Layered oxide cathode material and its manufacturing method, cathode plate, and sodium-ion battery

Abstract

The present invention relates to a layered oxide cathode material, a method for producing the same, a cathode plate, and a sodium-ion battery, and belongs to the technical field of sodium-ion batteries. The layered oxide cathode material comprises O3@P2 phase composite oxide particles, which include O3 phase nickel-manganese oxide layered particles and a P2 phase metal oxide coating layer coated on the surface of the O3 phase nickel-manganese oxide layered particles, and an inert coating layer coated on the surface thereof, wherein the inert coating layer is a carbon layer and / or an inorganic metal oxide layer. When the layered oxide cathode material according to the present invention is used in a sodium-ion battery, the manufactured sodium-ion battery has high initial Coulomb efficiency, excellent rate characteristics, long cycle life, and good air stability.

Description

[Technical Field]

[0001] The present invention relates to the technical field of sodium-ion batteries, and more specifically to layered oxide cathode materials, methods for producing the same, cathode plates, and sodium-ion batteries. [Background technology]

[0002] Lithium-ion batteries are already widely used in electric vehicles, home appliances, and energy storage, but they face problems such as low reserves and uneven distribution of lithium resources, as well as large price fluctuations, which significantly limit their large-scale application. Compared to lithium resources, sodium resources are widely distributed in the Earth's crust and readily available, giving sodium-ion batteries a cost advantage and raising expectations for large-scale applications in the energy storage sector.

[0003] Sodium-ion batteries operate on a principle similar to lithium-ion batteries, storing and releasing energy by utilizing the release and absorption of sodium ions between the positive and negative electrodes. Currently, the positive electrode materials for sodium-ion batteries mainly include layered transition metal oxides, polyanionic compounds, and Prussian blue analogs. Among these, layered transition metal oxide positive electrode materials have the highest sodium absorption capacity and are attracting increasing research and attention. Layered transition metal oxides can be classified mainly into P2 and O3 types depending on the coordination environment of sodium ions and the stacking order between layers. The letters P and O represent ternary prismatic and octahedral sodium ion coordination environments, respectively, and the numbers 2 and 3 represent the stacking order between layers as ABBA and ABCABC, respectively. Of these, P2 phase materials are sodium-deficient phases (usually with a sodium content of less than 0.67%). If sodium-ion batteries are manufactured using these materials, the resulting sodium-ion batteries have a low initial charge capacity and require an additional sodium replenishment process, making them unsuitable for practical use. O3 phase materials are sodium-rich (typically with a sodium content close to 1.0), and when used to manufacture sodium-ion batteries, the resulting batteries have high charge and discharge capacities. For this reason, O3 phase materials are promising as cathode materials for commercial sodium-ion batteries. However, the abundant sodium elements in O3 phase cathode materials readily react with moisture and carbon dioxide in the air, resulting in a high residual alkali content on the material's surface. This leads to the formation of low-conductivity substances such as sodium carbonate, sodium hydroxide, and sodium bicarbonate, which affects the initial Coulomb efficiency, reversible capacity, and other properties of the manufactured sodium-ion batteries.

[0004] Based on this, how to remove or effectively utilize residual alkali on the surface of O3-phase layered oxide sodium-ion battery cathode materials to improve the air stability of O3-phase layered oxide sodium-ion battery cathode materials is an urgent technical challenge that must be solved in this field. [Overview of the project] [Problems that the invention aims to solve]

[0005] The main objective of this invention is to provide a layered oxide cathode material, a method for producing the same, a cathode plate, and a sodium-ion battery, in order to solve the problem of poor electrochemical properties of sodium-ion battery cathode materials in the conventional technology, which are caused by residual alkali and poor air stability. [Means for solving the problem]

[0006] To achieve the above objective, a first aspect of the present invention provides a layered oxide cathode material comprising O3@P2 phase composite oxide particles including O3 phase nickel-manganese oxide layered particles and a P2 phase metal oxide coating layer coated on the surface of the O3 phase nickel-manganese oxide layered particles, and an inert coating layer coated on the surface of the O3@P2 phase composite oxide particles, wherein the inert coating layer is a carbon layer and / or an inorganic metal oxide layer.

[0007] The technical solution of the embodiment of the present invention provides a layered oxide cathode material having a two-layer coating structure that addresses the shortcomings of the cathode materials of existing sodium-ion batteries. In this material, the P2 phase metal oxide coating layer reduces the residual alkali content on the surface of the O3 phase nickel-manganese oxide layered particles and provides good transport channels for sodium ions, while the inert coating layer delays side reactions between the outer surface of the layered oxide cathode material and the air and electrolyte, thereby significantly reducing the amount of residual alkali on the surface of the oxide material and improving air stability.

[0008] Furthermore, the molecular formula of the O3-phase nickel-manganese oxide layered particles is Na x Ni a Mn b M1 c O2 (where 0.8 ≤ x ≤ 1.0, a + b + c = 1.0, and a, b, and c are all positive numbers, and M1 is one or more selected from Fe, Ti, Mg, Cu, Al, Ca, Zn, and Co), preferably M1 is one or more selected from Fe, Ti, Mg, Cu, Zn, and Ca.

[0009] In this embodiment, the inventors, after numerous experiments, selected and optimized the type of O3-phase nickel-manganese oxide layered particles. As a result, they found that when the components match the elemental composition and stoichiometric ratio of the above molecular formula, the air stability of the obtained O3-phase nickel-manganese oxide layered particles is further improved, and the compatibility and suitability of the O3-phase nickel-manganese oxide layered particles with the P2-phase metal oxide coating layer are also improved.

[0010] Furthermore, the molecular formula of the P2 phase metal oxide coating layer is Na y M2O2 (where 0.6 ≤ y ≤ 0.8, and M2 is one or more selected from Ni, Mn, Fe, Ti, Mg, Cu, Al, Ca, and Co), preferably M2 is one or more selected from Fe, Mn, Mg, Cu, and Ca.

[0011] In this example, the inventors, after numerous experiments, selected and optimized the type of P2 phase metal oxide coating layer. As a result, they found that when its components match the elemental composition and stoichiometric ratio in the above molecular formula, it is possible to better reduce the amount of residual alkali on the surface of the O3 phase nickel-manganese oxide layered particles and effectively improve the air stability of the P2 phase metal oxide coating layer.

[0012] Furthermore, the inorganic metal oxide layer is one or more selected from the Al2O3 layer, TiO2 layer, CuO layer, and MgO layer, and preferably the inorganic metal oxide layer is one or more selected from the Al2O3 layer, TiO2 layer, and MgO layer.

[0013] In this embodiment, some of the above inorganic metal oxide layers have a more stabilized structure compared to the inorganic metal oxide layers formed by other metals, and can further suppress the side reaction between the O3@P2 phase composite oxide particles and the electrolyte. Furthermore, the inventors preferably made the inorganic metal oxide layer be one or more selected from an Al2O3 layer, a TiO2 layer, and a MgO layer, and these inorganic metal oxide layers can better cooperate synergistically with the above preferred P2 phase metal oxide coating layer, and the cost is also lower. As a result, it was found that the product added value of the manufactured layered oxide cathode material can be effectively increased.

[0014] Furthermore, M1 in the O3 phase nickel manganese-based oxide layered particles is Ti, and M2 in the P2 phase metal oxide coating layer is one or more selected from Fe, Cu, and Mn, or M1 in the O3 phase nickel manganese-based oxide layered particles is Cu or Ti and Cu, and M2 in the P2 phase metal oxide coating layer is one or more selected from Mg, Cu, and Mn.

[0015] In this embodiment, through a lot of experiments and comparisons, the inventors found that when M2 in the P2 phase metal oxide coating layer and M1 in the O3 phase nickel manganese-based oxide layered particles are combined as above, the P2 phase metal oxide coating layer and the O3 phase nickel manganese-based oxide layered particles can be better bonded, and the residual alkali on the surface of the O3 phase nickel manganese-based oxide is more effectively removed, and the air stability of the obtained layered oxide cathode material is improved.

[0016] Furthermore, the molecular formula of the O3 phase nickel manganese-based oxide layered particles is NaNi 0.5 Mn 0.4 Ti 0.1 O2, and the molecular formula of the P2 phase metal oxide coating layer is Na 9 / 7 Cu 2 / 9 Fe 1 / 9 Mn 2 / 3 O2, and the inert coating layer is an Al2O3 layer, or the molecular formula of the O3 phase nickel manganese-based oxide layered particles is NaNi0.45 Mn 0.4 Ti 0.1 Cu 0.05 It is O2, and the molecular formula of the P2 phase metal oxide coating layer is Na 0.6 Mg 0.15 Cu 0.15 Mn 0.7 It is O2, and the inert coating layer is a carbon layer.

[0017] In this embodiment, when layered oxide cathode material is provided with O3-phase nickel-manganese oxide layered particles as the core, a P2-phase metal oxide coating layer as the first coating layer, and an inert coating layer as the second coating layer, as in the two methods described above, the resulting layered oxide cathode material not only has excellent electrochemical properties but also high air stability, thus better satisfying practical requirements.

[0018] Furthermore, in the layered oxide cathode material, the thickness of the P2 phase metal oxide coating layer is 2 nm to 100 nm, and the thickness of the inert coating layer is 2 to 100 nm. Preferably, when the weight of the layered oxide cathode material is 100%, the P2 phase metal oxide coating layer is 0.5 mass% to 5 mass%, and the inert coating layer is 0.5 mass% to 5 mass%, and preferably, the coverage rate of the P2 phase metal oxide coating layer on the surface of the O3 phase nickel manganese-based oxide layered particles is 80% to 100%, and the coverage rate of the inert coating layer on the surface of the O3@P2 phase composite oxide particles is 80% to 100%.

[0019] In this embodiment, if the thickness of the two coating layers is within the above range, a better balance can be achieved between suppressing side reactions, consuming residual alkali, and improving conductivity, thereby further improving the electrochemical properties of the cathode material. When the two coating layers are provided in the above weight ratio, the synergy and mass transfer between each coating layer and between the P2 phase metal oxide coating layer and core particles are improved, and the electrochemical properties of the resulting cathode material are further improved. In some representative embodiments, the coverage of the P2 phase metal oxide coating layer on the surface of the O3 phase nickel manganese oxide layered particles is 80% to 100%, and the coverage of the inert coating layer on the surface of the O3@P2 phase composite oxide particles is 80% to 100%. In the layered oxide cathode material structure according to the present invention, the coverage of each coating layer can reach 80% or more, that is, a good, complete, and uniform coating structure can be obtained, and as a result, the air stability of the resulting layered oxide cathode material is further improved.

[0020] A second aspect of the present invention provides a method for producing a layered oxide cathode material, comprising the steps of: preparing O3-phase nickel-manganese oxide layered particles and a first metal source; mixing the O3-phase nickel-manganese oxide layered particles and the first metal source and performing a first ball milling to obtain first pre-coated particles; subjecting the first pre-coated particles to a first calcination treatment to obtain O3@P2-phase composite oxide particles; mixing the O3@P2-phase composite oxide particles with a carbon source and / or a second metal source and performing a second ball milling to obtain second pre-coated particles; and subjecting the second pre-coated particles to an optional second calcination treatment to obtain a layered oxide cathode material.

[0021] In the technical solution of the embodiment of the present application, first, the bond strength between the first metal source and the O3-phase nickel-manganese oxide layered particles is improved by pre-coating them. Then, a P2-phase metal oxide coating layer is insitu generated on the surface of the O3-phase nickel-manganese oxide layered particles by an in-situ solid-phase reaction, thereby significantly consuming residual alkali on the surface and improving air stability. Subsequently, the O3@P2-phase composite oxide particles and the carbon source and / or second metal source are pre-coated by ball milling, and an inert coating layer is generated by another in-situ solid-phase reaction. This allows for better cooperation of the physical and chemical properties between each coating layer compared to simple mixed coating or liquid-phase reaction, simplifies the flow while protecting the structural integrity of the core particles and coating layers, and results in a layered oxide cathode material with better properties and higher product added value. Furthermore, the layered oxide cathode material according to the present invention has a simple manufacturing method, excellent compatibility with existing manufacturing processes, and is easily applicable to large-scale industrial applications.

[0022] Furthermore, the first ball milling operation has a rotational speed of 100 rpm to 500 rpm and a duration of 0.5 hours to 4 hours, and / or the second ball milling operation has a rotational speed of 100 rpm to 500 rpm and a duration of 0.5 hours to 4 hours.

[0023] In this example, by setting the experimental conditions for the two ball milling processes as described above, a more uniform coating can be achieved, and as a result, the uniformity of components, structural continuity, and coating completeness of the resulting P2 phase metal oxide coating layer and inert coating layer can be improved.

[0024] Furthermore, the weight ratio of O3-phase nickel-manganese oxide layered particles to the first metal source is 1:(0.005~0.05), and the weight ratio of O3@P2-phase composite oxide particles to the carbon source and / or second metal source is 1:(0.005~0.05). Preferably, the first metal source comprises a sodium source and a coated metal source, and the coated metal source is selected from oxides, hydroxides, carbonates, sulfates, oxalates, acetates, and citrates corresponding to Fe, Ti, Mg, Cu, Al, Ca, and Co. The first metal source is one or more of the following: the sodium source is one or more selected from sodium carbonate, sodium hydroxide, sodium nitrate, and sodium peroxide; preferably, the carbon source is one or more selected from coal tar, coal pitch, petroleum pitch, expanded graphite, carbon black, and graphene; and the second metal source is one or more selected from oxides, hydroxides, and carbonates corresponding to Ni, Mn, Fe, Ti, Mg, Cu, Al, Ca, and Co.

[0025] In this embodiment, the inventors, after numerous experiments, preferredly determined the above weight ratio relationship, as well as the weight ratio and coating thickness corresponding to the P2 phase metal oxide coating layer and the inert coating layer. They found that by manufacturing the material with the above weight ratio relationship, the electrochemical properties and air stability of the obtained layered oxide cathode material could be more effectively improved. The inventors, after numerous comparative tests, determined several coating metal sources and sodium sources and found that selecting the above types allows the solid-phase reaction to proceed more smoothly, forming the P2 phase metal oxide coating layer and contributing to obtaining a cathode material with the desired structure. Furthermore, the inventors, after numerous comparative tests, determined several carbon sources and second metal sources and found that selecting the above types allows the inert coating layer to be formed more continuously, uniformly, and densely, resulting in a layered oxide cathode material with superior properties.

[0026] Furthermore, the first calcination treatment is performed at a temperature of 600°C to 1000°C for a calcination time of 2 hours to 20 hours, and the second calcination treatment is performed at a temperature of 400°C to 1000°C for a calcination time of 0.5 hours to 20 hours. Preferably, the calcination atmosphere for the first calcination treatment is an air and / or oxygen atmosphere.

[0027] In this embodiment, the inventors, after numerous experiments, determined the preferred temperature and time conditions for the two calcination processes described above. They found that following these conditions resulted in a more stable two-layer coating structure, specifically, tighter bonding between the P2-phase metal oxide coating layer and the surface of the O3-phase nickel-manganese oxide layered particles, and tighter bonding between the inert coating layer and the surface of the O3@P2-phase composite oxide particles. Furthermore, they found that the air stability of the manufactured layered oxide cathode material was improved.

[0028] More preferably, the calcination atmosphere for the first calcination treatment is an air and / or oxygen atmosphere. The inventors have found that by performing the first calcination in the presence of air, the P2 phase oxide coating layer can be formed more efficiently and the ionic conductivity can be improved.

[0029] Furthermore, when mixing O3@P2 phase composite oxide particles with a second metal source, a second calcination treatment is performed, with a temperature of 700°C to 1000°C, a duration of 10 to 20 hours, and an atmosphere of air and / or oxygen. In this case, the inert coating layer is an inorganic metal oxide layer, but after many experiments, the inventors have preferred the above conditions to form an inert coating layer with a more stable and dense structure, thereby improving the air stability of the final layered oxide cathode material.

[0030] In this embodiment, O3@P2 phase composite oxide particles are mixed with a carbon source, and when the carbon source is one or more selected from coal tar, coal pitch, and petroleum pitch, a second calcination treatment is performed. The second calcination treatment is performed at a temperature of 400°C to 800°C for a duration of 0.5h to 2h, and in a nitrogen atmosphere and / or argon atmosphere. In this case, the inert coating layer is a carbon layer, and the carbon source contains various small organic molecules. Therefore, after many experiments, the inventors preferred to determine the above conditions in order to achieve carbonization while removing small organic molecules from coal tar, coal pitch, and petroleum pitch, thereby obtaining a more complete and stable carbon layer, and thereby improving the air stability of the final layered oxide cathode material.

[0031] When O3@P2 phase composite oxide particles are mixed with a carbon source, and the carbon source is one or more selected from expanded graphite, carbon black, and graphene, a layered oxide cathode material is obtained after a second ball milling without a second calcination treatment. In this case, the inert coating layer is a carbon layer, and the carbon source contains only elemental carbon, so to simplify the process and shorten the time, a layered oxide cathode material is obtained after a second ball milling.

[0032] A third aspect of the present invention provides a positive electrode plate containing the above-described layered oxide positive electrode material.

[0033] In this embodiment, the positive electrode plate contains the above-mentioned layered oxide positive electrode material, and therefore has high electrochemical properties and good air stability.

[0034] A fourth aspect of the present invention provides a sodium-ion battery including the above-described positive electrode plate. [Effects of the Invention]

[0035] The positive electrode material obtained by the present invention possesses both excellent electrochemical properties and structural stability. Therefore, when this positive electrode material is used as a component of a positive electrode plate in a sodium-ion battery, the resulting sodium-ion battery exhibits improved electrochemical properties, including improved initial Coulomb efficiency, excellent rate characteristics, long cycle life, and good air stability, making it suitable for a wide range of applications.

[0036] The above description is merely an outline of the technical solution of this application. In order to provide a clearer understanding of the technical solution of this application, to enable implementation in accordance with the contents of the specification, and to make the above and other objectives, features, and advantages of this application clearer and easier to understand, specific embodiments of this application are given below. [Brief explanation of the drawing]

[0037] To more clearly explain the technical solution of this application, the drawings used in this application are briefly described below. As is clear, the drawings described below represent only some embodiments of this application, and those skilled in the art can derive other drawings from these without any creative work.

[0038] [Figure 1] This is a scanning electron microscope image of the layered oxide cathode material obtained in Example 1. [Figure 2] This is a scanning electron microscope image of the layered oxide cathode material obtained in Comparative Example 1. [Figure 3] This is the XRD pattern of the layered oxide cathode material obtained in Example 1. [Figure 4] This is the XRD pattern of the layered oxide cathode material obtained in Comparative Example 1. [Modes for carrying out the invention]

[0039] The following descriptions will detail embodiments of the technical solution of the present application with reference to the drawings. The following embodiments are provided solely as examples to more clearly illustrate the technical solution of the present application and will not limit the scope of protection of the present application.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art. Terms used herein are used solely to describe specific embodiments and are not intended to limit this application. The terms “including” and “having,” and their variations, in the description of the specification, claims, and drawings above, are intended to cover non-exclusive inclusion.

[0041] In the description of the embodiments of this application, technical terms such as “first,” “second,” etc., are used solely to distinguish different subjects and are not to be understood as indicating or implying relative importance, or implicitly indicating the number, specific order, or primary / secondary relationship of the technical features shown. In the description of the embodiments of this application, “plural” means two or more unless otherwise clearly and specifically limited.

[0042] The “Examples” described herein mean that certain features, structures, or properties described with reference to the Examples may be included in at least one Example of the Application. The appearance of the same term in different parts of the Specification does not necessarily refer to the same Example, nor does it refer to mutually exclusive, independent, or alternative Examples. As those skilled in the art will understand both explicitly and implicitly, the Examples described herein may be combined with other Examples.

[0043] In the description of the embodiments of this application, the term "and / or" merely describes the relationship between related objects, indicating that three relationships are possible. For example, in the case of A and / or B, it can mean that A exists alone, that A and B exist simultaneously, or that B exists alone. In addition, the symbol " / " in this specification generally indicates that the preceding and succeeding related objects are in an "or" relationship.

[0044] In the description of the embodiments of this application, the term "multiple" means two or more (including two), similarly, "multiple sets" means two or more sets (including two sets), and "multiple sheets" means two or more sheets (including two sheets).

[0045] In the description of the embodiments of this application, the orientations or positional relationships indicated by technical terms such as "center," "vertical direction," "horizontal direction," "length," "width," "thickness," "top," "bottom," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inside," "outside," "clockwise," "counterclockwise," "axial direction," "radial direction," and "circumferential direction" are based on the orientations or positional relationships indicated on the surface and are merely intended to facilitate and simplify the description of the embodiments of this application. They do not indicate or imply that the devices or elements shown need to have a specific orientation, or be configured and operated in a specific orientation, and therefore should not be interpreted as limiting the embodiments of this application.

[0046] In the description of the embodiments of this application, unless otherwise specifically defined and limited, technical terms such as “attach,” “connect,” “join,” and “fix” should be understood in a broad sense, and may include, for example, fixed connections, removable connections, or integral connections; mechanical connections, electrical connections; direct connections, indirect connections via an intermediate medium, internal communication between two components, or interaction relationships between two components. A person skilled in the art will understand the specific meaning of the above terms in the embodiments of this application depending on the specific circumstances.

[0047] As described in the background information, conventional sodium-ion battery cathode materials have the problem of poor electrochemical properties due to residual alkali and poor air stability. To solve the above technical problems, a first aspect of the present invention provides a layered oxide cathode material comprising O3@P2 phase composite oxide particles including O3 phase nickel-manganese oxide layered particles and a P2 phase metal oxide coating layer coated on the surface of the O3 phase nickel-manganese oxide layered particles, and an inert coating layer coated on the surface of the O3@P2 phase composite oxide particles, wherein the inert coating layer is a carbon layer and / or an inorganic metal oxide layer.

[0048] The layered oxide cathode material according to the present invention comprises an O3-phase nickel-manganese oxide layered particle core, a first P2-phase metal oxide coating layer coated thereon, and a second inert coating layer, wherein the first P2-phase metal oxide coating layer reduces the residual alkali content on the surface of the O3-phase nickel-manganese oxide layered particles and provides good transport channels for sodium ions, and the inert coating layer delays side reactions between the outer surface of the layered oxide cathode material and air and electrolyte, thereby the entire layered oxide cathode material exhibits high electrochemical properties and good air stability.

[0049] Specifically, the P2 phase metal oxide coating layer and the inert coating layer work together to improve the overall electrochemical properties of the O3 phase nickel-manganese oxide layered particles. Here, the inert coating layer is stable, uniform, and dense, and when it coats the outermost surface and comes into direct contact with the electrolyte, it can more effectively reduce side reactions between the manufactured layered oxide cathode material and the electrolyte, further reducing the erosion of the cathode active components by HF produced by side reactions, thereby extending its service life. In addition, an inert coating layer with a degree of flexibility can effectively suppress the occurrence of cracks inside the cathode material particles. However, when the inert coating layer comes into direct contact with the O3 phase nickel-manganese oxide layered particles, the diffusion channels of metal ions in the core are blocked, affecting the electrochemical properties of the cathode material. Taking this into consideration, the present invention employs a configuration in which a P2 phase metal oxide coating layer and an inert coating layer are coated in this order. The P2 phase metal oxide coating layer has poor side reaction suppression ability, but it has high ionic conductivity and can effectively reduce the charge transport impedance on the surface of the O3 phase nickel-manganese oxide layered particles.

[0050] The inventors, taking the above circumstances into comprehensive consideration, conducted numerous experiments and found that a combination of a P2-phase metal oxide coating layer and an inert coating layer was used. Specifically, a P2-phase metal oxide coating layer, which has high ionic conductivity and significantly consumes residual alkali, was applied to the surface of O3-phase nickel-manganese oxide layered particles. Subsequently, an inert coating layer was applied to the surface of the P2-phase metal oxide coating layer, and the inert coating layer was brought into direct contact with the electrolyte. By synergistically combining the advantages of the two types of coating layers, the present invention improves the electrochemical properties of the resulting layered oxide cathode material. Furthermore, it is possible to improve the initial Coulomb efficiency and rate characteristics of sodium-ion batteries manufactured using this cathode material, and extend the cycle life.

[0051] Furthermore, the molecular formula of the O3-phase nickel-manganese oxide layered particles is Na x Ni a Mn b M1 cThe element is O2 (where 0.8 ≤ x ≤ 1.0, a + b + c = 1.0, and a, b, and c are all positive numbers, and M1 is one or more elements selected from Fe, Ti, Mg, Cu, Al, Ca, Zn, and Co). The inventors, after numerous experiments, selected and optimized the type of O3-phase nickel-manganese oxide layered particles and found that the electrochemical properties are superior when the components match the elemental composition and stoichiometric ratio of the above molecular formula. Furthermore, it is even more preferable that M1 is one or more elements selected from Fe, Ti, Mg, Cu, Zn, and Ca. By employing some of the above metal elements, the electrochemical properties of the O3-phase nickel-manganese oxide layered particles are further improved, and the compatibility and fit with the coating layer on top are also improved.

[0052] In some representative embodiments, the molecular formula of the P2 phase metal oxide coating layer is Na y The P2 phase metal oxide coating layer is M2O2 (where 0.6 ≤ y ≤ 0.8, and M2 is one or more elements selected from Ni, Mn, Fe, Ti, Mg, Cu, Al, Ca, Zn, and Co). Through numerous experiments, the inventors selected and optimized the type of P2 phase metal oxide coating layer and found that when its components are in the stoichiometric ratio of the elemental composition in the above molecular formula, the amount of residual alkali on the surface of the O3 phase nickel-manganese oxide layered particles can be better reduced and its ionic conductivity can be effectively increased. Furthermore, through numerous experiments, the inventors preferably set M2 to one or more elements selected from Fe, Mn, Mg, Cu, Zn, and Ca. By using some of the above metal elements, the resulting P2 phase metal oxide coating layer can more effectively reduce the charge transport impedance on the surface of the O3 phase nickel-manganese oxide layered particles, and as a result, the electrochemical properties of the resulting layered oxide cathode material can be more significantly improved.

[0053] Regarding the selection of inert coating layers other than the carbon layer, the inventors, after numerous experiments, have found that in some preferred embodiments, the inorganic metal oxide layer is preferably one or more of the Al2O3 layer, TiO2 layer, CuO layer, and MgO layer. Compared to inorganic metal oxide layers formed by other metals, the structure of some of the above inorganic metal oxide layers is more stable and can better suppress side reactions between the O3@P2 phase composite oxide particles and the electrolyte. Furthermore, the inventors have found that it is even more preferable for the inorganic metal oxide layer to be one or more selected from the Al2O3 layer, TiO2 layer, and MgO layer, as these inorganic metal oxide layers can work synergistically better with the above preferred P2 phase metal oxide coating layer, and the cost is lower, thereby effectively increasing the added value of the manufactured layered oxide cathode material.

[0054] In some representative embodiments, M1 in the O3-phase nickel-manganese oxide layered particles is Ti, and M2 in the P2-phase metal oxide coating layer is one or more selected from Fe, Cu, and Mn; or M1 in the O3-phase nickel-manganese oxide layered particles is Cu or Ti and Cu, and M2 in the P2-phase metal oxide coating layer is one or more selected from Mg, Cu, and Mn. Since the P2-phase metal oxide coating layer plays a role in bonding the O3-phase nickel-manganese oxide layered particles and the inert coating layer, whether or not good bonding can be achieved with the O3-phase nickel-manganese oxide layered particles is a very important factor. Through numerous experiments and comparisons, the inventors have found that when M2 in the P2 phase metal oxide coating layer and M1 in the O3 phase nickel-manganese oxide particles are combined as described above, the P2 phase metal oxide coating layer and the O3 phase nickel-manganese oxide layered particles bond better, residual alkali on the surface of the O3 phase nickel-manganese oxide particles is more effectively removed, the electrochemical properties of the resulting layered oxide cathode material are improved, and the initial Coulomb efficiency and rate characteristics of sodium-ion batteries manufactured using this cathode material are improved, resulting in a longer cycle life.

[0055] Through numerous experiments, the inventors have further preferred the core oxide and the two coating layers of the layered oxide cathode material, and in two of the most representative embodiments, the molecular formula of the O3-phase nickel-manganese oxide layered particles is NaNi 0.5 Mn 0.4 Ti 0.1 It is O2, and the molecular formula of the P2 phase metal oxide coating layer is Na 9 / 7 Cu 2 / 9 Fe 1 / 9 Mn 2 / 3 It is O2, the inert coating layer is an Al2O3 layer, or the molecular formula of the O3 phase nickel-manganese oxide layered particles is NaNi 0.45 Mn 0.4 Ti 0.1 Cu 0.05 It is O2, and the molecular formula of the P2 phase metal oxide coating layer is Na 0.6 Mg 0.15 Cu 0.15 Mn 0.7 The core is O2, and the inert coating layer is a carbon layer. In a layered oxide cathode material, if O3-phase nickel-manganese oxide layered particles are provided as the core, a P2-phase metal oxide coating layer as the first coating layer, and an inert coating layer as the second coating layer, as in the two methods described above, the resulting layered oxide cathode material not only has excellent electrochemical properties but also high air stability, thus better satisfying practical requirements.

[0056] In addition to the preferred composition of the elements described above, during the experimental process, the inventors found that the thickness, mass ratio, and degree of coating of the film layer had a similarly significant effect on the properties of the resulting layered oxide cathode material. In a typical embodiment, the thickness of the P2 phase metal oxide coating layer is 2 nm to 100 nm, and the thickness of the inert coating layer is 2 to 100 nm. If the thicknesses of the P2 phase metal oxide coating layer and the inert coating layer are within the above range, a better balance can be achieved between suppressing side reactions, consuming residual alkali, and improving conductivity, and the electrochemical properties of the resulting layered oxide cathode material can be further improved. Regarding the weight ratio of the P2 phase metal oxide coating layer and the inert coating layer, in a preferred embodiment, if the weight of the layered oxide cathode material is 100%, the P2 phase metal oxide coating layer is 0.5 mass% to 5 mass%, and the inert coating layer is 0.5 mass% to 5 mass%. By providing the two coating layers in the weight ratios described above, the synergy and mass transfer between the P2-phase metal oxide coating layer and the inert coating layer, and between the P2-phase metal oxide coating layer and the core particles are improved, further enhancing the electrochemical properties of the resulting layered oxide cathode material. Furthermore, in some representative embodiments, the coverage of the P2-phase metal oxide coating layer on the surface of the O3-phase nickel-manganese oxide layered particles is 80% to 100%, and the coverage of the inert coating layer on the surface of the O3@P2-phase composite oxide particles is 80% to 100%. In the structure of the layered oxide cathode material according to the present invention, the coverage of the P2-phase metal oxide coating layer and the inert coating layer can reach 80% or more, that is, a good, complete, and uniform coating structure is obtained, and the air stability of the layered oxide cathode material is further improved.

[0057] A second aspect of the present invention provides a method for producing the above-mentioned layered oxide cathode material, comprising the steps of: providing O3-phase nickel-manganese oxide layered particles and a first metal source; mixing the O3-phase nickel-manganese oxide layered particles and the first metal source and performing a first ball milling to obtain first pre-coated particles; subjecting the first pre-coated particles to a first calcination treatment to obtain O3@P2-phase composite oxide particles; mixing the O3@P2-phase composite oxide particles with a carbon source and / or a second metal source and performing a second ball milling to obtain second pre-coated particles; and subjecting the second pre-coated particles to an optional second calcination treatment to obtain a layered oxide cathode material.

[0058] The above-described manufacturing method according to the present invention is simple, the relevant equipment is readily available, the process conditions are easy to achieve, and it is compatible with several existing manufacturing methods for cathode materials. Specifically, first, the first metal source and O3-phase nickel-manganese oxide layered particles are pre-coated to improve the bonding strength between them. Then, a P2-phase metal oxide coating layer is insitu generated on the surface of the O3-phase nickel-manganese oxide layered particles by an in-situ solid-phase reaction, thereby significantly consuming residual alkali on the surface and improving air stability. Subsequently, the O3@P2-phase composite oxide particles and the carbon source and / or second metal source are ball-milled and pre-coated, and an inert coating layer is generated by another in-situ solid-phase reaction. This allows for better cooperation of the physical and chemical properties between each coating layer compared to simple mixed coating or liquid-phase reactions, simplifies the process, protects the structural integrity of the core particles and coating layers, and yields a layered oxide cathode material with better performance and higher product added value.

[0059] To enhance the effect of the two pre-coatings, preferably, the first ball milling is performed at a rotational speed of 100 rpm to 500 rpm for a duration of 0.5 h to 4 h, and / or the second ball milling is performed at a rotational speed of 100 rpm to 500 rpm for a duration of 0.5 h to 4 h. By setting the experimental conditions for the two ball millings as described above, a more uniform coating can be achieved, and as a result, the uniformity of components, structural continuity, and coating completeness of the resulting P2 phase metal oxide coating layer and inert coating layer can be improved.

[0060] To better control the weight ratio and coating thickness of the P2 phase metal oxide coating layer and the inert coating layer, the inventors have found that in some representative embodiments, the weight ratio of O3 phase nickel manganese oxide layered particles to the first metal source is preferably 1:(0.005~0.05), and the weight ratio of O3@P2 phase composite oxide particles to the carbon source and / or second metal source is preferably 1:(0.005~0.05). Through numerous experiments, the inventors have found that by determining the above weight ratio relationship, as well as the weight ratio and coating thickness corresponding to the P2 phase metal oxide coating layer and the inert coating layer, and by manufacturing the material with the above weight ratio relationship, the electrochemical performance and air stability of the obtained layered oxide cathode material can be more effectively improved.

[0061] In some preferred embodiments, the first metal source comprises a sodium source and a coating metal source, where the coating metal source is one or more selected from oxides, hydroxides, carbonates, sulfates, oxalates, acetates, and citrates corresponding to Fe, Ti, Mg, Cu, Al, Ca, Zn, and Co, and the sodium source is one or more selected from sodium carbonate, sodium hydroxide, sodium nitrate, and sodium peroxide. After numerous comparative tests, the inventors determined several of the above coating metal sources and sodium sources and found that selecting the above types leads to a smoother solid-phase reaction, the formation of a P2 phase metal oxide coating layer, and the acquisition of a layered oxide cathode material with a desired structure.

[0062] In some preferred embodiments, the carbon source is one or more selected from coal tar, coal pitch, petroleum pitch, expanded graphite, carbon black, and graphene, and the second metal source is one or more selected from oxides, hydroxides, and carbonates corresponding to Ni, Mn, Fe, Ti, Mg, Cu, Al, Ca, and Co. Similarly, after numerous comparative tests, the inventors determined several of the above carbon sources and second metal sources and found that selecting the above types results in a more continuous, uniform, and dense, smooth formation of the inert coating layer, yielding a layered oxide cathode material with superior properties.

[0063] The present invention forms a P2-phase metal oxide coating layer and an inert coating layer by calcination and solid-phase reaction. In a typical embodiment, the first calcination treatment is performed at a temperature of 600°C to 1000°C for a calcination time of 2 to 20 hours, and the second calcination treatment is performed at a temperature of 400°C to 1000°C for a calcination time of 0.5 to 20 hours. The inventors, after numerous experiments, determined the preferred temperature and time conditions for the two calcinations described above. They found that following these conditions results in a more stable two-layer coating structure, specifically, a tighter bond between the P2-phase metal oxide coating layer and the surface of the O3-phase nickel-manganese oxide layered particles, and a tighter bond between the inert coating layer and the surface of the O3@P2-phase composite oxide particles. Furthermore, they found that the air stability of the manufactured layered oxide cathode material is improved. More preferably, the calcination atmosphere for the first calcination treatment is an air and / or oxygen atmosphere. The inventors have found that by performing the first calcination in the presence of air, the P2 phase oxide coating layer can be formed more efficiently, thereby improving ionic conductivity.

[0064] In some representative embodiments, When mixing O3@P2 phase composite oxide particles with a second metal source, a second calcination treatment is performed, with a temperature of 700°C to 1000°C, a duration of 10 to 20 hours, and an atmosphere of air and / or oxygen. In this case, the inert coating layer is an inorganic metal oxide layer, but after many experiments, the inventors have preferred the above conditions to form an inert coating layer with a more stable and dense structure, thereby improving the air stability of the final layered oxide cathode material.

[0065] When O3@P2 phase composite oxide particles are mixed with a carbon source, and the carbon source is one or more selected from coal tar, coal pitch, and petroleum pitch, a second calcination treatment is performed, the second calcination treatment being at a temperature of 400°C to 800°C for 0.5 hours to 2 hours, and the atmosphere being a nitrogen atmosphere and / or an argon atmosphere. In this case, the inert coating layer is a carbon layer, and the carbon source contains various small organic molecules. Therefore, after many experiments, the inventors have preferred to determine the above conditions in order to achieve carbonization while removing small organic molecules from coal tar, coal pitch, and petroleum pitch, thereby obtaining a more complete and stable inert coating layer, and thereby improving the air stability of the finally formed layered oxide cathode material.

[0066] When O3@P2 phase composite oxide particles are mixed with a carbon source, and the carbon source is one or more selected from expanded graphite, carbon black, and graphene, a layered oxide cathode material is obtained after a second ball milling without a second calcination treatment. In this case, the inert coating layer is a carbon layer, and the carbon source contains only elemental carbon, so to simplify the process and shorten the time, a layered oxide cathode material is obtained in which the carbon layer is completely and stably coated in the structure after the second ball milling.

[0067] A third aspect of the present invention provides a positive electrode plate containing the above-described layered oxide positive electrode material.

[0068] A fourth aspect of the present invention provides a sodium-ion battery including the above-described positive electrode plate.

[0069] The positive electrode material obtained by the present invention possesses both excellent electrochemical properties and structural stability. Therefore, when this positive electrode material is used as a component of a positive electrode plate in a sodium-ion battery, the resulting sodium-ion battery exhibits improved electrochemical properties, including improved initial Coulomb efficiency, excellent rate characteristics, long cycle life, and good air stability, making it suitable for a wide range of applications.

[0070] The present application will be described in more detail below with reference to specific examples, but these examples are not intended to be understood as limiting the scope of protection claimed in this application.

[0071] Unless otherwise defined, all technical terms used herein have the same meaning as those generally understood by those skilled in the art. Technical terms used herein are solely for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the invention.

[0072] The following are some specific examples, but these examples are illustrative and are for interpretation purposes only and should not be understood as limiting the present application. Where specific techniques or conditions are not specified in the examples, they should be carried out in accordance with the techniques or conditions described in the relevant art literature or in accordance with the product description. Unless otherwise specified, the reagents or equipment used are all common products available commercially.

[0073] 1. Manufacturing method

[0074] Example 1 Method for manufacturing layered oxide cathode materials:

[0075] First, the O3 phase cathode material NaNi 0.45 Mn 0.4 Ti 0.1 Cu 0.05O2 was prepared by weighing sodium carbonate, nickel oxide, manganese dioxide, titanium dioxide, and copper oxide according to their molecular formula stoichiometric ratios, and mixing them uniformly in a ball mill with a fixed amount of anhydrous ethanol for 3 hours at a ball milling speed of 450 r / min. The mixture was dried in a vacuum drying oven for 12 hours to obtain a dry powder. The powder was then calcined at a high temperature of 900°C in an air atmosphere for 15 hours.

[0076] Next, sodium carbonate, magnesium oxide, copper oxide, and manganese dioxide were weighed according to the stoichiometric ratio of the P2 phase molecular formula, and thoroughly ground to obtain the first metal source. 1 g of the first metal source and the O3 phase cathode material NaNi were then mixed. 0.45 Mn 0.4 Ti 0.1 Cu 0.05 20g of O2 was placed in a ball milling tank, and ball milling was performed for 3 hours at a rotation speed of 450 rpm to obtain first pre-coated particles. The ball-milled first pre-coated particle sample was placed in a muffle furnace and baked at 900°C for 10 hours, then cooled and pulverized to obtain O3@P2 phase composite oxide particles having a P2 phase metal oxide coating layer. The molecular formula of the P2 phase is Na 0.6 Mg 0.15 Cu 0.15 Mn 0.7 It is O2.

[0077] Finally, 10 g of O3@P2 phase composite oxide particles having a first coating layer and 0.2 g of expanded graphite were placed in a ball milling tank, and ball milling was performed for 3 hours at a rotation speed of 450 rpm to obtain second pre-coated particles. The ball-milled second pre-coated particle sample was thoroughly dried and pulverized to obtain a layered oxide cathode material having a P2 phase metal oxide coating layer and an inert coating layer, which was then expressed as G+P2+O3. A scanning electron microscope image of the obtained G+P2+O3 layered oxide cathode material is shown in Figure 1, and the XRD test pattern is shown in Figure 3.

[0078] In the G+P2+O3 layered oxide cathode material, the thickness of the P2 phase metal oxide coating layer is 12 nm, and the thickness of the inert coating layer is 20 nm.

[0079] Example 2 Method for manufacturing layered oxide cathode materials:

[0080] First, the O3 phase cathode material NaNi 0.5 Mn 0.4 Ti 0.1 O2 was prepared by weighing sodium carbonate, nickel oxide, manganese dioxide, and titanium dioxide according to their molecular formula stoichiometric ratios, and mixing them uniformly with a fixed amount of anhydrous ethanol in a ball mill for 3 hours at a ball milling speed of 450 r / min. The mixture was dried in a vacuum drying oven for 12 hours to obtain a dry powder. The powder was then calcined at a high temperature of 900°C in an air atmosphere for 15 hours.

[0081] Next, sodium carbonate, magnesium oxide, copper oxide, and manganese dioxide were weighed according to the stoichiometric ratio of the P2 phase molecular formula, and thoroughly ground to obtain the first metal source. 1 g of the first metal source and the O3 phase cathode material NaNi were then mixed. 0.5 Mn 0.4 Ti 0.1 20g of O2 was placed in a ball milling tank, and ball milling was performed for 3 hours at a rotation speed of 450 rpm to obtain first pre-coated particles. The ball-milled first pre-coated particle sample was placed in a muffle furnace and baked at 900°C for 10 hours, then cooled and pulverized to obtain O3@P2 phase composite oxide particles having a P2 phase metal oxide coating layer. The molecular formula of the P2 phase is Na 9 / 7 Cu 2 / 9 Fe 1 / 9 Mn 2 / 3 It is O2.

[0082] Finally, 10 g of O3@P2 phase composite oxide particles having a first coating layer and 0.05 g of Al2O3 were placed in a ball milling tank, and the ball milling time was set to 3 hours and the rotation speed to 450 rpm to obtain second pre-coated particles. The ball-milled second pre-coated particle sample was placed in a muffle furnace and baked at 600°C for 10 hours to dry it thoroughly and then pulverized to obtain a layered oxide cathode material having a P2 phase metal oxide coating layer and an inert coating layer, which was then designated as the Al2O3@P2+O3 layered oxide cathode material.

[0083] In the Al2O3@P2+O3 layered oxide cathode material, the thickness of the P2 phase metal oxide coating layer is 14 nm, and the thickness of the inert coating layer is 18 nm.

[0084] Example 3 Method for manufacturing layered oxide cathode materials:

[0085] First, the O3 phase cathode material NaNi 0.45 Mn 0.4 Ti 0.1 Fe 0.05 O2 was prepared by weighing sodium carbonate, nickel oxide, manganese dioxide, titanium dioxide, and ferric oxide according to their molecular formula stoichiometric ratios, and mixing them uniformly in a ball mill with a fixed amount of anhydrous ethanol for 3 hours at a ball milling speed of 450 r / min. The mixture was dried in a vacuum drying oven for 12 hours to obtain a dry powder. The powder was then calcined at a high temperature of 900°C in an air atmosphere for 15 hours.

[0086] Next, sodium carbonate, magnesium oxide, copper oxide, and manganese dioxide were weighed according to the stoichiometric ratio of the P2 phase molecular formula, and thoroughly ground to obtain the first metal source. 1 g of the first metal source and the O3 phase cathode material NaNi were then mixed. 0.45 Mn 0.4 Ti 0.1 Fe 0.05 20g of O2 was placed in a ball milling tank, and ball milling was performed for 3 hours at a rotation speed of 450 rpm to obtain first pre-coated particles. The ball-milled first pre-coated particle sample was placed in a muffle furnace and baked at 900°C for 10 hours, then cooled and pulverized to obtain O3@P2 phase composite oxide particles having a P2 phase metal oxide coating layer. The molecular formula of the P2 phase is Na 0.6 Mg 0.15 Cu 0.15 Mn 0.7 It is O2.

[0087] Finally, 10 g of O3@P2 phase composite oxide particles having a first coating layer and 0.05 g of Al2O3 were placed in a ball milling tank, and the ball milling time was set to 3 hours and the rotation speed to 450 rpm to obtain second pre-coated particles. The ball-milled second pre-coated particle sample was placed in a muffle furnace and baked at 600°C for 10 hours to dry it thoroughly and then pulverized to obtain a layered oxide cathode material having a P2 phase metal oxide coating layer and an inert coating layer, which was then designated as the Al2O3@P2+O3 layered oxide cathode material.

[0088] In the Al2O3@P2+O3 layered oxide cathode material, the thickness of the P2 phase metal oxide coating layer is 15 nm, and the thickness of the inert coating layer is 22 nm.

[0089] Example 4 Method for manufacturing layered oxide cathode materials:

[0090] First, the O3 phase cathode material NaNi 0.45 Mn 0.4 Ti 0.1 Zn 0.05 O2 was prepared by weighing sodium carbonate, nickel oxide, manganese dioxide, titanium dioxide, and zinc oxide according to their molecular formula stoichiometric ratios, and mixing them uniformly in a ball mill with a fixed amount of anhydrous ethanol for 3 hours at a ball milling speed of 450 r / min. The mixture was dried in a vacuum drying oven for 12 hours to obtain a dry powder. The powder was then calcined at a high temperature of 900°C in an air atmosphere for 15 hours.

[0091] Next, sodium carbonate, magnesium oxide, copper oxide, and manganese dioxide were weighed according to the stoichiometric ratio of the P2 phase molecular formula, and thoroughly ground to obtain the first metal source. 1 g of the first metal source and the O3 phase cathode material NaNi were then mixed. 0.45 Mn 0.4 Ti 0.1 Zn 0.0520g of O2 was placed in a ball milling tank, and ball milling was performed for 3 hours at a rotation speed of 450 rpm to obtain first pre-coated particles. The ball-milled first pre-coated particle sample was placed in a muffle furnace and baked at 900°C for 10 hours, then cooled and pulverized to obtain O3@P2 phase composite oxide particles having a P2 phase metal oxide coating layer. The molecular formula of the P2 phase is Na 0.6 Mg 0.15 Cu 0.15 Mn 0.7 It is O2.

[0092] Finally, 10 g of O3@P2 phase composite oxide particles having a first coating layer and 0.05 g of TiO2 were placed in a ball milling tank, and the ball milling time was set to 3 hours and the rotation speed to 450 rpm to obtain second pre-coated particles. The ball-milled second pre-coated particle sample was placed in a muffle furnace and baked at 600°C for 10 hours to dry it thoroughly and then pulverized to obtain a layered oxide cathode material having a P2 phase metal oxide coating layer and an inert coating layer, which was then designated as a TiO2+P2+O3 layered oxide cathode material.

[0093] In the TiO2+P2+O3 layered oxide cathode material, the thickness of the P2 phase metal oxide coating layer is 16 nm, and the thickness of the inert coating layer is 19 nm.

[0094] Example 5 Method for manufacturing layered oxide cathode materials:

[0095] This embodiment differs from Example 1 only in the following respects: The amounts of the first metal source and expanded graphite (i.e., carbon source) used are different. Specifically, the amounts of the first metal source and expanded graphite were changed so that the weight ratio of O3-phase nickel-manganese oxide layered particles to the first metal source was 1:0.002, and the weight ratio of O3@P2-phase composite oxide particles to the carbon source was 1:0.002.

[0096] In the obtained G+P2+O3 layered oxide cathode material, the thickness of the P2 phase metal oxide coating layer is 1.5 nm, and the thickness of the inert coating layer is 1.8 nm.

[0097] Example 6 Method for manufacturing layered oxide cathode materials:

[0098] This embodiment differs from Example 1 only in the following respects: The amounts of the first metal source and expanded graphite (i.e., carbon source) used are different. Specifically, the amounts of the first metal source and expanded graphite were changed so that the weight ratio of O3-phase nickel-manganese oxide layered particles to the first metal source was 1:0.08, and the weight ratio of O3@P2-phase composite oxide particles to the carbon source was 1:0.08.

[0099] In the obtained G+P2+O3 layered oxide material, the thickness of the P2 phase metal oxide coating layer is 125 nm, and the thickness of the inert coating layer is 140 nm.

[0100] Example 7 Method for manufacturing layered oxide cathode materials:

[0101] This example differs from Example 1 only in the following respect: the conditions for the two ball milling processes are different, specifically,

[0102] The ball milling to obtain the first pre-coated particles was performed for 5 hours at a rotational speed of 50 rpm, and the ball milling to obtain the second pre-coated particles was also performed for 5 hours at a rotational speed of 50 rpm.

[0103] Example 8 Method for manufacturing layered oxide cathode materials:

[0104] This example differs from Example 1 only in the following respect: the conditions for the two ball milling processes are different, specifically,

[0105] The ball milling to obtain the first pre-coated particles was performed for a duration of 0.4 hours at a rotational speed of 600 rpm, and the ball milling to obtain the second pre-coated particles was also performed for a duration of 0.4 hours at a rotational speed of 600 rpm.

[0106] Example 9 Method for manufacturing layered oxide cathode materials:

[0107] In this example, compared with Example 1, only the following points are different. The conditions for calcining the ball-milled first preliminary coating particle sample are different. Specifically, it was calcined at 500 °C for 22 h.

[0108] Example 10 Manufacturing method of layered oxide cathode material:

[0109] In this example, compared with Example 1, only the following points are different. The conditions for calcining the ball-milled first preliminary coating particle sample are different. Specifically, it was calcined at 1100 °C for 1 h.

[0110] Example 11 Manufacturing method of layered oxide cathode material:

[0111] In this example, compared with Example 2, only the following points are different. The conditions for calcining the ball-milled second preliminary coating particle sample are different. Specifically, it was calcined at 300 °C for 22 h.

[0112] Example 12 Manufacturing method of layered oxide cathode material:

[0113] In this example, compared with Example 2, only the following points are different. The conditions for calcining the ball-milled second preliminary coating particle sample are different. Specifically, it was calcined at 1100 °C for 0.2 h.

[0114] Comparative Example 1 Manufacturing method of layered oxide cathode material:

[0115] In this comparative example, compared with Example 1, only the following points are different. The O3-phase cathode material NaNi 0.45 Mn 0.4 Ti 0.1 Cu 0.05 O2 was used as the cathode material as it was without coating.

[0116] The scanning electron microscope image of this O3-phase cathode material is shown in Fig. 2, and the XRD test pattern is shown in Fig. 4.

[0117] Comparative Example 2 Method for manufacturing a layered oxide cathode material:

[0118] In this comparative example, compared with Example 1, only the following points are different. The obtained O3@P2 phase composite oxide particles having a P2 phase metal oxide coating layer were used as the cathode material as they were without coating an inert coating layer.

[0119] Comparative Example 3 Method for manufacturing a layered oxide cathode material:

[0120] In this comparative example, compared with Example 1, only the following points are different. A P2 phase metal oxide coating layer was not coated, that is, the O3 phase cathode material particles NaNi 0.45 [[ID=二十一]]Mn 0.4 Ti 0.1 Cu 0.05 210 g of O2 and 0.2 g of expanded graphite were directly put into a ball milling tank, the ball milling time was 3 h, the rotation speed was 450 rmp, and preliminary coated particles were obtained. The preliminary coated particles were sufficiently dried and pulverized to obtain a cathode material.

[0121] Comparative Example 4 Method for manufacturing a layered oxide cathode material:

[0122] In this comparative example, compared with Example 1, only the following points are different. After obtaining O3 phase cathode material NaNi 0.45 Mn 0.4 Ti 0.1 Cu 0.05 O2, 1 g of a mixture of the first metal source and expanded graphite (weight ratio of both is 1:1) and 20 g of the O3 phase cathode material NaNi 0.45 Mn 0.4 Ti 0.1 Cu 0.05 O2 were put into a ball milling tank, the ball milling time was 3 h, the rotation speed was 450 rmp, and preliminary coated particles were obtained. The preliminary coated particle sample was put into a muffler furnace, calcined at 900 °C for 10 h, cooled and pulverized to obtain a cathode material.

[0123] Specifically, a mixed coating layer was formed by applying a single layer of a mixture of the P2 phase metal oxide coating material and the inert coating material.

[0124] Battery combinations (1) Preparation of positive electrode plate: The layered oxide positive electrode material, conductive carbon black, and polyvinylidene fluoride (PVDF) produced in each of the above examples and comparative examples are mixed in a mass ratio of 8:1:1, and an appropriate amount of N-methylpyrrolidone (NMP) is added to form a uniform electrode slurry. Then, the electrode slurry is uniformly applied to aluminum foil, vacuum dried, cut into a circular electrode plate with a diameter of 15 mm, and placed in a glove box.

[0125] (2) Battery assembly: A CR2032 button cell was assembled using metallic sodium as the counter electrode, glass fiber as the separator, sodium perchlorate as the solute of the electrolyte, and propylene carbonate, ethylene carbonate, and fluoroethylene carbonate (volume ratio 1:1:0.05) as the solvent of the electrolyte, with a sodium perchlorate concentration of 1 mol / L in the electrolyte. The entire assembly process was carried out in a glove box filled with argon gas. After the button cell was left for 6 hours, it was used for subsequent measurement of its electrochemical properties.

[0126] 2.Measurement method

[0127] Coverage ratio of P2 phase metal oxide coating layer and inert coating layer: The percentage of the total surface area of ​​the electrode material covered by the coating layer was measured by infrared spectroscopy.

[0128] Particle size: GB / T 19077. Particle size analysis by laser diffraction.

[0129] Compression density: GB / T 24533 Powder compression density measurement.

[0130] pH value: GB / T 9724 General rules for pH measurement of chemical reagents.

[0131] Moisture content: GB / T 6283 Karl Fischer method (a common method) for measuring the moisture content in chemical products.

[0132] Specific surface area: GB / T 19587 The specific surface area of ​​the solid material was measured by the gas adsorption BET method.

[0133] Scanning electron microscope image: Taken with a ZEISS MERLIN Compact, 50k magnification.

[0134] Measurement of electrochemical properties: Using a constant current charge / discharge mode, charge / discharge tests were performed at a current density of 0.1C, with a charge cutoff voltage of 4.2V and a discharge cutoff voltage of 2.0V. The initial charge / discharge capacity and Coulomb efficiency of each battery were measured.

[0135] Air Stability: The positive electrode materials obtained in each of the above examples and comparative examples were exposed to an air environment and maintained for 24 hours. After exposure to air, each positive electrode material was used to make a battery using the method described above, and its initial charge / discharge capacity and Coulomb efficiency were measured.

[0136] Table 1 shows the particle size distribution and coating status of each layer of the positive electrode material obtained in each example and comparative example, Table 2 shows the measurement results of the physical and chemical properties, and Table 3 shows the measurement results of the electrochemical properties of each manufactured battery.

[0137] 3. Analysis of measurement results for each example and comparative example.

[0138] [Table 1]

[0139] [Table 2]

[0140] [Table 3]

[0141] From the above results, it was found that in the above embodiments of the present invention, a good coating effect was achieved, the P2 phase metal oxide coating layer reduced the alkali residue on the surface of the O3 phase nickel-manganese layered oxide, and the inert coating layer reduced side reactions occurring between the material surface and air and electrolyte. The above experiments suggested that the two-layer coating of the P2 phase metal oxide coating layer and the inert coating layer affected the particle size, specific surface area, pH value, moisture content, and compressive density of the material, and that with appropriate nickel-manganese cathode material, coating amount, and ball milling conditions, the layered oxide cathode material exhibits high electrochemical properties and good air stability. When this layered oxide cathode material is used in a sodium-ion battery, the manufactured sodium-ion battery has high initial cycle Coulomb efficiency, excellent rate characteristics, long cycle life, and good air stability. Furthermore, the method for manufacturing the layered oxide cathode material according to the present invention is simple and practical, suitable for mass production, and has promising applicability.

[0142] Furthermore, this application is not limited to the embodiments described above. The embodiments described above are merely illustrative, and any embodiment that has substantially the same configuration as the technical concept and exhibits the same effects within the scope of the technical solutions of this application is included within the scope of this application. In addition, other forms constructed by adding various modifications to the embodiments that a person skilled in the art could conceive, or by combining some of the components of the embodiments, are also included within the scope of this application, as long as they do not depart from the spirit of this application.

Claims

1. A layered oxide cathode material comprising O3@P2 phase composite oxide particles and an inert coating layer coated on the surface of the O3@P2 phase composite oxide particles, wherein the O3@P2 phase composite oxide particles comprise O3 phase nickel-manganese oxide layered particles and a P2 phase metal oxide coating layer coated on the surface of the O3 phase nickel-manganese oxide layered particles, and the inert coating layer is a carbon layer and / or an inorganic metal oxide layer.

2. The molecular formula of the O3 phase nickelmanganese oxide layered particles is Na ｘ Ni ａ Mn ｂ M1 ｃ O ２ (However, 0.8 ≤ x ≤ 1.0, a + b + c = 1.0, and a, b, and c are all positive numbers, and M1 is one or more selected from Fe, Ti, Mg, Cu, Al, Ca, Zn, and Co.) Preferably, the layered oxide cathode material according to claim 1 is characterized in that M1 is one or more selected from Fe, Ti, Mg, Cu, Zn, and Ca.

3. The molecular formula of the P2 phase metal oxide coating layer is Na ｙ M2O ２ (However, 0.6 ≤ y ≤ 0.8, and M2 is one or more selected from Ni, Mn, Fe, Ti, Mg, Cu, Al, Ca, and Co.) Preferably, the layered oxide cathode material according to claim 1 is characterized in that M2 is one or more selected from Fe, Mn, Mg, Cu, and Ca.

4. The inorganic metal oxide layer is Al ２ O ３ layer, TiO ２ layer, CuO layer, and MgO layer, and is one or more selected therefrom, Preferably, the inorganic metal oxide layer is Al ２ O ３ layer, TiO ２ The layered oxide cathode material according to any one of claims 1 to 3, characterized in that it is one or more selected from the layers and the MgO layer.

5. In the O3 phase nickel-manganese oxide layered particles, M1 is Ti, and in the P2 phase metal oxide coating layer, M2 is one or more selected from Fe, Cu, and Mn, or The layered oxide cathode material according to claim 4, characterized in that M1 in the O3 phase nickel-manganese oxide layered particles is Cu or Ti and Cu, and M2 in the P2 phase metal oxide coating layer is one or more selected from Mg, Cu, and Mn.

6. The molecular formula of the O3 phase nickel-manganese oxide layered particles is NaNi ０．５ Mn ０．４ Ti ０．１ O ２ The molecular formula of the P2 phase metal oxide coating layer is Na ９／７ Cu ２／９ Fe １／９ Mn ２／３ O ２ The inert coating layer is Al ２ O ３ It is a layer, or, The molecular formula of the O3 phase nickel-manganese oxide layered particles is NaNi ０．４５ Mn ０．４ Ti ０．１ Cu ０．０５ O ２ The molecular formula of the P2 phase metal oxide coating layer is Na ０．６ Mg ０．１５ Cu ０．１５ Mn ０．７ O ２ The layered oxide cathode material according to claim 4, characterized in that the inert coating layer is the carbon layer.

7. The thickness of the P2 phase metal oxide coating layer is 2 nm to 100 nm, and the thickness of the inert coating layer is 2 nm to 100 nm. Preferably, with respect to the weight of the layered oxide cathode material being 100%, the P2 phase metal oxide coating layer is 0.5% to 5% by mass, and the inert coating layer is 0.5% to 5% by mass. Preferably, the layered oxide cathode material according to any one of claims 1 to 3, characterized in that the coverage of the P2 phase metal oxide coating layer on the surface of the O3 phase nickel manganese-based oxide layered particles is 80% to 100%, and the coverage of the inert coating layer on the surface of the O3@P2 phase composite oxide particles is 80% to 100%.

8. The process involves providing O3-phase nickel-manganese oxide layered particles and a first metal source, mixing the O3-phase nickel-manganese oxide layered particles with the first metal source, and performing a first ball milling to obtain first pre-coated particles. The first step of subjecting the first pre-coated particles to a first calcination treatment to obtain the O3@P2 phase composite oxide particles, The steps include mixing the O3@P2 phase composite oxide particles with a carbon source and / or a second metal source, and performing a second ball milling to obtain second pre-coated particles, A method for producing a layered oxide cathode material according to any one of claims 1 to 7, comprising the step of subjecting the second pre-coated particles to an optional second calcination treatment to obtain the layered oxide cathode material.

9. The method for producing a layered oxide cathode material according to claim 8, characterized in that the first ball milling has a rotational speed of 100 rpm to 500 rpm and a duration of 0.5 h to 4 h, and / or the second ball milling has a rotational speed of 100 rpm to 500 rpm and a duration of 0.5 h to 4 h.

10. The weight ratio of the O3-phase nickel-manganese oxide layered particles to the first metal source is 1:(0.005 to 0.05), and the weight ratio of the O3@P2-phase composite oxide particles to the carbon source and / or the second metal source is 1:(0.005 to 0.05), Preferably, the first metal source comprises a sodium source and a coated metal source, wherein the coated metal source is one or more selected from oxides, hydroxides, carbonates, sulfates, oxalates, acetates, and citrates corresponding to Fe, Ti, Mg, Cu, Al, Ca, Zn, and Co, and the sodium source is one or more selected from sodium carbonate, sodium hydroxide, sodium nitrate, and sodium peroxide. Preferably, the carbon source is one or more selected from coal tar, coal pitch, petroleum pitch, expanded graphite, carbon black, and graphene, and the second metal source is one or more selected from oxides, hydroxides, and carbonates corresponding to Ni, Mn, Fe, Ti, Mg, Cu, Al, Ca, and Co, characterized in that this is the method for producing a layered oxide cathode material according to 8 or 9.

11. The first calcination treatment is performed at a temperature of 600°C to 1000°C and for a calcination time of 2 hours to 20 hours, and the second calcination treatment is performed at a temperature of 400°C to 1000°C and for a calcination time of 0.5 hours to 20 hours. Preferably, the scalding atmosphere for the first scalding treatment is an air and / or oxygen atmosphere, characterized in that the method for producing a layered oxide cathode material according to claim 10.

12. When mixing the O3@P2 phase composite oxide particles with the second metal source, the second calcination treatment is performed, and the second calcination treatment is performed at a temperature of 700°C to 1000°C for a duration of 10 to 20 hours, and in an atmosphere of air and / or oxygen. When the O3@P2 phase composite oxide particles and the carbon source are mixed, and the carbon source is one or more selected from coal tar, coal pitch, and petroleum pitch, the second calcination treatment is performed, and the second calcination treatment is performed at a temperature of 400°C to 800°C for a duration of 0.5 h to 2 h, and in an atmosphere of nitrogen and / or argon. A method for producing a layered oxide cathode material according to claim 11, characterized in that the O3@P2 phase composite oxide particles and the carbon source are mixed, and the carbon source is one or more selected from expanded graphite, carbon black, and graphene, and the layered oxide cathode material is obtained after the second ball milling without performing the second calcination treatment.

13. A positive electrode plate characterized by comprising a layered oxide positive electrode material according to any one of claims 1 to 7, or a layered oxide positive electrode material manufactured by a method for manufacturing a layered oxide positive electrode material according to any one of claims 8 to 12.

14. A sodium-ion battery characterized by including the positive electrode plate described in claim 13.

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