CN120978060A

CN120978060A - A high-capacity sodium-ion battery cathode material, its preparation method and application

Info

Publication number: CN120978060A
Application number: CN202510673125.9A
Authority: CN
Inventors: 冯丽华; 周晓崇; 徐雪松; 孙褚俊; 田子启; 查惟伟
Original assignee: Zhejiang Chaona New Energy Materials Co ltd
Current assignee: Zhejiang Chaona New Energy Materials Co ltd
Priority date: 2025-05-23
Filing date: 2025-05-23
Publication date: 2025-11-18

Abstract

This invention discloses a high-capacity sodium-ion battery cathode material, its preparation method, and its application, relating to the field of sodium-ion battery technology. The material has the molecular formula Na _x Ni _y _ Fez _M _ mMnnO _2 , where x ≥ 0.8, 0.1 ≤ y ≤ 0.2, y + z = 0.6, m ≤ 0.1 and m + n = 0.4, and M represents a divalent transition metal element. This invention utilizes a divalent transition metal element to replace high-valent manganese, which is beneficial for increasing the bulk sodium content, reducing the Mn ³⁺ content, minimizing the Jan Taylor effect, and improving cycle performance. It also helps adjust the transition metal element composition in the layered oxide, deeply activating the oxidation-reduction of nickel during charge and discharge, and improving reversible capacity. Furthermore, the use of low-nickel, high-iron, and high-manganese elements as the main elements helps reduce material costs. The preparation process employs a wet vacuum mixing followed by pressing and sintering process to improve the crystallinity and purity of the material, forming large-size single crystals.

Description

High-capacity sodium ion battery positive electrode material and preparation method and application thereof

Technical Field

The invention relates to the technical field of lithium ion batteries, in particular to a high-capacity sodium ion battery anode material and a preparation method and application thereof.

Background

The lithium battery technology is broken through continuously, and the proportion of lithium batteries in the global electrochemical energy storage is as high as 86%. However, lithium is used as a core raw material of lithium batteries, but the lithium resource reserves are limited, and the development of sodium electricity with abundant raw material reserves is an important strategic choice in face of double challenges of lithium resource shortage and supply chain safety. The development of sodium batteries becomes an important technical reserve for coping with lithium resource shortage, and is also a key scheme for promoting cost reduction and efficiency improvement of the energy storage market.

As a key component of sodium ion batteries, the positive electrode material plays a critical role in determining the energy density and cost competitiveness of the battery. Among the various candidate materials, layered transition metal oxides are of great interest due to their high theoretical capacity and well-established manufacturing processes. In particular, the O3 phase structure is attractive due to its high sodium content (x≥0.7) and good reversibility, and is suitable for achieving high energy density. However, O3-phase layered transition metal oxides are often deficient in the safe voltage window (2.0-4.0V vs. Na ⁺/Na), which greatly hinders their commercial application.

Precise adjustment of the composition of the transition metal layer is particularly important because it can activate additional reversible redox reactions, thereby increasing specific capacity. The layered oxide rich in nickel shows high capacity due to its higher active element, but is limited by its high cost, while the layered oxide rich in manganese is more economical, but its structure is degraded and rate performance is poor due to Jahn-Teller effect of Mn ³⁺. In contrast, low nickel O3 layered oxides strike a good balance between high sodium content and potential cost advantages and are therefore expected to be candidates for the next generation of positive electrodes. At present, little is known about the phase change mechanism and sodium storage kinetics of low nickel layered oxides, and how to regulate the transition metal component to fully activate the redox of Ni to increase capacity is not reported.

Chinese patent CN119092657A discloses a low-nickel high-capacity sodium ion battery anode material, a preparation method and a sodium ion battery. The positive electrode material is in an irregular block shape and has a layered structure. The material can be prepared by coprecipitation precursor sintering or a high temperature solid phase method, and shows higher discharge gram capacity, average discharge voltage and lower material cost than the NFM111 system material, and good multiplying power and cycle performance are maintained. However, the oxidation-reduction reaction of the Zn doped high-potential Ni ³⁺/Ni⁴⁺ or O ² is advanced, so that the material generates irreversible phase change under high voltage, a small amount of Zn migrates to Na to cause cycle performance attenuation in the cycle process, and zinc element has no chemical activity, so that the electron transfer is greatly hindered, and the rate performance is greatly negatively influenced.

Chinese patent CN115911331a discloses a method for preparing a low nickel copper manganese base sodium ion battery anode material. The method comprises the steps of wet grinding and mixing a nickel source, a manganese source and a copper source, adding carbonate, performing coprecipitation reaction to obtain a carbonate precursor, uniformly mixing the precursor with a carbon nano tube, adding a sodium source, and calcining to obtain the anode material. The invention relates to a method for manufacturing a semiconductor device. According to the invention, the mixed sintering of the carbon nano tube is doped, so that the promotion of crystal grains and crystal boundaries is obviously prevented, the stable crystal phase structure is maintained, the problem of crystal phase transformation is solved, meanwhile, the sintered carbon nano tube forms an electronic conduction structure of a network structure, the contact between a positive electrode material and electrolyte is reduced, the occurrence of side reaction is inhibited, and the structure is stable under the high-voltage condition. However, the carbon nano tube has overlarge specific surface, is easy to agglomerate and difficult to mix uniformly, and meanwhile, the side reaction in the charge and discharge process can be increased due to the larger specific surface, the gas production risk is increased, and the long-cycle performance is reduced;

Chinese patent CN117936734a discloses a low-nickel high-capacity sodium ion battery positive electrode material, its preparation method and application. The invention controls the nickel content component to be 0.08-0.12, which can obviously reduce the production cost compared with NaNi _1/3Mn_1/3Fe_1/3O₂, and the invention can reduce the cost and simultaneously has high capacity, high median voltage and high compaction density by optimizing the components and coating the surface of the layered oxide with a dot-shaped array coating layer with special morphology. However, the system has higher iron content, the prepared layered material has the phenomenon of local enrichment of iron element, and high voltage is easy to cause Fe ⁴⁺ migration, so that irreversible phase change and structural damage are caused, and the long-cycle performance is reduced.

In view of this, the present invention has been made.

Disclosure of Invention

The invention aims to provide a high-capacity sodium ion battery anode material, and a preparation method and application thereof.

The invention is realized in the following way:

In a first aspect, the invention provides a high-capacity sodium ion battery positive electrode material, wherein the molecular formula of the high-capacity sodium ion battery positive electrode material is Na _xNi_yFe_zM_mMn_nO₂, x is more than or equal to 0.8,0.1 and less than or equal to y is less than or equal to 0.2, y+z=0.6, m is less than or equal to 0.1, m+n=0.4, and M represents a transition divalent metal element.

In an alternative embodiment, x >0.96; m: n=1:3.5-5.

In an alternative embodiment, the M corresponding ion is selected from at least one of Mg ²⁺、Cu²⁺、Zn²⁺、Co²⁺、Ca²⁺、Ba²⁺ and Sr ²⁺.

In an alternative embodiment, the M ion is selected from Mg ²⁺ and Cu ²⁺;Mg²⁺ and Cu ²⁺ in a doping amount ratio of 1:1-2.

In an alternative embodiment, the high capacity sodium ion battery positive electrode material has at least one parametric characterization of features (1) -feature (5):

the high-capacity sodium ion battery anode material has an average particle diameter of 5 μm;

The characteristic (2) is that the Mn ³⁺/Mn⁴⁺ proportion in the positive electrode material of the high-capacity sodium ion battery is 1:3-4;

The positive electrode material of the high-capacity sodium ion battery is of a layered structure, and the compaction density is more than or equal to 3.0g cm ^-3;

The characteristic (4) is that the average sodium ion diffusion coefficient of the high-capacity sodium ion battery anode material in the charge and discharge process is more than 1 multiplied by 10 ^-10cm² s^-1;

and (5) the cycle life of the high-capacity sodium ion battery anode material in a full battery is more than 1000 circles.

In a second aspect, the present invention provides a method for preparing a high capacity sodium ion battery cathode material according to the previous embodiment, comprising adding a sodium source, a nickel source, an iron source, a manganese source and an M source to a solvent in stoichiometric ratio, stirring, followed by ball milling and high temperature sintering.

In an alternative embodiment, the method for preparing a high capacity sodium ion battery positive electrode material includes at least one of the features (6) -18:

Characterized in that the solvent comprises at least one of absolute ethyl alcohol and acetone;

The ball milling speed is 300-500rpm, and the mixing time is 6-10h;

the ball milling is carried out under vacuum condition;

the high-temperature sintering comprises the steps of firstly heating to 1000-1050 ℃ from room temperature, preserving heat for 10-20h, then cooling to 180-220 ℃, and then putting into a box body filled with inert gas to cool to room temperature;

the method is characterized in that the heating rate in the high-temperature sintering process is 1 ℃ per minute and 3 ℃ per minute, and the cooling rate is 1 ℃ per minute and 3 ℃ per minute;

characterized in that (11) after ball milling and before high-temperature sintering, the mixture is pressed for 2-5min under the pressure of 8-12 MPa;

The method is characterized by comprising the steps of (12) grinding the sintered material after the high-temperature sintering, and sieving the ground material with a 300-400-mesh sieve;

The characteristic (13) is that the sodium source is at least one of sodium carbonate, sodium acetate, sodium nitrate, sodium fluoride and sodium chloride;

The characteristic (14) is that the nickel source is at least one of nickel oxide, nickel trioxide, nickel carbonate, nickel acetate, nickel chloride, nickel sulfate and nickel nitrate;

the characteristic (15) is that the iron source is at least one of ferrous oxide, ferric oxide, ferrous carbonate, ferric acetate, ferrous chloride, ferric chloride, ferrous sulfate, ferric sulfate, ferrous nitrate and ferric nitrate;

characterized in that the manganese source is at least one of manganese monoxide, manganese trioxide, manganese dioxide, manganese carbonate, manganese acetate, manganese chloride, manganese sulfate and manganese nitrate;

Characterized in that (17) the M source comprises at least one corresponding metal oxide of Mg ²⁺、Cu²⁺、Zn²⁺、Co²⁺、Ca²⁺、Ba²⁺ and Sr ²⁺;

The method is characterized in that the sodium source is anhydrous sodium carbonate, the nickel source is nickel oxide, the iron source is ferric oxide, the manganese source is manganese sesquioxide, and the M source is at least one of magnesium oxide and copper oxide.

In a third aspect, the present invention provides a high-capacity sodium-ion battery positive electrode material according to any one of the preceding embodiments or a use of the high-capacity sodium-ion battery positive electrode material prepared by the method for preparing a high-capacity sodium-ion battery positive electrode material according to any one of the preceding embodiments in preparing a sodium-ion battery positive electrode material.

In a fourth aspect, the present invention provides a sodium ion battery, which includes a positive electrode sheet, where the positive electrode sheet uses the high-capacity sodium ion battery positive electrode material according to any one of the foregoing embodiments or the high-capacity sodium ion battery positive electrode material prepared by the preparation method of the high-capacity sodium ion battery positive electrode material according to any one of the foregoing embodiments as a positive electrode material.

In a fifth aspect, the present invention provides an electric device, including a sodium ion battery according to the foregoing embodiment.

The invention has the following beneficial effects:

The high-capacity sodium ion battery anode material provided by the invention is beneficial to improving the bulk sodium content, reducing the Mn ³⁺ content, reducing the Taylor effect of ginger and promoting the cycle performance by adopting a technology of substituting a divalent transition metal element for a high-valence manganese element, is beneficial to adjusting the composition of the transition metal element in the layered oxide, is beneficial to deeply activating the oxidation reduction of nickel in the charge and discharge process and is beneficial to improving the reversible capacity, and in the invention, low nickel, high iron and high manganese are used as main elements, so that the material cost is beneficial to being reduced. In the preparation process, the process of wet vacuum mixing and tabletting sintering is adopted, so that the crystallinity and purity of the material are improved, and large-size single crystals are formed.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is an SEM electron microscope image of the high-capacity sodium ion battery cathode material provided in example 1;

fig. 2 is an SEM electron microscope image of the positive electrode material of the high-capacity sodium ion battery provided in example 2;

FIG. 3 is an SEM image of the positive electrode material of the high capacity sodium ion battery provided in example 3;

FIG. 4 is an SEM image of the positive electrode material of the sodium ion battery provided in comparative example 1;

fig. 5 is an SEM electron microscope image of the positive electrode material of the sodium ion battery provided in example 5;

fig. 6 is an SEM electron microscope image of the positive electrode material of the sodium ion battery provided in example 7.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

The invention provides a high-capacity sodium ion battery anode material, the molecular formula of the high-capacity sodium ion battery anode material is Na _xNi_yFe_zM_mMn_nO₂, x is more than or equal to 0.8,0.1 and less than or equal to y is less than or equal to 0.2, y+z=0.6, m is less than or equal to 0.1, m+n=0.4, and M represents a transition divalent metal element.

Wherein, the ion corresponding to M is selected from at least one of Mg ²⁺、Cu²⁺、Zn²⁺、Co²⁺、Ca²⁺、Ba²⁺ and Sr ²⁺, and preferably, the ion corresponding to M is selected from at least one of Mg ²⁺ and Cu ²⁺.

In some embodiments, x >0.96; m: n=1:3.5-5. According to the invention, the doping amount of the transition divalent metal element can be limited by controlling the proportion of m and n, so that the divalent element can be better substituted and adjusted to the electronic structure, and the cycle performance and the multiplying power performance of the material are effectively improved. Wherein, the transition divalent metal element M replaces Mn ions, and the bulk sodium content is improved by regulating and controlling the local charge distribution in the crystal structure. The ratio of Mn ³⁺/Mn³⁺ in the positive electrode material of the high-capacity sodium ion battery is 1:3-4.

When the M corresponding ions are selected from a plurality of types, the sum of doping amounts of the plurality of M ions is M, and further, the doping amount ratio of the M corresponding ions selected from Mg ²⁺, cu ²⁺;Mg²⁺ and Cu ²⁺ is 1:1-2. According to the invention, the aggregation of Mn ³⁺ and the occurrence of Jahn-Teller effect can be inhibited by further limiting the doping amounts of Mg ²⁺ and Cu ²⁺, so that the structural stability of the material is improved.

In addition, the average grain diameter of the positive electrode material of the high-capacity sodium ion battery is 5 mu m, and the positive electrode material of the high-capacity sodium ion battery is of a layered structure. The compacted density of the positive electrode material of the high-capacity sodium ion battery is more than or equal to 3.0gcm ^-3.

Further, the invention provides a preparation method of the high-capacity sodium ion battery anode material, which comprises the steps of adding a sodium source, a nickel source, an iron source, a manganese source and an M source into a solvent according to stoichiometric ratio, stirring, and then performing ball milling and high-temperature sintering.

Specifically, the method comprises the following steps:

S1, mixing.

The sodium source, nickel source, iron source, manganese source and M source were added to the solvent and stirred, followed by vacuum ball milling.

Wherein the sodium source includes, but is not limited to, at least one of sodium carbonate, sodium acetate, sodium nitrate, sodium fluoride, and sodium chloride, the nickel source includes, but is not limited to, at least one of nickel oxide, nickel trioxide, nickel carbonate, nickel acetate, nickel chloride, nickel sulfate, and nickel nitrate, the iron source includes, but is not limited to, at least one of ferrous oxide, ferric oxide, ferrous carbonate, ferric acetate, ferrous chloride, ferric chloride, ferrous sulfate, ferric sulfate, manganese nitrate, and ferric nitrate, and the manganese source includes, but is not limited to, at least one of manganese monoxide, manganese trioxide, manganese dioxide, manganese carbonate, manganese acetate, manganese chloride, manganese sulfate, and manganese nitrate. The M source comprises at least one corresponding metal oxide of Mg ²⁺、Cu²⁺、Zn²⁺、Co²⁺、Ca²⁺、Ba²⁺、Sr²⁺;

Preferably, the sodium source is anhydrous sodium carbonate, the nickel source is nickel oxide, the iron source is ferric oxide, the manganese source is manganic oxide, and the M source is at least one of magnesium oxide and copper oxide.

In the invention, the solvent wet method is adopted for vacuum mixing, so that the uniformity of the materials is better. Wherein the solvent comprises at least one of absolute ethyl alcohol and acetone, the rotation speed of vacuum ball milling is 300-500rpm, and the mixing time is 6-10h.

S2, tabletting.

Tabletting the mixture obtained in the step S1 for 2-5min under the pressure of 8-12 MPa.

In the invention, the tablet compresses loose powder raw materials into a compact sheet structure through mechanical pressure, so that gaps among particles are reduced, and the particles are in close contact. This helps to promote solid phase diffusion during subsequent high temperature sintering, increases the contact area between particles, accelerates diffusion of atoms or ions, and shortens sintering time. Meanwhile, the porosity is reduced, the internal defects of the sintered material are reduced, and the overall density is improved.

The mixed raw materials may have the problem of uneven local components, and the tabletting uniformly distributes different components through external force, so that uneven performance (such as conductivity and capacity difference) caused by component segregation during sintering is avoided. The pressed green body has certain mechanical strength, is convenient for carrying and subsequent treatment, can maintain the preset geometric shape (such as sheet shape and block shape) in the sintering process, and prevents deformation or cracking at high temperature. For the multicomponent positive electrode material, tabletting can force different raw materials (such as lithium source and transition metal oxide) to be in close contact, so that the high-temperature solid-phase reaction is ensured to be fully carried out, and unreacted residues are prevented from affecting the electrochemical performance.

It will be appreciated that in some other embodiments, the high temperature sintering of the vacuum ball milled material may be performed directly without the tabletting step.

S3, sintering at a high temperature.

The high-temperature sintering can lead the material to form the anode material with stable crystal structure, high purity and good electrochemical performance, wherein the high-temperature sintering comprises the steps of firstly heating to 1000-1050 ℃ from room temperature, preserving heat for 10-20 hours, then cooling to 180-220 ℃, and then putting the anode material into a box body filled with inert gas to cool to room temperature, and preferably, the temperature rising rate in the high-temperature sintering process is 1 ℃ per minute 3 ℃ per minute, and the cooling rate is 1 ℃ per minute 3 ℃ per minute.

In the invention, the high-temperature sintering temperature, the heating rate and the cooling rate are controlled, so that the positive electrode material with higher purity is formed, and the gas production is reduced. The invention can lead the reaction to be more uniform by slowly heating, and avoid the segregation of components caused by local overheating. The gradual decomposition of organic matters or residual solvents is facilitated, and air holes and cracks are reduced. The invention can reduce thermal stress by slowly cooling, avoid particle cracking or lattice distortion, and is beneficial to promoting ordered arrangement of atoms and improving crystallinity.

In the invention, the process of wet vacuum mixing and tabletting sintering is adopted, which is favorable for improving the crystallinity and purity of the material and forming large-size single crystals.

S4, grinding.

And (3) grinding the sintered material and sieving the ground material with a 300-400 mesh sieve after the high-temperature sintering in the step (S3).

In the invention, the sintered material is usually agglomerated or formed into larger particles, and the sintered material can be crushed to the target particle size (such as micron or submicron), so that the specific surface area is increased, and the lithium ion diffusion rate is improved. The particle size distribution is more uniform through grinding, and uneven electrode coating caused by oversized particles or agglomeration caused by undersized particles is avoided, so that the compaction density and the cycling stability of the electrode are optimized. Further, grinding can remove sintered hard shell on the surface of the sintered material, expose fresh surface and improve the contact area and the reactivity of the material and electrolyte. Grinding can also slightly modify the particle surface morphology, reduce sharp corners and reduce the risk of puncturing the separator during electrode preparation. The fine and uniform particles are easier to disperse in the electrode slurry, reduce slurry sedimentation or agglomeration, improve coating uniformity, improve compaction density, facilitate uniform mixing of materials, conductive agents (such as carbon black) and binders (such as PVDF), form a continuous conductive network, reduce electrode internal resistance, and play a role in regulating electrochemical performance. The particle size of the high-capacity sodium ion battery anode material can reach 5 mu m after grinding.

In addition, the invention provides application of the high-capacity sodium ion battery anode material in preparing the sodium ion battery anode material.

For example, the invention provides a sodium ion battery, which comprises a positive electrode plate, wherein the positive electrode plate takes the positive electrode material of the high-capacity sodium ion battery as a positive electrode material. The invention also provides an electric device which comprises the sodium ion battery of the embodiment.

The features and capabilities of the present invention are described in further detail below in connection with the examples.

Example 1

The embodiment provides a preparation method of a layered oxide positive electrode material of a sodium ion battery, wherein the chemical formula of the layered oxide positive electrode material of the sodium ion battery is Na _0.96Ni_0.2Mn_0.32Fe_0.4Mg_0.08O₂, and the preparation method comprises the following steps:

Mixing Na ₂CO₃、NiO、Mn₂O₃、Fe₂O₃ and MgO in an agate mortar according to stoichiometric ratio, transferring into a ball mill, adding a proper amount of absolute ethyl alcohol, vacuum packaging, mixing for 8 hours at 400rpm, pouring the uniformly ground raw materials into a die of a tablet press, placing the die into the tablet press, pressing into a wafer with the pressure of 10MPa for 2min, placing the pressed raw material wafer into a corundum square boat, placing into a muffle furnace, heating to 1020 ℃ at a temperature rise rate of 3 ℃ per min, preserving heat for 15 hours, cooling to 200 ℃ at a temperature rise rate of 2 ℃ per min, immediately placing the material into a glove box filled with Ar after heat treatment to prevent the material from contacting any moisture until the temperature is reduced, then transferring the material into a drying room (-70 ℃ dew point, relative humidity <1%, and the like) with low humidity, grinding the material into powder by using the mortar, and sieving by using a sieve with a 325-mesh aperture screen, thus obtaining the Na _0.96Ni_0.2Mn_0.32Fe_0.4Mg_0.08O₂ anode material.

Referring to FIG. 1, it can be seen from FIG. 1 that the obtained sample was a large single crystal in a plate-like form, with a size of 5. Mu.m.

Example 2

The embodiment provides a preparation method of a layered oxide positive electrode material of a sodium ion battery, wherein the chemical formula of the layered oxide positive electrode material of the sodium ion battery is Na _0.96Ni_0.2Mn_0.32Fe_0.4Cu_0.08O₂, and the preparation method comprises the following steps:

Mixing Na ₂CO₃、NiO、Mn₂O₃、Fe₂O₃ and CuO in an agate mortar according to stoichiometric ratio, transferring into a ball mill, adding a proper amount of absolute ethyl alcohol, vacuum packaging, mixing for 8 hours at 400rpm, pouring the uniformly ground raw materials into a die of a tablet press, placing the die into the tablet press, pressing into a wafer with the pressure of 10MPa for 2min, placing the pressed raw material wafer into a corundum square boat, placing into a muffle furnace, controlling the temperature rising rate to be 3 ℃ per min, heating to 1020 ℃, preserving heat for 15 hours, cooling to 200 ℃ at the rate of 2 ℃ per min, immediately placing the material into a glove box filled with Ar after heat treatment to prevent the material from contacting any moisture until the temperature is reduced, transferring the material into a drying room with low humidity, grinding the material into powder by using the mortar, and sieving by using a sieve with a 325 mesh sieve, thereby obtaining the Na _0.96Ni_0.2Mn_0.32Fe_0.4Cu_0.08O₂ anode material.

Referring to FIG. 2, it can be seen from FIG. 2 that the obtained sample was also a large single crystal in a plate-like form, with a size of 515. Mu.m.

Example 3

The embodiment provides a preparation method of a layered oxide positive electrode material of a sodium ion battery, wherein the chemical formula of the layered oxide positive electrode material of the sodium ion battery is Na _0.96Ni_0.2Mn_0.32Fe_0.4Mg_0.04Cu_0.04O₂, and the preparation method comprises the following steps:

Mixing Na ₂CO₃、NiO、Mn₂O₃、Fe₂O₃, mgO and CuO in an agate mortar according to a stoichiometric ratio, transferring into a ball mill, adding a proper amount of absolute ethyl alcohol, vacuum packaging, mixing for 8 hours at 400rpm, pouring the uniformly ground raw materials into a die of a tablet press, placing the die into the tablet press, pressing into a wafer with the pressure of 10MPa for 2min, placing the pressed raw material wafer into a corundum square boat, placing into a muffle furnace, controlling the temperature rising rate to be 3 ℃ per min, heating to 1020 ℃, preserving heat for 15 hours, cooling to 200 ℃ at the rate of 2 ℃ per min, immediately placing the material into a glove box filled with Ar after heat treatment to prevent contacting any moisture until the temperature is reduced, transferring the material into a drying room with low humidity, grinding the material into powder by using the mortar, and sieving by using a sieve with a 325 mesh sieve, thereby obtaining the Na _0.96Ni_0.2Mn_0.32Fe_0.4Mg_0.04Cu_0.04O₂ anode material.

Referring to FIG. 3, it can be seen from FIG. 3 that the obtained sample is a large single crystal in a plate-like form, and the surface thereof is smoother and the size thereof is 5. Mu.m.

Example 4

The embodiment provides a preparation method of a layered oxide positive electrode material of a sodium ion battery, wherein the chemical formula of the layered oxide positive electrode material of the sodium ion battery is Na _0.96Ni_0.2Mn_0.32Fe_0.4Mg_0.02Cu_0.06O₂. The preparation process is basically the same as in example 3.

Example 5

The present embodiment provides a method for preparing a layered oxide cathode material of a sodium ion battery, where the chemical formula of the layered oxide cathode material of the sodium ion battery is Na _0.98Ni_0.2Mn_0.31Fe_0.4Mg_0.09O₂, and the preparation process is substantially the same as that of embodiment 1.

Example 6

The present embodiment provides a method for preparing a layered oxide cathode material of a sodium ion battery, where the chemical formula of the layered oxide cathode material of the sodium ion battery is Na _0.92Ni_0.2Mn_0.34Fe_0.4Mg_0.06O₂, and the preparation process is substantially the same as that of embodiment 1.

Comparative example 1

The comparative example provides a preparation method of a layered oxide cathode material of a sodium ion battery, wherein the chemical formula of the layered oxide cathode material of the sodium ion battery is Na ₀₉₆Ni₀₂Mn₀₄Fe₀₄O₂, and the preparation method comprises the following steps:

Mixing Na ₂CO₃、NiO、Mn₂O₃ and Fe ₂O₃ in an agate mortar according to stoichiometric ratio, transferring into a ball mill, adding a proper amount of absolute ethyl alcohol, vacuum packaging, mixing for 8 hours at 400rpm, pouring the uniformly ground raw materials into a die of a tablet press, placing the die into the tablet press, pressing into a wafer with the pressure of 10MPa for 2min, placing the pressed raw material wafer into a corundum ark, placing into a muffle furnace, controlling the temperature rising rate to be 3 ℃ per min, heating to 1020 ℃, preserving heat for 15 hours, cooling to 200 ℃ at the rate of 2 ℃ per min, immediately placing the material into a glove box filled with Ar after heat treatment to prevent contact with any moisture until the temperature is reduced, then transferring the material into a drying room (-70 ℃ dew point with the relative humidity of <1 percent) with low humidity, grinding the material into powder by using the mortar, and sieving by using a mesh 325, thereby obtaining the Na _0.96Ni_0.2Mn_0.4Fe_0.4O₂ anode material.

Referring to FIG. 4, it can be seen from FIG. 4 that the obtained sample was a large single crystal in a plate-like form, which had a rough surface and many secondary particles with a size of 5.20. Mu.m.

Comparative example 2

The comparative example provides a method for preparing a layered oxide cathode material of a sodium ion battery, wherein the chemical formula of the layered oxide cathode material of the sodium ion battery is Na ₁Ni_0.2Mn_0.3Fe_0.4Mg_0.1O₂, and the preparation process is basically the same as that of the example 1.

Comparative example 3

The comparative example provides a method for preparing a layered oxide cathode material of a sodium ion battery, wherein the chemical formula of the layered oxide cathode material of the sodium ion battery is Na _0.8Ni_0.2Mn_0.32Fe_0.4Ti_0.08O₂, and the preparation process is basically the same as that of the example 1.

Comparative example 4

The comparative example provides a method for preparing a layered oxide cathode material of a sodium ion battery, wherein the chemical formula of the layered oxide cathode material of the sodium ion battery is Na _0.8Ni_0.2Mn_0.32Fe_0.4Cu_0.04Ti_0.04O₂, and the preparation process is basically the same as that of the example 1.

Comparative example 5

The comparative example differs from example 1 in that the comparative example adopts natural cooling to 200 ℃ after high-temperature sintering, the cooling rate is not controlled, and other steps and parameters are kept consistent.

Referring to fig. 5, it can be seen from fig. 5 that the resulting sample is extremely heterogeneous, has a rough surface and a large number of secondary particles, and has a size of 1 μm.

Comparative example 6

The comparative example differs from example 1 in that the temperature of this example was reduced to 200 ℃ with a cooling rate of 5 ℃ per minute after high temperature sintering, and other steps and parameters remained consistent.

Comparative example 7

The comparative example differs from example 1 in that the ball mill mixing in this example uses dry mixing, no solvent is added, and other steps and parameters remain the same.

Referring to fig. 6, it can be seen from fig. 6 that the obtained sample is not uniform in size, has a rough surface and irregular morphology, and has a size of 1 μm.

Experimental example 1

The performance of the high-capacity sodium ion battery anode materials prepared in the examples 1-6 and the comparative examples 1-7 is detected, wherein the detection method comprises the steps of analyzing the average particle size by a laser particle size analyzer, detecting the gas production of the first charge and discharge ring by an in-situ differential electrochemical mass spectrometer, calculating the compaction density of a pole piece after rolling by a thickness meter, measuring the residual alkali content by a potentiometric titrator, analyzing the Mn ³⁺/Mn⁴⁺ proportion by an X-ray photoelectron spectroscopy, and calculating the Na-O bond length by X-ray diffraction refinement.

Parameters relating to the cathode materials prepared in Table 1

From the table, the application can prepare the corresponding high-compaction-density large-size single crystal layered oxide positive electrode material through vacuum wet mixing and solid phase high-temperature calcination. The proportion of Mn ³⁺/Mn⁴⁺ is regulated and controlled by substitution of low-valence elements so as to reduce the residual alkali on the surface and reduce the gas production behavior of the anode material. Enhancing Na-O bond energy and increasing structural stability.

The comparative example 1 of the present application, which was not doped with divalent transition metal element, was compared with the data of example 1, and it can be seen that the gas yield and residual alkali CO ₃ ^2- content were significantly higher than those of example 1, the compaction density was significantly lower than that of example 1, and the Mn ³⁺/Mn⁴⁺ ratio regulation effect was poor.

In comparative example 2, in which the ratio of Mg to Mn is 1:3, and the ratio is not in the range of m: n=1:3.5-5 of the present application, the larger Mg doping amount results in a certain increase in gas yield and residual alkali CO ₃ ^2- content, a certain decrease in compaction density, and the overall performance is inferior to that of example 1, but superior to that of comparative example 1 without doping.

The Ti doped with the element in comparative example 3 can be seen that the overall performance is significantly reduced compared to that of example 1, since substitution of Ti with tetravalent does not increase the bulk sodium content and the Mn ³⁺/Mn⁴⁺ ratio cannot be controlled, which is fully demonstrated that not all transition metals can meet the performance requirements of the present application.

The doping element in comparative example 4 is a combination of Cu and Ti, which is not quite different from that in comparative example 3, and it is found that the combination of Cu and Ti does not play a synergistic effect, whereas the effect of doping Cu and Mg simultaneously in example 3 in the present application is significantly better than that of example 1 doped with Mg alone and example 2 doped with Cu alone, which fully proves that the combination of Cu and Mg has a synergistic effect.

In comparative example 5, after sintering at high temperature, the sample is naturally cooled to 200 ℃ without controlling the cooling rate, so that the sample is nonuniform, sodium ions cannot be fully embedded into crystal lattices during natural cooling, na ₂ O is formed on the surface and reacts with H ₂O/CO₂ in the air to generate Na ₂CO₃, and Na ₂CO₃ is decomposed in the charging and discharging processes of the battery to release CO ₂ (gas production). Lattice defects (e.g., oxygen vacancies) caused by cooling stress may become active sites for electrolyte decomposition, further increasing gas production. Thus, the gas yield and residual alkali CO ₃ ^2- content were significantly higher than in example 1 and the compaction density was lower than in example 1.

The higher cooling rate is adopted for cooling after high-temperature sintering in comparative example 6, which can lead to partial Na ⁺ to stay at high-energy sites (such as grain boundaries or surfaces) and increase the generation risk of surface residual alkali (Na ₂ O/NaOH). Rapid cooling results in thermal stress build-up, which may initiate microcracks or oxygen vacancies, exposing more active surfaces (e.g., mn ³⁺), exacerbating residual alkali formation and gassing. Thus, the gas yield and residual alkali CO ₃ ^2- content were significantly higher than in example 1 and the compaction density was lower than in example 1.

The dry blending used in comparative example 7 resulted in a non-uniform sample size, a rough surface and irregular morphology, a significantly higher gas yield and residual alkali CO ₃ ^2- content than example 1, and a lower compaction density than example 1.

Experimental example two

The positive electrode materials provided in examples 1 to 6 and comparative examples 1 to 7 above were prepared into batteries. The preparation method comprises the steps of adding a certain amount of NMP (N-methyl pyrrolidone) into PVDF (polyvinylidene fluoride) =8:1:1 (Super P) serving as a positive electrode material, uniformly mixing, coating and drying to obtain a pole piece with the surface density of 10mg/cm ³, compacting the pole piece to be about 3.3g/cm ³ after rolling by a roll press, cutting the pole piece to be a 14mm round pole piece, placing the round pole piece in a glove box for standby, taking a sodium hexafluorophosphate electrolyte as a counter electrode of a battery, selecting a glass fiber diaphragm, cutting the sodium hexafluorophosphate electrolyte into 18mm wafers, and assembling the pole piece, the positive electrode piece, the diaphragm, the negative electrode piece, the gasket, the elastic piece and the negative electrode shell into a CR2025 button battery according to the sequence, wherein the test voltage is 2.0-4.0V, and the test equipment is Xinwei. The electrochemical performance test adopts constant current charge and discharge test, namely constant current is set, so that the battery is subjected to charge and discharge circulation for a specified number of times under the current condition, and the cycle life and the rapid charge and discharge capacity of the battery are evaluated.

Table 2 electrochemical properties table of the positive electrode materials prepared

As can be seen from the above table, the layered oxide cathode materials prepared by substitution of divalent elements in examples 1 to 6 of the present application have higher discharge gram capacity, rate capability and cycle stability, exhibit excellent overall electrochemical properties, and are significantly superior to comparative examples 1 to 7.

In conclusion, the high-capacity sodium ion battery anode material provided by the invention is beneficial to improving the bulk sodium content, reducing the Mn ³⁺ content and reducing the Taylor effect by using a divalent transition metal element to replace a high-valence manganese element technology, is beneficial to improving the cycle performance, is beneficial to introducing the divalent metal element into a transition metal layer, and is beneficial to improving the reversible capacity by further adjusting the Mn ³⁺/Mn⁴⁺ proportion in the layered oxide to deeply activate the redox of nickel in the charge-discharge process, and is beneficial to reducing the material cost by taking low-nickel high-iron high-manganese as a main element. In the preparation process, the process of wet vacuum mixing and tabletting sintering is adopted, so that the crystallinity and purity of the material are improved, and large-size single crystals are formed.

The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The high-capacity sodium ion battery positive electrode material is characterized in that the molecular formula of the high-capacity sodium ion battery positive electrode material is Na _xNi_yFe_zM_mMn_nO₂, x is more than or equal to 0.8,0.1 and less than or equal to y and less than or equal to 0.2, y+z=0.6, m is less than or equal to 0.1, m+n=0.4, and M represents a divalent transition metal element.

2. The high capacity sodium ion battery positive electrode material of claim 1, wherein x >0.96; m: n = 1:3.5-5.

3. The high capacity sodium ion battery positive electrode material of claim 1, wherein the M corresponding ion is selected from at least one of Mg ²⁺、Cu²⁺、Zn²⁺、Co²⁺、Ca²⁺、Ba²⁺ and Sr ²⁺.

4. The positive electrode material of a high-capacity sodium ion battery according to claim 1, wherein the doping amount ratio of the ions corresponding to M selected from Mg ²⁺ and Cu ²⁺;Mg²⁺ and Cu ²⁺ is 1:1-2.

5. The high capacity sodium ion battery positive electrode material of claim 1, wherein the high capacity sodium ion battery positive electrode material has at least one parametric characterization of features (1) -feature (5):

6. A method for preparing a high capacity sodium ion battery positive electrode material according to any one of claims 1 to 5, comprising adding a sodium source, a nickel source, an iron source, a manganese source and an M source in stoichiometric proportions to a solvent, stirring, followed by ball milling and high temperature sintering.

7. The method of preparing a high capacity sodium ion battery positive electrode material according to claim 6, wherein the method of preparing a high capacity sodium ion battery positive electrode material comprises at least one of the following features (6) -18:

The ball milling speed is 300-500rpm, and the mixing time is 6-10h;

the ball milling is carried out under vacuum condition;

8. Use of the high-capacity sodium ion battery positive electrode material according to any one of claims 1 to 5 or the high-capacity sodium ion battery positive electrode material according to any one of claims 67.

9. A sodium ion battery, which is characterized by comprising a positive electrode plate, wherein the positive electrode plate takes the positive electrode material of the high-capacity sodium ion battery as defined in any one of claims 1 to 5 or the positive electrode material of the high-capacity sodium ion battery prepared by the preparation method of the positive electrode material of the high-capacity sodium ion battery as defined in any one of claim 67 as the positive electrode material.

10. An electrical device comprising the sodium ion battery of claim 9.