioxide, etc. in the air, thereby reducing the impact of byproducts generated on the surface of the lithium-rich metal oxide core on the processing of the positive electrode sheet, and reducing the impact of byproducts on the release of lithium ions from the lithium-rich metal oxide core, thereby reducing the impact on the charging capacity of the battery cell. In addition, the embedding of the carbonaceous material in the organic layer is beneficial to improving the conductivity of the lithium-rich metal oxide. Therefore, the lithium-rich metal oxide of the present application has high stability and conductivity. When the lithium-rich metal oxide of the present application is applied to a battery cell, it is beneficial to improve the performance of the battery cell.

[0009] In one possible implementation, at least a portion of the carbonaceous material penetrates the organic layer. This, on the one hand, further improves the conductivity of the lithium-rich metal oxide; on the other hand, the carbonaceous material can serve as a channel for ion transmission, thereby improving the diffusion coefficient of ions, such as lithium ions.

[0010] In a possible implementation, the carbonaceous material includes a simple carbon material; optionally, the simple carbon material includes a one-dimensional carbon material; optionally, the one-dimensional carbon material includes a carbon nanotube.

[0011] In the above scheme, the carbonaceous material includes a single carbon material, so that the effect of the decomposition of the carbonaceous material during the coating process of the lithium-rich metal oxide on the conductivity of the lithium-rich metal oxide can be reduced. The single carbon material includes a one-dimensional carbon material, which is conducive to the embedding or penetration of the carbonaceous material in the organic layer. The one-dimensional carbon material includes carbon nanotubes. Due to the high conductivity of carbon nanotubes, it is conducive to improving the electronic conductivity of the lithium-rich metal oxide; in addition, the hollow tubes inside the carbon nanotubes can accommodate electrolytes, and the electrolyte can contact the lithium-rich metal oxide core through the hollow tubes. The hollow tubes can also serve as ion channels to transport lithium ions. Therefore, by selecting carbon nanotubes as carbonaceous materials, it is beneficial to further improve the conductivity of lithium-rich metal oxides.

[0012] In a possible implementation, the carbon nanotubes include one or more of single-walled carbon nanotubes and multi-walled carbon nanotubes, so that different types of carbon nanotubes can be flexibly selected according to actual conditions.

[0013] In one possible implementation, the aspect ratio of the carbon nanotubes is 100:1 to 1000:1, and can be optionally 200:1 to 400:1. If the aspect ratio of the carbon nanotubes is too large, the carbon nanotubes are prone to agglomeration. In this way, the dispersion of the carbon nanotubes is poor during the coating process of the lithium-rich metal oxide core, which is not conducive to the carbon nanotubes uniformly coating the lithium-rich metal oxide core. The aspect ratio of the carbon nanotubes is too small, which affects the transmission effect of the carbon nanotubes on electrons and ions. By setting the aspect ratio of the carbon nanotubes to an appropriate range, both the coating effect on the lithium-rich metal oxide core and the conductivity of the lithium-rich metal oxide can be taken into account.

[0014] In one possible implementation, the mass ratio of the carbon nanotubes to the lithium-rich metal oxide is 0.2% to 2%, and can be optionally 0.5% to 1.5%. If the carbon nanotube content is too high, agglomerates will form during the mixing process, which is not conducive to achieving uniform coating and affects the stability of the lithium-rich metal oxide. If the carbon nanotube content is too low, the conductivity of the lithium-rich metal oxide decreases, and the transmission and diffusion paths of lithium ions are reduced, affecting the charging capacity of the battery cell prepared from the lithium-rich metal oxide. By reasonably setting the proportion of carbon nanotubes in the lithium-rich metal oxide, it is beneficial to balance the stability and conductivity of the lithium-rich metal oxide, as well as the charging capacity of the battery cell.

[0015] In one possible implementation, the softening temperature of the organic layer does not exceed 450° C., and optionally, does not exceed 300° C. After softening, the organic material becomes fluid and can uniformly coat the lithium-rich metal oxide core over a large area. By selecting an organic material with a lower softening temperature, uniform and dense coating of the lithium-rich metal oxide core can be achieved at a lower temperature.

[0016] In one possible implementation, the median particle size Dv of the lithium-rich metal oxide is 50 The median particle size of the lithium-rich metal oxide is 2μm to 10μm, and can be 4μm to 8μm. If the median particle size of the lithium-rich metal oxide is too large, the path for lithium ions to escape from the lithium-rich metal oxide core is too long, which is not conducive to the escape of lithium ions and affects the charging capacity of the battery cell prepared by the lithium-rich metal oxide; if the median particle size of the lithium-rich metal oxide is too small, the surface activity of the lithium-rich metal oxide is strong, and the lithium-rich metal oxide particles or lithium-rich metal oxide core particles are easy to agglomerate, and the particle dispersion is poor, which is not conducive to achieving coating uniformity. By reasonably setting the median particle size of the lithium-rich metal oxide, the uniformity of the lithium-rich metal oxide coating and the charging capacity of the battery cell can be taken into account.

[0017] In one possible implementation, the mass ratio of the coating layer to the lithium-rich metal oxide is 1% to 10%, optionally 3% to 7%. A coating layer with too high a content will inhibit the release of lithium ions, affecting the charge capacity of the battery cell. A coating layer with too low a content will not be conducive to forming a uniform and complete coating on the surface of the lithium-rich metal oxide core, resulting in poor coating effect, poor stability of the lithium-rich metal oxide, and also affecting the charge capacity of the battery cell.

[0018] In one possible implementation, the material of the lithium-rich metal oxide core includes Li a M n O y , 2≤a≤8, the Li a M n O y Including Li2M 1 O2、Li2M 2 O3、Li3M 3 O4、Li5M 4 O4、Li6M 5 O4、Li8M 6 One or more of O6; M 1 Including one or more of Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Mo; M 2 Including one or more of Mn, Sn, Mo, Ru, Ir; M 3 Including one or more of V, Nb, Cr, Mo; M 4 Including one or more of Fe, Cr, V, Mo; M 5 Including one or more of Co, V, Cr, Mo; M 6 Including Sn; optionally, the Li a M n O y The lithium-rich metal oxide core may include one or more of Li2NiO2, Li2CuO2, Li2MnO3, Li3VO4, Li3NbO4, Li5FeO4, Li6CoO4, and Li8SnO6. In this way, it is convenient to flexibly select a suitable lithium-rich metal oxide core according to actual needs.

[0019] In one possible implementation, the material of the organic layer includes one or more of rubber, asphalt, polypropylene, polyethylene, polystyrene, polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polyvinylidene fluoride, and polytetrafluoroethylene. Alternatively, the material of the organic layer includes one or more of rubber, asphalt, and polyvinylidene fluoride. This allows for flexible selection of the material of the organic layer based on actual needs.

[0020] In a second aspect, the present application provides a method for preparing a lithium-rich metal oxide, comprising: providing a lithium-rich metal oxide core, a carbonaceous material, and an organic matter; mixing the lithium-rich metal oxide core, the carbonaceous material, and the organic matter, and treating the mixture to obtain the lithium-rich metal oxide. The lithium-rich metal oxide prepared by this method has high conductivity and stability. When the lithium-rich metal oxide of the present application is applied to a battery cell, it is beneficial to improve the performance of the battery cell.

[0021] In one possible implementation, the treatment includes: sintering in an inert atmosphere for 2 hours to 6 hours. In this way, it is easy to obtain a lithium-rich metal oxide with a uniform coating. Optionally, the inert atmosphere includes one or more of nitrogen, argon and helium. In this way, it is convenient to select a suitable inert gas according to actual needs. Optionally, the temperature of the treatment does not exceed 500°C, and optionally, the temperature of the sintering does not exceed 300°C. In this way, a lithium-rich metal oxide with a uniform and dense coating layer can be achieved at a lower temperature.

[0022] In a possible implementation, the method further includes: screening the product after the treatment to obtain the lithium-rich metal oxide, so as to facilitate obtaining the lithium-rich metal oxide with a suitable particle size.

[0023] In one possible implementation, the carbonaceous material includes an elemental carbon material; optionally, the elemental carbon material includes a one-dimensional carbon material; optionally, the one-dimensional carbon material includes carbon nanotubes. In this way, the effect of the decomposition of the carbonaceous material during the preparation of the lithium-rich metal oxide on the conductivity of the lithium-rich metal oxide can be reduced. The elemental carbon material includes a one-dimensional carbon material, which is conducive to the embedding or penetration of the carbonaceous material in the organic layer. The one-dimensional carbon material includes carbon nanotubes. Due to the high conductivity of carbon nanotubes, it is beneficial to improve the electronic conductivity of the lithium-rich metal oxide; in addition, the hollow tubes inside the carbon nanotubes can accommodate electrolytes, and the electrolyte can contact the lithium-rich metal oxide core through the hollow tubes. The hollow tubes can also serve as ion channels to transport lithium ions. Therefore, by selecting carbon nanotubes as carbonaceous materials, it is beneficial to further improve the conductivity of lithium-rich metal oxides.

[0024] In a possible implementation, the carbon nanotubes include one or more of single-walled carbon nanotubes and multi-walled carbon nanotubes, so that different types of carbon nanotubes can be flexibly selected according to actual conditions.

[0025] In one possible implementation, the aspect ratio of the carbon nanotubes is 100:1 to 1000:1, and can be optionally 200:1 to 400:1. This allows for both the coating effect on the lithium-rich metal oxide core and the conductivity of the lithium-rich metal oxide to be achieved.

[0026] In one possible implementation, the softening temperature of the organic material is lower than the treatment temperature. Optionally, the softening temperature of the organic material does not exceed 450° C., and optionally, does not exceed 300° C. In this way, the organic material softens at the sintering temperature, thereby forming a fluid state, facilitating uniform and dense coating of the lithium-rich metal oxide core.

[0027] In one possible implementation, the organic material includes one or more of rubber, asphalt, polypropylene, polyethylene, polystyrene, polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polyvinylidene fluoride, and polytetrafluoroethylene. Alternatively, the organic material includes one or more of rubber, asphalt, and polyvinylidene fluoride. This allows for flexible selection of the organic material based on actual needs.

[0028] In one possible implementation, providing a lithium-rich metal oxide core comprises: uniformly mixing a Li source and a Mn source in a molar ratio of (a+0.05):1 to a:1, and then performing a single temperature sintering in an inert atmosphere for 4 to 8 hours, wherein the sintering temperature is 400°C to 600°C; wherein the Li source comprises one or more of lithium oxide, lithium carbonate, lithium oxalate, lithium acetate, and lithium hydroxide, and the Mn source comprises one or more of Mn oxide, hydroxide, halide, sulfate, carbonate, nitrate, oxalate, acetate, sulfide, and nitride; optionally, the sintering temperature is 450°C to 550°C; optionally, the inert atmosphere comprises one or more of nitrogen, argon, and helium; and the product of the single temperature sintering is subjected to air flow crushing to obtain the lithium-rich metal oxide core. In this way, a suitable lithium-rich metal oxide core is easily prepared, which facilitates the subsequent preparation of lithium-rich metal oxides.

[0029] In a third aspect, a positive electrode sheet is provided, comprising the lithium-rich metal oxide in the first aspect and any possible implementation thereof.

[0030] In a fourth aspect, a battery cell is provided, comprising the positive electrode sheet described in the third aspect.

[0031] In a fifth aspect, a battery is provided, comprising the battery cell described in the fourth aspect.

[0032] In a sixth aspect, an electrical device is provided, comprising the battery described in the fifth aspect.

[0033] The present application provides a lithium-rich metal oxide, comprising a lithium-rich metal oxide core and a coating layer, the coating layer comprising an organic layer and a carbonaceous material, the organic layer coating the lithium-rich metal oxide core, and the carbonaceous material being embedded in the organic layer. The lithium ion content in the lithium-rich metal oxide core is higher than that of general lithium-containing metal oxides. Selecting the lithium-rich metal oxide core to prepare the positive electrode material is beneficial to improving the charging capacity of the battery cell. The organic layer coating the lithium-rich metal oxide core can reduce the risk of the lithium-rich metal oxide core reacting with water, carbon dioxide, etc. in the air, thereby reducing the impact of byproducts generated on the surface of the lithium-rich metal oxide core on the processing of the positive electrode sheet, and reducing the impact of byproducts on the release of lithium ions from the lithium-rich metal oxide core, thereby reducing the impact on the charging capacity of the battery cell. In addition, the embedding of the carbonaceous material in the organic layer is beneficial to improving the conductivity of the lithium-rich metal oxide. Therefore, the lithium-rich metal oxide of the present application has high stability and conductivity. When the lithium-rich metal oxide of the present application is applied to a battery cell, it is beneficial to improve the performance of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG1 is a schematic diagram of a lithium-rich metal oxide according to an embodiment of the present application;

[0035] FIG2 is a flow chart of a method for preparing a lithium-rich metal oxide according to an embodiment of the present application;

[0036] FIG3 is a schematic diagram of a battery cell according to an embodiment of the present application;

[0037] FIG4 is a schematic diagram of a battery module according to an embodiment of the present application;

[0038] FIG5 is a schematic diagram of a battery according to an embodiment of the present application;

[0039] FIG6 is a schematic diagram of an electrical device according to an embodiment of the present application;

[0040] FIG7 is a schematic diagram of a scanning electron microscope image of a lithium-rich metal oxide without a coating layer;

[0041] FIG8 is a schematic diagram of a scanning electron microscope image of a lithium-rich metal oxide with a coating layer in the present application. DETAILED DESCRIPTION

[0042] Below, the embodiments of the negative electrode sheet, secondary battery, battery module, battery pack and electric device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0043] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0044] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0045] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0046] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0047] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0048] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0049] Lithium-ion batteries are widely used in mobile phones, electric vehicles, power stations and other fields due to their high energy density, high voltage and long life. The lithium-rich metal oxides in lithium-ion batteries are crucial to the performance of lithium-ion batteries, such as capacity and

[0050] Lithium-rich metal oxides have a high lithium ion content and are widely used in the preparation of lithium-ion batteries. Lithium-rich metal oxides have poor stability. In the prior art, in order to improve the performance of lithium-rich metal oxides, carbon or polymers are usually used to coat lithium-rich metal oxides to improve the conductivity or stability of lithium-rich metal oxides. However, the applicant has found through research that this method of coating lithium-rich metal oxides with only a single carbon source often makes it difficult to balance stability and conductivity, which is not conducive to improving the overall performance of lithium-rich metal oxides, nor is it conducive to improving the performance of lithium-ion batteries.

[0051] In view of this, the present application provides a lithium-rich metal oxide, in which the coating layer includes organic matter and carbonaceous materials, which can take into account the stability and conductivity of the lithium-rich metal oxide, and is conducive to improving the performance of the battery cell.

[0052] [Lithium-rich metal oxides]

[0053] FIG1 is a schematic diagram of a lithium-rich metal oxide according to an embodiment of the present application. As shown in FIG1 , the lithium-rich metal oxide 1 includes a lithium-rich metal oxide core 11 and a coating layer 12 .

[0054] The lithium ion content in the lithium-rich metal oxide core 11 is higher than that in general lithium-containing metal oxides. Selecting the lithium-rich metal oxide core 11 to prepare a battery cell is beneficial to improving the charging capacity of the battery cell.

[0055] The coating layer 12 coats the lithium-rich metal oxide core 11 . That is, the lithium-rich metal oxide core 11 , as the core of the lithium-rich metal oxide 1 , is coated inside the coating layer 12 .

[0056] The coating layer 12 includes an organic layer 121 and a carbonaceous material 122 . The organic layer 121 covers the lithium-rich metal oxide core 11 , and at least a portion of the carbonaceous material 122 is embedded in the organic layer 121 .

[0057] The organic layer 121 is a material layer formed of organic matter, and the organic layer 121 covers the outer surface of the lithium-rich metal oxide core 11 .

[0058] The lithium-rich metal oxide core 11 easily reacts with water, carbon dioxide, etc. in the air, thereby generating by-products on the surface of the lithium-rich metal oxide core 11, such as lithium-containing inert compounds such as Li2CO3 and LiOH. These by-products or lithium-containing inert compounds are free on the surface of the lithium-rich metal oxide core 11, affecting the release of lithium ions from the lithium-rich metal oxide core 11, resulting in a decrease in the performance of the lithium-rich metal oxide and the charging capacity of the battery cell. In addition, the lithium-containing inert compounds are highly alkaline. When the lithium-rich metal oxide core 11 is mixed with a binder to form a slurry to prepare a positive electrode sheet, these inert compounds will affect the performance of the binder, causing the binder, such as polyvinylidene fluoride (PVDF), to denature, affecting the performance of the slurry and the coating of the slurry, thereby affecting the processing of the positive electrode sheet.

[0059] By using an organic layer 121 to coat the lithium-rich metal oxide core 11, the risk of side reactions in the lithium-rich metal oxide core 11 can be reduced, which is beneficial to improving the stability of the lithium-rich metal oxide 1; the influence of lithium-containing inert compounds on the processing of the positive electrode sheet can be reduced, and the influence of by-products on the charging capacity of the battery cell and the performance of the lithium-rich metal oxide can be reduced, which is beneficial to improving the performance of the lithium-rich metal oxide and the charging capacity of the battery cell.

[0060] Optionally, the charge capacity of a battery cell may include the initial charge capacity of the battery cell, during which lithium ions are released from the positive electrode sheet during the charging process of the battery cell. For example, the charge capacity of a battery cell may be the ratio of the capacity of the battery cell to the mass of the active material in the battery cell after the battery cell is fully charged.

[0061] The carbonaceous material 122 includes a carbonaceous material having electrical conductivity and may include a single carbon material.

[0062] At least a portion of the carbonaceous material 122 in the coating layer 12 is embedded in the organic layer 121 . For example, the coating layer 12 includes a plurality of carbonaceous material particles, and at least one carbonaceous material particle is embedded in the organic layer 121 .

[0063] Embedding may include: a portion of the carbonaceous material particles being embedded in the organic layer 121 , the carbonaceous material particles being adsorbed on the organic layer 121 , or all of the carbonaceous material particles being embedded in the organic layer 121 .

[0064] By arranging the carbonaceous material 122 to be embedded in the organic layer 121 , the conductive performance of the organic layer 121 is improved, that is, the resistivity of the lithium-rich metal oxide 1 is reduced and the conductivity of the lithium-rich metal oxide 1 is improved.

[0065] Alternatively, the lithium-rich metal oxide 1 of the present application can be used as a lithium supplement. Alternatively, the lithium-rich metal oxide of the present application can also be used as an active agent, and after being mixed with a binder and a conductive agent, a positive electrode sheet can be prepared.

[0066] The present application provides a lithium-rich metal oxide 1, comprising a lithium-rich metal oxide core 11 and a coating layer 12, wherein the coating layer 12 comprises an organic layer 121 and a carbonaceous material 122, wherein the organic layer 121 coats the lithium-rich metal oxide core 11, and the carbonaceous material 122 is embedded in the organic layer 121. The lithium ion content in the lithium-rich metal oxide core 11 is higher than that of general lithium-containing metal oxides. Selecting the lithium-rich metal oxide core 11 to prepare a positive electrode material is beneficial for improving the charge capacity of a battery cell. The organic layer 121 coating the lithium-rich metal oxide core 11 can reduce the risk of the lithium-rich metal oxide core 11 reacting with water, carbon dioxide, etc. in the air, thereby reducing the impact of byproducts generated on the surface of the lithium-rich metal oxide core 11 on the processing of the positive electrode sheet, and reducing the impact of byproducts on the release of lithium ions from the lithium-rich metal oxide core 11, thereby reducing the impact on the charge capacity of the battery cell. In addition, the embedding of the carbonaceous material 122 in the organic layer 121 is beneficial for improving the conductivity of the lithium-rich metal oxide 1. Therefore, the lithium-rich metal oxide 1 of the present application has high stability and conductivity. When the lithium-rich metal oxide 1 of the present application is applied to a battery cell, it is beneficial to improve the performance of the battery cell.

[0067] In some embodiments, at least a portion of the carbonaceous material 122 penetrates the organic layer 121. Alternatively, the carbonaceous material 122 is embedded in the organic layer 121 and extends from the surface of the organic layer 121 near the lithium-rich metal oxide core 11 to the surface of the organic layer 121 away from the lithium-rich metal oxide core 11. Thus, the carbonaceous material 122 is in contact with both the lithium-rich metal oxide core 11 and the exterior of the lithium-rich metal oxide 11, such as the electrolyte.

[0068] Optionally, at least a portion of the carbonaceous material 122 penetrates the organic layer 121 and extends to the surface of the organic layer 121 away from the lithium-rich metal oxide core 11. In this way, the carbonaceous material 122 can contact the external environment, such as the electrolyte, and can be used to transport lithium ions.

[0069] In the above embodiment, at least part of the carbonaceous material 122 penetrates the organic layer 121. This, on the one hand, is beneficial to further improve the conductivity of the lithium-rich metal oxide 1; on the other hand, the carbonaceous material 122 can serve as a channel for transmitting ions, which is beneficial to improve the diffusion coefficient of ions, such as lithium ions.

[0070] In some embodiments, the carbonaceous material 122 includes a single carbon material, so as to reduce the effect of the carbonaceous material 122 decomposing during the coating process on the conductivity of the lithium-rich metal oxide 1 .

[0071] Elemental carbon materials can include zero-dimensional carbon materials, one-dimensional carbon materials, and two-dimensional carbon materials. Zero-dimensional carbon materials can include carbon black, fullerene C60, etc. One-dimensional carbon materials can include carbon nanotubes with internal hollow structures and carbon nanofibers without obvious internal hollow structures. Two-dimensional carbon materials can include graphene, etc.

[0072] Optionally, in some embodiments, the elemental carbon material 122 includes a one-dimensional carbon material, which is conducive to embedding or penetrating the carbon material into the organic layer 121 .

[0073] Optionally, in some embodiments, the one-dimensional carbon material includes carbon nanotubes.

[0074] Carbon nanotubes have high electrical conductivity, and their inclusion in coating layer 12 helps improve the electronic conductivity of lithium-rich metal oxide 1. Furthermore, the hollow tubes within the carbon nanotubes can accommodate electrolyte, which can then contact lithium-rich metal oxide core 11 through the hollow tubes. The hollow tubes also serve as ion channels for lithium ion transport. Therefore, selecting carbon nanotubes as carbonaceous material 122 further improves the electrical conductivity of lithium-rich metal oxide 1.

[0075] In some embodiments, the carbon nanotubes include single-walled carbon nanotubes, multi-walled carbon nanotubes, or more thereof, so that different types of carbon nanotubes can be flexibly selected according to actual conditions.

[0076] In some embodiments, the aspect ratio of the carbon nanotubes is 100:1 to 1000:1, and can be optionally 200:1 to 400:1.

[0077] The aspect ratio of a carbon nanotube is the ratio of the length of the carbon nanotube to its outer diameter.

[0078] When the aspect ratio of the carbon nanotubes is greater than 1000:1, the carbon nanotubes are long and easily aggregated, which results in poor dispersion of the carbon nanotubes during coating of the lithium-rich metal oxide core 11, hindering uniform coating of the lithium-rich metal oxide core 11 by the carbon nanotubes.

[0079] When the aspect ratio of the carbon nanotube is less than 100:1, the length of the carbon nanotube is small and the hollow tube of the carbon nanotube is short, which affects the transmission effect of the carbon nanotube on electrons and ions.

[0080] In this embodiment, by setting the aspect ratio of the carbon nanotubes to 100:1 to 1000:1, both the coating effect on the lithium-rich metal oxide core 11 and the conductivity of the lithium-rich metal oxide 1 can be taken into consideration.

[0081] Optionally, by setting the aspect ratio of the carbon nanotubes to 200:1 to 400:1, it is beneficial to further improve the coating effect on the lithium-rich metal oxide core 11 and the conductivity of the lithium-rich metal oxide 1.

[0082] In some embodiments, the mass ratio of carbon nanotubes to lithium-rich metal oxide 1 is 0.2% to 2%, and can be optionally 0.5% to 1.5%.

[0083] When the mass ratio of carbon nanotubes to lithium-rich metal oxide 1 is greater than 2%, the carbon nanotubes will form agglomerates during the process of mixing the carbon nanotubes, or mixing the carbon nanotubes with organic matter and the lithium-rich metal oxide core 11, which is not conducive to achieving uniform coating and affects the coating effect and the stability of the lithium-rich metal oxide 1.

[0084] When the mass ratio of carbon nanotubes to lithium-rich metal oxide is less than 0.2%, the content of carbon nanotubes is too small, the conductivity of the lithium-rich metal oxide 1 decreases, and the transmission path and diffusion path of lithium ions are reduced, which affects the performance of the lithium-rich metal oxide 1 and the charging capacity of the prepared battery cell.

[0085] In this embodiment, by setting the mass ratio of carbon nanotubes to lithium-rich metal oxide 1 to 0.2% to 2%, it is beneficial to take into account the stability and conductivity of the lithium-rich metal oxide 1 and the charging capacity of the battery cell.

[0086] Optionally, the mass ratio of carbon nanotubes to lithium-rich metal oxide 1 is 0.5% to 1.5%, which is beneficial to further improve the stability and conductivity of lithium-rich metal oxide 1 and the charging capacity of the battery cell.

[0087] In some embodiments, the softening temperature of the organic layer 121 is no more than 450°C, and optionally, no more than 300°C.

[0088] The softening temperature can be the temperature at which the organic matter changes from a solid state to a fluid state, or the temperature at which the organic matter changes from a solid state to a molten state. After reaching the softening temperature of the organic matter, the organic matter becomes a fluid state or a molten state.

[0089] After softening, the organic material melts and becomes fluid, which can evenly coat the lithium-rich metal oxide core 11 over a large area, thereby forming an organic layer 121. By selecting an organic material with a lower softening temperature, the lithium-rich metal oxide core 11 can be evenly and densely coated at a lower temperature.

[0090] In some embodiments, the median particle size Dv of the lithium-rich metal oxide 1 is 50 It is 2μm~10μm, and can be optionally 4μm~8μm.

[0091] Median particle size Dv 50 It can refer to the particle size corresponding to when the cumulative volume distribution percentage of a sample reaches 50%.

[0092] Median particle size Dv of lithium-rich metal oxide 1 50 The larger the median particle size of the lithium-rich metal oxide core 11, the larger the median particle size Dv of the lithium-rich metal oxide core 11. 50 The larger the lithium-rich metal oxide core 11, the smaller the median particle size, the lithium-rich metal oxide 1 median particle size Dv 50 The smaller.

[0093] The median particle size Dv of the lithium-rich metal oxide 1 50 When the diameter is greater than 10 μm, the path for lithium ions to escape from the lithium-rich metal oxide core 11 is too long, which is not conducive to the escape of lithium ions and affects the performance of the lithium-rich metal oxide 1 and the capacity of the prepared battery cell.

[0094] The median particle size Dv of the lithium-rich metal oxide 1 50When the particle size is less than 2 μm, the surface activity of the lithium-rich metal oxide 1 is relatively strong, the lithium-rich metal oxide particles or the lithium-rich metal oxide core particles are easily agglomerated, and the particle dispersion is relatively poor, which is not conducive to achieving coating uniformity.

[0095] In this embodiment, by setting the median particle size Dv of the lithium-rich metal oxide 1 50 The thickness is 2 μm to 10 μm, which can take into account both the uniformity of the coating of the lithium-rich metal oxide 1 and the capacity of the battery cell prepared by the lithium-rich metal oxide.

[0096] Optionally, the median particle size Dv of the lithium-rich metal oxide 1 is 50 The thickness of the lithium-rich metal oxide 1 is 4 μm to 8 μm, which is beneficial to further improve the coating uniformity of the lithium-rich metal oxide 1 and the capacity of the battery cell.

[0097] In some embodiments, the mass ratio of the coating layer 12 to the lithium-rich metal oxide 1 is 1% to 10%, and can be optionally 3% to 7%.

[0098] When the mass ratio of the lithium-rich metal oxide 1 in the coating layer 12 is greater than 10%, the excessively high content of the coating layer 12 will inhibit the release of lithium ions and affect the charging capacity of the battery cell.

[0099] When the mass ratio of the lithium-rich metal oxide 1 in the coating layer 12 is less than 1%, the content of the coating layer 12 is too low, which is not conducive to forming a uniform and complete coating on the surface of the lithium-rich metal oxide core 11. The coating effect is poor, the stability of the lithium-rich metal oxide 1 is poor, and the charging capacity of the battery cell is affected.

[0100] In this embodiment, by setting the mass ratio of the coating layer 12 to the lithium-rich metal oxide 1 to 1% to 10%, both the stability of the lithium-rich metal oxide 1 and the capacity of the prepared battery cell can be taken into consideration.

[0101] Optionally, the mass ratio of the coating layer 12 to the lithium-rich metal oxide 1 is 3% to 7%, which is beneficial to further improve the stability of the lithium-rich metal oxide 1 and the capacity of the prepared battery cell.

[0102] In some embodiments, the material of the lithium-rich metal oxide core 11 includes Li a M n O y , 2≤a≤8,Li a M n O y Including Li2M 1 O2、Li2M 2 O3、Li3M 3 O4、Li5M 4 O4、Li6M 5O4、Li8M 6 One or more of O6; M 1 Including one or more of Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Mo; M 2 Including one or more of Mn, Sn, Mo, Ru, Ir; M 3 Including one or more of V, Nb, Cr, Mo; M 4 Including one or more of Fe, Cr, V, Mo; M 5 Including one or more of Co, V, Cr, Mo; M 6 including Sn; optionally, Li a M n O y The lithium-rich metal oxide core may include one or more of Li2NiO2, Li2CuO2, Li2MnO3, Li3VO4, Li3NbO4, Li5FeO4, Li6CoO4, and Li8SnO6. In this way, it is convenient to flexibly select a suitable lithium-rich metal oxide core according to actual needs.

[0103] In some embodiments, the material of the organic layer 121 includes one or more of rubber, asphalt, polypropylene, polyethylene, polystyrene, polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polyvinylidene fluoride, and polytetrafluoroethylene. Alternatively, the material of the organic layer 121 includes one or more of rubber, asphalt, and polyvinylidene fluoride. This allows for flexible selection of the material of the organic layer according to actual needs.

[0104] The softening temperature of rubber is about 140°C, the softening temperature of asphalt is about 250°C, the softening temperature of polypropylene is about 165°C, the softening temperature of polyethylene is about 180°C, the softening temperature of polystyrene is about 166°C, the softening temperature of polycarbonate is about 215°C, the softening temperature of polymethyl methacrylate is about 160°C, the softening temperature of polyethylene terephthalate is about 250°C, the softening temperature of polyvinylidene fluoride is about 160°C, and the softening temperature of polytetrafluoroethylene is about 330°C.

[0105] The above description of the lithium-rich metal oxide embodiment of the present application is combined with Figure 1. The following details an embodiment of the method for preparing the lithium-rich metal oxide. For any undescribed portion of the embodiment of the method for preparing the lithium-rich metal oxide, reference can be made to the relevant description of the embodiment of the lithium-rich metal oxide.

[0106] [Method for preparing lithium-rich metal oxide]

[0107] FIG2 is a flow chart of a method for preparing a lithium-rich metal oxide according to an embodiment of the present application. As shown in FIG2 , the method 200 for preparing a lithium-rich metal oxide includes the following steps.

[0108] Step 210: Provide a lithium-rich metal oxide core, a carbonaceous material, and an organic matter.

[0109] Step 220: Mix the lithium-rich metal oxide core, the carbonaceous material, and the organic matter, and process them to obtain the lithium-rich metal oxide.

[0110] The lithium-rich metal oxide 1 prepared by the method of the present application has high conductivity and stability, which is beneficial to improving the performance of battery cells.

[0111] Optionally, the lithium-rich metal oxide prepared by method 200 is the same as the lithium-rich metal oxide described above. In addition, the lithium-rich metal oxide prepared by method 200 may also be different in structure from the lithium-rich metal oxide described above.

[0112] In some embodiments, the above treatment includes sintering in an inert atmosphere for 2 to 6 hours, so as to obtain a uniformly coated lithium-rich metal oxide 1 .

[0113] In some embodiments, the inert atmosphere includes one or more of nitrogen, argon, and helium, so that it is convenient to select a suitable inert gas according to actual needs.

[0114] In some embodiments, the temperature of the above treatment does not exceed 500°C. Alternatively, the temperature does not exceed In this way, a lithium-rich metal oxide 1 with a uniform and dense coating layer can be achieved at a lower temperature.

[0115] In some embodiments, the method further comprises: screening the product after the above treatment to obtain lithium-rich metal oxide 1. In this way, lithium-rich metal oxide 1 with a suitable particle size can be obtained.

[0116] In some embodiments, the carbonaceous material includes an elemental carbon material; optionally, the elemental carbon material includes a one-dimensional carbon material; optionally, the one-dimensional carbon material includes carbon nanotubes. In this way, the effect of the decomposition of the carbonaceous material during the preparation of the lithium-rich metal oxide on the conductivity of the lithium-rich metal oxide can be reduced. The elemental carbon material includes a one-dimensional carbon material, which is conducive to the embedding or penetration of the carbonaceous material in the organic layer. The one-dimensional carbon material includes carbon nanotubes. Due to the high conductivity of carbon nanotubes, it is beneficial to improve the electronic conductivity of the lithium-rich metal oxide; in addition, the hollow tubes inside the carbon nanotubes can accommodate electrolytes, and the electrolyte can contact the lithium-rich metal oxide core through the hollow tubes. The hollow tubes can also serve as ion channels to transport lithium ions. Therefore, by selecting carbon nanotubes as carbonaceous materials, it is beneficial to further improve the conductivity of lithium-rich metal oxides.

[0117] Optionally, the carbon nanotubes include one or more of single-walled carbon nanotubes and multi-walled carbon nanotubes, so that different types of carbon nanotubes can be flexibly selected according to actual conditions.

[0118] In some embodiments, the aspect ratio of the carbon nanotubes is 100:1 to 1000:1, and can be optionally 200:1 to 400:1. In this way, both the coating effect on the lithium-rich metal oxide core and the conductivity of the lithium-rich metal oxide can be taken into consideration.

[0119] In some embodiments, the softening temperature of the organic material is lower than the sintering temperature. Optionally, the softening temperature of the organic material does not exceed 450° C., and optionally, does not exceed 300° C. In this way, the organic material softens at the sintering temperature and becomes fluidized, facilitating uniform and dense coating of the lithium-rich metal oxide core.

[0120] In some embodiments, the organic material includes one or more of rubber, asphalt, polypropylene, polyethylene, polystyrene, polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polyvinylidene fluoride, and polytetrafluoroethylene. Alternatively, the organic material includes one or more of rubber, asphalt, and polyvinylidene fluoride. This allows for flexible selection of the organic material based on actual needs.

[0121] In some embodiments, a lithium-rich metal oxide core is provided, comprising: mixing a Li source and a Mn source in a molar ratio of (a+0.05):1 to a:1, and then performing a single temperature sintering in an inert atmosphere for 4 to 8 hours, and the sintering temperature is 400°C to 600°C; wherein the Li source includes one or more of lithium oxide, lithium carbonate, lithium oxalate, lithium acetate, and lithium hydroxide, and the Mn source includes one or more of Mn oxide, hydroxide, halide, sulfate, carbonate, nitrate, oxalate, acetate, sulfide, and nitride; optionally, the sintering temperature is 450°C to 550°C; optionally, the inert atmosphere includes one or more of nitrogen, argon, and helium; the product of the single temperature sintering is subjected to air flow crushing to obtain a lithium-rich metal oxide core. In this way, it is easy to prepare a suitable lithium-rich metal oxide core, so as to facilitate the subsequent preparation of lithium-rich metal oxides. In addition, the method prepares a lithium-rich metal oxide core at a lower sintering temperature, which is beneficial to reduce costs and also helps reduce lithium volatilization.

[0122] [Positive electrode]

[0123] The present application provides a positive electrode sheet comprising the lithium-rich metal oxide in any one of the embodiments.

[0124] [Battery Cell]

[0125] The present application provides a battery cell, comprising the positive electrode sheet in the above embodiment.

[0126] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square, or any other shape.

[0127] FIG3 is a schematic diagram of a battery cell according to an embodiment of the present application. As shown in FIG3 , the battery cell 3 includes a housing 31 , a cover plate 32 , and an electrode assembly 33 disposed in the housing 31 .

[0128] The electrode assembly 33 can be made of the positive electrode sheet, the negative electrode sheet and the separator of the present application through a winding process or a lamination process.

[0129] Optionally, the battery cell 3 further includes an electrolyte. The electrolyte can be solid, semi-solid, or liquid, and this embodiment of the application does not impose any specific limitation on this.

[0130] In some embodiments, battery cells may be assembled into a battery module. The number of battery cells contained in a battery module may be one or more. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0131] Figure 4 is a schematic diagram of a battery module according to one embodiment of the present application. Referring to Figure 4 , within the battery module 4, multiple battery cells 3 may be arranged sequentially along the length of the battery module 4. Of course, any other arrangement is also possible. Furthermore, the multiple battery cells 3 may be secured together using fasteners.

[0132] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 3 are accommodated in the accommodation space.

[0133] [Battery]

[0134] The present application provides a battery, comprising the battery cell described in the above embodiment.

[0135] Figure 5 is a schematic diagram of a battery according to an embodiment of the present application. As shown in Figure 5 , the present application provides a battery 5 comprising the battery cell 3 according to any of the above embodiments.

[0136] The battery cells 3 can be directly assembled into the battery 5 , or they can be assembled into battery modules first, and then multiple battery modules can be assembled into the battery 5 .

[0137] [Electrical devices]

[0138] The present application provides an electrical device, comprising the battery described in the above embodiment.

[0139] Figure 6 is a schematic diagram of an electric device according to an embodiment of the present application. As shown in Figure 6 , the present application provides an electric device 6 including the battery 5 according to the above embodiment.

[0140] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0141] [Example]

[0142] Examples 1-9

[0143] The difference between Example 1 and Examples 2-9 is that the ratio of the mass of the coating layer to the mass of the lithium-rich metal oxide is different, that is, the total content of the coating layer is different.

[0144] Examples 10-15

[0145] The difference between Example 1 and Examples 10-15 is that the ratio of the mass of the carbon nanotubes to the mass of the lithium-rich metal oxide is different, that is, the content of the carbon nanotubes is different.

[0146] Examples 16-21

[0147] The difference between Example 1 and Examples 16-21 is that the median particle size of the lithium-rich metal oxide is different.

[0148] Examples 22-28

[0149] The difference between Example 1 and Examples 22-28 is that the aspect ratios of the carbon nanotubes are different.

[0150] Examples 29-35

[0151] The difference between Example 1 and Examples 29-35 is that the temperature T1 is different, that is, the sintering temperature when preparing the lithium-rich metal oxide core is different.

[0152] Examples 36-41

[0153] The difference between Example 1 and Examples 36-41 is that the temperature T2 is different, that is, the temperature when the lithium-rich metal oxide is prepared using the lithium-rich metal oxide core, organic matter and carbonaceous material is different.

[0154] Examples 42-45

[0155] The difference between Example 1 and Examples 42-45 is that the types of lithium-rich metal oxide cores are different.

[0156] Examples 46-48

[0157] The difference between Example 1 and Examples 46-48 is that the types of carbonaceous materials are different.

[0158] Examples 49-50

[0159] The difference between Example 1 and Examples 49-50 is that the types of organic matter are different.

[0160] Comparative Example 1

[0161] In Comparative Example 1, the lithium-rich metal oxide core was not coated.

[0162] Comparative Examples 2-3

[0163] In Comparative Example 2, only carbon nanotubes were used to coat the lithium-rich metal oxide core, and in Comparative Example 3, only asphalt was used to coat the lithium-rich metal oxide core.

[0164] Comparative Examples 4-6

[0165] In comparative example 4, the lithium-rich metal oxide core is only mixed with carbon nanotubes without sintering; in comparative example 5, the lithium-rich metal oxide core is only mixed with asphalt without sintering; in comparative example 6, the lithium-rich metal oxide core, carbon nanotubes and asphalt are only mixed without sintering.

[0166] [Preparation method of lithium-rich metal oxide]

[0167] (1) Preparation of lithium-rich metal oxide core

[0168] Combine Li source with M n The source is in a molar ratio of (a+0.05):1 to a:1 (where M n Including M 1 ~M 6 After mixing evenly, the mixture is sintered once at a high temperature in a nitrogen inert atmosphere, wherein the sintering temperature refers to the sintering temperature T1 of different embodiments in Table 1, and the sintering time is 4h to 8h.

[0169] The Li source of Example 1-42 includes lithium hydroxide, M n The source includes ferric oxide; the Li source of Example 43 includes lithium hydroxide, M n The source includes cobalt hydroxide; the Li source of Example 44 includes lithium hydroxide, M n The source includes copper oxide; the Li source of Example 45 includes lithium hydroxide, M n The source includes nickel hydroxide; the Li source of Example 46 includes lithium hydroxide, M n The source includes niobium pentoxide.

[0170] The product obtained by the above-mentioned single temperature-raising sintering is subjected to air flow crushing to obtain a lithium-rich metal oxide core.

[0171] (2) Preparation of lithium-rich metal oxides

[0172] The lithium-rich metal oxide core, carbonaceous material and organic matter are uniformly mixed and then sintered at a low temperature. Specific parameters such as the sintering temperature T2 are shown in Table 1. After sintering, the mixture is sieved to obtain a lithium-rich metal oxide.

[0173] [Test of total content of coating layer]

[0174] The total content W of the coating layer can be measured using a high-frequency infrared carbon and sulfur analyzer (C content analyzer, model HCS-140, Shanghai Dekai Instrument Co., Ltd.) in accordance with GBT20123-2006 "Determination of total carbon and sulfur content of steel using infrared absorption method after combustion in a high-frequency induction furnace (conventional method)".

[0175] The content Wo of the organic layer in the coating layer can be tested using a thermal analyzer with model NETZSCH STA449F3. 20 mg of lithium-rich metal oxide is weighed and added to a corundum crucible. Under an inert gas atmosphere, the thermal weight loss rate of the lithium-rich metal oxide is tested when the temperature is increased from 25°C to 800°C, where the heating rate can be 10°C / min.

[0176] Specifically, 20 mg of lithium-rich metal oxide was weighed and added to a corundum crucible. The TG curve of the lithium-rich metal oxide was measured by a thermal analysis instrument under a nitrogen atmosphere to obtain its thermal weight loss rate (the percentage of the weight lost by thermal decomposition to the original sample weight) W L1 % and softening temperature T, and the type of organic matter can be determined by the softening temperature.

[0177] Combined with the TG curve of the organic matter, its weight loss rate W is obtained L2 % (can be obtained by referring to relevant data or through experiments), and then calculated: Wo = W L1 / W L2 .

[0178] [Testing of carbon nanotube content and aspect ratio]

[0179] The carbon nanotube content Wc is equal to the total coating content W minus the organic matter content Wo.

[0180] The aspect ratio of carbon nanotubes can be measured by transmission electron microscopy. Normally, 20 well-dispersed carbon nanotubes are taken, their outer diameters and lengths are measured respectively, and the average value is taken as the aspect ratio of the carbon nanotubes.

[0181] [The median particle size Dv of lithium-rich metal oxides 50 Tests]

[0182] The median particle size Dv of lithium-rich metal oxides 50It can be measured with a laser particle size analyzer, referring to GB / T 19077-2016 particle size distribution laser diffraction method.

[0183] [Testing the resistivity of lithium-rich metal oxides]

[0184] The powder of the lithium-rich metal oxide was dried, and an appropriate amount of powder was weighed. The powder resistivity of the sample was then measured using a powder resistivity tester (ST2722 digital four-probe tester, manufactured by Suzhou Jingge Electronics Co., Ltd.) in accordance with GB / T 30835-2014 "Carbon-composite lithium iron phosphate lithium-rich metal oxide for lithium-ion batteries" at a test pressure of 20 MPa.

[0185] [Preparation of lithium-ion batteries]

[0186] Preparation of the positive electrode sheet: Lithium-rich metal oxide, binder polyvinylidene fluoride (PVDF), and conductive agent acetylene black are dissolved in N-methylpyrrolidone (NMP) at a mass ratio of 97:2:1. The mixture is thoroughly stirred and mixed to form a positive electrode slurry. The slurry is evenly coated on the positive electrode current collector aluminum foil. The positive electrode sheet is then dried, cold-pressed, and slit. In the preparation of this positive electrode sheet, the lithium-rich metal oxide is used as the active material, and no other active materials are added.

[0187] Preparation of negative electrode sheets: Dissolve the negative electrode active material artificial graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) in deionized water at a mass ratio of 96:1.5:1.5:1.0, stir and mix thoroughly to prepare a negative electrode slurry; coat the negative electrode slurry on the negative electrode current collector copper foil, and then dry, cold press, and cut to obtain a negative electrode sheet.

[0188] Isolation film: polypropylene film.

[0189] Preparation of the electrolyte: Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and LiPF6 was uniformly dissolved in the above solution to obtain an electrolyte. The concentration of LiPF6 in the electrolyte was 1 mol / L.

[0190] Preparation of lithium-ion batteries: The positive electrode sheet, separator, and negative electrode sheet are stacked and wound in order to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the electrolyte prepared above is added. After packaging, standing, formation, aging and other processes, a lithium-ion battery is obtained.

[0191] [Testing the initial charge capacity of lithium-ion batteries]

[0192] The assembled lithium-ion battery was charged at a constant current of 0.1C to 4.25V, left to stand for 5 minutes, and the first-cycle charging capacity of the lithium-ion battery was recorded. The first-cycle charging capacity of the lithium-ion battery was obtained by dividing the first-cycle charging capacity of the battery by the mass of the lithium-rich metal oxide.

[0193] [Test of lithium ion diffusion coefficient]

[0194] The diffusion coefficient of lithium ions can be measured using conventional methods in the art such as the CV method, EIS method, GITT method, and PITT method, and calculated based on Fick's first and second laws.

[0195] Using the GITT method as an example, the steps for measuring the lithium ion diffusion coefficient of a lithium-rich metal oxide used as a cathode active material are as follows: Grind the lithium-rich metal oxide into a powder microelectrode; connect the powder microelectrode to an electrochemical workstation and perform a coulometric titration. The titration is performed with a pulse current of 20 μA for 1 hour and a rest period of 4 hours. (Note: To compare the effects of pulse current and time, a parallel experiment with 10 μA and 10 minutes can be performed.) After obtaining the GITT curve, the lithium ion diffusion coefficient is calculated using the following formula:

[0196] Among them, D Li is the lithium ion diffusion coefficient; I0 ​​is the applied current 20μA; V m is the molar volume of the active material lithium-rich metal oxide; F is the Faraday constant; A is the electrode surface area, n is the number of electrons participating in the reaction, which can also be understood as the charge number of lithium ions, that is, n can be 1, dE / dx is the slope of the coulometric titration curve, that is, the slope of the open circuit potential at a certain concentration on the Li concentration curve in the electrode; (dE) / (dt 1 / 2 ) is the polarization voltage versus t 1 / 2 The slope of the curve. For details, please refer to: Xie et al., Solid State Ionics, 2007, 178: 1218–1224; Yang et al., Electrochimica Acta, 2012, 66: 88–93.

[0197] As shown in Tables 1 and 2, Table 1 shows the specific parameters of different embodiments and comparative examples, and Table 2 shows the experimental results of different embodiments and comparative examples. Lithium-ion batteries were prepared using the lithium-rich metal oxides of the different embodiments, and the performance of the lithium-ion batteries was tested. The test results can be found in Table 2.

[0198] In Table 1, the lithium-rich metal oxide core is the type of lithium-rich metal oxide core selected in the lithium-rich metal oxide, the organic matter is the material of the organic layer in the coating layer covering the lithium-rich metal oxide core, the carbonaceous material is the type of carbonaceous material in the coating layer, the total content of the coating layer is the ratio of the weight of the coating layer to the weight of the lithium-rich metal oxide, the carbon nanotube content is the ratio of the weight of the carbon nanotube to the weight of the lithium-rich metal oxide, and Dv 50 is the median particle size of the lithium-rich metal oxide, the aspect ratio of carbon nanotubes is the ratio of the length of the carbon nanotubes in the coating layer to their outer diameter, temperature T1 is the sintering temperature when preparing the lithium-rich metal oxide core, and temperature T2 is the sintering temperature when preparing the lithium-rich metal oxide using the lithium-rich metal oxide core, organic matter, and carbonaceous material. In Table 1, CNTs represents the carbonaceous material being carbon nanotubes, P represents the organic matter being pitch, RB represents the organic matter being rubber, and PVDF represents the organic matter being polyvinylidene fluoride.

[0199] Table 1 Specific parameters of the examples and comparative examples

[0200]

[0201]

[0202] Table 2 Test results of the embodiments and comparative examples

[0203]

[0204]

[0205] Figure 7 is a schematic diagram of a scanning electron microscope image of a lithium-rich metal oxide core that is not coated with a coating layer; Figure 8 is a schematic diagram of a scanning electron microscope image of a lithium-rich metal oxide core that is coated with a coating layer in the present application.

[0206] Combining Comparative Example 1 with Examples 1-50, the resistivity of the lithium-rich metal oxide not coated with a coating layer is much greater than that of the lithium-rich metal oxide with a coating layer, and after the lithium-rich metal oxide not coated with a coating layer is made into a battery, its first-cycle charging capacity and lithium ion diffusion coefficient are much lower than those of the battery made of the lithium-rich metal oxide with a coating layer.

[0207] As shown in Figure 7 , the surface of the lithium-rich metal oxide contains an inert lithium-containing compound, which affects the diffusion coefficient of lithium ions, the conductivity of the lithium-rich metal oxide, the charge capacity of the lithium-ion battery, and other properties. As shown in Figure 8 , the surface of the lithium-rich metal oxide core is coated with a coating layer, and the coating layer is embedded with carbon nanotubes. Combined with Example 1 and its test data, the performance of the lithium-rich metal oxide provided with the coating layer is significantly improved.

[0208] In combination with Examples 1-9, by reasonably setting the content of the coating layer, the battery capacity and the diffusion coefficient of lithium ions can be taken into account; when the content of the coating layer is low, the coating effect is weakened and the charging capacity of the battery is reduced; when the content of the coating layer is high, the escape of lithium ions is affected and the charging capacity of the battery is reduced.

[0209] In combination with Examples 10-13, by reasonably setting the content of carbon nanotubes, the conductivity of the lithium-rich metal oxide, the capacity of the battery and the diffusion coefficient of lithium ions can be taken into account; in combination with Example 14, when the content of carbon nanotubes is low, the conductivity of the lithium-rich metal oxide powder decreases; in combination with Example 15, when the content of carbon nanotubes is high, the charging capacity of the battery decreases.

[0210] In combination with Examples 16-19, by reasonably setting the median particle size of the lithium-rich metal oxide, the coating uniformity and capacity of the lithium-rich metal oxide can be taken into account, which is beneficial to ensuring the capacity of the battery; in combination with Example 20, when the median particle size of the lithium-rich metal oxide is smaller, the charging capacity of the battery is reduced; in combination with Example 21, when the median particle size of the lithium-rich metal oxide is larger, the charging capacity of the battery is reduced.

[0211] In combination with Examples 22-26, by reasonably setting the aspect ratio of the carbon nanotubes, the capacity of the battery and the conductivity of the lithium-rich metal oxide can be taken into account; in combination with Example 27, when the aspect ratio of the carbon nanotubes is relatively small, the diffusion coefficient of lithium ions is low; in combination with Example 28, when the aspect ratio of the carbon nanotubes is relatively large, the charging capacity of the battery is reduced.

[0212] In combination with Examples 29-33, by reasonably setting the temperature T1, a good balance between battery capacity and the diffusion coefficient of lithium ions can be maintained; in combination with Example 34, when the primary sintering temperature is low, the capacity of the battery is reduced; in combination with Example 35, when the primary sintering temperature is high, the diffusion coefficient of lithium ions is reduced.

[0213] In combination with Examples 36-41, by reasonably setting the temperature T2, the conductivity and stability of the lithium-rich metal oxide, the capacity of the battery and the diffusion coefficient of lithium ions can be taken into account.

[0214] In conjunction with Examples 42-45, the coating layer of the present application can be coated on the surface of various lithium-rich metal oxide cores to improve battery performance. In conjunction with Examples 46-48, various different carbonaceous materials can be used to coat the lithium-rich metal oxide core, thereby improving the conductivity of the lithium-rich metal oxide. In conjunction with Examples 49-50, various different organic substances can be used to coat the lithium-rich metal oxide core.

[0215] In combination with Comparative Examples 2-3 and Examples 1-50, it is difficult to take into account both the capacity of the battery and the conductive properties of the lithium-rich metal oxide when only carbon nanotubes or organic matter are used for coating.

[0216] In combination with Comparative Examples 4-6 and Examples 1-44, it is difficult to form a coating layer by simply mixing several materials.

[0217] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A lithium-rich metal oxide, characterized in that include: Lithium-rich metal oxide core; The coating layer comprises an organic layer and a carbonaceous material, the organic layer covers the lithium-rich metal oxide core, and at least a portion of the carbonaceous material is embedded in the organic layer.

2. The lithium-rich metal oxide according to claim 1, characterized in that At least a portion of the carbonaceous material penetrates the organic layer.

3. The lithium-rich metal oxide according to claim 1 or 2, characterized in that The carbonaceous material includes a simple carbon material; optionally, the simple carbon material includes a one-dimensional carbon material; optionally, the one-dimensional carbon material includes a carbon nanotube.

4. The lithium-rich metal oxide according to claim 3, characterized in that The carbon nanotubes include one or more of single-walled carbon nanotubes and multi-walled carbon nanotubes.

5. The lithium-rich metal oxide according to claim 3 or 4, characterized in that The aspect ratio of the carbon nanotubes is 100:1 to 1000:1, and can be optionally 200:1 to 400:

1.

6. The lithium-rich metal oxide according to any one of claims 3 to 5, characterized in that The mass ratio of the carbon nanotubes to the lithium-rich metal oxide is 0.2% to 2%, and can be optionally 0.5% to 1.5%.

7. The lithium-rich metal oxide according to any one of claims 1 to 6, characterized in that The softening temperature of the organic layer does not exceed 450°C, and optionally, does not exceed 300°C.

8. The lithium-rich metal oxide according to any one of claims 1 to 7, characterized in that The median particle size Dv of the lithium-rich metal oxide 50 It is 2μm~10μm, and can be optionally 4μm~8μm.

9. The lithium-rich metal oxide according to any one of claims 1 to 8, characterized in that The mass ratio of the coating layer to the lithium-rich metal oxide is 1% to 10%, and can be optionally 3% to 7%.

10. The lithium-rich metal oxide according to any one of claims 1 to 9, characterized in that The lithium-rich metal oxide core material includes Li a M n O y , 2≤a≤8, the Li a M n O y Including Li2M 1 O2、Li2M 2 O3、Li3M 3 O4、Li5M 4 O4、Li6M 5 O4、Li8M 6 One or more of O6; M 1 Including one or more of Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, and Mo; M 2 Including one or more of Mn, Sn, Mo, Ru, and Ir; M 3 Including one or more of V, Nb, Cr, and Mo; M 4 Including one or more of Fe, Cr, V, and Mo; M 5 Including one or more of Co, V, Cr, and Mo; M 6 Including Sn; Optionally, the Li a M n O y Including one or more of Li2NiO2, Li2CuO2, Li2MnO3, Li3VO4, Li3NbO4, Li5FeO4, Li6CoO4, and Li8SnO6.

11. The lithium-rich metal oxide according to any one of claims 1 to 10, characterized in that The material of the organic layer includes one or more of rubber, asphalt, polypropylene, polyethylene, polystyrene, polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polyvinylidene fluoride, and polytetrafluoroethylene; optionally, the material of the organic layer includes one or more of rubber, asphalt and polyvinylidene fluoride.

12. A method for preparing a lithium-rich metal oxide, characterized in that: include: Providing lithium-rich metal oxide cores, carbonaceous materials and organic matter; The lithium-rich metal oxide core, the carbonaceous material and the organic matter are mixed and treated to obtain the lithium-rich metal oxide.

13. The method according to claim 12, characterized in that The treatment comprises: sintering in an inert atmosphere for 2 hours to 6 hours, optionally, the inert atmosphere comprises one or more of nitrogen, argon and helium; and / or, The treatment temperature does not exceed 500°C, and optionally, the treatment temperature does not exceed 300°C.

14. The method according to claim 12 or 13, characterized in that The method further comprises: The product after the treatment is screened to obtain the lithium-rich metal oxide.

15. The method according to any one of claims 12 to 14, characterized in that: The carbonaceous material includes a simple carbon material; optionally, the simple carbon material includes a one-dimensional carbon material; optionally, the one-dimensional carbon material includes a carbon nanotube.

16. The method according to claim 15, characterized in that The carbon nanotubes include one or more of single-walled carbon nanotubes and multi-walled carbon nanotubes.

17. The method according to claim 15 or 16, characterized in that The aspect ratio of the carbon nanotubes is 100:1 to 1000:1, and can be optionally 200:1 to 400:

1.

18. The method according to any one of claims 12 to 17, characterized in that: The softening temperature of the organic matter is lower than the treatment temperature; optionally, the softening temperature of the organic matter does not exceed 450°C; optionally, the softening temperature of the organic matter does not exceed 300°C.

19. The method according to any one of claims 12 to 18, characterized in that: The organic matter includes one or more of rubber, asphalt, polypropylene, polyethylene, polystyrene, polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polyvinylidene fluoride, and polytetrafluoroethylene; optionally, the organic matter includes one or more of rubber, asphalt, and polyvinylidene fluoride.

20. The method according to any one of claims 12 to 19, characterized in that The method of providing a lithium-rich metal oxide core comprises: Combine Li source with M n The sources are mixed in a molar ratio of (a+0.05):1 to a:1 and then sintered in an inert atmosphere for 4h to 8h at a temperature of 400°C to 600°C; wherein the Li source comprises one or more of lithium oxide, lithium carbonate, lithium oxalate, lithium acetate, and lithium hydroxide, and the M n Sources include M n One or more of oxides, hydroxides, halides, sulfates, carbonates, nitrates, oxalates, acetates, sulfides, and nitrides; optionally, the sintering temperature is 450° C. to 550° C.; optionally, the inert atmosphere includes one or more of nitrogen, argon, and helium; The product of the primary temperature-raising sintering is subjected to air flow crushing to obtain the lithium-rich metal oxide core.

21. A positive electrode sheet, characterized in that: The invention comprises the lithium-rich metal oxide as described in any one of claims 1 to 11.

22. A battery cell, characterized in that: Comprising the positive electrode sheet as claimed in claim 21.

23. A battery, characterized in that: Comprising the battery cell as claimed in claim 22.

24. An electrical device, characterized in that: Comprising a battery as claimed in claim 23.

Images