Sodium battery positive electrode material and preparation method and application thereof

Abstract

This invention provides a sodium-ion battery cathode material, its preparation method, and its application. The general formula of the sodium-ion battery cathode material is Na. a Ni b Ti c Fe d Mn e X f O2, wherein: 0.94≤a≤1.04, 0.20≤b≤0.30, 0.03≤c≤0.1, 0.3≤d≤0.4, 0.3≤e≤0.5, 0.001≤f≤0.02, and element X is selected from at least one of Cu and Ag; the proportion of element X on the surface of the sodium-ion battery cathode material is 0.5wt%-2wt%. The sodium-ion battery cathode material provided by this invention has the characteristics of high initial discharge capacity, high conductivity, and high cycle stability.

Description

Technical Field

[0001] This invention relates to a sodium-ion battery cathode material, and more particularly to a sodium-ion battery cathode material, its preparation method, and its application, belonging to the field of new energy. Background Technology

[0002] Currently, the valence of Fe in sodium-ion battery layered cathode materials is above 3V. Therefore, introducing more Fe can reduce costs and increase the average voltage of the cell. However, the valence of Fe can lead to the Jan Taylor effect, causing significant structural changes. Therefore, it is particularly important to stabilize the structure while increasing the Fe content.

[0003] Chinese patent CN117800411A discloses a sodium-ion battery cathode material precursor uniformly doped with stable valence elements, its preparation method, and the sodium-ion battery cathode material itself. This patent stabilizes metal-oxygen bonds and increases cell volume through doping elements, resulting in a more stable structure and better capacity and cycle performance in the sodium-ion battery cathode material prepared from this precursor. While this patent discloses a technical solution that focuses on improving the precursor by stabilizing metal-oxygen bonds and increasing cell volume through doping elements, it suffers from drawbacks such as low efficiency and limited capacity improvement.

[0004] Chinese patent CN117712349A discloses a coating material for sodium-ion battery cathodes, the sodium-ion battery cathode material and its preparation method, a sodium-ion battery, and related electrical equipment. The coating material provided by this patent is slightly soluble in water, has high air stability, and high ionic conductivity. When used as a coating material for sodium-ion battery cathodes, it effectively improves the storage performance, interfacial stability, and sodium-ion diffusion capacity of the resulting cathode material. It can also effectively reduce the contact area between the cathode material and the electrolyte during cycling, alleviate side reactions between electrode materials, and thus improve the electrochemical performance of the battery. However, because this patent uses a Bi coating method to improve the surface, Bi has relatively low conductivity, and the process involves three sintering stages. Furthermore, the phosphate coating has poor stability, resulting in defects in conductivity and cycle stability.

[0005] As can be seen from the above, at present, sodium electrode materials have the drawback of not being able to simultaneously achieve energy density, conductivity and cycle stability.

[0006] Therefore, developing a sodium-ion cathode material with high initial discharge capacity, conductivity, and cycle stability has become a research direction in this field. Summary of the Invention

[0007] This invention provides a sodium-ion battery cathode material, which has the characteristics of high initial discharge capacity, high conductivity and high cycle stability.

[0008] This invention also provides a method for preparing sodium-ion cathode material, which is characterized by its simple operation.

[0009] The present invention also provides a positive electrode sheet, which has the characteristics of high initial discharge capacity, high conductivity and high cycle stability.

[0010] The present invention also provides a battery that has high initial discharge capacity, high conductivity, and high cycle stability.

[0011] This invention provides a sodium-ion battery cathode material, wherein the general formula of the sodium-ion battery cathode material is Na. a Ni b Ti c Fe d Mn e X f O2, wherein: 0.94≤a≤1.04, 0.20≤b≤0.30, 0.001≤c≤0.1, 0.3≤d≤0.4, 0.3≤e≤0.5, 0.001≤f≤0.02, and element X is selected from at least one of Cu and Ag; the surface mass percentage of element X in the sodium-ion battery cathode material is 0.5wt%-2wt%.

[0012] The sodium-ion cathode material as described above, wherein the initial discharge capacity of the sodium-ion cathode material is greater than or equal to 130 mAh / g; and / or,

[0013] The powder resistivity at 18 MPa pressure is less than or equal to 320,000 Ω*cm; and / or,

[0014] The full cell containing this positive electrode material retains a capacity of ≥94.5% after 100 cycles at 45°C, and the amount of Fe dissolved from the negative electrode is ≤50ppm.

[0015] The sodium-ion cathode material as described above, wherein the single-particle compressive strength of the sodium-ion cathode material is greater than or equal to 190 MPa; and / or,

[0016] The Dv3 of the sodium-ion cathode material is greater than 2 μm;

[0017] Including the dQ / dV spectrum of the full cell containing this cathode material after 100 cycles at 45°C, no irreversible phase transition was observed in the 3.7-4V range; and / or,

[0018] The average voltage of a coin cell containing this positive electrode material is greater than or equal to 3.1V in the 2-4V range.

[0019] This invention also provides a method for preparing a sodium-ion battery cathode material, comprising the following steps:

[0020] 1) A first sintering treatment was performed on a mixed system including nickel-iron-manganese oxide precursor, titanium source and sodium source to obtain a first sintered product;

[0021] 2) The mixed system including the first sintered product and the metal source of element X is subjected to a second sintering treatment to obtain the sodium-ion cathode material;

[0022] The first sintering treatment is carried out at a temperature of 850-1000℃ and a holding time of 8-14h.

[0023] The second sintering treatment is carried out at a temperature of 400-800℃ and a holding time of 6-12 hours.

[0024] The general formula of the nickel-iron-manganese oxide precursor is Ni b Fe d Mn e (OH)2, 0.20≤b≤0.30, 0.3≤d≤0.4, 0.3≤e≤0.5.

[0025] The method for preparing the sodium-ion battery cathode material as described above, wherein the first sintering treatment includes first heating to 600-700°C at a heating rate of 4-8°C / min, then heating to 850-1000°C at a heating rate of 1-2°C / min, and holding at that temperature for 8-14 hours; and / or,

[0026] The second sintering process includes heating to 400-800℃ at a heating rate of 1-5℃ / min and holding at that temperature for 6-12 hours.

[0027] In the preparation method of the sodium-ion cathode material as described above, the X element includes copper and silver, and the molar ratio of copper to silver is 1:(0.6 to 1.5).

[0028] The method for preparing sodium-ion cathode material as described above further includes cooling the product obtained from the first sintering treatment to room temperature at a rate of 2-5 °C / min.

[0029] In the method for preparing sodium-ion cathode material as described above, the X element metal source is selected from at least one of copper oxide and silver oxide.

[0030] The present invention also provides a positive electrode sheet comprising any of the above-mentioned sodium-ion positive electrode materials.

[0031] The present invention also provides a battery comprising any of the above-described sodium-ion cathode materials; and / or

[0032] or,

[0033] This includes any of the above-mentioned positive electrode plates.

[0034] The sodium-ion cathode material provided by this invention has the characteristics of high energy density, high conductivity and high cycle stability. Attached Figure Description

[0035] Figure 1 Here is a SEM image of the sodium-ion cathode material prepared in Example 1;

[0036] Figure 2 Here is a SEM image of the sodium-ion cathode material prepared in Example 2;

[0037] Figure 3 SEM image of the sodium-ion cathode material prepared in Comparative Example 1;

[0038] Figure 4 The image shows the XRD pattern of the sodium-ion cathode material prepared in Example 1.

[0039] Figure 5 This is a schematic diagram of the cross-sectional SEM sampling point locations of the sodium-ion cathode material prepared in Example 1;

[0040] Figure 6 The data shows the silver content distribution at various sampling points of the sodium-ion cathode material prepared in Example 1. Detailed Implementation

[0041] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] The first aspect of this invention provides a sodium-ion battery cathode material, the general formula of which is Na. a Ni b Ti c Fe d Mn e X f O2, wherein: 0.94≤a≤1.04, 0.20≤b≤0.30, 0.03≤c≤0.1, 0.3≤d≤0.4, 0.3≤e≤0.5, 0.001≤f≤0.02, and X is selected from at least one of Cu and Ag; the surface mass percentage of element X in the sodium-ion battery cathode material is 0.5wt%-2wt%.

[0043] The inventors have discovered that the sodium-ion battery cathode material provided by this invention exhibits high initial discharge capacity, high conductivity, and high cycle stability. Based on the above observations, the inventors speculate that the reason for this may be:

[0044] First, the cathode material has suitable iron and titanium content. Fe participates in valence changes during charge and discharge, contributing capacity and a high average voltage, resulting in high energy density for the sodium-ion cathode material. However, high Fe content can lead to structural instability, so titanium is introduced. Titanium stabilizes the structure of the sodium-ion cathode material through solid solution formation of second-phase particles, thus achieving high energy density and cycle stability. Second, the surface of the cathode material is coated with the stabilizing element Ti, which further enhances the cycle stability. Third, Ti enters the crystal lattice, forming second-phase particles with a different crystal structure. These second-phase particles can be coherent or incoherent with the matrix, hindering dislocation movement and increasing the material's strength. This further improves the strength of the cathode material and mitigates cycle degradation caused by particle breakage, resulting in even higher cycle stability for the sodium-ion cathode material.

[0045] Meanwhile, because iron is a variable-valence element, it is susceptible to the Jan Taylor effect. During charging and discharging, iron easily detaches from the bulk and participates in the charging and discharging process (self-discharge), with some iron being reduced and deposited at the negative electrode. The introduction of Ti can suppress the migration of iron to higher valence states, suppress the Jan Taylor effect, stabilize iron in the transition metal layer, and reduce the amount of iron deposited at the negative electrode during charging and discharging. Furthermore, due to its low conductivity, Ti can further passivate iron, making it less prone to deposition.

[0046] However, due to the low conductivity of Ti, the introduction of Ti will reduce the conductivity of the sodium electrode material. In this case, Cu and Ag are materials with good conductivity (specifically, metallic electronic conductivity greater than 30 × 10⁻⁶). 6 By introducing the aforementioned metal elements (s / m) onto the surface of the material, an electron tunneling effect can be induced, improving the electronic conductivity of the cathode material and giving the sodium-ion cathode material of this invention higher conductivity.

[0047] According to the molecular formula of the sodium-ion battery cathode material, if element X is uniformly distributed within the sodium-ion battery cathode material, then the mass percentage of element X in the sodium-ion battery cathode material is approximately 0.05 wt%. In the sodium-ion battery cathode material provided by this invention, the mass percentage of element X on the surface of the sodium-ion battery cathode material is 0.5 wt%-2 wt%, indicating that element X is more distributed on the surface of the sodium-ion battery cathode material, rather than uniformly distributed within it. Since the metallic electronic conductivity of element X is greater than 30*10... 6 The above-mentioned distribution (s / m) gives the sodium-ion cathode material provided by this invention stronger conductivity.

[0048] The sodium-ion cathode material provided by this invention has the characteristics of high initial discharge capacity, high conductivity, and high cycle stability.

[0049] Specifically, the sodium-ion battery cathode material provided by this invention has an initial discharge capacity greater than or equal to 130 mAh / g; and / or, a powder resistivity less than or equal to 320,000 Ω*cm at 18 MPa pressure; and / or, after 100 cycles at 45°C, a full cell including this cathode material exhibits a capacity retention of greater than or equal to 94.5%, and a Fe element dissolution at the negative electrode is less than or equal to 50 ppm. This further demonstrates that the sodium-ion battery cathode material provided by this invention possesses high initial discharge capacity, conductivity, and cycle stability. Fe is a cathode component; a large dissolution of Fe indicates damage to the cathode structure, leading to rapid deterioration in cycling performance. Therefore, a Fe element dissolution at the negative electrode of less than or equal to 50 ppm signifies high cycle stability of the sodium-ion battery cathode material.

[0050] More specifically, the sodium-ion battery cathode material provided by this invention has a single-particle compressive strength greater than or equal to 190 MPa, indicating that the sodium-ion battery cathode material has high mechanical strength. Furthermore, the sodium-ion battery cathode material also has a Dv3 greater than 2 μm. Dv3 is a volumetric particle size index, that is, the particle size value that accounts for 3% of the cathode material by volume. This index characterizes whether the material contains fine powder. Fine powder has a large specific surface area, is difficult to process, has high activity, and exhibits more intense side reactions with the electrolyte, affecting cycle stability. A Dv3 greater than 2 μm indicates that the volume percentage of fine powder with a particle size smaller than 2 μm in the sodium-ion battery cathode material is less than 3%. The small volume percentage of fine powder further highlights the high initial discharge capacity, conductivity, and cycle stability of the sodium-ion battery cathode material provided by this invention.

[0051] In one specific embodiment, the dQ / dV spectrum of a full cell including the cathode material, measured after 100 cycles at 45°C, shows no irreversible phase transition in the 3.7-4V range. The presence of a phase transition indicates a decrease in the cycle stability of the cathode material. Therefore, the absence of an irreversible phase transition in the 3.7-4V range in the dQ / dV spectrum of a full cell including the cathode material after 100 cycles at 45°C further emphasizes the high cycle stability of the cathode material provided by this invention. Furthermore, in one embodiment, the average voltage of a coin cell including the sodium-ion cathode material provided by this invention in the 2-4V range is greater than or equal to 3.1V, indicating that the cathode material provided by this invention further exhibits a high voltage uniformity.

[0052] In one embodiment, SEM (5K field of view) observation of the sodium-ion battery cathode material provided by the present invention revealed fewer than 20 fine powder particles randomly adsorbed on the surface of conventional particles. This phenomenon further demonstrates that the sodium-ion battery cathode material provided by the present invention contains relatively few fine powder particles, thus highlighting its superior initial discharge capacity, conductivity, and cycle stability.

[0053] A second aspect of this invention provides a method for preparing a sodium-ion battery cathode material, which can be used to obtain the sodium-ion battery cathode material provided in the first aspect of this invention. The preparation method includes the following steps:

[0054] 1) A first sintering treatment was performed on a mixed system including nickel-iron-manganese oxide precursor, titanium source and sodium source to obtain a first sintered product;

[0055] 2) A second sintering process is performed on the mixed system including the first sintering product and the metal source of element X to obtain sodium-ion cathode material;

[0056] The first sintering treatment is carried out at a temperature of 850-1000℃ and a holding time of 8-14h.

[0057] The second sintering treatment is carried out at a temperature of 400-800℃ and a holding time of 6-12 hours.

[0058] The general formula for nickel-iron-manganese oxide precursors is Ni. b Fe d Mn e (OH)2, 0.20≤b≤0.30, 0.3≤d≤0.4, 0.3≤e≤0.5.

[0059] The present invention does not limit the preparation method of the above-mentioned nickel-iron-manganese oxide precursor, and can use commonly used preparation methods in the art, such as co-precipitation method.

[0060] Add pure water, 12% ammonia solution, and 30% sodium hydroxide solution to the reactor and stir, controlling the stirring speed at 200 r / min, to obtain the bottom liquid. Simultaneously, add 0.6 m... 3 Nitrogen gas is introduced at a flow rate of / h, and the total volume of the bottom liquid is 3.5m³. 3 The ammonia concentration in the bottom solution is 2 g / L;

[0061] Coprecipitation reaction: A nickel-iron-manganese mixed solution (including aqueous solutions of nickel, iron, and manganese ions), alkaline solution, and ammonia water were added to a reaction vessel. The coprecipitation reaction was carried out at 45°C for 100 h to obtain a nickel-iron-manganese hydroxide slurry. The molar ratio of nickel, iron, and manganese in the nickel-iron-manganese mixed solution was 25:35:40, the total concentration of the nickel-iron-manganese mixed solution was 80 g / L, and the flow rate was 200 L / h. The concentration of the sodium hydroxide solution was 20%, and the flow rate was 50 L / h. The mass concentration of the ammonia water was 12%, and the flow rate was 10 L / h.

[0062] Post-processing: The nickel-iron-manganese hydroxide slurry was successively washed, dried, sieved and packaged to obtain the nickel-iron-manganese-sodium ternary precursor.

[0063] Titanium source refers to a compound containing titanium. In the preparation method provided by this invention, the titanium source is selected from at least one of titanium dioxide, titanium boride, titanium carbide, and titanates (e.g., alkali metal titanates).

[0064] Sodium source refers to a compound containing sodium. In the preparation method provided by this invention, the sodium source is at least one of sodium carbonate, sodium bicarbonate, sodium acetate, and sodium oxalate.

[0065] The metal source of element X is a compound containing element X. The preparation method provided by this invention does not limit the specific selection of the metal source of element X, as long as it meets the requirement of including element X. For example, when element X is copper, the metal source of element X can be selected from at least one of copper sulfate, copper chloride, copper nitrate, and copper acetate; when element X is silver, the metal source of element X can be selected from silver nitrate.

[0066] In the preparation method provided by this invention, the molar ratio of the nickel-iron-manganese oxide precursor, the titanium source, and the sodium source is based on the general formula Na for sodium-ion cathode materials. a Ni b Ti c Fe d Mn e X f O2, wherein 0.94≤a≤1.04, 0.20≤b≤0.30, 0.03≤c≤0.1, 0.3≤d≤0.4, 0.3≤e≤0.5, 0.001≤f≤0.02. That is, first, the values ​​of a, b, c, d, e, and f are selected; nickel-iron-manganese oxide precursors are prepared according to the values ​​of b, d, and e; then, the amounts of sodium source, titanium source, and element X metal source are determined using the values ​​of a, c, and f. A first sintering treatment is performed on the mixed system of raw materials conforming to the above molar ratio to obtain the first sintered product. In the preparation method provided by this invention, the treatment temperature of the first sintering treatment is 850-1000℃, and the holding time is 8-14h. The holding time refers to the duration of the target treatment temperature, excluding the time required to rise from the initial temperature to the target treatment temperature. This invention does not limit the heating rate from the initial temperature to the target treatment temperature; commonly used heating rates in the art can be used. The above process can give the product a better crystallization effect, thus making the resulting cathode material more resistant to breakage during cycling.

[0067] Furthermore, the first sintering process can be carried out in an air atmosphere. The oxygen contained in the air helps in the formation of the first sintering product.

[0068] Furthermore, the first sintered product is mixed with an X element metal source and subjected to a second sintering treatment to obtain a second sintered product. The amount of X element metal source added is as described above and will not be repeated here. In the preparation method provided by this invention, the second sintering treatment temperature is 400-800℃, and the holding time is 6-12 hours. These treatment conditions can further improve the structural instability caused by excessive Fe introduction, while promoting recrystallization and improving internal stress, thereby resulting in a cathode material with more outstanding anti-breakage performance during cycling.

[0069] Furthermore, when the first sintered product is mixed with the X element metal source and a second sintering process is performed, the X element is introduced in the later stage of sintering. Unlike the introduction of X element during the precursor preparation stage, where X element can enter the crystal lattice and participate in the construction of the transition metal layer, when X element is introduced in the later stage of sintering, X does not enter the crystal lattice but instead coats the surface of the first sintered product, improving electronic conductivity. This can be verified by the fact that the surface mass percentage of X element in the sodium electrode material is 0.5-2 wt%.

[0070] The method for preparing sodium-ion battery cathode material provided by this invention can obtain sodium-ion battery cathode material with high energy density, conductivity and cycle stability through common raw materials and simple steps, and has the characteristics of simple operation.

[0071] In one embodiment, the first sintering treatment includes heating to 600-700°C at a heating rate of 4-8°C / min, then heating to 850-1000°C at a heating rate of 1-2°C / min, and holding at that temperature for 8-14 hours. The preparation method provided by this invention, by limiting the heating curve of the first sintering treatment to a rapid-then-slow pattern, combined with the introduction of Ti and the heating rate of 1-2°C / min to 850-1000°C at the nucleation temperature, slows down the nucleation of the crystal structure, resulting in more uniform and consistent unit cells. Consequently, the resulting cathode material exhibits lower internal stress and higher particle compressive strength during cycling.

[0072] Furthermore, in one embodiment, the second sintering treatment includes heating to 400-800°C at a heating rate of 1-5°C / min and holding at that temperature for 6-12 hours. This heating rate slows down crystal nucleation, resulting in more uniform and consistent unit cells. Consequently, the cathode material produced exhibits lower internal stress and higher compressive strength during cycling, further enhancing its characteristics.

[0073] Furthermore, in one embodiment, the product obtained from the first sintering treatment is cooled to room temperature at a rate of 2-5°C / min. This cooling rate further enhances the characteristics of the cathode material, such as lower internal stress during cycling and higher particle compressive strength.

[0074] In one embodiment, the metal source of element X is selected from at least one of copper oxide and silver oxide. The aforementioned compound, as the metal source of element X, can be better integrated with other raw materials, thereby further highlighting the high energy density, conductivity, and cycle stability of the sodium-ion battery cathode material produced.

[0075] A third aspect of the present invention provides a positive electrode sheet comprising the sodium-ion battery positive electrode material provided in the first aspect of the present invention.

[0076] The positive electrode sheet of the present invention specifically includes a positive current collector and a positive active layer formed of a positive active material disposed on the surface of the positive current collector.

[0077] This invention does not limit the preparation method of the positive electrode sheet; methods commonly used in the art can be used for preparation. In one embodiment, the sodium-ion positive electrode material and binder provided by this invention can be dispersed in an appropriate amount of N-methylpyrrolidone (NMP) solvent and thoroughly stirred to form a uniform positive electrode slurry. The positive electrode slurry is then uniformly coated onto a positive electrode current collector, and after drying, rolling, and slitting, a positive electrode sheet is obtained. In a specific embodiment, the positive electrode active layer comprises, by weight percentage, 70-99 wt% positive electrode active material, 0.5-15 wt% conductive agent, and 0.5-15 wt% binder; more specifically, it comprises 80-98 wt% positive electrode active material, 1-10 wt% conductive agent, and 1-10 wt% binder.

[0078] The positive electrode current collector can be made of at least one of aluminum foil, carbon-coated aluminum foil, copper foil, and nickel foil; the binder can be selected from at least one of fluorinated resin, polyether resin, cellulose-type binder, polyacrylate-type binder, and polyimide.

[0079] Since the sodium-ion cathode material provided by this invention has a high discharge specific capacity, the cathode sheet provided by this invention also has a high discharge specific capacity.

[0080] A fourth aspect of the present invention provides a battery comprising any sodium-ion cathode material provided in the first aspect of the present invention, or any cathode sheet provided in the third aspect of the present invention.

[0081] It is conceivable that the battery provided by the present invention, in addition to the aforementioned positive electrode, also includes a negative electrode, an electrolyte, and a separator.

[0082] This invention does not strictly limit the negative electrode active material in the negative electrode sheet. It can be at least one of the negative electrode active materials commonly used in sodium-ion batteries, such as sodium sheet, graphite, hard carbon, soft carbon, mesophase carbon microspheres, silicon-based negative electrode materials (mainly including silicon suboxide and silicon-carbon negative electrode), and tin-based negative electrode materials (mainly including tin and tin alloy).

[0083] The present invention does not strictly limit the choice of electrolyte, and may include one or more solvents commonly used in sodium-ion battery electrolytes, such as at least one of the solutions of propylene carbonate and / or ethylene carbonate of NaPF6 and / or NaClO4.

[0084] The present invention does not strictly limit the choice of membrane material, and can be a membrane material commonly used in sodium-ion batteries, such as at least one selected from polypropylene, polyethylene, and glass fiber.

[0085] The battery provided by this invention has the characteristic of high discharge specific capacity.

[0086] The following examples further illustrate the sodium-ion cathode material, its preparation method, and its applications provided by the present invention.

[0087] First, the nickel-iron-manganese oxide precursor was prepared using the following method:

[0088] 1) Add pure water, 12% ammonia solution, and 30% sodium hydroxide solution to the reactor and stir, controlling the stirring speed at 200 r / min, to obtain the bottom liquid. Simultaneously, add 0.6 m... 3 Nitrogen gas is introduced at a flow rate of / h, and the total volume of the bottom liquid is 3.5m³. 3 The ammonia concentration in the bottom solution is 2 g / L;

[0089] 2) Coprecipitation reaction: A nickel-iron-manganese mixed solution, alkaline solution, and ammonia water were added to the reactor, and a coprecipitation reaction was carried out at 45℃ for 100 h to obtain a nickel-iron-manganese hydroxide slurry. The molar ratio of nickel, iron, and manganese in the nickel-iron-manganese mixed solution was 25:35:40, the total concentration of the nickel-iron-manganese mixed solution was 80 g / L, and the flow rate was 200 L / h; the concentration of the sodium hydroxide solution was 20%, and the flow rate was 50 L / h; the mass concentration of the ammonia water was 12%, and the flow rate was 10 L / h.

[0090] 3) Post-processing: The nickel-iron-manganese hydroxide slurry is washed, dried, sieved and packaged in sequence to obtain the nickel-iron-manganese-sodium ternary precursor.

[0091] In step 2), the molar ratio of nickel, iron, and manganese in the iron-manganese mixed solution can be changed according to the desired precursor formula. For example, to obtain Ni... 0.25 Fe 0.35 Mn 0.40 If the (OH)₂ precursor is used, then the molar ratio of nickel, iron, and manganese is 25:35:40. For example, if the intention is to produce Ni... 0.25 Fe 0.25 Mn 0.50 If the (OH)2 precursor is used, then the molar ratio of nickel, iron, and manganese is 25:25:50.

[0092] Example 1

[0093] Add 10 kg of Ni to the high-speed mixer. 0.25 Fe 0.35 Mn 0.40 (OH)2, 6.04 kg Na 2C O3 and 100.6g TiO2 were mixed at 900rpm for 10min in a 50L high-speed mixer. The mixture was placed in a sagger, and air was introduced. The temperature was first increased to 650℃ at 6℃ / min, and then increased to 940℃ at 1.5℃ / min and held for 10h for sintering. Afterward, the mixture was cooled to room temperature at a rate of 3℃ / min using water cooling and an exhaust fan. The material after exiting the furnace was pulverized and sieved using an air jet mill. The pulverized material was then mixed with 53.9g Ag2O in a 30L high-speed mixer at 900rpm for 10min. The mixture was placed in a sagger, and air was introduced. The temperature was increased to 600℃ at 3℃ / min and held for sintering for 10h. Afterward, the mixture was cooled in the furnace. The material after exiting the furnace was sieved, iron was removed, and the product was packaged to obtain NaNi. 0.25 Fe 0.35 Mn 0.40 Ti 0.006 Ag 0.005 O2 sodium-ion layered cathode material.

[0094] Example 2

[0095] Add 10 kg of Ni to the high-speed mixer. 0.25 Fe 0.35 Mn 0.40 (OH)2, 6.04 kg Na2CO3, and 100.6 g TiO2 were mixed at 900 rpm for 10 min in a 50 L high-speed mixer. The mixture was placed in a sagger, and air was introduced. The temperature was first increased to 650 °C at 6 °C / min, then increased to 940 °C at 1.5 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled to room temperature at a rate of 3 °C / min using water cooling and an exhaust fan. The material after exiting the furnace was pulverized and sieved using an air jet mill. The pulverized material was then mixed with 63.5 CuO in a 30 L high-speed mixer at 900 rpm for 10 min. The mixture was placed in a sagger, and air was introduced. The temperature was increased to 600 °C at 3 °C / min and held for sintering for 10 h. Afterward, the mixture was cooled in the furnace. The material after exiting the furnace was sieved, iron was removed, and the product was packaged (iron (magnetic foreign matter) was removed by setting a current of 20-30 A to form a magnetic field, and the rest was the same). The resulting product had the molecular formula NaNi. 0.25 Fe 0.35 Mn 0.40 Ti 0.006 Cu 0.005 O2 sodium-ion layered cathode material.

[0096] Example 3

[0097] Add 10 kg of Ni to the high-speed mixer. 0.25 Fe 0.35 Mn 0.40 (OH)₂, 6.04 kg Na₂CO₃, and 100.6 g TiO₂ were mixed at 900 rpm for 10 min in a 50 L high-speed mixer. The mixture was placed in a sagger, and air was introduced. The temperature was first increased to 650 °C at 6 °C / min, then increased to 940 °C at 1.5 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled to room temperature at a rate of 3 °C / min using water cooling and an exhaust fan. The material after exiting the furnace was pulverized and sieved using an air jet mill. The pulverized material was then mixed with 31.8 g CuO and 27.0 g Ag₂O in a 30 L high-speed mixer at 900 rpm for 10 min. The mixture was placed in a sagger, and air was introduced. The temperature was increased to 600 °C at 3 °C / min and held for sintering for 10 h. Afterward, the mixture was cooled in the furnace. The material after exiting the furnace was sieved, iron was removed, and the product was packaged to obtain the product with the molecular formula [missing information].

[0098] NaNi 0.25 Fe 0.35 Mn 0.40 Ti 0.006 Ag 0.0025 Cu 0.0025 O2 sodium-ion layered cathode material.

[0099] Example 4

[0100] Add 10 kg of Ni to the high-speed mixer. 0.25 Fe 0.30 Mn 0.45 (OH)₂, 6.04 kg Na₂CO₃, and 100.6 g TiO₂ were mixed at 900 rpm for 10 min in a 50 L high-speed mixer. The mixture was placed in a sagger, and air was introduced. The temperature was first increased to 650 °C at 6 °C / min, then increased to 940 °C at 1.5 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled to room temperature at a rate of 3 °C / min using water cooling and an exhaust fan. The material after exiting the furnace was pulverized and sieved using an air jet mill. The pulverized material was then mixed with 53.9 g Ag₂O in a 30 L high-speed mixer at 900 rpm for 10 min. The mixture was placed in a sagger, and air was introduced. The temperature was increased to 600 °C at 3 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled in the furnace. The material after exiting the furnace was sieved, iron was removed, and the product was packaged to obtain the product with the molecular formula [missing information].

[0101] NaNi 0.25 Fe 0.35 Mn 0.40 Ti 0.006 Ag 0.005O2 sodium-ion layered cathode material.

[0102] Example 5

[0103] Add 10 kg of Ni to the high-speed mixer. 0.25 Fe 0.40 Mn 0.35 (OH)₂, 6.04 kg Na₂CO₃, and 100.6 g TiO₂ were mixed at 900 rpm for 10 min in a 50 L high-speed mixer. The mixture was placed in a sagger, and air was introduced. The temperature was first increased to 650 °C at 6 °C / min, then increased to 940 °C at 1.5 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled to room temperature at a rate of 3 °C / min using water cooling and an exhaust fan. The material after exiting the furnace was pulverized and sieved using an air jet mill. The pulverized material was then mixed with 53.9 g Ag₂O in a 30 L high-speed mixer at 900 rpm for 10 min. The mixture was placed in a sagger, and air was introduced. The temperature was increased to 600 °C at 3 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled in the furnace. The material after exiting the furnace was sieved, iron was removed, and the product was packaged to obtain the product with the molecular formula [missing information].

[0104] NaNi 0.25 Fe 0.35 Mn 0.40 Ti 0.006 Ag 0.005 O2 sodium-ion layered cathode material.

[0105] Example 6

[0106] Add 10 kg of Ni to the high-speed mixer. 0.25 Fe 0.35 Mn 0.40 (OH)₂, 6.04 kg Na₂CO₃, and 100.6 g TiO₂ were mixed at 900 rpm for 10 min in a 50 L high-speed mixer. The mixture was placed in a sagger, and air was introduced. The temperature was first increased to 650 °C at 4 °C / min, then increased to 940 °C at 1 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled to room temperature at a rate of 3 °C / min using water cooling and an exhaust fan. The material was then pulverized and sieved using an air jet mill. The pulverized material was then mixed with 53.9 g Ag₂O in a 30 L high-speed mixer at 900 rpm for 10 min. The mixture was placed in a sagger, and air was introduced. The temperature was increased to 600 °C at 3 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled in the furnace. The material was then sieved, iron-removed, and packaged to obtain the product with the molecular formula [missing information].

[0107] NaNi 0.25 Fe 0.35 Mn 0.40 Ti 0.006 Ag 0.005O2 sodium-ion layered cathode material.

[0108] Example 7

[0109] Add 10 kg of Ni to the high-speed mixer. 0.25 Fe 0.35 Mn 0.40 (OH)₂, 6.04 kg Na₂CO₃, and 100.6 g TiO₂ were mixed at 900 rpm for 10 min in a 50 L high-speed mixer. The mixture was placed in a sagger, and air was introduced. The temperature was first increased to 650 °C at 8 °C / min, then increased to 940 °C at 2 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled to room temperature at a rate of 3 °C / min using water cooling and an exhaust fan. The material was then pulverized and sieved using an air jet mill. The pulverized material was then mixed with 53.9 g Ag₂O in a 30 L high-speed mixer at 900 rpm for 10 min. The mixture was placed in a sagger, and air was introduced. The temperature was increased to 600 °C at 3 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled in the furnace. The material was then sieved, iron-removed, and packaged to obtain the product with the molecular formula [missing information].

[0110] NaNi 0.25 Fe 0.35 Mn 0.40 Ti 0.006 Ag 0.005 O2 sodium-ion layered cathode material.

[0111] Example 8

[0112] Add 10 kg of Ni to the high-speed mixer. 0.25 Fe 0.35 Mn 0.40 (OH)₂, 6.04 kg Na₂CO₃, and 100.6 g TiO₂ were mixed at 900 rpm for 10 min in a 50 L high-speed mixer. The mixture was placed in a sagger, and air was introduced. The temperature was first increased to 650 °C at 1.5 °C / min, then increased to 940 °C at 1.5 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled to room temperature at a rate of 3 °C / min using water cooling and an exhaust fan. The material after exiting the furnace was pulverized and sieved using an air jet mill. The pulverized material was then mixed with 53.9 g Ag₂O in a 30 L high-speed mixer at 900 rpm for 10 min. The mixture was placed in a sagger, and air was introduced. The temperature was increased to 600 °C at 3 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled in the furnace. The material after exiting the furnace was sieved, iron removed, and packaged to obtain the molecular formula [missing information].

[0113] NaNi 0.25 Fe 0.35 Mn 0.40 Ti 0.006 Ag 0.005O2 sodium-ion layered cathode material.

[0114] Example 9

[0115] Add 10 kg of Ni to the high-speed mixer. 0.25 Fe 0.35 Mn 0.40 (OH)₂, 6.04 kg Na₂CO₃, and 100.6 g TiO₂ were mixed at 900 rpm for 10 min in a 50 L high-speed mixer. The mixture was placed in a sagger, and air was introduced. The temperature was first increased to 650 °C at 6 °C / min, then increased to 940 °C at 6 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled to room temperature at a rate of 3 °C / min using water cooling and an exhaust fan. The material was then pulverized and sieved using an air jet mill. The pulverized material was then mixed with 53.9 g Ag₂O in a 30 L high-speed mixer at 900 rpm for 10 min. The mixture was placed in a sagger, and air was introduced. The temperature was increased to 600 °C at 3 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled in the furnace. The material was then sieved, iron-removed, and packaged to obtain the product with the molecular formula [missing information].

[0116] NaNi 0.25 Fe 0.35 Mn 0.40 Ti 0.006 Ag 0.005 O2 sodium-ion layered cathode material.

[0117] Example 10

[0118] Add 10 kg of Ni to the high-speed mixer. 0.28 Fe 0.32 Mn 0.40 (OH)2, 6.04 kg Na 2C O3 and 100.6g TiO2 were mixed at 900rpm for 10min in a 50L high-speed mixer. The mixture was placed in a sagger, and air was introduced. The temperature was first increased to 650℃ at 6℃ / min, and then increased to 940℃ at 1.5℃ / min and held for 10h for sintering. Afterward, the mixture was cooled to room temperature at a rate of 3℃ / min using water cooling and an exhaust fan. The material after exiting the furnace was pulverized and sieved using an air jet mill. The pulverized material was then mixed with 53.9g Ag2O in a 30L high-speed mixer at 900rpm for 10min. The mixture was placed in a sagger, and air was introduced. The temperature was increased to 600℃ at 3℃ / min and held for sintering for 10h. Afterward, the mixture was cooled in the furnace. The material after exiting the furnace was sieved, iron was removed, and the product was packaged to obtain NaNi. 0.28 Fe 0.32 Mn 0.40 Ti 0.006 Ag 0.005 O2 sodium-ion layered cathode material.

[0119] Example 11

[0120] Add 10 kg of Ni to the high-speed mixer. 0.25 Fe 0.35 Mn 0.40 (OH)2, 5.80 kg Na 2C O3 and 100.6g TiO2 were mixed at 900rpm for 10min in a 50L high-speed mixer. The mixture was placed in a sagger, and air was introduced. The temperature was first increased to 650℃ at 6℃ / min, and then increased to 940℃ at 1.5℃ / min and held for 10h for sintering. Afterward, the mixture was cooled to room temperature at a rate of 3℃ / min using water cooling and an exhaust fan. The material after exiting the furnace was pulverized and sieved using an air jet mill. The pulverized material was then mixed with 53.9g Ag2O in a 30L high-speed mixer at 900rpm for 10min. The mixture was placed in a sagger, and air was introduced. The temperature was increased to 600℃ at 3℃ / min and held for sintering for 10h. Afterward, the mixture was cooled in the furnace. The material after exiting the furnace was sieved, iron was removed, and the product was packaged to obtain Na. 0.96 Ni 0.25 Fe 0.35 Mn 0.40 Ti 0.006 Ag 0.005 O2 sodium-ion layered cathode material.

[0121] Comparative Example 1

[0122] Add 10 kg of Ni to the high-speed mixer. 0.25 Fe 0.35 Mn 0.40 (OH)2 and 6.04 kg of Na2CO3 were mixed at 900 rpm for 10 min in a 50 L high-speed mixer. The mixture was then placed in a sagger, and air was introduced. The temperature was first increased to 650 °C at 6 °C / min, and then increased to 940 °C at 1.5 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled to room temperature at a rate of 3 °C / min using water cooling and an exhaust fan. The material after exiting the furnace was pulverized and sieved using an air jet mill. The pulverized material was then mixed with 53.9 g of Ag2O in a 30 L high-speed mixer at 900 rpm for 10 min. The mixture was then placed in a sagger, and air was introduced. The temperature was increased to 600 °C at 3 °C / min and held for sintering for 10 h. Afterward, the mixture was cooled in the furnace. The material after exiting the furnace was sieved, iron was removed, and the product was packaged to obtain NaNi. 0.25 Fe 0.35 Mn 0.40 Ag 0.005 O2 sodium-ion layered cathode material.

[0123] Comparative Example 2

[0124] Add 10 kg of Ni to the high-speed mixer. 0.25 Fe 0.35 Mn 0.40 (OH)2, 6.04 kg Na2CO3, and 83.2 g MgO were mixed at 900 rpm for 10 min in a 50 L high-speed mixer. The mixture was placed in a sagger, and air was introduced. The temperature was first increased to 650 °C at 6 °C / min, then increased to 940 °C at 1.5 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled to room temperature at a rate of 3 °C / min using water cooling and an exhaust fan. The material after exiting the furnace was pulverized and sieved using an air jet mill. The pulverized material was then mixed with 53.9 g Ag2O in a 30 L high-speed mixer at 900 rpm for 10 min. The mixture was placed in a sagger, and air was introduced. The temperature was increased to 600 °C at 3 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled in the furnace. The material after exiting the furnace was sieved, iron was removed, and the product was packaged to obtain NaNi. 0.25 Fe 0.35 Mn 0.40 Mg 0.005 Ag 0.005 O2 sodium-ion layered cathode material.

[0125] Comparative Example 3

[0126] Add 10 kg of Ni to the high-speed mixer. 0.25 Fe 0.35 Mn 0.40 (OH)₂, 6.04 kg Na₂CO₃, and 100.6 g TiO₂ were mixed in a 50 L high-speed mixer at 900 rpm for 10 min. The mixture was placed in a sagger, and air was introduced. The temperature was first increased to 650 °C at 6 °C / min, then increased to 940 °C at 1.5 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled to room temperature at a rate of 3 °C / min using water cooling and an exhaust fan. The material after exiting the furnace was pulverized and sieved using an air jet mill. The pulverized material was then placed in a sagger, and air was introduced. The temperature was increased to 600 °C at 3 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled with the furnace. The material after exiting the furnace was sieved, iron was removed, and the product was packaged to obtain the product with the molecular formula [missing information].

[0127] NaNi 0.25 Fe 0.35 Mn 0.40 Ti 0.006 O2 sodium-ion layered cathode material.

[0128] Comparative Example 4

[0129] Add 10 kg of Ni to the high-speed mixer. 0.25 Fe 0.35 Mn 0.40(OH)₂, 6.04 kg Na₂CO₃, and 100.6 g TiO₂ were mixed at 900 rpm for 10 min in a 50 L high-speed mixer. The mixture was placed in a sagger, and air was introduced. The temperature was first increased to 650 °C at 6 °C / min, then increased to 940 °C at 1.5 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled to room temperature at a rate of 3 °C / min using water cooling and an exhaust fan. The material after exiting the furnace was pulverized and sieved using an air jet mill. The pulverized material was then mixed with 67.7 g ZrO₂ in a 30 L high-speed mixer at 900 rpm for 10 min. The mixture was placed in a sagger, and air was introduced. The temperature was increased to 600 °C at 3 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled in the furnace. The material after exiting the furnace was sieved, iron was removed, and the product was packaged to obtain the product with the molecular formula [missing information].

[0130] NaNi 0.25 Fe 0.35 Mn 0.40 Ti 0.006 Zr 0.005 O2 sodium-ion layered cathode material.

[0131] Comparative Example 5

[0132] Add 10 kg of Ni to the high-speed mixer. 0.25 Fe 0.25 Mn 0.50 (OH)₂, 6.04 kg Na₂CO₃, and 100.6 g TiO₂ were mixed at 900 rpm for 10 min in a 50 L high-speed mixer. The mixture was placed in a sagger, and air was introduced. The temperature was first increased to 650 °C at 6 °C / min, then increased to 940 °C at 1.5 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled to room temperature at a rate of 3 °C / min using water cooling and an exhaust fan. The material after exiting the furnace was pulverized and sieved using an air jet mill. The pulverized material was then mixed with 53.9 g Ag₂O in a 30 L high-speed mixer at 900 rpm for 10 min. The mixture was placed in a sagger, and air was introduced. The temperature was increased to 600 °C at 3 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled in the furnace. The material after exiting the furnace was sieved, iron was removed, and the product was packaged to obtain the product with the molecular formula [missing information].

[0133] NaNi 0.25 Fe 0.25 Mn 0.50 Ti 0.006 Ag 0.005 O2 sodium-ion layered cathode material.

[0134] Comparative Example 6

[0135] Add 10 kg of Ni to the high-speed mixer. 0.25 Fe 0.45 Mn 0.30(OH)₂, 6.04 kg Na₂CO₃, and 100.6 g TiO₂ were mixed at 900 rpm for 10 min in a 50 L high-speed mixer. The mixture was placed in a sagger, and air was introduced. The temperature was first increased to 650 °C at 6 °C / min, then increased to 940 °C at 1.5 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled to room temperature at a rate of 3 °C / min using water cooling and an exhaust fan. The material after exiting the furnace was pulverized and sieved using an air jet mill. The pulverized material was then mixed with 53.9 g Ag₂O in a 30 L high-speed mixer at 900 rpm for 10 min. The mixture was placed in a sagger, and air was introduced. The temperature was increased to 600 °C at 3 °C / min and held for 10 h for sintering. Afterward, the mixture was cooled in the furnace. The material after exiting the furnace was sieved, iron was removed, and the product was packaged to obtain the product with the molecular formula [missing information].

[0136] NaNi 0.25 Fe 0.45 Mn 0.30 Ti 0.006 Ag 0.005 O2 sodium-ion layered cathode material.

[0137] Comparative Example 7

[0138] Add 10 kg of Ni to the high-speed mixer. 0.25 Fe 0.35 Mn 0.40 (OH)2, 6.04 kg Na 2C O3, 100.6g TiO2, and 53.9g Ag2O were mixed in a 50L high-speed mixer at 900rpm for 10min. The mixture was placed in a sagger, and air was introduced. The temperature was first increased to 650℃ at 6℃ / min, then increased to 940℃ at 1.5℃ / min and held for 10h for sintering. Afterward, the mixture was cooled to room temperature at a rate of 3℃ / min using water cooling and an exhaust fan. The material after exiting the furnace was pulverized and sieved using an air jet mill. The pulverized material was then placed in a sagger, and air was introduced. The temperature was increased to 600℃ at 3℃ / min and held for sintering for 10h. Afterward, the mixture was cooled with the furnace. The material after exiting the furnace was sieved, iron was removed, and the product was packaged to obtain the product with the molecular formula [missing information].

[0139] NaNi 0.25 Fe 0.35 Mn 0.40 Ti 0.006 Ag 0.005 O2 sodium-ion layered cathode material.

[0140] Test case

[0141] 1. SEM tests were performed on the sodium-ion cathode materials prepared in Example 1, Example 2, and Comparative Example 1, respectively, to obtain... Figures 1-3 ;

[0142] Depend on Figures 1-3 It can be seen that, Figure 3 In Comparative Example 1, the sodium-ion battery cathode material had fine particles on its surface. EDS analysis of these particles revealed that they were sodium compounds. This indicates that because Ti was not added in Comparative Example 1, sodium compounds precipitated on the surface of the resulting sodium-ion battery cathode material. These sodium compounds can become residual alkali, affecting the gas generation and processing performance of the cathode material.

[0143] XRD tests were performed on the sodium-ion cathode material prepared in Example 1. The images are shown below. Figure 4 . Figure 4 By referring to the peak shape of the PDF standard card 28-0819-NaCrO2, it can be seen that this material is a layered O3 sodium electrode material.

[0144] 2. The particle strength, powder resistance, and Dv3 of the sodium-ion layered cathode materials prepared in each embodiment and comparative example were tested. The results are shown in Table 1.

[0145] in:

[0146] Test method for single particle strength: Using Shimadzu DUH-211S equipment, under a 500x microscope, select a single particle with a primary particle size distribution of 3-8μm in the positive electrode material, apply pressure with a 50μm flat indenter, record the corresponding pressure and stress, and obtain the stress corresponding to particle breakage. Test more than 10 particles and take the average value.

[0147] Powder resistance test method: PD-51 test equipment and MCP-T700 impedance meter are used. The four-probe method is adopted. 4g of material is weighed and placed in a graduated cylinder with a radius of 10mm. The powder resistance value is recorded under a pressure of 18MPa.

[0148] Dv3 testing method: Using a Malvern 3000 particle size analyzer, add approximately 0.2g of sample to a 50mL beaker, add one dropper of 10% sodium hexametaphosphate, add water to approximately 20mL, and sonicate externally at 60% intensity for 5min. Then transfer to a beaker of 1L deionized water, stir at 3000rpm, and maintain a light-blocking degree of 8-12% for testing.

[0149] The method for determining the mass percentage of element X on the surface of sodium-ion cathode material was as follows: Ion milling was performed using a Gatan 697Ilion II instrument. The high-purity argon gas outlet pressure was controlled at 0.18 MPa, the sample chamber pressure was <5 × 10⁻⁶ Torr, the angles of the left and right ion guns were controlled at 0 degrees, and the ion beam energy was 5 keV. After milling, EDS measurements were performed using a Hitachi Regulus 8100 / SU 8010 instrument. The test voltage was controlled at 1 kV, the test current at 10 μA, and a magnification of 10 K was used for spot scanning. Main elements such as Ni, Fe, Mn, Ti, Cu, and Ag were selected, and the measurements were taken based on the selected positions (specifically, the spectra). Figure 1 , 2 3 and 4 are considered as the surface layer, among which, the spectrum Figure 5 , 6 Points 7 and 8 (considered internal) are used to automatically calculate the proportions of each element. For the sodium-ion cathode material prepared in Example 1, the sampling points are shown in the figure. Figure 5 The distribution data of silver content at each point can be found in the following table. Figure 6 Take the mass percentage of element X at any surface location of each sample and fill it into Table 1.

[0150] Table 1

[0151]

[0152] As shown in Table 1, the sodium-ion cathode materials prepared in Examples 1-7 have higher strength and lower resistance compared to the materials prepared in the comparative examples. In Examples 8 and 9, due to unsuitable heating rates in the first or second sintering treatment, the materials prepared had lower strength and higher resistance compared to the materials prepared in Examples 1-7.

[0153] Depend on Figure 6 It can be seen that in the sodium-ion cathode material prepared in Example 1, the silver content is high on the surface of the material and low inside the material.

[0154] In Comparative Example 7, silver and titanium were simultaneously doped into the material instead of being introduced through post-coating. Compared to Example 1, the sample prepared in Comparative Example 7 had a significantly lower silver content on its surface and a higher powder resistivity. This indicates that introducing element X into the cathode material through post-coating can enhance the conductivity of the cathode material.

[0155] Furthermore, as mentioned above, based on the molecular formula of the sodium-ion cathode material, if element X is uniformly distributed within the sodium-ion cathode material, then the mass percentage of element X in the sodium-ion cathode material is approximately 0.05 wt%. Table 1 shows that in the samples prepared in Examples 1 to 11, the mass percentage of element X on the surface of the sodium-ion cathode material is significantly higher than 0.05 wt%, indicating that element X is more distributed on the surface of the sodium-ion cathode material, rather than uniformly distributed within it.

[0156] 3. The sodium-ion layered cathode materials prepared in each embodiment and comparative example are assembled into coin cells using the following method:

[0157] The prepared sodium-ion layered positive electrode material, acetylene black, and polyvinylidene fluoride (PVDF) were weighed at a mass ratio of 90:5:5, mixed evenly, and NMP was added and stirred for 2 hours to form a viscous slurry. This slurry was then evenly coated onto aluminum foil, vacuum baked at 80°C, pressed into sheets, and cut into positive electrode sheets with a diameter of 14 mm. Using a 16 mm diameter pure sodium sheet as the negative electrode, Tianci ENA-18 as the electrolyte, and a PP / PE / PP composite separator, the cells were assembled into coin cells in an argon-filled glove box.

[0158] The assembled button cells were subjected to 0.2C initial discharge capacity, 2-4V average voltage, and initial efficiency tests. The test results are shown in Table 2.

[0159] The 0.2C capacity / energy density test method is as follows: The assembled button cell is placed in a Blue Electric device at a test temperature of 25±1℃ and a test voltage of 2.0~4.0V. It is charged and discharged at 0.2C / 0.2C, and the charging cut-off current is 0.05C (1C nominal capacity is 130mAh / g).

[0160] 2-4V average voltage test method: It is calculated based on the tested 0.2C coin energy and coin capacity. The calculation method is: 0.2C coin energy / 0.2C coin discharge capacity.

[0161] The method for testing the first efficiency is as follows: At 25℃, charge the battery at a constant current of 0.1C to 4.0V, then charge it at a constant voltage until the current is less than or equal to 0.01mA. After that, let it stand for 5 minutes to obtain the charging capacity R1. Then discharge it at a constant current of 0.1C to 2.0V, and then let it stand for 5 minutes to obtain the discharge capacity R2. R2 / R1*100% is the first efficiency.

[0162] Table 2

[0163]

[0164]

[0165] As shown in Table 2, the sodium-ion cathode materials prepared in Examples 1 to 11 have higher initial discharge capacity, average voltage, and initial efficiency compared to the materials prepared in the comparative examples.

[0166] Furthermore, compared to Examples 1 to 7, the initial discharge capacity, average voltage, and initial efficiency of Examples 8 and 9 were relatively low. This may be because the heating rate of the first sintering treatment during the preparation of the Example 8 sample was slower, while the heating rate of the first sintering treatment during the preparation of the Example 9 sample was faster.

[0167] 4. The sodium-ion layered cathode materials prepared in each embodiment and comparative example are assembled into full cells in the following manner:

[0168] A positive electrode slurry was prepared by mixing sodium-ion battery layered cathode material, conductive carbon black SP, conductive graphite KS-6, and binder PVDF in a mass ratio of 94.5%:2%:1%:2.5% with NMP. The cathode slurry was then coated (coating density 12 mg / cm³). 2 The positive electrode sheet is produced by the rolling process and then assembled with the negative electrode (graphite), the separator (polyCelgard propylene microporous membrane), and the electrolyte (1mol / L LiPF6+DEC / EC (volume ratio 1:1)) to form a 503048 full cell with a capacity of about 400mAh.

[0169] The assembled full cells were tested for capacity retention and iron dissolution at 45℃ for 100 cycles. The results are shown in Table 3.

[0170] The method for testing the iron leaching amount from the negative electrode is as follows: 0.4g of the negative electrode is weighed from a full cell after testing the cycle capacity retention rate. Plate digestion is performed using 10ml of aqua regia, and the elements enriched in the negative electrode are determined using an ICP-OES instrument.

[0171] The test method for capacity retention rate at 45℃ for 100 cycles is as follows: use the Xinwei CT3008-5V3A-A1 battery, cycle at 45℃, with a voltage of 4~2V and a constant voltage cutoff current of 20mA, for 100 cycles.

[0172] Cyclic gas generation test method: Before cycling, the volume of the pouch cell was measured by the water displacement method and recorded as V1. After cycling 100 times at 45℃, the volume of the pouch cell was measured by the water displacement method and recorded as V2. The volume growth rate is (V2-V1) / V1*100%.

[0173] Table 3

[0174]

[0175] As shown in Table 3, the sodium-ion cathode materials prepared in Examples 1 to 11 have a lower mass ratio of dissolved iron in the anode, a higher cycle capacity retention rate, and a lower cycle gas production growth rate compared to the materials prepared in the comparative examples.

[0176] Furthermore, compared to Examples 1 to 7, Examples 8 and 9 exhibited relatively low capacity retention, but higher Fe mass ratio and gas production growth rate. This may be due to the slower heating rate of the first sintering treatment during the preparation of the Example 8 sample, while the faster heating rate of the first sintering treatment during the preparation of the Example 9 sample.

[0177] 4. After cycling the full cells prepared from the materials of each embodiment and comparative example used in Experimental Example 4 for 100 cycles in an environment of 45°C, the charge-discharge curves were differentiated to obtain dQ / dV, and the presence of irreversible phase transitions in the 3.7-4V range was observed. It was observed that no irreversible phase transitions occurred in Examples 1 to 11 within the 3.7-4V range, while irreversible phase transitions occurred in Comparative Examples 1 to 5 within the 3.7-4V range.

[0178] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention 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; and these 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 the present invention.

Claims

1. A sodium-ion battery cathode material, wherein the material has a single-crystal structure, characterized in that, The molecular formula of the sodium-ion battery cathode material is Na. a Ni b Ti c Fe d Mn e X f O2, wherein: 0.94≤a≤1.04, 0.20≤b≤0.30, 0.001≤c≤0.1, 0.3≤d≤0.4, 0.3≤e≤0.5, 0.001≤f≤0.02, and element X is selected from at least one of Cu and Ag; the surface mass percentage of element X in the sodium-ion battery cathode material is 0.5wt%-2wt%. The compressive strength of a single particle of the sodium-ion cathode material is greater than or equal to 190 MPa.

2. The sodium-ion cathode material according to claim 1, characterized in that, The initial discharge capacity of the sodium-ion cathode material is greater than or equal to 130 mAh / g; and / or, The powder resistivity is less than or equal to 320,000 Ω at a pressure of 18 MPa. cm; and / or, The full cell containing this positive electrode material retains a capacity of ≥94.5% after 100 cycles at 45°C, and the amount of Fe dissolved from the negative electrode is ≤50ppm.

3. The sodium-ion cathode material according to claim 1, characterized in that, The Dv3 of the sodium-ion cathode material is greater than 2 μm; Including the dQ / dV spectrum of the full cell containing this cathode material after 100 cycles at 45°C, no irreversible phase transition was observed in the 3.7-4V range; and / or, The average voltage of a coin cell containing this positive electrode material is greater than or equal to 3.1V in the 2-4V range.

4. A method for preparing a sodium-ion cathode material according to any one of claims 1-3, characterized in that, Includes the following steps: 1) A first sintering treatment is performed on a mixed system including nickel-iron-manganese oxide precursor, titanium source and sodium source to obtain a first sintered product; the first sintered product is cooled to room temperature and pulverized by a vapor mill; 2) The mixture of the first sintered product after crushing and the metal source of element X is subjected to a second sintering treatment to obtain the sodium-ion cathode material; The first sintering treatment is carried out at a temperature of 850-1000℃ and a holding time of 8-14h. The second sintering treatment is carried out at a temperature of 400-800℃ and a holding time of 6-12 hours. The general formula of the nickel-iron-manganese oxide precursor is Ni b Fe d Mn e (OH)2, 0.20≤b≤0.30, 0.3≤d≤0.4, 0.3≤e≤0.5; The first sintering process includes first heating to 600-700℃ at a heating rate of 4-8℃ / min, then heating to 850-1000℃ at a heating rate of 1-2℃ / min, and holding at that temperature for 8-14 hours.

5. The method according to claim 4, characterized in that, The second sintering process includes heating to 400-800℃ at a heating rate of 1-5℃ / min and holding at that temperature for 6-12 hours.

6. The method according to claim 4, characterized in that, The X element includes copper and silver, with a molar ratio of copper to silver of 1:(0.6~1.5).

7. The method according to any one of claims 4-6, characterized in that, It also includes cooling the product obtained from the first sintering treatment to room temperature at a rate of 2-5 °C / min.

8. The method according to any one of claims 4-6, characterized in that, The metal source of element X is selected from at least one of copper oxide and silver oxide.

9. A positive electrode plate, characterized in that, The positive electrode sheet comprises the sodium-ion positive electrode material according to any one of claims 1-3.

10. A battery, characterized in that, The battery comprises the sodium-ion cathode material according to any one of claims 1-3; and / or, The battery includes the positive electrode as described in claim 9.

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