Layered oxide positive electrode material and preparation method and application thereof

Abstract

The invention relates to a layered oxide positive electrode material and a preparation method and application thereof, and belongs to the technical field of sodium batteries, and the preparation method of the layered oxide positive electrode material comprises the following steps: in an air atmosphere, uniformly mixing a first metal source and a sodium source, then carrying out first calcination, cooling, crushing and grinding, and then carrying out second calcination to obtain the layered oxide positive electrode material. The layered oxide positive electrode material is obtained; the number of the first metal sources is at least two, the median diameter D50 of only one metal source Mi is at least 1.5 times of the median diameter of the other metal sources, the sum of the products of the valence Z corresponding to the first metal sources and the corresponding molar weight y is S, S is larger than or equal to 2 and smaller than or equal to 4-x, and Z is larger than or equal to 2 and smaller than or equal to 4. According to the method, the types and parameters of the first metal sources are selected and matched, and the relationship among the metal sources in the first metal sources is controlled, so that the difficulty of redox reaction in the calcining process can be obviously reduced, and the cycle performance of the prepared layered oxide positive electrode material is improved.

Description

Technical Field

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

[0002] Sodium-ion batteries, as an emerging energy storage technology, have attracted widespread attention due to their abundant resources and low cost. Among them, layered oxide cathode materials are considered one of the ideal cathode materials for sodium-ion batteries due to their high specific capacity and good cycle stability.

[0003] Currently, a common method for preparing high-performance layered oxide cathode materials is to use a co-precipitation method to prepare a precursor, which is then mixed with a sodium salt and calcined. This method allows for precise control of the precursor's composition and structure, resulting in high-performance cathode materials. However, the co-precipitation method requires complex reaction equipment and precise control conditions, which increases production costs. Furthermore, the co-precipitation method involves multiple steps, including solution preparation, precipitation reaction, filtration, washing, and drying, making the operation complex and time-consuming. In addition, the co-precipitation process may generate a large amount of waste liquid, requiring additional treatment measures and increasing environmental costs.

[0004] To reduce the production cost of cathode materials, researchers have tried various other methods, such as the sol-gel method: mixing a metal salt solution with an organic solvent to form a sol, followed by drying and calcination to prepare the cathode material. While this method can reduce costs to some extent, it is difficult to precisely control the uniform distribution of metal ions, leading to inconsistent cathode material performance. Spray drying involves forming particles from a solution through spray drying, followed by calcination. Although this method can improve production efficiency, spray drying equipment is expensive, increasing initial investment costs, and the uneven particle size distribution affects the overall performance of the cathode material.

[0005] Given the aforementioned shortcomings of existing technologies, how to prepare high-performance sodium-ion cathode materials while significantly reducing costs has become an urgent problem to be solved. Summary of the Invention

[0006] In view of the above analysis, the present invention aims to provide a layered oxide cathode material and its preparation method and application, in order to solve at least one of the following technical problems: (1) the co-precipitation method for preparing layered oxide cathode materials has high production costs, complex processes, and subsequent waste liquid treatment increases environmental costs; (2) although the sol-gel method reduces costs, it cannot guarantee the performance of the cathode material, and the spray drying method has high costs and the cathode material obtained has unstable performance.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] The first aspect of the present invention provides a method for preparing a layered oxide cathode material, comprising: mixing a first metal source and a sodium source uniformly in an air atmosphere and then performing a first calcination, cooling to room temperature, pulverizing and grinding, and then performing a second calcination to obtain a layered oxide cathode material;

[0009] Among them, the first metal source is at least two kinds, and there is only one metal source Mi whose median particle size D50 is at least 1.5 times the median particle size of the other metal sources;

[0010] The sum of the products of the valence state Z corresponding to the first metal source and the corresponding molar amount y is S, which satisfies 2≤S≤4-x, where x is the molar amount of sodium, and the valence state Z corresponding to the first metal source satisfies 2≤Z≤4.

[0011] Furthermore, the median particle size D50 of the metal source Mi is 2.5-4 times that of the median particle size of the other metal sources.

[0012] Furthermore, the sum of the products S between the valence state Z and the molar quantity y corresponding to the first metal source satisfies: 2.4≤S≤4-x.

[0013] Furthermore, the valence state Z corresponding to the first metal source satisfies 2≤Z≤3.

[0014] Furthermore, the median particle size of the metal source Mi is 5μm≤D50≤12μm, SPAN<1.2, where SPAN is defined as (D90-D10) / D50, and the tap density satisfies TD(M1)≥2.0g / cm³. 3 .

[0015] Furthermore, in the first metal source, the molar amount of metal source Mi is ≥0.3.

[0016] Furthermore, the first metal source is spherical.

[0017] Furthermore, the metal element in the first metal source is selected from at least two of Mn, Ni, Fe, Cu and Co.

[0018] Furthermore, the first metal source is a metal oxide, a metal carbonate, or a metal hydroxide.

[0019] Furthermore, the conditions for the first and second calcinations are each independent: calcination temperature ≥ 800℃, calcination time ≥ 10h.

[0020] A second aspect of the present invention provides a layered oxide cathode material prepared by the preparation method described in the first aspect.

[0021] Furthermore, the molecular formula of the layered oxide cathode material is Na. x M yO2, where x is the molar amount of Na and y is the molar amount of the metallic element M.

[0022] The third aspect of this invention provides an application of the layered oxide cathode material described in the second aspect in a sodium-ion battery.

[0023] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0024] (1) The preparation method of the layered oxide cathode material of the present invention is simple. The layered oxide cathode material can be obtained by directly calcining the metal source and the sodium source. The method does not require co-precipitation to prepare the precursor, and the raw materials used are low in cost, which helps to reduce the cost of sodium ion cathode material and improve the cost performance of the product.

[0025] (2) In the preparation of layered oxide cathode material, the present invention selects and matches the type and parameters of the first metal source, selects a spherical metal source with large particle size, low SPAN value and high tap density, and controls the median particle size of the spherical metal source to be at least 1.5 times the median particle size of the other metal sources. This can overcome the disadvantage of poor performance caused by direct mixing and calcination of conventional oxides, and improve the prepared layered oxide cathode material to have high capacity, high first efficiency and excellent cycle performance.

[0026] (3) In the preparation of layered oxide cathode material, the present invention controls the sum of the products of the valence state Z and the corresponding molar amount y of each metal source in the first metal source to be S, satisfying 2≤S≤4-x, and the valence state Z of each metal source satisfies 2≤Z≤4, which can significantly reduce the difficulty of redox reaction during calcination and further improve the cycle performance of the prepared layered oxide cathode material.

[0027] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0028] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0029] Figure 1 This is a SEM image of the layered oxide cathode material prepared in Example 1.

[0030] Figure 2 This is a SEM image of the layered oxide cathode material prepared in Example 2.

[0031] Figure 3 This is a SEM image of the layered oxide cathode material prepared in Example 3. Detailed Implementation

[0032] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0033] The first aspect of the present invention provides a method for preparing a layered oxide cathode material, comprising: mixing a first metal source and a sodium source uniformly in an air atmosphere and then performing a first calcination, cooling to room temperature, pulverizing and grinding, and then performing a second calcination to obtain the layered oxide cathode material;

[0034] Among them, the first metal source is at least two kinds, and there is only one metal source Mi whose median particle size D50 is at least 1.5 times the median particle size of the other metal sources;

[0035] The sum of the products of the valence state Z corresponding to the first metal source and the corresponding molar amount y is S, which satisfies 2≤S≤4-x, where x is the molar amount of sodium, and the valence state Z corresponding to the first metal source satisfies 2≤Z≤4.

[0036] In this invention, the sum of the products of the valence state Z and the corresponding molar amount y of the first metal source is controlled to be S, satisfying 2≤S≤4-x. When S≤4-x, excessive reduction reactions can be avoided during calcination, because the entire reaction process is carried out in a high-temperature oxidizing atmosphere. Excessive reduction increases the difficulty of the entire reaction. Therefore, when S≤4-x, the calcination difficulty can be reduced, making it easier to sinter a purer target product, thereby improving the specific capacity and cycle performance of the layered oxide cathode material. When S≥2, excessive oxidation reactions can be avoided, because excessive oxidation reactions mean that more oxygen is needed to participate in the reaction, which also increases the difficulty of the reaction, resulting in poor performance of the prepared cathode material.

[0037] In this invention, when the valence state Z corresponding to the first metal source satisfies 2≤Z≤4, complex redox reactions between the first metal source and the sodium source can be avoided, thus preventing increased reaction difficulty and performance degradation of the layered oxide cathode material. Therefore, when the sum of the product of the valence state Z corresponding to the first metal source and its corresponding molar amount y is S, satisfying 2≤S≤4-x, and simultaneously satisfying 2≤Z≤4, a synergistic effect can be achieved, jointly improving the specific capacity, initial coulombic efficiency, and cycle performance of the prepared layered oxide cathode material. Furthermore, due to reduced sintering difficulty, a purer cathode material is obtained, exhibiting suitable carbon content and superior electrochemical performance. More preferably, the sum of the product S between the valence state Z corresponding to the first metal source and its molar amount y satisfies: 2.4≤S≤4-x, and the valence state Z corresponding to the first metal source satisfies 2≤Z≤3.

[0038] In this invention, it is understood that, among the first metal sources, one and only one metal source has a median particle size D50 that is at least 1.5 times the median particle size of the other metal sources, and this metal source is designated as Mi. The other metal sources refer to metal sources other than Mi. In this invention, by way of example, in one specific embodiment, the molecular formula of the layered oxide cathode material is Na. x Mi y1 M1 y2 M2 y3 O2 has three metals in its molecular formula, which are sourced from metal source Mi, metal source M1 and metal source M2 respectively. If a metal source with a content ≥0.3 is designated as Mi, then the other metal sources are M1 and M2.

[0039] In this invention, limiting the use of one and only one large-particle metal source serves two purposes: ① as a substrate for calcination nucleation, and ② as a grinding medium to promote thorough grinding and mixing of all raw materials, achieving uniform mixing. The inventors unexpectedly discovered through extensive research that limiting the use of one and only one large-particle metal source yields better results. Other raw materials adhere to this large-particle metal source, using it as a nucleus for fusion. If all sources are small-particle metal sources, nucleation cannot occur, making the high-temperature melting process relatively difficult. This is because small-particle metal sources have low material density, causing agglomeration and uneven melting. If all sources are large-particle metal sources, the particles will not fuse sufficiently; only the contacting parts fuse, while the non-contacting parts fuse separately, leading to uneven element distribution or even localized element enrichment. This increases the ion diffusion path and reduces the rate performance of the cathode material.

[0040] In this invention, the median particle size D50 of the metal source Mi is a range consisting of 1.5 times, 1.6 times, 1.8 times, 2 times, 2.1 times, 2.5 times, 2.6 times, 2.8 times, 3 times, 3.5 times, 4 times, and any two of the above values ​​of the median particle size of the other metal sources, preferably 2.5-4 times.

[0041] According to the present invention, specifically, the median particle size of the metal source Mi is 5μm≤D50≤12μm, SPAN<1.2, where SPAN is defined as (D90-D10) / D50, and the tap density satisfies TD(M1)≥2.0g / cm³. 3 .

[0042] In this invention, the inventors discovered that controlling the median particle size of the metal source Mi (5μm≤D50≤12) and SPAN<1.2 can result in a more uniform particle distribution and a denser material, thereby increasing the content of active material per unit volume and thus improving the specific capacity of the battery, while achieving a tap density ≥2.0 g / cm³. 3 It can promote the dense packing of metal source particles and make the contact between particles more stable. During the charging and discharging process of the battery, this dense packing structure helps to reduce the relative movement and poor contact between particles, thereby enhancing the structural stability of the material. At the same time, it can ensure that Mi can act as a relatively solid sphere, serving as a grinding medium during the mixing process, so that all raw materials are fully ground and mixed evenly, improving the cycle stability of the battery.

[0043] In this invention, specifically, the remaining metal sources refer to those with D50 < 5 μm and compaction density TD < 2.0 g / cm³. 3 For the metal source, the SPAN value of the other metal sources is not required for the scheme of the present invention. For example, it can be 1.5, 1.6, 1.8, 1.9, 2.0, etc.

[0044] According to the present invention, in the first metal source, the metal source Mi is any metal element in the molecular formula with a molar amount ≥ 0.3.

[0045] In this invention, it is understood that a metal element with a molar amount ≥ 0.3 in the molecular formula is selected, and its corresponding metal source is designated as Mi, and the median particle size D50 of Mi is guaranteed to be at least 1.5 times the median particle size of the other metal sources.

[0046] In this invention, the element Mi in the molecular formula is limited to having a molar amount ≥ 0.3 because the large-particle-size metal source selected under this condition is an essential metal raw material that is indispensable in the target sodium ion cathode material, rather than an ordinary raw material.

[0047] It is understandable that when there are two or more metal sources in the cathode material with a molar amount of ≥0.3, any metal source with a molar amount of ≥0.3 can be selected as Mi according to actual needs.

[0048] According to some embodiments of the present invention, the first metal source is spherical.

[0049] In this invention, it is understood that the first metal source is spherical because spherical particles have a more uniform surface. Furthermore, since the metal source Mi, being a solid sphere, can simultaneously act as a grinding medium during the mixing process, it promotes thorough grinding and mixing of all raw materials, achieving uniform mixing. During sintering, it facilitates more uniform melting and diffusion, resulting in a more regular morphology and uniform particle size distribution in the final product. This reduces particle agglomeration during sintering, leading to a more uniform crystal structure and improving the battery's initial coulombic efficiency and cycle stability. Moreover, by specifying only one raw material with no morphology requirements for others, it facilitates the use of lower-cost, common oxide raw materials, reducing raw material costs and increasing material selection flexibility.

[0050] According to the present invention, the metal element in the first metal source is selected from at least two of Mn, Ni, Fe, Cu and Co.

[0051] In this invention, selecting at least two of the above-mentioned metal sources can provide different charge transfer capabilities, thereby reducing the difficulty of redox reactions during calcination and avoiding a decrease in the electrochemical performance of the cathode material. By rationally combining the above-mentioned metal elements according to the method provided by this invention, the specific capacity of the cathode material can be comprehensively improved.

[0052] According to the present invention, the first metal source is a metal oxide, a metal carbonate, or a metal hydroxide. In one embodiment of the present invention, considering the availability and economy of the raw materials, spherical Ni or spherical Mn is selected as the designated metal source Mi. For example, spherical Ni3O4, spherical Mn3O4, spherical Mn2O3, etc.

[0053] In this invention, the sodium source can be a sodium source commonly used in the art. Since the sodium source melts / vaporizes first during sintering and actively participates in the fusion process of the first metal source, the median particle size, tap density, and SPAN value of the sodium source do not need to be specifically limited, and common sodium sources can be used, such as those with D50 = 18 μm and TD = 1.2 g / cm³. 3 Battery-grade sodium carbonate.

[0054] According to the present invention, the conditions for the first calcination and the second calcination are each independent of each other: calcination temperature ≥ 800°C and calcination time ≥ 10h.

[0055] In this invention, when the calcination conditions meet the above-mentioned range, sufficient energy can be provided in the redox reaction to allow the sodium source and metal source to react fully and form a stable crystal structure. Especially for the layered oxide cathode material of this invention, it helps sodium ions and metal ions to be uniformly distributed in the crystal structure, forming an ideal layered structure.

[0056] In this invention, a multi-calcination process (one calcination, cooling, and then recalcination) gradually forms a stable crystal structure, optimizes the distribution of metal elements, reduces internal stress and distortion, improves electrochemical performance, and reduces side reactions and carbon content. These steps work together to significantly improve the overall performance of the sodium-ion battery cathode material.

[0057] A second aspect of this invention provides a layered oxide cathode material prepared by the preparation method described in the first aspect, wherein the molecular formula of the layered oxide cathode material is: Na x M y O2, where x is the molar amount of Na and y is the molar amount of the metallic element M.

[0058] In this invention, in the molecular formula of the layered oxide cathode material, M can be 2-6 different metal types, such as M1, M2, M3, M4, M5 and M6, which represent different types of metal elements.

[0059] Specifically, for example, when n is 3, the molecular formula is Na. x M1 y1 M2 y2 M3 y3 O2, where y1 is the molar amount corresponding to M1, y2 is the molar amount corresponding to M2, y3 is the molar amount corresponding to M3, and x is the molar amount of sodium.

[0060] According to some embodiments of the present invention, M is selected from at least two of Mn, Ni, Fe, Cu and Co.

[0061] The third aspect of this invention provides an application of the layered oxide cathode material described in the second aspect in a sodium-ion battery.

[0062] In this invention, it is understood that the layered oxide cathode material described in the second aspect, when applied to sodium-ion batteries, possesses high specific capacity, high initial coulombic efficiency, and excellent cycle performance, wherein the specific capacity is not less than 124 mAh / g, the initial coulombic efficiency is not less than 92%, the capacity retention rate after 100 cycles is not less than 91%, and the carbon content is suitable, ranging from 900 to 1500 ppm.

[0063] The technical solution of the present invention will be further explained below with reference to specific embodiments.

[0064] In the following examples and comparative examples, all reagents were commercially available and of analytical grade purity.

[0065] Performance testing: A mixture of positive electrode material, conductive carbon black SP, and PVDF (polyvinylidene fluoride) at a mass ratio of 80:10:10 was prepared. NMP (N-methylpyrrolidone) was added to create a viscous adhesive solution, which was then coated onto aluminum foil (16 μm thick). The mixture was baked in a vacuum drying oven at 120°C for 12 hours to obtain the positive electrode sheet (active material areal density 5 mg / cm³). 2 Using a sodium metal sheet as the counter electrode (thickness 300±50μm), a glass fiber (Waterman) membrane (thickness 650±50μm), and 1mol / L NaPF6, with EC / DMC = 1:1 as the electrolyte, a 2032 type coin cell was assembled in an Ar protective glove box.

[0066] The conductive carbon black SP was Swiss Temi high conductive carbon black SUPER P, PVDF was purchased from SOLVAY PVDF5130, NMP was a common solvent, metallic Na was purchased from Aladdin, and NaPF6 solution (a mixture of EC and DMC in a volume ratio of EC / DMC = 1:1) was purchased from Alfa.com.

[0067] Electrochemical performance testing: The specific capacity was tested in the voltage range of 2.5-4.0V at room temperature (25℃). The discharge specific capacity at 0.1C was measured by charging and discharging at 0.1C. The first efficiency (first coulombic efficiency) was calculated by dividing the first discharge capacity at 0.1C by the first charge capacity at 0.1C. The discharge capacity retention rate at 1C for 100 cycles was further tested.

[0068] Carbon content: Tested using a carbon-sulfur analyzer.

[0069] Example 1

[0070] This example illustrates the preparation of Na. 0.8 Ni 0.25 Fe 0.3 Mn 0.45 O2 cathode material.

[0071] Since the target product has a high Mn content (≥0.3%), Mn is defined as Mi element, and spherical Mn3O4 with a valence state of +2.667 is selected as the Mn metal source. The relevant indicators are as follows: D50 = 8 μm, SPAN = 1.1, and tap density meets TD = 2.3 g / cm³. 3Other raw materials, such as Ni(OH)₂ with a +2 oxidation state (D₅₀ = 3 μm, TD = 1.4 g / cm³), were selected. 3 The Fe raw material selected is Fe₂O₃ with a +3 oxidation state (D₅₀ = 0.5 μm, TD = 1.3 g / cm³). 3 The sodium source is sodium carbonate (D50 = 18 μm, TD = 1.2 g / cm³). 3 );

[0072] The valence state of the raw material combination satisfies S = 2.667 × 0.45 + 2 × 0.25 + 3 × 0.30 = 2.6.

[0073] The metal source and sodium source were thoroughly mixed according to the target ratio (molar ratio of Na:Ni:Fe:Mn is 0.8:0.25:0.3:0.45), and calcined at 950°C for 15 hours under air atmosphere. After cooling to room temperature, the mixture was pulverized and ground, and then calcined again at 900°C for 10 hours. After pulverization and sieving, the final layered oxide cathode material was obtained.

[0074] Example 2

[0075] This example illustrates the preparation of Na. 0.96 Cu 0.11 Ni 0.22 Fe 0.33 Mn 0.34 O2 cathode material.

[0076] Since the Mn element content is high enough to meet the requirement of ≥0.3%, Mn is defined as the Mi element, and spherical Mn2O3 in the +3 valence state is selected as the Mn raw material. The relevant indicators are as follows: D50=8μm, SPAN=1.1, and tap density meets the requirement of TD=2.5g / cm³. 3 Other raw materials, such as NiCO3 with a +2 valence (D50 = 3 μm, TD = 1.4 g / cm³), were selected. 3 The Fe raw material selected is Fe3O4 with a +2.667 valence (D50 = 0.5 μm, TD = 1.3 g / cm³). 3 The Cu raw material selected is CuO with a +2 oxidation state (D50 = 1.1 μm, TD = 1.8 g / cm³). 3 The sodium source was Na2CO3 (D50 = 18 μm, TD = 1.2 g / cm³). 3 ).

[0077] The valence state of the raw material combination satisfies S=3×0.34+2×0.22+2.667×0.33+2×0.11=2.56.

[0078] The metal source and sodium source were thoroughly mixed according to the target ratio (molar ratio of Na:Cu:Ni:Fe:Mn is 0.96:0.11:0.22:0.33:0.34), and calcined at 850°C for 15 hours under air atmosphere. After cooling to room temperature, the mixture was pulverized and ground, and then calcined again at 850°C for 15 hours. After further pulverization and sieving, the final layered oxide cathode material was obtained.

[0079] Example 3

[0080] This example illustrates the preparation of Na1Ni. 0.35 Fe 0.30 Mn 0.35 O2 cathode material.

[0081] Since the contents of Ni, Fe, and Mn all meet the requirement of ≥0.3%, Ni is selected as the Mi element, and spherical Ni3O4 with a valence state of +2.667 is selected as the Ni raw material. The relevant indicators are as follows: D50 = 12μm, SPAN = 1.0, and tap density meets TD = 2.0 g / cm³. 3 Other raw material Mn was selected as MnO2 with a +4 oxidation state (D50 = 2.5 μm, TD = 1.8 g / cm³). 3 The Fe raw material selected is FeO with a +2 valence (D50 = 1.5).

[0082] μm, TD = 1.4 g / cm 3 The sodium source selected was Na2CO3 (D50 = 18 μm, TD = 1.2 g / cm³). 3 Sodium ion cathode material Na1Ni0.35Fe0.30Mn0.35O2 was prepared.

[0083] The valence state of the raw material combination satisfies S = 2.667 × 0.35 + 2 × 0.3 + 4 × 0.35 = 2.93.

[0084] The metal source and sodium source were thoroughly mixed according to the target ratio (molar ratio of Na:Ni:Fe:Mn is 1:0.35:0.3:0.35), and calcined at 950°C for 20 hours under air atmosphere. After cooling to room temperature, the mixture was pulverized and ground, and then calcined again at 950°C for 20 hours. After pulverization and sieving, the final layered oxide cathode material was obtained.

[0085] Example 4

[0086] Na was prepared according to the method described in Example 2. 0.96 Cu 0.11 Ni 0.22 Fe 0.33 Mn 0.34 O2 cathode material.

[0087] The difference is that the spherical Mn3O4 with a +2.667 valence is replaced with spherical MnO2 with a +4 valence, while keeping other conditions unchanged, and the cathode material is prepared. At this time, S = 4 × 0.45 + 2 × 0.25 + 3 × 0.30 = 3.2.

[0088] Example 5

[0089] Na was prepared according to the method described in Example 2. 0.96 Cu 0.11 Ni 0.22 Fe 0.33 Mn 0.34 O2 cathode material.

[0090] The difference is that the particle size index of Mn3O4 is changed to D50 = 5μm, while other parameters remain unchanged.

[0091] Example 6

[0092] Na was prepared according to the method described in Example 2. 0.96 Cu 0.11 Ni 0.22 Fe 0.33 Mn 0.34 O2 cathode material.

[0093] The difference is that the particle size index of Mn3O4 is changed to D50 = 12μm, while other parameters remain unchanged.

[0094] The cathode materials prepared in Examples 1-6 were assembled into 2032 type coin cells, and their performance was tested. The results are shown in Table 1.

[0095] Table 1

[0096]

[0097]

[0098] The results above show that the cathode materials prepared in Examples 1 and 4 all have high specific capacity (not less than 124 mAh / g), high first-efficiency (not less than 94%), and excellent cycle retention (capacity retention of not less than 91.8% after 100 cycles).

[0099] Examples 1-3 show that different cathode materials were prepared, all of which have high specific capacity and first-efficiency, as well as excellent cycle performance.

[0100] Comparative Example 1

[0101] Na was prepared according to the method in Example 1. 0.8 Ni 0.25 Fe 0.3 Mn 0.45O2 cathode material.

[0102] The difference lies in the use of two large-particle-size raw materials. Specifically, the spherical Mn₂O₃ has a D50 of 8 μm, and the +2 valence nickel hydroxide is replaced with a D50 of 8 μm. All other conditions remain unchanged.

[0103] Comparative Example 2

[0104] Na was prepared according to the method in Example 1. 0.8 Ni 0.25 Fe 0.3 Mn 0.45 O2 cathode material.

[0105] The spherical Mn3O4 with a valence state of +2.667 was modified to have a smaller particle size, satisfying D50 = 4 μm and TD = 1.3 g / cm³. 3 The +2 valence NiOH was replaced with large-particle-size NiOH (D50 = 8 μm, SPAN = 1.1, tap density satisfies TD = 2.3 g / cm³). 3 ), with other conditions remaining unchanged.

[0106] Table 2

[0107]

[0108]

[0109] For the cathode material Na 0.8 Ni 0.25 Fe 0.3 Mn 0.45 Compared to Example 1, Comparative Example 1 had two large-particle-size raw materials, resulting in a decrease in specific capacity, first-efficiency and cycle performance, and an increase in carbon content. This indicates that the presence of two large-particle-size metal raw materials at the same time led to insufficient reaction and a decrease in electrochemical performance.

[0110] Comparative Example 2 used a large-particle-size Ni source with a content of 0.25%, which does not meet the requirement of ≥0.3%. It also showed a simultaneous decrease in capacity, first-efficiency performance, and cycle performance, as well as an increase in carbon content. Combined with the performance of other examples, this demonstrates that the content of large-particle-size raw materials needs to meet the requirement of ≥0.3%.

[0111] Comparative Example 3

[0112] Na1Ni was prepared according to the method described in Example 3. 0.35 Fe 0.30 Mn 0.35 O2 cathode material.

[0113] The difference lies in the following specifications for Ni3O4: D50 = 12 μm, SPAN = 1.0, and tap density satisfying TD = 1.8 g / cm³. 3All other conditions remain unchanged.

[0114] Table 3

[0115]

[0116] For the cathode material Na1Ni 0.35 Fe 0.30 Mn 0.35 O2, compared to Example 3, the tap density of Comparative Example 3 is less than 2.0 g / cm³. 3 This leads to a decrease in specific capacity, first efficiency, and cycle performance.

[0117] Comparative Example 4

[0118] Na was prepared according to the method in Example 2. 0.96 Cu 0.11 Ni 0.22 Fe 0.33 Mn 0.34 O2 cathode material.

[0119] The difference is that Fe3O4 with a +2.667 valence (D50 = 0.5 μm, TD = 2.0 g / cm³) 3 ), with other conditions remaining unchanged.

[0120] Comparative Example 5

[0121] Na was prepared according to the method described in Example 2. 0.96 Cu 0.11 Ni 0.22 Fe 0.33 Mn 0.34 O2 cathode material.

[0122] The difference is that the spherical Mn3O4 with a +2.667 valence is replaced with spherical MnO2 with a +4 valence, and the NiOH with a +2 valence is replaced with Ni2O3 with a +3 valence. With other conditions remaining unchanged, the cathode material is prepared, and S = 3.45.

[0123] Comparative Example 6

[0124] Na was prepared according to the method described in Example 2. 0.96 Cu 0.11 Ni 0.22 Fe 0.33 Mn 0.34 O2 cathode material.

[0125] The difference is that the particle size index of Mn3O4 is changed to D50 = 4.5μm, while other parameters remain unchanged.

[0126] Comparative Example 7

[0127] Na was prepared according to the method described in Example 5. 0.96Cu 0.11 Ni 0.22 Fe 0.33 Mn 0.34 O2 cathode material.

[0128] The difference is that CuO is replaced by Cu2O with a +1 valence, and NiCO3 is replaced by NiO with a +1 valence, which does not satisfy 2≤Z≤4.

[0129] Comparative Example 8

[0130] Na was prepared according to the method described in Example 2. 0.96 Cu 0.11 Ni 0.22 Fe 0.33 Mn 0.34 O2 cathode material.

[0131] The difference is that the particle size index of Mn3O4 is changed to D50 = 14μm, while other conditions remain the same.

[0132] Comparative Example 9

[0133] Na was prepared according to the method described in Example 2. 0.96 Cu 0.11 Ni 0.22 Fe 0.33 Mn 0.34 O2 cathode material.

[0134] The difference is that the SPAN of Mn3O4 is 1.2, while other conditions remain the same.

[0135] Comparative Example 10

[0136] Na was prepared according to the method described in Example 2. 0.96 Cu 0.11 Ni 0.22 Fe 0.33 Mn 0.34 O2 cathode material.

[0137] The difference is that after the metal source and sodium source are fully mixed according to the target ratio, they are calcined at 850℃ for 30 hours.

[0138] Comparative Example 11

[0139] Na was prepared according to the method described in Example 2. 0.96 Cu 0.11 Ni 0.22 Fe 0.33 Mn 0.34 O2 cathode material.

[0140] The difference is that after the metal source and sodium source are fully mixed according to the target ratio, they are calcined at 750℃ for 20 hours.

[0141] Table 4

[0142]

[0143] For the cathode material Na 0.96 Cu 0.11 Ni 0.22 Fe 0.33 Mn 0.34 Compared to Example 2, the performance of Comparative Example 3 decreased, indicating that the tap density of the small-particle-size raw materials was too high, resulting in poor performance and hindering the normal progress of the reaction. This indirectly suggests that, apart from large-particle-size raw materials, the tap density of other raw materials should not be too high (it needs to be <2 g / cm³). 3 It is easy to calcine to produce cathode materials with better performance;

[0144] The performance degradation of Comparative Example 6 indicates that the absence of large-particle-size raw materials that meet the requirements is not conducive to the normal progress of the reaction. This indirectly suggests that the presence of a large-particle-size spherical raw material (≥5μm) in the raw materials helps to fully mix all the raw materials and makes it easier to calcine a cathode material with better performance.

[0145] The poor performance of Comparative Example 7 indicates that when selecting raw materials, the valence state of a single metal raw material should not be too low, and the suitable valence state is ≥+2. That is, in combination with other embodiments and comparative examples, the overall performance needs to satisfy 2≤n1,n2,n3≤4.

[0146] For the cathode material Na1Ni 0.35 Fe 0.30 Mn 0.35 O2, compared to the performance degradation in Example 4, indicates that the tap density of large-diameter spherical raw materials should not be less than 2 g / cm³. 3 That is, the tapped density needs to satisfy TD(M1)≥2.0g / cm³. 3 .

[0147] The performance of Comparative Examples 8 and 9 decreased. Together with Comparative Example 6, this shows that the large-particle-size spherical raw materials need to meet the following conditions: 5μm≤D50≤12μm and SPAN<1.2. This indicates that the physical and chemical properties of the raw materials within the conditions specified by this scheme are conducive to thorough mixing and calcination, thus producing a cathode material with better performance.

[0148] Comparative Example 10, compared to Example 2, showed a significant decrease in material capacity, carbon content, and cycle performance after only one calcination, indicating that a prolonged single calcination cannot achieve the effect of a double calcination.

[0149] Comparative Example 11, compared to Example 2, reduced the sintering temperature to 750°C, resulting in a sharp decline in material properties and extremely high carbon content. This indicates that the temperature did not reach the minimum required for the reaction, and even with secondary sintering, the reaction could not be fully completed.

[0150] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a layered oxide cathode material, characterized in that, include: In an air atmosphere, the first metal source and sodium source are mixed evenly and then subjected to a first calcination. After cooling to room temperature, the mixture is crushed and ground and then subjected to a second calcination to obtain a layered oxide cathode material. Among them, the first metal source is at least two kinds, and there is only one metal source Mi whose median particle size D50 is at least 1.5 times the median particle size of the other metal sources; The sum of the products of the valence state Z corresponding to the first metal source and the corresponding molar amount y is S, which satisfies 2≤S≤4-x, where x is the molar amount of sodium, and the valence state Z corresponding to the first metal source satisfies 2≤Z≤4.

2. The preparation method according to claim 1, characterized in that, The median particle size D50 of the metal source Mi is 2.5-4 times that of the median particle size of the other metal sources.

3. The preparation method according to claim 1, characterized in that, The sum S of the products between the valence state Z and the molar quantity y corresponding to the first metal source satisfies: 2.4≤S≤4-x; And / or, the valence state Z corresponding to the first metal source satisfies 2≤Z≤3.

4. The preparation method according to claim 1, characterized in that, The median particle size of the metal source Mi is 5μm≤D50≤12μm, SPAN<1.2, where SPAN is defined as (D90-D10) / D50, and the tap density satisfies TD(M1)≥2.0g / cm³. 3 ; And / or, in the first metal source, the molar amount corresponding to metal source Mi is ≥0.

3.

5. The preparation method according to claim 1, characterized in that, The first metal source is spherical; And / or, the metal element in the first metal source is selected from at least two of Mn, Ni, Fe, Cu and Co.

6. The preparation method according to claim 5, characterized in that, The first metal source is a metal oxide, a metal carbonate, or a metal hydroxide.

7. The preparation method according to claim 5, characterized in that, The conditions for the first and second calcinations are independent of each other: calcination temperature ≥ 800℃, calcination time ≥ 10h.

8. A layered oxide cathode material prepared by the preparation method according to any one of claims 5-8.

9. The layered oxide cathode material according to claim 8, characterized in that, The molecular formula of the layered oxide cathode material is Na. x M y O2, where x is the molar amount of Na and y is the molar amount of the metallic element M.

10. The application of the layered oxide cathode material according to any one of claims 1 or 8-9 in sodium-ion batteries.

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