Metal oxide precursors, their manufacturing methods, and applications

Abstract

This application discloses a metal oxide precursor, a method for producing the same, and its applications. The metal oxide precursor has a single crystal structure, and the crystal exhibits an incomplete octahedral structure. This incomplete octahedral structure is used as a reference to simulate a fully grown regular octahedral structure, and the degree of crystal growth θ of the octahedral structure is 33%-95%, where θ = L1 / L2, where L1 is the edge length of any crystal growth edge in the octahedral structure, and L2 is the edge length of the corresponding crystal growth edge simulated to a fully grown crystal edge. The metal oxide precursor described in this application has an octahedral structure and, when used in the manufacture of a positive electrode material, can improve structural stability and energy density, and provide batteries with excellent cycle stability.

Description

Cross-reference of related applications

[0001] This application requests priority from the Chinese patent application filed with the China National Intellectual Property Office on December 29, 2023, application number 202311867450.6, with the title of invention "Metal Oxide Precursor, Method for Producing the Same, and Applications," the entire contents of which are incorporated into this application by reference. [Technical Field]

[0002] This application relates to the field of battery technology, and more particularly to metal oxide precursors, their manufacturing methods, and applications. [Background technology]

[0003] The description herein provides only background information relating to the present invention and does not necessarily constitute prior art. Precursors synthesized by coprecipitation typically have a polycrystalline structure, with multiple crystal grains and grain boundaries present in the polycrystalline structure. Not only are the crystal grains relatively loosely arranged, but there are also a relatively large number of grain boundaries and defects. On the one hand, the crystallinity of the cathode material after sintering is low, the crystal grain size is non-uniform, and it is easily crushed during the compaction process. Furthermore, the structure of the cathode material is easily destroyed during the insertion and desorption processes of cations, resulting in poor structural stability of the cathode material and affecting the battery cycle life and stability. On the other hand, the diffusion pathway of cations in the crystal lattice is long, affecting the cation transition rate and the battery discharge rate.

[0004] Precursors produced by conventional spray pyrolysis processes typically have an octahedral structure (as shown in C in Figure 1, where the crystal structure growth is complete). While this structure offers high stability, it exhibits low reactivity and requires higher energy for sintering the cathode, posing significant demands and challenges to the production process and energy consumption. [Overview of the Initiative]

[0005] One of the objectives of the embodiments of this application is to provide a metal oxide precursor, a method for producing the same, and its applications to solve the problem that precursors produced by conventional spray pyrolysis processes usually have an octahedral structure, which has low activity, requires higher energy when sintering the cathode, and poses high demands and challenges to the production process and energy consumption.

[0006] The technical solution relating to the embodiment of this application is as follows:

[0007] In the first embodiment, a metal oxide precursor is provided, the metal oxide precursor having a single crystal structure, and the crystal exhibiting an incomplete octahedral structure, the incomplete octahedral structure being simulated and referenced as a complete octahedral structure, the degree of crystal growth θ of the octahedral structure being 33%-95%, and θ = L1 / L2, where L1 is the edge length of any crystal growth edge of the octahedral structure, and L2 is the edge length of the corresponding crystal growth edge simulated as a crystal edge when fully grown, that is, L2 is the edge length of the crystal edge corresponding to the crystal growth edge L1 in the regular octahedral structure.

[0008] In one example, L1 is 0.1 μm-4.3 μm.

[0009] In one embodiment, the single-crystal particle growth rate η of the metal oxide precursor is L1 / H1, where L1 is the edge length of any crystal growth edge of the octahedral structure and H1 is the single-crystal particle size of the octahedral structure.

[0010] In one embodiment, the single-crystal particle growth rate of the metal oxide precursor is 23%-67%.

[0011] In one embodiment, the single-crystal particle growth rate of the metal oxide precursor is 38%-58%.

[0012] In one embodiment, the single-crystal particle growth rate of the metal oxide precursor is 35%-63%.

[0013] In one embodiment, the size of the single crystal particles of the metal oxide precursor is 0.43 μm - 6.43 μm.

[0014] In one embodiment, the crystal surface area of the metal oxide precursor accounts for 88.72% - 99.99% of the crystal surface area of the metal oxide precursor when the degree of crystal growth is 100%.

[0015] In one embodiment, the crystal volume of the metal oxide precursor accounts for 95.23% - 99.99% of the crystal volume of the metal oxide precursor when the degree of crystal growth is 100%.

[0016] In one embodiment, the ratio of the crystal surface area to the crystal volume of the metal oxide precursor is 1.62 μm -1 - 26.03 μm -1 is.

[0017] In one embodiment, the metal oxide precursor includes a first crystal and / or a second crystal, the degree of crystal growth of the first crystal is 33% ≤ θ1 ≤ 65%, and the degree of crystal growth of the second crystal is 65% < θ2 ≤ 95%.

[0018] In one embodiment, the metal oxide precursor includes a first crystal and / or a second crystal, the edge length of the growth edge in the first crystal is 0.1 μm - 2.95 μm, and the edge length of the growth edge in the second crystal is 0.2 μm - 4.3 μm.

[0019] In one embodiment, the metal oxide precursor includes a first crystal and / or a second crystal, the ratio of the crystal surface area to the crystal volume in the first crystal is 1.63 μm -1 - 26.03 μm -1 is, and the ratio of the crystal surface area to the crystal volume in the second crystal is 1.62 μm -1 - 24.48 μm -1 is.

[0020] In one embodiment, the chemical general formula of the metal oxide precursor is A x M yIt is represented as O2, where 0.9 ≤ x ≤ 1 and 0 ≤ y ≤ 0.1, A is at least one selected from Ni, Fe, Cu, Mn, and Co, and M is at least one selected from Mg, Al, Sn, Ca, W, Ti, Zn, Li, Na, Mo, La, and Zr.

[0021] In a second embodiment, a method for producing the above-mentioned metal oxide precursor is provided, wherein the production method is selected from spray pyrolysis.

[0022] In one embodiment, the pyrolysis temperature of the spray pyrolysis method is 460°C-1110°C.

[0023] In one embodiment, the decomposition time for the spray pyrolysis method is 1 min to 30 min.

[0024] In a third embodiment, a positive electrode material is provided which is produced from the metal oxide precursor described above or from a metal oxide precursor produced by the method described above.

[0025] In a fourth embodiment, a positive electrode sheet is provided, comprising a positive electrode current collector and a positive electrode material layer provided on the surface of the positive electrode current collector, wherein the positive electrode material layer comprises the positive electrode material described above.

[0026] In a fifth embodiment, a secondary battery including the above-described positive electrode sheet is provided.

[0027] The beneficial effects of the metal oxide precursor according to the embodiment of the present application are as follows: The degree of growth of the metal oxide precursor is evaluated using the ratio of the edge length of the crystal growth edge in the octahedral-like structure to the edge length of the crystal edge in the theoretically fully grown regular octahedral structure. When the degree of growth of the metal oxide precursor is 33%-95%, the metal oxide precursor has an overall structure that closely resembles a regular octahedron, and the growth of the six edges of the regular octahedron is incomplete, forming six unsaturated growth cross-sections, thereby causing the metal oxide precursor to have a 14-faced octahedral-like structure. On the other hand, the metal oxide precursor has high symmetry and a regular crystal lattice, resulting in good structural stability. It can maintain good crystallinity during the process of manufacturing the cathode material, which is advantageous in improving the structural stability of the cathode material and the cycle stability of the battery. On the other hand, the cation diffusion pathway in the octahedral-like structure of the metal oxide precursor is short, which is advantageous in improving the cation transition rate, thereby improving storage capacity and providing a high energy density to the cathode material. Furthermore, the metal oxide precursors of the embodiments of this application have improved structural stability and overcome the drawbacks of conventional octahedral precursors, such as low activity, high difficulty in manufacturing cathodes, and high costs, thus possessing high market applicability.

[0028] The beneficial effect of the method for producing metal oxide precursors according to the embodiments of this application is that, by spray pyrolysis, single crystal particles of metal oxide precursors exhibiting an incompletely grown octahedral structure can be produced, and these can be used as a reference to simulate a fully grown octahedral structure, with the crystal growth degree θ of this octahedral structure being 33%-95%. Due to its structural characteristics, the produced metal oxide precursors have properties such as high symmetry, crystal lattice order, and structural stability, improving the structural stability of the cathode material and the cycle stability of the battery. Furthermore, it is advantageous for improving the specific surface area of ​​the reaction activity of the metal oxide precursor, which is advantageous for shortening the ion diffusion pathway, and improving the electrochemical performance of the cathode material, such as ion transition efficiency and storage capacity.

[0029] The beneficial effect of the cathode material according to the embodiment of the present invention is that by using the above-mentioned metal oxide precursor in the manufacture of the cathode material, not only can the crystallinity of the cathode material be improved, but the cathode material can also be given a high energy density, which is advantageous for improving the cycle performance of the battery.

[0030] The beneficial effect of the positive electrode sheet according to the embodiment of the present invention is that by applying a positive electrode material having properties such as high energy density and cycle stability to the positive electrode sheet, the electrochemical performance of the positive electrode sheet, such as energy density and cycle stability, can be improved.

[0031] The beneficial effect of the secondary battery according to the embodiment of the present invention is that by applying a positive electrode sheet having characteristics such as high energy density and cycle stability to the secondary battery, the electrochemical performance of the secondary battery, such as cycle stability and cycle life, can be improved. [Brief explanation of the drawing]

[0032] To more clearly explain the technical concepts in the embodiments of this application, the following drawings, which may be used to describe the embodiments or exemplary technologies, are briefly introduced below. Clearly, the drawings in the following description represent only a few embodiments of this application, and those skilled in the art can obtain other drawings based on these without any creative effort.

[0033] Figure 1 is a schematic diagram of the crystal structure of the metal oxide precursor, where A is a schematic diagram of the octahedral structure of the first crystal, B is a schematic diagram of the octahedral structure of the second crystal, and C is a schematic diagram simulating a fully grown regular octahedral structure. L1 is the edge length of a crystal growth edge in either the first or second crystal octahedral structure, and L2 is the edge length of the corresponding crystal growth edge simulating a crystal edge in the fully grown state; that is, L2 is the edge length of the crystal edge corresponding to the L1 crystal growth edge in the regular octahedral structure.

[0034] Figure 2 is a scanning electron microscope image of the metal oxide precursor produced in Example 1 of the present invention.

[0035] Figure 3 is a scanning electron microscope image of the metal oxide precursor produced in Example 3 of the present invention.

[0036] Figure 4 is a scanning electron microscope image of the metal oxide precursor produced in Example 6 of the present invention.

[0037] Figure 5 is a scanning electron microscope image of the metal oxide precursor produced in Comparative Example 3 of the present invention. [Modes for carrying out the invention]

[0038] To further clarify the purpose, technical solutions, and advantages of this application, the application will be described in more detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are for interpretation purposes only and do not limit the application.

[0039] Furthermore, when a component is referred to as being "fixed" or "attached" to another component, it may be attached to the other component directly or indirectly. When one component is referred to as being "connected" to another component, it may be connected to the other component directly or indirectly. The directions or positional relationships indicated by terms such as "up," "down," "left," and "right" are based on the directions or positional relationships shown in the drawings and are merely for the purpose of facilitating explanation. They do not indicate or imply that the specified device or element has a specific direction or must be configured and operated in a specific direction, and therefore cannot be understood as limiting this application. A person skilled in the art can understand the specific meaning of the above terms depending on the specific situation. The terms "first" and "second" are merely for the purpose of facilitating explanation and do not indicate or imply relative importance or implicitly indicate the number of technical features. "Multiple" means two or more unless otherwise specified.

[0040] To illustrate the technical solution of this application, a detailed description follows with reference to the attached specific drawings and examples.

[0041] Some embodiments of the present invention provide a metal oxide precursor having a single crystal structure, and the crystal exhibits an incompletely grown octahedral structure. As shown in Figure 1, the incompletely grown octahedral structure (shown in A and B in Figure 1) is simulated and referenced as a fully grown regular octahedral structure (shown in C in Figure 1), and the degree of crystal growth θ of the octahedral structure is 33%-95%, with θ = L1 / L2, where L1 is the edge length of any crystal growth edge in the octahedral structure, and L2 is the edge length of the corresponding crystal growth edge simulated as a crystal edge when fully grown, that is, L2 is the edge length of the crystal edge corresponding to the L1 crystal growth edge in the regular octahedral structure.

[0042] Furthermore, the edge length of the crystal edge when growth is complete is the crystal edge length of the metal oxide precursor when the degree of crystal growth is 100% (i.e., when it grows into a regular octahedral structure), i.e., the theoretical edge length. The metal oxide precursor crystal of the embodiment of this application exhibits the characteristics of an incompletely grown octahedral structure, which is easily inherited by the cathode material.

[0043] In the embodiments of the present invention, the degree of growth of the metal oxide precursor is evaluated using the ratio of the edge length of the crystal growth edge in the octahedral structure to the edge length of the crystal edge in a theoretically fully grown regular octahedral structure. When the degree of growth of the metal oxide precursor is 33%-95%, the octahedral structure of the metal oxide precursor has an overall structure very similar to a regular octahedron, and the growth of six edges in the octahedral structure is incomplete, forming six unsaturated growth cross-sections, resulting in an octahedral structure with 14 faces. In this case, the metal oxide precursor of the embodiments of the present invention has at least the following performance advantages.

[0044] On the one hand, the octahedral structure of metal oxide precursors has properties very similar to those of regular octahedral structures, so its crystal structure still has high symmetry and a regular crystal lattice, resulting in a stable and good structure. This allows for good crystallinity to be maintained during the manufacturing process of the cathode material, which is advantageous for improving the structural stability of the cathode material and the cycle stability of the battery. On the other hand, the octahedral structure of metal oxide precursors has 14 faces, which improves its active specific surface area. The diffusion pathway of cations in the octahedral structure of metal oxide precursors is short, which is advantageous for improving the transition rate of cations, thus improving storage capacity and providing a high energy density to the cathode material. If the degree of crystal growth θ of the approximate octahedral structure is less than 33%, properties such as structural stability, symmetry, and crystal lattice regularity of the approximate octahedral structure are impaired, which is disadvantageous for improving the electrochemical performance such as structural stability and cycle stability of the cathode material. When the degree of crystal growth θ of the octahedral structure exceeds 95%, the effect of improving the specific surface area of ​​reaction activity for metal oxide precursors is low, which is unfavorable for shortening the ion diffusion pathway and unfavorable for improving the electrochemical performance of the cathode material, such as ion transition efficiency and storage capacity.

[0045] For example, the degree of crystal growth θ of the octahedral structure may be any typical but non-restrictive point value or an interval value between any two points, such as 33%, 35%, 40%, 50%, 60%, 70%, 80%, 90%, 95%.

[0046] In the metal oxide precursors of the embodiments of this application, the incompletely grown octahedral structure is simulated and referenced as a fully grown regular octahedral structure. Therefore, the edge length L1 of any crystal growth edge in the octahedral structure is lower than the edge length L2 of the crystal edge corresponding to the L1 crystal growth edge in the regular octahedral structure.

[0047] In some embodiments, the edge length L2 of the crystal edges in this fully grown octahedron structure is 0.105 μm–13.03 μm.

[0048] In some embodiments, the edge length L1 of any crystal growth edge in the octahedral structure is 0.1 μm to 4.3 μm. In this case, the degree of crystal growth of the octahedral structure in the metal oxide precursor is calculated using the formula θ = L1 / L2, which gives a degree of crystal growth of 33% to 95%. This is advantageous for maintaining the symmetry, crystal lattice order, and structural stability of the octahedral structure, and is advantageous for improving the structural stability of the cathode material and the cycle stability of the battery. Furthermore, the octahedral structure has 14 faces, which improves its active specific surface area and allows for a higher cation transition rate.

[0049] For example, the edge length L1 of any crystal growth edge in the octahedral structure may be any typical but non-limiting point value or an interval value between any two point values, such as 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 4 μm, or 4.3 μm.

[0050] In the embodiments of this application, since the degree of crystal growth of the metal oxide precursor is 33%-95%, the size of the single crystal particles of the metal oxide precursor is also lower than the size of the single crystal particles of the metal oxide precursor when the degree of crystal growth is 100% (i.e., octahedral structure).

[0051] In some examples, the size of the octahedral single crystal grains ranges from 0.148 μm to 18.43 μm.

[0052] In some embodiments, the size of the single crystal particles of the metal oxide precursor (i.e., the size of the single crystal particles with an octahedral structure) is 0.43 μm–6.43 μm. Under these single crystal particle size conditions, within this range, the particle size belongs to the medium particle size category, allowing for a balance between electrochemical performance and mechanical stability, and providing good overall performance. If the particle size is too large, the ion transport pathway becomes longer, the charge / discharge rate decreases, the specific surface area decreases, the electrochemical reaction rate decreases, affecting the battery capacity and power density, and the electrode structure tends to become non-uniform. If the particle size is too small, particle aggregation and rupture during the charge / discharge process are more likely to occur, affecting cycle performance, and while small sizes improve reaction sites, side reactions also increase, affecting the battery stability and lifespan, and particles that are too small also reduce conductivity.

[0053] For example, the size of the single crystal grains of the metal oxide precursor (i.e., the size of the single crystal grains with an octahedral structure) may be any typical but non-limiting point value or an interval value between any two point values, such as 0.43 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 6 μm, 6.43 μm, etc.

[0054] In some embodiments, the single-crystal particle growth rate of the octahedral structure in the metal oxide precursor of the embodiment of this application can be calculated by measuring the edge length of the crystal growth edge and the size of the single-crystal particle. The single-crystal particle growth rate of the metal oxide precursor can be expressed using the ratio of the edge length L1 of any crystal growth edge in the octahedral structure to the single-crystal particle size H1, and the single-crystal particle growth rate can be denoted as η, where η = L1 / H1. For example, if the edge length L1 of the crystal growth edge in the metal oxide precursor is 0.1 μm-4.3 μm and the size H1 of the single-crystal particle is 0.43 μm-6.43 μm, the single-crystal particle growth rate η obtained by calculation is 23%-67%.

[0055] In some other embodiments, the single-crystal particle growth rate of the octahedral structure in the metal oxide precursor of the embodiment of the present invention can also be estimated by the relationship between the size of the single-crystal particles of the metal oxide precursor when the degree of crystal growth is 100% under ideal conditions and the size of the single-crystal particles of the metal oxide precursor with incomplete growth. For example, under ideal conditions when the degree of crystal growth is 100%, the metal oxide precursor has an octahedral structure consisting of eight equilateral triangles, and if the size of its single-crystal particles is H2,

number

number

[0056] For example, the single-crystal grain growth rates of octahedral structures in metal oxide precursors may be typical but non-limiting arbitrary point values ​​or interval values ​​between any two point values, such as 23%, 30%, 35%, 38%, 40%, 45%, 50%, 55%, 58%, 60%, 63%, and 67%.

[0057] In some embodiments, the single-crystal particle growth rate of the metal oxide precursor is 38%-58%. In this case, a higher single-crystal particle growth rate indicates a higher degree of development, resulting in a more stable structure, greater difficulty in firing the cathode, and higher energy consumption. If the growth rate is too low, it indicates insufficient growth, poor crystallinity, an increase in crystal defects, decreased electrochemical activity of the material, and reduced battery capacity.

[0058] Considering that the degree of crystal growth of the metal oxide precursors in the embodiments of this application is 33%-95%, there are certain differences in the surface area and volume of the crystals of the metal oxide precursors in the embodiments of this application compared to metal oxide precursors with a degree of crystal growth of 100%.

[0059] In some embodiments, the crystal surface area of ​​the metal oxide precursor accounts for 88.72%–99.99% of the crystal surface area of ​​the metal oxide precursor when the degree of crystal growth is 100%. That is, with the crystal surface area of ​​the regular octahedral structure of the metal oxide precursor being 100%, the crystal surface area of ​​the suboctahedral structure is 88.72%–99.99% of the crystal surface area of ​​the regular octahedral structure. In this case, it is advantageous to maintain properties such as structural stability, symmetry, and crystal lattice regularity of the suboctahedral structure, as well as to improve the reaction activity specific surface area of ​​the metal oxide precursor and shorten the ion diffusion pathway, thereby improving the electrochemical performance of the cathode material, such as ion transition efficiency and storage capacity.

[0060] For example, the crystal surface area of ​​the metal oxide precursor may be a typical but non-limiting arbitrary point value or an interval value between any two points, such as 88.72%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 99.99% of the crystal surface area of ​​the metal oxide precursor when the degree of crystal growth is 100%.

[0061] In some embodiments, the crystal volume of the metal oxide precursor accounts for 95.23%–99.99% of the crystal volume of the metal oxide precursor when the degree of crystal growth is 100%. That is, with the crystal volume of the regular octahedral structure of the metal oxide precursor being 100%, the crystal volume of the suboctahedral structure was 95.23%–99.99% of the crystal volume of the regular octahedral structure. In this case, it is advantageous to maintain properties such as structural stability, symmetry, and crystal lattice regularity of the suboctahedral structure, as well as to improve the reaction activity specific surface area of ​​the metal oxide precursor and shorten the ion diffusion pathway, thereby improving the electrochemical performance of the cathode material, such as ion transition efficiency and storage capacity.

[0062] For example, the crystal volume of the metal oxide precursor may be any typical but non-limiting point value or an interval value between any two points, such as 95.23%, 96%, 97%, 98%, 99%, or 99.99% of the crystal volume of the metal oxide precursor when the degree of crystal growth is 100%.

[0063] In some embodiments, when the ratio of the crystal surface area to the crystal volume of the metal oxide precursor is defined as the relative surface area, the relative surface area is 1.62 μm -1 -26.03 μm -1 That is, in the metal oxide precursor, the ratio of the crystal surface area to the crystal volume of the pseudo-octahedral structure is 1.62 μm -1 -26.03 μm -1 In this case, as the degree of growth increases, the surface area and volume corresponding to the crystal also increase, but the ratio between the two decreases. A small ratio means that the particles are large, the structure is more stable, the occurrence of side reactions is reduced, and the battery life is extended. If the ratio is too low, there are too few active sites, restricting the battery reaction rate and rate performance. A large ratio indicates a large number of active sites, which is advantageous for improving the electrochemical reaction rate of the electrode material and can shorten the transport path of ions and electrons inside the material. If the ratio is too high, volume changes are more likely to occur during the cycling process, the structure becomes unstable, and side reactions also increase. When the ratio of the crystal surface area to the volume is within the range of 1.62 μm -1 -26.03 μm -1 it satisfies the macroscopic geometric characteristics of the pseudo-octahedral structure described in the present invention, improves the reaction rate, and improves the cycle stability.

[0064] Exemplarily, the ratio of the crystal surface area to the crystal volume of the metal oxide precursor is defined as the relative surface area. In this case, the relative surface area is 1.62 μm -1 , 2 μm -1 , 5 μm -1 , 10 μm -1 , 12 μm -1 , 15 μm -1 , 18 μm -1 , 20 μm -1 , 22 μm -1 , 24 μm -1 , 26 μm -1 , 26.03 μm -1 and can be any typical but non-limiting point value such as these or an interval value between any two point values.

[0065] The metal oxide precursors of the embodiments of this application satisfy the requirement of having a crystal growth degree of 33%-95% and possess a specific relative surface area, and have a specific crystal surface area ratio and a specific crystal volume ratio compared to metal oxide precursors with a crystal growth degree of 100%. By limiting the structure of the metal oxide precursors of the embodiments of this application, it is advantageous to improve the structural stability of the cathode material and the cycle stability of the battery, thereby improving electrical performance.

[0066] Note that when the degree of crystal growth is 100%, the crystal surface area of ​​the metal oxide precursor is the theoretical crystal surface area, and when the degree of crystal growth is 100%, the crystal volume of the metal oxide precursor is the theoretical crystal volume.

[0067] In some embodiments, as shown in Figure 1, the metal oxide precursor includes a first crystal and / or a second crystal, the first and second crystals having different degrees of crystal growth, as shown in Figure 1A, the lower the degree of crystal growth, the larger the area of ​​the six unsaturated growth cross-sections formed, and as shown in Figure 1B, the higher the degree of crystal growth, the smaller the area of ​​the six unsaturated growth cross-sections formed, becoming closer to the edges.

[0068] In some embodiments, the metal oxide precursor comprises a first crystal and / or a second crystal, where the degree of crystal growth of the first crystal is 33% ≤ θ1 ≤ 65%, and the degree of crystal growth of the second crystal is 65% < θ2 ≤ 95%. In this case, if the degree of crystallinity is too high, the sintering activity of the precursor decreases, the difficulty of sintering increases, the required sintering temperature increases, there is a risk of grain growth and aggregation, and it affects the electrochemical performance. If the degree of crystallinity is too low, the structure is unstable, and it is difficult to sinter a stable single-crystal cathode structure. The degree of growth in the first crystal with a degree of growth of 33% ≤ θ1 ≤ 65% is relatively low, the crystallinity of the crystal is also low, it has high reaction activity and contributes to the formation of a uniform single-crystal structure during the sintering process. The degree of growth in the second crystal with a degree of growth of 65% < θ2 ≤ 95% is relatively high, the crystallinity of the crystal is also higher, the structural stability of the material is improved, it is more stable during the charge and discharge process, capacity decay is reduced, and battery life is extended.

[0069] In some embodiments, the metal oxide precursor comprises a first crystal and / or a second crystal, where the ridge length of the growth edge in the first crystal is 0.1 μm-2.95 μm and the ridge length of the growth edge in the second crystal is 0.2 μm-4.3 μm. In this case, the first crystal with a growth edge length of 0.1 μm-2.95 μm exhibits a low degree of crystal growth, a crystal structure that is more biased towards a subspherical shape, a larger contact area with the electrolyte, improved kinetic performance, a lower sintering temperature, and reduced energy consumption. The second crystal with a growth edge length of 0.2 μm-4.3 μm exhibits a high degree of crystal growth, a crystal structure that is biased towards a regular octahedral structure, high crystallinity, improved conductivity of electrons and ions, and better structural stability during the charge-discharge process.

[0070] In some embodiments, the metal oxide precursor comprises a first crystal and / or a second crystal, where the ratio of the crystal surface area to the crystal volume in the first crystal, i.e., the relative surface area of ​​the first crystal, is 1.63 μm². -1 -26.03μm -1 Therefore, the ratio of the crystal surface area to the crystal volume in the second crystal, i.e., the relative surface area of ​​the second crystal, is 1.62 μm². -1 -24.48μm -1 In this case, the relative surface area is 1.63 μm². -1 -26.03μm -1 The first crystal, as described above, has a low growth rate of 33%-65%. Precursors with a low growth rate have a high relative surface area, more active sites, contribute to improved initial capacity and charge / discharge rate performance, and allow for easier control of the cathode firing process. Relative surface area: 1.62 μm -1 -24.48μm -1 The second crystal, which is the precursor, has a high growth rate of 65%-95%. Precursors with a high growth rate have a high degree of crystallinity, making it easier to improve the conductivity and structural stability of the material.

[0071] In some specific embodiments, the metal oxide precursor comprises either the first or second crystal described above. The metal oxide precursor in the embodiments of the present application may be mainly the first crystal or mainly the second crystal.

[0072] In another specific embodiment, the metal oxide precursor contains both a first and a second crystal. In this case, mixing the first and second crystals of different growth stages makes it easier to improve the conductivity and structural stability of the material, increases reaction activity, facilitates the sintering of a uniform single-crystal cathode, reduces energy consumption, and makes the sintering process easier to control. Furthermore, crystals of different growth stages often have different particle sizes, and the coexistence of large and small particles is advantageous for improving tap density, further increasing the sagger filling volume and reducing sintering costs.

[0073] When the metal oxide precursor contains a mixture of first and second crystals, the embodiments of this application do not limit the distribution ratio of the first and second crystals. For example, the mixing ratio of the first and second crystals may be any typical but non-limiting point value or an interval value between any two point values, such as 30:70, 35:65, 40:60, 45:55, 50:50, 55:45, 60:40, 65:35, or 70:30.

[0074] In some embodiments, the general chemical formula of the metal oxide precursor is A x M y It is represented as O2, where 0.9 ≤ x ≤ 1, 0 ≤ y ≤ 0.1, and x + y = 1, A is at least one selected from Ni, Fe, Cu, Mn, and Co, and M is at least one selected from Mg, Al, Sn, Ca, W, Ti, Zn, Li, Na, Mo, La, and Zr. The metal oxide precursor in the embodiments of this application may be a binary metal oxide, a ternary metal oxide, or a quaternary metal oxide, and it should be understood that the embodiments of this application are not limited thereto.

[0075] The embodiments of this application provide a method for producing the above-mentioned metal oxide precursor, wherein the production method is selected from spray pyrolysis methods.

[0076] The embodiment of this application allows for the production of single-crystal metal oxide precursor particles exhibiting an incompletely grown octahedral structure by spray pyrolysis. When compared to a fully grown octahedral structure, the degree of crystal growth θ for this octahedral structure is 33%-95%. Due to its structural characteristics, the produced metal oxide precursor possesses high symmetry, crystal lattice order, and structural stability, improving the structural stability of the cathode material and the cycle stability of the battery. It also contributes to improving the specific surface area of ​​the reaction activity of the metal oxide precursor, shortening the ion diffusion pathway, and improving the electrochemical performance of the cathode material, such as ion transition efficiency and storage capacity.

[0077] Regarding the specific operation of the spray pyrolysis method, conventional methods can be referred to, and the embodiments of this application omit such a description.

[0078] In some embodiments, the pyrolysis temperature of the spray pyrolysis method is 460°C-1110°C. Under these conditions, at lower pyrolysis temperatures, the decomposition and crystallization processes are slower, resulting in less particle growth, smaller particle size, shorter growth ridges, and a sub-octahedral structure closer to a subspherical shape. As the pyrolysis temperature increases, the decomposition rate increases, particles grow larger, and an optimal thermodynamic equilibrium is gradually reached, resulting in a higher degree of growth, shorter growth ridges, and a sub-octahedral structure closer to a regular octahedron. Within this pyrolysis temperature range, the degree of crystal growth is moderate, improving the conductivity and structural stability of the material, and making it easier to sinter into a single-crystal cathode, while also allowing for easier control of the sintering process.

[0079] Note that the pyrolysis temperature is the operating temperature of the pyrolysis apparatus.

[0080] In some embodiments, the pyrolysis time for the spray pyrolysis method is 1 min to 30 min. Under these pyrolysis time conditions, as the pyrolysis time increases, the pyrolysis becomes more complete, the degree of crystallinity increases, and the degree of growth increases; that is, the longer the growth edge length, the closer the crystal structure is to a regular octahedron structure. At this pyrolysis time, the precursor has high reactive activity, the process of sintering the cathode becomes easier to control, and this contributes to improved capacity and cycle stability.

[0081] For example, the pyrolysis temperature in the spray pyrolysis method may be any typical and non-limiting point value or an interval value between any two points, such as 460°C, 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, or 1100°C, and the pyrolysis time may be any typical and non-limiting point value or an interval value between any two points, such as 1 min, 5 min, 10 min, 15 min, 20 min, 25 min, or 30 min.

[0082] By adjusting the temperature and time of spray pyrolysis, it is advantageous to control the degree of crystal growth of the metal oxide precursor. This allows the metal oxide precursor to inherit the advantages of an octahedral structure while avoiding complete growth, and is advantageous for forming a suboctahedral structure with 14 faces, thereby achieving control over the degree of growth of the metal oxide precursor.

[0083] The embodiments of this application further provide a cathode material manufactured from the above-mentioned metal oxide precursor.

[0084] By using the metal oxide precursor of the embodiment of this application in the manufacture of the cathode material, it is possible not only to improve the crystallinity of the cathode material but also to give the cathode material a high energy density, which is advantageous for improving the cycle performance of the battery.

[0085] The method for manufacturing the positive electrode material will be described by referring to conventional methods, and this will not be explained in the embodiments of this application.

[0086] The embodiment of the present application further provides a positive electrode sheet including a positive electrode current collector and a positive electrode material layer provided on the surface of the positive electrode current collector, wherein the positive electrode material layer includes the above-mentioned positive electrode material.

[0087] The embodiment of this application makes it possible to improve the electrochemical performance of a cathode sheet, such as energy density and cycle stability, by applying a cathode material having characteristics such as high energy density and cycle stability to the cathode sheet.

[0088] The embodiments of the present invention further provide a secondary battery including the above-described positive electrode sheet.

[0089] The embodiment of this invention can improve the electrochemical performance of a secondary battery, such as cycle stability and cycle life, by applying a positive electrode sheet having characteristics such as high energy density and cycle stability to a secondary battery.

[0090] For example, the secondary battery may be a sodium-ion battery.

[0091] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil, and the composite current collector may be formed by forming a metal material on a polymer material substrate, where the metal material includes, but is not limited to, at least one of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, and the polymer material substrate includes, but is not limited to, at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0092] The positive electrode material layer further comprises a binder and a conductive agent, where the binder may be any commercially available binder used in positive electrode sheets, and includes, but is not limited to, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene ternpolymer, vinylidene fluoride-fluoropropylene-tetrafluoroethylene ternpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic acid ester resin, or a binder manufactured by any known method, and is not limited to these. Furthermore, it should be understood that the conductive agent may be any commercially available conductive agent used in sodium-ion batteries, such as carbon black or graphite.

[0093] The metal oxide precursor, its manufacturing method, and its applications will be described below with reference to specific examples. However, these examples are merely illustrative and not intended to limit the scope of the examples of this application, so as can be understood by those skilled in the art. Unless otherwise specified in the examples, the procedures were carried out under normal conditions or conditions suggested by the manufacturer. Unless otherwise specified, the reagents or equipment used are all commercially available, standard products. Example 1

[0094] Nickel nitrate, copper nitrate, iron nitrate, and manganese nitrate are dissolved in pure water in a metal atom molar ratio of 25:5:35:35 to prepare a mixed metal salt solution with a concentration of 200 g / L. First, the mixed metal salt solution is atomized at an atomization pressure of 0.4 MPa and an atomization angle of 45°. Then, it is thermally decomposed at 460°C for 5 minutes to obtain a metal oxide precursor. The general formula of the obtained metal oxide precursor product is represented as NCFM25 / 5 / 35 / 35.

[0095] The surface morphology of the metal oxide precursor produced in this embodiment is shown in Figure 2. The metal oxide precursor has a single-crystal structure, and its morphology is an octahedral structure with six unsaturated growth cross-sections. Furthermore, the large area of ​​the unsaturated growth cross-sections indicates that the degree of crystal growth in the spray pyrolysis process is at a low level.

[0096] Detection revealed that the size of the single crystal grains of the metal oxide precursor is approximately 0.68 μm, the ridge length L1 of the growth ridge in the crystal is approximately 0.48 μm, the theoretical ridge length is calculated to be approximately 1.33 μm, the degree of crystal growth θ of the metal oxide precursor is approximately 36%, and the grain growth rate is approximately 31.6%. At this degree of crystal growth, the ratio of the crystal surface area to the theoretical crystal surface area of ​​the metal oxide precursor is approximately 86.2%, the ratio of the crystal volume to the theoretical crystal volume of the metal oxide precursor is approximately 90.3%, and the relative surface area of ​​the metal oxide precursor is approximately 1.87. Example 2

[0097] Nickel chloride and manganese chloride are dissolved in pure water in a metal atom molar ratio of 35:65 to prepare a mixed metal salt solution with a concentration of 180 g / L. First, the mixed metal salt solution is atomized at an atomization pressure of 0.5 MPa and an atomization angle of 50°. Then, it is thermally decomposed at 800°C for 15 minutes to obtain a metal oxide precursor. The general formula of the obtained metal oxide precursor product is represented as FM35 / 65.

[0098] As can be seen from the SEM measurements, the metal oxide precursor produced in this embodiment has a single-crystal structure, and its morphology is an octahedral structure with six unsaturated growth cross-sections. Furthermore, the area of ​​the unsaturated growth cross-sections is smaller than that of Example 1, indicating that the degree of crystal growth in this spray pyrolysis process is higher than that of Example 1.

[0099] Detection revealed that the size of the single crystal grains of the metal oxide precursor is approximately 2.8 μm, the ridge length L1 of the growth ridge in the crystal is approximately 1.98 μm, the theoretical ridge length is calculated to be approximately 3.6 μm, the degree of crystal growth θ of the metal oxide precursor is approximately 55%, and the grain growth rate is approximately 38.89%. At this degree of crystal growth, the ratio of the crystal surface area to the theoretical crystal surface area of ​​the metal oxide precursor is approximately 91.7%, the ratio of the crystal volume to the theoretical crystal volume of the metal oxide precursor is approximately 93.83%, and the relative surface area of ​​the metal oxide precursor is approximately 6.72. Example 3

[0100] Nickel sulfate and manganese sulfate are dissolved in pure water in a metal atom molar ratio of 25:75 to prepare a mixed metal salt solution with a concentration of 230 g / L. First, the mixed metal salt solution is atomized at an atomization pressure of 0.6 MPa and an atomization angle of 42°. Then, it is thermally decomposed at 1100°C for 25 minutes to obtain a metal oxide precursor. The general formula of the obtained metal oxide precursor product is represented as NM25 / 75.

[0101] The surface morphology of the metal oxide precursor produced in this embodiment is shown in Figure 3. The metal oxide precursor has a single-crystal structure, the area of ​​the unsaturated growth cross-section in the structure is small, and its morphology is close to a regular octahedron structure, indicating a high degree of crystal growth in the spray pyrolysis process.

[0102] Detection revealed that the size of the single crystal grains of the metal oxide precursor is approximately 5.6 μm, the ridge length L1 of the growth ridge in the crystal is approximately 3.96 μm, the theoretical ridge length is calculated to be approximately 4.26 μm, the degree of crystal growth θ of the metal oxide precursor is approximately 93%, and the grain growth rate is approximately 65.77%. At this degree of crystal growth, the ratio of the crystal surface area to the theoretical crystal surface area of ​​the metal oxide precursor is approximately 97.8%, the ratio of the crystal volume to the theoretical crystal volume of the metal oxide precursor is approximately 99.3%, and the relative surface area of ​​the metal oxide precursor is approximately 24.21. Example 4

[0103] Nickel nitrate, cobalt nitrate, and manganese nitrate are dissolved in pure water in a metal atom molar ratio of 83:12:5 to prepare a mixed metal salt solution with a concentration of 220 g / L. First, the mixed metal salt solution is atomized at an atomization pressure of 0.5 MPa and an atomization angle of 48°. Then, it is thermally decomposed at 500°C for 2 minutes to obtain a metal oxide precursor. The general formula of the obtained metal oxide precursor product is represented as NCM83 / 12 / 5.

[0104] Detection revealed that the size of the single crystal grains of the metal oxide precursor was approximately 0.71 μm, the ridge length L1 of the growth ridge in the crystal was approximately 0.25 μm, and the theoretical ridge length was calculated to be approximately 0.76 μm. The degree of crystal growth θ of the obtained metal oxide precursor was approximately 33%, and the grain growth rate was approximately 35.1%. At this degree of crystal growth, the ratio of the crystal surface area to the theoretical crystal surface area of ​​the metal oxide precursor was approximately 66.33%, the ratio of the crystal volume to the theoretical crystal volume of the metal oxide precursor was approximately 88.72%, and the relative surface area of ​​the metal oxide precursor was approximately 7.25. Example 5

[0105] Nickel sulfate, cobalt sulfate, and manganese sulfate are dissolved in pure water in a metal atom molar ratio of 65:15:20 to prepare a mixed metal salt solution with a concentration of 250 g / L. First, the mixed metal salt solution is atomized at an atomization pressure of 0.7 MPa and an atomization angle of 55°. Then, it is thermally decomposed at 1100°C for 30 minutes to obtain a metal oxide precursor. The general formula of the obtained metal oxide precursor product is represented as NCM65 / 15 / 20.

[0106] Detection revealed that the single crystal particle size of the metal oxide precursor was approximately 6.24 μm, the ridge length L1 of the growth ridge in the crystal was approximately 4.3 μm, and the theoretical ridge length was calculated to be approximately 4.53 μm. The degree of crystal growth θ of the obtained metal oxide precursor was approximately 95%, and the grain growth rate was approximately 68.9%. At this degree of crystal growth, the ratio of the crystal surface area to the theoretical crystal surface area of ​​the metal oxide precursor was approximately 99.81%, the ratio of the crystal volume to the theoretical crystal volume of the metal oxide precursor was approximately 99.9%, and the relative surface area of ​​the metal oxide precursor was approximately 1.62. Example 6

[0107] Nickel acetate, cobalt acetate, and manganese acetate were dissolved in pure water in a metal atom molar ratio of 60:10:30 to prepare a mixed metal salt solution with a concentration of 210 g / L. First, the mixed metal salt solution was atomized at an atomization pressure of 0.6 MPa and an atomization angle of 50°, and thermal decomposition was carried out at 550°C for 5 minutes to obtain the first crystal. Without changing any other conditions, the thermal decomposition temperature was changed to 780°C and the thermal decomposition time was set to 18 minutes to obtain the second crystal. The first and second crystals, which had different degrees of growth, were mixed in a 60:40 ratio, and the general formula of the resulting metal oxide precursor product is represented as NCM60 / 10 / 30.

[0108] The surface morphology of the metal oxide precursor produced in this embodiment is shown in Figure 4. The metal oxide precursor has a single-crystal structure and includes two types of octahedral structures with different growth degrees and particle sizes, where the larger particle size indicates a higher degree of crystal growth, and the smaller crystal particle size indicates a lower degree of crystal growth.

[0109] Detection revealed that the size of the single crystal grains of the first crystal in the metal oxide precursor was approximately 2.48 μm, the ridge length L1 of the growth ridge in the crystal was approximately 1.02 μm, the theoretical ridge length was calculated to be approximately 2.49 μm, the degree of crystal growth θ of the metal oxide precursor was approximately 41%, and the grain growth rate was approximately 41.1%. At this degree of crystal growth, the ratio of the crystal surface area to the theoretical crystal surface area of ​​the metal oxide precursor was approximately 73.89%, the ratio of the crystal volume to the theoretical crystal volume of the metal oxide precursor was approximately 92.3%, and the relative surface area of ​​the metal oxide precursor was approximately 2.37.

[0110] The size of the single crystal grains of the second crystal in the metal oxide precursor is approximately 5.09 μm, the ridge length L1 of the growth ridge in the crystal is approximately 3.39 μm, and the theoretical ridge length is calculated to be approximately 3.81 μm. The degree of crystal growth θ of the metal oxide precursor is approximately 89%, and the grain growth rate is approximately 66.6%. At this degree of crystal growth, the ratio of the crystal surface area to the theoretical crystal surface area of ​​the metal oxide precursor is approximately 99.09%, the ratio of the crystal volume to the theoretical crystal volume of the metal oxide precursor is approximately 99.95%, and the relative surface area of ​​the metal oxide precursor is approximately 1.91. Comparative Example 1

[0111] The difference between Comparative Example 1 and Example 1 is that the thermal decomposition temperature is 380°C and the thermal decomposition time is 50 s.

[0112] Under these thermal decomposition conditions, the metal oxide precursor is not completely decomposed, resulting in insufficient crystal growth, a nearly spherical single-crystal structure, almost no prism structure, and sufficiently non-uniform particle size. Detection revealed that the single-crystal particle size of the metal oxide precursor was approximately 0.38 μm, and the growth rate was less than 25%. Comparative Example 2

[0113] The difference between Comparative Example 2 and Example 2 is that the thermal decomposition temperature is 1200°C and the thermal decomposition time is 40 s.

[0114] Under these thermal decomposition conditions, the metal oxide precursor reacts sufficiently, the crystal grows completely, the single crystal structure exhibits a nearly perfect octahedral structure, and the particle size clearly increases. Detection reveals that the size of the single crystal particles of the metal oxide precursor is approximately 9.62 μm, the edge length L1 of the growth edge in the crystal is approximately 6.8 μm, the theoretical edge length is calculated to be approximately 6.83 μm, the degree of crystal growth θ of the metal oxide precursor is approximately 99.5%, and the grain growth rate is approximately 70.7%. At this degree of crystal growth, the ratio of the crystal surface area to the theoretical crystal surface area of ​​the metal oxide precursor is approximately 99.99%, the ratio of the crystal volume to the theoretical crystal volume of the metal oxide precursor is approximately 99.99%, and the relative surface area of ​​the metal oxide precursor is approximately 1.08. Comparative Example 3

[0115] Nickel salt and manganese salt were mixed in a metal atom molar ratio of 25:75 to form a metal salt solution, which was placed in a reaction vessel. Then, sodium hydroxide solution and aqueous ammonia solution were added, nitrogen gas was introduced, the reaction temperature was controlled to 60°C, the pH value was controlled to 10.5, the stirring speed was set to 500 r / min, and the coprecipitation reaction was carried out for 13 hours. Finally, the metal hydroxide precursor was obtained by centrifugal washing and drying.

[0116] The surface morphology of the metal hydroxide precursor produced in this comparative example is shown in Figure 5. The metal hydroxide precursor is composed of secondary particles formed by the aggregation of strip-shaped or sheet-shaped primary particles, exhibiting a polycrystalline structure, and having a sufficiently heterogeneous particle size distribution between 5 μm and 20 μm. Comparative Example 4

[0117] The difference between Comparative Example 4 and Example 4 is that the thermal decomposition temperature is 430°C and the thermal decomposition time is 2 min.

[0118] Under these thermal decomposition conditions, the metal oxide precursor cannot react sufficiently, resulting in insufficient crystal growth, a lack of pronounced octahedral structure in the single crystal, a subspherical structure, extremely small particle size, and severe aggregation.

[0119] The single crystal grain size of the metal oxide precursor is approximately 3.18 μm, the ridge length L1 of the growth ridge in the crystal is approximately 1.09 μm, and the theoretical ridge length is calculated to be approximately 3.39 μm. The degree of crystal growth θ of the metal oxide precursor is approximately 32%, and the grain growth rate is approximately 34.3%. At this degree of crystal growth, the ratio of the crystal surface area to the theoretical crystal surface area of ​​the metal oxide precursor is approximately 65.32%, the ratio of the crystal volume to the theoretical crystal volume of the metal oxide precursor is approximately 88.2%, and the relative surface area of ​​the metal oxide precursor is approximately 1.61. Comparative Example 5

[0120] The difference between Comparative Example 5 and Example 5 is that the thermal decomposition temperature is 1200°C and the thermal decomposition time is 30 min.

[0121] Under these thermal decomposition conditions, the metal oxide precursor reacts sufficiently, the crystal grows completely, the single crystal structure exhibits a nearly perfect octahedral structure, and the particle size clearly increases. Detection reveals that the size of the single crystal particles of the metal oxide precursor is approximately 6.49 μm, the edge length L1 of the growth edge in the crystal is approximately 4.5 μm, the theoretical edge length is calculated to be approximately 4.69 μm, the degree of crystal growth θ of the metal oxide precursor is approximately 96%, and the grain growth rate is approximately 69.3%. At this degree of crystal growth, the ratio of the crystal surface area to the theoretical crystal surface area of ​​the metal oxide precursor is approximately 99.88%, the ratio of the crystal volume to the theoretical crystal volume of the metal oxide precursor is approximately 99.99%, and the relative surface area of ​​the metal oxide precursor is approximately 1.57. Application examples

[0122] The precursors produced in Examples 1-3 and Comparative Examples 1-3 were mixed with sodium carbonate in a 1:1 molar ratio. The mixture was then placed in a muffle furnace and heated to 900°C at a heating rate of 5°C / min under an air atmosphere. After constant temperature sintering for 15 hours, the mixture was allowed to cool naturally, then pulverized and sieved to obtain the cathode material.

[0123] The precursors produced in Examples 4-6 and Comparative Examples 4-5 were mixed with lithium carbonate in a molar ratio of 1:1.05. The mixture was then placed in a muffle furnace and heated to 950°C at a heating rate of 5°C / min under an air atmosphere. After constant temperature sintering for 15 hours, the mixture was allowed to cool naturally, then pulverized and sieved to obtain the cathode material.

[0124] The positive electrode materials produced in Examples 1-3 and Comparative Examples 1-3 were used to create sodium-ion coin batteries, and the discharge ratio capacity and capacity retention rate after 50 cycles were measured under voltage conditions of 2V-4.2V. The positive electrode materials produced in Examples 4-6 and Comparative Examples 4-5 were used to create lithium-ion coin batteries, and the discharge ratio capacity and capacity retention rate after 50 cycles were measured under voltage conditions of 2V-4.0V. The measurement results are shown in Table 1. [Table 1]

[0125] As can be seen from Table 1, the metal oxide precursors produced in Examples 1-3 have good cycle stability as cathode materials for sodium-ion batteries. The cycle stability of Comparative Examples 1-3 is lower in all cases than that of Examples 1-3, and in particular, Comparative Example 3 has poor cycle stability, with a capacity retention rate of only 86.7% after 50 cycles.

[0126] The energy density was calculated based on the battery capacity and average voltage formula, and since mass energy density (Whkg) = capacity (Ah / kg) × average voltage (V), the positive electrode ratio capacity is proportional to the mass energy density. As can be seen from the discharge ratio capacity measurement results, the metal oxide precursors produced in Examples 1-3 and Comparative Example 1-3 were used to produce the positive electrode material for a sodium-ion battery, and the positive electrode materials produced in Examples 1-3 and Comparative Example 1-3 were assembled into a soft pack battery in the same manner, and under the same voltage conditions, Example 1-3 had a higher energy density than Comparative Example 1-3.

[0127] The technical features of the above embodiments can be combined in any way, and for the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as these combinations of technical features are inconsistent, they should be considered to fall within the scope described herein.

[0128] The foregoing describes only preferred embodiments of the present application and does not limit it. Various modifications and changes are possible for those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present application should be included within the scope of the claims.

Claims

1. A metal oxide precursor, The metal oxide precursor has a single crystal structure, and the crystal exhibits an incompletely grown octahedral structure. This incompletely grown octahedral structure is used as a reference to simulate a fully grown regular octahedral structure, and the degree of crystal growth θ of the octahedral structure is 33%-95%, where θ=L 1 / L 2 And here, L 1 L is the edge length of any of the crystal growth edges of the aforementioned octahedral structure. 2 L is the edge length that simulates the crystal edge at the time of complete growth, i.e., L 2 L in the regular octahedron structure 1 This is the edge length of the crystal edge corresponding to the crystal growth edge. A metal oxide precursor characterized by the following features.

2. L 1 The metal oxide precursor according to claim 1, characterized in that the particle size is 0.1 μm to 4.3 μm.

3. The metal oxide precursor according to claim 1, characterized in that the size of the single crystal particles of the metal oxide precursor is 0.43 μm to 6.43 μm.

4. The single crystal particle growth rate η of the metal oxide precursor is η = L 1 / H 1 where L 1 is the edge length of any crystal growth edge in the pseudo-octahedral structure, and H 1 is the single crystal particle size of the pseudo-octahedral structure. The metal oxide precursor according to claim 1, characterized in that

5. The metal oxide precursor according to claim 4, characterized in that the single crystal particle growth rate of the metal oxide precursor is 23%-67%.

6. The metal oxide precursor according to claim 5, characterized in that the single crystal particle growth rate of the metal oxide precursor is 35%-63%.

7. The metal oxide precursor according to claim 6, characterized in that the single crystal particle growth rate of the metal oxide precursor is 38%-58%.

8. The metal oxide precursor according to claim 1, characterized in that the crystal surface area of ​​the metal oxide precursor accounts for 88.72% to 99.99% of the crystal surface area of ​​the metal oxide precursor when the degree of crystal growth is 100%.

9. The metal oxide precursor according to claim 1, characterized in that the crystal volume of the metal oxide precursor accounts for 95.23% to 99.99% of the crystal volume of the metal oxide precursor when the degree of crystal growth is 100%.

10. The ratio of the crystal surface area to the crystal volume of the aforementioned metal oxide precursor is 1.62 μm². -1 -26.03μm -1 The metal oxide precursor according to claim 1, characterized in that it is the same as described in claim 1.

11. The metal oxide precursor comprises a first crystal and / or a second crystal, wherein the degree of crystal growth of the first crystal is 33% ≤ θ 1 ≤65%, and the degree of crystal growth of the second crystal is 65% < θ 2 A metal oxide precursor according to any one of claims 1 to 10, characterized in that it is ≤95%.

12. The metal oxide precursor according to any one of claims 1 to 10, wherein the metal oxide precursor comprises a first crystal and / or a second crystal, the ridge length of the growth ridge in the first crystal is 0.1 μm to 2.95 μm, and the ridge length of the growth ridge in the second crystal is 0.2 μm to 4.3 μm.

13. The metal oxide precursor comprises a first crystal and / or a second crystal, wherein the ratio of the crystal surface area to the crystal volume in the first crystal is 1.63 μm². -1 -26.03μm -1 The ratio of the crystal surface area to the crystal volume in the second crystal is 1.62 μm². -1 -24.48μm -1 A metal oxide precursor according to any one of claims 1 to 10, characterized in that it is the metal oxide precursor described in any one of claims 1 to 10.

14. The general chemical formula of the metal oxide precursor is A x M y O 2 The metal oxide precursor according to claim 1 is characterized in that it is expressed as follows, where 0.9 ≤ x ≤ 1 and 0 ≤ y ≤ 0.1, A is at least one selected from Ni, Fe, Cu, Mn, and Co, and M is at least one selected from Mg, Al, Sn, Ca, W, Ti, Zn, Li, Na, Mo, La, and Zr.

15. A method for producing a metal oxide precursor according to any one of claims 1 to 14, selected from a spray pyrolysis method.

16. The method for producing a metal oxide precursor according to claim 15, characterized in that the thermal decomposition temperature of the spray pyrolysis method is 460°C to 1110°C.

17. The method for producing a metal oxide precursor according to claim 15, characterized in that the thermal decomposition time of the spray thermal decomposition method is 1 min to 30 min.

18. A cathode material produced from a metal oxide precursor according to any one of claims 1 to 14 or a metal oxide precursor produced by the method described in any one of claims 15 to 17.

19. It is a positive electrode sheet, The positive electrode sheet includes a positive electrode current collector and a positive electrode material layer provided on the surface of the positive electrode current collector, wherein the positive electrode material layer includes the positive electrode material described in claim 18. A positive electrode sheet characterized by the following features.

20. A secondary battery characterized by including the positive electrode sheet described in claim 19.

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