Sodium ion battery positive electrode material, and preparation method therefor and use thereof

Abstract

Embodiments of the present application provide a sodium ion battery positive electrode material, and a preparation method therefor and a use thereof. The sodium ion battery positive electrode material comprises a sodium-based metal oxide, the chemical formula of the sodium-based metal oxide being NaaNi1-x-y-i-j-kFexMnyM1 iM2 jM3 kOb, wherein 0.5≤a≤1.2, 1.8≤b≤2.2, 0<x<1, 0<y<1, 0<i≤0.1, 0<j≤0.1, 0≤k≤0.1, 0<i+j+k≤0.1, M1, M2, and M3 represent doped elements, M1 is selected from at least one of Cu and Co, M2 is selected from at least one of Ce and Sr, and M3 is a metal element different from M1 and M2. The specific elements M1 and M2 are introduced into the sodium ion battery positive electrode material for co-doping, so that the positive electrode material has high sphericity and a large particle size, and thus has high compaction density, good cycle performance, and the like.

Description

Sodium battery positive electrode material and its preparation method and application

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of China on February 29, 2024, with application number 202410234511.3 and application name “Sodium battery positive electrode materials, preparation methods and applications thereof”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of sodium ion batteries, and in particular to a sodium battery positive electrode material and a preparation method and application thereof. Background Art

[0003] Because sodium resources are abundant and inexpensive on Earth, sodium-ion batteries are relatively inexpensive to manufacture, making them a promising candidate for meeting the future demand for low-cost large-scale energy storage devices. The cathode materials widely used in sodium-ion batteries are layered sodium-based transition metal oxides, which typically have a flat, sheet-like structure with small particle size and a low compaction density, resulting in a low volumetric energy density for sodium batteries. Therefore, it is necessary to provide a sodium-based cathode material with a high compaction density. Summary of the Invention

[0004] In view of this, the present application provides a sodium-ion positive electrode material and its preparation method and application, so that the sodium-ion battery using the sodium-ion positive electrode material can have a higher volume energy density, good cycle performance, higher charging capacity, etc.

[0005] The first aspect of the embodiment of the present application provides a sodium positive electrode material, wherein the sodium positive electrode material comprises a sodium-based metal oxide, and the chemical formula of the sodium-based metal oxide is Na a Ni1-xyij-kFe x Mn y M 1 i M 2 j M 3 k O b , wherein, 0.5≤a≤1.2, 1.8≤b≤2.2, 0<x<1, 0<y<1, 0<i≤0.1, 0<j≤0.1, 0≤k≤0.1, and 0<i+j+k≤0.1, and the values ​​of a, b, x, y, i, j, and k make the sodium-based metal oxide electrically neutral; M 1 、M 2 、M 3 represents the doping element, the M 1 At least one selected from Cu and Co, wherein M 2 At least one selected from Ce and Sr, the M 3Different from the M 1 、The M 2 of metal elements.

[0006] By synergistically doping sodium-based metal oxides with the above-mentioned multiple elements in appropriate amounts, their sphericity and particle size can be improved, ensuring that the powder or electrode compaction density of the sodium battery positive electrode material is high and reducing its specific surface area, thereby making the sodium battery using the positive electrode material have high capacity, high volume energy density, and good cycle performance.

[0007] In some embodiments of the present application, the M 3 One or more selected from Ti, Zr, Zn, Mg, Ca, V, Cr, Mo, Nb, Y, Sn, Sb, Al, Li, and K.

[0008] In some embodiments of the present application, the M 2 is Ce, or is Ce and Sr. In this case, it is more conducive to improving the charge capacity and sphericity of the above-mentioned sodium battery positive electrode material.

[0009] In some embodiments of the present application, 0<i+j+k≤0.08. 1 、M 2 、M 3 The total doping amount of elements is low, which is more conducive to the higher structural stability and better cycle performance of the positive electrode material.

[0010] In some implementations of the present application, 0.01≤i≤0.06.

[0011] In some implementations of the present application, 0.01≤j≤0.05.

[0012] In some implementations of the present application, 0≤k≤0.03.

[0013] In some embodiments of the present application, i is greater than or equal to j. In this case, it is more conducive to the above-mentioned sodium-based metal oxide to balance higher sphericity, high capacity and good cycle performance.

[0014] In the embodiment of the present application, the sodium cathode material is a spherical or quasi-spherical particle. The apparent morphology of the sodium cathode material is not the common flat sheet structure in the field, but a spherical or quasi-spherical structure, which is more conducive to improving the compaction density of the sodium cathode material.

[0015] In the embodiment of the present application, the average particle sphericity of the sodium-based positive electrode material is in the range of 0.75-1. In some embodiments of the present application, the average particle sphericity of the sodium-based positive electrode material is in the range of 0.85-1. The higher average particle sphericity can reflect that the sodium-based positive electrode material of the embodiment of the present application is a particle with a rounded morphology, the exposure degree of its electrochemically active surface is increased, and the kinetic performance can be significantly improved. At the same time, it can achieve denser packing and high compaction density, which is beneficial to the improvement of the energy density of the sodium battery, and the uniformity of its ability to intercalate and deintercalate sodium ions is improved, which is beneficial to improving the battery cycle performance.

[0016] In the embodiment of the present application, the number of particles with a sphericity of less than 0.75 in the sodium-ion positive electrode material is less than 30%. The number of particles of the sodium-ion positive electrode material with low sphericity is relatively low in the overall sodium-ion positive electrode material, thereby ensuring that the material has a high average particle sphericity, a high compaction density, and good dynamic performance.

[0017] In the embodiment of the present application, the aspect ratio of the particles having a sphericity of less than 0.75 is within a range of greater than 1 and less than 3. Even particles with relatively low sphericity still have a relatively small aspect ratio, which is much lower than the aspect ratio of conventional flat sheet materials. Their apparent morphology is relatively rounded, and their presence does not significantly affect the dynamic performance and compaction density of the positive electrode material.

[0018] In the embodiment of the present application, the particle size D50 of the sodium cathode material is 5 μm-20 μm. A sodium cathode material with a suitable average particle size is conducive to the material having a high powder compaction density, a suitably high charge capacity, and good kinetic performance.

[0019] In the embodiment of the present application, the specific surface area of ​​the sodium positive electrode material is 0.15m 2 / g-0.35m 2 By controlling the above-mentioned doping elements and their contents, the sodium cathode material of the present application can have a relatively high average particle sphericity while its specific surface area is not too large, which is conducive to the material having good cycle stability.

[0020] In some embodiments of the present application, the sodium positive electrode material further includes a metal oxide coating layer coated on the surface of the sodium-based metal oxide; the metal element in the metal oxide coating layer is selected from the M contained in the sodium-based metal oxide. 1 、The M 2 、The M 3 One or more of .

[0021] In the embodiment of the present application, the sodium cathode material has a compaction density of 3.2 g / mL to 3.6 g / mL at 200 MPa. The sodium cathode material has a high compaction density, which is beneficial to improving the overall capacity of the battery.

[0022] In the embodiment of the present application, the sodium cathode material has a gram capacity of 140-160 mAh / g. The sodium cathode material has a high gram capacity, which is beneficial to improving the overall capacity of the battery.

[0023] The second aspect of the embodiment of the present application provides a method for preparing the sodium battery positive electrode material as described in the first aspect of the embodiment of the present application, comprising the following steps:

[0024] The first precursor of the sodium-based metal oxide is mixed with a sodium source and a doping element M source, and then calcined to obtain a sodium cathode material;

[0025] Alternatively, the second precursor of the sodium-based metal oxide is mixed with a sodium source and a doping element M' source and then calcined to obtain a sodium cathode material;

[0026] Alternatively, the third precursor of the sodium-based metal oxide is mixed with a sodium source and then calcined to obtain a sodium cathode material;

[0027] The first precursor contains Ni, Fe and Mn elements; the second precursor contains Ni, Fe, Mn and M' elements, and the M' and M' together constitute all the doping elements M contained in the sodium-based metal oxide; the M includes the M 1 and M 2 , or including the M 1 、M 2 and M 3 ; The third precursor contains Ni, Fe, Mn and the doping element M.

[0028] The preparation method of the above-mentioned sodium battery positive electrode material has a simple process, is easy to operate, and is suitable for large-scale industrial production to produce the sodium battery positive electrode material required by the aforementioned application.

[0029] A third aspect of an embodiment of the present application provides a positive electrode plate, which includes a positive electrode collector and a positive electrode material layer arranged on the positive electrode collector, and the positive electrode material layer includes the sodium-ion positive electrode material described in the first aspect of the embodiment of the present application, or the sodium-ion positive electrode material prepared according to the preparation method described in the second aspect of the embodiment of the present application.

[0030] The positive electrode sheet prepared using the sodium-ion positive electrode material of the embodiment of the present application has a higher compaction density, and thus the sodium-ion battery using the positive electrode sheet has a higher volume energy density, and at the same time has a higher capacity and good cycle performance.

[0031] A fourth aspect of the present invention provides a sodium-ion battery, comprising the positive electrode sheet described above. In some embodiments, the sodium-ion battery comprises a positive electrode sheet, a negative electrode sheet, and an electrolyte positioned between the positive electrode sheet and the negative electrode sheet. The electrolyte may be an electrolyte solution or a solid / semi-solid electrolyte membrane.

[0032] Since the sodium ion battery uses the above-mentioned sodium cathode material of the present application, the sodium ion battery can have a higher volume energy density, a higher charge specific capacity, good cycle performance, etc.

[0033] A fifth aspect of the present application provides an electric device, the electric device comprising the sodium ion battery described in the fourth aspect of the present application, wherein the electric device comprises an electronic device or a mobile device.

[0034] By using the sodium ion battery provided in the embodiment of the present application to power the electrical device, the user experience and market competitiveness of the electrical device can be improved.

[0035] A sixth aspect of the present application provides an energy storage system, comprising the sodium-ion battery described in the fourth aspect of the present application. The energy storage system comprises at least one battery pack, wherein the battery pack comprises a plurality of sodium-ion batteries as described in the fourth aspect of the present application.

[0036] The sodium-ion battery used in this energy storage system has a high volume energy density, good rate performance and cycle stability, so that the energy storage characteristics of the energy storage system are better. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG1 is a schematic structural diagram of a positive electrode plate provided in an embodiment of the present application.

[0038] FIG2 is a schematic structural diagram of a sodium ion battery provided in an embodiment of the present application.

[0039] FIG3 is a schematic structural diagram of an electronic device provided in an embodiment of the present application.

[0040] FIG4 is a schematic structural diagram of a mobile device provided in an embodiment of the present application.

[0041] FIG5 is a schematic structural diagram of an energy storage system provided in an embodiment of the present application.

[0042] FIG6 shows a cross-sectional scanning electron microscope (SEM) photograph of the positive electrode material prepared in Example 1 and its energy spectrum analysis results.

[0043] FIG7 is a SEM photograph of the positive electrode material prepared in Example 2 of the present application.

[0044] FIG8 is a SEM photograph of the positive electrode material prepared in Example 3 of the present application. DETAILED DESCRIPTION

[0045] The embodiments of the present application will be described below with reference to the accompanying drawings.

[0046] The layered sodium-based transition metal oxide cathode materials used in sodium batteries are mostly flat, sheet-like structures with low compaction density and low capacity volatility. This results in low volumetric energy density and low initial charge specific capacity. To address this issue, the present invention provides a sodium battery cathode material with high compaction density and high capacity volatility.

[0047] Specifically, the present invention provides a sodium cathode material, which includes a sodium-based metal oxide, the chemical formula of which is Na a Ni1-xyij-kFe x Mn y M 1 i M 2 j M 3 k O b , wherein, 0.5≤a≤1.2, 1.8≤b≤2.2, 0<x<1, 0<y<1, 0<i≤0.1, 0<j≤0.1, 0≤k≤0.1, and 0<i+j+k≤0.1, and the values ​​of a, b, x, y, i, j, and k make the sodium-based metal oxide electrically neutral; M 1 、M 2 、M 3 represents the doping element, the M 1 At least one selected from Cu (copper), Co (cobalt), the M 2 At least one selected from Ce (cerium), Sr (strontium), the M 3 Different from the M 1 、The M 2 of metal elements.

[0048] Since the above i and j are greater than 0, the sodium-based metal oxide of the present application must contain the doping element M 1 and M 2 , where M 1 Doping of elements is mainly used to control the exposure of the electrochemically active surface in sodium-based metal oxides, thereby improving the sphericity of the material and increasing the compaction density of the material. 2 Elements can play a role in fluxing, M 2The doping of M can increase the particle size of sodium-based metal oxides and also help to increase the compaction density of the material. 1 and M 2 The co-doping of M can make the sodium-based metal oxide have a higher sphericity and a larger particle size, which is beneficial to improve the compaction density. 2 The capacity reduction caused by the increase in material particle size due to doping can be 1 The exposure of the crystal surface caused by doping is suppressed to a certain extent, because M 1 The problems of crystal surface exposure and increased specific surface area caused by doping can be solved by M 2 The increase in material particle size caused by doping is suppressed to a certain extent. Thus, the sodium-based metal oxide can take into account a higher compaction density, a higher capacity and good cycle stability. In some cases, the above sodium-based metal oxide is also doped with M 3 elements, which can further improve the electrochemical properties of the material, such as capacity, cycle stability, etc. In addition, controlling the M 1 、M 2 、M 3 The total doping amount of elements does not exceed 10%, which can ensure that the doping of these elements does not affect the structural stability of the material and ensures that its electrochemical cycle performance is better and the volume energy density is higher.

[0049] Therefore, the above-mentioned sodium battery positive electrode material in the embodiment of the present application can improve the sphericity and particle size of the layered sodium-based metal oxide through appropriate synergistic doping of multiple elements, ensuring that the compaction density of the positive electrode material powder or the battery positive electrode sheet is high, while the battery capacity is high and the cycle performance is good.

[0050] In this application, the general formula Na a Ni1-xyij-kFe x Mn y M 1 i M 2 j M 3 k O b The sodium-based metal oxide represented by M can be called doped sodium-based metal oxide. 1 、M 2 、M 3 Elements are uniformly doped in the lattice of sodium-based metal oxides, among which M 1 、M 2 The elements can specifically replace the transition metal sites, such as replacing part of Ni, Fe, and Mn elements; 3 Elements can replace the transition metal site or Na site.

[0051] In some embodiments of the present application, the above-mentioned sodium-based metal oxide may be an O3 phase, or a P2 phase, or a stacked phase of O3 and P2. The above-mentioned O3 phase and P2 phase refer to materials that do not undergo any charging or discharging reactions. The P2 phase refers to the triangular prism coordination of the oxygen coordination environment of the sodium ions in the material crystal lattice, and the O3 phase refers to the octahedral coordination of the oxygen coordination of the sodium ions in the material crystal lattice. The sodium-based metal oxide material in the P2 phase may have high ionic conductivity, good structural stability and relatively good environmental stability. The sodium-based metal oxide in the O3 phase has a high capacity; the sodium-based metal oxide containing the stacked phase of O3 and P2 can compromise the various properties of the P2 phase and the O3 phase. In the present application, when a is greater than 1.0, the above-mentioned sodium-based metal oxide may be referred to as a sodium-rich metal oxide. In some embodiments, a=1.0, b=2.0.

[0052] In some embodiments, the M 2 Ce, or Ce and Sr. When the types of other doping elements are the same and the total amount of doping elements is the same, Ce element alone or Ce and Sr elements are used as M 2 Doping elements, compared to using only Sr as M 2 Doping elements are more helpful in improving the sphericity and charging capacity of the above-mentioned sodium battery positive electrode materials.

[0053] In the embodiment of the present application, the M 3 One or more selected from the group consisting of Ti (titanium), Zr (zirconium), Zn (zinc), Mg (magnesium), Ca (calcium), V (vanadium), Cr (chromium), Mo (molybdenum), Nb (niobium), Y (yttrium), Sn (tin), Sb (antimony), Al (aluminum), Li (lithium), and K (potassium). In some embodiments, M 3 One or more elements selected from Ti, Zr, Zn, Mg, and Ca. These five elements are easier to achieve uniform doping in the sodium-based metal oxide and are beneficial for improving the capacity and stability of the material.

[0054] In some embodiments of the present application, 0<i+j+k≤0.08. For example, i+j+k is specifically 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, etc. 1 、M 2 、M 3 The total doping amount of elements is low, which is more conducive to the higher structural stability and better cycle performance of the positive electrode material.

[0055] In some embodiments of the present application, 0.01≤i≤0.06. 1The appropriate doping of elements is beneficial for ensuring that the electrochemically active surface of the sodium-based metal oxide is appropriately exposed, ensuring high sphericity, while not significantly affecting the cycling stability of the material. For example, i can be 0.015, 0.02, 0.03, 0.04, 0.05, 0.055, etc.

[0056] In some embodiments of the present application, 0.01≤j≤0.05. 2 The appropriate doping of elements is beneficial for ensuring that the particle size of the sodium-based metal oxide is appropriately increased, thereby improving its compaction density, while not significantly affecting the specific capacity of the material. For example, j can be 0.015, 0.02, 0.03, 0.04, 0.045, 0.05, etc.

[0057] In an embodiment of the present application, the ratio of i to j (i.e., i / j) is in the range of 0.5-2.5. For example, i / j is specifically 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 2.0, 2.2, 2.4, etc. In some embodiments, i is greater than or equal to j, for example, i / j is in the range of 1.0-2.2. In this case, it is more conducive to the above-mentioned sodium-based metal oxide to balance higher sphericity, high capacity and good cycle performance.

[0058] In some embodiments of the present application, 0≤k≤0.03. 3 In some embodiments, k is less than i, and k is less than j.

[0059] In the embodiment of the present application, the sodium cathode material is in the form of spherical or quasi-spherical particles. The spherical or quasi-spherical appearance can make the sodium cathode material have a higher compaction density and better dynamic performance.

[0060] In the embodiment of the present application, the average particle sphericity of the sodium positive electrode material is in the range of 0.75-1.0. Wherein, the "average particle sphericity" is the average result of the sphericity of multiple sodium positive electrode material particles. For example, the area equivalent sphericity of a single sodium positive electrode material particle (equal to the ratio of the area equivalent radius d1 of the particle to the circumference equivalent radius d2 of the particle) can be obtained from a two-dimensional SEM photograph containing multiple (such as more than 50) sodium positive electrode material particles, and the average value of the sphericity of multiple sodium positive electrode material particles can be calculated based on this. Wherein, d1 can be calculated based on the projected area S of the particle, and d2 can be calculated based on the circumference L of the projected outline of the particle: S=πd l 2; L = 2πd2. For another example, the volume equivalent sphericity of a single sodium cathode material particle (equal to the ratio of the volume equivalent radius d3 of the particle to its surface area equivalent radius d4) can be obtained from a three-dimensional SEM photograph containing multiple (e.g., more than 50) sodium cathode material particles, and the average value of the sphericity of the multiple sodium cathode material particles can be calculated based on this. Wherein, d3 can be calculated based on the volume V of the particle, and d4 can be calculated based on the surface area S' of the particle: V = 4πd3 3 / 3; S'=πd4 2 The closer the sphericity of the particles is to 1, the closer the morphology of the particles is to a standard sphere.

[0061] Based on the doping element M in the above sodium-based metal oxide 1 、M 2 The type control and the total doping amount control can improve the sphericity of the sodium-based metal oxide, so that the average particle sphericity of the overall sodium-based cathode material is higher (above 0.75), the macroscopic structure is more rounded, rather than a flat sheet structure, the exposure of the electrochemically active surface of the material is increased, the kinetic performance can be significantly improved, and thus it is beneficial to improve the rate performance of the sodium battery. And the rounded sodium-based cathode material particles are easier to form dense packing, and the compaction density of the material is higher, which can increase the energy density of the sodium battery. In addition, the deintercalation and extraction of sodium ions (Na + ) has a certain improvement in uniformity compared to the sheet structure, which can further improve the cycle performance of sodium batteries.

[0062] In some embodiments of the present application, the average particle sphericity of the sodium positive electrode material is in the range of 0.8-1.0, and can further be in the range of 0.85-1.0. For example, the average particle sphericity is 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.98, 0.99, etc. In some embodiments, the average particle sphericity is 0.89-1.0.

[0063] In the embodiment of the present application, in the sodium-based positive electrode material, the number of sodium-based positive electrode material particles with a particle sphericity of less than 0.75 accounts for less than 30%. The number of sodium-based positive electrode material particles with low sphericity accounts for a low proportion in the overall sodium-based positive electrode material, thereby ensuring that the average particle sphericity of the material is high, the dynamic performance is better, and the compaction density is high. In some embodiments, the number ratio can be less than or equal to 25%, less than or equal to 20%, less than or equal to 15%, less than or equal to 10%, less than or equal to 8%, less than or equal to 6%, less than or equal to 5%, etc.

[0064] In the embodiment of the present application, the particle width-to-thickness ratio of the sodium battery positive electrode material with a particle sphericity of less than 0.75 is within the range of greater than 1 and less than 3. Even for particles with relatively low sphericity, the width-to-thickness ratio is still small, much lower than the width-to-thickness ratio of conventional flat sheet materials, and its apparent morphology is relatively rounded, and its dynamic performance is still relatively high; such particles are present in the overall positive electrode material and will not affect the dynamic performance and compaction density of the positive electrode material too much. Among them, "width-to-thickness ratio" refers to the ratio of the maximum lateral dimension of the particle to its thickness. The maximum lateral dimension of particles with a sphericity of less than 0.75 is greater than the thickness. "Maximum lateral dimension" can specifically refer to the distance between the two largest points on a cross section perpendicular to the thickness direction. For example, when the cross section is a polygon, the maximum lateral dimension can be the diameter of the circumscribed circle of the polygon. The above-mentioned width-to-thickness ratio can be obtained from a scanning electron microscope photograph of the material. In some embodiments, the aspect ratio of the sodium battery positive electrode material particles having a particle sphericity of less than 0.75 may be less than or equal to 2.8, less than or equal to 2.5, less than or equal to 2.2, less than or equal to 2.0, less than or equal to 1.8, less than or equal to 1.5, less than or equal to 1.4, etc.

[0065] In the embodiment of the present application, the sodium cathode material is a single crystal or quasi-single crystal particle. Compared with polycrystalline sodium cathode materials, single crystal or quasi-single crystal sodium cathode materials have a higher degree of crystallinity, a more stable bulk structure, and better cycle performance.

[0066] In an embodiment of the present application, the particle size D50 of the sodium-based positive electrode material is in the range of 5 μm to 20 μm. That is, the average particle size of the aforementioned sodium-based positive electrode material is in the range of greater than or equal to 5 μm to less than or equal to 20 μm. Controlling the average particle size of the sodium-based positive electrode material within the above range can not only prevent the average particle size of the positive electrode material from being too large, which will lengthen the diffusion path of sodium ions and deteriorate the rate performance of the material, but also prevent the compaction density of the material from being too low due to the average particle size of the positive electrode material being too small. For example, the particle size D50 can be specifically 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm or 19 μm, etc. The particle size D50 can be obtained from the particle size distribution curve of the sodium cathode material measured based on the laser diffraction method. Specifically, the D50 is the particle size value corresponding to when the cumulative volume distribution percentage of the material reaches 50%.

[0067] In the embodiment of the present application, the specific surface area of ​​the sodium positive electrode material is 0.15-0.35m 2 / g. In the present application, the sodium-based metal oxide is subjected to at least the above-mentioned specific M 1 、M 2The doping of elements can make the material have a high sphericity while its particle size is appropriately increased, so that its specific surface area can be moderately reduced, which is beneficial to improve the battery cycle performance using the sodium positive electrode material. In addition, the specific surface area of ​​the sodium positive electrode material is 0.15m 2 / g or more, which also reflects that the particle size of the material is relatively large, which is conducive to improving the compaction density. For example, the specific surface area of ​​the sodium cathode material can be 0.18m 2 / g, 0.20m 2 / g, 0.22m 2 / g, 0.24m 2 / g, 0.25m 2 / g, 0.26m 2 / g, 0.28m 2 / g, 0.30m 2 / g, 0.32m 2 / g, 0.34m 2 In some embodiments, the specific surface area of ​​the sodium cathode material is 0.20-0.30 m 2 / g.

[0068] The specific surface area of ​​the sodium cathode material can be measured by the nitrogen adsorption method (also known as the "BET method").

[0069] In the embodiment of the present application, the compaction density of the sodium positive electrode material at 200 MPa is 3.2 g / mL (ie, 3.2 g / cm 3 ) or above, for example, in the range of 3.2-3.6 g / mL. Based on the embodiments of the present application, the aforementioned sodium-based metal oxide is doped with specific elements, which can improve its sphericity and increase its particle size, so that the compaction density of the material is higher, which is beneficial to the improvement of the volume energy density of the battery. For example, the compaction density of the sodium positive electrode material at 200 MPa can be specifically 3.15 g / mL, 3.2 g / mL, 3.3 g / mL, 3.4 g / mL, 3.5 g / mL, etc.

[0070] The compaction density can be measured by a powder compaction density meter on the powdered sodium cathode material and read as the compaction density under a pressure of 200 MPa.

[0071] In the embodiment of the present application, the 0.1C charge gram capacity of the sodium battery positive electrode material is 140-160 mAh / g, for example, specifically 142 mAh / g, 143 mAh / g, 145 mAh / g, 148 mAh / g, 150 mAh / g, 152 mAh / g, 155 mAh / g, 158 mAh / g, etc. In some embodiments, the above-mentioned charge gram capacity of the sodium battery positive electrode material is 145-160 mAh / g. The positive electrode material has a higher discharge gram capacity, which is beneficial to the improvement of the total charge capacity / discharge capacity of the sodium battery.

[0072] In some embodiments of the present application, the sodium positive electrode material further includes a metal oxide coating layer coated on the surface of the sodium-based metal oxide; the metal element in the metal oxide coating layer is selected from the M contained in the sodium-based metal oxide. 1 、M 2 、M 3 It is understood that when the sodium-based metal oxide contains the doping element M 1 、M 2 When the metal element in the metal oxide coating layer is selected from M contained in the sodium-based metal oxide 1 、M 2 When the sodium-based metal oxide contains doping elements M 1 、M 2 and M 3 When the metal element in the metal oxide coating layer is selected from M contained in the sodium-based metal oxide 1 、M 2 、M 3 One or more elements.

[0073] The metal oxide coating layer may be formed during the preparation of the sodium-based metal oxide based on the segregation of the doping elements contained therein. In an embodiment of the present application, the thickness of the metal oxide coating layer may be 0.1 nm to 20 nm, for example, specifically 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 18 nm, etc. In some embodiments, the thickness of the coating layer may be 1 nm to 10 nm.

[0074] It should be noted that when the above-mentioned sodium-based cathode material does not have a metal oxide coating layer, the average particle sphericity, D50, specific surface area, compacted density, and discharge gram capacity of the above-mentioned sodium-based cathode material specifically refer to the corresponding properties of the sodium-based metal oxide. In other words, the above-mentioned parameters are applicable whether the above-mentioned sodium-based cathode material has or does not have a metal oxide coating layer.

[0075] The present application also provides a method for preparing the above-mentioned sodium cathode material. The preparation method may specifically include the following steps:

[0076] The first precursor of the sodium-based metal oxide is mixed with a sodium source and a doping element M source, and then calcined to obtain a sodium-based metal oxide-containing sodium cathode material;

[0077] Wherein, the first precursor contains Ni, Fe and Mn elements, and the M includes the above-mentioned M 1 and the above M 2 Elements, or including the above M 1 、M 2 and M 3 Here, M is all doping elements contained in the above sodium-based metal oxide.

[0078] In the present application, the first precursor does not contain sodium and doping element M. The first precursor can be one or more of carbonates, hydroxides, oxyhydroxides, and oxides containing Ni, Fe, and Mn elements. a Ni1-xyij-kFe x Mn y M 1 i M 2 j M 3 k O b The first precursor, the sodium source, and the M source are mixed in a stoichiometric ratio. The mixing can be performed in a ball mill, a grinder, a stirring device, or the like.

[0079] In an embodiment of the present application, the sodium source may be at least one compound containing sodium element, for example, the sodium source may be one or more of sodium carbonate, sodium bicarbonate, sodium nitrate, sodium hydroxide, and the like.

[0080] In the embodiment of the present application, the M source includes M 1 Source and M 2 Source, or including M 1 Source, M 2 Source and M 3 Source. Among them, M 1 The source can be M 1 At least one compound of an element, such as M 1 The source can be M 1 One or more of carbonates, bicarbonates, nitrates, oxides, peroxides, hydroxides, etc. 2 The source can be M 2At least one compound of an element, such as M 2 The source can be M 2 One or more of carbonates, bicarbonates, nitrates, oxides, peroxides, hydroxides, etc.

[0081] In an embodiment of the present application, the calcination atmosphere is an oxygen-containing atmosphere (for example, an air atmosphere or an oxygen atmosphere) so that precursors in the form of hydroxides, carbonates, or oxyhydroxides decompose into corresponding oxides. In some embodiments of the present application, the calcination may be a one-step calcination. For example, the one-step calcination may be kept warm for 6-24 hours at a calcination temperature of 850°C-1100°C. The calcination temperature may be specifically 860°C, 880°C, 900°C, 920°C, 950°C, 980°C, 990°C, 1000°C, or 1050°C. The holding time may be specifically 7 hours, 8 hours, 9 hours, 10 hours, 12 hours, 15 hours, 16 hours, 18 hours, 20 hours, etc. In other embodiments of the present application, the calcination may be a two-step or more step-by-step calcination. After the calcined product is cooled to room temperature, it can be crushed and sieved to obtain a positive electrode material of the desired particle size.

[0082] In addition, in some embodiments of the present application, a pre-calcination may be performed before the calcination to remove water from the first precursor, sodium source, and M source, and to decompose the non-oxide raw materials into oxides. It is understood that the pre-calcination temperature is lower than the calcination temperature.

[0083] The present application also provides another method for preparing the above-mentioned sodium battery cathode material, which may include the following steps:

[0084] The second precursor of the sodium-based metal oxide is mixed with a sodium source and a doping element M "source and then calcined to obtain a sodium positive electrode material containing the sodium-based metal oxide; wherein the third precursor contains Ni, Fe, Mn and M' elements, and the M' and the M" together constitute all the doping elements M contained in the sodium-based metal oxide, and M includes the above M 1 and M 2 , or including the above M 1 、M 2 and M 3 .

[0085] It is understood that M' and M" are part of all M contained in the sodium-based metal oxide. If M includes M 1 and M 2 , then M' is M 1 , M" is M 2 , or M' is M 2 , M”=M 1 If M includes M1 、M 2 and M 3 , then M' is one or two of M, and M" is the remaining doping element. For example, if M' is M 1 , then the M" source includes M 2 Source and M 3 Source; if M' is M 2 , then the M" source includes M 1 Source and M 3 Source; if M' is M 3 , then the M” source includes M 1 Source and M 2 Source; if M' is M 1 and M 2 , then the source of M” is M 3 Source; if M' is M 1 and M 3 , then the source of M” is M 2 Source; if M' is M 2 and M 3 , then the source of M” is M 1 Source; if M' is M 2 and M 3 , then the source of M” is M 1 source.

[0086] Similarly, the second precursor can be one or more carbonates, hydroxides, oxyhydroxides, or oxides containing Ni, Fe, Mn, and M'. For example, the M' source can be one or more carbonates, bicarbonates, nitrates, oxides, peroxides, hydroxides, etc. containing M'. The selection range, mixing method, and calcination process of the sodium source can be found in the description above.

[0087] The present application also provides another method for preparing the above-mentioned sodium cathode material, which may include the following steps:

[0088] The third precursor of the sodium-based metal oxide is mixed with a sodium source and then calcined to obtain a sodium-based positive electrode material containing the sodium-based metal oxide; wherein the third precursor contains Ni, Fe, Mn and all doping elements M contained in the sodium-based metal oxide, and the M includes the above-mentioned M 1 and the above M 2 Elements, or including the above M 1 、M 2 and M 3 element.

[0089] The above-mentioned third precursor is used to be mixed with a sodium source and then calcined to form a positive electrode material containing the above-mentioned sodium-based metal oxide. It can be understood that the third precursor does not contain sodium element. In the embodiment of the present application, the third precursor can be one or more of carbonates, hydroxides, oxyhydroxyl and oxides containing Ni, Fe, Mn and doping element M. In the third precursor, the molar ratio relationship between the metal elements Ni, Fe, Mn and M can be basically consistent with the above-mentioned sodium-based metal oxide. In some embodiments, the third precursor is a hydroxide, and its chemical formula can be expressed as Ni1-xyij-kFe x Mn y M 1 i M 2 j M 3 k (OH)2. In other embodiments, the third precursor is a hydroxide oxide, an exemplary chemical formula of which can be represented by Ni1-xyij-kFe x Mn y M 1 i M 2 j M 3 k In some other embodiments, the sodium-based metal oxide precursor is a carbonate, and its chemical formula can be expressed as Ni1-xyij-kFe x Mn y M 1 i M 2 j M 3 k CO3.

[0090] Among them, the selection range, mixing method, calcination process, etc. of the sodium source can be found in the previous description of this application.

[0091] The preparation methods of the three sodium-based positive electrode materials provided above in this application are as follows: a sodium-free precursor corresponding to the sodium-based metal oxide that does not contain the doping element M or contains part of M is mixed with a sodium source and a doping element source and then calcined, or a sodium-free precursor containing all the doping elements M is mixed with a sodium source and then calcined, to obtain a sodium-based metal oxide containing the doping element M. This preparation method has a simple process, does not require complicated steps in the doping process, is suitable for large-scale production, and can produce sodium-based positive electrode materials that meet the requirements of sphericity, particle size, and compacted density as mentioned above in this application.

[0092] During the calcination process, a metal oxide coating layer may be formed on the sodium-based metal oxide. The metal element in the metal oxide coating layer is selected from one or more of all M elements contained in the sodium-based metal oxide. Of course, in other embodiments of the present application, an additional coating layer may be formed on the surface of the prepared sodium-based metal oxide, that is, the coating layer formation operation is performed after the calcination step.

[0093] The embodiment of the present application also provides a positive electrode plate for a sodium battery, which includes the sodium battery positive electrode material described above in the embodiment of the present application.

[0094] Referring to Figure 1, the positive electrode sheet 100 provided in an embodiment of the present application includes a positive electrode current collector 11 and a positive electrode material layer 12 disposed on the positive electrode current collector 11. The positive electrode material layer 12 includes a positive electrode active material 120. The positive electrode active material 120 includes the sodium battery positive electrode material described above in the embodiment of the present application. The positive electrode material layer 12 is disposed on one surface or on two opposite surfaces of the positive electrode current collector 11. In the embodiment of the present application, the positive electrode material layer 12 may further include a binder, a conductive agent, etc.

[0095] Among them, the positive electrode current collector 11, the binder, and the conductive agent are conventional choices in the field of sodium batteries. For example, the positive electrode current collector 11 can be aluminum foil, carbon-coated aluminum foil, aluminized polymer film, etc. The binder can specifically include but is not limited to polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyimide (PI), polyacrylic acid (PAA), polyacrylate, polyacrylamide (PAM), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR) and sodium alginate, etc. One or more of the conductive agent can specifically include but is not limited to acetylene black, Ketjen black, Super P conductive carbon black, graphite, graphene, carbon nanotubes, carbon fiber, amorphous carbon, etc.

[0096] In some embodiments, the positive electrode active material 120 in the positive electrode material layer 12 may all be the above-mentioned sodium-based positive electrode materials in the embodiment of the present application. In other embodiments, the positive electrode active material 120 in the positive electrode material layer 12 includes the above-mentioned sodium-based positive electrode materials in the embodiment of the present application, and other positive electrode active materials. Exemplarily, the other positive electrode active materials may be at least one of other layered sodium transition metal oxides, Prussian blue (white) compounds, and sodium polyanionic compounds. For example, the layered sodium transition metal oxide may be sodium nickel iron manganese (NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3O2, abbreviated as NFM); the Prussian blue (white) compound can be Prussian white (Na2Mn[Fe(CN)6], abbreviated as PBA); the sodium polyanion compound can be sodium iron phosphate (NaFePO4, abbreviated as NFP) or sodium vanadium phosphate (Na3V2(PO4)3, abbreviated as NVP).

[0097] Referring to FIG2 , an embodiment of the present application further provides a sodium ion battery 200. The sodium ion battery 200 includes a positive electrode 21, a negative electrode 22, an electrolyte 23, a diaphragm 24, and corresponding connecting accessories and circuits. The diaphragm 24 is disposed between the positive electrode 21 and the negative electrode 22, and the electrolyte 23 is filled between the positive electrode 21 and the negative electrode 22 and infiltrates the diaphragm 24. The positive electrode 21 includes the positive electrode sheet 100 described above in the embodiment of the present application, which also correspondingly includes the sodium positive electrode material described above in the embodiment of the present application.

[0098] For sodium ion batteries, it is through sodium ions (Na + ) between the positive electrode 21 and the negative electrode 22 to achieve energy storage and release. The electrolyte 23 is Na + The carrier transported between the positive electrode 21 and the negative electrode 22. The ion-conducting but electronically insulating separator 24 is used to separate the positive electrode 21 from the negative electrode 22 to prevent short circuit. + It is released from the positive electrode active material of the positive electrode 21, migrates to the negative electrode 22 through the electrolyte 23 and the separator 24, and is embedded in the negative electrode active material to achieve the storage of electrical energy. + The negative electrode active material in the negative electrode 22 is released and migrates back to the positive electrode 21 through the electrolyte 23 and the separator 24 to perform external work, that is, release electrical energy to the power load connected to the sodium ion battery 200.

[0099] In the embodiment of the present application, the sodium ion battery 200 has a high volume energy density, a high capacity and good cycle performance because its positive electrode 21 uses the above-mentioned sodium positive electrode material provided in the embodiment of the present application.

[0100] The sodium ion battery 200 shown in FIG2 is a liquid battery, which uses an electrolyte as a liquid electrolyte. It is understood that in other embodiments of the present application, the sodium ion battery can also be a solid / semi-solid battery, which includes a positive electrode, a negative electrode, and a solid / semi-solid electrolyte layer located therebetween.

[0101] The sodium-ion batteries provided in the embodiments of this application can be used as batteries for consumer electronic devices, power batteries for mobile devices, and can also be applied to energy storage systems. Consumer electronic devices include, but are not limited to, mobile phones, tablet computers, laptop computers, and wearable electronic devices. Mobile devices can include, for example, electric vehicles and electric bicycles.

[0102] The embodiment of the present application further provides an electric device, which includes the above-mentioned sodium ion battery of the embodiment of the present application. The electric device uses the above-mentioned sodium ion battery to power it. Among them, the electric device may include electronic equipment, or mobile devices (such as electric vehicles). Among them, the electric device includes an electric component and a power supply component, the power supply component supplies power to the electric component, and the power supply component includes the above-mentioned sodium ion battery of the embodiment of the present application.

[0103] In the implementation manner of this application, the electronic device can be a mobile phone, a tablet computer, a laptop computer, a wearable device (such as a smart watch, a smart bracelet, smart glasses, smart headphones, etc.), an augmented reality (AR) device, a virtual reality (VR) device, a television, a digital camera, a vehicle-mounted device and other electronic products, and this application does not limit this.

[0104] In some embodiments, referring to FIG3 , an embodiment of the present application provides an electronic device 300. The electronic device 300 includes a housing 301 and a circuit board assembly (not shown in FIG3 ) and a battery 302 housed in the housing 301. The battery 302 can power the electronic device 300, and the battery 302 includes the sodium ion battery 200 described above in the embodiment of the present application. The battery 302 is electrically connected to the circuit board and can power the circuit board assembly. The circuit board assembly can be one of the electrical components of the electronic device 300. In some embodiments, the housing 301 may include a front cover assembled on the front side of the electronic device and a rear shell assembled on the rear side, and the battery 302 may be fixed on the inside of the rear shell. The electronic device 300 shown in FIG3 may specifically be a mobile phone, etc.

[0105] In some other embodiments, referring to FIG. 4 , an embodiment of the present application provides a mobile device 400. Mobile device 400 can be any movable device used for loading, transporting, assembling, disassembling, security, etc., such as various types of vehicles, including but not limited to electric vehicles, electric buses, electric trucks, electric motorcycles, electric bicycles, etc. In this embodiment, mobile device 400 is specifically an electric vehicle.

[0106] Specifically, the mobile device 400 may include a body 401, a mobile component 402 (for example, a wheel), and a drive component. The drive component includes a motor 403 and a battery system 404. The battery system 404 includes the above-mentioned sodium ion battery 200 provided in the embodiment of the present application. The battery system 404 is housed in the body 401 (for example, under the chassis of the vehicle) and is electrically connected to the motor 403. It can supply power to the motor 403, and the motor 403 then provides power to drive the mobile component 402 to move. The motor 403 is one of the electrical components of the mobile device 400. The battery system 404 may be a battery pack, which includes a plurality of the above-mentioned sodium ion batteries 200. The plurality of sodium ion batteries may be connected in series and parallel to form a battery pack, and at least one battery module and a battery management system may be packaged to form a battery pack.

[0107] The present invention also provides an energy storage system comprising a plurality of the sodium ion batteries 200 described above. Due to the use of the secondary batteries provided in the present invention, the energy storage system can have a strong energy storage capacity and good energy efficiency, and is cost-effective.

[0108] Referring to Figure 5, the energy storage system 500 includes one or more battery packs 501 (Figure 5 is an example of two battery packs 501), and a battery management system 502 electrically connected to each battery pack 501, wherein each battery pack 501 includes multiple sodium ion batteries 200 provided in the embodiments of the present application. The battery pack 501 can be a module composed of multiple sodium ion batteries 200 connected in series and parallel. The battery management system 502 can be used to monitor the status information of each sodium ion battery 200 in the battery pack 501, adjust the voltage and temperature of the battery pack, and implement charge and discharge protection functions. In some embodiments, the battery pack 501 and the battery management system 502 can be packaged to form a battery pack.

[0109] In some embodiments of the present application, the energy storage system 500 further includes a power converter and at least one battery pack, wherein the power converter is electrically connected to the battery pack. The power converter is configured to convert the voltage output by the battery pack into power and output it to the grid or an electrical load, and / or to convert the voltage output by an external power source into power and output it to the battery pack.

[0110] The energy storage system 500 shown in FIG5 may be an electric vehicle energy storage system, a data center short-term backup power system, a site energy backup power system, an intelligent photovoltaic energy storage power station, or the like.

[0111] The embodiments of the present application are further described below with reference to a number of embodiments.

[0112] Comparative Example 1

[0113] Weigh sodium carbonate and Ni according to the stoichiometric ratio of Na: (Ni+Fe+Mn) = 1:1.1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)2, mixed in a ball mill, controlling the ball mill speed to 300rpm, to obtain a mixture. The mixture was calcined in air or oxygen, wherein the calcination procedure was: calcined at 950℃ for 8 hours, and then naturally cooled to room temperature to obtain the desired positive electrode material NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2.

[0114] Examples 1-8

[0115] According to the stoichiometric ratio of each element in the positive electrode material shown in Table 1, Na: (Ni+Fe+Mn): M 1 :M 2 :M 3 =1:(1-ijk):i:j:k to weigh sodium carbonate, Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)2 and M 1 Oxide, M 2 Oxide, M 3 Oxide (if k = 0, M is not taken 3 The mixture was then calcined in air or oxygen at 950°C for 8 hours, followed by natural cooling to room temperature to obtain the desired positive electrode material. The types of metal elements in the positive electrode material and their subscripts are shown in Table 1.

[0116] Example 9

[0117] According to the stoichiometric ratio of each element in the positive electrode material shown in Table 1, Na: (Ni+Fe+Mn): M 1 :M 2 =1:(1-ij):i:j to weigh sodium carbonate, Ni 0.95 / 3 Fe 0.95 / 3 Mn 0.95 / 3 Cu 0.05 (OH)2 and M 2 Oxide (M 2 and Ce) and mixed in a ball mill at a speed of 300 rpm to obtain a mixture. The mixture was calcined in air or oxygen at 950°C for 8 hours and then naturally cooled to room temperature to obtain the desired positive electrode material.

[0118] Example 10

[0119] According to the stoichiometric ratio of each element in the positive electrode material shown in Table 1, Na: (Ni+Fe+Mn): M 1 :M 2 =1:(1-ij):i:j to weigh sodium carbonate, Ni 0.95 / 3 Fe 0.95 / 3 Mn 0.95 / 3 Co 0.05 (OH)2 and M 2 Oxide (M 2 and Ce) and mixed in a ball mill at a speed of 300 rpm to obtain a mixture. The mixture was calcined in air or oxygen at 950°C for 8 hours and then naturally cooled to room temperature to obtain the desired positive electrode material.

[0120] Material characterization:

[0121] Figure 6 shows a cross-sectional scanning electron microscope (SEM) photograph of the positive electrode material prepared in Example 1 and its energy spectrum analysis results. As can be seen from Figure 6, the doping elements Cu and Ce are uniformly distributed in the positive electrode material, just like the elements Na, Mn, Fe, and Ni. This also shows that Cu and Ce are uniformly doped in the crystal lattice of the positive electrode material.

[0122] Figure 7 shows an SEM photograph of the positive electrode material prepared in Example 2. As can be seen from Figure 7, the positive electrode material in Example 2 exhibits a rounded, highly spherical structure rather than a distinctly flat, flaky structure. Furthermore, the particles of this positive electrode material are relatively large, approximately 14 μm in size. Figure 8 shows an SEM photograph of the positive electrode material prepared in Example 3 at a higher magnification. Figure 8 also shows that the positive electrode material in Example 3 is composed of spherical particles with a high degree of sphericity.

[0123] In addition, from the SEM photographs of the positive electrode materials containing more particles in each embodiment and comparative example, more than 50 positive electrode material particles were taken to calculate the sphericity of each particle (the ratio of the area equivalent radius to its circumference equivalent radius), and then the average particle sphericity of the positive electrode material was calculated. The relevant results are summarized in Table 1 below.

[0124] The positive electrode materials prepared in each example and comparative example were subjected to particle size distribution analysis using a laser particle size analyzer. The particle size distribution curve obtained was used to determine the particle size corresponding to the cumulative volume distribution percentage of the material reaching 50% (i.e., D50). The results are summarized in Table 1 below.

[0125] In addition, the specific surface area of ​​the cathode material powders prepared in each Example and Comparative Example was measured using the nitrogen adsorption method (also known as the "BET method"). The compaction density of the cathode material powders prepared in each Example and Comparative Example was measured using a powder compaction density meter, and the compaction density value of each powder material at a pressure of 200 MPa was recorded. The relevant results are summarized in Table 2.

[0126] The positive electrode materials prepared in each embodiment and comparative example were also assembled into button-type sodium batteries, and the specific steps were as follows: (1) the sodium positive electrode materials of each embodiment or comparative example were added to N-methylpyrrolidone (NMP) with a binder polyvinylidene fluoride (PVDF) and a conductive agent super P in a mass ratio of 94:3:3, and the mixture was thoroughly stirred and mixed to obtain a slurry, which was coated on an aluminum foil current collector, dried, cold pressed, and cut to obtain positive electrode sheets; (2) the obtained positive electrode sheets were respectively combined with a sodium sheet, an electrolyte (the electrolyte contained NaClO4 with a concentration of 1 mol / L) and a separator to produce a 2032 button-type battery.

[0127] Each button-type sodium battery was subjected to charge and discharge tests over a voltage range of 2.0-4.0V, with an initial charge and discharge rate of 0.1C. The charge capacity, median voltage, and calculated volumetric energy density of each button-type sodium battery during the initial charge and discharge process were recorded. Volumetric energy density = positive electrode material compaction density × initial charge capacity × median voltage. The test results are summarized in Table 2.

[0128] Table 1 Note: In Table 1, the subscript of Na element in each cathode material is 1, and the subscript of O element is 2.

[0129] Table 2

[0130] From Table 1 and Table 2, it can be seen from the comparison between Comparative Example 1 and Examples 1-10 that the sodium oxide positive electrode material containing Ni, Fe, and Mn elements is subjected to M 1 Elements, M 2 The co-doping of elements can significantly improve the sphericity and average particle size of the material's particles and reduce its specific area, thereby significantly improving the volume energy density and cycle performance of the battery. At the same time, the specific capacity of the positive electrode material has not decreased significantly, and has even increased.

[0131] Among them, it can be seen from the comparison between Examples 1 and 2 that the positive electrode material maintains the doping element M 2 Under the condition of no change, as M 1 As the doping amount of the element increases, the average particle sphericity of the positive electrode material increases; from the comparison between Examples 2 and 3, it can be seen that under the same other conditions, the doping element M 1 The effect of using Cu is better than that of using Co.

[0132] In addition, from the comparison between Examples 2 and 4, it can be seen that, under the same conditions, M 1When the Ce doping ratio is the same as Sr, the sphericity of the material is higher and the particle size is slightly smaller, but the compaction density of the positive electrode sheet and the volume energy density of the battery are high, and the specific capacity of the material is high. In addition, M 2 Example 5, which contains both Ce and Sr, is also better than M 2 The battery of Example 4, which is composed solely of Sr, has a good overall effect.

[0133] From the comparison between Example 6 and Example 2, it can be seen that 1 When the doping amount of M is the same, 2 With the increase of the doping amount of elements, the particle size of the material becomes larger and the average particle sphericity increases.

[0134] From the comparison between Examples 6-8, it can be seen that when doping M 1 and M 2 In the case of elements, we further introduce M 3 Doping with elements can further improve the electrochemical performance of cathode materials, such as improving capacity and cycle stability. 3 When it is Zn element, the cycle performance of the positive electrode material is better; 3 When it is Ca element, the specific capacity of the positive electrode material is higher.

[0135] In addition, it can be seen from the comparison between Example 9 and Example 2, and the comparison between Example 10 and Example 3 that M 1 、M 2 Elements can be doped by solid phase doping or pre-doped in the precursor and then calcined to obtain M-doped 1 、M 2 layered sodium oxide cathode materials.

[0136] The foregoing merely represents exemplary embodiments of the present application, and while the description is relatively specific and detailed, it should not be construed as limiting the scope of the present invention. It should be noted that a person of ordinary skill in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

[0137] In the description of this application, unless otherwise specified, the meaning of "multiple (kinds)" refers to greater than or equal to two (kinds). "At least one (kind)" refers to one (kind) or more (kinds). "At least one of the following (kinds)" or similar expressions refers to any combination of these items, including any combination of single (individual) or plural (individual) items. For example, "at least one (individual) of a, b, or c", or "at least one (individual) of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple, respectively.

[0138] In addition, the numerical range represented by "-" in this application refers to the range including the numerical values ​​recorded before and after "-" as the minimum and maximum values, respectively. In this application, expressions about parameter ranges, such as "greater than or equal to (≥)", "less than or equal to (≤)", "above...", and "below..." all include the number itself. The numerical values ​​and numerical ranges involved in the embodiments of this application are approximate values. Due to the influence of manufacturing process / testing method, etc., there may be a certain range of errors, which can be considered negligible by those skilled in the art.

Claims

1. A sodium cathode material, characterized in that The sodium-based positive electrode material includes a sodium-based metal oxide, the chemical formula of which is Na a Ni1-xyij-kFe x Mn y M 1 i M 2 j M 3 k O b , wherein, 0.5≤a≤1.2, 1.8≤b≤2.2, 0<x<1, 0<y<1, 0<i≤0.1, 0<j≤0.1, 0≤k≤0.1, and 0<i+j+k≤0.1, and the values ​​of a, b, x, y, i, j, and k make the sodium-based metal oxide electrically neutral; M 1 、M 2 、M 3 represents the doping element, the M 1 At least one selected from Cu and Co, the M 2 At least one selected from Ce and Sr, the M 3 is different from the M 1 、The M 2 of metal elements.

2. The sodium cathode material according to claim 1, wherein The M 3 One or more selected from Ti, Zr, Zn, Mg, Ca, V, Cr, Mo, Nb, Y, Sn, Sb, Al, Li, and K.

3. The sodium cathode material according to claim 1 or 2, wherein The M 2 is Ce, or is Ce and Sr.

4. The sodium cathode material according to any one of claims 1 to 3, wherein 0<i+j+k≤0.

08.

5. The sodium cathode material according to any one of claims 1 to 4, characterized in that 0.01≤i≤0.06。 6. The sodium cathode material according to any one of claims 1 to 5, characterized in that 0.01≤j≤0.05。 7. The sodium cathode material according to any one of claims 1 to 6, characterized in that The i is greater than or equal to the j.

8. The sodium cathode material according to any one of claims 1 to 7, wherein 0≤k≤0.03。 9. The sodium battery cathode material according to any one of claims 1 to 8, characterized in that The sodium cathode material is in the form of spherical or quasi-spherical particles.

10. The sodium cathode material according to any one of claims 1 to 9, characterized in that The average particle sphericity of the sodium-ion cathode material is in the range of 0.75-1.

11. The sodium cathode material according to claim 10, wherein In the sodium battery positive electrode material, the number of particles with a sphericity of less than 0.75 accounts for less than 30%.

12. The sodium cathode material according to claim 11, wherein The aspect ratio of the particles having a sphericity of less than 0.75 is within a range of greater than 1 and less than 3.

13. The sodium battery cathode material according to any one of claims 1 to 12, wherein: The particle size D50 of the sodium cathode material is 5 μm-20 μm.

14. The sodium battery cathode material according to any one of claims 1 to 13, wherein The specific surface area of ​​the sodium cathode material is 0.15 m 2 / g-0.35m 2 / g.

15. The sodium battery cathode material according to any one of claims 1 to 14, characterized in that The sodium positive electrode material further includes a metal oxide coating layer coated on the surface of the sodium-based metal oxide; the metal element in the metal oxide coating layer is selected from the M contained in the sodium-based metal oxide. 1 、The M 2 、The M 3 One or more of .

16. The sodium battery cathode material according to any one of claims 1 to 15, characterized in that The compaction density of the sodium cathode material at 200 MPa is 3.2 g / mL-3.6 g / mL.

17. The positive electrode material according to any one of claims 1 to 16, characterized in that The gram capacity of the sodium cathode material is 140 mAh / g-160 mAh / g.

18. A method for preparing a sodium cathode material according to any one of claims 1 to 17, characterized in that: The following steps are involved: Alternatively, the first precursor of the sodium-based metal oxide is mixed with a sodium source and a doping element M source and then calcined to obtain a sodium cathode material; Alternatively, the second precursor of the sodium-based metal oxide is mixed with a sodium source and a doping element M' source and then calcined to obtain a sodium cathode material; Mixing the third precursor of the sodium-based metal oxide with a sodium source and calcining the mixture to obtain a sodium cathode material; The first precursor contains Ni, Fe and Mn elements; the second precursor contains Ni, Fe, Mn and M' elements, and the M' and M' together constitute all the doping elements M contained in the sodium-based metal oxide; the M includes the M 1 and M 2 , or including the M 1 、M 2 and M 3 ; The third precursor contains Ni, Fe, Mn and the doping element M.

19. The preparation method according to claim 18, characterized in that The first precursor, the second precursor, and the third precursor are independently selected from one or more of carbonates, hydroxides, oxyhydroxides, and oxides.

20. A positive electrode plate, characterized in that: The positive electrode sheet includes a positive electrode current collector and a positive electrode material layer arranged on the positive electrode current collector, and the positive electrode material layer includes the sodium-based positive electrode material according to any one of claims 1 to 17, or the sodium-based positive electrode material prepared by the preparation method according to any one of claims 18 to 19.

21. A sodium ion battery, characterized in that: The sodium ion battery comprises the positive electrode sheet and the negative electrode sheet as claimed in claim 20, and an electrolyte located between the positive electrode sheet and the negative electrode sheet.

22. An electrical device, characterized in that: The electrical device includes the sodium ion battery as claimed in claim 21.

23. The electrical equipment according to claim 22, wherein: The power-consuming device includes an electronic device or a mobile device.

24. An energy storage system, characterized in that: The energy storage system includes at least one battery pack, which includes a plurality of sodium-ion batteries as claimed in claim 21.

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