Positive electrode sheet for sodium-ion battery, and battery, battery pack, and electric device

Abstract

The present application provides a positive electrode sheet for a sodium-ion battery, and a battery, a battery pack, and an electric device. The positive electrode sheet for a sodium-ion battery comprises a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode current collector; a positive electrode coating layer comprises a polyanionic positive electrode material; the cross-sectional porosity of the polyanionic positive electrode material is 1%-60%; the specific surface area of the polyanionic positive electrode material is denoted as S m2 / g, wherein 1.5≤S≤30; and the volumetric particle size distribution (D90-D10) / D50 of the polyanionic positive electrode material is denoted as K, wherein 0.6≤K≤4, and 5≤S*K≤60. By using the polyanionic positive electrode material satisfying the described properties, the stability of a positive electrode slurry formed by the positive electrode material can be improved, the viscosity of the positive electrode slurry can be reduced, the gelation of the positive electrode slurry can be reduced, the coating uniformity of the positive electrode slurry on the current collector can be improved, and the uniformity of the positive electrode active material layer can be improved, thereby increasing the compacted density of the positive electrode sheet, and further increasing the volumetric energy density and gram capacity of the battery.

Description

Positive electrode sheets, batteries, battery packs, and electrical devices used in sodium-ion batteries.

[0001] This application claims priority to Chinese Patent Application No. 202510121678.3, filed on January 24, 2025, entitled "Positive electrode sheet, battery, battery pack and electrical device for sodium-ion batteries", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application belongs to the field of batteries, and particularly relates to a positive electrode sheet, battery, battery pack and electrical device for sodium-ion batteries. Background Technology

[0003] Lithium-ion batteries are a widely used battery technology in electronic devices and electric vehicles. Compared to lithium, sodium is more abundant and cheaper, thus sodium-ion batteries have broad application prospects. Existing sodium-ion battery cathode materials mainly include layered metal oxides, polyanionic compounds, and Prussian blue-like compounds.

[0004] Polyanionic cathode materials have attracted widespread attention due to their high rate performance, long cycle life, good thermal stability, and excellent safety performance, as well as their stable crystal structure, high voltage, and high safety.

[0005] However, the positive electrode slurry formed by polyanionic positive electrode material has poor stability and is prone to gelation, making it difficult to coat. This affects the coating effect of the positive electrode slurry on the current collector, thereby affecting the uniformity of the positive electrode active material layer and resulting in a low compaction density of the positive electrode sheet. Summary of the Invention

[0006] This application provides a positive electrode sheet, a battery, a battery pack, and an electrical device for sodium-ion batteries, which improves the stability of the positive electrode slurry, thereby increasing the compaction density of the positive electrode sheet.

[0007] In a first aspect, this application provides a positive electrode sheet for a sodium-ion battery, comprising a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode current collector, wherein the positive electrode active material layer contains a polyanionic positive electrode material.

[0008] The cross-sectional porosity of the polyanionic cathode material is 1%-60%;

[0009] The specific surface area of ​​the polyanion-type cathode material is denoted as Sm. 2 / g, 1.5≤S≤30;

[0010] The volumetric particle size distribution (D90-D10) / D50 of the polyanionic cathode material is denoted as K, where 0.6≤K≤4;

[0011] The polyanionic cathode material satisfies the following relationship: 5≤S*K≤60.

[0012] In one possible implementation, 0.8 ≤ K ≤ 3.

[0013] In one possible implementation, 0.8 ≤ K ≤ 2.

[0014] In one possible implementation, 6 ≤ S*K ≤ 45.

[0015] In one possible implementation, 10 ≤ S*K ≤ 20.

[0016] In one possible implementation, 2≤S≤20.

[0017] In one possible implementation, 3 ≤ S ≤ 15.

[0018] In one possible implementation, the cross-sectional porosity of the polyanionic cathode material is 2%-40%.

[0019] In one possible implementation, the cross-sectional porosity of the polyanionic cathode material is 5%-20%.

[0020] In one possible implementation, 0.5μm≤D10≤10μm, 3μm≤D50≤15μm, and 10μm≤D90≤60μm.

[0021] In one possible implementation, the chemical formula of the polyanionic cathode material is Na. x M y (PO4) w X a Z b Y c M is at least one of Ti, V, Cr, Mn, Fe, Co, and Ni; X is at least one of S, P, Si, W, and B; Z is at least one of F, O, and OH; and Y is at least one of C and Al.

[0022] 2.8≤x≤4.2, 1.9≤y≤3.1, 1.8≤w≤2.2, 0≤a≤3.0, 0≤b≤8.0, 0≤c≤3.0.

[0023] In one possible implementation, the polyanionic cathode material is at least one of single crystal, quasi-single crystal, and polycrystalline.

[0024] Secondly, this application provides a battery including the positive electrode sheet described in the first aspect.

[0025] Thirdly, this application provides a battery pack including the battery described in the second aspect.

[0026] Fourthly, this application provides an electrical device including the battery described in the second aspect or the battery pack described in the third aspect.

[0027] The positive electrode sheet, battery, battery pack, and electrical device for sodium-ion batteries provided in this application include a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode current collector. The positive electrode coating contains a polyanionic positive electrode material, the cross-sectional porosity of which is 1%-60%, and the specific surface area of ​​which is denoted as Sm. 2 / For g, 1.5≤S≤30, the volumetric particle size distribution (D90-D10) / D50 of the polyanionic cathode material is denoted as K, 0.6≤K≤4, and 5≤S*K≤60. By using a polyanionic cathode material that meets the above characteristics, the compaction degree of the cathode material can be improved, the stability of the cathode slurry formed by the cathode material can be improved, the viscosity of the cathode slurry can be reduced, the gelation of the cathode slurry can be reduced, the coating uniformity of the cathode slurry on the current collector can be improved, and the uniformity of the cathode active material layer can be improved, thereby increasing the compaction density of the cathode sheet, and thus improving the volumetric energy density and specific capacity of the battery. Detailed Implementation

[0028] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0029] The cathode materials of sodium-ion batteries mainly include layered metal oxides, polyanionic compounds, and Prussian blue compounds.

[0030] Layered metal oxides exhibit complex phase transitions, poor air and structural stability, stringent environmental requirements, and inherently poor material safety. Prussian blue compounds typically contain numerous vacancies and abundant water of crystallization, impacting the battery's actual specific capacity, stability, and safety. Polyanionic compounds, on the other hand, possess characteristics such as high rate performance, long cycle life, good thermal stability, and excellent safety performance. Furthermore, they exhibit stable crystal structures, high voltage, and high safety, thus attracting widespread attention.

[0031] However, the positive electrode slurry formed by polyanionic compounds has poor stability and is prone to gelation, making it difficult to coat. This affects the coating effect of the positive electrode slurry on the current collector, thereby affecting the uniformity of the positive electrode active material layer and resulting in a low compaction density of the positive electrode sheet.

[0032] According to the inventors' research, the compaction density of the positive electrode sheet can be increased through the following methods:

[0033] 1. Improve the internal density of polyanionic cathode materials.

[0034] Improving the particle density of polyanionic cathode materials can increase the amount of cathode material contained per unit volume, thereby improving the capacity and quality of the material per unit volume, increasing the specific capacity of the battery, enhancing the compressive strength of the particles, increasing the compaction density of the cathode sheet, and thus improving the volumetric energy density of the battery.

[0035] However, excessive particle density in the cathode material can affect the sodium ion solid-phase diffusion rate, leading to increased polarization and a decrease in the battery's specific capacity. Furthermore, excessive particle density makes the particles more prone to sedimentation, affecting the uniformity of the cathode slurry and making it difficult to coat the slurry evenly onto the current collector. This negatively impacts the coating effect and, consequently, the uniformity of the cathode active material layer, resulting in a lower compaction density of the cathode sheet.

[0036] Therefore, within a certain range, the particle density of polyanionic cathode materials helps to increase the sodium ion solid-phase diffusion rate, increase the specific capacity of the battery, reduce particle sedimentation, and improve the uniformity of the cathode slurry. This allows the cathode slurry to be coated more evenly on the current collector, improving the coating effect of the cathode slurry, thereby improving the uniformity of the cathode active material layer, increasing the compaction density of the cathode sheet, and ultimately increasing the volumetric energy density of the battery.

[0037] The particle density of polyanionic cathode materials can be characterized by cross-sectional porosity. Therefore, the cross-sectional porosity of polyanionic cathode materials needs to be within a certain range.

[0038] 2. Rationally combine polyanionic cathode material particles.

[0039] A proper particle arrangement allows the particles to be packed more tightly, reducing the porosity between particles, increasing the compaction density of the positive electrode, and thus improving the volumetric energy density of the battery.

[0040] Low uniformity of particle distribution in the cathode material leads to poor dispersion of the cathode material in the cathode slurry, making the particles more prone to agglomeration. This increases the viscosity and gelation of the cathode slurry, affecting the coating effect and the uniformity of the cathode active material layer, resulting in a lower compaction density of the cathode sheet. Conversely, high uniformity of particle distribution in the cathode material makes it difficult for the particles to pack tightly after the cathode slurry is coated onto the current collector, resulting in larger pores between the particles and a lower compaction density of the cathode sheet.

[0041] Therefore, within a certain range, the uniformity of polyanionic cathode materials helps improve the dispersibility of cathode materials in the cathode slurry, reduces particle agglomeration, lowers the viscosity of the cathode slurry, reduces gelation, and improves the coating effect of the cathode slurry on the current collector. It also helps the cathode material particles on the current collector to pack tightly, reducing the porosity between particles, thereby increasing the compaction density of the cathode sheet and ultimately improving the volumetric energy density of the battery.

[0042] The uniformity of polyanionic cathode materials can be characterized by volumetric particle size distribution, which can be represented by (D90-D10) / D50. D90 refers to the particle size corresponding to 90% of the cumulative volumetric particle size distribution, D50 to 50%, and D10 to 10%. A smaller (D90-D10) / D50 indicates a smaller difference between D90 and D10, a narrower particle distribution, and more uniform particle size. Conversely, a larger (D90-D10) / D50 indicates a larger difference between D90 and D10, a wider particle size distribution, and greater variation in particle size. Therefore, the (D90-D10) / D50 of polyanionic cathode materials needs to be within a certain range.

[0043] 3. Rationally select the specific surface area of ​​polyanionic cathode materials.

[0044] The specific surface area of ​​the cathode material can also affect the stability of the cathode slurry, thus affecting the uniformity of the cathode active material layer, and consequently the compaction density of the cathode sheet, and ultimately the volumetric energy density of the battery. A larger specific surface area of ​​the cathode material increases the contact area between particles, causing more binder and solvent to be adsorbed onto the cathode material surface, reducing the amount of solvent flowing in the cathode slurry. This leads to increased viscosity of the cathode slurry, making it more prone to gelation, affecting the uniformity of the cathode slurry coating on the current collector, and thus affecting the uniformity of the cathode active material layer, resulting in a lower compaction density of the cathode sheet. Conversely, a smaller specific surface area of ​​the cathode material results in a smaller contact area between the cathode material particles and the electrolyte, hindering the diffusion of sodium ions from the cathode material to the electrolyte, thereby reducing the specific capacity of the battery.

[0045] Therefore, a specific surface area within a certain range for polyanionic cathode materials helps increase the amount of solvent flowing in the cathode slurry, reduces the viscosity of the cathode slurry, decreases gelation of the cathode slurry, and improves the coating uniformity of the cathode slurry on the current collector. This, in turn, improves the uniformity of the cathode active material layer, increases the compaction density of the cathode sheet, and consequently improves the volumetric energy density of the battery. It also helps increase the contact area between the cathode material particles and the electrolyte, enhancing the diffusion rate of sodium ions, thereby increasing the specific capacity of the battery.

[0046] Moreover, the ratio of (D90-D10) to D50 of the polyanionic cathode material is within a certain range. Therefore, the specific surface area of ​​the cathode material and the product of (D90-D10) to D50 can be controlled to be within a certain range.

[0047] Therefore, in a first aspect, embodiments of this application provide a positive electrode sheet for a sodium-ion battery, comprising a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode current collector. The positive electrode active material layer contains a polyanionic positive electrode material, the cross-sectional porosity of which is 1%-60%, and the specific surface area of ​​which is denoted as Sm. 2 / g, 1.5≤S≤30, the volumetric particle size distribution (D90-D10) / D50 of the polyanionic cathode material is denoted as K, 0.6≤K≤4, and the polyanionic cathode material satisfies the following relationship: 5≤S*K≤60.

[0048] Specifically, the cross-sectional porosity of the polyanionic cathode material is 1%-60%, for example, it can be a range of 1%, 2%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 27%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or any combination thereof.

[0049] When the cross-sectional porosity of polyanionic cathode materials is between 1% and 60%, it helps to improve the compaction of the cathode material, increase the amount of cathode material contained per unit volume, and thus increase the specific capacity of the battery. It also helps to improve the compressive strength of the particles, increase the compaction density of the cathode sheet, and thus increase the volumetric energy density of the battery. Furthermore, it helps to reduce particle sedimentation, improve the uniformity of the cathode slurry, allowing the cathode slurry to be coated more evenly on the current collector, improving the coating effect of the cathode slurry, thereby improving the uniformity of the cathode active material layer, increasing the compaction density of the cathode sheet, and further increasing the volumetric energy density of the battery. It also helps to improve the sodium ion solid-phase diffusion rate, increasing the specific capacity of the battery.

[0050] The particle size distribution (D90-D10) / D50 of polyanionic cathode materials is denoted as K, where 0.6 ≤ K ≤ 4. For example, K can be a range of 0.6, 0.8, 1, 1.5, 2, 2.5, 3, 3.5, 4, or any combination of two of these ranges.

[0051] When the volumetric particle size distribution (D90-D10) / D50 of the polyanionic cathode material is within the range of 0.6-4, it helps to improve the dispersibility of the cathode material in the cathode slurry, reduce particle agglomeration, lower the viscosity of the cathode slurry, reduce gelation, and improve the coating effect of the cathode slurry. This, in turn, improves the uniformity of the cathode active material layer, increases the compaction density of the cathode sheet, and consequently improves the volumetric energy density of the battery. It also helps to ensure the tight packing of cathode material particles on the current collector, reducing porosity between particles, thereby increasing the compaction density of the cathode sheet and ultimately improving the volumetric energy density of the battery.

[0052] The specific surface area of ​​polyanionic cathode materials is denoted as Sm. 2 / g, the volumetric particle size distribution (D90-D10) / D50 is denoted as K, and the polyanionic cathode material satisfies the following relationship: 5≤S*K≤60. For example, S*K can be a range of 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60 or any two of them.

[0053] When the volumetric particle size distribution (D90-D10) / D50 of the polyanionic cathode material is between 0.6 and 4, and the S*K of the cathode material is between 5 and 60, the specific surface area of ​​the cathode material can be controlled. This helps to increase the amount of solvent flowing in the cathode slurry, reduce the viscosity of the cathode material, reduce the gelation of the cathode slurry, and improve the uniformity of the cathode slurry coating on the current collector. This, in turn, improves the uniformity of the cathode active material layer, increases the compaction density of the cathode sheet, and ultimately improves the volumetric energy density of the battery. It also helps to increase the contact area between the cathode material particles and the electrolyte, enhancing the diffusion rate of sodium ions, thereby increasing the specific capacity of the battery.

[0054] The specific surface area of ​​polyanionic cathode materials is denoted as Sm. 2 / g, 1.5≤S≤30. For example, S can be a range of 1.5, 2, 2.5, 3, 5, 8, 10, 12, 15, 18, 20, 23, 25, 28, 30 or any two of them.

[0055] The specific surface area of ​​the polyanionic cathode material is 0.5 m². 2 / g-30m 2 At a concentration of / g, it helps to reduce the viscosity of the positive electrode slurry, decrease gelation of the positive electrode slurry, improve the uniformity of the positive electrode slurry, and improve the coating uniformity of the positive electrode slurry on the current collector, thereby improving the uniformity of the positive electrode active material layer, increasing the compaction density of the positive electrode sheet, and thus improving the volumetric energy density of the battery. It also helps to increase the diffusion rate of sodium ions, thereby increasing the specific capacity and volumetric energy density of the battery.

[0056] Therefore, by adjusting cross-sectional porosity, volumetric particle size distribution, specific surface area, and the product of specific surface area and volumetric particle size distribution, it is possible to better improve the uniformity of the cathode slurry, reduce its viscosity, decrease its gelation, and improve the coating uniformity of the cathode slurry on the current collector. This, in turn, improves the uniformity of the cathode active material layer, increases the compaction density of the cathode sheet, and ultimately enhances the volumetric energy density of the battery. It can also better improve the diffusion rate of sodium ions, thereby increasing the specific capacity of the battery.

[0057] In some embodiments of this application, the cross-sectional porosity of the polyanionic cathode material is 2%-40%. Within this range, the 1 / s slurry viscosity of the cathode slurry can be lower than 4200 mPa·s, and the compaction density of the cathode sheet can reach or even exceed 2.10 g / cm³. 3 The energy density of polyanionic cathode materials can reach or even exceed 610Wh / L, and the specific capacity of the battery can reach or even exceed 94.0mAh / g.

[0058] Therefore, the cross-sectional porosity of polyanionic cathode materials, ranging from 2% to 40%, helps reduce the viscosity of the cathode slurry, improve its uniformity, and enhance its coating effect. This, in turn, improves the uniformity of the cathode active material layer, increases the compaction density of the cathode sheet, and raises the volumetric energy density of the cathode material, thereby increasing the volumetric energy density of the battery. It also helps to increase the density of particles, increasing the amount of cathode material contained per unit volume, thus improving the specific capacity of the battery.

[0059] In some embodiments of this application, the cross-sectional porosity of the polyanionic cathode material is 5%-20%. Within this range, the 1 / s slurry viscosity of the cathode slurry can be lower than 4000 mPa·s, and the compaction density of the cathode sheet can reach or even exceed 2.25 g / cm³. 3 The volumetric energy density of the cathode material reaches or even exceeds 660Wh / L, and the specific capacity of the battery can reach or even exceed 98.0mAh / g.

[0060] Therefore, the cross-sectional porosity of polyanionic cathode materials is 5%-20%, which can further reduce the viscosity of cathode slurry, increase the compaction density of cathode sheets, and increase the volumetric energy density of cathode materials, thereby improving the specific capacity and volumetric energy density of batteries.

[0061] In some embodiments of this application, the particle size distribution (D90-D10) / D50 of the polyanionic cathode material is denoted as K, where 0.8 ≤ K ≤ 3. Within this range, the 1 / s slurry viscosity of the cathode slurry can be lower than 3800 mPa·s, and the compaction density of the cathode sheet can reach or even exceed 2.18 g / cm³. 3The volumetric energy density of the cathode material can reach or even exceed 630Wh / L, and the specific capacity of the battery can reach or even exceed 97.0mAh / g.

[0062] Therefore, when K is 0.8-3, it helps to reduce the viscosity of the positive electrode slurry, reduce the gelation of the positive electrode slurry, improve the coating effect of the positive electrode slurry, thereby improving the uniformity of the positive electrode active material layer, increasing the compaction density of the positive electrode sheet, and the volumetric energy density of the positive electrode material, thus improving the volumetric energy density and specific capacity of the battery.

[0063] In some embodiments of this application, 0.8 ≤ K ≤ 2. Within this range, the 1 / s slurry viscosity of the positive electrode slurry can be lower than 3600 mPa·s, and the compaction density of the positive electrode sheet can reach or even exceed 2.25 g / cm³. 3 The volumetric energy density of the cathode material can reach or even exceed 660Wh / L, and the specific capacity of the battery can reach or even exceed 98.5mAh / g.

[0064] Therefore, when K is 0.8-2, the viscosity of the positive electrode slurry can be further reduced, the fluidity of the positive electrode slurry can be improved, the compaction density of the positive electrode sheet can be further improved, and the volumetric energy density of the positive electrode material can be improved, thereby improving the volumetric energy density and specific capacity of the battery.

[0065] In some embodiments of this application, the specific surface area of ​​the polyanionic cathode material is denoted as Sm. 2 For polyanionic cathode materials, the volumetric particle size distribution (D90-D10) / D50 is denoted as K. The following relationship applies: 6 ≤ S*K ≤ 45. Within this range, the 1 / s slurry viscosity of the cathode slurry is below 4600 mPa·s, and the compaction density of the cathode sheet can reach or even exceed 2.10 g / cm³. 3 The volumetric energy density of the cathode material can reach or even exceed 625Wh / L, and the specific capacity of the battery can reach or even exceed 95.5mAh / g.

[0066] Therefore, when S*K is 6-45, it helps to reduce the viscosity of the cathode material, reduce the gelation of the cathode slurry, improve the coating uniformity of the cathode material on the current collector, thereby improving the uniformity of the cathode active material layer, increasing the compaction density of the cathode sheet, increasing the volumetric energy density of the cathode material, and thus improving the volumetric energy density and specific capacity of the battery.

[0067] In some embodiments of this application, 10 ≤ S*K ≤ 20. Within this range, the 1 / s slurry viscosity of the positive electrode slurry can be lower than 3800 mPa·s, and the compaction density of the positive electrode sheet can reach or even exceed 2.15 g / cn. 3The volumetric energy density of the cathode material can reach or even exceed 635Wh / L, and the specific capacity of the battery can reach or even exceed 97.0mAh / g.

[0068] Therefore, when S*K is 10-20, the viscosity of the cathode material can be further reduced, the compaction density of the cathode sheet and the volumetric energy density of the cathode material can be increased, thereby further improving the volumetric energy density and specific capacity of the battery.

[0069] In some embodiments of this application, the specific surface area of ​​the polyanionic cathode material is denoted as Sm. 2 / g, 2≤S≤20. Within this range, the 1 / s slurry viscosity of the positive electrode slurry is less than 4200 mPa·s, and the compaction density of the positive electrode sheet can reach or even exceed 2.20 g / cm³. 3 The volumetric energy density of the cathode material can reach or even exceed 635Wh / L, and the specific capacity of the battery can reach or even exceed 95.5mAh / g.

[0070] Therefore, when S is 2-20, it helps to reduce the viscosity of the positive electrode slurry, reduce the gelation of the positive electrode slurry, improve the coating uniformity of the positive electrode material, improve the uniformity of the positive electrode active material layer, thereby increasing the compaction density of the positive electrode sheet and the volumetric energy density of the positive electrode material, and thus improving the volumetric energy density and specific capacity of the battery.

[0071] In some embodiments of this application, 3 ≤ S ≤ 15. Within this range, the 1 / s slurry viscosity of the positive electrode slurry is less than 4000 mPa·s, and the compaction density of the positive electrode sheet can reach or even exceed 2.27 g / cm³. 3 The energy density of the cathode material can reach or even exceed 655Wh / L, and the specific capacity of the battery can reach or even exceed 98.0mAh / g.

[0072] Therefore, when S is 3-15, the viscosity of the positive electrode slurry can be further reduced, the compaction density of the positive electrode sheet can be increased, and the volumetric energy density of the positive electrode material can be increased, thereby further improving the volumetric energy density and specific capacity of the battery.

[0073] In some embodiments of this application, considering that a reasonable particle configuration helps to improve the compaction density of the positive electrode sheet and reduce ion diffusion resistance, thereby improving the volumetric energy density of the battery, the polyanionic positive electrode material in this embodiment satisfies the following relationships: 0.5μm≤D10≤10μm, 3μm≤D50≤15μm, and 10μm≤D90≤60μm.

[0074] In this application, D10 is 0.5μm-10μm, D50 is 3μm-15μm, and D90 is 10μm-60μm, which helps to reduce the porosity between particles, thereby increasing the compaction density of the positive electrode sheet and thus increasing the volumetric energy density of the battery.

[0075] For example, D10 can be a range of 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm or any combination thereof.

[0076] D50 can be a range of 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, or any combination thereof.

[0077] D90 can be a range of 10μm, 15μm, 18μm, 20μm, 22μm, 25μm, 28μm, 30μm, 33μm, 35μm, 38μm, 40μm, 45μm, 50μm, 55μm, 60μm, or any combination thereof.

[0078] In some embodiments of this application, the chemical formula of the polyanionic cathode material is Na. x M y (PO4) w X a Z b Y c M is at least one of Ti, V, Cr, Mn, Fe, Co, and Ni; X is at least one of S, P, Si, W, and B; Z is at least one of F, O, and OH; and Y is at least one of C and Al.

[0079] In this application, sodium ions can be reversibly inserted and extracted into the positive electrode active material, enabling sodium-ion batteries to achieve charge-discharge cycles.

[0080] Transition metal elements (M) contribute electrochemical activity, enhance structural stability, and improve conductivity and thermal stability in polyanionic cathode materials. By selecting and optimizing the type and proportion of transition metals, the battery's capacity, energy density, cycle life, and safety can be significantly improved. For example, titanium has good chemical stability and safety and is often used to improve the material's cycle life and thermal stability; vanadium has multiple oxidation states and can provide high capacity and good rate performance; chromium can improve the material's structural stability and corrosion resistance; manganese is inexpensive and environmentally friendly, and has good electrochemical stability; iron is abundant and low-cost, and has good safety and environmental friendliness; cobalt has high conductivity and good electrochemical performance; and nickel has high capacity and good rate performance.

[0081] (PO4)w X a Z b Typically, stable crystal frameworks are formed, such as phosphates or complex phosphates, providing structural support for the insertion and extraction of sodium ions and transition metal ions. This helps maintain the structural integrity of the material during charge and discharge, and can also provide higher energy and improve the electrochemical performance of the battery. X can be selected from at least one of S, P, Si, W, and B. Sulfur can provide high capacity, and sulfur-based compounds such as sulfides are used to improve energy density; phosphorus can improve the thermal stability and safety of the material, and phosphates such as lithium iron phosphate are used to provide high safety; silicon has high theoretical capacity, and silicon-based materials are used to improve capacity and energy density; tungsten has high density and good mechanical properties, and tungsten-based materials are used to enhance structural stability; boron can improve the conductivity and thermal stability of the material, and borides are used to improve conductivity and thermal stability.

[0082] Z can be used to improve chemical stability and ionic conductivity. Z can be selected from at least one of O, F, and OH. Oxygen can regulate the proportion of phosphates or complex phosphates in the crystal framework. Fluorine can improve the electrochemical stability and corrosion resistance of materials; fluorides are used to improve voltage and stability. Hydroxyl groups can improve the hydrophilicity and ionic conductivity of materials; hydroxyl compounds are used to improve ionic conductivity.

[0083] Y (yet) can be used to enhance electrical conductivity, structural stability, and thermal stability. Y can be selected from at least one of C and Al. Carbon and aluminum have good electrical conductivity and are lightweight, and are used to improve conductivity and reduce weight.

[0084] Wherein, 2.8≤x≤4.2, 1.9≤y≤3.1, 1.8≤w≤2.2, 0≤a≤3.0, 0≤b≤8.0, and 0≤c≤3.0. By adjusting these stoichiometric ratios, the electrochemical performance, structural stability, and other properties of the material can be optimized.

[0085] In some embodiments of this application, the polyanionic cathode material is at least one of single crystal, quasi-single crystal, and polycrystalline.

[0086] Single-crystal materials have a complete crystal structure, which reduces stress concentration points that may lead to material degradation during charging and discharging, and exhibits higher mechanical stability, which helps to extend the cycle life of the battery.

[0087] Polycrystalline materials can have their performance optimized by adjusting grain size and shape, offering greater design flexibility and a higher reaction rate, making them suitable for applications requiring rapid charge and discharge.

[0088] Single-crystal-like materials combine the advantages of single crystals and polycrystalline materials, exhibiting fewer grain boundaries and good structural integrity, as well as excellent stability and good rate performance during cycling.

[0089] In some embodiments of this application, the polyanionic cathode material can be at least one of fully broken particles, partially broken particles, and uncrushed particles.

[0090] Completely broken particles refer to materials in which the original particles have been completely broken into smaller particles or powder. Completely broken particles have a larger specific surface area, which can increase the contact area with the electrolyte, thereby improving the electrochemical reaction rate.

[0091] Semi-crushed granular materials refer to materials in which the original particles are partially crushed to form a mixture of particles of varying sizes. While maintaining a certain degree of structural integrity, the semi-crushed particles increase the surface area, thereby achieving a balance between mechanical stability and reactivity.

[0092] Unbroken granular materials refer to materials in which the original granules retain their integrity without undergoing significant mechanical breakage. Unbroken granules maintain a complete crystal structure and typically have higher mechanical stability, making them suitable for long-life applications.

[0093] The positive electrode sheet for sodium-ion batteries of this application can be prepared using conventional techniques in the art. It can be prepared by wet or dry formulation. For example, the above-mentioned positive electrode material, conductive agent, and binder can be uniformly dispersed in a solvent to obtain a positive electrode slurry. Then, the positive electrode slurry is coated on at least one functional surface of the positive electrode current collector, and after drying, the positive electrode sheet of this application can be obtained.

[0094] The positive current collector in this application can be selected from positive current collectors conventionally used in the art, such as aluminum foil.

[0095] The conductive agent, adhesive, and other components can all be selected from conventional substances in the field. For example, the conductive agent can be selected from one or more of conductive carbon black (SP), carbon nanotubes, carbon nanofibers, Ketjen black, graphyne, conductive graphite, and graphene. The adhesive can be selected from one or more of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), hydrogenated nitrile rubber (HNBR), sodium alginate (SA), polytetrafluoroethylene (PTEE), acrylic modified PVDF, polyacrylate polymers, polyimide, styrene-butadiene rubber (SBR), and styrene-acrylic rubber.

[0096] This application does not specify the coating method; any coating method such as gravure coating, extrusion coating, spraying, or screen printing can be used to achieve the coating of the positive electrode active layer slurry.

[0097] Secondly, this application provides a battery including the positive electrode sheet for a sodium-ion battery as described above, which has advantages corresponding to the aforementioned positive electrode sheet, and will not be elaborated further.

[0098] In addition to the positive electrode, the battery of this application also includes a separator, a negative electrode, and an electrolyte. The composition of the negative electrode can refer to conventional negative electrode sheets in the art, and the separator can also be a separator commonly used in the art, such as PP film, PE film, etc.

[0099] The battery of this application can be prepared using conventional methods in the art. Specifically, the positive electrode, separator and negative electrode can be stacked in sequence, and the cell can be obtained by stacking or winding. Then, the battery can be obtained by baking, liquid injection, formation and packaging.

[0100] Batteries can be liquid batteries, solid-state batteries, or semi-solid-state batteries, and their shapes can be prismatic, cylindrical, or pouch batteries.

[0101] Thirdly, this application provides a battery pack including the battery as described above, which has advantages corresponding to the above-mentioned positive electrode plate, which will not be elaborated further.

[0102] Fourthly, this application provides an electrical device, including the battery or battery pack described above, which has advantages corresponding to the positive electrode plate described above, and will not be elaborated further.

[0103] The electrical equipment used in this application can be conventional electrical equipment in the field, such as power equipment (e.g., electric vehicles), electronic equipment (e.g., computers, mobile phones, digital cameras, printers, fax machines, etc.), wearable devices (e.g., watches, wristbands, VR glasses, etc.), and household appliances (e.g., air conditioners, refrigerators, washing machines, microwave ovens, etc.), etc., without any particular limitation.

[0104] For example, in addition to the battery mentioned above, the electrical device may also include control components, input components, output components, communication components, and storage components. Control components may include, for example, a microcontroller or processor, for handling the device's logic control and data processing; input components may include, for example, a keyboard or touchscreen, for user input; output components may include, for example, a speaker, for audio output; communication components may include, for example, Wi-Fi or Bluetooth, for communication; and storage components may include, for example, memory or storage devices, for storing data and programs.

[0105] The present application will be further described below through specific embodiments.

[0106] It should be noted that the cross-sectional porosity, volumetric particle size distribution, and specific surface area of ​​polyanionic cathode materials can be obtained by disassembling the product and conducting tests.

[0107] Specifically, the disassembly process involves the following: Battery cell types include, but are not limited to, pouch cells, prismatic cells, and cylindrical cells. The battery is discharged to 2.0V under a low current (e.g., 0.05C / 0.1C / 0.2C) and then disassembled in an inert environment. The positive electrode is removed, cleaned with an organic solvent, and the positive electrode powder material is scraped off. The organic solvent can be one or more types of alcohols, esters, or ethers.

[0108] Then, the scraped positive electrode powder material (such as the above-mentioned polyanionic positive electrode material, conductive agent, and binder) is ultrasonically cleaned for 10 minutes to remove the floating matter on the upper layer. Organic solvent is added again, and ultrasonic cleaning is performed for 10 minutes. The cleaning is repeated three times. The bottom layer material is taken and vacuum dried until the powder moisture content is below 500 ppm.

[0109] After cleaning and drying the positive electrode sheet, cross-sectional porosity testing can be performed. After cleaning and drying the scraped positive electrode powder material, volumetric particle size distribution and specific surface area testing can be performed.

[0110] Cross-sectional porosity test: The cross-section of the positive electrode is cut by plasma beam, magnified 1000 times, and 10 SEM images are taken. The proportion of particle porosity in the SEM images is counted (porosity = particle cross-sectional pore area / particle cross-sectional area).

[0111] Volumetric particle size distribution test: The volumetric particle size distribution of the cathode material is tested using a Malvern 3000 laser particle size analyzer, for example, referring to GB / T 19077.1.

[0112] Specific surface area test: The specific surface area of ​​the cathode material is tested using the nitrogen isothermal adsorption-desorption method. For example, refer to GB / T 19587. The p / p0 (relative pressure) value range is 0.05 to 0.30. The five measurement points selected within this range should be evenly distributed as much as possible. The maximum value among the five test points should not be lower than 0.20. The linear correlation coefficient should be ≥0.999. The degassing conditions are 2h and 200℃.

[0113] In practical applications, the cathode material undergoes multiple steps such as mixing, coating, drying, and compaction during battery manufacturing. Therefore, after disassembling the product, the cross-sectional porosity, volumetric particle size distribution, and specific surface area are tested. The results may have slight differences compared to the test results of the raw material, which can be ignored.

[0114] Example 1

[0115] The method for preparing the sodium-ion battery in this embodiment includes the following steps:

[0116] (1) The cross-sectional porosity is 8% and the specific surface area is 6.9 m². 2A polyanionic cathode material with a density of / g, K = 1.5, and S*K = 6.9, and the chemical formula is Na. 3.95 Fe 3.04 (PO4)2(P 1.98 O 7.02 The crystal form is Pn21a. It is mixed with SP, PVDF and NMP (N-methylpyrrolidone) in a mass ratio of 93:4:3:60, and then coated on aluminum foil current collector. After drying, it is rolled to obtain a positive electrode sheet. S is the specific surface area value without unit, and K is (D90-D10) / D50.

[0117] (2) Hard carbon, SP, CMC, SBR and deionized water are mixed evenly in a mass ratio of 90:4:3:3:50, and then coated on aluminum foil current collector. After drying, the negative electrode sheet is obtained by rolling.

[0118] (3) The positive electrode, negative electrode and separator are stacked sequentially in an orderly manner to obtain the electrode core;

[0119] (4) After the electrode core is encased, electrolyte is injected, and sodium-ion batteries are obtained through formation and capacity testing.

[0120] Example 2

[0121] The preparation method of the sodium-ion battery in Example 2 is basically the same as that in Example 1, except that a cross-sectional porosity of 1% and a specific surface area of ​​6.9 m² are used. 2 Preparation of polyanionic cathode material with K = 1.5 and S*K = 6.9.

[0122] Example 3

[0123] The preparation method of the sodium-ion battery in Example 3 is the same as that in Example 1, except that a cross-sectional porosity of 2% and a specific surface area of ​​6.9 m² are used. 2 Preparation of polyanionic cathode material with K = 1.5 and S*K = 6.9.

[0124] Example 4

[0125] The preparation method of the sodium-ion battery in Example 4 is the same as that in Example 1, except that a cross-sectional porosity of 3% and a specific surface area of ​​6.9 m² are used. 2 Preparation of polyanionic cathode material with K = 1.5 and S*K = 6.9.

[0126] Example 5

[0127] The preparation method of the sodium-ion battery in Example 5 is the same as that in Example 1, except that a cross-sectional porosity of 5% and a specific surface area of ​​6.9 m² are used. 2Preparation of polyanionic cathode material with K = 1.5 and S*K = 6.9.

[0128] Example 6

[0129] The preparation method of the sodium-ion battery in Example 6 is the same as that in Example 1, except that a cross-sectional porosity of 20% and a specific surface area of ​​6.9 m² are used. 2 Preparation of polyanionic cathode material with K = 1.5 and S*K = 6.9.

[0130] Example 7

[0131] The preparation method of the sodium-ion battery in Example 7 is the same as that in Example 1, except that a cross-sectional porosity of 30% and a specific surface area of ​​6.9 m² are used. 2 Preparation of polyanionic cathode material with K = 1.5 and S*K = 6.9.

[0132] Example 8

[0133] The preparation method of the sodium-ion battery in Example 8 is the same as that in Example 1, except that a cross-sectional porosity of 40% and a specific surface area of ​​6.9 m² are used. 2 Preparation of polyanionic cathode material with K = 1.5 and S*K = 6.9.

[0134] Example 9

[0135] The preparation method of the sodium-ion battery in Example 9 is the same as that in Example 1, except that a cross-sectional porosity of 60% and a specific surface area of ​​6.9 m² are used. 2 Preparation of polyanionic cathode material with K = 1.5 and S*K = 6.9.

[0136] Example 10

[0137] The preparation method of the sodium-ion battery in Example 10 is the same as that in Example 1, except that it uses a cross-sectional porosity of 8% and a specific surface area of ​​1.5 m². 2 Preparation of polyanionic cathode material with K = 3.34 and S*K = 5.01.

[0138] Example 11

[0139] Example 11 is prepared using the same method as Example 1 for a sodium-ion battery, except that it uses a cross-sectional porosity of 8% and a specific surface area of ​​2m². 2 Preparation of polyanionic cathode material with K = 4 and S*K = 8.

[0140] Example 12

[0141] Example 12 is prepared using the same method as the sodium-ion battery in Example 1, except that it uses a cross-sectional porosity of 8% and a specific surface area of ​​3m². 2 Preparation of polyanionic cathode material with K = 4 and S*K = 12 / g.

[0142] Example 13

[0143] Example 13 is prepared using the same method as the sodium-ion battery in Example 1, except that it uses a cross-sectional porosity of 8% and a specific surface area of ​​15m². 2 Preparation of polyanionic cathode material with K = 1.5 and S*K = 22.5 / g.

[0144] Example 14

[0145] Example 14 uses the same method as Example 1 for preparing a sodium-ion battery, except that it uses a cross-sectional porosity of 8% and a specific surface area of ​​17.2 m². 2 Preparation of polyanionic cathode material with K = 1.5 and S*K = 25.8 / g.

[0146] Example 15

[0147] Example 15 is prepared using the same method as the sodium-ion battery in Example 1, except that it uses a cross-sectional porosity of 8% and a specific surface area of ​​20 m². 2 Preparation of polyanionic cathode material with K = 1.5 and S*K = 30 / g.

[0148] Example 16

[0149] Example 16 uses the same method as Example 1 for preparing a sodium-ion battery, except that it uses a cross-sectional porosity of 8% and a specific surface area of ​​29.6 m². 2 Preparation of polyanionic cathode material with K = 1.5 and S*K = 44.4 / g.

[0150] Example 17

[0151] Example 17 is prepared using the same method as the sodium-ion battery in Example 1, except that it uses a cross-sectional porosity of 8% and a specific surface area of ​​10 m². 2 Preparation of polyanionic cathode material with K = 0.6 and S*K = 6.

[0152] Example 18

[0153] The preparation method of the sodium-ion battery in Example 18 is the same as that in Example 1, except that it uses a cross-sectional porosity of 8% and a specific surface area of ​​6.9 m². 2 Preparation of polyanionic cathode material with K = 0.8 and S*K = 5.52.

[0154] Example 19

[0155] Example 19 uses the same method as Example 1 for preparing a sodium-ion battery, except that it uses a cross-sectional porosity of 8% and a specific surface area of ​​6.9 m². 2 Preparation of polyanionic cathode material with K = 2 and S*K = 13.8 / g.

[0156] Example 20

[0157] The preparation method of the sodium-ion battery in Example 20 is the same as that in Example 1, except that it uses a cross-sectional porosity of 8% and a specific surface area of ​​6.9 m². 2 Preparation of polyanionic cathode material with K = 2.4 and S*K = 16.56.

[0158] Example 21

[0159] The preparation method of the sodium-ion battery in Example 21 is the same as that in Example 1, except that it uses a cross-sectional porosity of 8% and a specific surface area of ​​6.9 m². 2 Preparation of polyanionic cathode material with K = 2.89 and S*K = 19.94.

[0160] Example 22

[0161] Example 22 uses the same method as Example 1 for preparing a sodium-ion battery, except that it uses a cross-sectional porosity of 8% and a specific surface area of ​​6.9 m². 2 Preparation of polyanionic cathode material with K = 4 and S*K = 27.6 / g.

[0162] Example 23

[0163] Example 23 is prepared using the same method as the sodium-ion battery in Example 1, except that it uses a cross-sectional porosity of 8% and a specific surface area of ​​30 m². 2 Preparation of polyanionic cathode material with K = 3 and S*K = 60 / g.

[0164] Comparative Example 1

[0165] The sodium-ion battery in Comparative Example 1 was prepared using the same method as that in Example 1, except that it used a cross-sectional porosity of 62% and a specific surface area of ​​30 m². 2 Preparation of polyanionic cathode material with K = 1.5 and S*K = 10.35 / g.

[0166] Comparative Example 2

[0167] Comparative Example 2 was prepared using the same method as the sodium-ion battery in Example 1, except that it used a cross-sectional porosity of 0.02% and a specific surface area of ​​6.9 m².2 Preparation of polyanionic cathode material with K = 1.5 and S*K = 10.35 / g.

[0168] Comparative Example 3

[0169] The sodium-ion battery in Comparative Example 3 was prepared using the same method as that in Example 1, except that it used a cross-sectional porosity of 8% and a specific surface area of ​​34.5 m². 2 Preparation of polyanionic cathode material with K = 1.5 and S*K = 51.75 / g.

[0170] Comparative Example 4

[0171] The sodium-ion battery in Comparative Example 4 was prepared using the same method as that in Example 1, except that it used a cross-sectional porosity of 8% and a specific surface area of ​​0.3 m². 2 Preparation of polyanionic cathode material with K = 1.5 and S*K = 0.45 / g.

[0172] Comparative Example 5

[0173] The sodium-ion battery in Comparative Example 5 was prepared using the same method as that in Example 1, except that it used a cross-sectional porosity of 8% and a specific surface area of ​​6.9 m². 2 Preparation of polyanionic cathode material with K = 4.7 and S*K = 32.43.

[0174] Comparative Example 6

[0175] The sodium-ion battery in Comparative Example 6 was prepared using the same method as that in Example 1, except that it used a sodium-ion battery with a porosity of 8% and a specific surface area of ​​6.9 m². 2 Preparation of polyanionic cathode material with K = 0.4 and S*K = 2.76.

[0176] Comparative Example 7

[0177] The sodium-ion battery in Comparative Example 7 was prepared using the same method as that in Example 1, except that it used a cross-sectional porosity of 8% and a specific surface area of ​​25.4 m². 2 Preparation of polyanionic cathode material with K = 3.1 and S*K = 78.74.

[0178] Comparative Example 8

[0179] The sodium-ion battery in Comparative Example 8 was prepared using the same method as that in Example 1, except that it used a cross-sectional porosity of 8% and a specific surface area of ​​0.7 m². 2 Preparation of polyanionic cathode material with K = 1.2 and S*K = 0.84.

[0180] The specific volume, compaction density, and volumetric energy density of Examples 1-23 and Comparative Examples 1-8 were tested respectively, and the test results are shown in Table 1 below. The specific test methods are as follows:

[0181] Specific capacity test: The battery is charged to 3.8V under 1 / 3C conditions and discharged to 2.0V under 1 / 3C conditions, and the cycle is repeated 3 times. The specific capacity is calculated based on the capacity of the last test.

[0182] Compacted density test: The weight and thickness of a fixed area of ​​positive electrode sheet are measured, and then the compacted density is obtained based on the ratio of the mass of the dressing to the volume of the dressing.

[0183] Volumetric energy density test: The battery is charged to 3.8V under 1 / 3C conditions and discharged to 2.0V under 1 / 3C conditions for 3 cycles. The specific capacity and average voltage of the last test are taken, and the volumetric energy density of the positive electrode material is calculated in combination with the compaction density of the positive electrode sheet.

[0184] Slurry viscosity test: The viscosity of the slurry is tested at a shear rate of 1 / s.

[0185] Table 1

[0186] The following conclusions can be drawn from Table 1:

[0187] 1) As can be seen from Examples 1 to 23 and Comparative Examples 1 to 8, the cross-sectional porosity and specific surface area Sm of the polyanionic cathode material are relatively high. 2 When / g, K=(D90-D10) / D50 and S*K are within the range of the embodiments of this application, it helps to improve the volumetric energy density of the cathode material, reduce the viscosity of the cathode slurry, thereby improving the compaction density of the cathode sheet, and thus the volumetric energy density and specific capacity of the battery.

[0188] 2) As can be seen from Example 1 and Comparative Example 1, if the cross-sectional porosity of the polyanionic cathode material is too high, it will increase the viscosity of the cathode slurry, reduce the compaction density of the cathode sheet, the volumetric energy density of the cathode material, and the specific capacity of the battery.

[0189] 3) As can be seen from Example 1 and Comparative Example 2, the cross-sectional porosity of the polyanionic cathode material is too low. Although it can increase the compaction density of the cathode sheet, it will increase the viscosity of the cathode slurry and reduce the volumetric energy density of the polyanionic cathode material and the specific capacity of the battery.

[0190] 4) As can be seen from Example 1 and Comparative Example 3, if the specific surface area of ​​the polyanionic cathode material is too high, it will increase the viscosity of the cathode slurry, reduce the compaction density of the cathode sheet, the volumetric energy density of the polyanionic cathode material, and the specific capacity of the battery.

[0191] 5) As can be seen from Example 1 and Comparative Example 4, if the specific surface area of ​​the polyanionic cathode material is too low, it will increase the viscosity of the cathode slurry, reduce the compaction density of the cathode sheet, the volumetric energy density of the polyanionic cathode material, and the specific capacity of the battery.

[0192] 6) As can be seen from Example 1 and Comparative Example 5, if the K of the polyanionic cathode material is too high, it will increase the viscosity of the cathode slurry, reduce the compaction density of the cathode sheet, the volumetric energy density of the polyanionic cathode material, and the specific capacity of the battery.

[0193] 7) As can be seen from Example 1 and Comparative Example 6, if the K of the polyanionic cathode material is too low, it will increase the viscosity of the cathode slurry, reduce the compaction density of the cathode sheet, the volumetric energy density of the polyanionic cathode material, and the specific capacity of the battery.

[0194] 8) As can be seen from Example 1 and Comparative Example 7, even if the specific surface area and K of the polyanionic cathode material are within a specific range, if their product is too large, it will still increase the viscosity of the cathode slurry, reduce the compaction density of the cathode sheet, the volumetric energy density of the polyanionic cathode material, and the specific capacity of the battery.

[0195] 9) As can be seen from Example 1 and Comparative Example 8, even if the specific surface area and K of the polyanionic cathode material are within a specific range, if their product is too small, although the viscosity of the cathode slurry will be reduced, the compaction density of the cathode sheet, the volumetric energy density of the polyanionic cathode material, and the specific capacity of the battery will be reduced.

[0196] By using cross-sectional porosity and specific surface area Sm within a specific range 2 Using polyanionic cathode materials of / g, K, and S*K to prepare sodium-ion batteries can improve the volumetric energy density of the cathode material, reduce the viscosity of the cathode slurry, and increase the compaction density of the cathode sheet, thereby improving the volumetric energy density and specific capacity of the battery.

[0197] Finally, it should be noted that other embodiments of this application will readily conceive of by those skilled in the art upon consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and alterations may be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A positive electrode for a sodium-ion battery, wherein, It includes a positive current collector and a positive active material layer located on at least one side of the positive current collector, the positive active material layer containing a polyanionic positive electrode material; The cross-sectional porosity of the polyanionic cathode material is 1%-60%; The specific surface area of ​​the polyanion-type cathode material is denoted as Sm. 2 / g, 1.5≤S≤30; The volumetric particle size distribution (D90-D10) / D50 of the polyanionic cathode material is denoted as K, where 0.6≤K≤4; The polyanionic cathode material satisfies the following relationship: 5≤S*K≤60.

2. The positive electrode according to claim 1, wherein, 0.8≤K≤3。 3. The positive electrode according to claim 1 or 2, wherein, 0.8≤K≤2。 4. The positive electrode according to any one of claims 1-3, wherein, 6≤S*K≤45.

5. The positive electrode according to any one of claims 1-4, wherein, 10≤S*K≤20.

6. The positive electrode according to any one of claims 1-5, wherein, 2≤S≤20。 7. The positive electrode according to any one of claims 1-6, wherein, 3≤S≤15。 8. The positive electrode according to any one of claims 1-7, wherein, The cross-sectional porosity of the polyanionic cathode material is 2%-40%.

9. The positive electrode according to any one of claims 1-8, wherein, The cross-sectional porosity of the polyanionic cathode material is 5%-20%.

10. The positive electrode according to claim 1, wherein, 0.5μm≤D10≤10μm, 3μm≤D50≤15μm, 10≤D90≤60μm.

11. The positive electrode according to any one of claims 1-10, wherein, The chemical formula of the polyanionic cathode material is Na. x M y (PO4) w X a Z b Y c M is at least one of Ti, V, Cr, Mn, Fe, Co, and Ni; X is at least one of S, P, Si, W, and B; Z is at least one of F, O, and OH; and Y is at least one of C and Al. 2.8≤x≤4.2, 1.9≤y≤3.1, 1.8≤w≤2.2, 0≤a≤3.0, 0≤b≤8.0, 0≤c≤3.

0.

12. The positive electrode according to any one of claims 1-11, wherein, The polyanionic cathode material is at least one of single crystal, quasi-single crystal, and polycrystalline.

13. A battery, wherein, Includes the positive electrode sheet for sodium-ion batteries as described in any one of claims 1-12.

14. A battery pack, wherein, Includes the battery as described in claim 13.

15. An electrical appliance, wherein, Includes the battery of claim 13 or the battery pack of claim 14.

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