Positive electrode active material, method for manufacturing the same, positive electrode plate containing the same, battery cell, battery, and power consumption device

Abstract

This application provides a positive electrode active material, a method for producing the same, a positive electrode plate containing the same, a battery cell, a battery, and a power consumption device, wherein the positive electrode active material comprises a substrate and a sodium-rich layer formed in situ on the substrate surface, the substrate comprising a sodium-containing layered transition metal oxide, and the sodium-rich layer comprising one or more sodium salts represented by formulas (I) and (II), where m represents an integer from 1 to 8 and n represents an integer from 2 to 20. [Formula 1] TIFF2026511410000024.tif59123

Description

[Technical Field]

[0001] This application relates to a positive electrode active material, a method for producing the same, a positive electrode plate containing the same, a battery cell, a battery, and a power consumption device. [Background technology]

[0002] In recent years, batteries have been widely used in energy storage and power systems such as hydroelectric, thermal, wind, and solar power plants, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. Currently, lithium-ion batteries still occupy a core position in the battery market, but at the same time, lithium-ion batteries also face significant challenges, such as the increasing scarcity of lithium resources. Sodium resources are far more abundant and widely distributed than lithium resources, and their cost is much lower than lithium, making sodium-ion batteries a new generation of electrochemical systems with a high potential to replace lithium-ion batteries. The positive electrode active material is a crucial element that affects the performance of sodium-ion batteries, and due to constraints in the manufacturing process, relatively high levels of free alkaline substances are often present on the surface of the positive electrode active material, which affects the performance of sodium-ion batteries. Therefore, effective technical means to improve the performance of the positive electrode active material are needed. The above description is for the purpose of providing background art information related to this application and does not necessarily constitute prior art. [Overview of the Initiative]

[0003] This application provides a positive electrode active material that can improve the energy density and cycle performance of a battery, a method for manufacturing the same, a positive electrode plate containing the same, a battery cell, a battery, and a power consumption device.

[0004] A first aspect of this application provides a positive electrode active material comprising a substrate and a sodium-rich layer formed in situ on the surface of the substrate, wherein the substrate comprises a sodium-containing layered transition metal oxide, and the sodium-rich layer comprises one or more sodium salts represented by formulas (I) and (II). [ka] m represents an integer from 1 to 8, and n represents an integer from 2 to 20.

[0005] The sodium-rich layer in the positive electrode active material according to the embodiment of this application is formed in situ on the substrate surface, thereby uniformly dispersing the sodium salt on the substrate surface, reducing direct contact between the substrate and the electrolyte, decreasing side reactions, and further improving the cycle stability of the positive electrode active material. The sodium-rich layer contains one or more of the sodium salts represented by formulas (I) and (II) above, which, as sodium replenishers, provide an additional sodium source during the first cycle charging process of the battery (i.e., the battery formation process) and can replenish the loss of activated sodium during the film formation process of the negative electrode. As activated sodium is gradually consumed during the battery cycle, the sodium salts represented by formulas (I) and (II) above provide excess activated sodium to be stored in the negative electrode, replenishing the loss of activated sodium during the battery cycle and reducing the probability of excessive desorption of sodium ions in the positive electrode active material, thereby improving the structural stability of the positive electrode active material and improving the battery cycle performance. The sodium salts represented by formulas (I) and (II) above undergo an irreversible sodium desorption process during the first charging cycle of the battery. During the sodium desorption process, the sodium salt further decomposes to produce carbon dioxide, which is then released in gaseous form. The solid remaining after sodium desorption mainly adheres to the substrate surface in the form of elemental carbon, improving electronic conductivity, reducing polarization, and decreasing direct contact between the substrate and the electrolyte. This reduces side reactions and improves the battery's cycle performance. Therefore, the positive electrode active material according to the embodiment of this application can improve the energy density and cycle performance of the battery.

[0006] In any embodiment, the sodium-rich layer is made of the following sodium salt [ka] including one or more of them.

[0007] In any of the embodiments, the sodium-rich layer comprises the following sodium salts [Chemical formula] including one or more of them.

[0008] In any of the embodiments, the thickness of the sodium-rich layer is denoted as h, and the volume distribution particle size Dv50 of the positive electrode active material is denoted as D. The unit is nm in both cases, and 0.005 ≤ h / D ≤ 0.05, and optionally 0.01 ≤ h / D ≤ 0.025. By adjusting h / D within the above range, the positive electrode active material can have a high gram capacity, and furthermore, the positive electrode active material can have a relatively high structural stability, and furthermore, the battery can have a high energy density and a long cycle life.

[0009] In any of the embodiments, the thickness of the sodium-rich layer is 30 - 120 nm, and optionally 40 - 100 nm. When the thickness of the sodium-rich layer is within the above range, the positive electrode active material can have a high gram capacity and high cycle stability, and furthermore, the battery can have a high energy density and a long cycle life.

[0010] In any of the embodiments, the volume distribution particle size Dv50 of the positive electrode active material is 2000 - 8000 nm. When the volume distribution particle size Dv50 of the positive electrode active material is within the above range, it can have a relatively high gram capacity and a relatively high tap density, and also can have a good ion transport ability, and furthermore, the battery can have a higher energy density and a longer cycle life.

[0011] In any of the embodiments, the sodium-rich layer is located on 80%-100% of the surface of the substrate, and selectively on 95%-100% of the surface. Thereby, a good sodium replenishment effect can be achieved, and furthermore, the direct contact between the substrate and the electrolyte can be reduced, side reactions can be reduced, and the cycle stability of the cathode active material can be improved, and the cycle performance of the battery can be improved.

[0012] In any of the embodiments, the cathode active material includes one or more of the O3 phase, P2 phase, and P3 phase.

[0013] In any of the embodiments, the content of the free alkaline substance on the surface of the cathode active material is 13% or less, and selectively 3.2% or less. Since the content of the free alkaline substance on the surface of the cathode active material is relatively low, the cathode active material can have relatively high interfacial stability, which is advantageous for improving the cycle performance and / or rate performance of the battery, and furthermore, is advantageous for improving the processing performance of the cathode slurry and the battery.

[0014] In any of the embodiments, the pH of the cathode active material is 10.0 - 13.0, and selectively 11.0 - 12.3. Since the pH of the cathode active material is relatively low, the cathode active material can have relatively high interfacial stability, which is advantageous for improving the cycle performance and / or rate performance of the battery, and furthermore, is advantageous for improving the processing performance of the cathode slurry and the battery.

[0015] In any of the embodiments, the carbon content of the cathode active material is 1% - 13%, and selectively 6.3% - 8.5%.

[0016] In any of the embodiments, the sodium-containing layered transition metal oxide includes one or more of the oxides represented by formula (III), Na x M a A b B c O m Q n Formula (III) 0 < x ≤ 1, 0 < a ≤ 1, 0 ≤ b ≤ 1 / 3, 0 ≤ c ≤ 1 / 3, 1.9 ≤ m ≤ 2, 0 ≤ n ≤ 0.1, M contains one or more of Ni, Mn, Fe, Co, Cu, A contains one or more metal elements of Group IA, IIA, IIIA, IVA, VA, IIB, IIIB, IVB, VB, VIB, and optionally contains one or more elements of Li, K, Mg, Ca, Sr, Ba, Zn, La, Sc, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Al, Sn, Ge, Bi, Sb, B contains one or more non-metal elements of Group IIIA, IVA, VA, VIA, and optionally contains one or more elements of Si, P, B, S, Se, Q contains one or more non-metal elements of Group VA, VIIA, and optionally contains one or more elements of F, Cl, N.

[0017] The second aspect of this application provides a method for manufacturing a positive electrode active material, and this method for manufacturing a positive electrode active material includes: Providing a sodium-containing layered transition metal oxide, wherein the surface of the sodium-containing layered transition metal oxide contains a free alkaline substance, and the alkaline substance contains sodium hydroxide and / or sodium carbonate; Providing a solvent and a first reaction component, wherein the solvent contains a polar organic solvent, and the first reaction component contains one or more of the compounds represented by formula (1) and formula (2),

Chemical formula

[0018] The manufacturing method according to the embodiments of this application can reduce the content of free alkaline substances on the substrate surface, while simultaneously being less likely to destroy the bulk structure of the substrate. Furthermore, the manufacturing method according to the embodiments of this application can generate uniformly dispersed sodium salts in situ on the substrate surface. These sodium salts can reduce polarization, provide an additional sodium source, replenish the loss of activated sodium during the negative electrode film formation process, and provide excess activated sodium for storage in the negative electrode, thereby replenishing the loss of activated sodium during the battery cycle process. Therefore, the positive electrode active material obtained by the manufacturing method according to the embodiments of this application can improve the energy density and cycle performance of the battery, and further improve the consistency of the battery.

[0019] In any embodiment, the molar ratio of the first reactant to the sodium-containing layered transition metal oxide is 0.1:1 or less, and selectively between 0.02:1 and 0.07:1. When the molar ratio of the first reactant to the sodium-containing layered transition metal oxide is within the above range, the content of free alkaline substances on the substrate surface can be effectively reduced, the positive electrode active material can be given an appropriate degree of sodium replenishment, and furthermore, the positive electrode active material can be given a high gram capacity and high structural stability, thereby enabling the battery to have a high energy density and a long cycle life.

[0020] In any embodiment, the mass ratio of the sodium-containing layered transition metal oxide to the solvent is 10:100 to 25:100, and selectively 15:100 to 22:100. When the mass ratio of the sodium-containing layered transition metal oxide to the solvent is within the above range, the content of free alkaline substances on the substrate surface can be effectively reduced, the positive electrode active material can be given an appropriate degree of sodium replenishment, and furthermore, the positive electrode active material can be given high gram capacity and high structural stability, thereby enabling the battery to have high energy density and long cycle life.

[0021] In any of the embodiments, the first reaction component is the following compound [ka] This includes one or more of the following.

[0022] In any of the embodiments, the first reaction component is the following compound [ka] This includes one or more of the following.

[0023] When the first reactant is within the above range, it is possible to effectively reduce the amount of free alkaline material on the substrate surface, provide the positive electrode active material with an appropriate amount of sodium replenishment, and give the positive electrode active material a high gram capacity. In addition, it is possible to reduce the polarization of the positive electrode active material and give the positive electrode active material high structural stability. As a result, when the first reactant is within the above range, the battery can have a high energy density and a long cycle life.

[0024] In any of the embodiments, the temperature of the drying is not higher than the boiling point of the polar organic solvent, and optionally, 10°C ≤ the boiling point of the polar organic solvent - the temperature of the drying ≤ 30°C. When the temperature of the drying is within the above range, the content of the free alkaline substances on the surface of the substrate can be effectively reduced, an appropriate degree of sodium supplementation can be provided to the positive electrode active material, and further, the positive electrode active material can be provided with a high gram capacity and a high structural stability, whereby the battery can be provided with a high energy density and a long cycle life.

[0025] In any of the embodiments, the drying is spray drying. Spray drying contributes to more uniformly dispersing the sodium salt formed after the reaction on the surface of the substrate, and further contributes to adjusting the content of the sodium salt on the surface of the substrate.

[0026] In any of the embodiments, the polar organic solvent contains one or more of an alcohol solvent, a ketone solvent, a nitrile solvent, and an ether solvent, and optionally contains one or more of ethanol, methanol, acetone, N-methylpyrrolidone, acetonitrile, tetrahydrofuran, and 1,4-dioxane.

[0027] In any of the embodiments, the volume fraction of the polar organic solvent is from 80% to 100% based on the total volume of the solvent.

[0028] In any of the embodiments, the solvent further contains water, and the volume fraction of the water is 20% or less based on the total volume of the solvent.

[0029] In any of the embodiments, the sodium-containing layered transition metal oxide contains one or more of the oxides represented by the formula (III), Na x M a A b B c O m Q n Formula (III) 0 < x ≤ 1, 0 < a ≤ 1, 0 ≤ b ≤ 1 / 3, 0 ≤ c ≤ 1 / 3, 1.9 ≤ m ≤ 2, 0 ≤ n ≤ 0.1, M contains one or more of Ni, Mn, Fe, Co, Cu, A contains one or more metal elements of Group IA, IIA, IIIA, IVA, VA, IIB, IIIB, IVB, VB, VIB, and optionally contains one or more elements of Li, K, Mg, Ca, Sr, Ba, Zn, La, Sc, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Al, Sn, Ge, Bi, Sb, B contains one or more non-metal elements of Group IIIA, IVA, VA, VIA, and optionally contains one or more elements of Si, P, B, S, Se, Q contains one or more non-metal elements of Group VA, VIIA, and optionally contains one or more elements of F, Cl, N.

[0030] In any of the examples, the volume distribution particle size Dv50 of the sodium-containing layered transition metal oxide is 2000 - 8000 nm.

[0031] In any of the examples, the sodium-containing layered transition metal oxide contains one or more of the O3 phase, P2 phase, and P3 phase.

[0032] The third aspect of this application provides a positive electrode plate, which includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector. Here, the positive electrode film layer contains the positive electrode active material of the first aspect of this application or the positive electrode active material manufactured by the method of the second aspect of this application.

[0033] In any of the examples, the content of the positive electrode active material in the positive electrode film layer is 50 wt% to 99 wt%, and optionally 85 wt% to 99 wt% based on the total weight of the positive electrode film layer.

[0034] The fourth aspect of this application provides a battery cell including the positive electrode plate of the third aspect of this application.

[0035] The fifth aspect of this application provides a battery including the battery cell of the fourth aspect of this application.

[0036] A sixth aspect of this application provides a power consumption device including a battery according to the fifth aspect of this application.

[0037] The power consumption device of this application includes a battery according to this application and therefore has at least the same advantages as the aforementioned battery. [Brief explanation of the drawing]

[0038] To more clearly explain the technical concept of the embodiments of this application, the following is a brief introduction to the drawings that may be used in the embodiments of this application. Obviously, the drawings described below represent only a few embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without expending any creative effort. [Figure 1] This is a schematic diagram of one embodiment of the battery cell of this application. [Figure 2] Figure 1 is a schematic exploded view of an embodiment of the battery cell. [Figure 3] This is a schematic diagram of one embodiment of the battery module of this application. [Figure 4] This is a schematic diagram of one embodiment of the battery pack of this application. [Figure 5] Figure 4 is a schematic exploded view of an embodiment of the battery pack shown. [Figure 6] This is a schematic diagram of one embodiment including a power consumption device that uses the battery of the present application as a power source. [Figure 7] This is an energy-dispersive X-ray spectroscopy (EDS) image of the positive electrode active material produced in Example 2. Note that the drawings are not necessarily drawn to actual scale. [Modes for carrying out the invention]

[0039] Hereinafter, with appropriate reference to the drawings, embodiments specifically disclosing the positive electrode active material, its manufacturing method, and positive electrode plates, battery cells, batteries, and power consumption devices contained herein will be described in detail. However, unnecessary detailed explanations may be omitted. For example, detailed explanations of well-known matters and repeated explanations of structures that are actually the same may be omitted. This is to avoid the following explanation becoming unnecessarily redundant and to make it easily understandable to those skilled in the art. The drawings and the following explanation are provided to enable those skilled in the art to fully understand this application and are not intended to limit the topics described in the claims.

[0040] The “range” disclosed in this application is limited in the form of a lower limit and an upper limit, and a given range is limited by selecting one lower limit and one upper limit, which define the boundary of a particular range. The range thus limited may or may not include the limit value, and any combination is possible, that is, any lower limit may be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 are also conceivable. Furthermore, if the minimum range values ​​are listed as 1 and 2, and the maximum range values ​​are listed as 3, 4 and 5, then the ranges 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5 are all conceivable. In this application, unless otherwise specified, the numerical range “ab” represents an abbreviated expression for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have already been listed in this specification, and "0-5" is simply a shortened representation of combinations of these numbers. Also, expressing a parameter as an integer ≥ 2 is equivalent to disclosing that this parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0041] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions, and such technical solutions should be considered to be included in the disclosures of this application.

[0042] Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical concepts, and such technical concepts should be considered to be included in the disclosures of this application.

[0043] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, the fact that the method includes steps (a) and (b) means that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, the fact that the method mentioned above may further include step (c) means that step (c) may be added to the method in any order, for example the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), and so on.

[0044] Unless otherwise specified, the terms “includes” and “inclusion” as used in this application may represent an open or closed configuration. For example, the terms “includes” and “inclusion” may mean that other components not listed may be included or inclusion, or that only the listed components may be included or inclusion.

[0045] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following conditions satisfy "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) but B is true (or exists); and both A and B are true (or exist).

[0046] In this application, the terms "multiple" and "multiple types" refer to two or more.

[0047] Unless otherwise specified, terms used in this application have the meanings commonly understood by those skilled in the art.

[0048] Unless otherwise specified, the numerical values ​​of each parameter referred to in this application can be measured using various commonly used test methods in the art, for example, according to the test methods given in the embodiments of this application. Unless otherwise specified, the test temperature for each parameter is 25°C.

[0049] Unless otherwise specified, the ratio parameters in this application are compared only when their units are the same. For example, the ratio of the volume distribution particle sizes of A and B is 1:1, and in this case, the units of the volume distribution particle sizes of A and B are the same.

[0050] The batteries referred to in the embodiments of this application may be a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the batteries referred to in this application may include battery cells, battery modules, or battery packs.

[0051] A battery cell is the smallest unit that makes up a battery and can independently realize the functions of charging and discharging. A battery cell may have a cylindrical, flattened, rectangular parallelepiped, or other shape, and the embodiments of this application are not limited to these. Figure 1 shows a rectangular parallelepiped battery cell 5 as an example.

[0052] When there are multiple battery cells, the multiple battery cells are connected in series, parallel, or series-parallel via busbar members. In some embodiments, the battery may be a battery module, and when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a single battery module. In some embodiments, the battery may be a battery pack, which includes a housing and battery cells, and the battery cells or battery modules are housed within the housing. In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least part of the vehicle's bottom plate, or a portion of the housing may be at least part of the vehicle's cross members and side members.

[0053] In some embodiments, the battery may be an energy storage device. The energy storage device may include an energy storage container, an energy storage electrical cabinet, and the like.

[0054] The battery cells according to the embodiments of this application include, but are not limited to, sodium-ion battery cells, sodium metal battery cells, and sodium metal battery cells without a negative electrode.

[0055] A battery cell generally includes an electrode assembly. The electrode assembly generally includes a positive electrode plate, a negative electrode plate, and a separator located between the positive and negative electrode plates. The electrode assembly may have a wound structure or a laminated structure, and the embodiments of this application are not limited thereto.

[0056] The battery cell may further include an outer casing, which may be used to package the electrode assembly and electrolyte. The outer casing may be a rigid case, such as a rigid plastic case, an aluminum case, or a steel case. The outer casing may be a pouch, such as a bag-shaped pouch. The material of the pouch may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), or polybutylene succinate (PBS).

[0057] In some embodiments, as shown in Figure 2, the casing may include a case 51 and a cover plate 53. The case 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and side plates surround and form a housing cavity. The case 51 has an opening that communicates with the housing cavity, and the cover plate 53 is used to cover the opening and seal the housing cavity. The electrode assembly 52 is packaged in the housing cavity. The number of electrode assemblies 52 included in the battery cell 5 may be one or more and can be adjusted according to the requirements.

[0058] In some embodiments, battery cells may be assembled into battery modules, and the number of battery cells included in a battery module may be multiple, with the specific number being adjusted according to the application and capacity of the battery module. Figure 3 is a schematic diagram of an example battery module 4. As shown in Figure 3, in the battery module 4, multiple battery cells 5 may be arranged sequentially along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, these multiple battery cells 5 may be fixed by fasteners.

[0059] Selectively, the battery module 4 may further include a housing having a housing space, in which a plurality of battery cells 5 are housed.

[0060] In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0061] Figures 4 and 5 are schematic diagrams of an example battery pack 1. As shown in Figures 4 and 5, the battery pack 1 may include a housing and a plurality of battery modules 4 installed inside the housing. The housing includes an upper housing 2 and a lower housing 3, and the upper housing 2 is used to cover the lower housing 3 and to form a sealed space for housing the battery modules 4. The plurality of battery modules 4 may be arranged in the housing in any manner.

[0062] The positive electrode plate contains a positive electrode active material, and the influence of the positive electrode active material's performance on battery performance is extremely important.

[0063] The positive electrode active material according to the embodiment of this application comprises a substrate and a sodium-rich layer formed in situ on the substrate surface, wherein the substrate comprises a sodium-containing layered transition metal oxide, and the sodium-rich layer comprises one or more sodium salts represented by formulas (I) and (II). [ka] m represents an integer from 1 to 8, and n represents an integer from 2 to 20.

[0064] Sodium-containing layered transition metal oxides generally consist of an MO6 octahedral structure formed by a transition metal M and six surrounding oxygen atoms, with sodium ions located between the transition metal layers, forming a layered structure in which MO6 transition metal layers and NaO6 sodium layers are alternately arranged. During the charging and discharging process of a battery, sodium-containing layered transition metal oxides are prone to lattice distortion and phase changes, which inhibit the transport and diffusion of sodium ions. Furthermore, some sodium ions are released onto the material surface, causing side reactions with the electrolyte, resulting in irreversible active sodium loss and simultaneously reducing the battery's cycle stability.

[0065] In the embodiment of this application, the sodium-rich layer in the positive electrode active material is formed in situ on the substrate surface, thereby uniformly dispersing the sodium salt on the substrate surface, reducing direct contact between the substrate and the electrolyte, decreasing side reactions, and further improving the cycle stability of the positive electrode active material.

[0066] The sodium-rich layer contains one or more sodium salts represented by formulas (I) and (II) above, which, as sodium replenishers, provide an additional sodium source during the first charging cycle of the battery (i.e., the battery formation process) and can replenish the loss of activated sodium during the negative electrode film formation process. Therefore, the positive electrode active material according to the embodiments of this application can have a relatively high gram capacity, thereby improving the energy density of the battery.

[0067] During the battery cycle, activated sodium is gradually consumed. The sodium salts represented by formulas (I) and (II) above provide excess activated sodium for storage at the negative electrode, replenishing the loss of activated sodium during the battery cycle and reducing the probability of excessive desorption of sodium ions in the positive electrode active material. This improves the structural stability of the positive electrode active material and enhances the battery's cycle performance.

[0068] The sodium salts represented by equations (I) and (II) above undergo an irreversible sodium desorption process during the first charging cycle of the battery. During the sodium desorption process, the sodium salt further decomposes to produce carbon dioxide, which is then released in gaseous form. The solid remaining after sodium desorption mainly adheres to the substrate surface in the form of elemental carbon, improving electronic conductivity, reducing polarization, and decreasing direct contact between the substrate and the electrolyte. This reduces side reactions and improves the battery's cycle performance.

[0069] Therefore, the positive electrode active material according to the embodiment of this application can improve the energy density and cycle performance of the battery.

[0070] Currently, the positive electrode sodium replenishment process generally involves physically mixing a sodium replenisher with the positive electrode active material as an additive, then adding it to a solvent to produce a slurry and a positive electrode plate, and achieving the purpose of sodium replenishment during the first battery cycle charging process (i.e., the battery chemical formation process). However, because the amount of sodium replenisher used is generally relatively small, there is a situation where the mixing is uneven when it is physically mixed with the positive electrode active material. At the same time, the density and particle size of the sodium replenisher itself have a relatively large impact on the uniformity of the produced positive electrode slurry and positive electrode plate, resulting in a low sodium replenishment effect and relatively poor electrochemical performance and consistency of the produced battery.

[0071] The positive electrode active material according to the embodiment of this application includes a substrate and a sodium-rich layer formed in situ on the substrate surface, thereby enabling a better sodium replenishment effect, improving the battery's cycle performance, and simultaneously providing relatively high consistency among manufactured batteries.

[0072] In some embodiments, m may represent an integer from 1 to 6, selectively an integer from 1 to 4, and further selectively 1 or 2.

[0073] In some embodiments, n may represent an integer from 2 to 10, selectively an integer from 2 to 6, and more selectively 2 or 3.

[0074] In some embodiments, the sodium-rich layer is made of the following sodium salts [ka] It may include one or more of these.

[0075] Selectively, the sodium-rich layer contains the following sodium salts [ka] It may include one or more of them.

[0076] In some embodiments, the thickness of the sodium-rich layer is denoted as h, and the volume distribution particle size Dv50 of the positive electrode active material is denoted as D, and the unit of both is nm, and 0 < h / D ≤ 0.05. For example, h / D may be in the range consisting of any value such as 0.005, 0.008, 0.01, 0.012, 0.015, 0.018, 0.02, 0.022, 0.025, 0.028, 0.03, 0.032, 0.035, 0.038, 0.04, 0.042, 0.045, 0.048, 0.05 or more. Since the voltage plateau of the sodium salt itself is relatively high, its content is relatively large, and when the sodium-rich layer is relatively thick, the sodium salt itself tends to aggregate and form large particles, which increases polarization, further affects the cycle performance of the battery, and may increase the gas generation amount of the battery. By adjusting h / D within the above range, the sodium salt can be uniformly dispersed on the substrate surface with a relatively thin thickness, and the carbon remaining after the sodium salt desodiumates can further improve the conductivity of the positive electrode active material to a certain extent, thereby not only achieving the effect of sodium replenishment, but also not increasing the gas generation amount of the battery, and thereby enabling the battery to have good cycle performance.

[0077] In some embodiments, 0.005 ≤ h / D ≤ 0.05, 0.005 ≤ h / D ≤ 0.04, 0.008 ≤ h / D ≤ 0.03, 0.01 ≤ h / D ≤ 0.025, 0.012 ≤ h / D ≤ 0.022, 0.016 ≤ h / D ≤ 0.020. By adjusting h / D within the above range, the positive electrode active material can be made to have a high gram capacity, and further the positive electrode active material can be made to have relatively high structural stability, and further the battery can be made to have a high energy density and a long cycle life.

[0078] In some embodiments, the thickness of the sodium-rich layer may be 30-120 nm, for example, within a range of 30 nm, 40 nm, 45 nm, 50 nm, 55 nm, 59 nm, 62 nm, 64 nm, 70 nm, 75 nm, 78 nm, 86 nm, 93 nm, 100 nm, 110 nm, 120 nm, or any of the above values.

[0079] In some embodiments, the thickness of the sodium-rich layer may be 40-100 nm, 59-93 nm, or 64-78 nm.

[0080] When the thickness of the sodium-rich layer is within the above range, the positive electrode active material can be given high gram capacity and high cycle stability, and furthermore, the battery can be given high energy density and long cycle life.

[0081] The thickness of the sodium-rich layer has a known meaning in this field and can be measured using instruments and methods known in this field. For example, the positive electrode plate after roll pressing is cut into a sample of a certain size (e.g., a 6 cm x 6 cm square) with scissors, polished with an ion cross-section polishing machine (e.g., IB-19500CP), a sample with the polished cut surface is obtained, then a TEM image is acquired using a transmission electron microscope, 10 locations are randomly selected from the image and the thickness of the sodium-rich layer is tested, and the average value is taken as the test result.

[0082] In some embodiments, the volume distribution particle size Dv50 of the positive electrode active material may be in the range of 2000-8000 nm. When the volume distribution particle size Dv50 of the positive electrode active material is within this range, it is possible to have a relatively high gram capacity and a relatively high compaction density, as well as good ion transport capability, and furthermore, the battery can be given a higher energy density and a longer cycle life.

[0083] The volume distribution particle size Dv50 of the positive electrode active material has a well-known meaning in the art. It represents the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 50%, and can be measured using well-known instruments and methods in the art. For example, it can be easily measured using a laser particle size analyzer by referring to GB / T 19077-2016. The test instrument may be a Mastersizer 2000 type laser particle size analyzer manufactured by Malvern Instruments, UK.

[0084] In some embodiments, the sodium-rich layer may be located on 80%-100% of the surface of the substrate, and may selectively be located on 85%-100%, 90%-100%, or 95%-100% of the surface. This can have a good sodium replenishment effect, further reduce the direct contact between the substrate and the electrolyte, reduce side reactions, improve the cycle stability of the positive electrode active material, and improve the cycle performance of the battery.

[0085] In some embodiments, the positive electrode active material may include one or more of the O3 phase, P2 phase, and P3 phase.

[0086] In some embodiments, the sodium-containing layered transition metal oxide includes one or more of the oxides represented by formula (III), Na x M a A b B c O m Q n Formula (III) 0 < x ≤ 1, 0 < a ≤ 1, 0 ≤ b ≤ 1 / 3, 0 ≤ c ≤ 1 / 3, 1.9 ≤ m ≤ 2, 0 ≤ n ≤ 0.1, M includes one or more of Ni, Mn, Fe, Co, Cu, A includes one or more metal elements of Group IA, IIA, IIIA, IVA, VA, IIB, IIIB, IVB, VB, VIB, B includes one or more non-metal elements of Group IIIA, IVA, VA, VIA, and Q includes one or more non-metal elements of Group VA, VIIA.

[0087] Unless otherwise specified, in the above chemical formulas, when M is two or more elements, the limitation of the numerical range of a above refers not only to the limitation of the stoichiometric number for each type of element that makes up M, but also to the limitation of the sum of the stoichiometric numbers of each element that makes up M. For example, when M is two or more elements M1, M2...Mn, the stoichiometric numbers a1, a2...an of M1, M2...Mn must each be within the numerical range limited for a in this application, and the sum of a1, a2...an must also be within this numerical range. Similarly, in the embodiments of this application, when other elements are two or more elements, the limitation of the numerical range of their stoichiometric numbers also has the same meaning as above.

[0088] M may contain one or more of Ni, Mn, Fe, Co, and Cu. The sodium-containing layered transition metal oxide may be a monocomponent material or a multicomponent material. A "monocomponent material" refers to a material containing only one transition metal M, for example, the transition metal M contains one of Ni, Mn, Fe, Co, and Cu. A "multicomponent material" refers to a material containing at least two transition metals M, for example, the transition metal M contains at least two of Ni, Mn, Fe, Co, and Cu, such as a combination of Mn and Fe, a combination of Mn, Fe, and Ni, or a combination of Mn, Fe, and Cu.

[0089] In some implementations, 0.5 ≤ x ≤ 1, and selectively, 0.66 ≤ x ≤ 1.

[0090] In some embodiments, b is 0.

[0091] In some embodiments, 0 <b≦1 / 3である。

[0092] In some embodiments, c is 0.

[0093] In some embodiments, 0 <c≦1 / 3である。

[0094] In some embodiments, b is 0 and c is 0.

[0095] In some embodiments, 0 < b ≤ 1 / 3 and 0 < c ≤ 1 / 3.

[0096] In some embodiments, 0 ≤ b ≤ 1 / 3, 0 ≤ c ≤ 1 / 3, and 0 < b + c ≤ 1 / 3. When the total content of element A and element B is within an appropriate range, it contributes to further improving the cycle performance and / or rate performance of the battery.

[0097] In some embodiments, A includes one or more elements selected from Li, K, Mg, Ca, Sr, Ba, Zn, La, Sc, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Al, Sn, Ge, Bi, and Sb. This contributes to improving the structural stability of the positive electrode active material and also contributes to improving the cycle performance and / or rate performance of the battery.

[0098] In some embodiments, B includes one or more elements selected from Si, P, B, S, and Se. This contributes to improving the structural stability of the positive electrode active material and also contributes to improving the cycle performance and / or rate performance of the battery.

[0099] In some embodiments, n is 0.

[0100] In some embodiments, 0 < n ≤ 0.1. When the content of element Q is within an appropriate range, it contributes to further improving the cycle performance and / or rate performance of the battery.

[0101] In some embodiments, Q includes one or more elements selected from F, Cl, and N. This contributes to improving the structural stability of the positive electrode active material and also contributes to improving the cycle performance and / or rate performance of the battery.

[0102] The content of each element in the positive electrode active material can be detected by inductively coupled plasma optical emission spectrometry (ICP) referring to EPA 6010D - 2014.

[0103] It should be noted that the shape of the positive electrode active material is not necessarily spherical, but may be sheet-like or random, and the positive electrode active material may be primary particles, secondary particles, or even a mixture thereof.

[0104] The shape of the positive electrode active material can be tested using a scanning electron microscope. For example, refer to JY / T010-1996 for testing. The test instrument may be a ZEISS Sigma 300.

[0105] In some embodiments, the content of free alkaline substances on the surface of the positive electrode active material may be 13% or less, and selectively 10.2% or less, 8.7% or less, 5.2% or less, 3.2% or less, 2.5% or less, 2.0% or less, 1.7% or less, and 1.2% or less. Because the content of free alkaline substances on the surface of the positive electrode active material is relatively low, the positive electrode active material can be given relatively high interfacial stability, which is advantageous in improving the cycle performance and / or rate performance of the battery, and further advantageous in improving the processing performance of the positive electrode slurry and the battery.

[0106] The free alkaline substances on the surface of the positive electrode active material mainly consist of NaOH and Na2CO3, which can be detected by potentiometric titration. The amount of free alkaline substances on the surface differs depending on the type of positive electrode active material.

[0107] In some embodiments, the pH of the positive electrode active material may be 10.0-13.0, and selectively 11.0-12.3. The relatively low pH of the positive electrode active material allows for relatively high interfacial stability, which is advantageous for improving the battery's cycle performance and / or rate performance, and further advantageous for improving the processing performance of the positive electrode slurry and the battery.

[0108] The pH of the positive electrode active material can be tested using a pH meter. For example, it can be tested in the following steps: Take an appropriate amount of positive electrode active material at 25°C and add it to deionized water (mass ratio is 1:9) to prepare a solution, seal it, and stir it in a magnetic stirrer for a certain period of time (e.g., 30 min). After that, place it in a 25°C water bath thermos and let it stand for a certain period of time (e.g., 1.5 h) before testing the pH value.

[0109] In some embodiments, the carbon content of the cathode active material may be 1%-13%, and selectively 2%-12.7%, 4.2%-10.6%, or 6.3%-8.5%. The carbon content of the cathode active material can be tested by a high-frequency infrared carbon-sulfur analyzer (e.g., CS996 series), and the test standard can refer to GB / T 20123-2006.

[0110] [Manufacturing method] The embodiments of this application further provide a method for producing the above-mentioned positive electrode active material, the method being: A step of providing a sodium-containing layered transition metal oxide, wherein the surface of the sodium-containing layered transition metal oxide contains a free alkaline substance, and the alkaline substance contains sodium hydroxide and / or sodium carbonate. A step of providing a solvent and a first reactant, wherein the solvent comprises a polar organic solvent, and the first reactant comprises one or more compounds represented by formulas (1) and (2). [ka] m represents an integer from 1 to 8, and n represents an integer from 2 to 20, and The process includes the steps of: mixing a sodium-containing layered transition metal oxide and a solvent with a first reactant to react the free alkaline substance on the surface of the sodium-containing layered transition metal oxide with the first reactant to form a sodium salt represented by formulas (I) and (II); and then drying the mixture to obtain a positive electrode active material, wherein the positive electrode active material comprises a substrate and a sodium-rich layer formed in situ on the substrate surface, the substrate comprising a sodium-containing layered transition metal oxide, and the sodium-rich layer comprising a sodium salt formed by the reaction of the free alkaline substance on the surface of the sodium-containing layered transition metal oxide with the first reactant, as represented by formulas (I) and (II).

[0111] Sodium-containing layered transition metal oxides are generally obtained by a high-temperature sintering process. In the manufacturing process, the amount of sodium source added to improve yield and compensate for the volatilization of high-temperature sintered Na is generally excessive. As a result, after the high-temperature sintering process is completed, some of the sodium source remains on the surface of the positive electrode active material and reacts with moisture and CO2 in the air to form free alkaline substances such as NaOH and Na2CO3. These alkaline substances cause the positive electrode slurry to gel or harden easily, affecting the coating performance of the positive electrode slurry and the performance of the battery. Furthermore, the free alkaline substances continue to react with moisture and CO2 in the air and the electrolyte, inhibiting the transport and diffusion of sodium ions. This also causes some sodium to desorb from the bulk structure of the positive electrode active material, worsening the stability of the bulk structure. The bulk structure of the positive electrode active material is prone to irreversible phase changes, which affects the capacity of the positive electrode active material and further affects the manufacturing and performance of the battery.

[0112] Currently, the content of free alkaline substances on the surface of the positive electrode active material is generally reduced using water washing or pickling processes. However, these methods reduce the sodium content of the positive electrode active material and irreversibly destroy the bulk structure of the positive electrode active material, leading to a reduction in the gram capacity of the positive electrode active material, deterioration of structural stability, and ultimately affecting the energy density and cycle performance of the battery.

[0113] The first reactive component comprises one or more compounds represented by formulas (1) and (2), which can react with free alkaline substances on the substrate surface, thereby effectively reducing the content of free alkaline substances and simultaneously making it less likely to destroy the bulk structure of the substrate, thereby providing the positive electrode active material with relatively high structural stability.

[0114] The compounds represented by formulas (1) and (2) contain carbonyl anions and, after reacting with free alkaline substances on the substrate surface, can further generate sodium salts represented by formulas (I) and (II) in situ on the substrate surface, and the sodium salts can be uniformly dispersed on the substrate surface. The sodium salts represented by formulas (I) and (II) can serve as sodium replenishers, providing an additional sodium source during the first cycle charging process of the battery (i.e., the battery formation process), replenishing the loss of active sodium during the negative electrode film formation process, and further providing excess active sodium for storage at the negative electrode, thereby replenishing the loss of active sodium during the battery cycle process and improving the cycle stability of the positive electrode active material. The sodium salts represented by equations (I) and (II) undergo an irreversible sodium desorption process during the first charging cycle of the battery. During the sodium desorption process, the sodium salt further decomposes to produce carbon dioxide, which is then released in gaseous form. The solid remaining after sodium desorption mainly adheres to the substrate surface in the form of elemental carbon, improving electronic conductivity, reducing polarization, and decreasing direct contact between the substrate and the electrolyte. This reduces side reactions and improves the battery's cycle performance.

[0115] Currently, the positive electrode sodium replenishment process generally involves physically mixing a sodium replenisher with the positive electrode active material as an additive, then adding it to a solvent to produce a slurry and a positive electrode plate, and achieving the purpose of sodium replenishment during the first battery cycle charging process (i.e., the battery chemical formation process). However, because the amount of sodium replenisher used is generally relatively small, there is a situation where the mixing is uneven when it is physically mixed with the positive electrode active material. At the same time, the density and particle size of the sodium replenisher itself have a relatively large impact on the uniformity of the produced positive electrode slurry and positive electrode plate, resulting in a low sodium replenishment effect and relatively poor electrochemical performance and consistency of the produced battery. The manufacturing method according to the embodiment of this application can uniformly disperse the sodium salt formed by the reaction on the substrate surface, thereby achieving a better sodium replenishment effect, improving the energy density and cycle performance of the battery, and simultaneously providing relatively high consistency to the produced battery.

[0116] The manufacturing method according to the embodiments of this application can reduce the content of free alkaline substances on the substrate surface, while simultaneously being less likely to destroy the bulk structure of the substrate. Furthermore, the manufacturing method according to the embodiments of this application can generate uniformly dispersed sodium salts in situ on the substrate surface. These sodium salts can reduce polarization, provide an additional sodium source, replenish the loss of activated sodium during the negative electrode film formation process, and provide excess activated sodium for storage in the negative electrode, thereby replenishing the loss of activated sodium during the battery cycle process. Therefore, the positive electrode active material obtained by the manufacturing method according to the embodiments of this application can improve the energy density and cycle performance of the battery, and further improve the consistency of the battery.

[0117] The thickness of the sodium-rich layer on the substrate surface of the positive electrode active material and the sodium salt content are related to parameters such as the type of the first reactant, the amounts of the three components used (i.e., sodium-containing layered transition metal oxide, solvent, and first reactant), and the drying temperature.

[0118] By adjusting the molar ratio of the first reactant to the sodium-containing layered transition metal oxide, the reaction rate between the first reactant and the sodium-containing layered transition metal oxide and the solubility of the resulting sodium salt can be adjusted. This allows for adjustment of the thickness and morphology of the sodium-rich layer on the substrate surface of the positive electrode active material, as well as adjustment of the sodium salt content and the degree of sodium replenishment in the positive electrode active material.

[0119] When the molar ratio of the first reactant to the sodium-containing layered transition metal oxide is high, the reaction rate between the first reactant and the sodium-containing layered transition metal oxide is relatively fast, the solubility of the resulting sodium salt in the solvent is relatively high, and the sodium-rich layer on the substrate surface of the resulting positive electrode active material is relatively thick. This reduces the content of free alkaline substances and allows for a relatively high degree of sodium replenishment.

[0120] In some embodiments, the molar ratio of the first reactant to the sodium-containing layered transition metal oxide may be 0.1:1 or less. This reduces the occurrence of situations in which the first reactant corrodes the substrate and contributes to the formation and adhesion of a complete sodium-rich layer to the substrate surface, reducing direct contact between the substrate and the electrolyte, reducing side reactions, and thereby providing the manufactured positive electrode active material with high structural stability and high gram capacity.

[0121] In some embodiments, the molar ratio of the first reactant to the sodium-containing layered transition metal oxide may be 0.01:1 to 0.095:1, 0.02:1 to 0.08:1, 0.02:1 to 0.07:1, or 0.03:1 to 0.06:1. When the molar ratio of the first reactant to the sodium-containing layered transition metal oxide is within the above range, the content of free alkaline substances on the substrate surface can be effectively reduced, the positive electrode active material can be given an appropriate degree of sodium replenishment, and furthermore, the positive electrode active material can be given a high gram capacity and high structural stability, thereby enabling the battery to have a high energy density and a long cycle life.

[0122] In some embodiments, m may represent an integer from 1 to 6, selectively an integer from 1 to 4, and further selectively 1 or 2.

[0123] In some embodiments, n may represent an integer from 2 to 10, selectively an integer from 2 to 6, and more selectively 2 or 3.

[0124] In some embodiments, the first reaction component may include one or more of the following compounds: [ka]

[0125] Selectively, the first reactant is the following compound [ka] It may include one or more of these.

[0126] When the first reactant is within the above range, it is possible to effectively reduce the amount of free alkaline material on the substrate surface, provide the positive electrode active material with an appropriate amount of sodium replenishment, and give the positive electrode active material a high gram capacity. In addition, it is possible to reduce the polarization of the positive electrode active material and give the positive electrode active material high structural stability. As a result, when the first reactant is within the above range, the battery can have a high energy density and a long cycle life.

[0127] In some embodiments, the polar organic solvent may include one or more of alcoholic solvents, ketoneic solvents, nitrile solvents, and etheric solvents. Selectively, the polar organic solvent may include one or more of ethanol, methanol, acetone, N-methylpyrrolidone (NMP), acetonitrile, tetrahydrofuran, and 1,4-dioxane.

[0128] In some embodiments, the volume fraction of the polar organic solvent may be 80% to 100% based on the total volume of the solvent.

[0129] In some examples, the solvent may further contain water, and the volume fraction of water is 20% or less of the total volume of the solvent.

[0130] In some embodiments, the mass ratio of sodium-containing layered transition metal oxide to solvent may be between 10:100 and 25:100, and selectively between 15:100 and 22:100. When the mass ratio of sodium-containing layered transition metal oxide to solvent is within the above range, the content of free alkaline substances on the substrate surface can be effectively reduced, the positive electrode active material can be given an appropriate degree of sodium replenishment, and furthermore, the positive electrode active material can be given high gram capacity and high structural stability, thereby enabling the battery to have high energy density and long cycle life.

[0131] The drying method may be one known in the art, and the embodiments of this application are not limited thereto. In some embodiments, drying may be spray drying. Spray drying contributes to more uniform dispersion of the sodium salt formed after the reaction on the substrate surface and further contributes to adjusting the sodium salt content on the substrate surface.

[0132] By adjusting the drying temperature, the reaction rate between the first reactant and the sodium-containing layered transition metal oxide, as well as the solubility of the resulting sodium salt, can be adjusted. This allows for adjustment of the thickness and morphology of the sodium-rich layer on the substrate surface of the positive electrode active material, as well as the sodium salt content and the degree of sodium replenishment in the positive electrode active material.

[0133] When the drying temperature is relatively high, the reaction rate between the first reactant and the sodium-containing layered transition metal oxide is relatively fast, the solubility of the resulting sodium salt in the solvent is relatively high, and the sodium-rich layer on the substrate surface of the resulting positive electrode active material is relatively thick. This reduces the content of free alkaline substances and allows for a relatively high degree of sodium replenishment.

[0134] In some embodiments, the drying temperature may be below the boiling point of the polar organic solvent, and selectively, 10°C ≤ boiling point of polar organic solvent - drying temperature ≤ 30°C. When the drying temperature is within the above range, the content of free alkaline substances on the substrate surface can be effectively reduced, the positive electrode active material can be given an appropriate degree of sodium replenishment, and furthermore, the positive electrode active material can be given high gram capacity and high structural stability, thereby enabling the battery to have a high energy density and a long cycle life.

[0135] In some embodiments, the sodium-containing layered transition metal oxide comprises one or more oxides represented by formula (III), Na x M a A b B c O m Qn Formula (III) 0 < x ≤ 1, 0 < a ≤ 1, 0 ≤ b ≤ 1 / 3, 0 ≤ c ≤ 1 / 3, 1.9 ≤ m ≤ 2, 0 ≤ n ≤ 0.1, where M contains one or more of Ni, Mn, Fe, Co, Cu; A contains one or more metal elements from Group IA, IIA, IIIA, IVA, VA, IIB, IIIB, IVB, VB, VIB; B contains one or more non-metal elements from Group IIIA, IVA, VA, VIA; and Q contains one or more non-metal elements from Group VA, VIIA.

[0136] Unless otherwise specified, in the above chemical formula, when M is two or more elements, the limitation of the above a numerical range is not only the limitation of the stoichiometric number for each type of element that becomes M, but also the limitation of the sum of the stoichiometric numbers of each element that becomes M. For example, when M is two or more elements M1, M2... Mn, the respective stoichiometric numbers a1, a2... an of M1, M2... Mn must each be within the numerical range limited for a in this application, and the sum of a1, a2... an must also be within this numerical range. Similarly, in the examples of this application, when other elements are two or more elements, the limitation of the numerical range of their stoichiometric numbers also has the above meaning.

[0137] M may contain one or more of Ni, Mn, Fe, Co, Cu. The sodium-containing layered transition metal oxide may be a single-component material or a multi-component material. "Single-component material" refers to a material containing only one transition metal M. For example, the transition metal M contains one of Ni, Mn, Fe, Co, Cu. "Multi-component material" refers to a material containing at least two transition metals M. For example, the transition metal M contains at least two of Ni, Mn, Fe, Co, Cu, such as a combination of Mn and Fe, a combination of Mn, Fe and Ni, a combination of Mn, Fe and Cu, etc.

[0138] In some embodiments, 0.5 ≤ x ≤ 1, and optionally, 0.66 ≤ x ≤ 1.

[0139] In some embodiments, b is 0.

[0140] In some embodiments, 0 < b ≤ 1 / 3.

[0141] In some embodiments, c is 0.

[0142] In some embodiments, 0 < c ≤ 1 / 3.

[0143] In some embodiments, b is 0 and c is 0.

[0144] In some embodiments, 0 < b ≤ 1 / 3 and 0 < c ≤ 1 / 3.

[0145] In some embodiments, 0 ≤ b ≤ 1 / 3, 0 ≤ c ≤ 1 / 3, and 0 < b + c ≤ 1 / 3. When the total content of element A and element B is within an appropriate range, it contributes to further improving the cycle performance and / or rate performance of the battery.

[0146] In some embodiments, A contains one or more elements selected from Li, K, Mg, Ca, Sr, Ba, Zn, La, Sc, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Al, Sn, Ge, Bi, and Sb. This contributes to improving the structural stability of the positive electrode active material and also contributes to improving the cycle performance and / or rate performance of the battery.

[0147] In some embodiments, B contains one or more elements selected from Si, P, B, S, and Se. This contributes to improving the structural stability of the positive electrode active material and also contributes to improving the cycle performance and / or rate performance of the battery.

[0148] In some embodiments, n is 0.

[0149] In some embodiments, 0 < n ≤ 0.1. When the content of element Q is within an appropriate range, it contributes to further improving the cycle performance and / or rate performance of the battery.

[0150] In some embodiments, Q comprises one or more elements from F, Cl, and N. This contributes to improving the structural stability of the positive electrode active material and to improving the battery's cycle performance and / or rate performance.

[0151] It should be noted that the shape of sodium-containing layered transition metal oxides is not necessarily spherical, but can be sheet-like or random, and the sodium-containing layered transition metal oxides may be primary particles, secondary particles, or even mixtures thereof.

[0152] In some examples, the volume distribution particle size Dv50 of sodium-containing layered transition metal oxides is 2000-8000 nm.

[0153] In some embodiments, the sodium-containing layered transition metal oxide comprises one or more of the O3 phase, P2 phase, and P3 phase.

[0154] In some embodiments, sodium-containing layered transition metal oxides can be produced using methods known in the art, such as by solid-state sintering, or by purchasing commercially available products.

[0155] Unless otherwise specified, all raw materials used in the above manufacturing methods can be purchased commercially.

[0156] [Positive electrode plate] The embodiments of this application further provide positive electrode plates.

[0157] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, the positive electrode film layer including a positive electrode active material as described in this application or a positive electrode active material produced by a manufacturing method as described in this application. The positive electrode current collector has two opposing surfaces in its thickness direction, and the positive electrode film layer is provided on one or both of the two opposing surfaces of the positive electrode current collector.

[0158] In some embodiments, the content of the positive electrode active material in the positive electrode film layer is 50 wt% to 99 wt%, and selectively 85 wt% to 99 wt%, based on the total weight of the positive electrode film layer.

[0159] The positive electrode film layer may further contain other positive electrode active materials known in the art, including, but not limited to, one or more of the following: fluorides, sulfides, phosphates, pyrophosphates, metal-organoflames / metal-hexacyanides, and organic compounds. These other positive electrode active materials may be used individually or in combination of two or more.

[0160] In some embodiments, the positive electrode film layer further selectively comprises a positive electrode conductive agent. This application does not particularly limit the type of positive electrode conductive agent, and for example, the positive electrode conductive agent may include one or more of the following: superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0161] In some embodiments, the positive electrode film layer further selectively includes a positive electrode adhesive. This application is not particularly limited to the type of positive electrode adhesive, and as an example, the positive electrode adhesive may include one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene ternary copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene ternary copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorine-containing acrylate resin, styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic acid resin (e.g., polyacrylate PAA, polymethacrylate PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0162] In some embodiments, the positive electrode current collector may be a metal foil sheet or a composite current collector. Aluminum foil can be used as an example of a metal foil sheet. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. For example, the metal material may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0163] The positive electrode film layer is generally obtained by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is generally formed by dispersing a positive electrode active material, a selective conductive agent, a selective adhesive, and any other components in a solvent and stirring them uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP).

[0164] [Negative electrode plate] The battery cell includes a negative electrode plate. The structure and composition of the negative electrode plate may be selected according to the type of battery cell, and the embodiments of this application are not limited thereto.

[0165] In some embodiments, the negative electrode plate may include a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector and containing a negative electrode active material. For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode film layer is provided on one or both of the two opposing surfaces of the negative electrode current collector.

[0166] The negative electrode active material may be a material known in this field, for example, the negative electrode active material may include, but is not limited to, one or more of soft carbon, hard carbon, and mesocarbon microbeads.

[0167] In some embodiments, the negative electrode film layer further selectively comprises a negative electrode conductive agent. This application does not particularly limit the type of negative electrode conductive agent, and for example, the negative electrode conductive agent may include one or more of the following: superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0168] In some embodiments, the negative electrode film layer further selectively includes a negative electrode adhesive. This application is not particularly limited to the type of negative electrode adhesive, and as an example, the negative electrode adhesive may include one or more of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic acid resin (e.g., polyacrylate PAA, polymethacrylate PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0169] In some embodiments, the negative electrode film layer may further selectively include other additives. For example, the other additives may include thickeners such as sodium carboxymethylcellulose (CMC), PTC thermistor materials, etc.

[0170] The negative electrode film layer is generally obtained by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is generally formed by dispersing a negative electrode active material, a selective conductive agent, a selective adhesive, and other selective auxiliary agents in a solvent and stirring them uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0171] The negative electrode plate does not exclude any additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode plate may further include a conductive undercoating (e.g., composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and installed on the surface of the negative electrode current collector, and in some embodiments, the negative electrode plate may further include a protective layer covering the surface of the negative electrode film layer.

[0172] In some embodiments, the negative electrode plate may include a negative electrode current collector and a metal layer placed on at least one surface of the negative electrode current collector, wherein the metal material in the metal layer may include one or more of pure sodium and sodium alloys.

[0173] Sodium alloys may be alloys formed from metallic sodium with other metallic or nonmetallic elements. For example, the other metallic elements in a sodium alloy may include one or more of tin, zinc, aluminum, magnesium, silver, gold, gallium, indium, and platinum, and the nonmetallic elements in a sodium alloy may include one or more of boron, carbon, and silicon.

[0174] In some embodiments, the negative electrode plate may be made of a sodium sheet (foil) or a sodium alloy sheet (foil).

[0175] In some embodiments, the negative electrode plate may consist only of a negative electrode current collector, which is then assembled to form a sodium metal battery cell without a negative electrode.

[0176] In some embodiments, the negative electrode current collector may include a metal foil sheet, a three-dimensional porous current collector, or a composite current collector. Examples of metal foil sheets include copper foil, copper alloy foil, nickel foil, and nickel alloy foil. Examples of three-dimensional porous current collectors include copper mesh, nickel mesh, foamed copper, and foamed nickel. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. For example, the metal material may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0177] [Electrolyte] A battery cell includes an electrolyte. This application does not specifically limit the type of electrolyte, which can be selected according to the needs. For example, the electrolyte may include one or more selected from solid electrolytes and liquid electrolytes (i.e., electrolyte solutions).

[0178] In some embodiments, the electrolyte is an electrolyte solution, which comprises an electrolyte salt and a solvent.

[0179] The type of electrolyte salt is not specifically limited and can be selected according to actual needs. In some embodiments, the electrolyte salt may include one or more of NaPF6, NaClO4, NaBCl4, NaSO3CF3, and Na(CH3)C6H4SO3.

[0180] The type of solvent is not specifically limited and can be selected according to actual needs. In some embodiments, the solvent may include, for example, one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0181] In some embodiments, the electrolyte further selectively includes additives. For example, the additives may include negative electrode film forming additives, positive electrode film forming additives, and further additives that can improve some of the battery's performance characteristics, such as additives that improve the battery's overcharge performance, additives that improve the battery's high-temperature performance, and additives that improve the battery's low-temperature output performance.

[0182] [Separator] Battery cells that use electrolytes, and some battery cells that use solid electrolytes, also include a separator. The separator is placed between the positive and negative electrodes and primarily serves to prevent internal short circuits.

[0183] This application does not particularly limit the type of separator, and any known porous structure separator having good chemical and mechanical stability may be selected.

[0184] In some embodiments, the separator material may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film. When the separator is a multilayer composite film, the materials of each layer may be the same or different.

[0185] Methods for manufacturing battery cells are known. In some embodiments, a battery cell can be formed by assembling a positive electrode plate, a separator, a negative electrode plate, and an electrolyte. For example, the positive electrode plate, separator, and negative electrode plate can be formed into an electrode assembly through a winding process and / or a lamination process, the electrode assembly is placed in an outer casing, dried, and then the electrolyte is injected. A battery cell is then obtained through processes such as vacuum packaging, settling, chemical formation, and shaping. Multiple battery cells may further constitute a battery module by series connection, parallel connection, or series-parallel connection. Multiple battery modules may further constitute a battery pack via series connection, parallel connection, or series-parallel connection. In some embodiments, multiple battery cells may directly constitute a battery pack.

[0186] power consumption equipment Embodiments of this application further provide a power consumption device including a battery according to embodiments of this application. The battery can serve as the power source for the power consumption device, or it can serve as the energy storage unit for the power consumption device. The power consumption device may be, but is not limited to, mobile devices (e.g., mobile phones, tablet computers, laptop computers, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0187] The power consumption device may select a specific type of battery according to its usage needs, for example, a battery cell, a battery module, or a battery pack.

[0188] Figure 6 is a schematic diagram of an example power consumption device. This power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the demand for high power output and high energy density of this power consumption device, a battery pack or battery module may be used.

[0189] Other examples of power-consuming devices include mobile phones, tablet computers, and laptop computers. These power-consuming devices are generally required to be thin, and may use battery cells as their power source.

[0190] Examples The following examples provide a more detailed description of the contents disclosed in this application, and these examples are for illustrative purposes only, as it will be obvious to those skilled in the art that various modifications and changes can be made within the scope of the contents disclosed in this application. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are based on mass, and all reagents used in the examples can be obtained commercially or synthesized according to conventional methods and can be used directly without further processing, and all instruments used in the examples can be obtained commercially.

[0191] Comparative Example 1 (1) Manufacturing of positive electrode active material Na2CO3, Fe2O3, NiO, and MnO2 were weighed in a molar ratio of Na:Fe:Ni:Mn of 1:0.3:0.3, then ball-milled to homogenize the mixture. The ball-milled mixture was placed in a sintering furnace and heated from 25°C to 800°C at a heating rate of 5°C / min under an air atmosphere, and maintained at a constant temperature for 15 hours. After completion, it was allowed to cool naturally to 25°C to produce layered transition metal oxide NaFe. 1 / 3 Ni 1 / 3 Mn 1 / 3 O2 was obtained, and the volume distribution particle size Dv50 was 4000 nm.

[0192] (2) Manufacturing of positive electrode plates The manufactured positive electrode active material, conductive agent Super P carbon black, and adhesive polyvinylidene fluoride (PVDF) were polished and uniformly mixed in a weight ratio of 90:10:10. An appropriate amount of solvent N-methylpyrrolidone (NMP) was added and the mixture was uniformly stirred to obtain a positive electrode slurry. The positive electrode slurry was uniformly applied to the aluminum foil of the positive electrode current collector, and then dried and cold-pressed to obtain a positive electrode plate. The application amount was 0.27 g / 1540.25 mm 2 That was the case.

[0193] (3) Manufacturing of negative electrode plates The negative electrode active material, hard carbon, the conductive agent carbon black Super P, the adhesive styrene-butadiene rubber (SBR), and the thickener sodium hydroxymethylcellulose (CMC) were dissolved in deionized water as a solvent in a weight ratio of 96.2:0.8:0.8:1.2, and a negative electrode slurry was obtained by using a vacuum stirrer. The negative electrode slurry was uniformly applied to the copper foil of the negative electrode current collector, air-dried, then transferred to a 120°C oven for 1 hour, followed by cold pressing and slitting to obtain the negative electrode plate. The application amount was 0.17 g / 1540.25 mm 2 That was the case.

[0194] (4) Manufacturing of electrolyte In a glove box under an argon gas atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were uniformly mixed in a volume ratio of 3:7, and then NaPF6 was dissolved in the above organic solvent to prepare an electrolyte with a mass fraction of 12.5%.

[0195] (5) Battery manufacturing A positive electrode plate, a separator (a polypropylene film with a thickness of 12 μm), and a negative electrode plate were sequentially laminated and wound to obtain an electrode assembly. The electrode assembly was placed inside the outer casing, dried, and then an electrolyte solution was injected to obtain a battery.

[0196] Comparative Example 2 Aside from the manufacturing process of the positive electrode plates, the battery manufacturing process is the same as in Comparative Example 1.

[0197] (6) Manufacturing of positive electrode plates The positive electrode active material, conductive agent carbon black Super P, adhesive polyvinylidene fluoride (PVDF), and sodium salt N2 (as shown in Table 1) produced in Comparative Example 1 were polished and uniformly mixed in a weight ratio of 90:10:10:5. An appropriate amount of solvent N-methylpyrrolidone (NMP) was added and the mixture was uniformly stirred to obtain a positive electrode slurry. The positive electrode slurry was uniformly applied to the aluminum foil of the positive electrode current collector, and then dried and cold-pressed to obtain a positive electrode plate. The application amount was 0.27 g / 1540.25 mm 2 That was the case.

[0198] Sodium salt N2 is prepared by the following method: 0.01 mol of compound H2 (shown in Table 1) is taken and dissolved in 30 ml of deionized water to prepare solution A; 0.08 mol of sodium hydroxide is taken and dissolved in 30 ml of deionized water to prepare solution B; solution B is slowly added dropwise to solution A to form a precipitate, which is then filtered by suction and dried to obtain sodium salt N2.

[0199] Examples 1-18 Aside from the manufacturing process of the positive electrode active material, the battery manufacturing process is the same as in Comparative Example 1.

[0200] (1) Manufacturing of positive electrode active material Layered transition metal oxide NaFe produced in Comparative Example 1 1 / 3 Ni 1 / 3 Mn 1 / 3 O2 was added to the solvents and first reaction components shown in Tables 1 and 2, and after uniform stirring, spray drying was performed, with the exhaust port temperature (drying temperature) as shown in Table 2. After completion, a layered transition metal oxide with a sodium salt coating on the surface, as shown in Tables 1 and 2, was obtained. Layered transition metal oxide NaFe 1 / 3 Ni 1 / 3 Mn 1 / 3 The mass ratio of O2 to solvent is 20:100, and the first reactant is layered transition metal oxide NaFe. 1 / 3 Ni 1 / 3 Mn 1 / 3 The molar ratio with O2 is as shown in Table 2, where D represents the volume distribution particle size Dv50 of the positive electrode active material produced in Examples 1 to 18, and the unit is nm.

[0201] [Table 1]

[0202] Test section (1) Thickness test of sodium-rich layer The manufactured positive electrode plate was cut into 6 cm x 6 cm square samples using scissors, polished using an ion cross-section polishing machine (e.g., IB-19500CP), and a sample with the polished cross-section was obtained. A TEM image was acquired using a transmission electron microscope, and 10 locations were randomly selected from the image to test the thickness of the sodium-rich layer, with the average value being used as the test result.

[0203] (2) Test for the content of free alkaline substances on the surface of the positive electrode active material At 25°C, 20 ± 0.5 g of the prepared positive electrode active material powder was weighed and placed in a 250 ml iodine volumetric flask. 150 ml of anhydrous ethanol was added, and the mixture was stirred at 1200 RPM for 60 min. The flask was then sealed and allowed to stand for 10 min. After that, the mixture was filtered by vacuum suction using a microfiltration membrane (e.g., a 0.45 μm polytetrafluoroethylene microfiltration membrane). A certain amount of filtrate was transferred and titrated with a 0.05 mol / L hydrochloric acid-ethanol standard solution using a potentiometric titrator to obtain the content of free alkaline substances on the surface of the positive electrode active material.

[0204] The free alkaline substances on the surface of the positive electrode active material mainly refer to NaOH and Na2CO3.

[0205] (3) pH value test of positive electrode active material At 25°C, 2g of the prepared positive electrode active material was taken and added to 18g of deionized water to prepare a solution. After sealing the solution, it was placed in a magnetic stirrer and stirred for 30 minutes. After completion, it was placed in a 25°C water bath incubator and allowed to stand for 1.5 hours before the pH value was tested.

[0206] (4) Test for carbon content of positive electrode active material At 25°C, 5g of the prepared positive electrode active material was weighed and placed in a dedicated crucible. An appropriate amount of flux (e.g., a mixture of pure iron flux, pure tin flux, and pure tungsten flux) was added and mixed uniformly. The carbon content of the positive electrode active material was then obtained by testing with a high-frequency infrared carbon-sulfur analyzer (e.g., CS996 series). The test standards can be referenced from GB / T 20123-2006.

[0207] (5) Chemical and capacity testing of batteries At 45°C, the manufactured battery (a battery without a chemical conversion process) was charged to 4.2V with a constant current of 0.05C, and the charge capacity at this time was denoted as C0. After the battery was left to stand at 25°C for 5 minutes, it was discharged to 1.5V with a constant current of 0.1C, and the discharge capacity at this time was denoted as D0.

[0208] The charge capacity in grams (mAh / g) of the positive electrode active material in the first cycle = charge capacity C0 / mass of the positive electrode active material.

[0209] (6) Battery cycle performance test At 25°C, the battery after the chemical formation and capacity test in step (5) above was charged to 4.2V with a constant current of 0.33C, and the constant voltage charging was continued until the current was 0.05C. At this time, the battery was in a fully charged state, and the charge capacity at this time was recorded as C1. After letting the battery stand for 5 minutes, it was discharged to 1.5V with a constant current of 0.33C, and the discharge capacity at this time was recorded as D1. A cycle charge-discharge test was performed on the battery according to the above method, and the discharge capacity after each cycle was recorded until the discharge capacity of the battery decreased to 80% of D1, and the cycle performance of the battery was characterized by the number of cycles at this time.

[0210] The results of the above tests are shown in Table 2.

[0211] As can be seen from the test results in Table 2, the positive electrode active material according to the embodiment of this application is a layered transition metal oxide with sodium salts formed in situ on its surface. The sodium salts can reduce the amount of free alkaline substances on the surface of the positive electrode active material, lower the pH of the positive electrode active material, and further improve the gram capacity of the positive electrode active material, thereby improving the battery's cycle performance.

[0212] As can be seen from the test results of Examples 1-18 and Comparative Example 2, when sodium salt is added as an additive to the positive electrode active material and then added to a solvent to manufacture a slurry and a positive electrode plate, the sodium replenishment effect of the sodium salt is poor and the battery cycle performance is poor. This is because the amount of sodium salt used is generally relatively small, and when it is physically mixed with the positive electrode active material, the mixing is uneven. At the same time, the density and particle size of the sodium salt itself have a relatively large impact on the uniformity of the manufactured positive electrode slurry and positive electrode plate, and further affect the sodium replenishment effect and the battery cycle performance.

[0213] Figure 7 is an energy-dispersive X-ray spectroscopy (EDS) image of the positive electrode active material produced in Example 2. The positive electrode active material includes a substrate and a sodium-rich layer formed in situ on the substrate surface, with the thickness of the sodium-rich layer denoted as h. As can be seen from Figure 7, carbon elements are uniformly distributed on the substrate surface, and the sodium salts in the sodium-rich layer are uniformly attached to the substrate surface. This effectively reduces direct contact between the substrate and the electrolyte, reduces side reactions, and improves the battery's cycle performance.

[0214] It should be noted that this application is not limited to the embodiments described above. The embodiments described above are merely illustrative, and any embodiments that have substantially the same configuration as the technical idea and produce the same effects within the scope of the technical proposal of this application are included within the scope of the technical proposal. Furthermore, other methods that are constructed by adding various modifications to the embodiments that a person skilled in the art could conceive of, and by combining some of the components of the embodiments, are also included within the scope of this application, without departing from the spirit of this application. [Table 2A] [Table 2B] [Table 2C] [Explanation of Symbols]

[0215] 1: Battery pack, 2: Upper casing, 3: Lower casing, 4: Battery module, 5: Battery cell, 51: Case, 52: Electrode assembly, 53: Cover plate.

Claims

1. A positive electrode active material comprising a substrate and a sodium-rich layer formed in situ on the surface of the substrate, wherein the substrate comprises a sodium-containing layered transition metal oxide, and the sodium-rich layer comprises one or more sodium salts represented by formulas (I) and (II), 【Chemistry 1】 m represents an integer from 1 to 8, and n represents an integer from 2 to 20; these are the positive electrode active materials.

2. The sodium-rich layer contains the following sodium salts 【Chemistry 2】 Includes one or more of the following: Selectively, the sodium-rich layer contains the following sodium salts 【Transformation 3】 The positive electrode active material according to claim 1, comprising one or more of the above.

3. The positive electrode active material according to claim 1 or 2, wherein the thickness of the sodium-rich layer is denoted as h, and the volume distribution particle size Dv50 of the positive electrode active material is denoted as D, both units being nm, and 0.005 ≤ h / D ≤ 0.05, and selectively 0.01 ≤ h / D ≤ 0.

025.

4. The thickness of the sodium-rich layer is 30-120 nm, selectively 40-100 nm, and / or The positive electrode active material according to claim 3, wherein the volume distribution particle size Dv50 of the positive electrode active material is 2000-8000 nm.

5. The sodium-rich layer is located on 80%–100% of the surface of the substrate, selectively located on 95%–100% of the surface, and / or The positive electrode active material comprises one or more of the O3 phase, P2 phase, and / or, The content of free alkaline substances on the surface of the positive electrode active material is 13% or less, selectively 3.2% or less, and / or The pH of the positive electrode active material is 10.0–13.0, selectively 11.0–12.3, and / or The positive electrode active material according to any one of claims 1 to 4, wherein the carbon content of the positive electrode active material is 1% to 13%, and selectively 6.3% to 8.5%.

6. The sodium-containing layered transition metal oxide comprises one or more oxides represented by formula (III), Na ｘ M ａ A ｂ B ｃ O ｍ Q ｎ Formula (III) 0 < x ≤ 1, 0 < a ≤ 1, 0 ≤ b ≤ 1 / 3, 0 ≤ c ≤ 1 / 3, 1.9 ≤ m ≤ 2, 0 ≤ n ≤ 0.1, M includes one or more of Ni, Mn, Fe, Co, and Cu. A contains one or more metallic elements from Group IA, Group IIA, Group IIIA, Group IVA, Group VA, Group IIB, Group IIIB, Group IVB, Group VB, and Group VIB, and selectively contains one or more elements from Li, K, Mg, Ca, Sr, Ba, Zn, La, Sc, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Al, Sn, Ge, Bi, and Sb. B contains one or more nonmetallic elements from Group IIIA, Group IVA, Group VA, and Group VIA, and selectively contains one or more elements from Si, P, B, S, and Se. Q comprises one or more nonmetallic elements from Group VA and Group VIIA, and selectively comprises one or more elements from F, Cl, and N, as described in any one of claims 1 to 5.

7. A method for producing a positive electrode active material, A step of providing a sodium-containing layered transition metal oxide, wherein the surface of the sodium-containing layered transition metal oxide contains a free alkaline substance, and the alkaline substance contains sodium hydroxide and / or sodium carbonate. A step of providing a solvent and a first reaction component, wherein the solvent includes a polar organic solvent, and the first reaction component includes one or more compounds represented by formulas (1) and (2). 【Chemistry 4】 Steps where m represents an integer from 1 to 8, and n represents an integer from 2 to 20, The process includes the steps of mixing the sodium-containing layered transition metal oxide, the solvent, and the first reaction component to react the free alkaline substance on the surface of the sodium-containing layered transition metal oxide with the first reaction component to form a sodium salt, and then drying the mixture to obtain a positive electrode active material. A method for producing a positive electrode active material, wherein the positive electrode active material comprises a substrate and a sodium-rich layer formed in situ on the surface of the substrate, the substrate comprises a sodium-containing layered transition metal oxide, and the sodium-rich layer comprises a sodium salt formed by the reaction of a free alkaline substance on the surface of the sodium-containing layered transition metal oxide with the first reaction component.

8. The molar ratio of the first reaction component to the sodium-containing layered transition metal oxide is 0.1:1 or less, selectively between 0.02:1 and 0.07:1, and / or The method according to claim 7, wherein the mass ratio of the sodium-containing layered transition metal oxide to the solvent is 10:100 to 25:100, and selectively 15:100 to 22:

100.

9. The first reaction component is the following compound 【Transformation 5】 Includes one or more of the following: Selectively, the first reaction component is the following compound 【Transformation 6】 The method according to claim 7 or 8, comprising one or more of the above.

10. The drying temperature is below the boiling point of the polar organic solvent, and selectively such that 10°C ≤ boiling point of the polar organic solvent - drying temperature ≤ 30°C, and / or The method according to any one of claims 7 to 9, wherein the drying is spray drying.

11. The polar organic solvent comprises one or more of the following: alcohol-based solvents, ketone-based solvents, nitrile-based solvents, and ether-based solvents, and selectively comprises one or more of the following: ethanol, methanol, acetone, N-methylpyrrolidone, acetonitrile, tetrahydrofuran, and 1,4-dioxane, and / or The volume fraction of the polar organic solvent is 80% to 100% and / or, based on the total volume of the solvent. The method according to any one of claims 7 to 10, wherein the solvent further contains water, and the volume fraction of the water is 20% or less with respect to the total volume of the solvent.

12. The sodium-containing layered transition metal oxide comprises one or more oxides represented by formula (III), Na ｘ M ａ A ｂ B ｃ O ｍ Q ｎ Formula (III) 0 < x ≤ 1, 0 < a ≤ 1, 0 ≤ b ≤ 1 / 3, 0 ≤ c ≤ 1 / 3, 1.9 ≤ m ≤ 2, 0 ≤ n ≤ 0.1, M includes one or more of Ni, Mn, Fe, Co, and Cu. A contains one or more metallic elements from Group IA, Group IIA, Group IIIA, Group IVA, Group VA, Group IIB, Group IIIB, Group IVB, Group VB, and Group VIB, and selectively contains one or more elements from Li, K, Mg, Ca, Sr, Ba, Zn, La, Sc, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Al, Sn, Ge, Bi, and Sb. B contains one or more nonmetallic elements from Group IIIA, Group IVA, Group VA, and Group VIA, and selectively contains one or more elements from Si, P, B, S, and Se. Q comprises one or more nonmetallic elements from Group VA and Group VIIA, and selectively comprises one or more elements from F, Cl, and N, the method according to any one of claims 7 to 11.

13. The volume distribution particle size Dv50 of the sodium-containing layered transition metal oxide is 2000-8000 nm, and / or The sodium-containing layered transition metal oxide comprises one or more of the O3 phase, P2 phase, and P3 phase, and is the method according to any one of claims 7 to 12.

14. A positive electrode plate comprising a positive electrode current collector and a positive electrode film layer installed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises a positive electrode active material according to any one of claims 1 to 6 or a positive electrode active material manufactured by the method according to any one of claims 7 to 13.

15. The positive electrode plate according to claim 14, wherein the content of the positive electrode active material in the positive electrode film layer is 50 wt% to 99 wt%, and selectively 85 wt% to 99 wt%, based on the total weight of the positive electrode film layer.

16. A battery cell comprising the positive electrode plate described in claim 14 or 15.

17. A battery comprising the battery cell described in claim 16.

18. A power consumption device including the battery described in claim 17.

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