High-entropy layered oxide, preparation method thereof and application of high-entropy layered oxide in battery electrode

Abstract

The invention discloses a preparation method of a high-entropy layered oxide, which comprises the following steps: 1) weighing metal nitrate and an organic compound, adding deionized water, stirring and dispersing to form a uniform complex; 2) transferring the complex to Joule thermal equipment, and further performing Joule thermal reaction to obtain a high-entropy layered oxide precursor; 3) grinding and uniformly mixing the high-entropy layered oxide precursor prepared in the step 2), a sodium source and a lithium source to obtain solid powder; and 4) placing the solid powder in Joule thermal equipment for Joule thermal reaction to obtain the high-entropy layered oxide powder. According to the method, metal nitrate is adopted as an oxidizing agent, an organic compound is adopted as a reducing agent, a violent oxidation-reduction reaction occurs during Joule thermal reaction, a large amount of gas and heat are released, metal cations are rapidly diffused, and uniform high-entropy layered oxide is formed. The high-entropy layered oxide has relatively high specific surface area, good crystallinity and excellent electrical properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalytic material preparation, and in particular relates to a high-entropy layered oxide, a preparation method thereof, and application in battery electrodes. Background Art

[0002] As a complementary technology to lithium-ion batteries, sodium-ion batteries have attracted much attention in the field of energy storage due to their advantages such as abundant sodium resources, low cost and high safety. x TMO2 (TM stands for transition metal) has become one of the mainstream cathode materials due to its high specific capacity (>200mAh / g), high energy density, and simple synthesis process. However, traditional high-entropy layered oxides have the following main problems:

[0003] 1) Traditional high-entropy materials rely on multi-step high-temperature calcination (such as calcination at 1000°C for 12 to 24 hours) or complex precursor treatment (such as ball milling, liquid phase mixing, etc.), resulting in long production cycles, high energy consumption, and difficulty in scalability. For example, the solid-phase synthesis of dual-phase materials requires long-term ball milling and high-temperature calcination, which significantly increases costs. Although electrochemical-assisted synthesis is green and environmentally friendly, it requires precise control of voltage (6 to 20V) and electrolyte concentration, has a narrow process window, and the problem of electrolyte recovery has not yet been solved;

[0004] 2) The uneven distribution of multiple elements in high-entropy materials can easily lead to local component segregation, resulting in lattice distortion and crack propagation. Although dual-phase composite structures (such as P2 / O3) combine phase advantages, the phase interface is prone to dynamic reconstruction under high-rate charge and discharge, accelerating capacity decay;

[0005] 3) The residual alkalinity on the surface of layered oxide is strong, which easily reacts with the electrolyte to form an unstable CEI film, increasing the interface impedance. x After cycling, TMO2 materials produce a large amount of Na2CO3 byproducts on their surface, reducing Coulombic efficiency. Sodium ion diffusion kinetics are slow, and while traditional modification strategies (such as anion-anchored separators) improve transmission efficiency, they fail to optimize the material's intrinsic conductivity, leading to a sharp drop in capacity at high rates (capacity retention is less than 70% at 1C).

[0006] 4) Although doping with metals such as Ni and Co improves performance, it increases material costs, which is contrary to the low-cost positioning of sodium-ion batteries. Summary of the Invention

[0007] The present invention aims to address, at least to some extent, one of the technical problems in the related art. To this end, the present invention primarily aims to provide a high-entropy layered oxide that addresses the issues with existing high-entropy layered oxides, such as their tendency to undergo irreversible phase transitions, structural collapse, and interfacial side reactions during cycling, resulting in rapid capacity decay and poor air stability.

[0008] The present invention also discloses a method for preparing the high-entropy layered oxide;

[0009] The invention also discloses the application of the high-entropy layered oxide in sodium ion battery electrodes.

[0010] The purpose of the present invention is achieved through the following technical solutions:

[0011] A method for preparing a high-entropy layered oxide comprises the following steps:

[0012] 1) Weighing a metal nitrate and an organic compound, adding deionized water, stirring and dispersing them to form a uniform complex;

[0013] 2) transferring the complex to a Joule heating device, and then reacting it by Joule heating to obtain a high-entropy layered oxide precursor;

[0014] 3) grinding and mixing the high entropy layered oxide precursor prepared in step 2), the sodium source, and the lithium source to obtain a solid powder;

[0015] 4) placing the solid powder in a Joule heating device to undergo Joule heating reaction to obtain high entropy layered oxide powder.

[0016] In certain specific embodiments, the metal nitrate is a mixture of nickel nitrate, iron nitrate, copper nitrate, manganese nitrate and zinc nitrate.

[0017] Furthermore, the nickel nitrate is nickel nitrate nonahydrate, the iron nitrate is iron nitrate nonahydrate, the copper nitrate is copper nitrate trihydrate, the manganese nitrate is manganese nitrate tetrahydrate, and the zinc nitrate is zinc nitrate tetrahydrate.

[0018] In certain specific embodiments, the mass ratio of the nickel nitrate, iron nitrate, copper nitrate, manganese nitrate and zinc nitrate is (0.6-1.0):(0.5-0.8):(0.2-0.5):(0.5-1.0):(0.2-0.4).

[0019] In some specific embodiments, the organic compound is one or more of urea, citric acid and glycine.

[0020] In some specific embodiments, the mass ratio of the metal nitrate to the organic compound is 1:(0.3-3).

[0021] In certain specific embodiments, the stirring and dispersing process conditions in step 1) are: stirring at a temperature of 60-100° C. and a rotation speed of 600-1000 r / min for 4-8 hours.

[0022] In certain specific embodiments, the mass ratio of the high entropy layered oxide precursor, the sodium source, and the lithium source in step 3) is 2-3:1:0.05-0.1.

[0023] In certain specific embodiments, in step 3), the sodium source is sodium carbonate, and the lithium source is lithium carbonate.

[0024] In certain specific embodiments, step 4) further comprises adding a research aid, wherein the research aid is ethanol.

[0025] In certain specific embodiments, the process conditions of the Joule heat reaction in step 2) and step 4) are: setting the voltage of the Joule heat device to 20-40V, the current to 30-60A, and the time to 15-35s.

[0026] As the same inventive concept, the present invention also provides a high-entropy layered oxide.

[0027] As the same inventive concept, the present invention also provides the use of the high-entropy layered oxide in sodium ion battery electrodes.

[0028] In certain specific embodiments, the specific application method of the high entropy layered oxide in a sodium ion battery electrode is:

[0029] The high-entropy layered oxide powder is weighed, and carbon black and polyvinylidene fluoride are weighed as a conductive agent and a binder. After mixing in a mortar, N-methylpyrrolidone is added dropwise as a solvent and continued to be ground into a uniform slurry; the slurry is coated on a conductive current collector and then transferred to a vacuum oven and dried at 120°C for 12 hours to remove the solvent to prepare a pole piece.

[0030] Compared with the prior art, the present invention has at least the following advantages:

[0031] 1) The preparation method of the present application adopts metal nitrate as oxidant and organic compound as reducing agent; nitrate (NO3 - ) undergoes a vigorous redox reaction with amino (-NH2) or carboxyl (-COOH) groups in organic compounds during the Joule heat reaction, releasing large amounts of gas (such as CO2, H2O, N2) and heat, without the need for additional large amounts of thermal energy. In addition, the Joule heat reaction is fast and the synthesis can be completed in a relatively short time, making it particularly suitable for the large-scale preparation of high-entropy oxides and significantly improving production efficiency.

[0032] 2) The preparation method of the present application uses relatively simple equipment, generally only requiring a heating device (Joule heating device) and a reaction vessel, and does not require special equipment such as high pressure equipment;

[0033] 3) The preparation method of the present invention can uniformly mix the raw materials on the molecular scale through solution mixing before the reaction. During the combustion process, the elements react rapidly at high temperature, which is conducive to the formation of uniform, high-purity high-entropy layered oxides. At the same time, through Joule heat reaction, high-entropy oxides can be rapidly synthesized. The products usually have a high specific surface area and good crystallinity. Due to the rapidity of the combustion reaction, some special microstructures may be formed, which is conducive to improving the electrical properties of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the specific embodiments of the present invention, the following briefly introduces the drawings required for the specific embodiments or the description of the prior art.

[0035] Figure 1 The XRD pattern of the high entropy layered oxide provided in Example 1 of the present invention;

[0036] Figure 2 The XRD pattern of the high entropy layered oxide provided in Example 2 of the present invention;

[0037] Figure 3 The XRD pattern of the high entropy layered oxide provided in Comparative Example 1 of the present invention;

[0038] Figure 4 The XRD pattern of the high entropy layered oxide provided in Comparative Example 2 of the present invention;

[0039] Figure 5 This is a diagram showing the electrochemical performance test of the high entropy layered oxide provided in Example 1 of the present invention;

[0040] Figure 6 A diagram showing the electrochemical performance test of the high entropy layered oxide provided in Example 2 of the present invention;

[0041] Figure 7 This is a diagram showing the electrochemical performance test of the high entropy layered oxide provided in Comparative Example 1 of the present invention;

[0042] Figure 8 This is a diagram showing the electrochemical performance test of the high-entropy layered oxide provided in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0043] The present invention will be further described in detail below with reference to the accompanying drawings and examples. The following examples are merely illustrative and non-restrictive, and should not be used to limit the scope of protection of the present invention.

[0044] When expressing a certain amount, concentration or other value or parameter in the form of a range, preferred range, or preferred upper and lower numerical limits, it should be understood that it is equivalent to specifically disclosing any range by combining any pair of upper range limits or preferred numerical values with any lower range limit or preferred numerical value, without considering whether the range is specifically disclosed. Unless otherwise indicated, the numerical range values listed herein include the endpoints of the range and all integers and fractions within the range.

[0045] Unless otherwise indicated, all percentages, parts, ratios, etc. herein are by weight.

[0046] The materials, methods, and examples herein are illustrative and, unless otherwise indicated, are not to be construed as limiting.

[0047] The present invention provides a method for preparing a high-entropy layered oxide, comprising the following steps:

[0048] 1) Weighing a metal nitrate and an organic compound, adding deionized water, stirring and dispersing them to form a uniform complex;

[0049] 2) transferring the complex to a Joule heating device, and then reacting it by Joule heating to obtain a high-entropy layered oxide precursor;

[0050] 3) grinding and mixing the high entropy layered oxide precursor prepared in step 2), the sodium source, and the lithium source to obtain a solid powder;

[0051] 4) placing the solid powder in a Joule heating device to undergo Joule heating reaction to obtain high entropy layered oxide powder.

[0052] Wherein, the metal nitrate is a mixture of nickel nitrate, iron nitrate, copper nitrate, manganese nitrate and zinc nitrate; the organic compound is one or more of urea, citric acid and glycine. In the technical solution of the present application, nitrate ions act as oxidants in the reaction, and organic compounds act as reducing agents and fuels. This specific reaction relationship enables the reaction to proceed more accurately, limiting the generation of other unnecessary impurities. Once the reaction is initiated, since the amount of the reactants is configured according to a certain ratio, when the reaction reaches a certain level and the reactants are consumed, the reaction will stop in a self-limiting manner, reducing the possibility of side reactions and thereby improving the purity of the product. At the same time, during the Joule heat reaction, the oxidation of citric acid will generate gases such as carbon dioxide and water vapor, and the decomposition of nitrates may also generate some gases. These gases form a protective atmosphere around the reaction system, isolating the reaction products from the outside air. This prevents the products from reacting with or being contaminated by impurities such as oxygen, nitrogen and dust in the air, thereby helping to maintain the high purity of the product.

[0053] In addition, organic compound molecules have multiple functional groups such as carboxyl and hydroxyl groups, which can form complexes with metal ions. During the self-combustion reaction, these complexes will decompose and react according to a certain structure and form. Taking the complex formed by metal nitrate and citric acid as an example, the molecular structure of citric acid will limit the aggregation and growth direction of metal ions, acting as a template to guide the formation of products with smaller particle size and more uniform size distribution. In addition, rapid cooling can inhibit the further growth and agglomeration of product particles at high temperature, so that the product maintains the smaller particle size state formed at the end of the reaction, which is conducive to obtaining products with smaller particle size. At the same time, it also reduces the possibility of the product reacting with external substances during the cooling process and reducing the purity.

[0054] At the same time, the preparation method of the present application adopts metal nitrate as oxidant and organic compound as reducing agent; nitrate (NO3 - ) undergoes a violent redox reaction with the amino group (-NH2) or carboxyl group (-COOH) in organic compounds during the Joule heat reaction, releasing a large amount of gas (such as CO2, H2O, N2) and heat. This self-sustaining high-temperature environment causes metal cations to diffuse rapidly and form high-entropy oxides.

[0055] Simultaneously, by applying a high current pulse to a complex composed of a metal nitrate and an organic compound, a Joule heating reaction occurs. This rapidly generates heat within the complex material, creating a transient high-temperature field accompanied by a heating rate of hundreds of kelvins per second. This internal self-heating mechanism avoids the thermal conduction delays associated with traditional external heating, achieving near-100% energy conversion efficiency. Within this extremely short heating time, the material undergoes a non-equilibrium phase transition. After the current is removed, the material cools down ultrafast through natural heat dissipation, "freezing" the high-entropy metastable state at high temperatures and preventing elemental resegregation or grain coarsening during cooling.

[0056] The test methods used in the following embodiments are mainly:

[0057] 1) XRD pattern analysis test;

[0058] The X-ray diffractometer was a Rigaku SmartLab SE instrument from Japan, using Cu Kα radiation. Scanning rate 5° / min, scanning range 10–80°;

[0059] 2) Electrical performance test

[0060] The electrochemical performance of the samples was tested using the Xinwei equipment according to the constant current charge and discharge method;

[0061] Example 1

[0062] This embodiment provides a method for preparing a high-entropy layered oxide, which specifically includes the following steps:

[0063] 1) Weigh 0.81 g of nickel nitrate hexahydrate, 0.81 g of iron nitrate nonahydrate, 0.29 g of copper nitrate trihydrate, 0.63 g of manganese nitrate tetrahydrate, 0.30 g of zinc nitrate hexahydrate, and 2.74 g of citric acid into a beaker, add an appropriate amount of deionized water as a solvent, and stir at 80°C and 800 rpm for 6 h to form a uniformly dispersed complex;

[0064] 2) Transferring the complex to a crucible and fixing it on a fast Joule heating device fixture, setting the Joule heating device voltage to 30 V, current to 50 A, and time to 30 s, starting the Joule heating device to heat and trigger the auto-combustion reaction. After the reaction is completed, the powder is collected and preliminarily ground to obtain a high-entropy layered oxide precursor;

[0065] 3) Weighing sodium carbonate and lithium carbonate as the sodium source and lithium source, respectively, and then adding the high-entropy layered oxide precursor prepared in step 2) into an agate mortar (wherein the mass ratio of the high-entropy layered oxide precursor, the sodium source, and the lithium source is 2.84:1:0.07), adding an appropriate amount of ethanol as a grinding aid, and grinding for 20 minutes until the ethanol evaporates to obtain a uniform solid powder;

[0066] 4) The solid powder obtained in step 3) is placed in a crucible and fixed on a fast Joule heating device fixture, the voltage of the Joule heating device is set to 35 V, the current is 45 A, and the time is 25 s, and the Joule heating device is started to obtain high entropy layered oxide powder by fast Joule heating.

[0067] Example 2

[0068] 1) Weigh 0.81 g nickel nitrate hexahydrate, 0.81 g iron nitrate nonahydrate, 0.29 g copper nitrate trihydrate, 0.63 g manganese nitrate tetrahydrate, 0.30 g zinc nitrate hexahydrate, and 1.07 g glycine into a beaker. Add an appropriate amount of deionized water as a solvent and stir at 80°C and 800 rpm for 6 h to form a uniformly dispersed complex.

[0069] 2) Transferring the complex to a crucible and fixing it on a fast Joule heating device fixture, setting the Joule heating device voltage to 30 V, current to 50 A, and time to 30 s, starting the Joule heating device to heat and trigger the auto-combustion reaction. After the reaction is completed, the powder is collected and preliminarily ground to obtain a high-entropy layered oxide precursor;

[0070] 3) Weighing sodium carbonate and lithium carbonate as the sodium source and lithium source, respectively, and then adding the high-entropy layered oxide precursor prepared in step 2) into an agate mortar (wherein the mass ratio of the high-entropy layered oxide precursor, the sodium source, and the lithium source is 2.84:1:0.07), adding an appropriate amount of ethanol as a grinding aid, and grinding for 20 minutes until the ethanol evaporates to obtain a uniform solid powder;

[0071] 4) The solid powder obtained in step 3) is placed in a crucible and fixed on a fast Joule heating device fixture, the voltage of the Joule heating device is set to 35 V, the current is 45 A, and the time is 25 s, and the Joule heating device is started to obtain high entropy layered oxide powder by fast Joule heating.

[0072] Example 3

[0073] This embodiment provides a method for preparing a high-entropy layered oxide, which specifically includes the following steps:

[0074] 1) Weigh 0.7 g nickel nitrate hexahydrate, 0.5 g iron nitrate nonahydrate, 0.2 g copper nitrate trihydrate, 0.5 g manganese nitrate tetrahydrate, 0.2 g zinc nitrate hexahydrate, and 2.5 g citric acid into a beaker, add an appropriate amount of deionized water as a solvent, and stir at 600 rpm for 8 h at 60°C to form a uniformly dispersed complex;

[0075] 2) Transferring the complex to a crucible and fixing it on a fast Joule heating device fixture, setting the Joule heating device voltage to 20 V, current to 30 A, and time to 35 s, starting the Joule heating device to heat and trigger the auto-combustion reaction. After the reaction is completed, the powder is collected and preliminarily ground to obtain a high-entropy layered oxide precursor;

[0076] 3) Weighing sodium carbonate and lithium carbonate as the sodium source and lithium source, respectively, and then adding the high-entropy layered oxide precursor prepared in step 2) into an agate mortar (wherein the mass ratio of the high-entropy layered oxide precursor, the sodium source, and the lithium source is 2.84:1:0.07), adding an appropriate amount of ethanol as a grinding aid, and grinding for 20 minutes until the ethanol evaporates to obtain a uniform solid powder;

[0077] 4) The solid powder obtained in step 3) is placed in a crucible and fixed on a fast Joule heating device fixture, the voltage of the Joule heating device is set to 25 V, the current is 35 A, and the time is 30 s, and the Joule heating device is started to obtain high entropy layered oxide powder by fast Joule heating.

[0078] Example 4

[0079] This embodiment provides a method for preparing a high-entropy layered oxide, which specifically includes the following steps:

[0080] 1) Weigh 1.0 g of nickel nitrate hexahydrate, 0.7 g of iron nitrate nonahydrate, 0.5 g of copper nitrate trihydrate, 1.0 g of manganese nitrate tetrahydrate, 0.40 g of zinc nitrate hexahydrate, and 4.8 g of citric acid in a beaker. Add an appropriate amount of deionized water as a solvent and stir at 1000 rpm for 4 h at 100°C to form a uniformly dispersed complex.

[0081] 2) Transferring the complex to a crucible and fixing it on a fast Joule heating device fixture, setting the Joule heating device voltage to 40 V, current to 60 A, and time to 25 s, starting the Joule heating device to heat and trigger the auto-combustion reaction. After the reaction is completed, the powder is collected and preliminarily ground to obtain a high-entropy layered oxide precursor;

[0082] 3) Weighing sodium carbonate and lithium carbonate as the sodium source and lithium source, respectively, and then adding the high-entropy layered oxide precursor prepared in step 2) into an agate mortar (wherein the mass ratio of the high-entropy layered oxide precursor, the sodium source, and the lithium source is 2.84:1:0.07), adding an appropriate amount of ethanol as a grinding aid, and grinding for 20 minutes until the ethanol evaporates to obtain a uniform solid powder;

[0083] 4) The solid powder obtained in step 3) is placed in a crucible and fixed on a fast Joule heating device fixture, the voltage of the Joule heating device is set to 40 V, the current is 50 A, and the time is 25 s, and the Joule heating device is started to obtain high entropy layered oxide powder by fast Joule heating.

[0084] Comparative Example 1

[0085] This comparative example provides a method for preparing a high-entropy layered oxide, which is basically the same as Example 1, except that the high-entropy layered oxide precursor is prepared by ball milling, specifically:

[0086] 1) Weigh 0.81 g of nickel nitrate hexahydrate, 0.81 g of iron nitrate nonahydrate, 0.29 g of copper nitrate trihydrate, 0.63 g of manganese nitrate tetrahydrate, 0.30 g of zinc nitrate hexahydrate, and 2.74 g of citric acid into a beaker, add an appropriate amount of deionized water as a solvent, and stir at 80°C and 800 rpm for 6 h to form a uniformly dispersed complex;

[0087] 2) weighing sodium carbonate and lithium carbonate as a sodium source and a lithium source, respectively, and adding them to a ball mill jar, then adding the complex prepared in step 2) to an agate mortar (wherein the mass ratio of the complex, the sodium source, and the lithium source is 2.84:1:0.07), adding an appropriate amount of ethanol as a grinding aid, and ball milling at 300 rpm for 6 h until the ethanol evaporates to obtain a uniform high-entropy layered oxide precursor;

[0088] 3) The high-entropy layered oxide precursor obtained in step 2) is placed in a crucible and fixed on a fast Joule heating device fixture, the voltage of the Joule heating device is set to 35 V, the current is 45 A, and the time is 25 s, and the Joule heating device is started to obtain high-entropy layered oxide powder by fast Joule heating.

[0089] Comparative Example 2

[0090] This comparative example provides a method for preparing a high-entropy layered oxide, which is basically the same as Example 1, except that the high-entropy layered oxide is prepared by calcining in a muffle furnace, specifically:

[0091] 1) Weigh 0.81 g of nickel nitrate hexahydrate, 0.81 g of iron nitrate nonahydrate, 0.29 g of copper nitrate trihydrate, 0.63 g of manganese nitrate tetrahydrate, 0.30 g of zinc nitrate hexahydrate, and 2.74 g of citric acid into a beaker, add an appropriate amount of deionized water as a solvent, and stir at 80°C and 800 rpm for 6 h to form a uniformly dispersed complex;

[0092] 2) Transferring the complex to a crucible and fixing it on a fast Joule heating device fixture, setting the Joule heating device voltage to 30 V, current to 50 A, and time to 30 s, starting the Joule heating device to heat and trigger the auto-combustion reaction. After the reaction is completed, the powder is collected and preliminarily ground to obtain a high-entropy layered oxide precursor;

[0093] 3) Weighing sodium carbonate and lithium carbonate as the sodium source and lithium source, respectively, and then adding the high-entropy layered oxide precursor prepared in step 2) into an agate mortar (wherein the mass ratio of the high-entropy layered oxide precursor, the sodium source, and the lithium source is 2.84:1:0.07), adding an appropriate amount of ethanol as a grinding aid, and grinding for 20 minutes until the ethanol evaporates to obtain a uniform solid powder;

[0094] 4) placing the solid powder obtained in step 3) in a corundum boat, then placing the corundum boat in a muffle furnace, raising the temperature to 900° C. at a heating rate of 5° C. / min, maintaining the temperature for 24 h, and then naturally cooling the mixture to obtain a high-entropy layered oxide powder.

[0095] Application Examples

[0096] The high-entropy oxide prepared in this application is mainly used for sodium-ion battery electrodes. Specifically: 80 mg of the high-entropy layered oxide powder in the above scheme is taken, 10 mg of carbon black and 10 mg of polyvinylidene fluoride are weighed as a conductive agent and a binder respectively, and after mixing in a mortar, an appropriate amount of N-methylpyrrolidone is added as a solvent and continued to be ground into a uniform slurry; the slurry is coated on a conductive current collector and then transferred to a vacuum oven and dried at 120°C for 12 hours to remove the solvent to prepare an electrode.

[0097] Performance testing:

[0098] Test Example 1

[0099] This test example takes the high entropy layered oxides prepared in Example 1, Example 2, Comparative Example 1 and Comparative Example 2 as examples, and performs XRD diffraction pattern analysis on the high entropy layered oxides prepared therefrom. The results are as follows: Figure 1-4 As shown, Figure 1 is the XRD pattern of Example 1; Figure 2 This is the XRD pattern of Example 2. Figure 1 and Figure 2 It can be seen that no obvious impurity peaks appear, indicating the successful preparation of pure phase O3 type layered structure; Figure 3 The XRD pattern of comparative example 1 is shown in FIG. Figure 3 It can be seen that there are obvious impurity peaks, which may be due to the failure of uniform mixing of the precursors, resulting in phase separation during the subsequent rapid Joule heating treatment. Figure 4 The XRD pattern of comparative example 2 is shown in FIG. Figure 4 It can be seen that there are obvious impurity peaks, which may be due to phase separation caused by long-term heating.

[0100] Test Example 2

[0101] This test example uses the high-entropy layered oxides prepared in Examples 1 and 2, as well as Comparative Examples 1 and 2. Electrodes were prepared using the methods described in the previous examples. After drying, the electrodes were cut into circular shapes with a diameter of 12 mm using a punching machine. In a glove box, half-cells were assembled using these electrodes as the positive electrode and a sodium metal sheet as the negative electrode. After 12 hours of rest, the electrochemical performance of the high-entropy oxide cathode was tested.

[0102] The results are as follows Figure 5-Figure 8 As shown in the figure, the first discharge specific capacities of Examples 1 and 2 are 143.09 and 122.15 mAh g, respectively. -1 , while the first discharge specific capacities of comparative examples 1 and 2 were only 47.76 and 85.54 mAh g -1 . Combined with the XRD diffraction pattern analysis in Test Example 1, it is inferred that the reason for the different first discharge specific capacity may be that the comparative example containing the impurity phase has a lower specific capacity because the lattice parameter mismatch between the impurity phase and the main phase (O3-type layered structure) forms a high-energy phase interface. This interface hinders the continuous diffusion channel of sodium ions between the layers and leads to local isolation of active sites. The inactive elements in the impurity phase occupy the transition metal layer position, dilute the concentration of the redox active metal, and reduce the number of effective sites involved in charge compensation. At the same time, the electronic structure of the impurity phase may not contribute to the redox reaction, resulting in overall capacity loss.

[0103] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. A method for preparing a high entropy layered oxide, characterized in that: The steps include: 1) Weighing a metal nitrate and an organic compound, adding deionized water, stirring and dispersing them to form a uniform complex; 2) transferring the complex to a Joule heating device, and then reacting it by Joule heating to obtain a high-entropy layered oxide precursor; 3) grinding and mixing the high entropy layered oxide precursor prepared in step 2), the sodium source, and the lithium source to obtain a solid powder; 4) placing the solid powder in a Joule heating device to undergo Joule heating reaction to obtain high entropy layered oxide powder.

2. The method for preparing a high entropy layered oxide according to claim 1, wherein: The metal nitrate is a mixture of nickel nitrate, iron nitrate, copper nitrate, manganese nitrate and zinc nitrate.

3. The method for preparing a high entropy layered oxide according to claim 2, wherein: The nickel nitrate is nickel nitrate nonahydrate, the iron nitrate is iron nitrate nonahydrate, the copper nitrate is copper nitrate trihydrate, the manganese nitrate is manganese nitrate tetrahydrate, and the zinc nitrate is zinc nitrate tetrahydrate.

4. The method for preparing a high entropy layered oxide according to any one of claims 1 to 3, characterized in that: The mass ratio of the nickel nitrate, iron nitrate, copper nitrate, manganese nitrate and zinc nitrate is (0.6-1.0):(0.5-0.8):(0.2-0.5):(0.5-1.0):(0.2-0.4).

5. The method for preparing a high entropy layered oxide according to claim 1, wherein: The organic compound is one or more of urea, citric acid and glycine.

6. The method for preparing a high entropy layered oxide according to claim 4, wherein: The mass ratio of the metal nitrate to the organic compound is 1:(0.3-3).

7. The method for preparing a high entropy layered oxide according to claim 1, wherein: The stirring and dispersing process conditions in step 1) are: stirring at a temperature of 60-100° C. and a rotation speed of 600-1000 r / min for 4-8 hours.

8. The method for preparing a high entropy layered oxide according to claim 7, wherein: The process conditions of the Joule heat reaction in step 2) and step 4) are as follows: setting the voltage of the Joule heat device to 20-40V, the current to 30-60A, and the time to 15-35s.

9. A high entropy layered oxide prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the high entropy layered oxide according to claim 9 in a sodium ion battery electrode.

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