Sodium-ion battery positive electrode material precursor and preparation method thereof, positive electrode material, sodium-ion battery and electric equipment

Abstract

The invention provides a sodium ion battery positive electrode material precursor and a preparation method thereof, a positive electrode material, a sodium ion battery and electric equipment, the sodium ion battery positive electrode material precursor comprises a secondary particle composed of a plurality of primary particles, the secondary particle is spherical or sphere-like, the secondary particle comprises an inner layer, a secondary outer layer and an outer layer from inside to outside, the porosity of the inner layer and the porosity of the secondary outer layer are both larger than the porosity of the outer layer, and the porosity of the secondary outer layer is 16%-25%. The sodium ion battery positive electrode material precursor provided by the embodiment of the invention can effectively cope with the volume change in the charging and discharging process, so that the problems of cracking and structure collapse caused by large fault pores in secondary particles are avoided, and the cycle performance and the safety are improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a precursor for a sodium-ion battery cathode material and its preparation method, cathode material, sodium-ion battery, and electrical equipment. Background Technology

[0002] Sodium-ion batteries have attracted much attention due to their advantages such as the wide availability and low cost of raw materials. The cathode material is a key component of sodium-ion batteries, and its morphology, structure, and other characteristics are closely related to the overall performance of the battery.

[0003] Current cathode materials still suffer from structural instability and are prone to structural collapse, which affects the battery's cycle stability, safety, and other performance characteristics. Summary of the Invention

[0004] This application provides a precursor for a sodium-ion battery cathode material and its preparation method, a cathode material, a sodium-ion battery, and an electrical device.

[0005] This application provides a sodium-ion battery cathode material precursor, which includes secondary particles composed of multiple primary particles. The secondary particles are spherical or near-spherical and include an inner layer, a sub-outer layer, and an outer layer from the inside out. The porosity of the inner layer and the sub-outer layer are both greater than the porosity of the outer layer, and the porosity of the sub-outer layer is 16%-25%.

[0006] In some embodiments of this application, the radius of the inner layer is greater than or equal to the thickness of the sub-outer layer.

[0007] In some embodiments of this application, the radius of the inner layer is 30%-45% of the radius of the secondary particle; and / or the thickness of the outermost layer is 16%-30% of the radius of the secondary particle; and / or the thickness of the outer layer is 25%-40% of the radius of the secondary particle.

[0008] In some embodiments of this application, the porosity of the inner layer is 10%-25%; and / or the porosity of the outer layer is less than 6%; and / or the overall porosity of the secondary particles is 6%-16%.

[0009] In some embodiments of this application, the sodium-ion battery cathode material precursor satisfies at least one of the following conditions:

[0010] a. The particle size distribution span value of the secondary particles is 0.3-0.6, preferably 0.3-0.5;

[0011] b. The tap density of the secondary particles is greater than or equal to 1.9 g / cm³. 3 ;

[0012] c. The specific surface area of ​​the secondary particles is 7-15 m². 2 / g;

[0013] d. The average particle size D50 of the secondary particles is 9-13 μm;

[0014] e. The full width at half maximum (FWHM) of the diffraction peak of the 100 crystal plane of the secondary particles in the X-ray diffraction pattern is 0.35°-0.45°;

[0015] f. The sphericity of the secondary particles is ≥0.90;

[0016] g. The primary particles are arranged radially along the radial direction of the secondary particles;

[0017] h. The general chemical formula of the sodium-ion battery cathode material precursor is Ni x M y Me z (OH)2, wherein M is selected from at least one of Fe, Mn, Zn, Mg, and Al, Me is selected from at least one of Cu, Zr, Ca, Y, Ce, and Ti, and 0.2≤x≤0.4, 0.6≤y≤0.8, and 0≤z≤0.04.

[0018] Another embodiment of this application provides a method for preparing a precursor of a sodium-ion battery cathode material, comprising the following steps: mixing a solvent, a complexing agent, and a precipitant to obtain a base liquid; adding a metal salt solution, a complexing agent, and a precipitant to the base liquid to perform a co-precipitation reaction to obtain a mixture containing an intermediate product; then separating a portion of the mixture and continuing to add a metal salt solution, a complexing agent, and a precipitant to the remaining mixture to perform a co-precipitation reaction to obtain a reaction product; and post-processing the reaction product to obtain the precursor of the sodium-ion battery cathode material.

[0019] In some embodiments of this application, the preparation method satisfies at least one of the following conditions (1)-(11):

[0020] (1) The metal salt includes soluble salts of Ni, M and Me, wherein M is selected from at least one of Fe, Mn, Zn, Mg and Al, and Me is selected from at least one of Cu, Zr, Ca, Y, Ce and Ti; optionally, the soluble salt includes at least one of sulfate, nitrate, acetate and chloride.

[0021] (2) The total concentration of metal ions in the metal salt solution is 1-5 mol / L;

[0022] (3) The precipitant includes at least one of sodium hydroxide and potassium hydroxide; optionally, the concentration of the precipitant is 8-12 mol / L;

[0023] (4) The complexing agent includes at least one of ammonia water, ammonium bicarbonate solution, ammonium carbonate solution, EDTA, ethylenediamine, sodium citrate and ammonium sulfate; optionally, the complexing agent is ammonia water with a concentration of 6-14 mol / L;

[0024] (5) The initial pH value of the coprecipitation reaction is 11.00-11.50, and the pH value gradually decreases to 10.00-10.40 during the reaction.

[0025] (6) The initial stirring speed of the coprecipitation reaction is 320-400 rpm, and the stirring speed is gradually reduced to 100-150 rpm during the reaction.

[0026] (7) The initial feed flow rate of the metal salt solution in the co-precipitation reaction is 2-4% / h of the available volume of the reaction vessel, and the feed flow rate of the metal salt solution gradually increases to 7-9% / h of the available volume of the reaction vessel during the reaction process;

[0027] (8) The reaction temperature of the coprecipitation reaction is 30-50℃;

[0028] (9) The ammonia concentration in the co-precipitation reaction is 2-5 g / L;

[0029] (10) The particle size of the intermediate product is 5-6 μm;

[0030] (11) The proportion of the partial mixture relative to the mixture is greater than 0 and less than or equal to 1 / 2.

[0031] In another embodiment of this application, a cathode material is provided, which is prepared from the sodium-ion battery cathode material precursor described in any of the above claims or from the sodium-ion battery cathode material precursor preparation method described in any of the above claims.

[0032] Another embodiment of this application provides a sodium-ion battery prepared from the above-described cathode material.

[0033] Another embodiment of this application provides an electrical device, including the sodium-ion battery described above.

[0034] The sodium-ion battery cathode material precursor provided according to the embodiments of this application includes spherical or near-spherical secondary particles composed of primary particles. Each secondary particle comprises an inner layer, a sub-outer layer, and an outer layer, arranged from the inside out. The inner layer is located closest to the center of the secondary particle, the sub-outer layer covers the inner layer, and the outer layer covers the sub-outer layer. Since the porosity of the inner and sub-outer layers is greater than that of the outer layer, the inner and sub-outer layers are more porous, while the outer layer is more dense. This reduces side reactions of the electrolyte on the surface. Therefore, by forming a cathode material precursor with a more porous interior and a denser exterior, the material's cycle performance is improved. Furthermore, by controlling the porosity of the sub-outer layer within a suitable range, the sub-outer layer can effectively cope with volume changes during charge and discharge, thereby avoiding large fracture pores within the secondary particles that could lead to cracking and structural collapse, further improving cycle performance and safety.

[0035] According to the preparation method provided in the embodiments of this application, by controlling the steps and conditions of the co-precipitation reaction, especially the operation of separating part of the mixture during the reaction, a sodium-ion battery cathode material precursor with a relatively loose interior, a relatively dense exterior, and a porosity of the sub-outer layer within a suitable range can be prepared. This allows the sodium-ion battery cathode material precursor to effectively mitigate the volume change caused by the charging and discharging process, thereby improving cycle performance and safety.

[0036] The cathode material provided in the embodiments of this application is prepared from the sodium-ion battery cathode material precursor in the above embodiments. Based on the performance of the sodium-ion battery cathode material precursor, the obtained sodium-ion battery cathode material has advantages such as good cycle stability.

[0037] Additional technical solutions and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0038] To more clearly illustrate the specific embodiments of this application or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a scanning electron microscope image of the sodium-ion battery cathode material precursor provided in Example 1 of this application;

[0040] Figure 2 This is a cross-sectional electron microscope image of the sodium-ion battery cathode material precursor provided in Example 1 of this application;

[0041] Figure 3This is a cross-sectional electron microscope image of the sodium-ion battery cathode material precursor provided in Example 2 of this application;

[0042] Figure 4 This is a cross-sectional electron microscope image of the sodium-ion battery cathode material precursor provided in Example 3 of this application;

[0043] Figure 5 This is a cross-sectional electron microscope image of the sodium-ion battery cathode material precursor provided in Comparative Example 1 of this application;

[0044] Figure 6 This is a cross-sectional electron microscope image of the sodium-ion battery cathode material precursor provided in Comparative Example 2 of this application;

[0045] Figure 7 This is a scanning electron microscope image of the sodium-ion battery cathode material precursor provided in Comparative Example 3 of this application;

[0046] Figure 8 This is a cross-sectional electron microscope image of the sodium-ion battery cathode material precursor provided in Comparative Example 3 of this application. Detailed Implementation

[0047] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0048] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0049] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0050] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0051] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0052] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0053] This application provides a precursor for a sodium-ion battery cathode material. The precursor comprises secondary particles consisting of multiple primary particles. These secondary particles are spherical or near-spherical and include an inner layer, a sub-outer layer, and an outer layer from the inside out. The porosity of the inner layer and the sub-outer layer is greater than that of the outer layer, with the sub-outer layer having a porosity of 16%-25%. It should be noted that the inner layer can be a single layer or multiple layers. The layers are demarcated by different arrangements of the primary particles. These arrangements include the orientation and density of the primary particles.

[0054] The sodium-ion battery cathode material precursor provided in the embodiments of this application includes spherical or near-spherical secondary particles composed of primary particles. Each secondary particle comprises an inner layer, a sub-outer layer, and an outer layer, arranged from the inside out. The inner layer is located closest to the center of the secondary particle, the sub-outer layer covers the inner layer, and the outer layer covers the sub-outer layer. Since the porosity of the inner and sub-outer layers is greater than that of the outer layer, the inner and sub-outer layers are more porous, while the outer layer is more dense. This reduces side reactions of the electrolyte on the surface. Therefore, by forming a cathode material precursor with a more porous interior and a denser exterior, the material's cycle performance is improved. Furthermore, by controlling the porosity of the sub-outer layer within a suitable range, the sub-outer layer can effectively cope with volume changes, thereby avoiding large fracture pores within the secondary particles that could lead to cracking and structural collapse, further improving cycle performance and safety.

[0055] For example, the porosity of the sub-outer layer can be any value between 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, or 16%-25%.

[0056] In some embodiments, the radius of the inner layer is greater than or equal to the thickness of the sub-outer layer. Since the sub-outer layer is relatively porous, if the thickness of the sub-outer layer is too large, large fault pores will appear inside the secondary particles, which will easily lead to structural collapse. By controlling the radius of the inner layer to be greater than or equal to the thickness of the sub-outer layer, the inner, sub-outer and outer layers can be arranged to form secondary particles with a more stable structure, thereby obtaining a cathode material with better cycle stability and thus optimizing the performance of the battery.

[0057] To further improve the mechanical strength of secondary particles, the thickness of each layer of secondary particles can be optimized.

[0058] In some embodiments, the radius of the inner layer relative to the radius of the secondary particles is 30%-45%; exemplaryly, the radius of the inner layer relative to the radius of the secondary particles can be any value between 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, or 30%-45%.

[0059] In some embodiments, the thickness of the outermost layer relative to the radius of the secondary particles is 16%-30%; exemplaryly, the thickness of the outermost layer relative to the radius of the secondary particles can be any value between 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or 16%-30%.

[0060] In some embodiments, the thickness of the outer layer relative to the radius of the secondary particles is 25%-40%. Exemplarily, the thickness of the outer layer relative to the radius of the secondary particles can be any value between 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, or 25%-40%.

[0061] By controlling the radius of the inner layer, the thickness of the sub-outer layer, and / or the thickness of the outer layer within the aforementioned suitable ranges, the structure of the secondary particles can be made more stable, which is beneficial for further improving cycle performance and safety.

[0062] In addition, the porosity of each layer of secondary particles can be optimized.

[0063] In some embodiments, the porosity of the inner layer is 10%-25%; exemplaryly, the porosity of the inner layer can be any value between 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, or 10%-25%.

[0064] In some embodiments, the porosity of the outer layer is less than 6%; exemplaryly, the porosity of the outer layer can be any value of 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6% or less than 6%.

[0065] By controlling the porosity of the inner and outer layers within the aforementioned suitable range, with the inner layer having a relatively larger porosity and the outer layer having a relatively smaller porosity, side reactions of the electrolyte on the surface can be reduced, which is beneficial to further improving the cycle performance of the battery.

[0066] In some embodiments, the overall porosity of the secondary particles is 6%-16%, which ensures that the precursor itself has high structural stability and further ensures the cycle performance of the battery. Exemplarily, the overall porosity of the secondary particles can be any value between 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, or 6%-16%.

[0067] In some embodiments, the Span value of the secondary particle size distribution is 0.3-0.6, preferably 0.3-0.5. Wherein, the Span value = (D90-D10) / D50), where D90 refers to the particle size corresponding to a cumulative volume distribution percentage of secondary particles in the sodium-ion battery cathode material precursor reaching 90% or more; D50 refers to the particle size corresponding to a cumulative volume distribution percentage of secondary particles in the sodium-ion battery cathode material precursor reaching 50% or more; and D10 refers to the particle size corresponding to a cumulative volume distribution percentage of secondary particles in the sodium-ion battery cathode material precursor reaching 10% or more. The narrow particle size distribution and uniform size of the secondary particles in the embodiments of this application are beneficial for the precursor to fully react with the sodium source, thereby improving capacity. Exemplarily, the Span value can be any value between 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, or 0.3-0.6.

[0068] In some embodiments, the tap density of the secondary particles is greater than or equal to 1.9 g / cm³. 3 For example, the tap density TD of secondary particles can be 1.9 g / cm³. 3 1.95g / cm 3 2.00g / cm 3 2.05g / cm 3 2.10 g / cm 3 2.15g / cm 3 2.20g / cm 3 Or greater than or equal to 1.9 g / cm³ 3 Any value. By controlling the tap density within a suitable range, it is beneficial to improve the energy density of the battery.

[0069] In some embodiments, the specific surface area of ​​the secondary particles is 7-15 m². 2 / g. For example, the specific surface area BET of secondary particles can be 7m². 2 / g、8m 2 / g、9m 2 / g, 10m 2 / g、11m 2 / g、12m 2 / g、13m 2 / g、14m 2 / g, 15m 2 / g or 7-15m 2 Any value between / g. By controlling the specific surface area within a suitable range, the cathode material can fully contact the electrolyte after preparation, thereby increasing capacity, while reducing side reactions between the cathode material and the electrolyte.

[0070] In some embodiments, the average particle size D50 of the secondary particles is 9-13 μm, which is beneficial for improving the battery energy density. Exemplarily, the average particle size D50 of the secondary particles can be any value between 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, or 9-13 μm.

[0071] In some embodiments, the full width at half maximum (FWHM) of the diffraction peak of the 100-plane of the secondary particle in the X-ray diffraction pattern is 0.35°-0.45°. Exemplarily, the FWHM(100) of the diffraction peak of the 100-plane of the secondary particle in the X-ray diffraction pattern can be any value between 0.35°, 0.36°, 0.37°, 0.38°, 0.39°, 0.40°, 0.41°, 0.42°, 0.43°, 0.44°, 0.45°, or 0.35°-0.45°.

[0072] In some embodiments, the sphericity of the secondary particles is ≥0.90. Higher sphericity of the secondary particles is beneficial for maintaining their structural stability and can effectively improve the filling capacity of the positive electrode active material, thereby improving battery cycle stability, discharge capacity, and charge / discharge efficiency. In particular, large-particle precursors with good sphericity are more conducive to improving battery energy density and stability. Exemplarily, the sphericity of the secondary particles can be any value of 0.90, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.00, or greater than 0.90.

[0073] In some embodiments, the primary particles are arranged radially along the radial direction of the secondary particles. In the embodiments of this application, the primary particles constituting the inner layer, the sub-outer layer, and the outer layer grow radially along the radial direction of the secondary particles, which is beneficial to improving the conductivity of sodium ions, thereby improving the cycle performance and charge / discharge efficiency of the battery.

[0074] In some embodiments, the general chemical formula of the sodium-ion battery cathode material precursor is Ni. x M y Me z (OH)2, wherein M is selected from at least one of Fe, Mn, Zn, Mg, and Al, and Me is selected from at least one of Cu, Zr, Ca, Y, Ce, and Ti, 0.2≤x≤0.4, 0.6≤y≤0.8, 0≤z≤0.04, and x, y, and z are all molar percentages.

[0075] Another embodiment of this application provides a method for preparing a precursor of a sodium-ion battery cathode material, comprising the following steps: mixing a solvent, a complexing agent, and a precipitant to obtain a base liquid; adding a metal salt solution, a complexing agent, and a precipitant to the base liquid to perform a co-precipitation reaction to obtain a mixture containing an intermediate product; then separating a portion of the mixture and continuing to add a metal salt solution, a complexing agent, and a precipitant to the remaining mixture to perform a co-precipitation reaction to obtain a reaction product; and post-processing the reaction product to obtain the precursor of the sodium-ion battery cathode material.

[0076] According to the preparation method provided in the embodiments of this application, by controlling the steps and conditions of the co-precipitation reaction, especially the operation of separating part of the mixture during the reaction, the spacing between primary particles will increase, resulting in a looser connecting layer. This allows the sodium-ion battery cathode material precursor to effectively alleviate the volume change caused by sodium ion insertion and extraction, and reduce electrolyte penetration, thereby improving cycle performance and safety.

[0077] In some embodiments, the metal salt includes soluble salts of Ni, M, and Me, wherein M is selected from at least one of Fe, Mn, Zn, Mg, and Al, and Me is selected from at least one of Cu, Zr, Ca, Y, Ce, and Ti; in some embodiments, the soluble salt includes at least one of sulfate, nitrate, acetate, and chloride. By selecting appropriate types of metal salts, sodium-ion battery cathode material precursors containing specific doped elements can be prepared.

[0078] In some embodiments, the total concentration of metal ions in the metal salt solution is 1-5 mol / L. Exemplarily, the total concentration of metal ions in the metal salt solution can be any value between 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, or 1-5 mol / L.

[0079] In some embodiments, the precipitant includes at least one of sodium hydroxide and potassium hydroxide; in some embodiments, the concentration of the precipitant is 8-12 mol / L. In some embodiments, the complexing agent includes at least one of ammonia, ammonium bicarbonate solution, ammonium carbonate solution, EDTA, ethylenediamine, sodium citrate, and ammonium sulfate; in some embodiments, the complexing agent is ammonia with a concentration of 6-14 mol / L.

[0080] In some embodiments, the initial pH of the coprecipitation reaction is 11.00-11.50, and the pH gradually decreases to 10.00-10.40 during the reaction.

[0081] In some embodiments, the initial stirring speed of the coprecipitation reaction is 320-400 rpm, and the stirring speed is gradually reduced to 100-150 rpm during the reaction.

[0082] In some embodiments, the initial feed flow rate of the metal salt solution for the co-precipitation reaction is 2-4% / h of the available volume of the reaction vessel, and the feed flow rate of the metal salt solution is gradually increased to 7-9% / h of the available volume of the reaction vessel during the reaction.

[0083] In some embodiments, the reaction temperature of the coprecipitation reaction is 30-50°C. In some embodiments, the ammonia concentration in the coprecipitation reaction is 2-5 g / L.

[0084] Due to the characteristics of the elements, the preparation of precursors with the morphological features of this application requires high-level processing techniques, for example, Fe. 2+ The precipitation rate is relatively fast, and it is easily oxidized to Fe. 3+ At the same time, ammonia water and Fe 2+ Its complexing ability is weak, and it is easy to cause segregation if the process parameters do not meet the requirements. Therefore, the adjustable range of process parameters is narrow, and the actual synthesis process requires high control precision.

[0085] By controlling the reaction conditions of the co-precipitation reaction within the aforementioned suitable range, and precisely controlling the process conditions of the synthesis process, it is beneficial to obtain sodium-ion battery cathode material precursors with good sphericity, relatively loose internal secondary particles, relatively dense external particles, and suitable porosity, thereby improving the cycle performance and safety of the corresponding batteries.

[0086] In some embodiments, the intermediate product has a particle size of 5-6 μm during the co-precipitation reaction. After obtaining the intermediate product with a particle size of 5-6 μm, a portion of the mixture is separated, and the remaining mixture is allowed to continue reacting, thereby forming a sodium-ion battery cathode material precursor with an inner layer, a sub-outer layer, and an outer layer structure that meets the target requirements layer by layer.

[0087] In some embodiments, the proportion of a portion of the mixture relative to the total mixture is greater than 0 and less than or equal to 1 / 2.

[0088] In some embodiments, the post-processing includes: separating the reaction product into a solid and liquid phase to obtain a solid, and then washing it with alkali, water, and drying it to obtain a sodium-ion battery cathode material precursor.

[0089] Another embodiment of this application provides a cathode material, prepared from any of the sodium-ion battery cathode material precursors described above or by any of the sodium-ion battery cathode material precursor preparation methods described above. The cathode material provided according to this application embodiment is prepared from the sodium-ion battery cathode material precursors described in the above embodiments. Based on the performance of the sodium-ion battery cathode material precursor, the obtained sodium-ion battery cathode material has advantages such as high capacity and good cycle stability.

[0090] For example, the method for preparing the cathode material includes mixing the obtained sodium-ion battery cathode material precursor with a sodium source, wherein the molar ratio of the sum of metal elements in the sodium-ion battery cathode material precursor to the sodium source is 1:(1.02-1.07); after mixing, the temperature is raised to 780-880℃ at a heating rate of 1-3℃ / min and calcined for 10-20 hours to obtain the sodium-ion battery cathode material.

[0091] Another embodiment of this application provides a sodium-ion battery prepared from the above-described positive electrode material.

[0092] Another embodiment of this application provides an electrical device including the sodium-ion battery described above.

[0093] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all reagents and raw materials used in the following embodiments are commercially available or synthesized by conventional methods, and the instruments used in the embodiments are also commercially available.

[0094] The test methods for testing the products involved in the following embodiments and comparative examples are described below:

[0095] 1. Span and particle size were tested using a Malvern 3000 laser particle size analyzer, referring to standard GB / T 19077-2016;

[0096] 2. The test reference standard for TD is GB / T 5162-2021, "Determination of Tap Density of Metal Powders";

[0097] 3. XRD was measured using an X-ray diffractometer, in accordance with standard GA / T 2079-2023;

[0098] 4. Sphericity and porosity were measured using Metis software;

[0099] 5. Specific surface area is determined according to GB / T 19587-2017 Gas Adsorption BET Method for Solid Substances.

[0100] Example 1

[0101] This embodiment provides a precursor for a sodium-ion battery cathode material, with the general chemical formula Ni. 0.33 Mn 0.33 Fe 0.34 (OH)₂. The preparation methods of sodium-ion battery cathode material precursors and cathode materials include:

[0102] Raw material preparation: Sulfate was used as raw material to prepare a nickel-iron-manganese metal salt solution with a total metal ion concentration of 2 mol / L, a sodium hydroxide solution with a concentration of 10 mol / L was prepared as a precipitant, and ammonia water with a concentration of 8 mol / L was prepared as a complexing agent.

[0103] Coprecipitation reaction: Water, sodium hydroxide solution, and ammonia solution were added to a reaction vessel and mixed to obtain a base liquid. The stirring frequency was increased to 320 rpm, and the temperature was increased to 45℃. The initial pH value of the reaction was 11.00, and the ammonia concentration was 3.5 g / L. Nitrogen gas was continuously purged into the reaction vessel during the reaction. Then, nickel-iron-manganese metal salt solution, sodium hydroxide solution, and ammonia water were added to the reaction vessel to carry out the coprecipitation reaction. During the reaction, the pH value was gradually reduced to 10.25, and the ammonia concentration was maintained at 3.5 g / L throughout. The feed flow rate of the metal salt solution was gradually increased from 2% / h of the usable volume of the reaction vessel to 7% / h, and the stirring frequency was gradually reduced to 100 rpm. During the reaction, when the particle size D50 of the slurry in the reaction vessel was 5.5 μm, 1 / 5 of the slurry was separated, and the remaining 4 / 5 continued to react until the particle size D50 of the slurry in the reaction vessel was about 10.5 μm, at which point the feeding was stopped.

[0104] Post-processing: The above slurry was subjected to solid-liquid separation, and the separated precipitate was centrifuged and washed. First, it was washed with sodium hydroxide solution for alkaline washing, followed by washing with deionized water. After centrifugation, the centrifuged material was placed in a forced-air drying oven and dried for 10 hours. After drying, it was sieved and demagnetized, and finally sealed and stored to obtain the precursor of sodium-ion battery cathode material with the general chemical formula Ni. 0.33 Mn 0.33 Fe 0.34 (OH)2, the scanning electron microscope (SEM) image and cross-sectional SEM image are shown below. Figure 1 and Figure 2 As shown.

[0105] Preparation of cathode material: The obtained nickel-iron-manganese-sodium ion battery cathode material precursor was mixed with sodium carbonate, and the elemental molar ratio was (Ni+Fe+Mn):Na=1:1.05; after mixing, it was calcined in a muffle furnace at a heating rate of 1℃ / min for 12h at 850℃ to obtain the cathode material.

[0106] Example 2

[0107] This embodiment provides a precursor for a sodium-ion battery cathode material, with the general chemical formula Ni. 0.30 Fe 0.30 Mn 0.30 Mg 0.10(OH)2. The difference between the sodium-ion battery cathode material precursor and the cathode material preparation method in this embodiment and those in Example 1 is that: (1) In the raw material preparation step, the types and proportions of metal elements contained in the metal salt solution are different; (2) In the co-precipitation reaction step, the pH value is gradually reduced to 10.00 during the reaction, the stirring speed is gradually reduced to 120 rpm during the reaction, and the reaction temperature is 30℃.

[0108] The cross-sectional electron microscope image of the obtained sodium-ion battery cathode material precursor is shown below. Figure 3 As shown.

[0109] Example 3

[0110] This embodiment provides a precursor for a sodium-ion battery cathode material, with the general chemical formula Ni. 0.30 Fe 0.30 Mn 0.30 Al 0.10 (OH)2. The difference between the sodium-ion battery cathode material precursor and the cathode material preparation method in this embodiment and those in Example 1 is as follows: (1) In the raw material preparation step: the types and proportions of metal elements contained in the metal salt solution are different, 6 mol / L ammonia water is used as a complexing agent, and the total concentration of metal ions in the metal salt solution is 1 mol / L; (2) In the co-precipitation reaction step: the pH value gradually decreases to 10.40 during the reaction process, and the feed flow rate of the metal salt solution gradually increases from 2% / h of the available volume of the reactor to 5% / h.

[0111] The cross-sectional electron microscope image of the obtained sodium-ion battery cathode material precursor is shown below. Figure 4 As shown.

[0112] Example 4

[0113] This embodiment provides a precursor for a sodium-ion battery cathode material, with the general chemical formula Ni. 0.33 Mn 0.33 Fe 0.34 (OH)2. The difference between the sodium-ion battery cathode material precursor and the cathode material preparation method in this embodiment and those in Example 1 is that: (1) In the raw material preparation: 12 mol / L sodium hydroxide solution is used as a precipitant; (2) In the co-precipitation reaction step: the ammonia concentration is 2 g / L, and the feed flow rate of the metal salt solution is gradually increased from 4% / h of the available volume of the reactor to 9% / h.

[0114] Comparative Example 1

[0115] This comparative example provides a precursor for a sodium-ion battery cathode material with the general chemical formula Ni. 0.33 Mn 0.33 Fe 0.34(OH)2. The difference between the sodium-ion battery cathode material precursor and the preparation method of the cathode material in this comparative example and Example 1 is that no slurry separation operation is performed during the co-precipitation reaction.

[0116] The cross-sectional electron microscope image of the obtained sodium-ion battery cathode material precursor is shown below. Figure 5 As shown.

[0117] Comparative Example 2

[0118] This comparative example provides a precursor for a sodium-ion battery cathode material with the general chemical formula Ni. 0.33 Mn 0.33 Fe 0.34 (OH)2. The difference between the sodium-ion battery cathode material precursor and the cathode material preparation method in this comparative example and Example 1 is that during the co-precipitation reaction, when the particle size D50 of the slurry in the reactor is 3.5 μm, 3 / 5 of the slurry is separated, and the remaining 2 / 5 continues to react.

[0119] The cross-sectional electron microscope image of the obtained sodium-ion battery cathode material precursor is shown below. Figure 6 As shown.

[0120] Comparative Example 3

[0121] This comparative example provides a precursor for a sodium-ion battery cathode material with the general chemical formula Ni. 0.33 Mn 0.33 Fe 0.34 (OH)2. The difference between the sodium-ion battery cathode material precursor and the cathode material preparation method in this comparative example and Example 1 is only that: during the co-precipitation reaction, when the particle size D50 of the slurry in the reactor is 3.5 μm, 1 / 5 of the slurry is separated, and the remaining 4 / 5 continues to react.

[0122] The scanning electron microscope (SEM) images and cross-sectional SEM images of the obtained sodium-ion battery cathode material precursor are shown below. Figure 7 and Figure 8 As shown.

[0123] Table 1. Layer thickness and porosity of the precursors in each embodiment and comparative example.

[0124]

[0125] Table 2. Physicochemical properties of precursors for each embodiment and comparative example.

[0126]

[0127] Test section

[0128] Samples prepared in all examples and comparative examples were used as positive electrode materials. The positive electrode material, polyvinylidene fluoride, and acetylene black were mixed in a mass ratio of 8:1:1, N-methyl-pyrrolidone was added, and then the mixture was uniformly coated onto aluminum foil as the current collector to serve as the positive electrode. After drying, in a glove box, a sodium metal sheet was used as the negative electrode, a 1 mol / L NaClO4 solution as the electrolyte, and glass fiber as the separator to assemble a CR2032 coin cell. First, it was activated by charge-discharge for 2 weeks at a current density of 0.1C (1C = 150 mAh / g), then by charge-discharge for 2 weeks at a current density of 0.2C, and finally by charge-discharge for 50 weeks at a current density of 1C. The charging cutoff voltage was 4.0V, and the discharging cutoff voltage was 4.0V.

[0129] Table 3 Electrochemical performance of the batteries corresponding to the precursors of each embodiment and comparative example.

[0130]

[0131] according to Figures 1 to 4 As can be seen, the secondary particles of the sodium-ion battery cathode material precursor in this application embodiment include an inner layer, a sub-outer layer, and an outer layer from the inside out, with the inner and sub-outer layers being relatively loose and the outer layer being relatively dense. Referring again to Tables 1 to 3, the batteries corresponding to Examples 1 to 4 of this application have a 1C discharge specific capacity exceeding 136.5 mAh / g and a capacity retention rate exceeding 91.49% after 50 cycles. It is evident that using the sodium-ion battery cathode material precursor in this application embodiment can enable the battery to have good electrochemical performance.

[0132] according to Figure 5 It is evident that in Comparative Example 1, no slurry separation was performed during the co-precipitation reaction. The resulting sodium-ion battery cathode material precursor had relatively dense secondary particles without any loose layers, and its internal structure was significantly different from that of the examples. According to... Figure 6 As can be seen, in Comparative Example 2, when the particle size D50 of the slurry in the reactor is 3.5 μm during the co-precipitation reaction, 3 / 5 of the slurry is separated, and the remaining 2 / 5 continues to react. The resulting secondary particles of the sodium-ion battery cathode material precursor show obvious internal fractures, and their internal structure is significantly different from that of the example. According to... Figure 7 and Figure 8 As can be seen, in Comparative Example 3, when the particle size D50 of the slurry in the reactor is 3.5 μm during the co-precipitation reaction, 1 / 5 of the slurry is separated, and the remaining 4 / 5 continues to react. The resulting secondary particles of the sodium-ion battery cathode material precursor exhibit internal fractures, and their internal structure is significantly different from that of the examples. Referring further to Tables 1 to 3, it can be seen that the 1C discharge specific capacity and 50-cycle capacity retention of the batteries in Comparative Examples 1-3 are worse than those in Example 1. Therefore, the sodium-ion battery cathode material precursor provided according to the embodiments of this application has better performance.

[0133] The technical features described above can be combined arbitrarily. Although not all possible combinations of these technical features are described, any combination of these technical features should be considered to be covered by this specification, provided that such combination does not contain contradictions.

[0134] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A precursor for a sodium-ion battery cathode material, characterized in that, The sodium-ion battery cathode material precursor includes secondary particles composed of multiple primary particles. The secondary particles are spherical or near-spherical and include an inner layer, a sub-outer layer, and an outer layer from the inside out. The porosity of the inner layer and the sub-outer layer are both greater than the porosity of the outer layer, and the porosity of the sub-outer layer is 16%-25%.

2. The sodium-ion battery cathode material precursor according to claim 1, characterized in that, The radius of the inner layer is greater than or equal to the thickness of the sub-outer layer.

3. The sodium-ion battery cathode material precursor according to claim 1 or 2, characterized in that, The radius of the inner layer is 30%-45% of the radius of the secondary particles; and / or The thickness of the outermost layer is 16%-30% of the radius of the secondary particles; and / or The thickness of the outer layer is 25%-40% of the radius of the secondary particles.

4. The sodium-ion battery cathode material precursor according to claim 1 or 2, characterized in that, The porosity of the inner layer is 10%-25%; and / or The porosity of the outer layer is less than 6%; and / or The overall porosity of the secondary particles is 6%-16%.

5. The sodium-ion battery cathode material precursor according to claim 1, characterized in that, The sodium-ion battery cathode material precursor satisfies at least one of the following conditions: a. The particle size distribution span value of the secondary particles is 0.3-0.6, preferably 0.3-0.5; b. The tap density of the secondary particles is greater than or equal to 1.9 g / cm³. 3 ; c. The specific surface area of ​​the secondary particles is 7-15 m². 2 / g; d. The average particle size D50 of the secondary particles is 9-13 μm; e. The full width at half maximum (FWHM) of the diffraction peak of the 100 crystal plane of the secondary particles in the X-ray diffraction pattern is 0.35°-0.45°; f. The sphericity of the secondary particles is ≥0.90; g. The primary particles are arranged radially along the radial direction of the secondary particles; h. The general chemical formula of the sodium-ion battery cathode material precursor is Ni x M y Me z (OH)2, wherein M is selected from at least one of Fe, Mn, Zn, Mg, and Al, Me is selected from at least one of Cu, Zr, Ca, Y, Ce, and Ti, and 0.2≤x≤0.4, 0.6≤y≤0.8, and 0≤z≤0.

04.

6. A method for preparing a precursor for a sodium-ion battery cathode material, characterized in that, Includes the following steps: The solvent, complexing agent, and precipitant are mixed to obtain the base liquid; A metal salt solution, complexing agent, and precipitant are added to the base liquid to carry out a coprecipitation reaction to obtain a mixture containing intermediate products. Then, a portion of the mixture is separated, and a metal salt solution, complexing agent, and precipitant are added to the remaining mixture to carry out a coprecipitation reaction to obtain the reaction product. The reaction products were post-processed to obtain a precursor for sodium-ion battery cathode material.

7. The method for preparing the sodium-ion battery cathode material precursor according to claim 6, characterized in that, The preparation method satisfies at least one of the following conditions (1)-(11): (1) The metal salt includes soluble salts of Ni, M and Me, wherein M is selected from at least one of Fe, Mn, Zn, Mg and Al, and Me is selected from at least one of Cu, Zr, Ca, Y, Ce and Ti; optionally, the soluble salt includes at least one of sulfate, nitrate, acetate and chloride. (2) The total concentration of metal ions in the metal salt solution is 1-5 mol / L; (3) The precipitant includes at least one of sodium hydroxide and potassium hydroxide; optionally, the concentration of the precipitant is 8-12 mol / L; (4) The complexing agent includes at least one of ammonia water, ammonium bicarbonate solution, ammonium carbonate solution, EDTA, ethylenediamine, sodium citrate and ammonium sulfate; optionally, the complexing agent is ammonia water with a concentration of 6-14 mol / L; (5) The initial pH value of the coprecipitation reaction is 11.00-11.50, and the pH value gradually decreases to 10.00-10.40 during the reaction. (6) The initial stirring speed of the coprecipitation reaction is 320-400 rpm, and the stirring speed is gradually reduced to 100-150 rpm during the reaction. (7) The initial feed flow rate of the metal salt solution in the co-precipitation reaction is 2-4% / h of the available volume of the reaction vessel, and the feed flow rate of the metal salt solution gradually increases to 7-9% / h of the available volume of the reaction vessel during the reaction process; (8) The reaction temperature of the coprecipitation reaction is 30-50℃; (9) The ammonia concentration in the co-precipitation reaction is 2-5 g / L; (10) The particle size of the intermediate product is 5-6 μm; (11) The proportion of the partial mixture relative to the mixture is greater than 0 and less than or equal to 1 / 2.

8. A positive electrode material, characterized in that, It is prepared by the sodium-ion battery cathode material precursor according to any one of claims 1 to 5 or by the sodium-ion battery cathode material precursor preparation method according to any one of claims 6 to 7.

9. A sodium-ion battery, characterized in that, It is prepared from the cathode material described in claim 8.

10. An electrical-related device, characterized in that, Including the sodium-ion battery as described in claim 9.

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