Sodium-ion layered metal oxide material, its manufacturing method, positive electrode material, and sodium-ion battery

Abstract

The present invention provides a sodium ion layered metal oxide material, a method for producing the same, a positive electrode material and a sodium ion battery, which belong to the technical field of sodium ion batteries. The sodium ion layered metal oxide material has a chemical formula shown in Formula I, where Formula I is Na x Ni a Mn b Ti (0.5-b) M (0.5-a) O (2-y) F y where 0.9≦x≦1.0, 0.3≦a<0.5, 0.3≦b≦0.4, 0.1≦1-ab≦0.35, 0≦y<0.1, and M includes at least one of Zn, Mg, Sn, Sb, Y, and Cu. By doping with the F element and the M element, Sodium ion layered metal oxide This contributes to improving the structural stability of the material, and the manufacturing method of the present invention reduces the formation of impurity phases. Sodium-ion layered metal oxide materials The distribution of the M element in the positive electrode sheet is more uniform, so that the positive electrode sheet and the sodium ion battery containing the sodium ion layered metal oxide material have a high discharge specific capacity and a high cycle performance.

Description

[Technical Field]

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to a sodium ion layered metal oxide material, a manufacturing method thereof, a positive electrode material, and a sodium ion battery. [Background technology]

[0002] The commercialization of electrochemical power sources, especially lithium-ion batteries (LIBs), has ushered in a new era of portable electronic products and electric vehicles, bringing great convenience to everyday life. However, concerns about the depletion of lithium resources and the driving forces behind price fluctuations for lithium, nickel, and cobalt raw materials have led to intensive research into sodium-ion batteries (NIBs), which are poised to become a strong contender in the energy storage field, including national grid and home energy storage. The cathode is an essential part of NIBs and directly determines all key performance characteristics of NIBs, such as cost, safety, energy density, power density, and cycle life. In addition, an ideal cathode material would be relatively environmentally friendly and easy to produce, transport, and store at scale.

[0003] Cost is a major factor driving the competition between sodium-ion batteries and lithium-ion batteries. Manganese has the advantages of being environmentally friendly, low in price, and high in annual production. Manganese-rich layered sodium-ion transition metal oxide materials (Mn-based Na x TMO2) contains many elements with electrochemical redox activity, such as Mn, Fe, Cu, Ni, Co, Cr, Ir, Ru, and O, and its chemical composition can be flexibly designed. It also has a high specific capacity and excellent safety performance, making it a strong competitor to commercially available sodium-ion battery cathode materials.

[0004] Currently, sodium ion layered transition metal oxide cathode materials have the general formula Na x TMO2 and Na +With the change in content, different structures are formed, and the general structures are O3, P3, O'3 and P2 phases. The transition metal sites in the layered oxides are occupied by various metal ions (e.g., Li, Na, Mg, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn, Ir, Ru, etc.). The outer core electron configurations, oxidation states, and TM-O bond energies of these metal ions are significantly different. + The layered oxide cathode materials with different structures are formed according to the content. Although O3-type high-nickel materials have high specific capacity, they not only undergo multi-phase transitions and large volume deformations when charged to high voltages, but also promote the decomposition of the electrolyte and induce co-doping of solvent molecules, ultimately causing serious structural degradation and capacity fading during the charge-discharge process of the electrode material. Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the problems in the background art, the present invention provides a sodium ion layered metal oxide material, a manufacturing method thereof, a positive electrode material and a sodium ion battery, which aim to solve the problems of serious structural degradation and capacity fade during charge and discharge of the positive electrode material. [Means for solving the problem]

[0006] In a first aspect, the present invention provides a sodium ion layered metal oxide material having the formula shown in Formula I: Na x Ni a Mn b Ti (0.5-b) M (0.5-a) O (2-y) F y Formula I, Here, 0.9≦x≦1.0, 0.3≦a<0.5, 0.3≦b≦0.4, 0.1≦1−ab≦0.35, 0≦y<0.1, and M includes at least one of Zn, Mg, Sn, Sb, Y, and Cu.

[0007] In the embodiment of the present invention, the element M contributes to improving the stability of the material, and F- The radius is O 2- Similar to the radius, substituting O with F is feasible. By controlling the doping amount of F, it is possible to avoid too many impurities in the finished product. The strong electronegativity of F can change the binding energy of oxygen element in the lattice, thereby increasing the Na + Improves the diffusion rate of Mn 3+ This suppresses lattice distortion caused by the Jahn-Teller effect of active ions such as ZnO, improving structural stability. Preferably, the sodium ion layered metal oxide material is an O3-type manganese-based layered oxide material.

[0008] In a second aspect, the present invention provides a method for producing the sodium-ion layered metal oxide material described above, said method comprising: A) mixing a Na source, a Ni source, a Mn source, a Ti source, a M source, and a F source with a solvent according to the stoichiometric ratio in Formula I, and then performing rough polishing to obtain a first slurry; B) polishing the first slurry to obtain a second slurry; C) spray drying the second slurry to obtain a first powder; D) calcining the powder to obtain a second powder by the following process: In an oxygen-containing atmosphere, the temperature is increased from room temperature to 110 to 130°C at a rate of 3 to 5°C / min, and the temperature is maintained for 2 to 4 hours. The temperature is then increased to 440 to 460°C at a rate of 5 to 8°C / min, and the temperature is maintained for 1 to 3 hours. The temperature is then increased to 850 to 950°C at a rate of 5 to 8°C / min, and the temperature is maintained for 10 to 20 hours. E) grinding and sieving the second powder to remove iron to obtain a sodium ion layered metal oxide material having a chemical formula of Formula I, Na x Ni a Mn b Ti (0.5-b) M (0.5-a) O (2-y) F y Formula I, wherein 0.9≦x≦1.0, 0.3≦a<0.5, 0.3≦b≦0.4, 0.1≦1−ab≦0.35, 0≦y<0.1, and M includes at least one of Zn, Mg, Sn, Sb, Y, and Cu.

[0009] In an embodiment of the present invention, the second powder is calcined at elevated temperatures using a specific process, which can reduce the occurrence of side reactions, reduce the formation of impurity phases, and make the copper distribution in the finished product more uniform, thereby improving the material uniformity and product stability, and further improving the electrochemical performance.

[0010] Preferably, the sodium ion layered metal oxide material is Na 0.95 Ni 0.45 Mn 0.3 Cu 0.05 Ti 0.2 O 1.95 F 0.05 , NaNi 0.48 Mn 0.4 Y 0.02 Ti 0.1 O 1.999 F 0.001 and Na 0.9 Ni 0.48 Mn 0.39 Cu 0.02 Mg 0.01 Ti 0.1 O2.

[0011] Preferably, the firing process is specifically as follows: In an oxygen-containing atmosphere, the temperature is increased from room temperature to 120-125°C at a rate of 4-5°C / min, and maintained at that temperature for 2-3 hours. The temperature is then increased further to 450-455°C at a rate of 5-7°C / min, and maintained at that temperature for 1-2 hours. The temperature is then increased further to 850-950°C at a rate of 5-8°C / min, and maintained at that temperature for 13-20 hours.

[0012] Preferably, the solvent used for rough grinding in step A) is water and / or alcohol, the solid content of the first slurry is 10 - 40%, ensuring the production volume and avoiding clogging of the rough grinder, sand mill and connecting pipes. The particle size of the first slurry is D100 < 10 μm, avoiding clogging of the filter screen of the sand mill by the particles in the slurry.

[0013] Preferably, the particle size of the second slurry is D50 < 3 μm and D100 < 8 μm, ensuring that the particle size distribution of the first powder obtained after spray drying is more concentrated, avoiding the generation of large particles, the slurry being uniform, and since the particle size of the second slurry is small and the insoluble particulate substances contact each other sufficiently, it is advantageous for ensuring the uniformity of the cation distribution in the finished product.

[0014] In the embodiments of the present invention, by polishing after rough grinding, it can be ensured that each insoluble particle in the slurry is sufficiently polished, ensuring the uniformity of the slurry and improving the polishing efficiency. Preferably, the particle size of the first powder is 2 μm < D50 < 15 μm, D100 < 40 μm, the moisture content is less than 1.5%, and BET > 15 m 2 / g

[0015] In the embodiments of the present invention, by the first powder meeting the above indexes, it can be ensured that there is less water vapor generated during the sintering of the first powder, avoiding the precipitation of sodium. The small particle size and large BET of the first powder ensure that the particles contact each other more sufficiently during sintering, facilitating ion exchange and migration, thereby ensuring that the sintered material has higher crystallinity, more uniform cation distribution, and fewer impurities.

[0016] Preferably, during the firing process, the oxygen content is 20 - 35%, the moisture content is less than 3%, and the carbon dioxide concentration is less than 1%.

[0017] In an embodiment of the present invention, the moisture, oxygen content and carbon dioxide content in the high-temperature furnace are detected online during the sintering process, and the gas flow rate, removal rate and oxygen gas and nitrogen gas ratio in the flowing gas are adjusted in a timely manner to control the moisture, oxygen content and carbon dioxide content in the high-temperature furnace within a control range, thereby avoiding the formation of too many impurity phases during the sintering process due to an excessively high oxygen content.

[0018] Preferably, after the firing is completed, rapid cooling is carried out to obtain the second powder, and the rapid cooling is a quenching treatment.

[0019] In the embodiment of the present invention, accelerating the cooling rate during the cooling process after firing allows for more Mn 3+ This contributes to the formation of a metastable phase containing 1,2-dichloro-1,3-trimethylsilyl group and having a high interlayer sodium content, thereby improving the reversible capacity of the electrode material.

[0020] In a third aspect, the present invention provides a positive electrode sheet comprising the sodium ion layered metal oxide material described above or the sodium ion layered metal oxide material produced by the production method described above.

[0021] In the embodiment of the present invention, the positive electrode sheet contains the above sodium ion layered metal oxide material, and therefore has good structural stability, high discharge specific capacity and high capacity retention rate.

[0022] In a fourth aspect, the present invention provides a sodium-ion battery comprising the positive electrode sheet described above. [Effects of the Invention]

[0023] In an embodiment of the present invention, a sodium ion battery includes the positive electrode sheet, and therefore has a high discharge specific capacity and high cycle performance. [Brief explanation of the drawings]

[0024] In order to more clearly describe the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only embodiments of the present invention, and those skilled in the art can obtain other drawings based on the provided drawings without making any creative efforts. [Figure 1] FIG. 1 is an SEM image of a sodium ion layered metal oxide material in Example 1 of the present invention. [Figure 2] FIG. 1 is an XRD diagram of a sodium ion layered metal oxide material in Example 1 of the present invention. [Figure 3] 1 shows the charge and discharge curves of the button battery in Example 1 of the present invention. [Figure 4] 3 shows the charge and discharge curves of the button battery in Example 2 of the present invention. [Figure 5] FIG. 2 is an SEM image of a sodium ion layered metal oxide material in Example 2 of the present invention. [Figure 6] 3 shows the charge and discharge curves of the button battery in Example 3 of the present invention. [Figure 7] FIG. 10 is an SEM image of a sodium ion layered metal oxide material in Example 3 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, the embodiments of the technical solution of the present application will be described in detail with reference to the drawings. The following embodiments are merely used to more clearly explain the technical solution of the present application, and therefore do not limit the protection scope of the present application, but are merely taken as examples.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art of this application, and the terms used herein are for the purpose of describing specific examples only and are not intended to be limiting of this application, and the terms "comprises" and "having" and any variations thereof in the specification and claims of this application and the description of the drawings above are intended to cover an exclusive inclusion.

[0027] In the description of the embodiments of the present application, the technical terms "first," "second," etc. are used only to distinguish between different objects, and cannot be understood as indicating or implying relative importance, or the number, particular order, or primary relationship of the indicated technical features. In the description of the embodiments of the present application, "plurality" means two or more, unless otherwise specified and specifically limited.

[0028] In this specification, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present application. The appearance of the term in each location in the description does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that excludes other embodiments. Those skilled in the art will clearly and implicitly understand that the embodiment described in this specification can be combined with other embodiments.

[0029] In the description of the embodiments of the present application, the term "and / or" indicates that there can be three types of relationships, not just a relationship describing related objects. For example, A and / or B can indicate three cases: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in this specification, the character " / " generally indicates that the related objects before and after it are in an "or" relationship.

[0030] In describing the embodiments of the present application, the term "plurality" means two or more (including two); similarly, "multiple sets" means two or more sets (including two sets), and "multiple sheets" means two or more (including two sheets).

[0031] In describing the embodiments of the present application, the orientations or positional relationships indicated by technical terms such as "center," "longitudinal," "lateral," "length," "width," "thickness," "up," "down," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" are based on the orientations or positional relationships shown in the drawings, and are intended merely to explain and simplify the description of the embodiments of the present application. They do not indicate or imply that the indicated devices or elements must have a specific orientation or be configured and operated in a specific orientation, and therefore cannot be understood as limiting the embodiments of the present application.

[0032] In describing the embodiments of the present application, unless otherwise clearly specified or limited, the technical terms "attached," "coupled," "connected," "fixed," etc. should be understood in a broad sense, and may refer to, for example, a fixed connection, a detachable connection, or an integral connection, a mechanical connection, an electrical connection, a direct connection, an indirect connection via an intermediate medium, internal communication between two elements, or an interactive relationship between two elements. Those skilled in the art will be able to understand the specific meanings of the above terms in the embodiments of the present application according to specific circumstances.

[0033] Currently, in the structure of sodium ion layered transition metal oxide cathode materials, O3-type high-nickel materials have a high specific capacity, but when they are charged to a high voltage, they not only undergo multi-phase transitions, resulting in large volume deformation, but also promote the decomposition of the electrolyte and induce co-doping of solvent molecules, ultimately causing serious structural degradation and capacity fading during the charge and discharge process of the electrode material.

[0034] To solve the above problems, the present invention provides a sodium ion layered metal oxide material, its manufacturing method, a positive electrode sheet and a sodium ion battery, in which doping with F element and M element contributes to improving the stability of the material, and the strong electronegativity of F can change the binding energy of oxygen element in the lattice, thereby increasing the Na + Improves the diffusion rate of Mn 3+This suppresses lattice distortion due to the Jahn-Teller effect of active ions such as sodium ion, improving structural stability. Furthermore, the present invention employs a specific process for calcining the second powder at elevated temperatures, thereby reducing the occurrence of side reactions, reducing the formation of impurity phases, and achieving a more uniform copper distribution in the finished product, thereby improving material uniformity, product stability, and electrochemical performance. As a result, positive electrode sheets and sodium ion batteries using this sodium ion layered metal oxide material have high discharge specific capacity and high cycle performance.

[0035] In a first aspect, the present invention provides a sodium-ion layered metal oxide material, which is an O3-type manganese-based layered oxide material and has the chemical formula shown in Formula I: Na x Ni a Mn b Ti (0.5-b) M (0.5-a) O (2-y) F y Formula I, Here, 0.9≦x≦1.0, 0.3≦a<0.5, 0.3≦b≦0.4, 0.1≦1−ab≦0.35, 0≦y<0.1, and M includes at least one of Zn, Mg, Sn, Sb, Y, and Cu.

[0036] In one embodiment of the present invention, 0.9≦x≦1.0, preferably 0.92≦x≦0.98, for example, x is 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, or 1.0, and preferably a range value with any of the above numerical values ​​as the upper or lower limit.

[0037] In one embodiment of the present invention, 0.3≦a<0.5, preferably 0.35≦a≦0.45, for example, a is 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, or 0.49, and preferably a range having any of the above numerical values ​​as its upper or lower limit.

[0038] In one embodiment of the present invention, 0<(0.5-a)≦0.2, preferably 0.01≦(0.5-a)≦0.05. Within this range, the proportion of M element can be prevented from being too high. Since M element has poor compatibility with oxides of elements such as Ni, Mn, and Ti during the sintering process, the amount of impurity phases in the finished product will increase, and the energy density of the material will be too low.

[0039] In one embodiment of the present invention, 0.3≦b≦0.4, preferably 0.32≦b≦0.38, for example, b is 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, or 0.4, and preferably a range value with any of the above numerical values ​​as the upper or lower limit.

[0040] In one embodiment of the present invention, 0.1≦1−ab≦0.35, preferably 0.2≦1−ab≦0.3.

[0041] In one embodiment of the present invention, 0≦y<0.1, preferably 0.01≦y≦0.08, for example, y is 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, or 0.09, preferably a range value with any of the above values ​​as the upper or lower limit. When the value of y is within the above range, it is possible to avoid a situation in which the proportion of F element is too high, resulting in an increase in impurity phases (e.g., nickel oxide) in the finished product, resulting in an excessively low energy density and poor structural stability of the material.

[0042] Specifically, in an embodiment of the present invention, the sodium ion layered metal oxide material is Na 0.95 Ni 0.45 Mn 0.3 Cu 0.05 Ti 0.2 O 1.95 F 0.05 , NaNi 0.48 Mn 0.4 Y 0.02 Ti 0.1 O1.999 F 0.001 and Na 0.9 Ni 0.48 Mn 0.39 Cu 0.02 Mg 0.01 Ti 0.1 O2.

[0043] In the present invention, after doping with F and M elements, the capacity retention rate of the material after 100 cycles of 1C is improved by 10% to 15%.

[0044] In a second aspect, the present invention further provides a method for producing a sodium ion layered metal oxide material, said method comprising: A) mixing a Na source, a Ni source, a Mn source, a Ti source, a M source, and a F source with a solvent according to the stoichiometric ratio in Formula I, and then performing rough polishing to obtain a first slurry; B) polishing the first slurry to obtain a second slurry; C) spray drying the second slurry to obtain a first powder; D) calcining the powder to obtain a second powder by the following process: In an oxygen-containing atmosphere, the temperature is increased from room temperature to 110 to 130°C at a rate of 3 to 5°C / min, and the temperature is maintained for 2 to 4 hours. The temperature is then increased to 440 to 460°C at a rate of 5 to 8°C / min, and the temperature is maintained for 1 to 3 hours. The temperature is then increased to 850 to 950°C at a rate of 5 to 8°C / min, and the temperature is maintained for 10 to 20 hours. E) grinding and sieving the second powder to remove iron to obtain a sodium ion layered metal oxide material having the formula of Formula I: Na x Ni a Mn b Ti (0.5-b) M (0.5-a) O (2-y) F y Formula I

[0045] In one embodiment of the present invention, the Na source is preferably one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium acetate, sodium oxalate, and sodium citrate, the Ni source is preferably one or more of nickel monoxide (NiO), nickel oxide (Ni2O3), nickel hydroxide "Ni(OH)2", nickel hydroxide "Ni(OH)3", nickel carbonate, and nickel oxalate, and the Mn source is preferably trimer tetroxide. The Ti source is preferably one or more of manganese dioxide, manganese trioxide, manganese monoxide, manganese carbonate, and manganese oxalate, and the Ti source is preferably titanium dioxide and / or metatitanic acid (HTiO), the M source is preferably at least one of oxide of M, hydroxide of M, carbonate of M, oxalate of M, and citrate of M, and when the M element is yttrium (Y), the M source is preferably oxide of Y, and the F source is preferably sodium fluoride. In the present invention, the Na source, Ni source, Mn source, Ti source, M source, and F source are all weighed and mixed according to the moles of the metal elements in the chemical formula shown in Formula I, which is a common technical means in this field, and therefore a description of the present invention will be omitted here.

[0046] In one embodiment of the present invention, the solvent used for rough polishing is preferably water and / or alcohol, more preferably deionized water and / or alcohol, the time for the rough polishing is preferably 1 to 3 hours, more preferably 1 to 2 hours, and the operating frequency of the rough polishing is preferably 10 to 50 Hz, more preferably 20 to 40 Hz.

[0047] In one embodiment of the present invention, the solid content of the first slurry obtained after rough polishing is preferably 10 to 40%, more preferably 20 to 30%, for example, 10%, 15%, 20%, 25%, 30%, 35%, or 40%, preferably within a range with any of the above numerical values ​​as the upper or lower limit, and the particle size of the first slurry is preferably D100<10 μm, more preferably D100<5 μm. After obtaining the first slurry, the present invention circulates and polishes the first slurry in a sand mill by switching the tanks in the A / B tank circulation method to obtain a second slurry.

[0048] In one embodiment of the present invention, the polishing time is preferably 2 to 5 hours, more preferably 3 to 4 hours. The rotation speed of the sand mill is preferably 200 to 1500 r / min, more preferably 500 to 1000 r / min. The particle size of the second slurry is D50 < 3 μm and D100 < 8 μm, preferably D50 < 2 μm and D100 < 5 μm. After obtaining the second slurry, the present invention spray-dries the second slurry to obtain a first powder. <00,00330

[0049] <| In one embodiment of the present invention, the particle size of the first powder obtained by spray drying is preferably 2 μm < D50 < 15 μm and D100 < 40 μm, the moisture content is less than 1.5%, and BET > 15 m 2 / g, more preferably 5 μm < D50 < 12 μm and D100 < 30 μm, the moisture content is less than 1.0%, and BET > 15 m 2 / g. <|

[0050] After obtaining the first powder, the present invention sinters it. The sintering is preferably performed by the following process. In an oxygen-containing atmosphere, the temperature is raised from room temperature to 110 - 130 °C at a heating rate of 3 - 5 °C / min, held for 2 - 4 hours, then the temperature is raised to 440 - 46 °C at a heating rate of 5 - 8 °C / min, held for 1 - 3 hours, and further the temperature is raised to 890 - 910 °C at a heating rate of 5 - 8 °C / min, and held for 10 - 20 hours.

[0051] In one embodiment of the present invention, the oxygen-containing atmosphere is preferably dry oxygen gas, dry air, or a mixture of dry oxygen gas and nitrogen gas, thereby preventing the material from being exposed to water and carbon dioxide during the cooling process and from being altered. Preferably, the oxygen-containing atmosphere is a mixture of dry oxygen gas and nitrogen gas, with the volume fraction of oxygen gas being preferably 25-35%, more preferably 30%, to control the oxygen gas content in the high-temperature furnace and prevent the adverse effects of water and carbon dioxide in the gas on the finished product. This contributes to reducing the free sodium content and pH of the finished product, preventing the slurry from gelling during battery manufacturing due to excessively high free sodium content and pH.

[0052] In one embodiment of the present invention, the first step involves heating from room temperature to 110-130°C at a heating rate of 3-5°C / min and then maintaining the temperature for 2-4 hours. The purpose of this step is mainly to reduce the moisture content of the first powder, thereby avoiding excessive moisture content in the high-temperature furnace atmosphere during the subsequent rapid heating process, which could lead to side reactions and excessively high impurity content in the finished product.

[0053] In this stage, the temperature increase rate is preferably 3 to 5°C / min, more preferably 3 to 4°C / min, the firing temperature is preferably 110 to 130°C, more preferably 115 to 125°C, for example, 110°C, 115°C, 120°C, 125°C, or 130°C, preferably within a range with any of the above numerical values ​​as the upper or lower limit, and the warming time is preferably 2 to 4 hours, more preferably 2 to 3 hours.

[0054] After the first firing stage is complete, the temperature is increased to 440-460°C at a rate of 5-8°C / min and maintained at this temperature for 1-3 hours, followed by the second firing stage. This stage is primarily intended to promote the decomposition and melting of the M element compound, improve the compatibility of M element with other elements, and ensure a more uniform distribution of M element in the finished product, improving material uniformity and ensuring product stability. Otherwise, the uneven distribution of M element in the finished product will result in inconsistent electrical performance in sampling tests at different points in the finished product, leading to poor product stability, or poor compatibility of M element with other elements and a high level of M element oxide impurities in the finished product, resulting in poor electrical performance.

[0055] In one embodiment of the present invention, the temperature rise rate in the second sintering step is preferably 5 to 8°C / min, more preferably 6 to 7°C / min, the firing temperature is preferably 440 to 460°C, more preferably 445 to 455°C, for example, 440°C, 445°C, 450°C, 455°C, or 460°C, preferably within a range with any of the above numerical values ​​as the upper or lower limit, and the temperature retention time is preferably 1 to 3 hours, more preferably 1 to 2 hours.

[0056] After the second firing step is completed, the present invention increases the temperature to 890-910°C at a rate of 5-8°C / min and maintains the temperature for 10-20 hours to carry out the third firing step. Firing at this temperature and time is advantageous in avoiding the formation of too many impurity phases during the sintering process due to temperatures that are too high or too low, and contributes to improving the crystallinity and purity of the finished product, thereby improving the charge / discharge specific capacity.

[0057] In one embodiment of the present invention, the temperature rise rate is preferably 5 to 8°C / min, and more preferably 6 to 7°C / min, the firing temperature is preferably 850 to 950°C, and more preferably 860 to 940°C, for example, 850°C, 860°C, 870°C, 880°C, 890°C, 900°C, 910°C, 920°C, 930°C, 940°C, or 950°C, and is preferably within a range with any of the above numerical values ​​as the upper or lower limit, and the temperature retention time is preferably 10 to 20 hours, and more preferably 15 to 16 hours.

[0058] During the entire sintering process, the water content in the high-temperature furnace is controlled to be less than 3%, the carbon dioxide concentration is less than 1%, and the oxygen content is controlled to be 20% to 50%, to avoid the formation of too many impurity phases during the sintering process due to the oxygen content being too high.The moisture, oxygen, and carbon dioxide contents in the high-temperature furnace are detected online during the sintering process, and the gas flow rate, removal rate, and the oxygen and nitrogen gas ratio in the flowing gas are promptly adjusted to keep the moisture, oxygen, and carbon dioxide contents in the high-temperature furnace within the control range.

[0059] After the firing is completed, the product is cooled to room temperature to obtain the second powder. Although natural cooling is possible, the present invention preferably involves rapidly cooling the fired product to room temperature, for example, by quenching, which accelerates the cooling rate and allows more Mn to be added. 3+ This contributes to the formation of a metastable phase containing Cr and having a high content of interlayer sodium, thereby improving the reversible capacity of the electrode material. In the present invention, the quenching treatment preferably employs cooling with chilled water or liquid nitrogen.

[0060] After obtaining the second powder, the present invention pulverizes it, sieves it to remove iron, and obtains a sodium-ion layered metal oxide material. The environmental humidity during pulverization and sieving is controlled to be less than 15%. The obtained sodium-ion layered metal oxide material has a particle size range of 0.5 μm < D50 < 12 μm, D100 < 40 μm, the content of magnetic foreign substances is less than 150 ppm, the manganese elution is less than 0.5 ppm, the free sodium is less than 100 ppm, and the moisture is less than 1000 ppm.

[0061] In one embodiment of the present invention, the pulverization method is preferably a jet mill or a mechanical mill. When sieving, the material passes through at least two stages of sieves. The mesh number of the first-stage sieve is preferably 80 - 100 meshes, and the mesh number of the second-stage sieve is 120 - 320 meshes.

[0062] Pulverization and sieving can improve the uniformity of the finished product, avoid large particles in the finished product from having an adverse effect on electrical performance, control the environmental humidity during pulverization and sieving to be less than 15%, and avoid material deterioration, impurity generation, and reduction of electrical performance due to water absorption of the sample.

[0063] In one embodiment of the present invention, the processes of pulverization, sieving, and iron removal of the second powder are continuous operations, connected through pipes in the middle, transported using negative pressure. After the finished product is degassed, it enters the pulverization equipment, and dry nitrogen gas is passed through both the sieving and iron removal processes for protection, avoiding the material from contacting water and carbon dioxide and generating impurities.

[0064] In a third aspect, the present invention provides a positive electrode sheet containing the above-mentioned sodium-ion layered metal oxide material. The present invention does not particularly limit other materials used in the positive electrode sheet, such as current collectors, conductive agents, adhesives, etc. General manufacturing raw materials of positive electrode sheets commonly used in this field can be adopted.

[0065] In a third aspect, the present invention provides a sodium ion battery including the above-described positive electrode sheet. The present invention does not particularly limit other materials used in the sodium ion battery, such as a negative electrode and a separator, and general manufacturing raw materials for sodium ion batteries commonly used in this field may be used.

[0066] Although several specific examples are provided below, the examples described below are merely illustrative and are used to explain the present application and should not be construed as limiting the present application. In the examples, specific techniques or conditions are not specified, and are carried out in accordance with the techniques or conditions described in literature in this field or in accordance with the product instructions. Reagents or instruments used without a manufacturer's name are all common products available on the market.

[0067] Example 1 The chemical formula of sodium ion layered metal oxide material is Na 0.95 Ni 0.45 Mn 0.3 Cu 0.05 Ti 0.2 O 1.95 F 0.05 and According to the weighing ratio of the number of moles of metal elements in the chemical formula of the material, sodium carbonate, nickel oxide, trimanganese tetroxide, titanium oxide, copper oxide, sodium fluoride and deionized water are put into a coarse grinding machine and mixed uniformly. The material mixing time is 2 hours and the operating frequency is 30 Hz. A first slurry (solid content is 25% and particle size is D100<8.5 μm) is obtained. The first slurry was ground and mixed in a sand mill by switching tanks in an A / B tank circulation manner, the grinding time was 3 hours, and the sand mill rotation speed was 1000 r / min to obtain a second slurry (particle size D50<3 μm, D100<8 μm). The second slurry was spray-dried to obtain the first powder (particle size: D50<10 μm, D100<35 μm, moisture: 0.5%, BET: 30 μm). 2 / g) The first powder is placed in a high-temperature furnace and fired, with the firing temperature curve being: from room temperature, the temperature is increased at 5°C / min to 120°C, and the temperature is maintained for 2 hours; then the temperature is increased at 5°C / min to 450°C, and the temperature is maintained for 2 hours; then the temperature is increased at 5°C / min to 900°C, and the temperature is maintained for 13 hours. The atmosphere in the high-temperature furnace is a mixed gas of dry oxygen gas and nitrogen gas (of which the oxygen gas ratio is 25%). Then, the fired powder is rapidly cooled to room temperature with chilled water to obtain a second powder. During the sintering process, the 2-hour hold at 120°C is primarily intended to reduce the moisture content of the first powder, preventing excessive moisture in the high-temperature furnace atmosphere during the subsequent rapid heating process, which could result in side reactions and excessive impurities in the finished product. The 2-hour hold at 450°C is primarily intended to promote the decomposition and melting of copper oxide, improve the compatibility of copper with other elements, ensure a more uniform copper distribution in the finished product, improve material uniformity, and ensure product stability. Otherwise, uneven copper distribution in the finished product could result in inconsistent electrical performance in sampling tests at different points in the finished product, leading to poor product stability. Alternatively, poor compatibility of copper with other elements could result in high copper oxide impurities in the finished product, resulting in poor electrical performance.

[0068] During the sintering process, the water content in the high-temperature furnace was controlled to be less than 3%, the carbon dioxide concentration to be less than 1%, and the oxygen content to be 20%-35%.

[0069] The second powder is pulverized, sieved and iron is removed to obtain a sodium ion layered metal oxide material, and the ambient humidity during pulverization and sieving is controlled to be less than 15%. The obtained sodium ion layered metal oxide material has a particle size range of D50 of 8.5 μm, D100 of 36 μm, a content of magnetic foreign matter of less than 150 ppm, manganese elution of less than 0.5 ppm, free sodium of less than 100 ppm, and moisture of less than 1000 ppm. The SEM image of the sodium ion layered metal oxide material is shown in Figure 1. The sodium ion layered metal oxide exhibits a typical layered structure, with small particles agglomerating to form large particles, and the primary particle size was 0.7 to 7 μm.

[0070] The XRD of the sodium ion layered metal oxide material is shown in Figure 2. Button batteries were fabricated using sodium-ion layered metal oxide materials as cathodes. The charge-discharge curves between 2 and 4.0 V are shown in Figure 3. The 0.1 C discharge specific capacity was 138 mAh / g, and the capacity retention at 1 C for 100 cycles was approximately 80% before doping with Cu and F. After doping with F and Cu, the 0.1 C discharge specific capacity remained almost unchanged compared to the undoped material, but the capacity retention at 1 C for 100 cycles was 91.2%, an approximately 11% improvement. Compared to the material doped with Cu alone, the capacity retention at 1 C for 100 cycles was 85.3%, an approximately 5% improvement. The introduction of M also improved the environmental stability of the layered metal oxide. After doping with M, the discharge specific capacity of the material increased by 5% to 10% compared to the undoped material when left in the same air atmosphere for the same time.

[0071] (Comparative Example 1) The sodium ion layered metal oxide material was prepared by the method of Example 1 and assembled into a button battery. The sodium ion layered metal oxide material had the chemical formula Na 0.95 Ni 0.5 Mn 0.3 Ti 0.2 There was something different about being O2. A button battery was manufactured using the method described in Example 1 and subjected to electrochemical performance testing. The results showed that the discharge specific capacity at 0.1C was 135.5mAh / g, and the capacity retention rate of the material at 1C for 100 cycles was approximately 80%.

[0072] (Comparative Example 2) The sodium ion layered metal oxide material was prepared by the method of Example 1 and assembled into a button battery. The sodium ion layered metal oxide material had the chemical formula Na 0.95Ni 0.45 Mn 0.3 Cu 0.05 Ti 0.2 There was something different about being O2. A button battery was manufactured using the method described in Example 1 and subjected to electrochemical performance testing. The results showed that the discharge specific capacity at 0.1C was 137mAh / g, and the capacity retention rate of the material at 1C for 100 cycles was approximately 85.3%.

[0073] (Comparative Example 3) The sodium ion layered metal oxide material was prepared by the method of Example 1 and assembled into a button battery. The sodium ion layered metal oxide material had the chemical formula Na 0.95 Ni 0.5 Mn 0.3 Ti 0.2 O 1.95 F 0.05 There was a difference in that. A button battery was manufactured using the method described in Example 1 and subjected to electrochemical performance testing. The results showed that the discharge specific capacity at 0.1C was 136mAh / g, and the capacity retention rate of the material at 1C for 100 cycles was approximately 82.4%.

[0074] Comparative Example 4 A button battery was fabricated using the sodium ion layered metal oxide material according to the method of Example 1, but the difference was that the first heating step was omitted, and the temperature was directly raised to 450°C at 5°C / min, kept at that temperature for 3 hours, and then raised to 900°C at 5°C / min, and kept at that temperature for 13 hours. A button battery was manufactured using the method of Example 1 and subjected to an electrochemical performance test. The result showed that the discharge specific capacity in the 2 to 4.0 V charge / discharge range was 125 mAh / g.

[0075] (Comparative Example 5) A button battery was fabricated using a sodium ion layered metal oxide material according to the method of Example 1, but the difference was that the first stage of the temperature rise process was omitted, and the temperature was directly raised to 900°C at 5°C / min and maintained at that temperature for 13 hours. The discharge specific capacity in the 2 to 4.0V charge / discharge range was 121mAh / g.

[0076] (Example 2) The chemical formula of the sodium-ion layered metal oxide material is NaNi 0.48 Mn 0.4 Y 0.02 Ti 0.1 O 1.999 F 0.001 and Based on the stoichiometric ratio of the number of moles of metal elements in the chemical formula of the material, sodium bicarbonate, nickel oxide, manganese tetroxide, titanium oxide, sodium fluoride, yttrium oxide and a certain amount of deionized water are put into a rough grinder and mixed uniformly. The material mixing time is 2 h, the operating frequency is 30 Hz, and the first slurry (the solid content is 30%, and the particle size is D100 < 7 μm) is obtained. The first slurry is polished and mixed in a sand mill by switching the tank in the A / B tank circulation method. The polishing time is 3 h, the sand mill rotation speed is 1000 r / min, and the second slurry (the particle size is D50 < 2 μm, D100 < 7 μm) is obtained. The second slurry is spray-dried to obtain the first powder (the particle size is 3 μm < D50 < 10 μm, D100 < 30 μm, the moisture content is less than 1%, and the BET is 30 m 2 / g). The first powder is placed in a high-temperature furnace for firing. The firing temperature curve rises from room temperature to 120 °C at 4 °C / min, holds for 2 h, then rises to 455 °C at 6 °C / min, holds for 2 h, and further rises to 850 °C at 7 °C / min and holds for 20 h. Subsequently, the fired material is rapidly cooled. The rapid cooling method may be cooling by liquid nitrogen or cooling by chilled water. In this sintering process, maintaining a temperature of 120°C for 2 hours mainly aims to reduce the water content of the first powder. This is to avoid having too much moisture in the high-temperature furnace atmosphere during the subsequent rapid temperature increase process, which may cause side reactions and result in a too high impurity phase in the finished product. When the maximum sintering temperature is 850°C, the compatibility between Y and other elements can be improved, making the distribution of Y elements in the finished product more uniform, enhancing the material uniformity, and ensuring the stability of the product. Otherwise, due to the non-uniform distribution of Y elements in the finished product, the electrical performances of sampling tests at different points in the finished product will not match, ultimately leading to poor product consistency. Additionally, when the sintering temperature is 850°C, it is possible to avoid the primary particles of the finished product being too large and causing a decrease in electrical performance.

[0077] In this sintering process, the water content in the high-temperature furnace was controlled to be less than 2%, the carbon dioxide concentration was less than 1%, and the oxygen content was 20% - 50%.

[0078] The second powder was pulverized, sieved, and iron was removed to obtain a sodium-ion layered metal oxide material. The environmental humidity during pulverization and sieving was controlled to be less than 10%. The obtained sodium-ion layered metal oxide material had a particle size range of 2μm < D50 < 10μm and 25μm < D100 < 35μm, the content of magnetic foreign substances was less than 150ppm, the manganese elution was less than 0.5ppm, the free sodium was less than 100ppm, and the moisture was less than 1000ppm.

[0079] The SEM of the sodium-ion layered metal oxide material is as shown in Figure 5. The sodium-ion layered metal oxide exhibits a typical layered structure, with small particles aggregating to form large particles, and the primary particle size was 0.2 - 4.5μm.

[0080] Using the sodium-ion layered metal oxide material as the positive electrode, a button battery was manufactured. The charge-discharge curve within the range of 2 - 4.0V is as shown in Figure 4. The discharge specific capacity at 0.1C was 135mAh / g, and the capacity retention rate after 100 cycles at 1C was approximately 85.2%. Before doping with Y and F (NaNi 0.5 Mn0.4 Ti 0.1 The capacity retention rate of 1C for 100 cycles of the (Ti 0.1 O2) material was about 80%, and the discharge specific capacity at 0.1C was 135.5 mAh / g. After doping with Y and F elements, compared with the undoped case, the discharge specific capacity at 0.1C decreased slightly, but the capacity retention rate of 1C for 100 cycles of the material increased by about 5%. After doping with Y, the layered metal oxide material had strong Y-O bonds, formed a stable structure, and the material was surrounded by a Y2O3 protective layer. The expanded Na layer caused Na ions to be inserted not only on the surface but also into the bulk. Therefore, the recycling performance of the material improved after Y doping. In addition, yttrium oxide does not decompose or melt at 850°C, corresponding to the introduction of a small amount of impurity phase, but in this product, the addition amount of yttrium oxide was small and did not have an adverse effect on the electrical performance.

[0081] (Example 3) The chemical formula of the sodium ion layered metal oxide material is Na 0.9 Ni 0.48 Mn 0.39 Cu 0.02 Mg 0.01 Ti 0.1 O2, and Based on the stoichiometric ratio of the number of moles of metal elements in the chemical formula of the material, sodium carbonate, nickel hydroxide, manganese dioxide, titanium oxide, and alcohol were put into a rough grinder and uniformly mixed. The material mixing time was 2 h, the operating frequency was 30 Hz, and the first slurry (solid content was 20%, particle size was D100 < 10 μm) was obtained. The first slurry was polished and mixed in a sand mill by switching the tank in an A / B tank circulation method. The polishing time was 3 h, the sand mill rotation speed was 1000 r / min, and the second slurry (particle size was D50 < 3 μm, D100 < 10 μm) was obtained. The second slurry was spray-dried to obtain the first powder (particle size was 3 μm < D50 < 8 μm, D100 < 35 μm, moisture was less than 1%, and BET was 30 m 2 / g). Place the first powder in a high-temperature furnace for firing. The firing temperature curve rises from room temperature to 120°C at a rate of 4°C / min, holds for 3 hours, then rises to 450°C at a rate of 7°C / min, holds for 1 hour, then rises to 950°C at a rate of 8°C / min, and holds for 15 hours. The atmosphere in the high-temperature furnace is dry oxygen gas. Subsequently, rapidly cool it to room temperature to obtain the second powder. The rapid cooling method may be cooling with liquid nitrogen or cooling with chilled water. During this sintering process, holding at 120°C for 3 hours is mainly to reduce the water content of the first powder and avoid the situation that the water content in the high-temperature furnace atmosphere is too high during the subsequent rapid heating process, resulting in side reactions and too high impurity phases in the finished product. Holding at 450°C for 1 hour is mainly to promote the decomposition and melting of copper oxide, improve the compatibility between copper and other elements, make the distribution of copper in the finished product more uniform, improve the material uniformity, and ensure the stability of the product. Otherwise, the non-uniform distribution of copper elements in the finished product will cause the electrical performance of sampling tests at different points in the finished product to not match and the stability of the product to be low, or the poor compatibility between copper elements and other elements and the high impurity of copper oxide in the finished product will cause poor electrical performance.

[0082] During this sintering process, control the water content in the high-temperature furnace to be less than 2% and the carbon dioxide concentration to be less than 1%. Detect the water content and carbon dioxide content in the high-temperature furnace online during the sintering process, timely adjust the gas flow rate and discharge amount, and control the water content and carbon dioxide content in the high-temperature furnace within the control range.

[0083] Crush, sieve, and remove iron from the second powder to obtain a sodium ion layered metal oxide material. Control the environmental humidity during crushing and sieving to be less than 10%. The obtained sodium ion layered metal oxide material has a particle size range of 3μm < D50 < 10μm and 25μm < D100 < 40μm, the content of magnetic foreign matter is less than 150ppm, the manganese elution is less than 0.5ppm, the free sodium is less than 100ppm, and the water content is less than 1000ppm.

[0084] The SEM image of the sodium ion layered metal oxide material is shown in Figure 7. The sodium ion layered metal oxide exhibits a typical layered structure, with small particles agglomerating to form large particles, and the primary particle size was 0.5 to 5 μm.

[0085] The chemical formula is Na 0.9 Ni 0.48 Mn 0.39 Cu 0.02 Mg 0.01 Ti 0.1 The sodium ion layered metal oxide material of O2 was used as the cathode to fabricate a button battery. The charge-discharge curve in the 2-4.0 V range is shown in Figure 6. The discharge specific capacity at 0.1 C was 129 mAh / g, and the capacity retention rate at 1 C for 100 cycles was about 92.1%. 0.9 Ni 0.5 Mn 0.4 Ti 0.1 The 100-cycle capacity retention rate of the O2 material at 1C was approximately 80%, and the 0.1C discharge specific capacity was 135.5 mAh / g. After doping with Cu and Mg, the 0.1C discharge specific capacity decreased slightly compared to the undoped material, but the 100-cycle capacity retention rate of the material at 1C was improved by approximately 12%. The addition of Mg to Cu doping is equivalent to substituting divalent magnesium ions for trivalent manganese ions, which increases the interlayer distance, promoting sodium ion diffusion and alleviating the lattice distortion caused by the desorption of sodium ions, improving the stability of the layered structure. Furthermore, the doping of divalent magnesium ions can alleviate structural deformation or volumetric changes that occur during the charge-discharge cycle of sodium-ion batteries, suppressing irreversible phase changes and significantly improving the reversible specific capacity of the material. In addition, Mg is non-electrochemically active in the material and does not participate in the redox reaction. However, the amount of magnesium oxide added in this product is so small that it does not adversely affect the electrical performance.

[0086] The above are only preferred embodiments of the present invention, and it should be pointed out that those skilled in the art can make some improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be regarded as within the protection scope of the present invention.

Claims

1. A sodium ion layered metal oxide material, wherein the sodium ion layered metal oxide material is an O3-type manganese-based layered oxide material, and the sodium ion layered metal oxide material is Na ０．９５ Ni ０．４５ Mn ０．３ Cu ０．０５ Ti ０．２ O １．９５ F ０．０５ , NaNi ０．４８ Mn ０．４ Y ０．０２ Ti ０．１ O １．９９９ F ０．００１ and Na ０．９ Ni ０．４８ Mn ０．３９ Cu ０．０２ Mg ０．０１ Ti ０．１ O ２ One or more of the following: The method for producing the sodium ion layered metal oxide material comprises: A) mixing a Na source, a Ni source, a Mn source, a Ti source, a M source, and a F source with a solvent according to the stoichiometric ratio in Formula I, and then performing rough polishing to obtain a first slurry; B) polishing the first slurry to obtain a second slurry; C) spray drying the second slurry to obtain a first powder; D) calcining the powder to obtain a second powder by the following process: In an oxygen-containing atmosphere, the temperature is increased from room temperature to 110-130°C at a rate of 3-5°C / min, and the temperature is maintained for 2-4 hours. The temperature is then increased to 440-460°C at a rate of 5-8°C / min, and the temperature is maintained for 1-3 hours. The temperature is then increased to 850-950°C at a rate of 5-8°C / min, and the temperature is maintained for 10-20 hours. E) grinding and sieving the second powder to remove iron to obtain a sodium-ion layered metal oxide material having the formula of Formula I:

2. A) mixing a Na source, a Ni source, a Mn source, a Ti source, a M source, and a F source with a solvent according to the stoichiometric ratio in Formula I, and then performing rough polishing to obtain a first slurry; B) polishing the first slurry to obtain a second slurry; C) spray drying the second slurry to obtain a first powder; D) calcining the powder to obtain a second powder by the following process: In an oxygen-containing atmosphere, the temperature is increased from room temperature to 110-130°C at a rate of 3-5°C / min, and the temperature is maintained for 2-4 hours. The temperature is then increased to 440-460°C at a rate of 5-8°C / min, and the temperature is maintained for 1-3 hours. The temperature is then increased to 850-950°C at a rate of 5-8°C / min, and the temperature is maintained for 10-20 hours. E) grinding and sieving the second powder to remove iron to obtain a sodium ion layered metal oxide material; The method for producing the sodium ion layered metal oxide material according to claim 1 .

3. In step A), the solvent used for rough polishing is water and / or alcohol, the solid content of the first slurry is 10-40%, and the particle size of the first slurry is D100<10 μm; The method according to claim 2 .

4. Specifically, the firing process includes: In an oxygen-containing atmosphere, the temperature is increased from room temperature to 120-125°C at a rate of 4-5°C / min, and kept at that temperature for 2-3 hours, then the temperature is increased further to 450-455°C at a rate of 5-7°C / min, and kept at that temperature for 1-2 hours, and then the temperature is increased further to 850-950°C at a rate of 5-8°C / min, and kept at that temperature for 13-20 hours. The method according to claim 2 .

5. During the baking process, the oxygen content is 20-35%, the moisture content is less than 3%, and the carbon dioxide concentration is less than 1%. The method according to claim 2 .

6. After the firing is completed, the mixture is rapidly cooled to obtain a second powder. The rapid cooling is a quenching process. The method according to claim 2 .

7. The sodium ion layered metal oxide material according to claim 1 or the sodium ion layered metal oxide material produced by the production method according to any one of claims 2 to 6, A positive electrode sheet characterized by:

8. The positive electrode sheet according to claim 7, A sodium-ion battery characterized by:

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