Sodium-ion battery positive electrode material and manufacturing method thereof

Abstract

The invention relates to a sodium ion battery positive electrode material and a manufacturing method thereof, and a sodium ion battery adopting the positive electrode material. The positive electrode material is composed of a first component material and a second component material, wherein the first component material has a higher discharge plateau voltage than the second component material. The two materials are combined through the coating structure, namely the first component material coats the surface of the second component material, or vice versa, the advantages of the two materials are fully utilized, and the overall performance of the material is improved. The electrochemical performance of the battery is further optimized by regulating and controlling the discharge platform voltage difference value (within the range of 0.1-1.6 V) of the two component materials. In addition, the weight ratio (within the range of 1%-50%) of the first component material is regulated and controlled, and balance of performance and cost is achieved. According to the manufacturing method, the processes of long-time ball milling (gt, 8 h) and high-temperature sintering (gt, 300 DEG C) are adopted, and a stable coating structure is formed. The sodium ion battery prepared from the positive electrode material is excellent in specific discharge capacity, plateau voltage and the like.

Description

Technical Field

[0001] This application relates to the technical field of sodium batteries, and particularly to a cathode material for a sodium-ion battery and a manufacturing method thereof. Background Art

[0002] Under the current background of the global green energy transformation, the new energy vehicle and electrochemical energy storage industries have ushered in unprecedented development opportunities. As the key technical support for these two major fields, the innovation of battery technology is particularly important. However, the lithium batteries that are currently mainly relied on in new energy vehicles and energy storage systems have relatively low content of raw material lithium resources in the earth's crust, and their geographical distribution is extremely uneven, mainly concentrated in places such as South America and Australia. For a country like ours with a huge energy demand and a high degree of concern for energy security, this undoubtedly poses long-term strategic challenges and potential development bottlenecks.

[0003] Under this background, sodium-ion batteries, with their rich raw materials, obvious cost advantages, and excellent low-temperature performance, have gradually come into people's view and are regarded as a powerful supplement to lithium batteries in some application markets. The abundance of sodium in the earth's crust is 1000 times that of lithium, and this unique resource advantage has laid a solid foundation for the industrial application of sodium-ion batteries. Especially in the energy storage and A0-class vehicle markets, sodium-ion batteries show great application potential due to their cost advantages and adaptability to low-temperature environments.

[0004] However, although sodium-ion batteries have broad prospects, the research and development of their cathode materials still face many challenges. Due to the limitations of the intrinsic properties of the materials, the existing sodium cathode materials generally have problems such as insufficient specific capacity and poor cycling performance, and these disadvantages seriously restrict the rapid popularization and commercial application of sodium-ion batteries. To overcome these technical problems, researchers have carried out a series of beneficial explorations. For example, there is a prior art that proposes a scheme of coating sodium iron sulfate with sodium vanadium phosphate, a polyanion-type sodium battery cathode material. By controlling the thickness and ratio of the coating layer, the specific capacity of the material is effectively improved, and its processing stability is enhanced. In addition, there are also technical solutions that are further innovated. By preparing nano-scale ferrous sulfate powder and in-situ coating technology, the voltage platform and cycling performance of the sodium iron sulfate-based cathode material are improved. These research results provide valuable ideas and experiences for the optimization of sodium-ion battery cathode materials. The research and development of sodium-ion battery cathode materials still need to be continuously deepened to further solve the existing performance bottlenecks and promote the progress of sodium-ion battery technology. Summary of the Invention

[0005] The purpose of this application is to provide a cathode material for sodium-ion batteries, which combines the advantages of different sodium-ion cathode materials, realizes the balance of the performance of sodium-ion battery materials through coating, and improves the energy density. The cathode material for sodium-ion batteries of this application includes a first component material and a second component material; The first component material is a polyanion material, the second component material is a polyanion material, and the discharge platform voltage of the first component material is greater than the discharge platform voltage of the second component material; Wherein, the first component material is coated on the surface of the second component material, or the second component material is coated on the surface of the first component material.

[0006] In one embodiment, the discharge platform voltage of the first component material is greater than or equal to 3V.

[0007] In one embodiment, the difference between the discharge platform voltage of the first component material and the discharge platform voltage of the second component material is in the range of 0.1 - 1.6V.

[0008] In one embodiment, the weight ratio of the first component material is in the range of 1% - 50%.

[0009] In one embodiment, the thickness of the component material coated on the outer layer is in the range of 30nm - 2000nm.

[0010] In one embodiment, the first component material is Na a M b (X c O d ) e Z f , where M is selected from one or more of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ca, Mg, Al, and Nb, X is selected from one or more of C, Se, Si, S, P, As, B, Mo, W, and Ge, and Z is selected from O, F, OH, or blank.

[0011] This application further provides a method for manufacturing a cathode material for sodium-ion batteries, including: Determine the first component material and the second component material, wherein the discharge platform voltage of the first component material is greater than the discharge platform voltage of the second component material; Weigh the first component material and the second component material respectively, and carry out pulverization and mixing; After pulverization and mixing, sinter the mixed material under an inert atmosphere.

[0012] In one embodiment, use a ball milling tank to carry out pulverization and mixing by ball milling.

[0013] In one embodiment, the duration of ball milling is greater than 8 h, and the sintering temperature is greater than 300 °C.

[0014] In one embodiment, by selecting the first component material and the second component material with different particle sizes, mutual coating of the first component material and the second component material is achieved, and the particle size of the material coating layer is less than 1 / 10 of the particle size of the inner layer material.

[0015] This application also provides a sodium-ion battery, including the aforementioned sodium-ion battery cathode material.

[0016] Compared with the prior art, this application has the following beneficial effects: Through component selection and structural layout, this application realizes the comprehensive advantages of different sodium-ion cathode materials. The first component material, as a polyanion material, has a relatively high discharge platform voltage and stable structural characteristics, while the second component material can be another polyanion material with a relatively low discharge platform voltage. By coating the first component material on the surface of the second component material, or vice versa, this application effectively balances the voltage platform, energy density, and cycle performance of the material, achieving an overall improvement in material performance.

[0017] Specifically, when the discharge platform voltage of the first component material is greater than or equal to 3 V and the difference in the discharge platform voltage from the second component material is in the range of 0.1 V - 1.6 V, the coating structure can make full use of the voltage windows of the two materials, broaden the voltage range of the overall material, and thus improve the energy density of the sodium-ion battery. At the same time, precise regulation of the weight ratio of the first component material within the range of 1% - 50% further ensures the stability and consistency of the material performance.

[0018] In terms of the manufacturing method, this application ensures the uniform distribution and tight combination of the first component material and the second component material through crushing, mixing, and sintering processes, thereby improving the overall performance and consistency of the cathode material. In particular, long-term (greater than 8 h) ball milling and mixing using a ball mill tank, and high-temperature (greater than 300 °C) sintering in an inert atmosphere, the optimization of these process parameters further enhances the crystallinity and electrochemical activity of the material. The sodium-ion battery containing the sodium-ion battery cathode material provided by this application shows advantages in terms of energy density, cycle stability, and safety, and is not only applicable to markets such as energy storage and automobiles, but also has the potential to be applied in a wider range of fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the discharge voltage platform curve graph of the battery cells formed by the materials of the examples and the comparative examples at a rate of 0.33C; Figure 2It is a result curve graph of the cycle test of the battery cells formed by the materials of the examples and comparative examples at a charge-discharge rate of 1C / 1C; Figure 3 It is a SEM image of the positive electrode material of the sodium-ion battery in a specific embodiment of the present application; Figure 4 It is a TEM image of the positive electrode material of the sodium-ion battery in a specific embodiment of the present application. Detailed Description of the Invention

[0020] To make the above objects, features, and advantages of the present application more obvious and understandable, the following will describe the specific embodiments of the present application in detail with reference to the accompanying drawings. It can be understood that the specific embodiments described herein are only for explaining the present application, rather than limiting the present application. Additionally, it should be noted that for the convenience of description, only the parts related to the present application are shown in the drawings, rather than all the structures. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present application.

[0021] The terms "include" and "have" in the present application and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products, or devices.

[0022] Referring to "embodiment" in this context means that a specific feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The phrase appearing at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0023] As the core component determining the performance of sodium-ion batteries, the research and optimization of positive electrode materials for sodium-ion batteries play a crucial role in improving the energy density, cycle stability, and safety of sodium-ion batteries. In recent years, although researchers have made a series of important progress in this field, such as the development of polyanionic sodium battery positive electrode materials and the application of coating technologies, there are still many challenges in existing sodium positive electrode materials, such as insufficient specific capacity, low voltage platform, and poor cycle performance. These disadvantages severely limit the commercialization process of sodium-ion batteries.

[0024] In order to overcome these technical difficulties, the present application proposes an innovative sodium ion battery positive electrode material and a method for manufacturing the same. The positive electrode material combines the advantages of different sodium ion positive electrode materials through component selection and structural layout to achieve a balanced improvement in material performance. At the same time, the present application also adopts an efficient and controllable manufacturing method to ensure the uniformity and consistency of the positive electrode material, thereby further improving the overall performance of the sodium ion battery. Next, the composition, structural characteristics, manufacturing method and application effect of the sodium ion battery positive electrode material provided by the present application will be introduced in detail. The sodium ion battery positive electrode material in a preferred embodiment of the present application includes a first component material and a second component material, wherein the first component material is a polyanion material, the second component material is a polyanion material, and the discharge platform voltage of the first component material is greater than the discharge platform voltage of the second component material, wherein the first component material is coated on the surface of the second component material, or the second component material is coated on the surface of the first component material. The discharge platform voltage referred to in this application refers to the cut-off voltage of 1.5V after charging to 4V at 0.33C within the voltage range of 1.5~4V, and discharging to 1.5V with a current of 0.33C. The ratio of the total discharge energy to the total discharge capacity is defined as the discharge platform voltage, and is obtained by testing a battery cell manufactured with the above-mentioned positive electrode material as the positive electrode and hard carbon as the negative electrode.

[0025] The sodium ion battery positive electrode material of the present application combines the first component material and the second component material, and the two work synergistically to jointly improve the comprehensive performance of the material. Specifically, the first component material uses a high-performance polyanion material, and the second component material can choose a polyanion-type material. These materials often have a high gram capacity and good cycle stability. What is more important is that this material forms a coating structure, that is, the first component material is coated on the surface of the second component material, or the second component material is coated on the surface of the first component material. This coating structure makes full use of the respective advantages of the two materials, and further improves the overall performance of the material through interface effects and interactions. Specifically, the coating layer can effectively protect the internal material from erosion by the external environment, such as preventing the intrusion of harmful substances such as moisture and oxygen, thereby extending the cycle life of the material. The coating layer can also play a role in regulating the transmission of ions and electrons and optimizing the charge and discharge performance of the battery.

[0026] In addition, this material also places special emphasis on the difference in discharge platform voltage between the first component material and the second component material. Specifically, the discharge platform voltage of the first component material is designed to be greater than the discharge platform voltage of the second component material. This design can broaden the voltage range of the positive electrode material, allowing the battery to operate in a wider voltage window. By precisely controlling the difference in discharge platform voltage between the two materials, the electrochemical performance of the battery can be further optimized, such as reducing polarization and improving charge and discharge efficiency.

[0027] Sodium polyanion cathode material with a low working voltage platform, the chemical general formula of which can be summarized as Na a M b (X c O d ) e Z f , where M is one or more of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ca, Mg, Al, Nb, etc.; X is C, Se, Si, S, P, As, B, Mo, W, Ge, etc.; Z is O, F, OH or blank, etc. The above list is only part of the materials, and any polyanion material that meets the above requirements can be applied in the technical solution of this application.

[0028] Specifically, the discharge platform voltage of the first component material is greater than or equal to 3V. The energy density of the battery is directly related to its working voltage. The first component material has a relatively high discharge platform voltage (≥3V). At the same charge amount, the battery can output a higher voltage, thereby increasing the energy density of the entire battery system, which is crucial for meeting the requirements of new energy vehicles and energy storage systems for high energy density. By setting the discharge platform voltage of the first component material to be greater than or equal to 3V, the positive electrode material can work stably within a wider voltage range. This is beneficial to the performance stability of the battery during charge and discharge, can reduce the battery aging problem caused by voltage fluctuations, and extend the service life of the battery. The first component material with a high discharge platform voltage can more effectively promote the sodium ion insertion and extraction process, thereby improving the electrochemical performance of the battery, enhancing the charge and discharge efficiency of the battery, reducing the polarization phenomenon, and improving the cycle stability of the battery, etc.

[0029] Specifically, the difference between the discharge platform voltage of the first component material and the discharge platform voltage of the second component material is in the range of 0.1 - 1.6V. By regulating the difference in the discharge platform voltages of the two component materials, the positive electrode material can work stably within a wider voltage range, which helps to improve the energy output ability of the battery. At the same time, it reduces the polarization phenomenon during the charge and discharge process of the battery and improves the overall performance of the battery. On the premise of maintaining the battery safety, an appropriate voltage difference can enable the battery to more effectively utilize sodium ions during charge and discharge, thereby increasing the energy density and power density of the battery, which is of great significance for meeting the requirements of high-performance batteries in fields such as new energy vehicles and energy storage systems. By regulating the voltage difference, the first component material and the second component material can play their respective advantages during battery operation, forming a complementary effect, and this synergistic effect improves the overall performance of the battery.

[0030] Specifically, the weight proportion of the first component material ranges from 1% to 50%. By controlling the weight proportion of the first component material, the material cost can be effectively reduced while ensuring the battery performance. When the proportion of the first component material is too high, although it may bring performance improvement, it will deviate from the designed voltage; while when the proportion is too low, its performance advantages may not be fully utilized. Therefore, the proportion range of 1% - 50% is the best choice to achieve the balance between performance and cost. As a high-performance polyanion material, the regulation of the weight proportion of the first component material has an important impact on the electrochemical performance of the battery. Within the above range, it can ensure that the first component material fully exerts its advantages of high voltage and high stability, and at the same time forms a good synergistic effect with the second component material to jointly improve the energy density, cycle stability and safety of the battery. The weight proportion of the first component material has an important impact on the cycle life of the battery, and can ensure that the first component material maintains a stable structure and performance during the battery cycle.

[0031] Specifically, the thickness of the component material coated on the outer layer is 30nm - 2000nm. In the specific implementation, the first component material can be used as a high-performance polyanion material, and its outer layer coating design can more effectively utilize the characteristics of the material, such as high voltage, high stability, etc., so as to improve the energy density and power density of the battery. The above thickness range ensures that the material can stably intercalate and deintercalate sodium ions during the charge and discharge process of the battery, reduce the polarization phenomenon, and improve the charge and discharge efficiency of the battery. The first component material coated on the outer layer can effectively protect the internal material from the erosion of the external environment, such as preventing the intrusion of harmful substances such as moisture and oxygen, thereby extending the service life of the battery. In addition, the first component material within this thickness range can form a stable solid electrolyte interface (SEI), reduce the capacity attenuation of the battery during the cycle, and improve the cycle stability of the battery. The morphology and structure of the material can be specifically referred to Figure 3 、 Figure 4 , and the material of the present application forms a stable coating layer, in which the grain size of the material formed in the outer coating layer is smaller than that included in the internal material (the second component).

[0032] Specifically, the first component material is Na a M b (X c O d ) e Z f , where M is selected from one or more of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ca, Mg, Al, and Nb, X is selected from one or more of C, Se, Si, S, P, As, B, Mo, W, and Ge, and Z is selected from O, F, OH, or blank, etc.

[0033] The present application further provides a method for manufacturing a cathode material for a sodium-ion battery, comprising: determining a first component material and a second component material, wherein the discharge platform voltage of the first component material is greater than that of the second component material; respectively weighing the first component material and the second component material, and performing pulverization and mixing; after pulverization and mixing, sintering the mixed material under an inert atmosphere.

[0034] In the manufacturing method of the present application, first, the first component material and the second component material are clearly defined and selected. The selection of these two materials is crucial, and it is necessary to ensure that the discharge platform voltage of the first component material is higher than that of the second component material. Subsequently, the required amounts of the first component material and the second component material are accurately weighed respectively and pulverized. The purpose of pulverization is to reduce the particle size of the material and increase its specific surface area, thereby improving the reaction activity and electrochemical performance of the material. Then, the two pulverized materials are fully mixed to ensure a uniform structure can be formed during the subsequent sintering process. The mixed material is placed in an inert atmosphere (such as nitrogen, argon, etc.) for sintering. This step is the core link in the manufacturing process. By controlling the sintering temperature, time, and atmosphere conditions, the microstructure and electrochemical performance of the material can be optimized. The processes of pulverization and mixing and sintering under an inert atmosphere contribute to forming a coated material structure, reducing pores and defects, improving the electrical conductivity and ion diffusion rate of the material, and thus improving the electrochemical performance of the battery.

[0035] Specifically, a ball milling tank is used to perform pulverization and mixing by ball milling. During the ball milling process, ball milling media with high hardness and wear resistance (such as cemented carbide balls, ceramic balls, etc.) are selected to impact and grind the first component material and the second component material. At the same time, by adjusting parameters such as the quantity, size, rotation speed, and ball milling time of the ball milling media, the pulverization degree and mixing uniformity of the material can be accurately controlled. In addition, to further improve the mixing effect, an appropriate amount of grinding aid or dispersant can be added during the ball milling process to promote the uniform dispersion between the material particles. The ball milling process uses mechanical energy to efficiently pulverize the material, which can quickly refine large particles of the material into tiny particles, thereby increasing the specific surface area of the material and improving its reaction activity. Through the mixing by ball milling, it can be ensured that the first component material and the second component material are uniformly distributed at the microscale, avoiding the phenomenon of excessive or too low local concentration.

[0036] Specifically, the duration of ball milling is greater than 8 h, and the sintering temperature is greater than 300 °C. During the ball milling process, the long-term ball milling for more than 8 hours not only ensures that the material particles are fully refined, but also promotes the uniform mixing between the particles. By continuously applying mechanical force, the structural stability and reactivity of the material are improved. At the same time, the long-term ball milling also helps to eliminate the pores and cracks in the material, further enhancing the density and conductivity of the material. In the sintering stage, the sintering temperature higher than 300 °C ensures that the chemical reaction between the material particles proceeds fully, forming stable chemical bonds and a coated microstructure. In addition, high-temperature sintering also helps to remove the volatile components and impurities in the material, improving the purity and electrochemical performance of the material.

[0037] Specifically, by selecting the first component material and the second component material with different particle sizes, mutual coating of the first component material and the second component material is achieved, and the particle size of the material coating layer is less than 1 / 10 of the particle size of the inner layer material.

[0038] This application also provides a sodium-ion battery, including the aforementioned positive electrode material for sodium-ion battery. By adopting the aforementioned positive electrode material, through processes such as long-term ball milling and high-temperature sintering, the refinement of material particles, uniform mixing, and densification of the structure are achieved, forming a coated structure, which can improve the electrochemical performance of the battery. Specific embodiments The following will further introduce some specific implementation manners to further elaborate on the technical solutions of this application.

[0040] The high-voltage platform positive electrode material Na2Fe2(SO4)3 and the low-voltage platform positive electrode material Na4Fe3(PO4)2P2O7 (the mass ratios of Na2Fe2(SO4)3 are 1%, 5%, 10%, 20%, and 50% respectively) are selected and put into a ball milling tank for ball milling, and the ball-milled samples are sintered in an inert atmosphere at 350 °C. The above samples are respectively named as Examples 1-5, and the above materials are assembled into button cells to test their discharge specific capacities, as shown in Table 1.

[0041] Table 1 Specific composition methods and test results of different examples Further, the materials sintered in Example 2 and Example 3 are selected as the positive electrode, and hard carbon is used as the negative electrode to make a battery cell and test its discharge voltage platform at a 0.33C rate, as shown in Table 2 and Figure 1 . When the mass ratio of Component 1 reaches 5%, the platform voltage of Example 2 increases significantly (2.85 V → 2.92 V). With the increase of the mass ratio of Component 1, the discharge platform voltage is further improved. Figure 1 is the discharge curve at 0.33C, and it can also be seen that the discharge voltage platform gradually moves up with the increase of the mass ratio of Component 1.

[0042] Table 2 Discharge platform voltage test results of Example 2 and Example 3 From the above test results, it can be found that in the embodiments of the present application, as the content of the high-voltage platform material increases, the voltage platform of the composite material gradually increases, indicating that the technical solution of the present application makes full use of the advantage of the higher voltage platform of sodium iron sulfate and improves the voltage platform of sodium iron pyrophosphate by coating, thereby increasing the energy density.

[0043] Cycling is a very critical performance index for batteries. In addition to verifying the improvement of the voltage platform through testing, the cycling performance was further verified and compared. At room temperature, cycling was carried out at a charge-discharge rate of 1C / 1C, and the test results are shown in Table 3 and Figure 2 . From the results of 400 cycles, as the proportion of Component 1 increases, the cycling performance can still maintain the same level without significant changes.

[0044] Table 3 Cycling test results of Example 2 and Example 3 To further confirm the improvement effect brought by material coating, the sintered material of Example 2 was selected for microscopic characterization at the material level, such as Figure 3 and Figure 4 . The small-particle material is coated on the surface of the large-particle material, and obvious particle-level differences can be seen from the TEM image.

[0045] At the same time, two groups of high-voltage platform cathode materials Na3V2(PO4)3 and low-voltage platform cathode materials Na4Fe3(PO4)2P2O7, as well as high-voltage platform materials Na4MnV(PO4)3 and low-voltage platform cathode materials Na4Fe3(PO4)2P2O7 were selected, and two groups of composite materials with a mass ratio of Na3V2(PO4)3 of 20% and 40% were obtained respectively by the above similar ball milling + high-temperature sintering process, which were labeled as Example 6 and Example 7; composite materials with a mass ratio of Na4MnV(PO4)3 of 20% and 40% were obtained respectively, which were labeled as Example 8 and Example 9; it can be seen from the test results in Table 4 that the voltage platform of the composite material has been significantly improved by adding the high-voltage platform material.

[0046] Table 4 0.33C discharge platform voltage test results of Examples 6 - 9 As can be seen from the above, the present application proposes an innovative cathode material for sodium-ion batteries, its manufacturing method, and a sodium-ion battery using this cathode material. The cathode material consists of a first component material and a second component material, where the first component material is a high-performance polyanion material with a discharge platform voltage higher than that of the second component material, and the second component material is a polyanion material. The two materials are combined through a coating structure, that is, the first component material coats the surface of the second component material, or vice versa. This structure makes full use of the advantages of both, and through the interface effect and interaction, improves the overall performance of the material.

[0047] Specifically, the high discharge platform voltage (≥3V) of the first component material broadens the voltage range of the cathode material, enabling the battery to operate stably within a wider voltage window, and improving the energy density and power density of the battery. At the same time, by adjusting the difference in the discharge platform voltages of the two component materials (within the range of 0.1 - 1.6V), the electrochemical performance of the battery is further optimized, such as reducing polarization and improving charge-discharge efficiency. In addition, the weight ratio of the first component material (within the range of 1% - 50%) is adjusted to achieve a balance between performance and cost, ensuring the high performance and economy of the battery.

[0048] In terms of the manufacturing method, the present application adopts the processes of long-time ball milling (>8h) and high-temperature sintering (>300°C). By controlling parameters such as the quantity, size, rotation speed of the ball milling medium, and the sintering temperature and time, the refinement of material particles, uniform mixing, and dense structure are achieved, forming a stable coating structure and further improving the electrochemical performance of the material.

[0049] The example data shows that the sodium-ion battery made of the cathode material of the present application performs excellently in terms of discharge specific capacity and platform voltage. In particular, the increase in the platform voltage proves the effectiveness and innovation of the technical solution of the present application. By making full use of the high voltage platform of the first component material and the good cycle stability of the second component material, the cathode material of the present application not only improves the energy density and cycle stability of the battery, but also reduces the polarization phenomenon and enhances the overall performance of the battery.

[0050] The above is only a specific implementation manner of the present application. Any improvement made on the premise of the concept of the present application is regarded as the protection scope of the present application.

Claims

1. A cathode material for a sodium-ion battery, characterized in that, It includes a first component material and a second component material; The first component material is a polyanionic material, the second component material is a polyanionic material, and the discharge platform voltage of the first component material is greater than that of the second component material; Wherein, the first component material is coated on the surface of the second component material, or the second component material is coated on the surface of the first component material.

2. The cathode material for a sodium-ion battery according to claim 1, wherein The discharge platform voltage of the first component material is greater than or equal to 3V.

3. The cathode material for sodium-ion battery according to claim 2, characterized in that, The difference between the discharge platform voltage of the first component material and that of the second component material is in the range of 0.1V - 1.6V.

4. The cathode material for a sodium ion battery according to claim 1, characterized in that, The weight ratio of the first component material is in the range of 1% - 50%.

5. The cathode material for a sodium-ion battery according to claim 1, wherein The thickness of the component material coated on the outer layer is in the range of 30nm - 2000nm.

6. The cathode material for a sodium-ion battery according to claim 1, wherein The first component material is Na a M b (X c O d ) e Z f , where M is selected from one or more of Ti, V, Cr, Cu, Mn, Fe, Co, Ni, Ca, Mg, Al, and Nb, X is selected from one or more of C, Se, Si, S, P, As, B, Mo, W, and Ge, and Z is selected from O, F, OH, or is blank.

7. A method for manufacturing a cathode material for a sodium-ion battery, characterized in that, It includes: Determine the first component material and the second component material, wherein the discharge platform voltage of the first component material is greater than that of the second component material; Weigh the first component material and the second component material respectively and carry out pulverization and mixing; After pulverization and mixing, sinter the mixed material under an inert atmosphere.

8. The manufacturing method of the positive electrode material for a sodium ion battery according to claim 7, characterized in that, Use a ball milling tank to carry out pulverization and mixing by ball milling.

9. The manufacturing method of the positive electrode material of a sodium ion battery according to claim 8, characterized in that, The duration of ball milling is greater than 8h, and the sintering temperature is greater than 300°C.

10. The manufacturing method of the positive electrode material for a sodium ion battery according to claim 7, characterized in that By selecting first component materials and second component materials with different particle sizes, mutual coating of the first component material and the second component material is achieved, and the particle size of the material coating layer is less than 1 / 10 of the particle size of the inner layer material.

11. A sodium-ion battery, characterized in that, It includes the positive electrode material for a sodium ion battery according to any one of claims 1 - 6.

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