A sodium zinc aluminum nickel manganese oxygen layer oxide, a method for preparing the same, and a sodium-ion battery

Abstract

The application provides a sodium zinc aluminum nickel manganese oxygen layered oxide shown as formula Na 0.70～ 0.72 Zn 0.05 Al 0.05 Ni 0.28 Mn 0.62 O2. The application further provides a preparation method of the sodium zinc aluminum nickel manganese oxygen layered oxide, comprising the following steps: S1) mixing raw materials according to a proportioning relationship and a chelating agent to obtain a mixed solution; S2) heating the mixed solution to form a gel; and S3) sintering the gel to obtain the sodium zinc aluminum nickel manganese oxygen layered oxide. The sodium zinc aluminum nickel manganese oxygen layered oxide provided by the application is used as a positive electrode material of a sodium ion battery, and high specific capacity, working voltage and excellent cycle stability are achieved. The sodium zinc aluminum nickel manganese oxygen layered oxide is used in the sodium ion battery, the battery has stable large-current cycle performance, has better electrochemical structure stability, has high practical application value, and can be used in portable electronic devices, energy storage power supplies and communication base stations and other energy storage equipment.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, and more particularly to a sodium zinc aluminum nickel manganese oxide layered oxide, its preparation method, and a sodium-ion battery. Background Technology

[0002] In recent years, due to the rapid development of portable electronic devices, electric vehicles, and hybrid vehicles, research on energy storage materials that are abundant in resources, highly energy-efficient, and environmentally friendly has become an international research hotspot. To meet the massive market demand, battery materials cannot be evaluated solely based on battery performance; battery safety, manufacturing costs, energy consumption, and environmental friendliness have also been incorporated as important indicators for evaluating battery materials. Currently, the development prospects of lithium-ion batteries are relatively bright. However, due to the uneven distribution of lithium resources and price constraints, excessive demand for lithium resources will inevitably lead to a shortage.

[0003] The development of sodium-ion batteries primarily aims to resolve the contradiction between the enormous demand for power batteries and the scarcity of lithium resources. Furthermore, lithium-ion batteries require the use of another rare metal besides lithium—cobalt; however, with the increasing market demand for power batteries, these scarce energy sources, lithium and cobalt, will inevitably face resource depletion and price increases. Sodium, as the second lightest alkali metal after lithium, has an abundance of 2.3%–2.8%, four to five orders of magnitude higher than lithium. When lithium resources face depletion, sodium-ion batteries hold the promise of replacing them.

[0004] Research on sodium-ion batteries began almost simultaneously with that of lithium-ion batteries, but with the successful commercialization of lithium-ion batteries, sodium-ion battery research gradually faded into the background. Furthermore, the lattice requirements for materials in sodium-ion batteries differ significantly from those in lithium-ion batteries, especially for cathode materials. This meant that attempts to directly apply materials successfully used in lithium-ion batteries to sodium-ion batteries almost always failed. In recent years, researchers have designed materials based on the unique characteristics of sodium-ion batteries, achieving many breakthroughs and making sodium-ion batteries a research hotspot once again.

[0005] Research on cathode materials is crucial for sodium-ion batteries. Cathode materials are not only a key factor in improving the performance of sodium-ion batteries, but also a major bottleneck limiting their cost. Finding cathode materials with high specific capacity, high operating voltage, stable structure, low cost, environmental friendliness, and good safety is of paramount importance.

[0006] Sodium-ion battery cathode materials can be mainly classified into three types according to their crystal structure: layered materials, polyanionic materials, and Prussian blue materials. Among them, layered materials have attracted much attention due to their high electronic conductivity and stable layered structure. The general formula for layered oxide cathode materials is Na. xTMO2 (TM stands for transition metal) was classified into different structures, such as O3, O2, P3, and P2, by Delmas et al. in 1980 based on the coordination configuration of sodium ions and the stacking mode of oxygen in the MO6 polyhedron. The uppercase letters represent the coordination configuration of sodium ions, and the numbers represent the number of stacking layers with the fewest repeating oxygen units. Due to these structural differences, the electrochemical properties of the corresponding materials also vary significantly. P2-type materials have wider sodium ion transport channels and lower sodium ion migration barriers, exhibiting faster diffusion kinetics, but their initial capacity is lower, and they are prone to phase transition between the P2 and O2 phases under high pressure, thus affecting cycle stability. Compared to P2-type materials, O3-type materials have a higher sodium ion content, resulting in a higher initial capacity, but their rate performance and capacity retention are poorer.

[0007] To address the series of problems associated with the aforementioned layered oxide materials, researchers have developed various modification methods. By designing and optimizing the material composition, structure, and surface, they aim to improve the specific capacity, enhance the structural stability and air stability of the materials, and thus explore the application value of layered oxide cathodes.

[0008] Sodium ion layered oxide cathode material (Na x TMO2, as a homologue of lithium-ion layered materials (such as LiCoO2), has attracted widespread attention and research due to its advantages such as high energy density, low cost, and simple synthesis. However, the large Na... + The radius and strong interlayer electrostatic repulsion lead to Na x TMO2 undergoes complex structural transformations during charge and discharge, further affecting its electrochemical performance. On the other hand, the energy density of layered cathodes is limited by the content of variable-valence transition metal ions. To obtain higher energy densities, layered oxide cathodes typically need to be charged to a high-voltage region to activate the oxygen ion redox reaction (>4.0V vs. Na). + Layered cathodes (Na) achieve higher discharge specific capacity by releasing more sodium ions. However, in the high-voltage region, layered cathodes undergo severe phase transitions and irreversible anionic redox reactions, ultimately leading to electrochemical performance degradation and structural collapse. To address these issues, the design of rational high-voltage layered materials to obtain high-energy-density batteries is currently a key research focus. Summary of the Invention

[0009] The technical problem solved by this invention is a Na 0.70～0.72 Zn 0.05 Al 0.05 Ni 0.28 Mn 0.62The sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide shown in O2 has a stable electrochemical structure. As a positive electrode material for sodium-ion batteries, it exhibits stable high-current cycling performance and good rate performance.

[0010] In view of this, this application provides a sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide as shown in formula (I).

[0011] Na 0.70～0.72 Zn 0.05 Al 0.05 Ni 0.28 Mn 0.62 O2 (Ⅰ).

[0012] Preferably, the layered oxide is composed of several layers of composite oxide and sodium atoms, with the sodium atoms distributed between two layers of composite oxide; oxygen is bonded to zinc, aluminum, manganese, and nickel in the composite oxide, and oxygen atoms are distributed on the surface of the zinc, aluminum, manganese, and nickel.

[0013] Preferably, the size of the layered oxide is 3 to 5 μm.

[0014] This application also provides a method for preparing the aforementioned sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide, comprising the following steps:

[0015] S1) Sodium source compound, zinc source compound, aluminum source compound, manganese source compound, and nickel source compound are mixed with a chelating agent according to the ratio to obtain a mixed solution;

[0016] S2) Heat the mixed solution until a gel is formed;

[0017] S3) The gel is sintered sequentially at 100-200℃, 400-600℃ and ≥950℃ to obtain sodium zinc aluminum nickel manganese oxide layered oxide.

[0018] Preferably, the sodium source compound is selected from at least one of sodium nitrate and sodium acetate; the zinc source compound is selected from at least one of zinc nitrate and zinc acetate; the aluminum source compound is selected from aluminum nitrate; the manganese source compound is selected from at least one of manganese nitrate and manganese acetate; the nickel source compound is selected from at least one of nickel nitrate and nickel acetate; and the chelating agent is selected from citric acid monohydrate.

[0019] Preferably, the molar ratio of the sodium source compound, zinc source compound, aluminum source compound, nickel source compound, manganese source compound to the chelating agent is (0.72-0.75):0.05:0.05:0.28:0.62:2.26.

[0020] Preferably, the sintering temperatures are 130–180°C, 420–480°C, and 950–1100°C, respectively; and the sintering times are 5–10 h, 5–10 h, or 10–15 h, respectively.

[0021] This application also provides a sodium-ion battery, including a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode is the sodium zinc aluminum nickel manganese oxide layered oxide described above or the sodium zinc aluminum nickel manganese oxide layered oxide prepared by the preparation method described above.

[0022] Preferably, the negative electrode material is one or both of metallic sodium and hard carbon, and the electrolyte is one of the following: a mixture of ethylene carbonate, propylene carbonate and 5% fluoroethylene carbonate in a volume ratio of 1:1; ethylene carbonate in a volume ratio of 1:1:1; a mixture of propylene carbonate, fluoroethylene carbonate and 5% fluoroethylene carbonate in a volume ratio of 1:1:1; or a mixture of propylene carbonate and fluoroethylene carbonate in a volume ratio of (95:5) to (98:2).

[0023] Preferably, the sodium-ion battery is a pouch battery or a button battery.

[0024] This application provides a sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide with the molecular formula Na. 0.70～ 0.72 Zn 0.05 Al 0.05 Ni 0.28 Mn 0.62 O2 is a P2 pure-phase sodium ion layered oxide. By simultaneously introducing metal elements Zn, Al, Ni and Mn, it forms bonds with O. Sodium atoms are distributed between the composite oxide layers formed by the above metal elements and oxygen elements, which is beneficial to improving the structural stability of sodium zinc aluminum nickel manganese oxygen layered oxide. At the same time, the layered oxide provided in this application has stable high-current cycling performance and good rate performance as a positive electrode material for sodium-ion batteries. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide cathode material of the present invention;

[0026] Figure 2 Aberration-corrected electron microscope image of the zinc-aluminum-nickel-manganese-oxygen layered oxide cathode material prepared in Example 1 of this invention;

[0027] Figure 3 XRD pattern of the sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide cathode material for sodium-ion batteries in Example 1 of this invention;

[0028] Figure 4 The sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide cathode material for the sodium-ion battery in Example 1 of this invention is at 10 mAg -1First-cycle charge-discharge curves at current density;

[0029] Figure 5 The sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide cathode material for the sodium-ion battery in Example 1 of this invention is used at 100 mAg. -1 Cyclic performance at current density;

[0030] Figure 6 This is a rate performance diagram of the sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide cathode material for sodium-ion batteries in Example 1 of the present invention.

[0031] Figure 7 XRD pattern of the sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide cathode material for sodium-ion batteries in Example 2 of this invention;

[0032] Figure 8 The sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide cathode material for the sodium-ion battery in Example 2 of this invention is at 10 mAg. -1 First-cycle charge-discharge curves at current density;

[0033] Figure 9 The sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide cathode material for the sodium-ion battery in Example 2 of this invention is at 100 mAg. -1 Cyclic performance at current density;

[0034] Figure 10 XRD pattern of the sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide cathode material for sodium-ion batteries in Example 3 of this invention;

[0035] Figure 11 The sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide cathode material for the sodium-ion battery in Example 3 of this invention is at 10 mAg -1 First-cycle charge-discharge curves at current density;

[0036] Figure 12 The sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide cathode material for the sodium-ion battery in Example 3 of this invention is at 100 mAg. -1 Cyclic performance at current density;

[0037] Figure 13 The sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide cathode material in Example 4 of this invention has a 1000 mAg content in a sodium-ion full cell. -1 Cyclic performance at current density;

[0038] Figure 14 XRD of the sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide cathode material for sodium-ion batteries prepared in Comparative Example 1;

[0039] Figure 15 XRD pattern of sodium zinc aluminum nickel manganese oxide layered oxide cathode material for sodium-ion batteries prepared for Comparative Example 2. Detailed Implementation

[0040] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0041] Given the poor structural stability of sodium-nickel-manganese-oxygen layered oxides in existing technologies and the need for improved performance as cathode materials, this application provides a sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide. By introducing different proportions of sodium, zinc, aluminum, nickel, and manganese to form a pure-phase layered structure, the structural stability of the nickel-zinc-aluminum-nickel-manganese-oxygen layered oxide is improved. Furthermore, as a cathode material for sodium-ion batteries, it enables sodium-ion batteries to exhibit better cycle performance and rate capability. Specifically, this invention discloses a sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide as shown in formula (Ⅰ).

[0042] Na 0.70～0.72 Zn 0.05 Al 0.05 Ni 0.28 Mn 0.62 O2 (Ⅰ).

[0043] The structural schematic diagram of the sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide of this application is shown below. Figure 1 As shown, specifically: the layered oxide is composed of several layers of composite oxide and sodium atoms, wherein the sodium atoms are distributed between two layers of composite oxide; oxygen and zinc, aluminum, manganese and nickel are bonded in the composite oxide, and oxygen atoms are distributed on the surface of zinc, aluminum, manganese and nickel.

[0044] In the sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide provided in this application, zinc atoms, aluminum atoms, manganese atoms, and nickel atoms are bonded to oxygen atoms, and oxygen atoms are formed on the surface of the aforementioned atoms, thereby forming a composite oxide composed of zinc, aluminum, nickel, manganese, and oxygen. Multiple sodium atoms are distributed between two layers of the composite oxide. Repeating this structural composition yields the sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide. Specifically, the molecular formula of the sodium-zinc-aluminum-nickel-manganese layered oxide is Na. 0.70 Zn 0.05 Al 0.05 Ni 0.28 Mn 0.62 O2, Na 0.71 Zn 0.05 Al 0.05 Ni 0.28 Mn 0.62 O2, Na 0.72 Zn 0.05 Al 0.05 Ni 0.28 Mn 0.62 O2.

[0045] The sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide described in this application has a size of 3–5 μm.

[0046] This application also provides a method for preparing sodium zinc aluminum nickel manganese oxide layered oxides, comprising the following steps:

[0047] S1) Sodium source compound, zinc source compound, aluminum source compound, manganese source compound, and nickel source compound are mixed with a chelating agent according to the ratio to obtain a mixed solution;

[0048] S2) Heat the mixed solution until a gel is formed;

[0049] S3) The gel is sintered sequentially at 100-200℃, 400-600℃ and ≥950℃ to obtain sodium zinc aluminum nickel manganese oxide layered oxide.

[0050] In the preparation of sodium-zinc-aluminum-nickel-manganese oxide layered oxides, sodium source compound, zinc source compound, aluminum source compound, manganese source compound, and nickel source compound are first mixed with a chelating agent according to a certain ratio to obtain a mixed solution. In this process, the sodium source compound, zinc source compound, aluminum source compound, manganese source compound, and nickel source compound are choices well-known to those skilled in the art. For example, the sodium source compound is selected from at least one of sodium nitrate and sodium acetate; the zinc source compound is selected from at least one of zinc nitrate and zinc acetate; the aluminum source compound is selected from aluminum nitrate; the manganese source compound is selected from at least one of manganese nitrate and manganese acetate; and the nickel source compound is selected from at least one of nickel nitrate and nickel acetate. Further, the sodium source compound is selected from sodium acetate, the zinc source compound from zinc acetate, the manganese source compound from manganese acetate, and the nickel source compound from nickel acetate. The chelating agent can specifically be citric acid monohydrate. The molar ratio of the sodium source compound, zinc source compound, aluminum source compound, nickel source compound, manganese source compound, and chelating agent is (0.72–0.75):0.05:0.05:0.28:0.62:2.26; specifically, the molar ratio of the sodium source compound, zinc source compound, aluminum source compound, nickel source compound, manganese source compound, and chelating agent is 0.72:0.05:0.05:0.28:0.62:2.26. The molar ratios are 0.73:0.05:0.05:0.28:0.62:2.26, 0.74:0.05:0.05:0.28:0.62:2.26, or 0.75:0.05:0.05:0.28:0.62:2.26. If the sodium, zinc, aluminum, nickel, and manganese source compounds are not within the above molar ranges, a pure-phase sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide cannot be formed. The mixing is preferably carried out in a glove box, where the water and oxygen contents are both below 0.1 ppm.

[0051] The present application then heats the above mixed solution until a gel is formed; the heating is preferably carried out in a water bath environment with a temperature of 50-100°C, specifically, the temperature of the water bath environment is 60-80°C.

[0052] According to the present invention, the gel is sintered sequentially at 100–200°C, 400–600°C, and ≥950°C to obtain a sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide. The sintering is carried out in stages: the sintering at 100–200°C removes moisture from the gel; the sintering at 400–600°C removes carbon from the gel; and the sintering at ≥950°C forms a pure-phase layered oxide. Specifically, the sintering temperatures are sequentially 130–180°C, 420–480°C, and 950–1100°C; the sintering times are 5–10 h, 5–10 h, or 10–15 h, respectively. For example, the sintering temperatures are sequentially 150°C, 500°C, and 950°C, and the corresponding sintering times are 6 h, 6 h, or 12 h, respectively.

[0053] This application also provides a sodium-ion battery, including a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode is the sodium zinc aluminum nickel manganese oxide layered oxide described in the above-described scheme.

[0054] In the sodium-ion battery, both the negative electrode and the electrolyte can be of types well known to those skilled in the art, and this application does not impose any particular restrictions. In specific embodiments, the negative electrode material is one or both of metallic sodium and hard carbon, and the electrolyte is one of the following: a mixture of ethylene carbonate, propylene carbonate, and 5% fluoroethylene carbonate in a volume ratio of 1:1; ethylene carbonate in a volume ratio of 1:1:1; a mixture of propylene carbonate, fluoroethylene carbonate, and 5% fluoroethylene carbonate in a volume ratio of (95:5) to (98:2); where 5% fluoroethylene carbonate represents the volume percentage of fluoroethylene carbonate in the mixture. The type of sodium-ion battery is not particularly limited; it can be a pouch battery or a button battery, and this application does not impose any particular restrictions.

[0055] To further understand the present invention, the following detailed description, in conjunction with embodiments, provides the sodium zinc aluminum nickel manganese oxide layered oxide provided by the present invention, its preparation method, and its application. The scope of protection of the present invention is not limited by the following embodiments.

[0056] Example 1

[0057] 13.56 mmol citric acid monohydrate, 4.39 mmol sodium acetate, 1.7 mmol nickel acetate, 3.7 mmol manganese acetate, 0.3 mmol zinc acetate, and 0.3 mmol aluminum nitrate were dissolved in 25 ml of deionized water and stirred until homogeneous to form solution A. Solution A was stirred in a 70°C water bath until it evaporated to dryness and formed gel A. Gel A was then ground and sintered sequentially at 150°C, 500°C, and 950°C for 360 min, 360 min, and 720 min, respectively, to obtain the final powder, which is Na. 0.70 Zn 0.05 Al 0.05 Ni 0.28 Mn 0.62 O2 sodium zinc aluminum nickel manganese oxygen layered oxides.

[0058] Figure 2 The image shows a spherical aberration electron microscope image of the finished powder prepared in this embodiment. As can be seen from the image, the metal atoms in the finished powder prepared in this embodiment are distributed in layers.

[0059] Figure 3 The image shows the XRD pattern of the finished powder prepared in this embodiment. As can be seen from the image, the product prepared in this embodiment is a pure phase P2 sodium ion layered oxide.

[0060] Preparation of the positive electrode: The sodium zinc aluminum nickel manganese oxide layered oxide, conductive carbon black, and binder polyvinylidene fluoride prepared in Example 1 were mixed at a mass ratio of 7:2:1, wherein the polyvinylidene fluoride was dissolved in NMP with a mass fraction of 5%. After uniform mixing, the mixture was coated onto carbon-coated aluminum foil using a scraper, with a film thickness of 150 micrometers. The film was then vacuum dried at 120°C for 10 hours to prepare an electrode sheet with a diameter of 10 mm. The active material loaded on the electrode sheet was 2 mg / cm³. -2 ;

[0061] Battery assembly: In a glove box protected by argon atmosphere, a button cell with model number CR2032 is assembled using a sodium metal sheet as the negative electrode, Whatman glass fiber as the separator, 1 mol / L sodium perchlorate as the solute, and a mixture of propylene carbonate (PC) and fluoroethylene carbonate (FEC) in a volume ratio of 95:5 as the solvent.

[0062] Battery testing: The assembled battery is placed at room temperature for testing, with a test voltage range of 2.5-4.3V.

[0063] The batteries obtained above were tested, and the specific results are as follows:

[0064] like Figure 4 As shown, Figure 4 The figure shows the first charge-discharge curve of the sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide cathode material synthesized in Example 1; as can be seen from the figure, at 10 mA g-1 The initial discharge specific capacity at the current density is 127.3 mAh g. -1 The initial Coulomb efficiency was 90.0%.

[0065] like Figure 5 As shown, Figure 5 The sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide cathode material synthesized in Example 1 was tested at 100 mAg. -1 Cyclic performance at current density, by Figure 5 It can be seen that at 100mA g -1 The discharge specific capacity after 100 cycles at current density increased from 113.3 mAh g. -1 Up to 100.1mAh g -1 The capacity retention rate was 88.5%.

[0066] like Figure 6 As shown, Figure 6 The figure shows the rate performance of the sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide cathode material synthesized in Example 1. As can be seen from the figure, the rate performance at 50 mA g... -1 The discharge specific capacity at the current density is 115.6 mAh g. -1 100mA g -1 The discharge specific capacity at the current density is 110.5 mAh g. -1 200mA g -1 The discharge specific capacity at the current density is 104.0 mAh g. -1 300mA g -1 The discharge specific capacity at the current density is 99.5 mAh g. -1 500mA g -1 The discharge specific capacity at the current density is 92.7 mAh g. -1 800mA g -1 The discharge specific capacity at the current density is 84.3 mAh g. -1 1000mA g -1 The discharge specific capacity at the current density is 79.4 mAh g. -1 1500mA g -1 The discharge specific capacity at the current density is 72.5 mAh g. -1 2000mA g -1 The discharge specific capacity at the current density is 64.3 mAh g. -1 .

[0067] Example 2

[0068] 13.56 mmol citric acid monohydrate, 4.43 mmol sodium acetate, 1.7 mmol nickel acetate, 3.7 mmol manganese acetate, 0.3 mmol zinc acetate, and 0.3 mmol aluminum nitrate were dissolved in 25 ml of deionized water and stirred until homogeneous to form solution A. Solution A was stirred in a 70°C water bath until it evaporated to dryness and formed gel A. Gel A was then ground and sintered sequentially at 150°C, 500°C, and 950°C for 360 min, 360 min, and 720 min, respectively, to obtain the final powder, which is Na. 0.71 Zn 0.05 Al 0.05 Ni 0.28 Mn 0.62 O2 sodium zinc aluminum nickel manganese oxygen layered oxides.

[0069] The obtained product, as determined by XRD analysis, is a pure-phase P2 layered oxide cathode material, such as... Figure 7 As shown.

[0070] Preparation of the positive electrode: The sodium zinc aluminum nickel manganese oxide layered oxide prepared in Example 2, conductive carbon black, and binder polyvinylidene fluoride were mixed at a mass ratio of 7:2:1, wherein the polyvinylidene fluoride was dissolved in NMP with a mass fraction of 5%. After uniform mixing, the mixture was coated onto carbon-coated aluminum foil using a scraper, with a film thickness of 150 micrometers. The film was then vacuum-dried at 120°C for 10 hours to produce an electrode sheet with a diameter of 10 mm. The active material loaded on the electrode sheet was 2 mg / cm³. -2 ;

[0071] Battery assembly: In a glove box protected by argon atmosphere, a button cell with model number CR2032 is assembled using a sodium metal sheet as the negative electrode, Whatman glass fiber as the separator, 1 mol / L sodium perchlorate as the solute, and a mixture of propylene carbonate (PC) and fluoroethylene carbonate (FEC) in a volume ratio of 95:5 as the solvent.

[0072] Battery testing: The assembled battery is placed at room temperature for testing, with a test voltage range of 2.5-4.3V.

[0073] The batteries obtained above were tested, and the specific results are as follows:

[0074] like Figure 8 As shown, Figure 8 The figure shows the first charge-discharge curve of the sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide cathode material synthesized in Example 2. As can be seen from the figure, at 10 mA g... -1 The initial discharge specific capacity at the current density is 127.9 mAh g. -1 The initial Coulomb efficiency was 94.2%.

[0075] like Figure 9 As shown, Figure 9 The sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide cathode material synthesized in Example 2 was tested at 100 mAg. -1 The cycling performance at current density is shown in the figure at 100 mAg. -1 The discharge specific capacity after 100 cycles at current density increased from 112.4 mAh g. -1 Up to 102.5mAh g -1 The capacity retention rate was 91.2%.

[0076] Example 3

[0077] 13.56 mmol citric acid monohydrate, 4.47 mmol sodium acetate, 1.7 mmol nickel acetate, 3.7 mmol manganese acetate, 0.3 mmol zinc acetate, and 0.3 mmol aluminum nitrate were dissolved in 25 ml of deionized water and stirred until homogeneous to form solution A. Solution A was stirred in a 70°C water bath until it evaporated to dryness and formed gel A. Gel A was then ground and sintered sequentially at 150°C, 500°C, and 950°C for 360 min, 360 min, and 720 min, respectively, to obtain the final powder, which is Na. 0.72 Zn 0.05 Al 0.05 Ni 0.28 Mn 0.62 O2 sodium zinc aluminum nickel manganese oxygen layered oxides.

[0078] The obtained product, as determined by XRD analysis, is a pure-phase P2 layered oxide cathode material, such as... Figure 10 As shown.

[0079] Preparation of the positive electrode: The sodium zinc aluminum nickel manganese oxide layered oxide, conductive carbon black, and binder polyvinylidene fluoride prepared in Example 3 were mixed at a mass ratio of 7:2:1, wherein the polyvinylidene fluoride was dissolved in NMP with a mass fraction of 5%. After uniform mixing, the mixture was coated onto carbon-coated aluminum foil with a film thickness of 150 micrometers. The film was then vacuum dried at 120°C for 10 hours to form an electrode sheet with a diameter of 10 mm. The active material loaded on the electrode sheet was 2 mg / cm³. -2 ;

[0080] Battery assembly: In a glove box protected by argon atmosphere, a button cell with model number CR2032 is assembled using a sodium metal sheet as the negative electrode, Whatman glass fiber as the separator, 1 mol / L sodium perchlorate as the solute, and a mixture of propylene carbonate (PC) and fluoroethylene carbonate (FEC) in a volume ratio of 95:5 as the solvent.

[0081] Battery testing: The assembled battery is placed at room temperature for testing, with a test voltage range of 2.5-4.3V.

[0082] The batteries obtained above were tested, and the specific results are as follows:

[0083] like Figure 11 As shown, Figure 11 The figure shows the first charge-discharge curve of the sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide cathode material synthesized in Example 3. As can be seen from the figure, at 10 mA g... -1 The initial discharge specific capacity at the current density is 127.1 mAh g. -1 The initial Coulomb efficiency was 94.6%.

[0084] like Figure 12 As shown, Figure 12 The sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide cathode material synthesized in Example 3 was tested at 100 mAg. -1 The cycling performance at current density is shown in the figure. At 100 mA g -1 The discharge specific capacity after 300 cycles at current density increased from 111.4 mAh g. -1 Up to 100.0mAh g -1 The capacity retention rate was 90.0%.

[0085] Example 4

[0086] 13.56 mmol citric acid monohydrate, 4.52 mmol sodium acetate, 1.7 mmol nickel acetate, 3.7 mmol manganese acetate, 0.3 mmol zinc acetate, and 0.3 mmol aluminum nitrate were dissolved in 25 ml of deionized water and stirred until homogeneous to form solution A. Solution A was stirred in a 70°C water bath until it evaporated to dryness and formed gel A. Gel A was then ground and sintered sequentially at 150°C, 500°C, and 950°C for 360 min, 360 min, and 720 min, respectively, to obtain the final powder, which is Na. 0.72 Zn 0.05 Al 0.05 Ni 0.28 Mn 0.62 O2 sodium zinc aluminum nickel manganese oxygen layered oxides.

[0087] The layered oxide prepared above was used as the positive electrode material and matched with hard carbon negative electrode material in a coin cell to form a full cell. Its performance was tested, and the results are as follows:

[0088] like Figure 13 As shown, Figure 13 The figure shows the cycle performance of the sodium zinc aluminum nickel manganese oxide layered oxide cathode material synthesized in Example 4 in a pouch cell at a 2C rate. As can be seen from the figure, the discharge capacity increased from 1.14 Ah to 1.01 Ah after 100 cycles at a 2C rate, with a capacity retention rate of 88.6%.

[0089] Comparative Example 1

[0090] The preparation method is the same as in Example 1, except that the amount of aluminum nitrate added is 1.8 mmol.

[0091] The obtained product was tested by XRD as follows: Figure 14 As shown in the figure, the oxide prepared in this comparative example is not a pure phase structure.

[0092] Comparative Example 2

[0093] The preparation method is the same as in Example 1, except that the sintering temperature in the last step is 900°C.

[0094] The obtained product was tested by XRD as follows: Figure 15 As shown in the figure, the oxide prepared in this comparative example is not a pure phase structure.

[0095] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0096] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide cathode material as shown in Formula (Ⅰ), On 0.70~0.72 Zn 0.05 Al 0.05 Ni 0.28 Mn 0.62 O2 (Ⅰ); The layered oxide is composed of several layers of composite oxide and sodium atoms, with the sodium atoms distributed between two layers of composite oxide; oxygen is bonded to zinc, aluminum, manganese, and nickel in the composite oxide, and oxygen atoms are distributed on the surface of zinc, aluminum, manganese, and nickel. The preparation method of the sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide cathode material includes the following steps: S1) Sodium source compound, zinc source compound, aluminum source compound, manganese source compound, and nickel source compound are mixed with a chelating agent according to the ratio to obtain a mixed solution; S2) Heat the mixed solution until a gel is formed; S3) The gel is sintered sequentially at 100~200℃, 400~600℃ and ≥950℃ to obtain sodium zinc aluminum nickel manganese oxide layered oxide.

2. The cathode material according to claim 1, characterized in that, The layered oxide has a size of 3~5 μm.

3. The preparation method of the sodium-zinc-aluminum-nickel-manganese-oxygen layered oxide cathode material according to claim 1, comprising the following steps: S1) Sodium source compound, zinc source compound, aluminum source compound, manganese source compound, and nickel source compound are mixed with a chelating agent according to the ratio to obtain a mixed solution; S2) Heat the mixed solution until a gel is formed; S3) The gel is sintered sequentially at 100~200℃, 400~600℃ and ≥950℃ to obtain sodium zinc aluminum nickel manganese oxide layered oxide.

4. The preparation method according to claim 3, characterized in that, The sodium source compound is selected from at least one of sodium nitrate and sodium acetate; the zinc source compound is selected from at least one of zinc nitrate and zinc acetate; the aluminum source compound is selected from aluminum nitrate; the manganese source compound is selected from at least one of manganese nitrate and manganese acetate; the nickel source compound is selected from at least one of nickel nitrate and nickel acetate; and the chelating agent is selected from citric acid monohydrate.

5. The preparation method according to claim 3, characterized in that, The molar ratio of the sodium source compound, zinc source compound, aluminum source compound, nickel source compound, manganese source compound to the chelating agent is (0.72~0.75): 0.05：0.05：0.28：0.62：2.26。 6. The preparation method according to claim 3, characterized in that, The sintering temperature is 130~180℃ and the time is 5~10h; the sintering temperature is 420~480℃ and the time is 5~10h; the sintering temperature is 950~1100℃ and the time is 10~15h.

7. A sodium-ion battery, comprising a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode comprises the sodium zinc aluminum nickel manganese oxide layered oxide positive electrode material according to any one of claims 1 to 2 or the sodium zinc aluminum nickel manganese oxide layered oxide positive electrode material prepared by the preparation method according to any one of claims 3 to 6.

8. The sodium-ion battery according to claim 7, characterized in that, The negative electrode material is one or both of metallic sodium and hard carbon, and the electrolyte is a mixture of ethylene carbonate, propylene carbonate and 5% fluoroethylene carbonate in a volume ratio of 1:1 or a mixture of propylene carbonate and fluoroethylene carbonate in a volume ratio of (95:5) to (98:2).

9. The sodium-ion battery according to claim 7, characterized in that, The sodium-ion battery is either a pouch battery or a button battery.

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