Layered oxide cathode material, method of manufacturing the same, cathode plate, and sodium ion battery

Abstract

The present invention provides a layered oxide cathode material belonging to the technical field of sodium ion batteries, a method for manufacturing the same, a cathode plate, and a sodium ion battery. Herein, the layered oxide cathode material comprises O3@P2 phase composite oxide particles and an inert coating layer coated on the surface thereof, wherein the O3@P2 phase composite oxide particles comprise O3 phase nickel-manganese-based oxide layered particles and a P2 phase metal oxide coating layer coated on the surface of the O3 phase nickel-manganese-based oxide layered particles; and 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 applied to a sodium ion battery, the manufactured sodium ion battery has a high first-cycle Coulomb efficiency, excellent rate capability, long cycle life, and good air stability.

Description

Technology Field

[0001] The present invention relates to the technical field of sodium ion batteries, and specifically to a layered oxide cathode material, a method for manufacturing the same, a cathode plate, and a sodium ion battery. Background Technology

[0002] Although lithium-ion batteries are widely used in fields such as electric vehicles, home appliances, and energy storage, their large-scale application is severely limited due to problems such as low lithium resource reserves, uneven distribution, and large price fluctuations. Since sodium resources are more widely distributed in the Earth's crust and easier to obtain than lithium resources, sodium-ion batteries have greater price advantages and are expected to be applied on a large scale in the energy storage sector.

[0003] Sodium-ion batteries share an operating principle similar to that of lithium-ion batteries, and they achieve energy storage and release by utilizing the desorption and insertion of sodium ions between the anode and cathode. Currently, cathode materials for sodium-ion batteries primarily consist of layered transition metal oxides, polyionic compounds, and Prussian blue analogs; among these, layered transition metal oxide cathode materials are attracting increasing research and interest due to their high sodium storage capacity. Here, layered transition metal oxides can be classified mainly into P2 and O3 types based on the sodium ion coordination environment and the interlayer stacking order. The letters P and O represent deltaic and octahedral sodium ion coordination environments, respectively, while the numbers 2 and 3 represent the interlayer stacking orders ABBA and ABCABC, respectively. In this context, P2 phase materials are a sodium-deficient phase (generally having a sodium content of less than 0.67); if these are used in the manufacture of sodium-ion batteries, the resulting first-cycle charge capacity is low, requiring a separate sodium replenishment process, which is disadvantageous for practical application; O3 phase materials are a sodium-rich phase (generally having a sodium content close to 1.0), and when used in the manufacture of sodium-ion batteries, the resulting sodium-ion batteries have high charge-discharge capacities, so O3 phase materials have the potential to become commercial sodium-ion battery cathode materials. However, the sodium element abundant in O3 phase cathode materials reacts easily with moisture and carbon dioxide in the air, and the high residual alkali content on the surface of the material leads to the formation of low-conductivity materials such as sodium carbonate, sodium hydroxide, and sodium bicarbonate, which affect the performance of the manufactured sodium-ion batteries, including the first cycle Coulomb efficiency and reversible capacity.

[0004] Based on this, a method to remove or effectively utilize residual alkali on the surface of the O3-phase layered oxide sodium ion battery cathode material and to improve the air stability of the O3-phase layered oxide sodium ion battery cathode material is a technical challenge that needs to be urgently solved in this field. means of solving the problem

[0005] The main objective of the present invention is to provide a layered oxide cathode material, a method for manufacturing the same, a cathode plate, and a sodium ion battery to solve the problem of degraded electrochemical performance of a sodium ion battery due to residual alkali and low air stability present in the cathode material of the prior art.

[0006] A first aspect of the present invention for achieving the above objective provides 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-based oxide layered particles and a P2 phase metal oxide coating layer coated on the surface of the O3 phase nickel-manganese-based oxide layered particles; and wherein the inert coating layer is a carbon layer and / or an inorganic metal oxide layer.

[0007] In the technical solution of the embodiment of the present application, considering the disadvantages present in conventional sodium ion battery cathode materials, a layered oxide cathode material having a double-layer coating structure is provided, wherein the P2 phase metal oxide coating layer reduces the residual alkali content on the surface of the O3 phase nickel-manganese-based oxide layered particles and provides a good transport channel for sodium ions, and the inert coating layer delays the side reaction between the outer surface of the layered oxide cathode material and 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 Mnb M1 c O2, and in the above formula 0.8≤x≤1.0, a+b+c=1.0, a, b, and c are all integers, 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 inventor discovered that by selecting and optimizing the type of O3-phase nickel-manganese oxide layered particles through numerous experiments, when the components are in 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 at the same time, the O3-phase nickel-manganese oxide layered particles can better blend and cooperate with the P2-phase metal oxide coating layer.

[0010] Furthermore, the molecular formula of the P2 phase metal oxide coating layer is Na y M2O2; in the above formula, 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 embodiment, the inventor discovered that by selecting and optimizing the type of P2 phase metal oxide coating layer through numerous experiments, when the components are in a stoichiometric ratio with the elemental composition of the above molecular formula, the amount of residual alkali on the surface of the O3 phase nickel-manganese oxide layered particles can be reduced more effectively, and the air stability of the P2 phase metal oxide coating layer can be effectively improved.

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

[0013] In this embodiment, compared to an inorganic metal oxide layer formed of another metal, the inorganic metal oxide layer has a more stable structure and can better suppress side reactions between the O3@P2 phase composite oxide particles and the electrolyte. Based on this, the inventors have discovered that by further optimizing the inorganic metal oxide layer to be one or more selected from an Al2O3 layer, a TiO2 layer, and an MgO layer, these inorganic metal oxide layers can cooperate more synergistically with the preferred P2 phase metal oxide coating layer, while also being more cost-effective, thereby effectively enhancing the product added value of the manufactured layered oxide cathode material.

[0014] Furthermore, M1 in the O3 phase nickel-manganese oxide layered particle 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 particle 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, the inventor discovered through numerous experiments and comparisons that if M2 in the P2 phase metal oxide coating layer and M1 in the O3 phase nickel-manganese oxide layered particles are combined in the manner described above, the P2 phase metal oxide coating layer and the O3 phase nickel-manganese oxide layered particles can be bonded more effectively, and at the same time, residual alkali on the surface of the O3 phase nickel-manganese oxide can be removed more effectively, thereby improving the air stability of the resulting layered oxide cathode material.

[0016] Furthermore, 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, and 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 It is O2, and the inert coating layer is a carbon layer.

[0017] In the present embodiment, when the O3 phase nickel-manganese-based oxide layered particles serving as the core, the P2 phase metal oxide coating layer serving as the first coating layer, and the inert coating layer serving as the second coating layer are installed in the above two ways in the layered oxide cathode material, the resulting layered oxide cathode material not only has excellent electrochemical performance but also higher air stability, thereby better meeting actual application 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 nm to 100 nm; preferably, based on 100% of the weight of the layered oxide cathode material, the mass fraction of the P2 phase metal oxide coating layer is 0.5% to 5%, and the mass fraction of the inert coating layer is 0.5% to 5%; 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 the present embodiment, when 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 better improving the electrochemical performance of the cathode material. When the two coating layers are installed in the above weight ratios, synergy and mass transfer can be better achieved between each coating layer and between the P2 phase metal oxide coating layer and the core particle, and the electrochemical performance of the obtained cathode material is also higher. In addition, in some representative embodiments, the coverage rate of the P2 phase metal oxide coating layer on the surface of the O3 phase nickel-manganese-based oxide layered particle is 80% to 100%; and the coverage rate of the inert coating layer on the surface of the O3@P2 phase composite oxide particle is 80% to 100%. In the structure of the layered oxide cathode material according to the present invention, the coverage rate of each coating layer can reach 80% and above, that is, by realizing a good, complete, and uniform coating structure, the air stability of the obtained layered oxide cathode material is further improved.

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

[0021] In the technical solution of the embodiment of the present application, a primary metal source and O3-phase nickel-manganese oxide layered particles are first pre-coated to improve the bonding strength between the two, and then a P2-phase metal oxide coating layer is created in-situ on the surface of the O3-phase nickel-manganese oxide layered particles through an in-situ solid-state reaction, thereby significantly consuming residual alkali on the surface and improving air stability. Next, O3@P2-phase composite oxide particles and a carbon source and / or secondary metal source are ball-milled and pre-coated, and an inert coating layer is created again through an in-situ solid-state reaction. Compared to simple mixed coating or liquid-state reaction, this method better synergizes the physicochemical performance between each coating layer and protects the structural integrity of the core particles and the coating layer, while simplifying the process to obtain a layered oxide cathode material with better performance and higher product added value. At the same time, the layered oxide cathode material according to the present invention has a simple manufacturing method and high compatibility with conventional manufacturing processes, making it easy for large-scale industrial application.

[0022] Furthermore, the rotational speed of the first ball milling is 100 rpm to 500 rpm and the time is 0.5 h to 4 h; and / or, the rotational speed of the second ball milling is 100 rpm to 500 rpm and the time is 0.5 h to 4 h.

[0023] In this embodiment, by setting the experimental conditions for two ball millings in the manner described above, a more uniform coating can be achieved, thereby improving the component uniformity, structural continuity, and coating integrity of the obtained P2 phase metal oxide coating layer and inert coating layer.

[0024] Furthermore, the weight ratio of O3-phase nickel-manganese-based oxide layered particles to a primary metal source is 1:(0.005 to 0.05), and the weight ratio of O3@P2-phase composite oxide particles to a carbon source and / or a secondary metal source is 1:(0.005 to 0.05); preferably, the primary metal source comprises a sodium source and a coating metal source, and 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, 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 tar pitch, petroleum pitch, expanded graphite, carbon black, and graphene, and the secondary 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 inventor discovered that by optimizing the weight ratio relationship through numerous experiments and simultaneously correlating the weight ratio and coating thickness of the P2 phase metal oxide coating layer and the inert coating layer, the various electrochemical performances and air stability of the resulting layered oxide cathode material can be more effectively improved when the material is manufactured according to the weight ratio relationship. Through numerous comparative tests, the inventor discovered that by optimizing the aforementioned coating metal sources and sodium sources, selecting the aforementioned types allows the solid-state reaction to proceed more smoothly, thereby enabling the formation of the P2 phase metal oxide coating layer and facilitating the securing of a cathode material with the expected structure. Similarly, through numerous comparative tests, the inventor discovered that by optimizing the aforementioned carbon sources and secondary metal sources, selecting the aforementioned types allows the inert coating layer to be formed smoothly in a more continuous, uniform, and dense state, thereby enabling the acquisition of a layered oxide cathode material with excellent performance.

[0026] Furthermore, the temperature of the first firing treatment is 600℃ to 1000℃ and the firing time is 2h to 20h, the temperature of the second firing treatment is 400℃ to 1000℃ and the firing time is 0.5h to 20h; preferably, the firing atmosphere of the first firing treatment is an air and / or oxygen atmosphere.

[0027] In this embodiment, the inventor discovered that by optimizing the temperature and time conditions of the two firings through numerous experiments, the structure of the two coating layers obtained is more stable when proceeding in this manner, that is, the surface of the P2 phase metal oxide coating layer and the O3 phase nickel-manganese oxide layered particle is bonded, and the surface of the inert coating layer and the O3@P2 phase composite oxide particle is bonded more closely, and thus the air stability of the layered oxide cathode material produced is better.

[0028] More preferably, the firing atmosphere of the first firing treatment is an air and / or oxygen atmosphere, and the inventor improves ion conductivity by performing the first firing under conditions where air is present, thereby forming a P2 phase metal oxide coating layer more efficiently.

[0029] Furthermore, when O3@P2 phase composite oxide particles and a secondary metal source are mixed, a secondary calcination treatment is performed, wherein the temperature of the secondary calcination treatment is 700°C to 1000°C, the time is 10h to 20h, and the atmosphere is an air and / or oxygen atmosphere; at this time, the inert coating layer is an inorganic metal oxide layer, and the inventor improves the air stability of the finally formed layered oxide cathode material by optimizing the above conditions through numerous experiments to form an inert coating layer with a more stable structure and a dense structure.

[0030] In the present embodiment, when O3@P2 phase composite oxide particles and a carbon source are mixed and the carbon source is one or more selected from coal tar, coal tar pitch, and petroleum pitch, a secondary calcination treatment is performed, wherein the temperature of the secondary calcination treatment is 400°C to 800°C, the time is 0.5h to 2h, and the atmosphere is a nitrogen atmosphere and / or an argon atmosphere; at this time, since the inert coating layer is a carbon layer and the carbon source contains various small molecule organic materials, the inventor improved the air stability of the finally formed layered oxide cathode material by optimizing the above conditions through numerous experiments to obtain a more complete and stable carbon layer by removing organic small molecules from coal tar, coal tar pitch, and petroleum pitch while simultaneously completing carbonization.

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

[0032] A third aspect of the present invention provides an anode plate comprising the layered oxide anode material.

[0033] In this embodiment, since the anode plate includes the layered oxide anode material, it has high electrochemical performance and also good air stability.

[0034] A fourth aspect of the present invention provides a sodium ion battery comprising the positive plate.

[0035] Since the cathode material obtained by the present invention simultaneously possesses good electrochemical performance and structural stability, when applied to a sodium ion battery as a cathode plate component, the resulting sodium ion battery also possesses overall improved electrochemical performance, including improved first-cycle Coulomb efficiency, excellent rate capability, long cycle life, and good air stability, so it can be well applied to various usage scenarios.

[0036] The above description is merely an overview of the technical solution of the present application, and may be implemented in accordance with the contents of the specification to better understand the technical solution of the present application. Furthermore, specific embodiments of the present invention are specifically provided below as examples to make the above and other purposes, features, and advantages of the present application more clearly apparent. Brief explanation of the drawing

[0037] Hereinafter, the drawings used in this application are briefly described to more clearly explain the technical solution of this application. The drawings described below are merely some embodiments of this application, and it is obvious to those skilled in the art that other drawings can be obtained based on these drawings without creative effort. Figure 1 is a scanning electron microscope image of the layered oxide cathode material obtained in Example 1. Figure 2 is a scanning electron microscope image of the layered oxide cathode material obtained in Comparative Example 1. Figure 3 is the XRD spectrum of the layered oxide cathode material obtained in Example 1. Figure 4 is the XRD spectrum of the layered oxide cathode material obtained in Comparative Example 1. Specific details for implementing the invention

[0038] Hereinafter, embodiments of the technical solution of the present application will be described in detail with reference to the attached drawings. The following embodiments are used merely to more clearly explain the technical solution of the present application and are therefore used only as examples and do not limit the scope of protection of the present invention.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as understood by those skilled in the art; terms used herein are merely for describing specific embodiments and are not intended to limit the application; and in the specification, claims, and description of the drawings, the terms “comprising,” “having,” and any variations thereof are intended to encompass non-exclusive inclusions.

[0040] In the description of the embodiments of this application, technical terms such as “first,” “second,” etc., are used merely to distinguish different objects and should not be understood as indicating or implying relative importance, or implying the number, specific order, or priority relationship of the indicated technical features. In the description of the embodiments of this application, “plural” means two or more unless otherwise explicitly and specifically limited.

[0041] The term “Examples” as used herein means that specific features, structures, or characteristics described with reference to the Examples may be included in at least one Example of this Application. The phrases appearing at each location in the Specification do not necessarily refer to the same Example, nor are they independent or alternative Examples mutually exclusive from other Examples. Those skilled in the art will understand, either explicitly or implicitly, that the Examples described herein may be combined with other Examples.

[0042] In the description of the embodiments of the present application, the term "and / or" is merely an association relationship describing an associated object, implying that three relationships exist; for example, A and / or B means three cases: only A exists, A and B exist simultaneously, and only B exists. Additionally, in this specification, the symbol " / " generally indicates that the preceding and succeeding associated objects are in an "or" relationship.

[0043] In the description of the embodiments of the present application, the term “multiple” means two or more (including two), likewise “multiple groups” means two or more groups (including two groups), and “multiple sheets” means two or more sheets (including two sheets).

[0044] In the description of the embodiments of the present application, the orientation or positional relationship indicated by technical terms such as “center,” “longitudinal,” “transverse,” “length,” “width,” “thickness,” “top,” “bottom,” “front,” “back,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inside,” “outside,” “clockwise,” “counterclockwise,” “axial,” “radial,” “circumferential,” etc., is based on the orientation or positional relationship illustrated in the drawings and is intended only to facilitate and simplify the description of the embodiments of the present application. It does not indicate or imply that the mentioned device or element must necessarily have a specific orientation or be configured and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0045] In the description of the embodiments of this application, unless otherwise explicitly specified or limited, technical terms such as “mounting,” “connecting,” “connecting,” and “fixing” should be understood in a broad sense, for example, they may be fixed connections, detachable connections, or integral; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; or communication within two elements or an interactive relationship between two elements. Those skilled in the art may understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0046] As explained in the background art, conventional sodium ion battery cathode materials have the problem of degrading the electrochemical performance of sodium ion batteries due to the presence of residual alkali and low air stability. A first aspect of the present invention to solve the above technical problem provides 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.

[0047] The layered oxide cathode material according to the present invention comprises an O3-phase nickel-manganese-based oxide layered particle core, a first P2-phase metal oxide coating layer coated thereon, and a second inert coating layer; the first layer's P2-phase metal oxide coating layer reduces the residual alkali content on the surface of the O3-phase nickel-manganese-based oxide layered particle and provides good sodium ion transport channels, and the inert coating layer delays side reactions between the outer surface of the layered oxide cathode material and air and electrolyte, thereby exhibiting overall high electrochemical performance and good air stability of the layered oxide cathode material.

[0048] Specifically, the P2 phase metal oxide coating layer and the inert coating layer cooperate to synergistically improve the overall electrochemical performance of the O3 phase nickel-manganese oxide layered particles. Among these, the inert coating layer is stable, uniform, and dense, and when coated on the outermost surface and in direct contact with the electrolyte, it can more effectively reduce side reactions between the manufactured layered oxide cathode material and the electrolyte, thereby reducing the erosion of the cathode active components by HF generated by side reactions and extending the service life. At the same time, the inert coating layer, which has a certain flexibility, can also effectively suppress the occurrence of internal cracks in the cathode material particles. However, when the inert coating layer and the O3 phase nickel-manganese oxide layered particles come into direct contact, the diffusion channels of metal ions within the core become blocked, affecting the electrochemical performance of the cathode material. Considering this, the present invention adopts a form in which a P2 phase metal oxide coating layer and an inert coating layer are sequentially coated. Among these, the P2 phase metal oxide coating layer has a lower ability to suppress side reactions with electrolytes, air, etc., but has high ionic conductivity, which can effectively reduce the charge transfer resistance on the surface of O3 phase nickel-manganese oxide layered particles.

[0049] The inventor comprehensively considered the above situation and, through numerous experimental verifications, combined and used a P2 phase metal oxide coating layer and an inert coating layer. Specifically, a P2 phase metal oxide coating layer with good ion conductivity and capable of significantly consuming residual alkali is coated on the surface of O3 phase nickel-manganese oxide layered particles, and then an inert coating layer is coated on the surface of the P2 phase metal oxide coating layer, and the inert coating layer is brought into direct contact with the electrolyte. By synergizing the advantages of the two coating layers, the present invention improves the electrochemical performance of the layered oxide cathode material obtained at the end, thereby improving the first cycle Coulomb efficiency, rate capability, and cycle life of a sodium ion battery manufactured using the cathode material.

[0050] Furthermore, the molecular formula of the O3-phase nickel-manganese oxide layered particles is Na x Ni a Mn b M1 c O2 is O2, where 0.8≤x≤1.0 and a+b+c=1.0 in the above formula, a, b, and c are all integers, and M1 is one or more selected from Fe, Ti, Mg, Cu, Al, Ca, Zn, and Co. Through numerous experiments, the inventor selected and optimized the type of O3-phase nickel-manganese oxide layered particles and discovered that electrochemical performance is superior when the components are in stoichiometric ratios with the elemental composition of the above molecular formula. Based on this, further optimization was performed so that M1 is one or more selected from Fe, Ti, Mg, Cu, Zn, and Ca. When using the above metal elements, the O3-phase nickel-manganese oxide layered particles have various electrochemical performances further improved, and at the same time, they may better blend and cooperate with the coating layer above them.

[0051] In some representative embodiments, the molecular formula of the P2 phase metal oxide coating layer is Na yM2O2; in the above formula, 0.6≤y≤0.8, and M2 is one or more 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 discovered that when the components are in stoichiometric ratios with the elemental composition of the above molecular formula, the amount of residual alkali on the surface of the O3 phase nickel-manganese oxide layered particles is reduced more effectively and the ionic conductivity is effectively improved. Based on this, the inventors further optimized through numerous experiments so that M2 is one or more selected from Fe, Mn, Mg, Cu, Zn, and Ca. When using the above metal elements, the resulting P2 phase metal oxide coating layer can more effectively reduce the charge transfer resistance on the surface of the O3 phase nickel-manganese oxide layered particles, thereby significantly improving the electrochemical performance of the resulting layered oxide cathode material.

[0052] Regarding the selection of an inert coating layer other than the carbon layer, the inventors, through numerous experiments, optimized several preferred embodiments such that the inorganic metal oxide layer is one or more selected from Al2O3, TiO2, CuO, and MgO layers. Compared to inorganic metal oxide layers formed of other metals, these inorganic metal oxide layers have a more stable structure and can better suppress side reactions between the O3@P2 phase composite oxide particles and the electrolyte. Based on this, the inventors discovered that by further optimizing the inorganic metal oxide layer to be one or more selected from Al2O3, TiO2, and MgO layers, these inorganic metal oxide layers can cooperate better with the preferred P2 phase metal oxide coating layer, while also being more cost-effective, thereby effectively enhancing the product added value of the obtained cathode material.

[0053] 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 serves to connect the O3-phase nickel-manganese oxide layered particles with the inert coating layer, whether good bonding with the O3-phase nickel-manganese oxide layered particles can be achieved is a very important factor. Through numerous experiments and comparisons, the inventor discovered that combining M2 in the P2 phase metal oxide coating layer and M1 in the O3 phase nickel-manganese oxide particles in the above manner allows the P2 phase metal oxide coating layer and the O3 phase nickel-manganese oxide layered particles to be better bonded, while simultaneously removing residual alkali from the surface of the O3 phase nickel-manganese oxide particles more effectively, thereby improving the electrochemical performance of the finally obtained layered oxide cathode material and improving the first cycle Coulomb efficiency, rate capability, and cycle life of the sodium ion battery manufactured using the cathode material.

[0054] Through numerous experiments, the inventor further optimized the core oxide and two coating layers of the layered oxide cathode material, so that in the two most representative embodiments, the molecular formula of the O3-phase nickel-manganese-based 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, and 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 Cu0.05 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 was discovered that in a layered oxide cathode material, where O2 is the core and the inert coating layer is a carbon layer, if the core O3 phase nickel-manganese-based oxide layered particle, the first coating layer P2 phase metal oxide coating layer, and the second coating layer inert coating layer are installed in the two ways described above, the resulting layered oxide cathode material not only has excellent electrochemical performance but also higher air stability, thereby better meeting actual application requirements.

[0055] In addition to the above-mentioned preferred elemental cooperation method, the inventors simultaneously discovered that the film layer thickness, mass ratio, and degree of coating influence each performance of the resulting layered oxide cathode material are equally significant during the experimental process. In a representative embodiment, the thickness of the P2 phase metal oxide coating layer in the layered oxide cathode material is 2 nm to 100 nm, and the thickness of the inert coating layer is 2 nm to 100 nm. When the thicknesses of the P2 phase metal oxide coating layer and the inert coating layer are within the above ranges, a better balance can be achieved between suppression of side reactions, consumption of residual alkali, and improvement of conductivity, thereby better improving the electrochemical performance of the resulting layered oxide cathode material. Regarding the weight ratio of the P2 phase metal oxide coating layer and the inert coating layer, in a preferred embodiment, based on 100% of the weight of the layered oxide cathode material, the mass fraction of the P2 phase metal oxide coating layer is 0.5% to 5%, and the mass fraction of the inert coating layer is 0.5% to 5%. When the two coating layers are installed in the respective weight ratios, synergy and mass transfer can be better achieved 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 particle, and the electrochemical performance of the resulting layered oxide cathode material is also higher. In addition, in some representative embodiments, the coverage rate of the P2 phase metal oxide coating layer on the surface of the O3 phase nickel-manganese-based oxide layered particle is 80% to 100%; and the coverage rate of the inert coating layer on the surface of the O3@P2 phase composite oxide particle is 80% to 100%. In the structure of the layered oxide cathode material according to the present invention, the coverage rate of the P2 phase metal oxide coating layer and the inert coating layer can reach 80% and above, that is, by realizing a good, complete, and uniform coating structure, the air stability of the layered oxide cathode material is further improved.

[0056] A second aspect of the present invention provides a method for manufacturing a layered oxide cathode material, comprising the steps of: preparing O3-phase nickel-manganese-based oxide layered particles and a primary metal source, mixing the O3-phase nickel-manganese-based oxide layered particles with the primary metal source, and then performing primary ball milling to obtain primary pre-coating particles; performing primary calcination treatment on the primary pre-coating particles to obtain O3@P2-phase composite oxide particles; mixing the O3@P2-phase composite oxide particles with a carbon source and / or a secondary metal source, and then performing secondary ball milling to obtain secondary pre-coating particles; and performing an optional secondary calcination treatment on the secondary pre-coating particles to obtain a layered oxide cathode material.

[0057] The manufacturing method according to the present invention is simple, and all related equipment and process conditions are readily available, and it is compatible with various manufacturing methods of conventional cathode materials. Specifically, first, a primary metal source and O3-phase nickel-manganese oxide layered particles are pre-coated to improve the bonding strength between them, and then, through an in-situ solid-state reaction, a P2-phase metal oxide coating layer is created in-situ on the surface of the O3-phase nickel-manganese oxide layered particles, thereby significantly consuming residual alkali on the surface and improving air stability. Next, O3@P2-phase composite oxide particles and a carbon source and / or secondary metal source are ball-milled and pre-coated, and an inert coating layer is created again through an in-situ solid-state reaction. Compared to simple mixed coating or liquid-state reaction, this method better synergizes the physicochemical performance between each coating layer and protects the structural integrity of the core particles and the coating layer, while simplifying the process to obtain a layered oxide cathode material with better performance and higher product added value.

[0058] To enhance the effect of the two-step pre-coating, preferably, the rotational speed of the first ball milling is 100 rpm to 500 rpm and the time is 0.5 h to 4 h; and / or, the rotational speed of the second ball milling is 100 rpm to 500 rpm and the time is 0.5 h to 4 h. By setting the experimental conditions for the two-step ball milling in the manner described above, a more uniform coating can be achieved, thereby improving the compositional uniformity, structural continuity, and coating integrity of the obtained P2 phase metal oxide coating layer and inert coating layer.

[0059] In order to better control the weight ratio and coating thickness of the P2 phase metal oxide coating layer and the inert coating layer, the inventors optimized the weight ratio of the O3 phase nickel-manganese-based oxide layered particles to the primary metal source to 1:(0.005–0.05) in several preferred embodiments, and the weight ratio of the O3@P2 phase composite oxide particles to the carbon source and / or secondary metal source to 1:(0.005–0.05). Through numerous experiments, the inventors optimized the above weight ratio relationship and simultaneously found that by correlating the weight ratio and coating thickness of the P2 phase metal oxide coating layer to the inert coating layer, the electrochemical performance and air stability of the resulting layered oxide cathode material can be more effectively improved when the material is prepared according to the above weight ratio relationship.

[0060] In some preferred embodiments, the primary metal source comprises a sodium source and a coating metal source, and 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. By optimizing the above coating metal source and sodium source through numerous comparative tests, the inventors discovered that when the above types are selected, the solid-state reaction proceeds more smoothly, enabling the formation of a P2 phase metal oxide coating layer, thereby facilitating the securing of a layered oxide cathode material of the expected structure.

[0061] In some preferred embodiments, the carbon source is one or more selected from coal tar, coal tar pitch, petroleum pitch, expanded graphite, carbon black, and graphene, and the secondary metal source is one or more selected from oxides, hydroxides, and carbonates corresponding to Ni, Mn, Fe, Ti, Mg, Cu, Al, Ca, and Co. Likewise, the inventors have discovered that by optimizing the carbon source and secondary metal source through numerous comparative tests, when the above types are selected, an inert coating layer can be smoothly formed in a more continuous, uniform, and dense state, thereby obtaining a layered oxide cathode material with excellent performance.

[0062] The present invention enables the formation of a P2 phase metal oxide coating layer and an inert coating layer through calcination and solid-state reaction, wherein in a representative embodiment, the temperature of the first calcination treatment is 600°C to 1000°C and the calcination time is 2h to 20h, the temperature of the second calcination treatment is 400°C to 1000°C and the calcination time is 0.5h to 20h; the inventors have discovered that by optimizing the temperature and time conditions of each of the two calcinations through numerous experiments, the structure of the two coating layers obtained when proceeding in this manner is more stable, that is, the surface of the P2 phase metal oxide coating layer and the O3 phase nickel-manganese-based oxide layered particles are bonded, and the surface of the inert coating layer and the O3@P2 phase composite oxide particles are bonded more closely, and thus the air stability of the manufactured layered oxide cathode material is better. More preferably, the firing atmosphere of the first firing treatment is an air and / or oxygen atmosphere, and the inventor improves ion conductivity by performing the first firing under conditions where air is present, thereby forming a P2 phase metal oxide coating layer more efficiently.

[0063] In some preferred embodiments,

[0064] When O3@P2 phase composite oxide particles and a secondary metal source are mixed, a secondary calcination treatment is performed, wherein the temperature of the secondary calcination treatment is 700°C to 1000°C, the time is 10h to 20h, and the atmosphere is an air and / or oxygen atmosphere; at this time, the inert coating layer is an inorganic metal oxide layer, and the inventor improves the air stability of the finally formed layered oxide cathode material by optimizing the above conditions through numerous experiments to form an inert coating layer with a more stable structure and a dense structure.

[0065] When O3@P2 phase composite oxide particles and a carbon source are mixed and the carbon source is one or more selected from coal tar, coal tar pitch, and petroleum pitch, a secondary calcination treatment is performed, wherein the temperature of the secondary calcination treatment is 400°C to 800°C, the time is 0.5h to 2h, and the atmosphere is a nitrogen atmosphere and / or an argon atmosphere; at this time, since the inert coating layer is a carbon layer and the carbon source contains various small molecule organic materials, the inventor improved the air stability of the finally formed layered oxide cathode material by optimizing the above conditions through numerous experiments to obtain a more complete and stable inert coating layer by removing organic small molecules from coal tar, coal tar pitch, and petroleum pitch while simultaneously completing carbonization.

[0066] When O3@P2 phase composite oxide particles and a carbon source are mixed and the carbon source is one or more selected from expanded graphite, carbon black, and graphene, a layered oxide cathode material is obtained immediately after secondary ball milling without performing a secondary calcination treatment; at this time, the inert coating layer is a carbon layer and the carbon source contains only elemental carbon, so a layered oxide cathode material is obtained immediately after secondary ball milling to simplify the process and shorten the cycle, and in this structure, the carbon layer achieves a complete and stable coating.

[0067] A third aspect of the present invention provides an anode plate comprising the layered oxide anode material.

[0068] A fourth aspect of the present invention provides a sodium ion battery comprising the positive plate.

[0069] Since the cathode material obtained by the present invention simultaneously possesses good electrochemical performance and structural stability, when applied to a sodium ion battery as a cathode plate component, the resulting sodium ion battery also possesses overall improved electrochemical performance, including improved first-cycle Coulomb efficiency, excellent rate capability, long cycle life, and good air stability, so it can be well applied to various usage scenarios.

[0070] The present application is described in more detail below with specific embodiments, but these embodiments should not be understood as limiting the scope of protection sought by the present application.

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

[0072] Some specific embodiments are listed below; however, the embodiments described below are illustrative and are intended only to interpret the invention and should not be understood as limiting the application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature of the art or in the product specifications. Where the manufacturer of the reagents or equipment used is not indicated, they are all general products available on the market.

[0073] A. Manufacturing method

[0074] Example 1

[0075] Method for manufacturing layered oxide cathode material:

[0076] First, O3 phase cathode material NaNi 0.45 Mn 0.4 Ti 0.1 Cu 0.05O2 was prepared. Sodium carbonate, nickel oxide, manganese dioxide, titanium dioxide, copper oxide, and a certain amount of anhydrous ethanol were weighed according to the stoichiometric ratio of their molecular formulas, placed in a ball mill, and mixed uniformly, with a mixing time of 3 hours and 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 placed in an air atmosphere and subjected to high-temperature calcination, with a calcination temperature of 900℃ and a temperature holding time of 15 hours.

[0077] Next, sodium carbonate, magnesium oxide, copper oxide, and manganese dioxide are weighed according to the stoichiometric ratios of the P2 phase molecular formula and sufficiently ground to obtain a primary metal source, after which 1 g of the primary metal source and 20 g of O3 phase cathode material NaNi 0.45 Mn 0.4 Ti 0.1 Cu 0.05 O2 is placed in a ball milling tank to obtain primary pre-coated particles by ball milling for a time of 3 hours at a rotation speed of 450 rpm; the ball-milled primary pre-coated particle sample is placed in a muffle furnace, calcined at 900°C for 10 hours, cooled, and then polished to obtain O3@P2 phase composite oxide particles having a P2 phase metal oxide coating layer, wherein the P2 phase molecular formula is Na 0.6 Mg 0.15 Cu 0.15 Mn 0.7 It is O2.

[0078] 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 to obtain secondary pre-coated particles with a ball milling time of 3 h and a rotation speed of 450 rmp; after sufficiently drying the ball-milled secondary pre-coated particle sample, it was polished to obtain a layered oxide cathode material having a P2 phase metal oxide coating layer and an inert coating layer, which is denoted as G@P2@O3, and a scanning electron microscope image of the obtained G@P2@O3 layered oxide cathode material is shown in Fig. 1, and an XRD test spectrum is shown in Fig. 3.

[0079] 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.

[0080] Example 2

[0081] Method for manufacturing layered oxide cathode material:

[0082] First, O3 phase cathode material NaNi 0.5 Mn 0.4 Ti 0.1 O2 was prepared. Sodium carbonate, nickel oxide, manganese dioxide, titanium dioxide, and a certain amount of anhydrous ethanol were weighed according to the stoichiometric ratio of their molecular formulas, placed in a ball mill, and mixed uniformly, with a mixing time of 3 hours and 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 placed in an air atmosphere and subjected to high-temperature calcination, with a calcination temperature of 900℃ and a temperature holding time of 15 hours.

[0083] Next, sodium carbonate, magnesium oxide, copper oxide, and manganese dioxide are weighed according to the stoichiometric ratios of the P2 phase molecular formula and sufficiently ground to obtain a primary metal source, after which 1 g of the primary metal source and 20 g of O3 phase cathode material NaNi 0.5 Mn 0.4 Ti 0.1 O2 is placed in a ball milling tank to obtain primary pre-coated particles by ball milling for a time of 3 hours at a rotation speed of 450 rpm; the ball-milled primary pre-coated particle sample is placed in a muffle furnace, calcined at 900°C for 10 hours, cooled, and then polished to obtain O3@P2 phase composite oxide particles having a P2 phase metal oxide coating layer, wherein the P2 phase molecular formula is Na 9 / 7 Cu 2 / 9 Fe 1 / 9 Mn 2 / 3 It is O2.

[0084] 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 to obtain a second pre-coated particle with a ball milling time of 3 h and a rotation speed of 450 rmp; the ball-milled second pre-coated particle sample was placed in a muffle furnace and fired at 600°C for 10 h, dried sufficiently, and then polished to obtain a layered oxide cathode material having a P2 phase metal oxide coating layer and an inert coating layer, which was designated as the Al2O3@P2@O3 layered oxide cathode material.

[0085] 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.

[0086] Example 3

[0087] Method for manufacturing layered oxide cathode material:

[0088] First, O3 phase cathode material NaNi 0.45 Mn 0.4 Ti 0.1 Fe 0.05 O2 was prepared. Sodium carbonate, nickel oxide, manganese dioxide, titanium dioxide, ferric oxide, and a certain amount of anhydrous ethanol were weighed according to the stoichiometric ratio of their molecular formulas, placed in a ball mill, and mixed uniformly, with a mixing time of 3 hours and a ball milling rotation 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 placed in an air atmosphere and high-temperature calcination was performed, with a calcination temperature of 900℃ and a temperature holding time of 15 hours.

[0089] Next, sodium carbonate, magnesium oxide, copper oxide, and manganese dioxide are weighed according to the stoichiometric ratios of the P2 phase molecular formula and sufficiently ground to obtain a primary metal source, after which 1 g of the primary metal source and 20 g of O3 phase cathode material NaNi 0.45 Mn 0.4 Ti 0.1 Fe 0.05O2 is placed in a ball milling tank to obtain primary pre-coated particles by ball milling for a time of 3 hours at a rotation speed of 450 rpm; the ball-milled primary pre-coated particle sample is placed in a muffle furnace, calcined at 900°C for 10 hours, cooled, and then polished to obtain O3@P2 phase composite oxide particles having a P2 phase metal oxide coating layer, wherein the P2 phase molecular formula is Na 0.6 Mg 0.15 Cu 0.15 Mn 0.7 It is O2.

[0090] 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 to obtain a second pre-coated particle with a ball milling time of 3 h and a rotation speed of 450 rmp; the ball-milled second pre-coated particle sample was placed in a muffle furnace and fired at 600°C for 10 h, dried sufficiently, and then polished to obtain a layered oxide cathode material having a P2 phase metal oxide coating layer and an inert coating layer, which was designated as the Al2O3@P2@O3 layered oxide cathode material.

[0091] 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.

[0092] Example 4

[0093] Method for manufacturing layered oxide cathode material:

[0094] First, O3 phase cathode material NaNi 0.45 Mn 0.4 Ti 0.1 Zn 0.05O2 was prepared. Sodium carbonate, nickel oxide, manganese dioxide, titanium dioxide, zinc oxide, and a certain amount of anhydrous ethanol were weighed according to the stoichiometric ratio of their molecular formulas, placed in a ball mill, and mixed uniformly, with a mixing time of 3 hours and 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 placed in an air atmosphere and subjected to high-temperature calcination, with a calcination temperature of 900℃ and a temperature holding time of 15 hours.

[0095] Next, sodium carbonate, magnesium oxide, copper oxide, and manganese dioxide are weighed according to the stoichiometric ratios of the P2 phase molecular formula and sufficiently ground to obtain a primary metal source, after which 1 g of the primary metal source and 20 g of O3 phase cathode material NaNi 0.45 Mn 0.4 Ti 0.1 Zn 0.05 O2 is placed in a ball milling tank to obtain primary pre-coated particles by ball milling for a time of 3 hours at a rotation speed of 450 rpm; the ball-milled primary pre-coated particle sample is placed in a muffle furnace, calcined at 900°C for 10 hours, cooled, and then polished to obtain O3@P2 phase composite oxide particles having a P2 phase metal oxide coating layer, wherein the P2 phase molecular formula is Na 0.6 Mg 0.15 Cu 0.15 Mn 0.7 It is O2.

[0096] 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 to obtain a second pre-coated particle with a ball milling time of 3 h and a rotation speed of 450 rmp; the ball-milled second pre-coated particle sample was placed in a muffle furnace, fired at 600°C for 10 h, sufficiently dried, and then polished to obtain a layered oxide cathode material having a P2 phase metal oxide coating layer and an inert coating layer, which was designated as the TiO2@P2@O3 layered oxide cathode material.

[0097] 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.

[0098] Example 5

[0099] Method for manufacturing layered oxide cathode material:

[0100] The only difference between this example and Example 1 is that the amounts of primary metal source and expanded graphite (i.e., carbon source) used are different. Specifically, the amounts of primary metal source and expanded graphite were changed so that the weight ratio of O3-phase nickel-manganese-based oxide layered particles to primary metal source is 1:0.002, and the weight ratio of O3@P2-phase composite oxide particles to carbon source is 1:0.002.

[0101] 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.

[0102] Example 6

[0103] Method for manufacturing layered oxide cathode material:

[0104] The only difference between this example and Example 1 is that the amounts of primary metal source and expanded graphite (i.e., carbon source) used are different. Specifically, the amounts of primary metal source and expanded graphite were changed so that the weight ratio of O3-phase nickel-manganese-based oxide layered particles to primary metal source was 1:0.08, and the weight ratio of O3@P2-phase composite oxide particles to carbon source was 1:0.08.

[0105] 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.

[0106] Example 7

[0107] Method for manufacturing layered oxide cathode material:

[0108] The only difference between this embodiment and Example 1 is that the conditions related to the two-step ball milling are different; specifically,

[0109] The ball milling time for obtaining the first pre-coating particles is 5h and the rotation speed is 50rmp; the ball milling time for obtaining the second pre-coating particles is 5h and the rotation speed is 50rmp.

[0110] Example 8

[0111] Method for manufacturing layered oxide cathode material:

[0112] The only difference between this embodiment and Example 1 is that the conditions related to the two-step ball milling are different; specifically,

[0113] The ball milling time for obtaining the first pre-coating particles is 0.4h and the rotation speed is 600 rpm; the ball milling time for obtaining the second pre-coating particles is 0.4h and the rotation speed is 600 rpm.

[0114] Example 9

[0115] Method for manufacturing layered oxide cathode material:

[0116] The only difference between this example and Example 1 is that the firing conditions for the ball-milled primary pre-coated particle samples are different, specifically, they are fired at 500°C for 22 hours.

[0117] Example 10

[0118] Method for manufacturing layered oxide cathode material:

[0119] The only difference between this example and Example 1 is that the firing conditions for the ball-milled primary pre-coated particle samples are different, specifically, they are fired at 1100°C for 1 hour.

[0120] Example 11

[0121] Method for manufacturing layered oxide cathode material:

[0122] The only difference between this example and Example 2 is that the firing conditions for the ball-milled secondary pre-coated particle samples are different, specifically, they are fired at 300°C for 22 hours.

[0123] Example 12

[0124] Method for manufacturing layered oxide cathode material:

[0125] The only difference between this example and Example 2 is that the firing conditions for the ball-milled secondary pre-coated particle samples are different, specifically, they are fired at 1100°C for 0.2h.

[0126] Comparative Example 1

[0127] Method for manufacturing layered oxide cathode material:

[0128] The only difference between this Comparative Example and Example 1 is the O3 phase cathode material NaNi 0.45 Mn 0.4 Ti 0.1 Cu 0.05 It means that O2 was used as the cathode material as is, without being coated in any way.

[0129] Scanning electron microscope image of the above O3 phase cathode material is shown in Fig. 2, and XRD test spectrum is shown in Fig. 4.

[0130] Comparative Example 2

[0131] Method for manufacturing layered oxide cathode material:

[0132] The only difference between this comparative example and Example 1 is that an inert coating layer was not coated, that is, the O3@P2 phase composite oxide particles having the obtained P2 phase metal oxide coating layer were used as the cathode material.

[0133] Comparative Example 3

[0134] Method for manufacturing layered oxide cathode material:

[0135] The only difference between this Comparative Example and Example 1 is that the P2 phase metal oxide coating layer was not coated, that is, 10 g of O3 phase cathode material particles NaNi 0.45 Mn 0.4 Ti 0.1 Cu 0.05 O2 and 0.2g of expanded graphite were placed directly into a ball milling tank to obtain pre-coated particles by ball milling for 3h and a rotation speed of 450rmp; the pre-coated particles were sufficiently dried and then polished to obtain an anode material.

[0136] Comparative Example 4

[0137] Method for manufacturing layered oxide cathode material:

[0138] The only difference between this Comparative Example and Example 1 is the O3 phase cathode material NaNi 0.45 Mn 0.4 Ti 0.1 Cu 0.05 After obtaining O2, 1g of a mixture of primary metal source and expanded graphite (weight ratio of the two is 1:1) and 20g of O3-phase cathode material NaNi 0.45 Mn 0.4 Ti 0.1 Cu 0.05 O2 was placed in a ball milling tank to obtain pre-coated particles with a ball milling time of 3h and a rotation speed of 450rmp; the pre-coated particle sample was placed in a muffle furnace to be fired at 900℃ for 10h, cooled, and then polished to obtain an anode material.

[0139] That is, a single-layer coating was performed by mixing the material of the P2 phase metal oxide coating layer and the material of the inert coating layer, and then using this as a mixed coating layer.

[0140] Battery Assembly:

[0141] (1) Preparation of anode plate: The layered oxide anode material, conductive carbon black, and polyvinylidene fluoride (PVDF) prepared in each of the above examples and comparative examples were mixed in a mass ratio of 8:1:1 and added to an appropriate amount of N-methylpyrrolidone (NMP) to form a uniform electrode slurry. Then, the electrode slurry was uniformly coated onto an aluminum foil and vacuum dried, then cut into a circular electrode plate with a diameter of 15 mm and transferred to a glove box to be prepared.

[0142] (2) Battery Assembly: Metallic sodium was used as the counter electrode and glass fiber was used as the separator. The solute of the electrolyte was sodium perchlorate, and the solvents of the electrolyte were propylene carbonate, ethylene carbonate, and fluoroethylene carbonate (volume ratio 1:1:0.05). The concentration of sodium perchlorate in the electrolyte was 1 mol / L. The battery was assembled into a CR2032 button cell, and the entire assembly process was performed in a glove box filled with argon. The button cell was left for 6 hours and then used for subsequent electrochemical performance tests.

[0143] B. Test Method

[0144] Coverage rate of P2 phase metal oxide coating layer and inert coating layer: The coating layer coverage area relative to the total surface area of ​​the electrode material was measured through infrared spectroscopy analysis.

[0145] Particle size: GB / T 19077 Particle size analysis laser diffraction.

[0146] Compressed density: GB / T 24533 Powder compressed density measurement.

[0147] pH Value: GB / T 9724 Principles of pH Measurement for Chemical Reagents.

[0148] Moisture content: GB / T 6283 Measurement of moisture content of chemical products Karl Fischer method (general method).

[0149] Specific surface area: GB / T 19587 Measurement of the specific surface area of ​​a solid material via the gas adsorption BET method.

[0150] Scanning electron microscope image: Taken with ZEISS MERLIN Compact, magnification 50k.

[0151] Electrochemical performance test: A charge-discharge test was performed at a current density of 0.1C using a constant current charge-discharge mode, with a charge cutoff voltage of 4.2V and a discharge cutoff voltage of 2.0V, and the first cycle charge-discharge capacity and Coulomb efficiency of each battery were tested.

[0152] Air stability: The cathode materials obtained in each of the above examples and comparative examples were exposed to an air environment and maintained for 24 hours, after which each cathode material exposed to air was manufactured into a battery according to the above method, and its first cycle charge / discharge capacity and Coulomb efficiency were tested.

[0153] The particle size distribution of the cathode material and the coating status of each layer obtained in each example and comparative example are shown in Table 1, the test results of the physicochemical performance are shown in Table 2, and the test results of the electrochemical performance of each battery manufactured further are shown in Table 3.

[0154] C. Analysis of test results for each example and comparative example

[0155] [Table 1]

[0156]

[0157] [Table 2]

[0158]

[0159]

[0160] [Table 3]

[0161]

[0162]

[0163] From the above results, it can be seen that the embodiments of the present invention described above achieve good coating effects, wherein the P2 phase metal oxide coating layer reduces the residual alkali content on the surface of the O3 phase nickel-manganese layered oxide, and the inert coating layer reduces side reactions occurring between the material surface, air, and electrolyte. Through the above experiments, it was found that a double-layer coating using a P2 phase metal oxide coating layer and an inert coating layer affects the particle size, specific surface area, pH value, moisture, and compression density of the material, and that the layered oxide cathode material exhibits high electrochemical performance and excellent air stability through appropriate nickel-manganese cathode material, coating amount, and ball milling conditions. Consequently, when the layered oxide cathode material is applied to a sodium-ion battery, the manufactured sodium-ion battery possesses high first-cycle Coulomb efficiency, excellent rate capability, long cycle life, and good air stability. Furthermore, the layered oxide cathode material according to the present invention has a simple and practical manufacturing method, is suitable for large-scale production, and has a wide range of application prospects.

[0164] It should be noted that the present application is not limited to the embodiments described above. The embodiments described above are merely examples, and all embodiments having substantially the same configuration as the technical concept and exhibiting the same operation and effect within the scope of the technical solution of the present application are also included within the technical scope of the present invention. Furthermore, various modifications to embodiments conceived by a person skilled in the art without departing from the essence of the present invention, as well as other embodiments configured by combining some components of the embodiments, are also included within the scope of the present invention.

Claims

Claim 1 A layered oxide cathode material comprises O3@P2 phase composite oxide particles and an inert coating layer coated on the surface of said O3@P2 phase composite oxide particles, wherein the O3@P2 phase composite oxide particles comprise O3 phase nickel-manganese-based oxide layered particles and a P2 phase metal oxide coating layer coated on the surface of said O3 phase nickel-manganese-based oxide layered particles; and the molecular formula of said O3 phase nickel-manganese-based 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 above P2 phase metal oxide coating layer is Na 0.6 Mg 0.15 Cu 0.15 Mn 0.7 A layered oxide cathode material characterized in that it is O2, and the inert coating layer is a carbon layer; wherein, in the 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; and 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 72% and the coverage rate of the inert coating layer on the surface of the O3@P2 phase composite oxide particles is 75%. Claim 2 A layered oxide cathode material according to claim 1, characterized in that, based on 100% of the weight of the layered oxide cathode material, the mass fraction of the P2 phase metal oxide coating layer is 0.5% to 5% and the mass fraction of the inert coating layer is 0.5% to 5%. Claim 3 A method for manufacturing a layered oxide cathode material according to claim 1, comprising the steps of: providing O3-phase nickel-manganese-based oxide layered particles and a primary metal source, mixing the O3-phase nickel-manganese-based oxide layered particles with the primary metal source, and then performing primary ball milling to obtain primary pre-coating particles; performing primary calcination treatment on the primary pre-coating particles to obtain O3@P2-phase composite oxide particles; mixing the O3@P2-phase composite oxide particles with a carbon source, and then performing secondary ball milling to obtain secondary pre-coating particles; and performing optional secondary calcination treatment on the secondary pre-coating particles to obtain the layered oxide cathode material. Claim 4 A method for manufacturing a layered oxide cathode material according to claim 3, wherein the rotational speed of the first ball milling is 100 rpm to 500 rpm and the time is 0.5 h to 4 h; and the rotational speed of the second ball milling is 100 rpm to 500 rpm and the time is 0.5 h to 4 h. Claim 5 A method for manufacturing a layered oxide cathode material according to claim 3, characterized in that the weight ratio of the O3 phase nickel-manganese-based oxide layered particles to the primary metal source is 1:(0.005~0.05), and the weight ratio of the O3@P2 phase composite oxide particles to the carbon source is 1:(0.005~0.05). Claim 6 A method for manufacturing a layered oxide cathode material according to claim 3, wherein the primary metal source comprises a sodium source and a coating metal source, and the coating metal source is one or more of oxides, hydroxides, carbonates, sulfates, oxalates, acetates, and citrates corresponding to Mg, Cu, and Mn; and the sodium source is one or more selected from sodium carbonate, sodium hydroxide, sodium nitrate, and sodium peroxide. Claim 7 A method for manufacturing a layered oxide cathode material according to claim 3, wherein the carbon source is one or more selected from coal tar, coal tar pitch, petroleum pitch, expanded graphite, carbon black, and graphene. Claim 8 A method for manufacturing a layered oxide cathode material according to claim 5, characterized in that the temperature of the first calcination treatment is 600℃ to 1000℃ and the calcination time is 2h to 20h, the temperature of the second calcination treatment is 400℃ to 1000℃ and the calcination time is 0.5h to 20h. Claim 9 A method for manufacturing a layered oxide cathode material according to claim 3, wherein the firing atmosphere of the first firing treatment is at least one of an air atmosphere and an oxygen atmosphere. Claim 10 A method for manufacturing a layered oxide cathode material according to claim 8, wherein, 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 tar pitch, and petroleum pitch, the secondary calcination treatment is performed, wherein the temperature of the secondary calcination treatment is 400℃ to 800℃, the time is 0.5h to 2h, and the atmosphere is one of a nitrogen atmosphere and an argon atmosphere; and when 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, the secondary calcination treatment is not performed, and the layered oxide cathode material is obtained immediately after the secondary ball milling. Claim 11 Anode plate characterized by comprising a layered oxide anode material according to claim 1 or 2. Claim 12 A sodium ion battery characterized by including a positive plate according to claim 11. Claim 13 delete Claim 14 delete

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