A sodium-ion battery positive electrode material precursor, a preparation method thereof and application thereof

Abstract

The application relates to a sodium ion battery positive electrode material precursor and a preparation method and application thereof. The preparation method does not use a small molecule complexing agent such as ammonia water commonly used in a traditional coprecipitation method, but uses a macromolecular complexing agent. The macromolecular complexing agent not only adjusts the concentration of free metal ions, but also promotes the uniform distribution of elements at a molecular level due to the combination of metal ions on a three-dimensional skeleton of an organic molecule, which is beneficial to the uniform coprecipitation of a crystallization reaction. Moreover, the macromolecular complexing agent has a regulating effect on the nucleation and growth of crystals, and can synthesize a precursor product with excellent morphology, structure and physical and chemical properties.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and relates to a cathode material precursor, its preparation method and application, and particularly to a sodium-ion battery cathode material precursor, its preparation method and application. Background Technology

[0002] Sodium-ion batteries have energy densities comparable to lithium iron phosphate batteries, and compared to lithium-ion batteries, they have potential advantages in terms of cost, safety, and rate performance, and are expected to be widely used in energy storage and low-speed electric vehicles.

[0003] Sodium-ion battery cathode materials are mainly divided into three categories: layered transition metal oxides, polyanionic compounds, and Prussian blue compounds. Among them, layered oxides have advantages in terms of energy density and cost, and their synthesis process is simple and environmentally friendly, making them the mainstream route for the industrialization of sodium-ion battery cathode materials.

[0004] The preparation methods of layered transition metal oxide cathode materials include solid-state method and co-precipitation method. The solid-state method involves directly mixing and sintering a sodium source with a metal oxide to obtain the cathode product. Although its process is relatively simple, the particle size and morphology of the material are not easy to control, and the material is prone to agglomeration during ball milling, resulting in low material uniformity. On the other hand, the co-precipitation method involves first preparing a hydroxide or carbonate precursor of the transition metal through a co-precipitation reaction, and then mixing it with a sodium source and calcining it to obtain the cathode material. The obtained product has controllable morphology, uniform particle size, and uniform element distribution.

[0005] CN108963233A discloses a Cu-Fe-Mn layered oxide precursor for sodium-ion batteries, its preparation method and application. The preparation method of the Cu-Fe-Mn layered oxide precursor includes: (1) preparing a mixed solution by mixing a copper source, an iron source, a manganese source and an optional metal M source in a preset ratio; (2) reacting the mixed solution, sodium hydroxide solution and ammonia water simultaneously in a protective atmosphere to obtain a reaction product; (3) post-processing the reaction product to obtain the Cu-Fe-Mn layered oxide precursor.

[0006] However, in the preparation of sodium ion cathode material hydroxide precursors, Cu 2+ Fe 2+ and Mn 2+ The precipitation coefficients of plasma vary considerably, which can easily lead to uneven element distribution in the crystallized products and affect the performance of the precursor. Current technologies use small-molecule complexing agents such as ammonia, which, while controlling the concentration of free metal ions and the precipitation rate, and regulating crystal growth, often result in precursor materials with problems such as elemental segregation, poor morphology, and undesirable physicochemical properties.

[0007] Therefore, in order to obtain precursor materials with excellent structure, morphology and physicochemical properties, it is necessary to provide an improved sodium-ion battery cathode material precursor, its preparation method and application. Summary of the Invention

[0008] The purpose of this invention is to provide a precursor for sodium-ion battery cathode material, its preparation method, and its application. The preparation method can synthesize a precursor product with excellent morphology, structure, and physicochemical properties, thereby facilitating the acquisition of high-performance sodium-ion battery cathode materials.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing a precursor of a sodium-ion battery cathode material, the method comprising:

[0011] In a protective atmosphere, a mixed salt solution and a precipitant solution are added to the bottom liquid, and after co-precipitation reaction, solid-liquid separation is performed to obtain the precursor of the sodium-ion battery cathode material.

[0012] The general chemical formula of the sodium-ion battery cathode material precursor is Ni. a Cu b Fe c Mn 1-a-b-c (OH)2, where 0≤a<0.5, 0<b≤0.3, 0.1≤c≤0.5;

[0013] The solute in the mixed salt solution includes a metal salt and a macromolecular complexing agent;

[0014] The macromolecular complexing agent includes any one or a combination of at least two of polyacrylic acid, polyaspartic acid, starch, or bovine serum albumin.

[0015] The preparation method provided by this invention does not use small molecule complexing agents such as ammonia commonly used in traditional coprecipitation methods, but instead uses macromolecular complexing agents. This not only adjusts the concentration of free metal ions, but also promotes the uniform distribution of each element at the molecular level by the binding of metal ions on the three-dimensional framework of organic molecules, which is beneficial to the uniform coprecipitation of crystallization reaction. Moreover, macromolecular complexing agents have a regulatory effect on crystal nucleation and growth, and can synthesize precursor products with excellent morphology, structure and physicochemical properties.

[0016] Furthermore, the preparation method provided by this invention reduces the use of small molecule complexing agents such as ammonia, thus reducing the generation of pollutants. Moreover, the entire preparation process is simple and easy to scale up for mass production. In addition, the general chemical formula of the sodium-ion battery cathode material precursor obtained by the preparation method provided by this invention is Ni. a Cu b Fe c Mn1-a-b-c (OH)2, where 0≤a<0.5, 0<b≤0.3, 0.1≤c≤0.5, is a cobalt-free, low-nickel layered oxide cathode precursor with broad application prospects in addressing the "lithium panic" and "cobalt anxiety".

[0017] The general chemical formula of the sodium-ion battery cathode material precursor obtained by the preparation method provided by this invention is Ni. a Cu b Fe c Mn 1-a-b-c (OH)2, where 0≤a<0.5, for example, it can be 0, 0.1, 0.2, 0.3 or 0.4, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable. When a is 0, it means that the precursor of the sodium-ion battery cathode material does not contain Ni.

[0018] 0 < b ≤ 0.3, for example, it can be 0.1, 0.15, 0.2, 0.25 or 0.3, but is not limited to the listed values. Other unlisted values ​​within the range also apply.

[0019] 0.1≤c≤0.5, for example, it can be 0.1, 0.2, 0.3, 0.4 or 0.5, but is not limited to the listed values. Other unlisted values ​​within the range also apply.

[0020] For example, in the macromolecular complexing agent of the present invention, the weight-average molecular weight of polyacrylic acid is in the range of 400,000-4,000,000, such as 400,000, 500,000, 800,000, 1,000,000, 1,500,000, 2,000,000, 2,500,000, 3,000,000, 3,500,000, or 4,000,000, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] For example, in the macromolecular complexing agent of the present invention, the weight-average molecular weight of polyaspartic acid is in the range of 1000-5000, for example, it can be 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500 or 5000, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] For example, in the macromolecular complexing agent of the present invention, the weight-average molecular weight of starch is in the range of 40,000-80,000, for example, it can be 40,000, 50,000, 60,000, 70,000 or 80,000, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] In the macromolecular complexing agent described in this invention, the molecular weight of bovine serum albumin is 68 kDa.

[0024] Preferably, the concentration of the macromolecular complexing agent in the mixed salt solution is 0.5-20 g / L, for example, it can be 0.5 g / L, 1 g / L, 3 g / L, 5 g / L, 8 g / L, 10 g / L, 12 g / L, 15 g / L, 18 g / L or 20 g / L, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0025] Preferably, the metal salt in the mixed salt solution includes any one or a combination of at least two of sulfates, chlorides, or nitrates. Typical but non-limiting combinations include combinations of sulfates and chlorides, chlorides and nitrates, sulfates and nitrates, or combinations of sulfates, chlorides, and nitrates.

[0026] For example, the metal salts corresponding to Ni include any one or at least two of nickel sulfate, nickel chloride, or nickel nitrate. Typical but non-limiting combinations include combinations of nickel sulfate and nickel chloride, nickel chloride and nickel nitrate, nickel sulfate and nickel nitrate, or combinations of nickel sulfate, nickel chloride, and nickel nitrate.

[0027] The metal salts corresponding to Cu include any one or at least two of copper sulfate, copper chloride, or copper nitrate. Typical but non-limiting combinations include the combination of copper sulfate and copper chloride, the combination of copper chloride and copper nitrate, the combination of copper sulfate and copper nitrate, or the combination of copper sulfate, copper chloride, and copper nitrate.

[0028] The metal salts corresponding to Fe include any one or at least two combinations of ferrous sulfate, ferrous chloride, or ferrous nitrate. Typical but non-limiting combinations include combinations of ferrous sulfate and ferrous chloride, ferrous chloride and ferrous nitrate, ferrous sulfate and ferrous nitrate, or combinations of ferrous sulfate, ferrous chloride, and ferrous nitrate.

[0029] The metal salts corresponding to Mn include any one or at least two of manganese sulfate, manganese chloride, or manganese nitrate. Typical but non-limiting combinations include manganese sulfate and manganese chloride, manganese chloride and manganese nitrate, manganese sulfate and manganese nitrate, or manganese sulfate, manganese chloride, and manganese nitrate.

[0030] In this invention, the metal salts in the mixed salt solution all have a valence state of +2.

[0031] Preferably, the total concentration of metal salts in the mixed salt solution is 90-110 g / L, for example, it can be 90 g / L, 95 g / L, 100 g / L, 105 g / L or 110 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] Preferably, the precipitant in the precipitant solution includes sodium hydroxide and / or potassium hydroxide.

[0033] Preferably, the mass percentage of the precipitant solution is 20-40 wt%, for example, it can be 20 wt%, 25 wt%, 30 wt%, 35 wt% or 40 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] Preferably, during the coprecipitation reaction, the flow rate of the mixed salt solution is 5-80 L / h, for example, it can be 5 L / h, 10 L / h, 20 L / h, 30 L / h, 40 L / h, 60 L / h or 80 L / h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the flow rate of the precipitant solution is such that the pH value of the coprecipitation reaction is 10-12, for example, it can be 10, 10.5, 11, 11.5 or 12, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, the temperature of the coprecipitation reaction is 30-60℃, for example, it can be 30℃, 35℃, 40℃, 45℃, 50℃, 55℃ or 60℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] Preferably, the coprecipitation reaction is carried out under stirring conditions.

[0038] Preferably, the stirring speed is 300-400 r / min, for example, it can be 300 r / min, 320 r / min, 350 r / min, 360 r / min, 380 r / min or 400 r / min, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0039] Preferably, the target particle size D50 of the coprecipitation reaction is 6-14 μm, for example, it can be 6 μm, 8 μm, 9 μm, 10 μm, 12 μm or 14 μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] Preferably, the base liquid is a mixture of a precipitant solution and water.

[0041] Preferably, the concentration of the precipitant in the base solution is 0.1-0.3 wt%, for example, it can be 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt% or 0.3 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0042] Too low a concentration of precipitant in the base solution will result in a larger initial particle size and uneven nucleation; while too high a concentration of precipitant will result in an excessive number of nuclei and may even produce microparticles.

[0043] In a second aspect, the present invention provides a precursor for a sodium-ion battery cathode material, wherein the precursor for the sodium-ion battery cathode material is prepared by the preparation method described in the first aspect.

[0044] The general chemical formula of the sodium-ion battery cathode material precursor is Ni. a Cu b Fe c Mn 1-a-b-c (OH)2, where 0≤a<0.5, 0<b≤0.3, 0.1≤c≤0.5.

[0045] Thirdly, the present invention provides a sodium-ion battery cathode material, which is prepared from the sodium-ion battery cathode material precursor described in the second aspect.

[0046] Fourthly, the present invention provides a sodium-ion battery, the sodium-ion battery comprising the sodium-ion battery positive electrode material described in the third aspect.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] (1) The preparation method provided by the present invention does not use small molecule complexing agents such as ammonia water commonly used in traditional coprecipitation methods, but uses macromolecular complexing agents. This not only adjusts the concentration of free metal ions, but also promotes the uniform distribution of each element at the molecular level by the binding of metal ions on the three-dimensional framework of organic molecules, which is beneficial to the uniform coprecipitation of crystallization reaction. Moreover, macromolecular complexing agents have a regulatory effect on the nucleation and growth of crystals, and can synthesize precursor products with excellent morphology, structure and physicochemical properties.

[0049] (2) Moreover, the preparation method provided by the present invention reduces the use of small molecule complexing agents such as ammonia water, reduces the generation of pollutants, and the entire preparation method has a simple process flow and is easy to carry out large-scale production.

[0050] (3) Furthermore, the chemical formula of the sodium-ion battery cathode material precursor obtained by the preparation method provided by the present invention is Ni a Cu b Fe c Mn 1-a-b-c (OH)2, where 0≤a<0.5, 0<b≤0.3, 0.1≤c≤0.5, is a cobalt-free, low-nickel layered oxide cathode precursor with broad application prospects in addressing the "lithium panic" and "cobalt anxiety". Attached Figure Description

[0051] Figure 1 This is a SEM image of the sodium-ion battery cathode material precursor obtained in Example 1. Detailed Implementation

[0052] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0053] Example 1

[0054] This embodiment provides a method for preparing a precursor for a sodium-ion battery cathode material, the method comprising the following steps:

[0055] Under a nitrogen atmosphere and with stirring at 350 r / min, a mixed salt solution and a precipitant solution were added to the bottom liquid, and a co-precipitation reaction was carried out at 40 °C until the target particle size (D50 of 10 μm) was achieved. After the co-precipitation reaction, solid-liquid separation was performed to obtain the Cu precursor for the sodium-ion battery cathode material. 0.2 Fe 0.3 Mn 0.5 (OH)2;

[0056] The solute in the mixed salt solution comprises 100 g / L of metal salt and 10 g / L of macromolecular complexing agent; the macromolecular complexing agent is polyaspartic acid (Wokai, model: XW2560840602);

[0057] The metal salts include copper sulfate, ferrous sulfate, and manganese sulfate;

[0058] The mass percentage of the precipitant solution is 30 wt%, and the precipitant is sodium hydroxide;

[0059] During the coprecipitation reaction, the flow rate of the mixed salt solution is 10 L / h; the flow rate of the precipitant solution is such that the pH value of the coprecipitation reaction is 10.3.

[0060] The base solution is a mixture of precipitant solution and water; the concentration of sodium hydroxide in the base solution is 0.1 wt%.

[0061] The SEM image of the sodium-ion battery cathode material precursor obtained in this embodiment is as follows: Figure 1 As shown.

[0062] Example 2

[0063] This embodiment provides a method for preparing a precursor for a sodium-ion battery cathode material, the method comprising the following steps:

[0064] Under a nitrogen atmosphere and with stirring at 300 rpm, a mixed salt solution and a precipitant solution were added to the bottom liquid, and a co-precipitation reaction was carried out at 30°C until the target particle size (D50 of 8 μm) was achieved. After the co-precipitation reaction, solid-liquid separation was performed to obtain the Cu precursor for the sodium-ion battery cathode material. 0.2 Fe 0.3 Mn 0.5 (OH)2;

[0065] The solute in the mixed salt solution comprises 90 g / L of a metal salt and 5 g / L of a macromolecular complexing agent; the macromolecular complexing agent is polyaspartic acid (Wokai, model: XW2560840602);

[0066] The metal salts include copper sulfate, ferrous sulfate, and manganese sulfate;

[0067] The mass percentage of the precipitant solution is 20 wt%, and the precipitant is sodium hydroxide;

[0068] During the coprecipitation reaction, the flow rate of the mixed salt solution is 20 L / h; the flow rate of the precipitant solution is such that the pH value of the coprecipitation reaction is 10.5.

[0069] The base solution is a mixture of precipitant solution and water; the concentration of sodium hydroxide in the base solution is 0.15 wt%.

[0070] Example 3

[0071] This embodiment provides a method for preparing a precursor for a sodium-ion battery cathode material, the method comprising the following steps:

[0072] Under a nitrogen atmosphere and with stirring at 400 rpm, a mixed salt solution and a precipitant solution were added to the bottom liquid, and a co-precipitation reaction was carried out at 60 °C until the target particle size (D50 of 12 μm) was achieved. After the co-precipitation reaction, solid-liquid separation was performed to obtain the Cu precursor for the sodium-ion battery cathode material. 0.2 Fe 0.3 Mn 0.5 (OH)2;

[0073] The solute in the mixed salt solution comprises 110 g / L of metal salt and 15 g / L of macromolecular complexing agent; the macromolecular complexing agent is polyaspartic acid (Wokai, model: XW2560840602);

[0074] The metal salts include copper sulfate, ferrous sulfate, and manganese sulfate;

[0075] The mass percentage of the precipitant solution is 40 wt%, and the precipitant is sodium hydroxide;

[0076] During the coprecipitation reaction, the flow rate of the mixed salt solution is 30 L / h; the flow rate of the precipitant solution is such that the pH value of the coprecipitation reaction is 10.9.

[0077] The base solution is a mixture of precipitant solution and water; the concentration of sodium hydroxide in the base solution is 0.2 wt%.

[0078] Example 4

[0079] This embodiment provides a method for preparing a precursor for a sodium-ion battery cathode material. Except for the concentration of the macromolecular complexing agent in the mixed salt solution being 0.5 g / L, the rest is the same as in Example 1.

[0080] Example 5

[0081] This embodiment provides a method for preparing a precursor for a sodium-ion battery cathode material. Except for the concentration of the macromolecular complexing agent in the mixed salt solution being 20 g / L, the rest is the same as in Example 1.

[0082] Example 6

[0083] This embodiment provides a method for preparing a precursor for a sodium-ion battery cathode material. Except for the macromolecular complexing agent being polyacrylic acid (McLean, model: P815683), the rest is the same as in Example 1.

[0084] Example 7

[0085] This embodiment provides a method for preparing a precursor for a sodium-ion battery cathode material. Except for the macromolecular complexing agent being starch (Maclean, model: S818110), the rest is the same as in Example 1.

[0086] Example 8

[0087] This embodiment provides a method for preparing a precursor for a sodium-ion battery cathode material. Except for the macromolecular complexing agent being bovine serum albumin (Sangon Biotech, model: A600332), the rest is the same as in Example 1.

[0088] Example 9

[0089] This embodiment provides a method for preparing a precursor for a sodium-ion battery cathode material. Besides adjusting the proportion of metal salts in the mixed salt solution to ensure the obtained precursor is Ni... 0.1 Cu 0.2 Fe 0.3 Mn 0.4 Except for (OH)2, everything else is the same as in Example 1.

[0090] In this embodiment, the metal salts in the mixed salt solution include nickel sulfate, copper sulfate, ferrous sulfate, and manganese sulfate.

[0091] Example 10

[0092] This embodiment provides a method for preparing a precursor for a sodium-ion battery cathode material. Besides adjusting the proportion of metal salts in the mixed salt solution to ensure the obtained precursor is Ni... 0.2 Cu 0.2 Fe 0.4 Mn 0.2 Except for (OH)2, everything else is the same as in Example 1.

[0093] In this embodiment, the metal salts in the mixed salt solution include nickel sulfate, copper sulfate, ferrous sulfate, and manganese sulfate.

[0094] Example 11

[0095] This embodiment provides a method for preparing a precursor for a sodium-ion battery cathode material. Besides adjusting the proportion of metal salts in the mixed salt solution to ensure the obtained precursor is Ni... 0.4 Cu 0.1 Fe 0.1 Mn 0.4 Except for (OH)2, everything else is the same as in Example 1.

[0096] In this embodiment, the metal salts in the mixed salt solution include nickel sulfate, copper sulfate, ferrous sulfate, and manganese sulfate.

[0097] Comparative Example 1

[0098] This comparative example provides a method for preparing a precursor for a sodium-ion battery cathode material. Except for replacing the macromolecular complexing agent with ammonium sulfate by mass, and making the concentration of the complexing agent in the mixed salt solution 10 g / L, everything else is the same as in Example 1.

[0099] The median particle size D50, specific surface area, and tap density of the sodium-ion battery cathode material precursors obtained in Examples 1-11 and Comparative Example 1 were measured, and the results are shown in Table 1.

[0100] Table 1

[0101] Example 1 10.13 76.51 1.07 Example 2 8.21 96.33 0.94 Example 3 11.85 69.23 1.22 Example 4 9.92 93.55 0.88 Example 5 10.25 74.32 1.01 Example 6 10.08 80.54 0.86 Example 7 10.03 83.91 0.85 Example 8 10.10 63.44 0.92 Example 9 10.28 105.98 0.86 Example 10 9.96 92.73 0.91 Example 11 10.07 88.64 0.96 Comparative Example 1 9.83 115.21 0.72

[0102] The sodium-ion battery cathode material precursors obtained in Examples 1-11 and Comparative Example 1 were respectively prepared into sodium-ion battery cathode materials: the sodium-ion battery cathode material precursors were mixed with sodium carbonate and calcined at 900°C for 15 hours to obtain sodium-ion battery cathode materials.

[0103] The sodium-ion battery cathode materials obtained in each embodiment and comparative example were used to prepare sodium-ion batteries. The preparation method is as follows:

[0104] Sodium-ion battery positive electrode material, binder polyvinylidene fluoride and conductive agent Super P were added to N-methylpyrrolidone at a mass ratio of 97:1.5:1.5 and stirred to form a positive electrode slurry; then the positive electrode slurry was uniformly coated onto the positive electrode current collector aluminum foil, and after drying and rolling, a positive electrode sheet was obtained.

[0105] Graphite, conductive agent acetylene black, thickener CMC and binder SBR are mixed in a mass ratio of 96:1:1.5:1.5, and deionized water is added and stirred thoroughly to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on the negative electrode current collector copper foil, and after drying, cold pressing and slitting, a negative electrode sheet is obtained.

[0106] Ethylene carbonate EC, ethyl methyl carbonate EMC, and diethyl carbonate DEC were mixed in a volume ratio of 1:1:1. Then, fully dried sodium salt NaPF6 was dissolved in the mixed solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0107] The positive electrode, separator, and negative electrode are stacked in sequence, then wrapped with an aluminum-plastic film, dried, and injected with electrolyte. After encapsulation, settling, and formation processes, a sodium-ion battery is obtained. The separator is a PE porous membrane with a thickness of 11 μm, an air permeability of 280 s / 100 mL, and a porosity of 40%.

[0108] The specific capacity, cycle capacity retention, and rate performance of the obtained sodium-ion batteries were tested, and the results are shown in Table 2.

[0109] The specific capacity test method is as follows: using the Blue Battery Test System, at 25℃, the sodium-ion battery is charged and discharged three times in a voltage range of 2V to 4.3V with a charge and discharge rate of 0.04A / g (calculated based on the mass of positive electrode material), and the specific capacity of the battery is measured.

[0110] The test method for cycle capacity retention is as follows: under 25℃ conditions, the battery is cycled with a charge-discharge cycle of 0.19A / g (calculated based on the mass of the positive electrode material). After 500 cycles, the discharge capacity of the battery at this time is divided by the discharge capacity of the first cycle, which is the battery's 500-cycle capacity retention.

[0111] The rate performance test method is as follows: Under 25℃ conditions, the battery is charged and discharged three times within a voltage range of 2V to 4.3V at a charge / discharge rate of 0.04A / g (calculated based on the mass of the positive electrode material), to obtain the discharge capacity C0 of the last cycle; then, the battery is charged to 4.3V at a charge rate of 0.04A / g (calculated based on the mass of the positive electrode material), and discharged to 2V at a discharge rate of 0.12A / g (calculated based on the mass of the positive electrode material), to obtain the discharge capacity C2 of the last cycle; the ratio of C2 / C0 is the rate performance.

[0112] Table 2

[0113] Example 1 132.5 83.1 87.5 Example 2 127.6 83.5 90.2 Example 3 131.5 80.7 85.3 Example 4 122.3 76.9 93.1 Example 5 133.2 82.8 88.9 Example 6 140.1 79.2 91.4 Example 7 130.4 80.2 88.3 Example 8 119.8 82.6 92.4 Example 9 145.7 84.3 86.8 Example 10 146.9 80.0 92.2 Example 11 162.3 77.4 87.7 Comparative Example 1 98.5 73.9 83.4

[0114] In summary, the preparation method provided by this invention does not use small-molecule complexing agents such as ammonia commonly used in traditional co-precipitation methods, but instead uses macromolecular complexing agents. This not only adjusts the concentration of free metal ions, but also promotes the uniform distribution of elements at the molecular level by the binding of metal ions on the three-dimensional framework of organic molecules, which is beneficial to the uniform co-precipitation of crystallization reactions. Moreover, macromolecular complexing agents have a regulatory effect on crystal nucleation and growth, enabling the synthesis of precursor products with excellent morphology, structure, and physicochemical properties. Furthermore, the preparation method provided by this invention reduces the use of small-molecule complexing agents such as ammonia, reducing the generation of pollutants. The entire preparation process is simple and easy to scale up for mass production. In addition, the general chemical formula of the sodium-ion battery cathode material precursor obtained by the preparation method provided by this invention is Ni. a Cu b Fe c Mn 1-a-b-c (OH)2, where 0≤a<0.5, 0<b≤0.3, 0.1≤c≤0.5, is a cobalt-free, low-nickel layered oxide cathode precursor with broad application prospects in addressing the "lithium panic" and "cobalt anxiety".

[0115] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a precursor for a sodium-ion battery cathode material, characterized in that, The preparation method includes: In a protective atmosphere, a mixed salt solution and a precipitant solution are added to the bottom liquid, and after co-precipitation reaction, solid-liquid separation is performed to obtain the precursor of the sodium-ion battery cathode material. The general chemical formula of the sodium-ion battery cathode material precursor is Ni. a Cu b Fe c Mn 1-a-b-c (OH)2, where 0≤a<0.5, 0.1≤b≤0.3, 0.1≤c≤0.5; The solute in the mixed salt solution includes a metal salt and a macromolecular complexing agent; The macromolecular complexing agent is polyaspartic acid, and the weight-average molecular weight of the polyaspartic acid ranges from 1000 to 5000. The concentration of the macromolecular complexing agent in the mixed salt solution is 10-15 g / L; The total concentration of metal salts in the mixed salt solution is 90-110 g / L; The base liquid is a mixture of precipitant solution and water; The precipitant in the precipitant solution includes sodium hydroxide and / or potassium hydroxide.

2. The preparation method according to claim 1, characterized in that, The metal salt in the mixed salt solution includes any one or a combination of at least two of sulfates, chlorides, or nitrates.

3. The preparation method according to claim 1, characterized in that, The mass percentage of the precipitant solution is 20-40 wt%.

4. The preparation method according to claim 1, characterized in that, During the coprecipitation reaction, the flow rate of the mixed salt solution is 5-80 L / h.

5. The preparation method according to claim 4, characterized in that, During the coprecipitation reaction, the flow rate of the mixed salt solution is 10-30 L / h.

6. The preparation method according to claim 1, characterized in that, The flow rate of the precipitant solution is such that the pH value of the coprecipitation reaction is 10-12.

7. The preparation method according to claim 6, characterized in that, The flow rate of the precipitant solution is such that the pH value of the coprecipitation reaction is 10-11.

8. The preparation method according to claim 1, characterized in that, The temperature of the coprecipitation reaction is 30-60℃.

9. The preparation method according to claim 1, characterized in that, The coprecipitation reaction was carried out under stirring.

10. The preparation method according to claim 9, characterized in that, The stirring speed is 300-400 r / min.

11. The preparation method according to claim 1, characterized in that, The target particle size D50 for the coprecipitation reaction is 6-14 μm.

12. The preparation method according to claim 1, characterized in that, The concentration of the precipitant in the bottom solution is 0.1-0.3 wt%.

13. The preparation method according to claim 12, characterized in that, The concentration of the precipitant in the bottom solution is 0.1-0.2 wt%.

14. A precursor for a sodium-ion battery cathode material, characterized in that, The sodium-ion battery cathode material precursor is prepared by the preparation method according to any one of claims 1-13; The general chemical formula of the sodium-ion battery cathode material precursor is Ni. a Cu b Fe c Mn 1-a-b-c (OH)2, where 0≤a<0.5, 0.1≤b≤0.3, 0.1≤c≤0.

5.

15. A sodium-ion battery cathode material, characterized in that, The sodium-ion battery cathode material is prepared from the sodium-ion battery cathode material precursor as described in claim 14.

16. A sodium-ion battery, characterized in that, The sodium-ion battery includes the sodium-ion battery cathode material as described in claim 15.

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