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

Abstract

The application discloses a sodium ion battery positive electrode material, a preparation method thereof and a sodium ion battery. The sodium ion battery positive electrode material precursor comprises an inner core and a coating film arranged on the surface of the inner core. The chemical general formula of the inner core is Mg x Fe y Mn z M (1‑x‑y‑z) (OH)2, and the chemical formula of the coating film is Al(OH)3, wherein 0.05<=x<=0.20, 0.20<=y<=0.50, 0.30<=z<=0.60, and M is selected from at least one of W, Cr, Zr, Ti, V, Cd, Cu, Co and Ni. The sodium ion battery positive electrode material provided by the application has high gram capacity, and the battery has excellent long cycle performance and rate performance when working in the voltage range of 2.5V-4.35V.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium ion battery materials and relates to a sodium ion battery positive electrode material and a preparation method thereof, and a sodium ion battery. Background Art

[0002] Lithium-ion batteries, with their high energy density and long cycle life, have been widely used in electronic devices. In recent years, lithium-ion batteries have been expanding into areas such as large-scale energy storage grids and electric vehicles. However, due to the limited and uneven distribution of lithium resources, the problem of high raw material costs has become increasingly prominent.

[0003] Similar to lithium-ion batteries, secondary sodium-ion batteries have become a key development area in the energy storage field due to their low cost, non-toxicity, and abundant and evenly distributed sodium resources. Like lithium-ion batteries, the energy storage performance of sodium-ion batteries is primarily influenced by the cathode material. Therefore, there is an urgent need to find a cathode material with high energy density, low cost, and long cycle life.

[0004] Sodium-ion battery cathode materials primarily include Prussian blue compounds, layered oxides, tunnel oxides, and polyanionic compounds. Layered metal oxides have attracted widespread attention due to their high specific capacity, simple preparation, and low production cost. Unlike lithium-ion batteries, transition metal elements such as Ti, V, Cr, Mn, Fe, Co, Ni, and Cu in sodium-ion battery layered oxide cathodes are electrochemically active. Due to cost considerations, iron- and manganese-based cathode materials are being researched for practical application.

[0005] Patent CN104617288A prepares copper-iron-manganese layered oxide positive electrode materials through a solid-phase method. The prepared copper-iron-manganese layered oxide positive electrode materials have an initial discharge capacity of 80 mAh / g at a charge and discharge rate of 0.1C within the voltage range of 2.5V to 4.2V. Patent CN115295787A prepares nickel-iron-manganese layered oxide positive electrode materials through a coprecipitation + high-temperature solid-phase method. The prepared nickel-iron-manganese layered oxide positive electrode materials have an initial discharge capacity of up to 198 mAh / g at a charge and discharge rate of 0.1C within the voltage range of 1.5V to 4.2V.

[0006] Although the above two layered transition metal oxide cathode materials have advantages in cost and energy density, their cycle performance is not ideal (<5000 times, 80% capacity), and cannot meet the application of sodium ion batteries in the energy storage field.

[0007] Therefore, it is necessary to provide a sodium ion battery positive electrode material that has excellent long cycle performance without reducing the material's gram capacity. Summary of the Invention

[0008] In response to the above-mentioned problems existing in the prior art, the present invention aims to provide a sodium ion battery positive electrode material, a preparation method thereof, and a sodium ion battery. The sodium ion battery positive electrode material provided by the present invention is doped with magnesium ions and M ions and coated with an alumina coating, so that the sodium ion battery material has a high specific capacity and exhibits excellent long-cycle performance and rate performance when the battery operates in the voltage range of 2.5V to 4.35V.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a sodium ion battery positive electrode material precursor, the sodium ion battery positive electrode material precursor comprising a core and a coating film disposed on the surface of the core, the chemical formula of the core being Mg x Fe y Mn z M (1-x-y-z) (OH)2, the chemical formula of the coating film is Al(OH)3, wherein 0.05≤x≤0.20, 0.20≤y≤0.50, 0.30≤z≤0.60, and M is selected from at least one of W, Cr, Zr, Ti, V, Cd, Cu, Co and Ni.

[0011] In the present invention, k may be, for example, 0.4, 0.5, 0.6, 0.8, 1.0, or 1.2. x may be, for example, 0.05, 0.10, 0.15, or 0.20. y may be, for example, 0.20, 0.25, 0.30, 0.40, or 0.50. z may be, for example, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, or 0.60.

[0012] The present invention introduces Mg element in the precursor co-precipitation stage. Compared with conventional manganese-based positive electrode materials, the material gram capacity is slightly reduced, but it shows excellent cycle performance and rate performance. 2+ with Ni 2+With similar ionic radius and ionic valence, replacing Ni with Mg in manganese-based positive electrode materials can improve material performance while significantly reducing costs; the introduction of magnesium can make the charge and discharge curve smoother, and improve the cycle performance and rate performance. In addition, the presence of Mg can effectively inhibit the P2-O2 phase transition and maintain the triangular prism P2 stacking structure during the cycle, thereby greatly improving the structural stability of the positive electrode material and thus improving the cycle performance. The doping of the M element can not only provide a certain reversible capacity for the battery, but also improve the structural stability of the material, thereby improving the capacity and cycle performance. The coating film is converted into an Al2O3 film in the positive electrode material, which has good uniformity and can protect the positive electrode active components from reacting with the electrolyte during the cycle, thereby further improving the cycle performance of the positive electrode material.

[0013] The sodium ion battery positive electrode material precursor provided by the present invention is doped with magnesium ions and M ions and coated with an alumina coating film, so that the sodium ion battery positive electrode material prepared using the precursor has a high gram capacity, and the battery exhibits excellent long cycle performance and rate performance when operating in the voltage range of 2.5V to 4.35V.

[0014] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0015] Preferably, M is at least one of W and Zr, preferably a combination of W and Zr, and the molar ratio of W to Zr is 1:(3-6), for example, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5 or 1:6.

[0016] Preferably, the particle size D50 of the core is 4 μm to 9 μm, for example, 4 μm, 5 μm, 6 μm, 6.5 μm, 7 μm, 8 μm or 9 μm.

[0017] In a second aspect, the present invention provides a method for preparing a precursor of a positive electrode material for a sodium ion battery as described in the first aspect, the method comprising the following steps:

[0018] (1) mixing a magnesium-iron-manganese mixed salt solution with a salt solution of M to obtain a first metal salt solution;

[0019] (2) adding the first metal salt solution, the precipitant solution, and the complexing agent to the bottom liquid in parallel to perform a coprecipitation reaction to obtain a mixed solution;

[0020] (3) adding the aluminum salt solution, the precipitant solution and the complexing agent to the mixed solution in parallel to carry out a coprecipitation reaction, aging and separating to obtain a precursor of the positive electrode material for a sodium ion battery.

[0021] The present invention rationally regulates the preparation process of a sodium-ion battery cathode material precursor, ensuring a uniform distribution of Mg in the precursor's core and a uniform doping of M with aluminum hydroxide. This precursor can be used to produce a high-performance sodium-ion battery cathode material with a high gram capacity. The battery exhibits excellent long-cycle performance and rate capability when operating in the 2.5V to 4.35V voltage range.

[0022] The present invention directly dopes Mg and M elements in the precursor co-precipitation stage, which can simplify the preparation process of the positive electrode material and reduce the cost of material preparation compared with doping during the sintering process.

[0023] Preferably, the total concentration of metal ions in the first metal salt solution in step (1) is 0.5 mol / L to 5 mol / L, for example, 0.5 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 4 mol / L or 5 mol / L.

[0024] Preferably, the concentration of the precipitant solution in step (2) is 2 mol / L to 15 mol / L, for example, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L, 12 mol / L, 13 mol / L, 14 mol / L or 15 mol / L, etc.

[0025] Preferably, the feed rate of the precipitant solution in step (2) is 1 L / h to 20 L / h, for example, 1 L / h, 2 L / h, 3 L / h, 4 L / h, 5 L / h, 6 L / h, 7 L / h, 8 L / h, 9 L / h, 10 L / h, 12 L / h, 13 L / h, 15 L / h, 16 L / h, 17 L / h, 18 L / h or 20 L / h, etc.

[0026] Preferably, the concentration of the complexing agent solution in step (2) is 4 mol / L to 12 mol / L, for example, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 10 mol / L, 11 mol / L or 12 mol / L.

[0027] Preferably, the feeding rate of the complexing agent solution in step (2) is 0.5 L / h to 10 L / h, for example, 0.5 L / h, 1 L / h, 2 L / h, 3 L / h, 4 L / h, 5 L / h, 6 L / h, 7 L / h, 8 L / h, 9 L / h or 10 L / h, etc.

[0028] Preferably, the pH value of the base solution in step (2) is between 9.0 and 13.0, for example, 9.0, 10.0, 11.0, 11.1, 11.2, 11.3, 11.4, 11.5, 12.0, 12.5 or 13.0, and the concentration of the complexing agent is 0.1 mol / L to 0.5 mol / L, for example, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L or 0.5 mol / L, etc.

[0029] Preferably, during the parallel addition in step (2), the feed rate of the first metal salt solution is 4 L / h to 100 L / h, for example, 4 L / h, 10 L / h, 15 L / h, 18 L / h, 20 L / h, 23 L / h, 26 L / h, 28 L / h, 30 L / h, 35 L / h, 40 L / h, 45 L / h, 50 L / h, 60 L / h, 70 L / h, 80 L / h, 90 L / h or 100 L / h, etc.

[0030] Preferably, during the parallel addition in step (2), the flow rates of the precipitant solution and the complexing agent are controlled so that the pH value of the reaction system is between 10.4 and 11.0 (for example, 10.4, 10.5, 10.6, 10.7, 10.8 or 11.0, etc.), and the concentration of the complexing agent is between 0.30 mol / L and 0.50 mol / L (for example, 0.30 mol / L, 0.32 mol / L, 0.35 mol / L, 0.37 mol / L, 0.40 mol / L, 0.45 mol / L or 0.50 mol / L, etc.).

[0031] Preferably, the coprecipitation reaction in step (2) is carried out under the protection of a protective gas. The present invention does not limit the type of the protective gas, for example, it can be at least one of nitrogen, argon or helium.

[0032] Preferably, the temperature of the coprecipitation reaction in step (2) is 40°C to 80°C, for example, 40°C, 42°C, 45°C, 47°C, 50°C, 53°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C; and the time of the coprecipitation reaction is 30h to 60h, for example, 30h, 33h, 36h, 40h, 45h, 50h, 55h or 60h.

[0033] Preferably, the concentration of aluminum ions in the aluminum salt solution in step (3) is 0.2 mol / L to 5 mol / L, for example, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L or 5 mol / L.

[0034] Preferably, the feeding rate of the aluminum salt solution in step (3) is 10 L / h to 20 L / h, for example, 10 L / h, 12 L / h, 15 L / h, 18 L / h or 20 L / h.

[0035] Preferably, the concentration of the precipitant solution in step (3) is 2 mol / L to 15 mol / L, for example, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, 12 mol / L, 13 mol / L or 15 mol / L.

[0036] Preferably, the feed rate of the precipitant solution in step (3) is 1 L / h to 20 L / h, for example, 1 L / h, 3 L / h, 5 L / h, 7 L / h, 10 L / h, 12.5 L / h, 15 L / h, 17 L / h or 20 L / h, etc.

[0037] Preferably, the concentration of the complexing agent solution in step (3) is 4 mol / L to 12 mol / L, for example, 4 mol / L, 6 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L or 12 mol / L.

[0038] Preferably, the feeding rate of the complexing agent solution in step (3) is 0.5 L / h to 10 L / h, for example, 0.5 L / h, 1 L / h, 2 L / h, 3 L / h, 4 L / h, 5 L / h, 6 L / h, 7 L / h, 8 L / h, 9 L / h or 10 L / h, etc.

[0039] Preferably, during the parallel addition in step (3), the flow rates of the precipitant solution and the complexing agent are controlled so that the pH value of the reaction system is between 9.0 and 13.0 (e.g., 9.0, 9.5, 9.8, 10.0, 10.5, 10.6, 10.7, 10.8, 10.9, 11.0, 11.5, 12.0, 12.5 or 13.0, etc.), preferably between 10.5 and 11.5; the concentration of the complexing agent is between 0 mol / L and 1 mol / L and does not contain 0 mol / L (for example, 0.05mol / L, 0.1mol / L, 0.2mol / L, 0.3mol / L, 0.40mol / L, 0.42mol / L, 0.45mol / L, 0.47mol / L, 0.50mol / L, 0.55mol / L, 0.6mol / L, 0.7mol / L, 0.8mol / L, 0.9mol / L or 1mol / L, etc.), preferably 0.30mol / L to 1mol / L.

[0040] Preferably, the coprecipitation reaction in step (3) is carried out under the protection of a protective gas. The present invention does not limit the type of protective gas, for example, it can be at least one of nitrogen, argon or helium.

[0041] Preferably, the temperature of the coprecipitation reaction in step (3) is 45°C to 55°C, for example, 45°C, 47°C, 50°C, 52°C, 53°C, 54°C or 55°C; and the time of the coprecipitation reaction is 0.5h to 4h, for example, 0.5h, 0.8h, 1h, 1.3h, 1.6h, 2h, 2.5h or 3h.

[0042] Preferably, the average particle size of the product after the coprecipitation reaction in step (3) is D', and the average particle size of the product obtained after the coprecipitation reaction in step (2) is D, D'-D = 0.05 μm to 0.2 μm, for example, 0.05 μm, 0.07 μm, 0.08 μm, 0.1 μm, 0.13 μm, 0.16 μm, 0.18 μm or 0.2 μm, etc.

[0043] As a preferred technical solution of the method of the present invention, the method comprises the following steps:

[0044] S1: mixing the magnesium, iron and manganese mixed salt solution with the salt solution of M to obtain a first metal salt solution with a total metal ion concentration of 0.5 mol / L to 5 mol / L;

[0045] S2: First stage reaction: a first metal salt solution, a 2 mol / L to 15 mol / L sodium hydroxide solution, and a 4 mol / L to 12 mol / L ammonia solution are added in parallel to a base solution having a pH value of 9.0 to 13.0 and an ammonia concentration of 0.1 mol / L to 0.5 mol / L. During the parallel addition process, the feed rate of the first metal salt solution is 4 L / h to 100 L / h. By controlling the flow rates of the sodium hydroxide solution and the ammonia solution, the pH value of the reaction system is controlled to be between 10.4 and 11.0 and the ammonia concentration is controlled to be between 0.30 and 0.50 mol / L. Under nitrogen protection, a coprecipitation reaction is carried out at a reaction temperature of 40° C. to 80° C. The reaction is carried out for 30 h to 60 h. When the average particle size reaches D, the first stage reaction is stopped.

[0046] S3: second stage reaction: adding an aluminum sulfate solution having a total metal ion concentration of 0.2 mol / L to 5 mol / L, a sodium hydroxide solution having a total metal ion concentration of 2 mol / L to 15 mol / L, and a 4 mol / L to 12 mol / L aqueous ammonia solution in parallel to the mixed solution after the first stage reaction, wherein the aluminum sulfate solution is fed at a rate of 10 L / h to 20 L / h during the parallel addition process, and the pH value of the reaction system is controlled to be between 9.0 and 13.0, and the concentration of the complexing agent is controlled to be between 0 mol / L and 1 mol / L and does not contain 0 mol / L by controlling the flow rates of the sodium hydroxide solution and the aqueous ammonia solution, and a coprecipitation reaction is carried out at a reaction temperature of 45° C. to 55° C. under nitrogen protection for 0.5 to 4 hours, and the reaction is stopped when the average particle size reaches D', D'-D=0.05 μm to 0.2 μm;

[0047] S4: Product post-processing: After the reaction is completed, the product is aged for 8 hours, centrifuged and washed, and dried at 100°C to obtain a precursor powder of the positive electrode material for sodium ion batteries.

[0048] In a third aspect, the present invention provides a sodium ion battery positive electrode material, which is prepared using the sodium ion battery positive electrode material precursor described in the first aspect.

[0049] Preferably, the sodium ion battery positive electrode material comprises a positive electrode material core and an aluminum oxide film layer coated on the surface of the positive electrode material core, and the chemical formula of the positive electrode material core is Na k Mg x Fe y Mn z M (1-x-y-z) O2, wherein 0.4≤k≤1.2, 0.05≤x≤0.20, 0.20≤y≤0.50, 0.30≤z≤0.60, and M is selected from at least one of W, Cr, Zr, Ti, V, Cd, Cu, Co and Ni.

[0050] The sodium-ion positive electrode material of the present invention has a uniform distribution of Mg in its core, is doped with M, and has a uniformly distributed Al2O3 film on the surface of the particles in the core. This sodium-ion battery positive electrode material has a high gram capacity and exhibits excellent long-cycle performance and rate capability when the battery operates within a voltage range of 2.5V to 4.35V.

[0051] Preferably, based on the total mass of the sodium ion battery positive electrode material as 100%, the mass proportion of the aluminum oxide film layer is 0% to 3% and does not contain 0%, for example, 0.01%, 0.05%, 0.1%, 0.3%, 0.5%, 0.7%, 1%, 1.3%, 1.5%, 1.8%, 2%, 2.5% or 3%, etc., preferably 0.5% to 1.5%.

[0052] In a fourth aspect, the present invention provides a method for preparing the positive electrode material for a sodium ion battery as described in the third aspect, the method comprising the following steps:

[0053] The sodium salt and the sodium ion battery positive electrode material precursor are mixed and sintered to obtain the sodium ion battery positive electrode material.

[0054] Preferably, the sintering temperature is 700°C to 1200°C, for example, 700°C, 725°C, 750°C, 770°C, 780°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1100°C, 1150°C or 1200°C.

[0055] Preferably, the sintering time is 10 h to 25 h, for example, 10 h, 12 h, 14 h, 15 h, 17 h, 18 h, 20 h, 22 h, 23 h or 25 h.

[0056] In one embodiment, sintering is performed in a tube furnace under oxygen flow.

[0057] In one embodiment, the method further comprises the step of grinding and screening the sintered product.

[0058] In a fifth aspect, the present invention provides a sodium ion battery, comprising the sodium ion battery positive electrode material described in the first aspect.

[0059] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0060] Compared with the prior art, the present invention has the following beneficial effects:

[0061] The sodium ion battery positive electrode material precursor provided by the present invention is doped with magnesium ions and M ions and coated with an alumina coating film, so that the sodium ion battery positive electrode material prepared using the precursor has a high gram capacity, and the battery exhibits excellent long cycle performance and rate performance when operating in the voltage range of 2.5V to 4.35V.

[0062] The present invention rationally regulates the preparation process of a sodium-ion battery cathode material precursor, ensuring a uniform distribution of Mg in the precursor's core and a uniform doping of M with aluminum hydroxide. This precursor can be used to produce a high-performance sodium-ion battery cathode material, exhibiting excellent long-cycle performance and high gram capacity.

[0063] The present invention directly dopes Mg and M elements in the precursor co-precipitation stage, which can simplify the preparation process of the positive electrode material and reduce the cost of material preparation compared with doping during the sintering process. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 This is an SEM image of the positive electrode material precursor prepared in Example 1.

[0065] Figure 2 This is the XRD pattern of the positive electrode material prepared in Example 1. DETAILED DESCRIPTION

[0066] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0067] To facilitate understanding of the present invention, the following examples provide a comprehensive and detailed description of the present invention, but the protection scope of the present invention is not limited to the following specific examples.

[0068] Example 1

[0069] This embodiment provides a doped and coated positive electrode material and a preparation method thereof, the preparation method comprising the following steps:

[0070] (1) First stage reaction: A magnesium-iron-manganese mixed salt solution is mixed with a cobalt sulfate solution to obtain a first metal salt solution with a total metal ion concentration of 2 mol / L and a magnesium-iron-manganese-cobalt molar ratio of 0.10:0.40:0.48:0.02. The first metal salt solution, 10 mol / L sodium hydroxide solution, and 8 mol / L ammonia water are added in parallel to a base liquid with a pH value of 11.3 and an ammonia concentration of 0.2 mol / L. During the parallel addition process, the feed rate of the first metal salt solution is 20 L / h. By controlling the flow rates of the sodium hydroxide solution and ammonia water, the pH value of the reaction system is controlled between 10.4 and 10.7, and the ammonia concentration is controlled between 0.30 and 0.40 mol / L. Under nitrogen protection, a coprecipitation reaction is carried out at a reaction temperature of 52°C. The reaction is continued for 30 hours until the average particle size reaches 4.9 μm, and the first stage reaction is stopped.

[0071] (2) Second stage reaction: Aluminum sulfate solution with a total metal ion concentration of 0.2 mol / L, sodium hydroxide solution of 10 mol / L, and ammonia water of 8 mol / L were added in parallel to the mixed solution after the first stage reaction. During the parallel addition process, the feed rate of aluminum sulfate solution was 20 L / h. By controlling the flow rates of sodium hydroxide solution and ammonia water, the pH value of the reaction system was controlled between 10.6 and 11.0, and the concentration of the complexing agent was controlled between 0.40 and 0.50 mol / L. Under nitrogen protection, the coprecipitation reaction was carried out at a reaction temperature of 52°C for 2 hours. The reaction was stopped when the average particle size reached 5.0 μm.

[0072] (3) Product post-treatment: After the reaction is completed, the product is aged for 8 hours, centrifuged and washed, and dried at 100°C to obtain the positive electrode material precursor powder. The positive electrode material precursor is a core-shell structure, including a core and a coating film coated on the surface of the core. The chemical formula of the core is Mg 0.10 Fe 0.40 Mn 0.48 Co 0.02 (OH)2, the chemical formula of the coating is Al(OH)3.

[0073] (4) High temperature sintering: Sodium carbonate and cathode material precursor powder were weighed and mixed evenly in a molar ratio of 1.03:1, sintered at 900°C for 18 hours, and ground and sieved to obtain a doped and coated cathode material. The doped and coated cathode material includes a cathode material core NaMg 0.10 Fe 0.40 Mn 0.48 Co 0.02 O2 and the aluminum oxide film layer coated on the surface of the positive electrode material core, the chemical formula of the doped coated positive electrode material is NaMg 0.10 Fe 0.40 Mn 0.48 Co 0.02 O2@Al2O3. Based on the total mass of the sodium ion battery positive electrode material being 100%, the mass proportion of the coating film is 1.0%.

[0074] The SEM image of the cathode material precursor prepared in this example is as follows Figure 1 As shown in the figure, it can be seen that the precursor prepared in this example has good sphericity and uniform size, with an average particle size of 5.0 μm.

[0075] The XRD pattern of the positive electrode material prepared in this example is shown in Figure 2 As shown, it can be seen that the obtained positive electrode material has a good P2 layered structure.

[0076] Example 2

[0077] This embodiment provides a doped and coated positive electrode material and a preparation method thereof, the preparation method comprising the following steps:

[0078] (1) First stage reaction: A magnesium-iron-manganese mixed salt solution is mixed with a zirconium sulfate solution to obtain a first metal salt solution with a total metal ion concentration of 1 mol / L and a magnesium-iron-manganese-zirconium molar ratio of 0.05:0.46:0.48:0.01. The first metal salt solution, 10 mol / L sodium hydroxide solution, and 8 mol / L ammonia water are added in parallel to a base solution with a pH value of 11.2 and an ammonia concentration of 0.4 mol / L. During the parallel addition process, the feed rate of the first metal salt solution is 40 L / h. By controlling the flow rates of the sodium hydroxide solution and ammonia water, the pH value of the reaction system is controlled between 10.6 and 10.9, and the ammonia concentration is controlled between 0.40 and 0.50 mol / L. Under nitrogen protection, a coprecipitation reaction is carried out at a reaction temperature of 45°C. The reaction is continued for 60 hours until the average particle size reaches 8.0 μm, and the first stage reaction is stopped.

[0079] (2) Second stage reaction: Aluminum sulfate solution with a total metal ion concentration of 0.5 mol / L, sodium hydroxide solution of 10 mol / L, and ammonia water of 8 mol / L were added in parallel to the mixed solution after the first stage reaction. During the parallel addition process, the feed rate of aluminum sulfate solution was 20 L / h. By controlling the flow rates of sodium hydroxide solution and ammonia water, the pH value of the reaction system was controlled between 10.8 and 11.2, and the concentration of the complexing agent was controlled between 0.45 and 0.55 mol / L. Under nitrogen protection, the coprecipitation reaction was carried out at a reaction temperature of 45°C. The reaction was stopped after 4 hours when the average particle size reached 8.1 μm.

[0080] (3) Product post-treatment: After the reaction is completed, the product is aged for 6 hours, centrifuged and washed, and dried at 100°C to obtain the precursor powder. The positive electrode material precursor is a core-shell structure, including a core and a coating film coated on the surface of the core. The chemical formula of the core is Mg 0.05 Fe 0.46 Mn 0.48 Zr 0.01 (OH)2, the chemical formula of the coating is Al(OH)3.

[0081] (4) High temperature sintering: Sodium carbonate and precursor powder were weighed and mixed evenly according to a molar ratio of 1.03:1, sintered at 880°C for 20 hours, and then ground and sieved to obtain the doped positive electrode material. The doped coated positive electrode material includes a positive electrode material core NaMg 0.05 Fe 0.46 Mn 0.48 Zr 0.01 O2 and the aluminum oxide film layer coated on the surface of the positive electrode material core, the material chemical formula of the doped coated positive electrode material is NaMg 0.05 Fe 0.46 Mn 0.48 Zr 0.01O2@Al2O3. Based on the total mass of the sodium ion battery positive electrode material being 100%, the mass of the coating film accounts for 0.8%.

[0082] Example 3

[0083] This embodiment provides a doped and coated positive electrode material and a preparation method thereof, the preparation method comprising the following steps:

[0084] (1) First stage reaction: A magnesium-iron-manganese mixed salt solution is mixed with a zirconium sulfate solution to obtain a first metal salt solution having a total metal ion concentration of 1.5 mol / L and a magnesium-iron-manganese-zirconium molar ratio of 0.10:0.35:0.52:0.03. The first metal salt solution, 5 mol / L sodium hydroxide solution, and 6 mol / L ammonia water are added in parallel to a base solution having a pH value of 12.0 and an ammonia concentration of 0.3 mol / L. During the parallel addition process, the feed rate of the first metal salt solution is 20 L / h. By controlling the flow rates of the sodium hydroxide solution and ammonia water, the pH value of the reaction system is controlled between 10.8 and 11.0, and the ammonia concentration is controlled between 0.30 and 0.40 mol / L. Under nitrogen protection, a coprecipitation reaction is carried out at a reaction temperature of 60°C for 40 hours. When the average particle size reaches 6.0 μm, the first stage reaction is stopped.

[0085] (2) Second stage reaction: Aluminum sulfate solution with a total metal ion concentration of 0.5 mol / L, sodium hydroxide solution of 5 mol / L, and ammonia water of 6 mol / L were added in parallel to the mixed solution after the first stage reaction. During the parallel addition process, the feed rate of aluminum sulfate solution was 15 L / h. By controlling the flow rates of sodium hydroxide solution and ammonia water, the pH value of the reaction system was controlled between 10.9 and 11.1, and the concentration of the complexing agent was controlled between 0.35 and 0.45 mol / L. Under nitrogen protection, the coprecipitation reaction was carried out at a reaction temperature of 60°C. The reaction was stopped after 3 hours when the average particle size reached 6.2 μm.

[0086] (3) Product post-treatment: After the reaction is completed, the product is aged for 8 hours, centrifuged and washed, and dried at 100°C to obtain the positive electrode material precursor powder. The positive electrode material precursor is a core-shell structure, including a core and a coating film coated on the surface of the core. The chemical formula of the core is Mg 0.10 Fe 0.35 Mn 0.52 Zr 0.03 (OH)2, the chemical formula of the coating is Al(OH)3.

[0087] (4) High temperature sintering: Sodium carbonate and cathode material precursor powder were weighed and mixed evenly in a molar ratio of 1.05:1, sintered at 1000°C for 20 hours, and ground and sieved to obtain a doped cathode material. The doped cathode material includes a cathode material core NaMg 0.10 Fe 0.35 Mn 0.52 Zr 0.03 O2 and the aluminum oxide film layer coated on the surface of the positive electrode material core, the chemical formula of the doped coated positive electrode material is NaMg 0.10 Fe 0.35 Mn 0.52 Zr 0.03 O2@Al2O3. Based on the total mass of the sodium ion battery positive electrode material being 100%, the mass proportion of the coating film is 1.0%.

[0088] Example 4

[0089] This embodiment provides a doped and coated positive electrode material and a preparation method thereof, the preparation method comprising the following steps:

[0090] (1) First stage reaction: A magnesium-iron-manganese mixed salt solution is mixed with a zirconium sulfate solution to obtain a first metal salt solution having a total metal ion concentration of 1.0 mol / L and a magnesium-iron-manganese-zirconium molar ratio of 0.15:0.35:0.4:0.1. The first metal salt solution, 7 mol / L sodium hydroxide solution, and 9 mol / L ammonia water are added in parallel to a base solution having a pH value of 12.5 and an ammonia concentration of 0.2 mol / L. During the parallel addition process, the feed rate of the first metal salt solution is 60 L / h. By controlling the flow rates of the sodium hydroxide solution and ammonia water, the pH value of the reaction system is controlled between 10.5 and 10.8, and the ammonia concentration is controlled between 0.30 and 0.40 mol / L. Under nitrogen protection, a coprecipitation reaction is carried out at a reaction temperature of 70°C. The reaction is continued for 50 hours until the average particle size reaches 7.0 μm, and the first stage reaction is stopped.

[0091] (2) Second stage reaction: Aluminum sulfate solution with a total metal ion concentration of 1.0 mol / L, sodium hydroxide solution of 7.5 mol / L, and ammonia water of 10 mol / L were added in parallel to the mixed solution after the first stage reaction. During the parallel addition process, the feed rate of aluminum sulfate solution was 10 L / h. By controlling the flow rates of sodium hydroxide solution and ammonia water, the pH value of the reaction system was controlled between 11.0 and 11.2, and the concentration of the complexing agent was controlled between 0.60 and 0.70 mol / L. Under nitrogen protection, the coprecipitation reaction was carried out at a reaction temperature of 50°C for 2 hours. The reaction was stopped when the average particle size reached 7.05 μm.

[0092] (3) Product post-treatment: After the reaction is completed, the product is aged for 8 hours, centrifuged and washed, and dried at 100°C to obtain the positive electrode material precursor powder. The positive electrode material precursor is a core-shell structure, including a core and a coating film coated on the surface of the core. The chemical formula of the core is Mg 0.15 Fe 0.35 Mn 0.40 Zr 0.10 (OH)2, the chemical formula of the coating is Al(OH)3.

[0093] (4) High temperature sintering: Sodium carbonate and cathode material precursor powder were weighed and mixed evenly in a molar ratio of 1.04:1, sintered at 850°C for 24 hours, and then ground and sieved to obtain a doped and coated cathode material. The doped and coated cathode material includes a cathode material core NaMg 0.15 Fe 0.35 Mn 0.40 Zr 0.10 O2 and the aluminum oxide film layer coated on the surface of the positive electrode material core, the chemical formula of the doped coated positive electrode material is NaMg 0.15 Fe 0.35 Mn 0.40 Zr 0.10 O2@Al2O3. Based on the total mass of the sodium ion battery positive electrode material being 100%, the mass of the coating film accounts for 1.5%.

[0094] Example 5

[0095] The difference from Example 3 is that zirconium sulfate is replaced by a mixture of zirconium sulfate and tungsten sulfate. In this example, the total molar amount of zirconium and tungsten is equal to the molar amount of zirconium in Example 3, and the molar ratio of tungsten to zirconium is 1:4.

[0096] Example 6

[0097] The difference from Example 3 is that zirconium sulfate is replaced by a mixture of zirconium sulfate and tungsten sulfate. In this example, the total molar amount of zirconium and tungsten is equal to the molar amount of zirconium in Example 3, and the molar ratio of tungsten to zirconium is 2:1.

[0098] Comparative Example 1

[0099] The difference between this comparative example and Example 1 is that no cobalt sulfate solution is added in step (1) of this comparative example.

[0100] The rest of the preparation methods and parameters remained the same as in Example 1.

[0101] Comparative Example 2

[0102] The difference between this comparative example and Example 1 is that the second stage coating reaction is not carried out in step (2) of this comparative example.

[0103] The rest of the preparation methods and parameters remained the same as in Example 1.

[0104] Comparative Example 3

[0105] The difference between this comparative example and Example 1 is that in this comparative example, no cobalt sulfate solution is added in step (1), and the second stage coating reaction is not carried out in step (2).

[0106] The rest of the preparation methods and parameters remained the same as in Example 1.

[0107] test:

[0108] At 25°C, a positive electrode was prepared using the above-prepared positive electrode material as the main positive electrode material (wherein the mass ratio of the main positive electrode material, conductive agent, and binder was 96:2:2, with carbon black as the conductive agent and PVDF as the binder). A sodium metal sheet was used as the negative electrode, and the resulting battery was assembled into a CR2032 button cell. Electrochemical performance was then tested at 0.1C over a voltage range of 2.5-4.35V. The initial discharge capacity and cycling performance are shown in Table 1. The battery was charged at a 0.1C rate and cycled to the fifth cycle at different discharge rates. The discharge capacity results are shown in Table 2.

[0109] Table 1

[0110]

[0111]

[0112] Table 2

[0113]

[0114] It can be seen from the data in the table that in Examples 1-6, the button batteries prepared from the doped and coated sodium ion battery positive electrode material of the present invention can be cycled for more than 3,000 times before the capacity decays to 80% of the initial capacity in the charge and discharge test at 0.1C in the discharge range of 2.5-4.35V; and the discharge capacity at 1C can reach more than 85% of the 0.1C discharge capacity, and the discharge capacity at 5C can reach more than 75% of the 0.1C discharge capacity.

[0115] Conventional cathode materials without doping or coating modification exhibited no more than 2,000 cycles of charge and discharge at 0.1C within the 2.5-4.35V discharge range until their capacity decayed to 80% of their initial capacity. Furthermore, their discharge capacities at 1C and 5C were significantly lower than those of batteries prepared with the doped and coated materials of the present invention. This indicates that sodium-ion batteries prepared with the doped and coated cathode materials of the present invention exhibit superior cycling and rate performance compared to conventional sodium-ion batteries.

[0116] By comparing Example 3 with Examples 5-6, it can be seen that the type of doping element M affects the electrochemical properties of the material. When the combination of W and Zr, especially when the molar ratio of W to Zr is 1:(3-6), the positive electrode material prepared by doping has better cycle performance and rate performance.

[0117] The applicant states that the present invention is intended to illustrate the detailed methods of the present invention through the above-described embodiments, but the present invention is not limited to the above-described detailed methods, that is, it does not mean that the present invention must rely on the above-described detailed methods in order to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for various raw materials in the products of the present invention, addition of auxiliary ingredients, and selection of specific methods, etc., are all within the scope of protection and disclosure of the present invention.

Claims

1. A sodium ion battery cathode material precursor, characterized in that: The sodium ion battery positive electrode material precursor comprises a core and a coating film arranged on the surface of the core, and the chemical formula of the core is Mg x Fe y Mn z M (1-x-y-z) (OH)2, the chemical formula of the coating film is Al(OH)3, wherein 0.05≤x≤0.20, 0.20≤y≤0.50, 0.30≤z≤0.60, M is a combination of W and Zr; the molar ratio of W to Zr is 1:(3-6); The sodium ion battery positive electrode material precursor is prepared by the following method, which comprises the following steps: (1) mixing a magnesium-iron-manganese mixed salt solution with a salt solution of M to obtain a first metal salt solution; (2) adding the first metal salt solution, the precipitant solution, and the complexing agent to the bottom liquid in parallel to perform a coprecipitation reaction to obtain a mixed solution; (3) adding an aluminum salt solution, a precipitant solution, and a complexing agent to the mixed solution in parallel to perform a coprecipitation reaction, and separating after aging to obtain a precursor of a positive electrode material for a sodium ion battery; The total concentration of metal ions in the first metal salt solution in step (1) is 0.5 mol / L to 5 mol / L, and during the parallel addition in step (2), the feed rate of the first metal salt solution is 4 L / h to 100 L / h; The concentration of aluminum ions in the aluminum salt solution in step (3) is 0.2 mol / L to 5 mol / L, and the feeding rate of the aluminum salt solution in step (3) is 10 L / h to 20 L / h.

2. The sodium ion battery cathode material precursor according to claim 1, characterized in that The particle size D50 of the core is 4 μm to 9 μm.

3. A method for preparing a precursor of a positive electrode material for a sodium ion battery according to claim 1 or 2, characterized in that: The method comprises the following steps: (1) mixing a magnesium-iron-manganese mixed salt solution with a salt solution of M to obtain a first metal salt solution; (2) adding the first metal salt solution, the precipitant solution, and the complexing agent to the bottom liquid in parallel to perform a coprecipitation reaction to obtain a mixed solution; (3) adding an aluminum salt solution, a precipitant solution, and a complexing agent to the mixed solution in parallel to perform a coprecipitation reaction, and separating after aging to obtain a precursor of a positive electrode material for a sodium ion battery; The total concentration of metal ions in the first metal salt solution in step (1) is 0.5 mol / L to 5 mol / L, and during the parallel addition in step (2), the feed rate of the first metal salt solution is 4 L / h to 100 L / h; The concentration of aluminum ions in the aluminum salt solution in step (3) is 0.2 mol / L to 5 mol / L, and the feeding rate of the aluminum salt solution in step (3) is 10 L / h to 20 L / h.

4. The method according to claim 3, characterized in that The concentration of the precipitant solution in step (2) is 2 mol / L to 15 mol / L.

5. The method according to claim 3, characterized in that The concentration of the complexing agent solution in step (2) is 4 mol / L to 12 mol / L.

6. The method according to claim 3, characterized in that The pH value of the base solution in step (2) is between 9.0 and 13.0, and the concentration of the complexing agent is between 0.1 mol / L and 0.5 mol / L.

7. The method according to claim 6, characterized in that The pH value of the base solution in step (2) is between 11.0 and 12.

5.

8. The method according to claim 3, characterized in that During the parallel addition in step (2), the flow rates of the precipitant solution and the complexing agent are controlled so that the pH value of the reaction system is between 10.4 and 11.0 and the concentration of the complexing agent is between 0.30 mol / L and 0.50 mol / L.

9. The method according to claim 3, characterized in that The coprecipitation reaction in step (2) is carried out under the protection of protective gas.

10. The method according to claim 3, characterized in that The temperature of the coprecipitation reaction in step (2) is 40° C. to 80° C., and the time of the coprecipitation reaction is 30 h to 60 h.

11. The method according to claim 3, characterized in that The concentration of the precipitant solution in step (3) is 2 mol / L to 15 mol / L.

12. The method according to claim 3, characterized in that The concentration of the complexing agent solution in step (3) is 4 mol / L to 12 mol / L.

13. The method according to claim 3, characterized in that During the parallel addition process of step (3), the pH value of the reaction system is kept between 9.0 and 13.0 by controlling the flow rates of the precipitant solution and the complexing agent; the concentration of the complexing agent is kept between 0 mol / L and 1 mol / L and does not contain 0 mol / L.

14. The method according to claim 13, characterized in that The pH value of the reaction system is between 10.5 and 11.

5.

15. The method according to claim 13, characterized in that The concentration of the complexing agent is 0.30 mol / L to 1 mol / L.

16. The method according to claim 3, characterized in that The coprecipitation reaction in step (3) is carried out under the protection of protective gas.

17. The method according to claim 3, characterized in that The temperature of the coprecipitation reaction in step (3) is 45° C. to 55° C., and the time of the coprecipitation reaction is 0.5 h to 4 h.

18. The method according to claim 3, characterized in that The average particle size of the product after the coprecipitation reaction in step (3) is D', and the average particle size of the product obtained after the coprecipitation reaction in step (2) is D, where D'-D = 0.05 μm to 0.2 μm.

19. The method according to claim 3, characterized in that The method comprises the following steps: S1: mixing the magnesium, iron and manganese mixed salt solution with the salt solution of M to obtain a first metal salt solution with a total metal ion concentration of 0.5 mol / L to 5 mol / L; S2: First stage reaction: a first metal salt solution, a 2 mol / L to 15 mol / L sodium hydroxide solution, and a 4 mol / L to 12 mol / L ammonia solution are added in parallel to a base solution having a pH value of 9.0 to 13.0 and an ammonia concentration of 0.1 mol / L to 0.5 mol / L. During the parallel addition process, the feed rate of the first metal salt solution is 4 L / h to 100 L / h. By controlling the flow rates of the sodium hydroxide solution and the ammonia solution, the pH value of the reaction system is controlled to be between 10.4 and 11.0 and the ammonia concentration is controlled to be between 0.30 and 0.50 mol / L. Under nitrogen protection, a coprecipitation reaction is carried out at a reaction temperature of 40° C. to 80° C. The reaction is carried out for 30 h to 60 h. When the average particle size reaches D, the first stage reaction is stopped. S3: second stage reaction: adding an aluminum sulfate solution having a total metal ion concentration of 0.2 mol / L to 5 mol / L, a sodium hydroxide solution having a total metal ion concentration of 2 mol / L to 15 mol / L, and a 4 mol / L to 12 mol / L aqueous ammonia solution in parallel to the mixed solution after the first stage reaction, wherein the aluminum sulfate solution is fed at a rate of 10 L / h to 20 L / h during the parallel addition process, and the pH value of the reaction system is controlled to be between 9.0 and 13.0, and the concentration of the complexing agent is controlled to be between 0 mol / L and 1 mol / L and does not contain 0 mol / L by controlling the flow rates of the sodium hydroxide solution and the aqueous ammonia solution, and a coprecipitation reaction is carried out at a reaction temperature of 45° C. to 55° C. under nitrogen protection for 0.5 to 4 hours, and the reaction is stopped when the average particle size reaches D', D'-D=0.05 μm to 0.2 μm; D4: Product post-processing: After the reaction is completed, age for 8 hours, centrifuge and wash, and dry at 100°C to obtain the precursor powder of the sodium ion battery positive electrode material.

20. A sodium ion battery cathode material, characterized in that: The sodium ion battery positive electrode material is prepared using the sodium ion battery positive electrode material precursor according to claim 1 or 2.

21. The sodium ion battery cathode material according to claim 20, characterized in that The sodium ion battery positive electrode material comprises a positive electrode material core and an aluminum oxide film layer coated on the surface of the positive electrode material core. The chemical formula of the positive electrode material core is Na k Mg x Fe y Mn z M (1-x-y-z) O2, wherein 0.4≤k≤1.2, 0.05≤x≤0.20, 0.20≤y≤0.50, 0.30≤z≤0.60, and M is a combination of W and Zr.

22. The sodium ion battery positive electrode material according to claim 21, characterized in that Taking the total mass of the sodium ion battery positive electrode material as 100%, the mass proportion of the aluminum oxide film layer is 0% to 3% and does not include 0%.

23. The sodium ion battery positive electrode material according to claim 22, characterized in that Taking the total mass of the sodium ion battery positive electrode material as 100%, the mass proportion of the aluminum oxide film layer is 0.5% to 1.5%.

24. A method for preparing a positive electrode material for a sodium ion battery according to any one of claims 20 to 23, characterized in that: The method comprises the following steps: The sodium salt and the sodium ion battery positive electrode material precursor are mixed and sintered to obtain the sodium ion battery positive electrode material.

25. The method according to claim 24, characterized in that The sintering temperature is 700°C to 1200°C.

26. The method according to claim 24, characterized in that The sintering time is 10 hours to 25 hours.

27. A sodium ion battery, characterized in that: The sodium ion battery comprises the sodium ion battery positive electrode material according to any one of claims 20 to 23.

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