High-entropy sodium-ion positive electrode material, preparation method and application thereof

Abstract

The application relates to a high-entropy sodium-ion positive electrode material and a preparation method and application thereof. 0.25 Zn 0.07 Ti 0.18 Zr 0.15 M x O2; M is two or more rare earth metal elements. The preparation method comprises the following steps: step A: mixing a sodium source, a rare earth metal oxide and a transition metal source in a certain molar ratio to obtain uniformly mixed precursor powder; and step B: heating and warming the uniformly mixed precursor powder and applying a certain pressure, and heating and keeping warm to obtain the positive electrode material. In the application, two or more rare earth metal elements are introduced when the high-entropy positive electrode material is designed, high-content rare earth metal elements are introduced in a pressure sintering mode, the material structure is greatly stabilized, the layer spacing of the material is widened, a high-speed sodium-ion transmission channel is provided, and the rate performance of the material is greatly improved.

Description

Technical Field

[0001] This invention relates to the technical field of sodium-ion batteries, and in particular to a high-entropy sodium-ion cathode material, its preparation method, and its application. Background Technology

[0002] Layered sodium ion oxide Na x TMO2 (TM being a transition metal) has attracted widespread attention from researchers due to its rich compositional diversity and tunable electrochemical properties. Layered oxide materials possess two-dimensional transport channels, exhibiting rapid sodium ion transport rates and high compaction density, making them the preferred route for many battery companies. However, layered oxide materials are prone to irreversible phase transitions above 4.0V, forcing a limitation on their charging voltage to below 4.0V in battery applications, significantly impacting their energy density. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a high-entropy sodium-ion cathode material, its preparation method, and its applications. This invention designs and synthesizes a novel high-entropy sodium-ion cathode material, thereby increasing the upper voltage limit of layered oxide cathode materials.

[0004] The first objective of this invention is to provide a high-entropy sodium-ion cathode material, wherein the high-entropy sodium-ion cathode material is NaNi. 0.25 Zn 0.07 Ti 0.18 Zr 0.15 M x O2; M represents two or more rare earth metal elements; x represents the molar ratio of the corresponding element, and satisfies 0 <x<0.35。

[0005] In one embodiment of the present invention, M is selected from one or more of scandium Sc, yttrium Y, lanthanum La, cerium Ce, praseodymium Pr, neodymium Nd, samarium Sm, europium Eu, gadolinium Gd, terbium Tb, dysprosium Dy, holmium Ho, erbium Er, thulium Tm, ytterbium Yb, and lutetium Lu.

[0006] The second objective of this invention is to provide a method for preparing a high-entropy sodium-ion cathode material, comprising the following steps:

[0007] Step A: Mix sodium source, rare earth metal oxide, and transition metal source in a certain molar ratio to obtain a uniformly mixed precursor powder;

[0008] Step B: Under certain pressure conditions, the uniformly mixed precursor powder is sintered to obtain the cathode material.

[0009] In one embodiment of the present invention, in step A, the sodium source is one or more of sodium carbonate, sodium hydroxide, sodium acetate, sodium oxalate, and sodium nitrate.

[0010] In one embodiment of the present invention, in step A, the transition metal source is selected from one or more of nickel source, zinc source, titanium source, and zirconium source.

[0011] In one embodiment of the present invention, in step A, the particle size D50 of the transition metal source is ≤50nm.

[0012] In one embodiment of the present invention, in step A, the nickel source is nickel oxide and / or nickel trioxide.

[0013] In one embodiment of the present invention, in step A, the zinc source is one or more of zinc oxide, zinc suboxide, and zinc dioxide.

[0014] In one embodiment of the present invention, in step A, the titanium source is titanium dioxide; the zirconium source is zirconium dioxide.

[0015] In one embodiment of the present invention, in step A, the rare earth metal oxide is selected from one or more of lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, and lutetium oxide.

[0016] In one embodiment of the present invention, in step B, the heating rate of the sintering treatment is 1-4°C / min, the temperature is 800-1000°C, the time is 8-20h, and the pressure is 20-30MPa.

[0017] A third objective of this invention is to provide a positive electrode sheet comprising the aforementioned high-entropy sodium ion positive electrode material.

[0018] A fourth objective of the present invention is to provide a sodium-ion battery, including the aforementioned positive electrode.

[0019] The technical solution of the present invention has the following advantages compared with the prior art:

[0020] 1. Common layered oxides typically undergo irreversible phase transitions when charged above 4.0V, leading to structural changes and significantly reducing the material's cycling performance. This invention employs a high-entropy approach, introducing various rare-earth metal elements to stabilize the material's structure, thereby ensuring good cycling stability even at an upper voltage limit of 4.15V.

[0021] 2. In designing high-entropy cathode materials, this invention introduces two or more rare earth metal elements. As is well known, rare earth metal elements can only be doped in small amounts due to their large ionic radii. However, this invention introduces high amounts of rare earth elements through pressure sintering without the generation of impurity phases.

[0022] 3. By introducing large-size, high-content rare earth metal elements through reasonable structural design, the material structure is greatly stabilized, the interlayer spacing is widened, high-speed sodium ion transport channels are provided, and the rate performance of the material is greatly improved.

[0023] 4. Rare earth metals have a large number of unpaired electrons and possess multi-electron properties, which can act as an "electron bank," improving the electron transport capability of materials and further enhancing their rate performance.

[0024] In summary, the high-entropy sodium-ion cathode material strategy provided by this invention improves the cycling and rate performance of layered oxide materials while increasing the upper limit voltage of the materials. Attached Figure Description

[0025] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...

[0026] Figure 1 This is a scanning electron microscope image of Embodiment 1 of the present invention.

[0027] Figure 2 These are the XRD diffraction patterns of Embodiment 1 and Comparative Example 3 of the present invention. Detailed Implementation

[0028] To address the technical problem in the field of battery cathode materials that rare earth elements can only be doped in trace amounts due to their large ionic radii, this invention provides a cathode material with high rare earth element doping content, its preparation method, and its application.

[0029] This invention provides a high-entropy sodium-ion cathode material, wherein the high-entropy sodium-ion cathode material is NaNi. 0.25 Zn 0.07 Ti 0.18 Zr 0.15 M x O2; M represents two or more rare earth metal elements; x represents the molar ratio of the corresponding element, and satisfies 0 <x<0.35。

[0030] In a specific embodiment, M is selected from one or more of scandium Sc, yttrium Y, lanthanum La, cerium Ce, praseodymium Pr, neodymium Nd, promethium Pm, samarium Sm, europium Eu, gadolinium Gd, terbium Tb, dysprosium Dy, holmium Ho, erbium Er, thulium Tm, ytterbium Yb, and lutetium Lu.

[0031] This invention also provides a method for preparing a high-entropy sodium-ion cathode material, comprising the following steps:

[0032] Step A: Mix sodium source, rare earth metal oxide, and transition metal source in a certain molar ratio to obtain a uniformly mixed precursor powder;

[0033] Step B: Under certain pressure conditions, the uniformly mixed precursor powder is sintered to obtain the high-entropy sodium ion cathode material.

[0034] In a specific embodiment, in step A, the sodium source is one or more of sodium carbonate, sodium hydroxide, sodium acetate, sodium oxalate, and sodium nitrate.

[0035] In a specific embodiment, in step A, the transition metal source is selected from one or more of nickel source, zinc source, titanium source and zirconium source;

[0036] In a specific embodiment, the particle size D50 of the transition metal source is ≤50nm.

[0037] In a specific embodiment, the nickel source is nickel oxide and / or nickel trioxide.

[0038] In a specific embodiment, the zinc source is one or more of zinc oxide, zinc suboxide, and zinc dioxide.

[0039] In a specific embodiment, the titanium source is titanium dioxide; the zirconium source is zirconium dioxide.

[0040] In a specific embodiment, the rare earth metal oxide is selected from one or more of lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, and lutetium oxide.

[0041] In this invention, the sodium source, nickel source, zinc source, titanium source, zirconium source, and rare earth metal oxide mentioned above are in the form of NaNi 0.25 Zn 0.07 Ti 0.18 Zr 0.15 M x The molar ratio of O2 is used for mixing.

[0042] In a specific embodiment, in step A, the method of uniform mixing can be any method that can achieve uniform mixing in the art, and ball milling is preferred.

[0043] In a specific embodiment, in step B, the heating rate of the sintering treatment is 1–4 °C / min, which can be 1–3 °C / min, 1–2 °C / min, specifically 1 °C / min, 1.5 °C / min, 2 °C / min, 2.5 °C / min, 3 °C / min, 3.5 °C / min, 4 °C / min, or any value between any two values; the temperature is 800–1000 °C, which can be 800–900 °C, 900–1000 °C, or 1–3 °C / min, 1–2 °C / min, specifically 1 °C / min, 1.5 °C / min, 2 °C / min, 2.5 °C / min, 3 °C / min, 3.5 °C / min, 4 °C / min, or any value between any two values; The temperature range is 0-1000℃, specifically 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, 890℃, 900℃, 910℃, 920℃, 930℃, 940℃, 950℃, 960℃, 970℃, 980℃, 990℃, 1000℃, or any value between any two of these two values; the time is 8-20 hours, and the pressure is 20-30 MPa.

[0044] In a specific embodiment, in step B, the apparatus for pressure sintering is an apparatus capable of pressurizing and heating in the art, and a vacuum bidirectional pressurized atmosphere furnace is preferred.

[0045] In this invention, a lower heating rate helps to achieve a more compact sintering of the material, which is more conducive to the incorporation of rare earth elements into the layered material. If the temperature rises too quickly, the incorporation of rare earth metal elements will be significantly affected. This invention introduces a high content of rare earth metal elements through pressure sintering without the generation of impurity phases. Pressure sintering during material preparation accelerates the diffusion process of sintered rare earth metal elements in the solid phase of the material, which is beneficial to the incorporation of rare earth metal elements.

[0046] In a specific embodiment of the present invention, the environmental conditions for the synthesis of the above-mentioned materials are such that the ambient humidity is ≤5% to prevent the materials from getting damp.

[0047] The present invention provides a positive electrode sheet, comprising the aforementioned high-entropy sodium ion positive electrode material.

[0048] In a specific embodiment of the present invention, the preparation method of the positive electrode sheet is a conventional preparation method in the art and is not particularly limited.

[0049] The present invention provides a sodium-ion battery, including the aforementioned positive electrode.

[0050] In a specific embodiment of the present invention, the sodium-ion battery further includes a negative electrode, a separator, and an electrolyte.

[0051] In a specific embodiment of the present invention, the active material of the negative electrode sheet is a conventional active material in the art, without any particular limitation, and may be selected from one or more combinations of lithium metal, lithium metal alloy, carbon silicon composite material, graphite, lithium metal nitride, antimony oxide, and carbon germanium composite material.

[0052] In a specific embodiment of the present invention, the diaphragm is a commonly used diaphragm in the art and is not particularly limited. One or more composite membranes commonly used in the art can be selected. Alternatively, an organic coating or an inorganic coating can be coated on the base membrane surface of the diaphragm. The base membrane of the diaphragm can be a polymer diaphragm of at least one of polyethylene, polypropylene, polyacrylonitrile, polyvinyl alcohol, polyarylether sulfone, and polyvinylidene fluoride.

[0053] In specific embodiments of the present invention, the above-mentioned method for preparing sodium-ion batteries is a conventional method in the art and is not particularly limited.

[0054] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0055] Example 1:

[0056] This embodiment provides a method for preparing and applying a cathode material.

[0057] (1) The preparation method of the positive electrode material is as follows:

[0058] 1.1 Sodium acetate (5 wt% excess), nickel oxide, zinc oxide, titanium dioxide, zirconium dioxide, lanthanum oxide, and samarium oxide were added according to the NaNi... 0.25 Zn 0.07 Ti 0.18 Zr 0.15 La 0.2 Sm 0.15 After weighing the molar ratio of O2, place it in a ball mill jar and ball mill at 900 rpm / min for 3.5 h to obtain a uniformly mixed precursor powder;

[0059] 1.2 The homogeneously mixed precursor powder was placed in a mold of a vacuum bidirectional pressure furnace. A pressure of 20 MPa was simultaneously applied within the furnace at a heating rate of 3 °C / min. After heating to 900 °C, the temperature was held for 10 h, and then allowed to cool naturally to obtain the high-entropy sodium-ion cathode material NaNi. 0.25 Zn 0.07 Ti 0.18 Zr 0.15 La 0.2 Sm 0.15 O2, the structural characterization results of the obtained cathode material are shown in Figure 2 .

[0060] (2) Preparation of sodium-ion batteries

[0061] NaNi 0.25 Zn 0.07 Ti 0.18 Zr 0.15La 0.2 Sm 0.15 O2 material, conductive agent Super P, and binder PVDF were ground uniformly at a mass ratio of 9:0.5:0.5. An appropriate amount of NMP was then added to adjust the slurry to a solid content of 65%, which was then evenly coated onto aluminum foil. The mixture was dried in a forced-air drying oven at 80℃ for 1 hour, followed by drying in a vacuum drying oven at 120℃ for 12 hours. Afterward, it was cut into 14mm circular positive electrode sheets using a cutting machine. A CR2032 coin cell was assembled in a high-purity argon-filled glove box using a 14mm diameter, 0.2mm thick sodium metal sheet as the negative electrode, a 0.1mol / L sodium perchlorate / ethylene carbonate / dimethyl carbonate solution as the electrolyte, and a 16mm diameter Whatman GF / F glass fiber as the separator.

[0062] Example 2

[0063] This embodiment follows the same preparation method as Example 1, except that the high-entropy sodium ion cathode material prepared is NaNi. 0.25 Zn 0.07 Ti 0.18 Zr 0.15 Ce 0.2 Nd 0.15 O2; The preparation and testing methods for sodium ions are the same as in Example 1.

[0064] Example 3

[0065] This embodiment follows the same preparation method as Example 1, except that the high-entropy sodium ion cathode material prepared is NaNi. 0.25 Zn 0.07 Ti 0.18 Zr 0.15 La 0.2 Lu 0.15 O2; The preparation and testing methods for sodium ions are the same as in Example 1.

[0066] Example 4

[0067] This embodiment follows the same preparation method as Example 1, except that the high-entropy sodium ion cathode material prepared is NaNi. 0.25 Zn 0.07 Ti 0.18 Zr 0.15 La 0.2.5 Ho 0.1 O2; The preparation and testing methods for sodium ions are the same as in Example 1.

[0068] Comparative Example 1

[0069] This comparative example was prepared entirely according to the scheme of Example 1, except that the sodium-ion battery layered oxide cathode material prepared was NaNi.0.25 Fe 0.3 Mn 0.45 O2; The preparation and testing methods for sodium ions are the same as in Example 1.

[0070] Comparative Example 2

[0071] This comparative example was prepared entirely according to the scheme of Example 1, except that the high-entropy sodium-ion battery layered oxide cathode material prepared was NaNi. 0.25 Zn 0.07 Ti 0.18 Zr 0.15 Al 0.2 Mn 0.15 O2; The preparation and testing methods for sodium ions are the same as in Example 1.

[0072] Comparative Example 3

[0073] This comparative example was prepared entirely according to the scheme of Example 1, except that the high-entropy sodium-ion battery layered oxide cathode material was prepared using NaNi without applying pressure. 0.25 Zn 0.07 Ti 0.18 Zr 0.15 La 0.2 Sm 0.1 5O2; The preparation and testing methods for sodium ions are the same as in Example 1, and the structural characterization results of the obtained cathode material are shown in [reference needed]. Figure 2 .

[0074] Performance testing

[0075] Charge-discharge tests were conducted using a constant current charge-discharge mode at a current density of 0.1C. The tests included the first charge-discharge cycle, rate performance, and capacity retention after 100 charge-discharge cycles at 1C for the materials of the examples and comparative examples in sodium-ion batteries. The electrochemical performance results of the O3 phase layered oxide material prepared in this example are shown in Table 1, under the conditions of a discharge cutoff voltage of 2.0V and a charge cutoff voltage of 4.15V.

[0076] Table 1. Electrochemical performance of Examples 1-4 and Comparative Examples 1-3

[0077]

[0078] Examples 1-4 and Comparative Examples 1-3 use the same main material type. Examples 1-4, prepared using the high-entropy sodium-ion cathode material preparation method provided by this invention, exhibit good cycle stability and rate performance under high voltage. Comparative Example 1 uses a common ternary layered oxide material with the same nickel content as the material prepared in Example 1. Within a voltage range of 2-4.15V, its discharge capacity and first-time efficiency are lower than those of Examples 1-4, and its capacity retention is only 76.6%. Comparative Example 2 uses a common high-entropy sodium-ion cathode material. Its electrochemical performance is slightly improved compared to Comparative Example 1, but still inferior to Examples 1-4. Comparative Example 3 was heated without any pressure. Figure 2 The XRD pattern shows that many impurity phases are generated, indicating that rare earth elements are not completely incorporated. Therefore, the capacity utilization, rate performance and cycle performance of this material are not as good as those of Examples 1-4.

[0079] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a high-entropy sodium-ion battery cathode material, characterized in that, The cathode material of the high-entropy sodium-ion battery is NaNi. 0.25 Zn 0.07 Ti 0.18 Zr 0.15 M x O2; x is the molar ratio of the corresponding element, and satisfies x=0.35; M refers to La and Sm; The preparation method includes the following steps: Step A: Sodium source, lanthanum oxide, samarium oxide, and transition metal source are mixed in a certain molar ratio to obtain a uniformly mixed precursor powder; the transition metal source includes nickel source, zinc source, titanium source, and zirconium source; Step B: Under certain pressure conditions, the uniformly mixed precursor powder is sintered to obtain the high-entropy sodium-ion battery cathode material. In step B, the heating rate of the sintering treatment is 1~4℃ / min, the temperature is 800~1000℃, the time is 8~20h, and the pressure is 20~30MPa.

2. The preparation method according to claim 1, characterized in that, In step A, at least one or two of the following conditions must be met: (1) The sodium source is one or more of sodium carbonate, sodium hydroxide, sodium acetate, sodium oxalate, and sodium nitrate; (2) The particle size D50 of the transition metal source is ≤50nm.

3. The preparation method according to claim 1, characterized in that, The nickel source is nickel oxide and / or nickel trioxide; the zinc source is zinc oxide.

4. The preparation method according to claim 1, characterized in that, The titanium source is titanium dioxide; the zirconium source is zirconium dioxide.

5. A positive electrode sheet, characterized in that, Including the high-entropy sodium-ion battery cathode material prepared by the preparation method according to any one of claims 1-4.

6. A sodium-ion battery, characterized in that, Includes the positive electrode sheet as described in claim 5.

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