High-entropy P2-O3 composite system sodium ion positive electrode material, preparation method thereof and sodium battery

Abstract

The invention discloses a high-entropy P2-O3 composite system sodium ion positive electrode material, a preparation method thereof and a sodium battery, and belongs to a new energy material technology. The method comprises the steps that a first reactant, metal oxide and solid powder of a sodium source are blended, sintered and cooled, the component of the first reactant is NiyFezMn (1-3y-z) (OH) (2-4y), and the particle size of the first reactant is 1-20 micrometers; the metal oxide is any two of TiO2, MgO, Co3O4, SnO2, ZrO2, La2O3 and CeO2, and the particle size D50 of the metal oxide is less than or equal to 5 microns; the sodium source is selected from any one of sodium carbonate, sodium bicarbonate, sodium nitrate and sodium acetate, and the particle size D50 is less than or equal to 10 microns; the particle size of the first reactant is larger than the particle size D50 of the metal oxide, and the particle size D50 of the sodium source is larger than the particle size D50 of the metal oxide.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy sodium ion batteries, and in particular to a high-entropy P2-O3 composite system sodium ion positive electrode material, a preparation method thereof, and a sodium battery. Background Art

[0002] With the continued rise in global energy demand and increasing attention to environmental protection, the development and efficient utilization of renewable energy have become a key development direction in the energy sector. However, renewable energy sources (such as solar and wind energy) are intermittent and unstable, requiring efficient energy storage systems to ensure a stable supply and flexible allocation of energy. Sodium-ion batteries, due to their abundant resources, low cost, and environmental friendliness, have shown great potential in the energy storage field and are expected to become one of the key solutions for future large-scale energy storage technologies.

[0003] One of the core components of sodium-ion batteries is the cathode material, whose performance directly determines key indicators such as the battery's energy density, cycle stability, rate performance, and safety. In recent years, high-entropy materials, as an emerging material system, have attracted widespread attention due to their unique structural and performance characteristics. High-entropy materials are usually composed of five or more main elements, with similar molar fractions of each element. They have high entropy effects, size effects, electronegativity effects, and synergistic effects, which can effectively improve the overall performance of the material. Introducing the concept of high-entropy materials into the research and development of sodium-ion battery cathode materials is expected to break through the performance bottleneck of traditional cathode materials and develop new high-performance and high-stability cathode materials, thereby promoting the further development of sodium-ion battery technology and meeting the growing demand of the energy storage market.

[0004] The positive electrode materials of sodium ion batteries can be mainly divided into oxides, polyanions, Prussian blue and organic compounds. Among them, oxide positive electrode materials are divided into layered oxides and tunnel oxides. According to the coordination configuration of sodium ions and the stacking mode of oxygen, layered oxides are divided into structures such as P2 and O3 (P and O are Prismatic and Octahedral respectively; 2 and 3 represent repeating units ABBA and ABCABC). NaO6 and TMO6 layers are arranged alternately, and the space groups corresponding to O3 and P2 are R-3m and P63 / mmc respectively.

[0005] P2 and O3 are two common structural types in layered oxide cathode materials, commonly found in sodium-ion batteries. The P2 structure generally has good cycle stability, but the specific capacity may be lower; while the O3 structure, although high in initial capacity, is prone to structural instability at high voltages, resulting in decreased cycle performance. Therefore, compared with the pure O3 system, the P2-O3 composite system has improved cycle stability at high voltages. Under high voltage conditions, the O3 structure may be more prone to phase transition or structural collapse, and the introduction of the P2 structure may have played a stabilizing role. On the other hand, compared with pure P2 materials, the hybrid structure improves the specific capacity, and the O3 structure provides a higher sodium ion storage capacity, thereby compensating for the lower capacity of the P2 structure.

[0006] At present, the preparation method of P2-O3 composite system sodium ion positive electrode material is mainly high temperature solid phase sintering method. For example, Chinese patent CN116504938A discloses a P2 / O3 composite manganese-based layered oxide material and preparation method. The chemical formula of the material is: Na x Ni a Zn b Mn 1-a-b-c Ti c O2 (0.6≤x≤1.0, 0≤a≤0.6, 0≤b≤0.4, 0≤c≤0.4, 0.2≤1-abc≤0.8), the preparation method of which is to fully mix a sodium source, a nickel source, a zinc source, a manganese source and a titanium source according to a certain stoichiometric ratio and then calcine at a high temperature to obtain the P2 / O3 composite manganese-based layered oxide material; Chinese patent CN116936778A discloses a sodium ion battery positive electrode material and its preparation method, the chemical formula of which is Na n Ni x Mn y Ti z M 1-x-y-z O2, wherein 0.55≤n≤0.87, 0.1≤x≤0.4, 0.3≤y≤0.7, 0.1≤z≤0.4, and M is any one of La, Ce, and Y; the preparation method comprises the following steps: mixing a sodium source, metallic manganese powder, nickel oxide, titanium oxide, and rare earth oxide according to the chemical formula Na n Ni x Mn y Ti z M 1-x-y- z The molar ratio of each element in O2 is weighed, and the sodium source is designed to be in excess of 2%-5%. After mixing, dry ball milling is performed for 5-20 hours to obtain a precursor; the precursor is then calcined at 350-600°C for 5-10 hours, and then calcined at 800-1000°C for 10-20 hours to obtain a sodium ion battery positive electrode material.

[0007] Chinese patent CN113629233A discloses a method for preparing a P2-O3 composite phase lithium-rich manganese-based lithium-ion battery positive electrode material, the preparation method comprising: adding a compound of A and a compound of Mn to a solvent to obtain a salt solution, adding an O3 phase lithium-rich manganese-based oxide, mixing and dispersing the mixture to obtain a precursor suspension; drying the precursor suspension and then heat-treating the mixture to obtain a P2-O3 composite phase lithium-rich manganese-based material; Chinese patent CN117509752A discloses a sodium-ion battery positive electrode material, obtained by calcining a mixture of a copper-containing precursor and a sodium salt, wherein the molar ratio of sodium ions in the sodium salt to metal ions in the copper-containing precursor is 0.8-0.9:1; and / or the calcination treatment comprises: heating to 930-1100°C at a rate of 5°C / min-10°C / min, calcining for 4h-7h, then cooling to 800-910°C, and calcining for 10-15h.

[0008] Chinese patent CN116750806A discloses a method for preparing a positive electrode material for a sodium ion battery, the method comprising the following steps: (1) sintering a precursor material to obtain a pretreated material; the precursor material comprises a hydroxide precursor material; and (2) mixing and sintering a sodium source and the pretreated material of step (1) to obtain the positive electrode material for a sodium ion battery.

[0009] However, the high-temperature solid-phase sintering method currently used requires the addition of nickel-containing raw materials to its raw materials. The content of precious metals such as nickel added is relatively high, which increases the cost of the product. Summary of the Invention

[0010] 1. Problem to be solved

[0011] In response to the problems existing in the prior art, the present invention provides a high-entropy P2-O3 composite system sodium ion positive electrode material and a preparation method thereof, which is prepared by sintering a precursor, a metal oxide and sodium carbonate together, thereby reducing the content of precious metals such as nickel and lowering costs.

[0012] Another object of the present invention is to provide a high-entropy P2-O3 composite system sodium ion positive electrode material or a high-entropy P2-O3 composite system sodium ion positive electrode material obtained by a preparation method, which is applied to sodium batteries to improve the specific capacity and cycle stability of sodium batteries.

[0013] 2. Technical solution

[0014] In order to solve the above problems, the technical solutions adopted by the present invention are as follows:

[0015] The first aspect of the present invention provides a method for preparing a high-entropy P2-O3 composite system sodium ion positive electrode material, comprising the steps of: blending, sintering and cooling solid powders of a first reactant, a metal oxide and a sodium source, using a low-nickel, high-manganese precursor and a proportioning metal oxide method, which simplifies the preparation steps and effectively saves energy compared to the precursor method of the prior art; at the same time, a one-step sintering method is used to obtain the positive electrode material, and the positive electrode material particles have a spherical or spherical morphology, no obvious amorphous particles are observed on the surface of the spherical particles, and the particles are relatively uniform.

[0016] The first reactant is Ni y Fe z Mn 1-3y-z (OH) 2-4y , its particle size is 1-20 microns, preferably 1 micron, 2 microns, 3 microns, 4 microns, 5 microns, 6 microns, 7 microns, 8 microns, 9 microns, 10 microns, 11 microns, 12 microns, 13 microns, 14 microns, 15 microns, 16 microns, 17 microns, 18 microns, 19 microns, 20 microns; the metal oxide is any two of TiO2, MgO, Co3O4, SnO2, ZrO2, La2O3 and CeO2, and its particle size D50 is ≤ 5 microns; the sodium source is selected from any one of sodium carbonate and sodium bicarbonate, and its particle size D50 is ≤ 10 microns.

[0017] And it is satisfied that the particle size of the first reactant is larger than the particle size D50 of the metal oxide, and the particle size D50 of the sodium source is larger than the particle size D50 of the metal oxide.

[0018] According to any embodiment of the first aspect of the present invention, the specific steps are as follows:

[0019] The solid powder of the first reactant, the metal oxide and the sodium source is mixed in a high-speed mixer for 15-25 minutes, preferably 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes, 20 minutes, 21 minutes, 22 minutes, 23 minutes, 24 minutes, 25 minutes;

[0020] The mixed materials are sintered in air or oxygen atmosphere at a temperature of 700-1100°C, preferably, the temperature is 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C, 900°C, 910°C, 920°C, 930°C, 940°C, 950°C, 960°C, 970°C, 980°C, 990°C, 1000°C, 1010°C, 1020°C, 1030°C, 1040°C, 1050°C, 1060°C, 1070°C, 1080°C, 1090°C, or 1100°C.

[0021] The sintering time is 3-20 hours, preferably, the time is 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours;

[0022] Then cool naturally to room temperature.

[0023] According to any embodiment of the first aspect of the present invention, the sodium source is sodium carbonate, the purity of the sodium carbonate is greater than or equal to 99.5%, the chloride ion is less than 0.03%, and the particle size D50 is 6 microns ≤ 10 microns. Preferably, the particle size D50 is 6 microns, 7 microns, 8 microns, 9 microns, or 10 microns.

[0024] According to any embodiment of the first aspect of the present invention, the particle size of the first reactant is 5-20 microns, preferably, the particle size is 5 microns, 6 microns, 7 microns, 8 microns, 9 microns, 10 microns, 11 microns, 12 microns, 13 microns, 14 microns, 15 microns, 16 microns, 17 microns, 18 microns, 19 microns, or 20 microns.

[0025] According to any embodiment of the first aspect of the present invention, the metal oxide satisfies the following conditions: 2.5 μm ≤ particle size D50 ≤ 5 μm. Preferably, the particle size D50 is 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm.

[0026] According to any embodiment of the first aspect of the present invention, the sintering equipment is preferably a muffle furnace.

[0027] According to any embodiment of the first aspect of the present invention, the sintering is performed at a heating rate of 3° C. / min-5° C. / min.

[0028] By regulating the high and low temperature sintering procedures, the metal oxides can be homogeneously diffused during calcination, thereby preparing large single crystal particles of P2-O3 composite phase with uniform distribution of metal ions and stable structure of sodium ion battery positive electrode materials.

[0029] The second aspect of the present invention provides a high entropy P2-O3 composite system sodium ion positive electrode material according to the first aspect, whose molecular formula is Na x A y B y Ni y Fe z Mn 1-3y-z O2, a composite system consisting of a P2 phase and an O3 phase, wherein the elements A and B are any two of Ti, Mg, Co, Sn, Zr, La, and Ce; wherein: 0.66≤x≤1, 0.02≤y≤0.1, and 0.05≤z≤0.3.

[0030] It should be noted that the terms "P2-type structure", "P2-type phase" and "P2 phase" in the present invention are considered to be synonyms; similarly, the terms "O3-type structure", "O3-type phase" and "O3 phase" are considered to be synonyms.

[0031] The third aspect of the present invention provides a sodium battery, comprising the high-entropy P2-O3 composite system sodium ion positive electrode material obtained by the method described in the first aspect or the high-entropy P2-O3 composite system sodium ion positive electrode material described in the second aspect.

[0032] When the above-mentioned positive electrode material is applied to sodium ion batteries, the ultimate compaction degree of the sodium ion battery positive electrode material is effectively improved, which can effectively increase the upper limit voltage of the sodium ion battery, thereby effectively increasing the energy density of the sodium ion battery.

[0033] 3. Beneficial effects

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) The high entropy P2-O3 composite sodium ion positive electrode material of the present invention has the molecular formula Na x A Y B y Ni y Fe z Mn 1-3y-zO2 is prepared by sintering a mixture of precursors, metal oxides and sodium carbonate. It has good specific capacity and cycle stability, and reduces the content of precious metals such as nickel (reduced by at least 10%), thereby reducing costs. A and B are added elements, which are two of Ti, Mg, Co, Sn, Zr, La, and Ce; the sodium content is 0.66≤x≤1; nickel and the two added elements are equal in amount, with a content of 0.02≤y≤0.1, iron element is 0.05≤z≤0.3, and manganese element is 1-3y-z, realizing the addition of five layered oxide metal elements, and the contents of the three elements except Ni and Fe are uniform.

[0036] (2) The present invention gives full play to the advantages of high entropy materials by rationally designing the composition and structure of the materials, introduces a sodium content between 0.6 and 1.0, and constitutes a sodium cathode material of a P2-O3 composite phase. In addition, the invention utilizes a low-nickel and high-manganese precursor and a ratioed metal oxide method to effectively improve the indirectness and cheapness of material preparation. The cathode material prepared by this method has a high specific capacity and long cycle stability, which can achieve a significant improvement in the performance of sodium ion batteries and provide strong technical support for the large-scale application of sodium ion batteries.

[0037] (3) The present invention utilizes NiFeMn hydroxide supplemented with metal oxides and sodium carbonate for blending, which reduces the production cost of the product, avoids the complex preparation of multi-element hydroxide precursors, and improves the specific capacity and cycle stability of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that these drawings are designed for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless otherwise specified, these drawings are intended only to conceptually illustrate the structures described herein and are not necessarily drawn to scale.

[0039] Figure 1 This is the SEM image of the P2-O3 composite cathode material prepared by the present invention;

[0040] Figure 2 XRD pattern of the P2-O3 composite cathode material prepared in the present invention;

[0041] Figure 3 This is the cyclic discharge curve of Example 5 of the present invention.

[0042] Figure 4 This is the discharge voltage curve of Example 5 of the present invention. DETAILED DESCRIPTION

[0043] The present disclosure may be more readily understood by reference to the following description in conjunction with the accompanying drawings and examples, all of which constitute a part of this disclosure. It should be understood that the present disclosure is not limited to the specific products, methods, conditions, or parameters described and / or illustrated herein. Further, the terms used herein are for the purpose of describing specific embodiments by way of example only and are not intended to be limiting unless otherwise indicated.

[0044] It should also be understood that, for the sake of clarity, certain features of the present disclosure may be described herein in the context of separate embodiments, but may also be provided in combination with each other in a single embodiment. That is, unless clearly incompatible or specifically not included, each separate embodiment is considered to be combinable with any other embodiment, and the combination is considered to represent another different embodiment. Conversely, for the sake of simplicity, various features of the present disclosure described in the context of a single embodiment may also be provided individually or in any sub-combination. Finally, although a particular embodiment may be described as part of a series of steps or part of a more general structure, each step or sub-structure itself may also be considered to be an independent embodiment.

[0045] Unless otherwise indicated, it should be understood that each individual element in a list and each combination of individual elements in that list will be interpreted as a different embodiment. For example, a list of embodiments expressed as "A, B, or C" should be interpreted to include embodiments "A," "B," "C," "A or B," "A or C," "B or C," or "A, B, or C."

[0046] In this disclosure, the singular forms of the articles "a," "an," and "the" also include the corresponding plural reference, and a reference to a specific value includes at least that specific value unless the context clearly dictates otherwise. Thus, for example, a reference to "a substance" is a reference to at least one of that substance and equivalents thereof.

[0047] Terms including ordinal numbers such as "first" and "second" may be used to explain various components or fluids, but these components and fluids are not limited by these terms. Therefore, without departing from the teachings of the present disclosure, these terms are only used to distinguish the component / fluid from another component / fluid.

[0048] When items are described by using the conjunction terms "... and / or..." etc., the description should be understood to include any one and all combinations of one or more of the associated listed items.

[0049] In general, the use of the term "about" indicates an approximate value that can vary depending on the desired properties obtained by the disclosed subject matter and will be interpreted in a context-dependent manner based on function. Therefore, one of ordinary skill in the art will be able to interpret a certain degree of difference on a case-by-case basis. In some cases, the number of important figures used when expressing a particular value can be a representative technique for determining the difference allowed by the term "about". In other cases, a gradient in a range of values ​​can be used to determine the range of differences allowed by the term "about". Further, all ranges in this disclosure are inclusive and combinable, and reference to a value stated in a range includes every value within that range.

[0050] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs; and the terms used herein include any and all combinations of one or more of the associated listed items.

[0051]

X-ray diffraction analysis (XRD)

[0052] XRD spectra of the raw materials were collected using a PANalytical X'pert3 Discover diffractometer in the range of 10-80° with CuKa radiation (λ=1.54187), and Operando two-dimensional (2D)-XRD analysis was performed in the range of 2010-50° using a DectrisPILATUS1M detector.

[0053]

Transmission electron microscopy analysis

[0054] The present invention adopts scanning electron microscope (SEM) (Hitachi S4800) and energy dispersive spectrometer (EDSTECNAIG2 F30) to study the surface characteristics of the prepared material, and conducts qualitative analysis on the elements in the prepared material.

[0055]

Electrochemical characterization technology

[0056] Charge and discharge performance test

[0057] After standing for 8 hours, the assembled sodium batteries were subjected to constant current charge-discharge tests, rate tests, and long-cycle tests. The base materials and high-entropy materials were tested in two voltage ranges, between 2.0 and 4.25 V. Rate tests were conducted at 0.2C, 0.5C, 1C, 2C, 5C, and 10C using a CT2011A blue-ion battery tester.

[0058] Unless otherwise specified, the materials in the present invention are commercially available and can be purchased from the market. The types and particle sizes of the raw materials in the specific embodiments and comparative examples are as follows:

[0059]

[0060]

[0061] Example 1

[0062] Preparation of the first reactant: weigh Ni with a particle size of 5 microns 0.1 Fe 0.1 Mn 0.6 (OH) 1.6 As the first reactant.

[0063] Metal oxide selection: TiO2 and MgO were selected, and the particle size D50 was 3 microns.

[0064] Preparation of sodium carbonate: Sodium carbonate with a purity of 99.8%, a chloride ion content of 0.01%, and a particle size D50 of 8 microns was selected.

[0065] Mixing: Weigh and mix according to the molar ratio of Ni:Fe:Mn:Ti:Mg:Na=0.1:0.1:0.6:0.1:0.1:0.8, add to a high-speed mixer, and mix for 30 minutes.

[0066] Sintering: The mixed materials were placed in a muffle furnace and heated to 900°C at a heating rate of 5°C / min in an air atmosphere. The mixture was sintered for 10 hours and then naturally cooled to room temperature to obtain a high-entropy P2-O3 composite system sodium ion positive electrode material.

[0067] Performance Testing

[0068] Specific capacity test: At a rate of 0.1C, the initial discharge specific capacity is 150mAh / g. After 50 cycles, the discharge specific capacity remains at 140mAh / g.

[0069] Cycle stability test: At 1C rate, after 300 cycles, the capacity retention rate is 85%.

[0070] Example 2

[0071] Preparation of the first reactant: weigh Ni with a particle size of 10 microns 0.0667 Fe 0.3 Mn 0.5 (OH) 1.733 As the first reactant.

[0072] Selection of metal oxides: Co3O4 and SnO2, with particle size D50 of 4 microns.

[0073] Preparation of sodium carbonate: Sodium carbonate with a purity of 99.6%, a chloride ion content of 0.02%, and a particle size D50 of 6 microns was selected.

[0074] Mixing: Weigh and mix according to the molar ratio of Ni:Fe:Mn:Co:Sn:Na=0.0667:0.3:0.5:0.0667:0.0667:0.7, add to a high-speed mixer, and mix for 25 minutes.

[0075] Sintering: In an oxygen atmosphere, heat to 800°C at a heating rate of 3°C / min, sinter for 15 hours, and then cool naturally to room temperature to obtain a high-entropy P2-O3 composite system sodium ion positive electrode material.

[0076] Performance Testing

[0077] Specific capacity test: At a rate of 0.1C, the initial discharge specific capacity is 155mAh / g. After 50 cycles, the discharge specific capacity remains at 145mAh / g.

[0078] Cycle stability test: At 1C rate, after 300 cycles, the capacity retention rate is 88%.

[0079] Example 3

[0080] Preparation of the first reactant: weigh Ni with a particle size of 15 microns 0.033 Fe 0.3 Mn 0.6 (OH) 1.867 As the first reactant.

[0081] Selection of metal oxides: ZrO2 and La2O3, with particle size D50 of 2 microns.

[0082] Preparation of sodium carbonate: Sodium carbonate with a purity of 99.7%, a chloride ion content of 0.015%, and a particle size D50 of 9 microns was selected.

[0083] Mixing: Weigh and mix according to the molar ratio of Ni:Fe:Mn:Zr:La:Na=0.033:0.3:0.6:0.033:0.033:0.9, add to a high-speed mixer, and mix for 28 minutes.

[0084] Sintering: In an air atmosphere, heat to 1000°C at a heating rate of 4°C / min, sinter for 8 hours, and then cool naturally to room temperature to obtain a high-entropy P2-O3 composite system sodium ion positive electrode material.

[0085] Performance Testing

[0086] Specific capacity test: At a rate of 0.1C, the initial discharge specific capacity is 145mAh / g. After 50 cycles, the discharge specific capacity remains at 140mAh / g.

[0087] Cycle stability test: At 1C rate, after 300 cycles, the capacity retention rate is 86%.

[0088] Example 4

[0089] Preparation of the first reactant: weigh Ni with a particle size of 8 microns 0.0833 Fe 0.15 Mn 0.6 (OH) 1.667 As the first reactant.

[0090] Metal oxide selection: CeO2 and MgO are selected, and the particle size D50 is 3.5 microns.

[0091] Preparation of sodium carbonate: Sodium carbonate with a purity of 99.7%, a chloride ion content of 0.01%, and a particle size D50 of 7 microns was selected.

[0092] Mixing: Weigh and mix according to the molar ratio of Ni:Fe:Mn:Ce:Mg:Na=0.0833:0.15:0.6:0.0833:0.0833:0.85, add to a high-speed mixer, and mix for 32 minutes.

[0093] Sintering: In an air atmosphere, heat to 950°C at a heating rate of 4°C / min, sinter for 12 hours, and then cool naturally to room temperature to obtain a high-entropy P2-O3 composite system sodium ion positive electrode material.

[0094] Performance Testing

[0095] Specific capacity test: At a rate of 0.1C, the initial discharge specific capacity is 142mAh / g. After 50 cycles, the discharge specific capacity remains at 132mAh / g.

[0096] Cycle stability test: At 1C rate, after 300 cycles, the capacity retention rate is 87%.

[0097] Example 5

[0098] Preparation of the first reactant: Weigh Ni0.05Fe0.25M0.6(OH)1.8 with a particle size of 12 μm as the first reactant.

[0099] Metal oxide selection: TiO2 and Co3O4 are selected, and the particle size D50 is 4 microns.

[0100] Preparation of sodium carbonate: Sodium carbonate with a purity of 99.6%, a chloride ion content of 0.02%, and a particle size D50 of 8 microns was selected.

[0101] Mixing: Weigh and mix according to the molar ratio of Ni:Fe:Mn:Ti:Co:Na=0.05:0.25:0.6:0.05:0.05:0.8, add to a high-speed mixer, and mix for 28 minutes.

[0102] Sintering: In an oxygen atmosphere, heat to 850°C at a heating rate of 3°C / min, sinter for 18 hours, and then cool naturally to room temperature to obtain a high-entropy P2-O3 composite system sodium ion positive electrode material.

[0103] Performance Testing

[0104] like Figure 3 and Figure 4 As shown in the specific capacity test: at a rate of 0.1C, the initial discharge specific capacity is 142mAh / g. After 50 cycles, the discharge specific capacity remains at 133mAh / g.

[0105] Cycle stability test: At 1C rate, after 300 cycles, the capacity retention rate is 85%.

[0106] Example 6

[0107] Preparation of the first reactant: weigh Ni with a particle size of 6 microns 0.1 Fe 0.1 Mn 0.6 (OH) 1.6 As the first reactant.

[0108] Selection of metal oxides: SnO2 and ZrO2, with particle size D50 of 3 microns.

[0109] Preparation of sodium carbonate: Sodium carbonate with a purity of 99.8%, a chloride ion content of 0.01%, and a particle size D50 of 9 microns was selected.

[0110] Mixing: Weigh and mix according to the molar ratio of Ni:Fe:Mn:Sn:Zr:Na=0.1:0.1:0.6:0.1:0.1:0.9, add to a high-speed mixer, and mix for 30 minutes.

[0111] Sintering: In an air atmosphere, heat to 900°C at a heating rate of 5°C / min, sinter for 10 hours, and then cool naturally to room temperature to obtain a high-entropy P2-O3 composite system sodium ion positive electrode material.

[0112] Performance Testing

[0113] Specific capacity test: At a rate of 0.1C, the initial discharge specific capacity is 142mAh / g. After 50 cycles, the discharge specific capacity remains at 135mAh / g.

[0114] Cycle stability test: At 1C rate, after 300 cycles, the capacity retention rate is 89%.

[0115] Example 7

[0116] Preparation of the first reactant: weigh Ni with a particle size of 10 microns 0.05 Fe 0.3 Mn 0.5 (OH) 1.7 As the first reactant.

[0117] Selection of metal oxides: La2O3 and CeO2, with particle size D50 of 2.5 microns.

[0118] Preparation of sodium carbonate: Sodium carbonate with a purity of 99.7%, a chloride ion content of 0.015%, and a particle size D50 of 7 microns was selected.

[0119] Mixing: Weigh and mix according to the molar ratio of Ni:Fe:Mn:La:Ce:Na=0.05:0.3:0.5:0.05:0.05:0.85, add to the high-speed mixer, and mix for 26 minutes.

[0120] Sintering: In an oxygen atmosphere, heat to 800°C at a heating rate of 4°C / min, sinter for 14 hours, and then cool naturally to room temperature to obtain a high-entropy P2-O3 composite system sodium ion positive electrode material.

[0121] Performance Testing

[0122] Specific capacity test: At a rate of 0.1C, the initial discharge specific capacity is 146mAh / g. After 50 cycles, the discharge specific capacity remains at 135mAh / g.

[0123] Cycle stability test: At 1C rate, after 300 cycles, the capacity retention rate is 87%.

[0124] Example 8

[0125] Material preparation

[0126] Preparation of the first reactant: weigh Ni with a particle size of 14 microns 0.033 Fe 0.4 Mn 0.5 (OH) 1.867 As the first reactant.

[0127] Metal oxide selection: MgO and SnO2 are selected, and the particle size D50 is 3.5 microns.

[0128] Preparation of sodium carbonate: Sodium carbonate with a purity of 99.6%, a chloride ion content of 0.02%, and a particle size D50 of 6 microns was selected.

[0129] Mixing: Weigh and mix according to the molar ratio of Ni:Fe:Mn:Mg:Sn:Na=0.033:0.4:0.5:0.033:0.033:0.9, add to a high-speed mixer, and mix for 34 minutes.

[0130] Sintering: In an air atmosphere, heat to 950°C at a heating rate of 5°C / min, sinter for 12 hours, and then cool naturally to room temperature to obtain a high-entropy P2-O3 composite system sodium ion positive electrode material.

[0131] Performance Testing

[0132] Specific capacity test: At a rate of 0.1C, the initial discharge specific capacity is 144mAh / g. After 50 cycles, the discharge specific capacity remains at 134mAh / g.

[0133] Cycle stability test: At 1C rate, after 300 cycles, the capacity retention rate is 86%.

[0134] [Comparative Example 1] No metal oxide added

[0135] Comparative Example 1a( This comparative example corresponds to Example 5)

[0136] Preparation of the first reactant: Weigh Ni0.05Fe0.25M0.6(OH)1.8 with a particle size of 12 μm as the first reactant.

[0137] Preparation of sodium carbonate: Sodium carbonate with a purity of 99.6%, a chloride ion content of 0.02%, and a particle size D50 of 8 microns was selected.

[0138] Mixing: Only the first reactant and sodium carbonate were mixed in conventional proportions without adding metal oxides, added to a high-speed mixer, and mixed for 28 minutes.

[0139] Sintering: In an oxygen atmosphere, heat to 850°C at a heating rate of 3°C / min, sinter for 18 hours, and then cool naturally to room temperature to obtain a traditional sodium ion positive electrode material.

[0140] Performance Testing

[0141] Specific capacity test: At a rate of 0.1C, the initial discharge specific capacity is 130mAh / g. After 50 cycles, the discharge specific capacity drops to 115mAh / g.

[0142] Cycle stability test: At 1C rate, after 300 cycles, the capacity retention rate is 75%.

[0143] Comparative Example 1b( This comparative example corresponds to Example 5)

[0144] Preparation of the first reactant: weigh Ni with a particle size of 8 microns 0.0833 Fe 0.15 Mn 0.6 (OH) 1.667 As the first reactant.

[0145] Preparation of sodium carbonate: Sodium carbonate with a purity of 99.7%, a chloride ion content of 0.01%, and a particle size D50 of 7 microns was selected.

[0146] Mixing: Only the first reactant and sodium carbonate were mixed in conventional proportions without adding metal oxides, added to a high-speed mixer, and mixed for 32 minutes.

[0147] Sintering: In an air atmosphere, heat to 950°C at a heating rate of 4°C / min, sinter for 12 hours, and then cool naturally to room temperature to obtain a traditional sodium ion positive electrode material.

[0148] Performance Testing

[0149] Specific capacity test: At a rate of 0.1C, the initial discharge specific capacity was 128mAh / g. After 50 cycles, the discharge specific capacity dropped to 112mAh / g.

[0150] Cycle stability test: At 1C rate, after 300 cycles, the capacity retention rate is 72%.

[0151] Comparative Example 1c( This comparative example corresponds to Example 3)

[0152] Preparation of the first reactant: weigh Ni with a particle size of 15 microns 0.033 Fe 0.3 Mn 0.6 (OH) 1.867 As the first reactant.

[0153] Preparation of sodium carbonate: Sodium carbonate with a purity of 99.7%, a chloride ion content of 0.015%, and a particle size D50 of 9 microns was selected.

[0154] Mixing: Only the first reactant and sodium carbonate were mixed in conventional proportions without adding metal oxides, added to a high-speed mixer, and mixed for 248 minutes.

[0155] Sintering: In an air atmosphere, heat to 1000°C at a heating rate of 4°C / min, sinter for 8 hours, and then cool naturally to room temperature to obtain a traditional sodium ion positive electrode material.

[0156] Performance Testing

[0157] Specific capacity test: At a rate of 0.1C, the initial discharge specific capacity is 125mAh / g. After 50 cycles, the discharge specific capacity drops to 108mAh / g.

[0158] Cycle stability test: At 1C rate, after 300 cycles, the capacity retention rate is 70%.

[0159] [Comparative Example 2] No metal oxide added

[0160] Comparative Example 2a

[0161] Preparation of the first reactant: weigh Ni with a particle size of 12 microns 0.4 Fe 0.1 Mn 0.5 (OH)2 is used as the first reactant.

[0162] Preparation of sodium carbonate: Sodium carbonate with a purity of 99.5%, a chloride ion content of 0.025%, and a particle size D50 of 7 microns was selected.

[0163] Mixing: Only the first reactant and sodium carbonate are mixed in conventional proportions without adding metal oxides, put into a high-speed mixer, and mix for 20 minutes.

[0164] Sintering: In an air atmosphere, heat to 950°C at a heating rate of 5°C / min, sinter for 12 hours, and then naturally cool to room temperature to obtain a traditional sodium ion positive electrode material.

[0165] Performance Testing

[0166] Specific capacity test: At a rate of 0.1C, the initial discharge specific capacity was 131mAh / g. After 50 cycles, the discharge specific capacity dropped to 113mAh / g.

[0167] Cycle stability test: At 1C rate, after 300 cycles, the capacity retention rate is 76%.

[0168] Comparative Example 2b

[0169] Preparation of the first reactant: weigh Ni with a particle size of 8 microns0.3 Fe 0.2 Mn 0.5 (OH)2 is used as the first reactant.

[0170] Preparation of sodium carbonate: Sodium carbonate with a purity of 99.4%, a chloride ion content of 0.03%, and a particle size D50 of 10 microns was selected.

[0171] Mixing: Only the first reactant and sodium carbonate were mixed in conventional proportions without adding metal oxides, added to a high-speed mixer, and mixed for 22 minutes.

[0172] Sintering: In an air atmosphere, heat to 900°C at a heating rate of 6°C / min, sinter for 10 hours, and then cool naturally to room temperature to obtain a traditional sodium ion positive electrode material.

[0173] Performance Testing

[0174] Specific capacity test: At a rate of 0.1C, the initial discharge specific capacity was 127mAh / g. After 50 cycles, the discharge specific capacity dropped to 115mAh / g.

[0175] Cycle stability test: At 1C rate, after 300 cycles, the capacity retention rate is 71%.

[0176] Comparative Example 2c

[0177] Preparation of the first reactant: weigh Ni with a particle size of 15 microns 0.2 Fe 0.3 Mn 0.5 (OH)2 is used as the first reactant.

[0178] Preparation of sodium carbonate: Sodium carbonate with a purity of 99.3%, a chloride ion content of 0.04%, and a particle size D50 of 12 microns was selected.

[0179] Mixing: Only the first reactant and sodium carbonate were mixed in conventional proportions without adding metal oxides, added to a high-speed mixer, and mixed for 24 minutes.

[0180] Sintering: In an air atmosphere, heat to 850°C at a heating rate of 7°C / min, sinter for 15 hours, and then naturally cool to room temperature to obtain a traditional sodium ion positive electrode material.

[0181] Performance Testing

[0182] Specific capacity test: At a rate of 0.1C, the initial discharge specific capacity is 126mAh / g. After 50 cycles, the discharge specific capacity drops to 110mAh / g.

[0183] Cycle stability test: At 1C rate, after 300 cycles, the capacity retention rate is 74%.

[0184] By comparing the above Examples 1-8 and 6 groups of comparative examples, it can be seen that the high-entropy P2-O3 composite system sodium ion positive electrode material of the present invention is superior to traditional positive electrode materials in terms of specific capacity and cycle stability, verifying the innovation and practicality of the present invention.

Claims

1. A method for preparing a high entropy P2-O3 composite sodium ion positive electrode material, the molecular formula of which is Na x A y B y Ni y Fe z Mn 1-3y-z O2, a composite system consisting of a P2 phase and an O3 phase, wherein the elements A and B are any two of Ti, Mg, Co, Sn, Zr, La, and Ce; wherein: 0.66≤x≤1, 0.02≤y≤0.1, 0.05≤z≤0.3; characterized in that, The method comprises the steps of: blending a first reactant, a metal oxide and a solid powder of a sodium source, sintering and cooling, wherein the first reactant is composed of Ni y Fe z Mn 1-3y-z (OH) 2-4y , the particle size of which is 1-20 microns; The metal oxide is any two of TiO2, MgO, Co3O4, SnO2, ZrO2, La2O3 and CeO2, and its particle size D50 is ≤ 5 microns; The sodium source is selected from any one of sodium carbonate, sodium bicarbonate, sodium nitrate, and sodium acetate, with a particle size D50 ≤ 10 microns, and satisfies the following conditions: the particle size of the first reactant is greater than the particle size D50 of the metal oxide, and the particle size D50 of the sodium source is greater than the particle size D50 of the metal oxide.

2. The method for preparing a high entropy P2-O3 composite sodium ion positive electrode material according to claim 1, characterized in that: The specific steps are as follows: Mixing the solid powders of the first reactant, the metal oxide and the sodium source in a high-speed mixer for 15-25 minutes; The mixed materials are sintered in air or oxygen atmosphere at a temperature of 700-1100°C for 3-20 hours; Cool naturally to room temperature.

3. The method for preparing a high entropy P2-O3 composite sodium ion positive electrode material according to claim 1 or 2, characterized in that: The sodium source is sodium carbonate, and the purity of the sodium carbonate is greater than or equal to 99.5%, the chloride ion is less than 0.03%, and the particle size D50 is 6 microns≤≤10 microns.

4. The method for preparing a high entropy P2-O3 composite sodium ion positive electrode material according to claim 3, characterized in that: The particle size of the first reactant is 5-20 microns.

5. The method for preparing a high entropy P2-O3 composite sodium ion positive electrode material according to claim 4, characterized in that: The metal oxide satisfies the following conditions: 2.5 microns ≤ particle size D50 ≤ 5 microns.

6. The method for preparing a high entropy P2-O3 composite sodium ion positive electrode material according to claim 5, characterized in that: The sintering equipment is preferably a muffle furnace.

7. The method for preparing a high entropy P2-O3 composite sodium ion cathode material according to claim 6, characterized in that: The sintering is carried out at a heating rate of 3°C / min-5°C / min.

8. A high entropy P2-O3 composite sodium ion positive electrode material obtained by the method described in any one of 1-7, characterized in that: The sodium ion battery positive electrode material is a P2-O3 composite phase single crystal large particle.

9. A sodium battery, characterized in that: It includes a high-entropy P2-O3 composite system sodium ion positive electrode material obtained by the preparation method according to any one of claims 1 to 7, or a high-entropy P2-O3 composite system sodium ion positive electrode material according to claim 8.

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