Sodium transition metal oxide positive electrode material containing glass-ceramic structure and method for producing same

Abstract

The application discloses a sodium transition metal oxide positive electrode material containing a glass ceramic structure, a preparation method and a sodium ion battery. x Mn a O 2­­ ·(M b O2) ­­ ·(U c O 2 ); wherein M is a ceramic-forming element, the compound of the ceramic-forming element has a melting point greater than or equal to 1000 DEG C, U is a glass-forming element, the compound of the glass-forming element has a melting point less than 1000 DEG C; 0.5<=x<=0.7, a>0, b>0, c>0, a+b+c=1. The sodium transition metal oxide positive electrode material forms a partially interstitial type blended doped glass ceramic structure, the design of a sodium-deficient phase increases the migration channel of Na elements, the design of an interfacial micro-melting blended doped shell core enables the material to obtain more redox active sites, and guarantees that the sodium-deficient phase material still has a relatively high specific capacity; meanwhile, the design of the interfacial micro-melting sodium-deficient phase inhibits the generation of alkaline impurities, and significantly improves the water resistance of the material.

Description

Technical Field

[0001] This application relates to the field of sodium-ion battery technology, specifically to a sodium transition metal oxide cathode material with a glass-ceramic structure, its preparation method, and a sodium-ion battery. Background Technology

[0002] Layered transition metal oxide cathode materials for sodium-ion batteries, with their core advantages of high specific capacity, wide availability of raw materials, and excellent rate performance, coupled with mature preparation and processing technologies and simple manufacturing processes, have become one of the most industrially valuable cathode materials in the sodium-ion battery field. Specific capacity is one of the core indicators for evaluating the electrochemical performance of sodium-ion battery cathode materials, directly determining the battery's energy density and suitability for various application scenarios. To increase the specific capacity of materials, previous extensive research has mainly focused on sodium-rich phase materials. However, sodium-rich phase materials have significant drawbacks: First, the high alkali residue content of sodium-rich phases leads to extremely high water absorption, easily absorbing moisture from the air. This not only causes the material's own moisture content to exceed the standard but also leads to problems such as uneven dispersion and poor system stability in subsequent homogenization processes, increasing the difficulty of production process control. Second, the chemical stability of sodium-rich phase materials decreases after water absorption, making them more prone to decomposition reactions, directly affecting the material's storage life and electrochemical performance stability, thus limiting its large-scale application.

[0003] Compared to sodium-rich phases, sodium-deficient phases, although having low alkali traces, can effectively suppress water absorption and decomposition of materials, solving the industrialization pain points of sodium-rich phases such as difficulty in homogenization and poor storage stability caused by water absorption. However, they face an unavoidable core technical bottleneck in the high-temperature synthesis process—the difficulty in achieving uniform fusion and stable molding of various components during synthesis, which easily leads to phase separation. This results in relatively low capacity of sodium-deficient phase materials and difficulty in synthesis, which is also the core difficulty in the large-scale preparation of sodium-deficient phase materials. Summary of the Invention

[0004] This application provides a sodium transition metal oxide cathode material with a sodium-deficient phase manganese based and a glass-ceramic structure, prepared by interfacial micro-melting sintering, a method for its preparation, and a sodium-ion battery.

[0005] Based on glass-ceramic forming technology, the manganese-based sodium transition metal oxide cathode material of this application innovatively adopts interfacial micro-melting sintering technology, which breaks through the bottleneck of traditional processes and achieves multi-dimensional optimization of material properties. The specific technical advantages and mechanisms of action are as follows: Glass-ceramic molding is the core process for preparing glass-ceramic materials. By precisely controlling parameters such as temperature and pressure, glassy precursors are transformed into composite functional materials that combine the melting properties of glass with the high strength of ceramics. Its core process typically includes three main steps: raw material melting, molding and shaping, and nucleation and crystallization. In particular, the surface glass melting technology for crystal nuclei can effectively reduce the melting temperature of doped auxiliary materials and suppress the loss of volatile materials. This technology allows for precise customization of the material's size, shape, and microstructure, effectively enabling the efficient fabrication of complex, irregularly shaped components.

[0006] First, this technology completely eliminates the complex precursor preparation process of traditional manufacturing processes. It induces the formation of a glassy molten layer on the material surface by introducing glassy elements (such as Li, K, B, and Si). The formation of this glassy molten layer significantly enhances the kinetic migration ability of dopants, creating favorable conditions for the introduction of ceramic dopants (such as Fe, Cu, Al, and Ti)—allowing these elements, which are normally difficult to integrate into the crystal structure, to stably sinter into the material lattice with the assistance of the molten interface. This simplification of the process not only reduces production complexity but also enables low-cost material preparation, while ensuring high uniformity of the product's crystal structure, laying the foundation for large-scale production.

[0007] Secondly, the synergistic doping of ceramic and glass-forming elements enables the cathode material to form a unique partially interstitial blended glass-ceramic structure. This structure can regulate the regional initial valence state distribution of manganese, inducing the formation of... and The material exhibits a multi-layered, cross-distributed valence state pattern. This valence state distribution characteristic provides the material with more redox active sites, effectively improving the material's reversible capacity and overcoming the performance bottleneck of insufficient capacity in traditional manganese-based materials.

[0008] Furthermore, the application of interfacial micro-melting sintering technology has made it possible to design sodium-deficient phases in manganese-based sodium transition metal oxide cathode materials. Sodium-deficient phase structures can be used to create more diverse... The migration channels accelerate the insertion, extraction, and transport of sodium ions, thus endowing the material with superior rate performance. Simultaneously, the sodium-deficient phase design effectively reduces alkali residue in the sintered material, prevents water absorption, and significantly increases the material's stability in air. This characteristic significantly improves the material's storage life and cycle stability, avoiding electrochemical performance degradation caused by water absorption, and providing a crucial guarantee for the long-term reliable application of sodium-ion batteries.

[0009] In summary, this application, through the innovative application of interfacial micro-melting sintering technology, significantly improves the reversible specific capacity of manganese-based sodium transition metal oxide cathode materials while simultaneously enhancing the material's air stability, cycle stability, and rate performance. This greatly broadens the preparation path and application scenarios of sodium-ion battery cathode materials, providing key technical support for the industrialization of high-performance sodium-ion batteries.

[0010] In a first aspect, this application provides a sodium transition metal oxide cathode material with a sodium-deficient manganese-based structure containing a glass-ceramic structure, which is sintered via interfacial micro-melting. The general formula of the sodium transition metal oxide with a sodium-deficient manganese-based structure containing a glass-ceramic structure in the interfacial micro-melting sintering of the cathode material is Na. x Mn a O2·(M b O2)·(U c O2); where 0.5≤x≤0.7, a>0, b>0, c>0, a+b+c=1; Na x Mn a O2 is the inner layer structure of the sodium transition metal oxide cathode material, (M b O2) and (U c O2) is the outer layer structure of the sodium transition metal oxide cathode material, and M is a ceramic element, the melting point of the compound of the ceramic element is greater than or equal to 1000℃, and U is a glass-forming element, the melting point of the compound of the glass-forming element is less than 1000℃. Secondly, this application provides a method for preparing a sodium transition metal oxide cathode material with a sodium-deficient phase manganese based on a glass-ceramic structure via interfacial micro-melting sintering, comprising the following steps: According to stoichiometric ratios, sodium-containing compounds, manganese-containing compounds, M-containing compounds, and U-containing compounds are mixed, ball-milled, refined, pressed into sheets, and sintered to obtain a sodium-transition metal oxide cathode material with a sodium-deficient phase manganese based and a glass-ceramic structure, characterized by interfacial micro-melting sintering. The sintering conditions are as follows: first, isothermal sintering at 400–600℃ for 5–12 h; then, heating to 800–850℃ and isothermal sintering for 5–12 h; finally, heating to 900–1000℃ and isothermal sintering for 2–8 h. The sintering atmosphere is oxygen, air, or a mixture of oxygen and air.

[0011] Thirdly, this application provides a sodium-ion battery, including a positive electrode material, wherein the positive electrode material comprises a sodium transition metal oxide positive electrode material with a sodium-deficient phase manganese based on a glass-ceramic structure and interfacial micro-melting sintering as described in the first aspect above, or a sodium transition metal oxide positive electrode material with a sodium-deficient phase manganese based on a glass-ceramic structure and interfacial micro-melting sintering as described in the second aspect above.

[0012] The method for preparing sodium transition metal oxide cathode materials with sodium-deficient phase manganese and glass ceramic structure by interfacial micro-melting sintering provided in this application is a simple one-step preparation method through interfacial micro-melting design. It has the advantages of inexpensive and readily available raw materials and simple preparation process. The obtained sodium transition metal oxide cathode material with sodium-deficient phase manganese and glass ceramic structure by interfacial micro-melting sintering has complete crystal form and high purity.

[0013] The sodium-ion battery provided in this application utilizes a sodium transition metal oxide cathode material with a sodium-deficient phase manganese based on a glass-ceramic structure, formed by interfacial micro-melting sintering, as the cathode material. The material has a typical core-shell protection structure, with a large manganese-based particle material as the core and a sodium-deficient phase (P2, P3 phase or mixed phase) doped with multiple elements on the surface as the capacity layer. While possessing a high specific capacity, the material stability is enhanced. The specific capacity and cycle stability of the sodium-ion battery are significantly improved.

[0014] The technical effects of this application are as follows: Focusing on the core technical challenges in the preparation of sodium battery cathode materials, this research has overcome key industry difficulties such as doping with difficult-to-dopant elements, sintering of sodium-deficient phases, and preparation of core-shell structures through innovative technical path design. This has resulted in a core technology system that combines technological advancement with industrial feasibility, as detailed below: Firstly, it addresses the challenge of doping ceramic elements in cathode materials, achieving highly efficient doping.

[0015] Due to their high melting points, ceramic-forming elements face technical bottlenecks in room-temperature synthesis systems, including difficulty in doping and uneven doping, which severely restricts the optimization of the crystal structure and performance improvement of cathode materials. This technology innovatively introduces glass-forming elements, which can construct a stable molten environment at the interface during material sintering. This molten environment provides an excellent diffusion and reaction carrier for the doping of ceramic-forming elements, enabling these elements, which are previously difficult to dope, to rapidly penetrate and uniformly incorporate into the crystal structure in a molten state. This effectively overcomes the doping limitations of room-temperature synthesis methods, significantly improving the efficiency and uniformity of element doping, and laying a core foundation for optimizing material performance.

[0016] Secondly, it achieved the technical effect of stable sintering of sodium-deficient phase cathode materials.

[0017] Sodium-deficient cathode materials are prone to incomplete sintering and phase separation during high-temperature sintering due to the low content of molten sodium source, resulting in poor material structural stability and severe degradation of electrochemical performance. To address this issue, this technology introduces glass-forming elements to construct a molten system. This system effectively locks in the sodium source at high temperatures, reducing sodium volatilization and loss, thus ensuring the stability of the sintering process. This completely solves the industry-wide problems of difficult sintering and phase separation in sodium-deficient materials, improving the sintering quality and structural integrity of the material. Simultaneously, the sodium-deficient phase design effectively reduces alkali residue in the sintered material, prevents water absorption, and significantly increases the material's stability in air. This characteristic significantly improves the material's storage life and cycle stability, avoiding electrochemical performance degradation caused by water absorption, providing a crucial guarantee for the long-term reliable application of sodium-ion batteries.

[0018] Thirdly, to achieve a low-cost gradient shell-core structure.

[0019] Traditional core-shell cathode materials are mostly prepared using solution co-precipitation methods, which suffer from drawbacks such as complex processes, harsh reaction conditions, and high production costs, making it difficult to meet the needs of large-scale industrial applications. This technology abandons the traditional process route, using a high-melting-point manganese source as the crystal nucleus to form a stable internal manganese-based core structure. Externally, multi-element doping creates a molten environment that effectively promotes efficient exchange and precise doping of elements between the inner and outer layers, naturally forming a gradient-distributed core-shell structure. The inner manganese-based core provides excellent cycle stability, while the outer multi-element doped structure significantly improves the material's specific capacity, achieving dual optimization of capacity and cycle performance.

[0020] The technical advantages of this application are: The process is simplified, the materials are of high performance, and the production cost is reduced. This application achieves comprehensive optimization of the preparation and performance of cathode materials through the innovative application of interfacial micro-melting sintering technology. Its core advantages are reflected in three aspects: 1. The preparation process is greatly simplified: The one-step mixing-sintering method is adopted, which eliminates the need for complex precursor synthesis and secondary coating treatment. The raw materials are cheap and readily available, and the operation process is simple, which greatly reduces the equipment investment and process control difficulty in the production process.

[0021] 2. Significantly improved overall material performance: The prepared cathode material has complete crystal structure and high purity, and has both typical core-shell protection structure and glass-ceramic properties. The manganese-based core ensures cycle stability, and the multi-doped sodium-deficient phase capacity layer provides high reversible specific capacity and abundant sodium migration channels. The final sodium-ion battery has achieved significant improvements in specific capacity, cycle stability and rate performance.

[0022] 3. Highly adaptable to industrialization: The process route is simple and controllable, with low production costs. It also fundamentally solves common industry problems such as phase separation and sodium source control contradictions in traditional processes. The prepared materials have stable performance and high batch consistency, which fully meets the needs of large-scale industrial production.

[0023] In summary, this application addresses three core pain points in the traditional preparation process of sodium-ion battery cathode materials: sintering phase separation, performance imbalance, and process complexity. It innovatively utilizes an interface micro-melting sintering technology to design a sodium-deficient manganese-based sodium transition metal oxide cathode material with a glass-ceramic structure, constructing a gradient shell-core structure preparation system of "manganese-based core - sodium-deficient capacity shell." This gradient shell-core structure achieves synergistic optimization of material performance: the inner manganese-based core, with its stable crystal structure, provides excellent cycle stability, fundamentally solving the problem of structural collapse during the charge and discharge process of manganese-based materials; the outer multi-element doped sodium-deficient phase serves as the capacity layer, retaining high specific capacity characteristics while constructing abundant sodium ion migration channels, achieving a dual improvement in specific capacity and rate performance. Through precise process control and elemental synergistic design, multiple goals are achieved: simplified material preparation process, improved overall performance, and reduced production costs. This completely resolves the inherent contradiction between sodium source control and material performance in traditional processes, providing core technological support for the large-scale industrial application of high-performance sodium battery cathode materials.

[0024] To more clearly demonstrate the technical means of this application and to ensure the smooth implementation of the contents of the specification, some typical embodiments of this application will be listed below, along with accompanying drawings and detailed descriptions. Attached Figure Description

[0025] Figure 1 The XRD patterns of sodium-deficient manganese-based sodium transition metal oxides with glass-ceramic structure prepared by interfacial micro-melting sintering in Examples 1-8 of this application and the manganese-based sodium transition metal oxides sintered by conventional methods in Comparative Examples 1 and 2 are shown. Figure 2 The image shows the SEM image of the electrode prepared by the sodium-deficient phase manganese-based sodium transition metal oxide with glass ceramic structure prepared by the interfacial micro-melting sintering in Example 1 of this application after standing for 24 hours. Figure 3 The diagram shows the first charge-discharge curves at 2.0~4.3V and 0.1C for the sodium-deficient manganese-based sodium transition metal oxide with a glass-ceramic structure prepared by interfacial micro-melting sintering in Example 1 of this application and the manganese-based sodium transition metal oxide sintered by conventional method in Comparative Example 2. Figure 4 The graph shows the performance of the sodium-deficient manganese-based sodium transition metal oxide with a glass-ceramic structure prepared by interfacial micro-melting sintering in Example 1 of this application and the manganese-based sodium transition metal oxide sintered by conventional method in Comparative Example 2 at different rate magnifications of 2.0~4.3V. Figure 5This is a schematic diagram of the long-cycle conditions at 2.0~4.3V and 0.5C for the sodium-deficient phase manganese-based sodium transition metal oxide with glass-ceramic structure prepared by interfacial micro-melting sintering in Example 1 of this application and the manganese-based sodium transition metal oxide sintered by conventional method in Comparative Example 2. Detailed Implementation

[0026] To make the inventive objectives and technical solutions of this application clearer and easier to understand, the following detailed description of this application is provided in conjunction with the accompanying drawings and embodiments. However, it should be understood that the specific embodiments described herein are only for explaining this application and are not intended to limit this application. Modifications and substitutions made to the methods, preparation steps, or conditions of this application without departing from the spirit and substance of this application are all within the scope of this application.

[0027] This application provides a sodium transition metal oxide cathode material with a sodium-deficient manganese-based structure and a glass-ceramic structure, which is sintered via interfacial micro-melting. The sodium transition metal oxide with a sodium-deficient manganese-based structure and a glass-ceramic structure, which is sintered via interfacial micro-melting, has the following general formula: Na x Mn a O2·(M b O2)·(U c O2); Among them, 0.5≤x≤0.7, a>0, b>0, c>0, a+b+c=1, for example: x is 0.5, 0.6, 0.7, etc.; a is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, etc.; b is 0.1, 0.2, 0.3, 0.4, etc.; c is 0.1, 0.2, 0.3, 0.4, etc.

[0028] Specifically, Na x Mn a O2 is the inner layer structure of sodium transition metal oxide cathode materials, which allows for the use of a high-melting-point manganese source as a crystal nucleus, thereby enabling Na... x Mn a O2 forms a stable internal core manganese-based structure; (M b O2) and (U c O2) is the outer layer structure of sodium transition metal oxide cathode material. The outer layer structure relies on multi-element doping to form a molten environment. This molten environment can effectively promote the efficient exchange and precise doping of elements between the inner and outer layers, thereby forming a gradient-distributed shell-core structure.

[0029] Wherein, M is a ceramic-forming element, specifically, the melting point of the compound of the ceramic-forming element is greater than or equal to 1000℃; U is a glass-forming element, specifically, the melting point of the compound of the glass-forming element is less than 1000℃.

[0030] This application innovatively relies on glass-ceramic melting and sintering technology, using high-melting-point manganese-based large-particle materials as the core matrix. By leveraging the unique technical characteristics of glass melting, the sodium source is locked in at high temperatures, solving the difficulties of sodium source loss and volatilization during the material sintering process. At the same time, the doped auxiliary materials in the molten state are more likely to enter the structure and spontaneously form a gradient-distributed shell-core structure, successfully realizing the controllable sintering of multi-component sodium-deficient phase cathode materials, and breaking through the problems of sodium loss and phase separation in the preparation of such materials by traditional processes.

[0031] In some embodiments, Na x Mn a The particle size corresponding to O2 is greater than (M) b The particle size corresponding to O2; and / or, Na x Mn a The particle size corresponding to O2 is larger than (U c The particle size corresponding to O2).

[0032] Due to (M) b O2) and (U c O2) is the outer layer structure of sodium transition metal oxide cathode material, i.e. (M b O2) and (U c O2) is used to form the outer protective structure, Na x Mn a O2 is used to form crystal nuclei, therefore Na x Mn a The particle size corresponding to O2 is greater than (M) b O2) corresponding particle size and (U c The particle size corresponding to O2 is used to achieve the gradation of the elemental composition of the hard core, the ceramic part, and the glassy part.

[0033] In some embodiments, the ceramic-forming element M is selected from one or more of Cu, Ca, Mg, Zn, Fe, Co, Al, La, Ti, Ni, or Zr, and the glass-forming element U is selected from one or more of Li, K, B, and Si.

[0034] In some embodiments, 0.55 ≤ x ≤ 0.65, 0.75 ≥ a ≥ 0.5, 0.25 ≥ b ≥ 0.05, and 0.2 ≥ c ≥ 0.05. For example, x can be 0.55, 0.6, 0.65, etc.; a can be 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, etc.; b can be 0.05, 0.1, 0.15, 0.2, 0.25, etc.; and c can be 0.05, 0.1, 0.15, 0.2, etc. By further controlling 0.55≤x≤0.65, 0.75≥a≥0.5, 0.25≥b≥0.05, and 0.2≥c≥0.05, ceramic elements that are originally difficult to dope can penetrate more quickly and be more uniformly doped into the crystal structure, improving the efficiency and uniformity of element doping. At the same time, it can further reduce the volatilization and loss of sodium, thereby ensuring the stability of the sintering process, preventing the cathode material from absorbing water, and greatly increasing the storage life and cycle stability of the cathode material.

[0035] In some embodiments, the characteristic is that x+c≥0.7. Since Na is also a glass-forming element, by controlling x+c≥0.7, the difficulties in sintering and phase separation of sodium-deficient phase materials can be effectively avoided, thereby enabling the core crystal form of the cathode material to exhibit a pure P2 structure or a mixed P2 and P3 structure, further improving the sintering quality and structural integrity of the material.

[0036] In some embodiments, the sodium transition metal oxide containing a glass-ceramic structure can be represented by at least one of the following general formulas: (1) Na 0.62 Mn 0.6 O2·(Ti 0.1 O2Ni 0.15 O2)·(K 0.05 O2Li 0.1 O2), its general formula can also be expressed as: [Na 0.62 Mn 0.6 ·(Ti 0.1 Ni 0.15 )·(K 0.05 Li 0.1 O2; (2) Na 0.6 Mn 0.55 O2·(La 0.15 O2Ni 0.15 O2)·(Li 0.15 O2), its general formula can also be expressed as: [Na 0.6 Mn 0.55 ·(La 0.15 Ni 0.15 )·(Li 0.15 O2; (3) Na 0.55 Mn 0.6 O2·(Ca 0.05 O2Ni 0.15 O2Zn 0.15 O2)(Si 0.05 O2), its general formula can also be expressed as: [Na 0.55 Mn 0.6 ·(Ca 0.05 Ni 0.15 Zn 0.15 (Si) 0.05 O2; (4) Na 0.6 Mn 0.5 O2·(Zr 0.1 O2Ni 0.2 O2Cu 0.1 O2)·(K 0.1 O2), its general formula can also be expressed as: [Na 0.6 Mn 0.5 ·(Zr 0.1 Ni 0.2 Cu 0.1 )·(K 0.1 O2; (5) Na 0.62 Mn 0.75 O2·(Fe 0.05 O2Ni 0.15 O2)·(Li 0.05 O2), its general formula can also be expressed as: [Na 0.62 Mn 0.75 ·(Fe 0.05 Ni 0.15 )·(Li 0.05 O2; (6) Na 0.62 Mn 0.65 O2·(Co 0.15 O2)·(Li 0.2 O2), its general formula can also be expressed as: [Na 0.62 Mn 0.65 ·(Co 0.15 )·(Li 0.2 O2; (7) Na 0.62 Mn 0.75 O2·(Al 0.15 O2)·(K 0.1 O2), its general formula can also be expressed as: [Na 0.62 Mn 0.75 ·(Al 0.15 )·(K 0.1 O2; (8) Na 0.65 Mn 0.75 O2·(Mg 0.1 O2)·(B 0.15 O2), its general formula can also be expressed as: [Na 0.65 Mn 0.75 ·(Mg 0.1 )·(B 0.15 )] O2.

[0037] like Figure 1 As shown, Figure 1 Therefore Example 1: Na 0.62 Mn 0.6 O2·(Ti 0.1 O2Ni 0.15 O2)·(K 0.05 O2Li 0.1 O2); Example 2: Na 0.6 Mn 0.55 O2·(La 0.15 O2Ni 0.15 O2)·(Li 0.15 O2); Example 3: Na 0.55 Mn 0.6 O2·(Ca 0.05 O2Ni 0.15 O2Zn 0.15 O2)(Si 0.05 O2); Example 4: Na 0.6 Mn 0.5 O2·(Zr 0.1 O2Ni 0.2 O2Cu 0.1 O2)·(K 0.1 O2); Example 5: Na 0.62 Mn 0.75 O2·(Fe 0.05 O2Ni 0.15 O2)·(Li 0.05 O2); Example 6: Na 0.62 Mn 0.65 O2·(Co 0.15 O2)·(Li 0.2 O2); Example 7: Na 0.62 Mn 0.75 O2·(Al 0.15 O2)·(K 0.1 O2); Example 8: Na 0.65 Mn 0.75 O2·(Mg 0.1 O2)·(B 0.15 O2); For example, in an XRD (X-ray diffraction) pattern, the horizontal axis is twice the incident angle (θ) of the X-rays (2θ, in degrees), and the vertical axis is the intensity after diffraction (au in the figure is short for absorption unit); according to Figure 1 It is known that the sodium-deficient manganese-based sodium transition metal oxides with glass-ceramic structure formed by interfacial micro-melting sintering have a core crystal form of pure P2 structure or a mixed P2 and P3 structure. While maintaining a high capacity, they can provide better material stability and have a smoother sodium ion insertion / extraction capability.

[0038] For the general modification of sodium-ion battery cathode materials, traditional methods for modifying and synthesizing sodium battery cathode materials often involve the preparation of co-precipitation precursors, dry mixing, or direct high-temperature processing. This process is not only cumbersome and energy-intensive, but also prone to sintering difficulties and crystal phase separation problems. Furthermore, there is an inherent contradiction in sodium source control—while a high sodium source can reduce phase separation, it will block sodium ion diffusion channels, leading to a decrease in capacity and rate performance; while a sodium-deficient phase can increase sodium migration channels, it will exacerbate sintering phase separation, resulting in unstable material structure and performance, which has become a technical bottleneck in the industry.

[0039] The core process of this application is: It uniquely adopts an innovative three-step sintering process with micro-melting interface design. Through precise temperature control of low-temperature molten layer formation, medium-temperature promotion of sodium source fusion, and high-temperature advancement of doping penetration, it completely solves the dual challenges of phase separation and sodium source control at the process level. The specific technical process is as follows: 1. Precise raw material formulation: using manganese-based large particle materials as the core layer (Mn a O2), according to stoichiometric ratio, the core layer raw materials and sodium source (Na) are mixed. x O2), multi-element doped phase (M b O2), interface micro-melting special glass phase formation (U c O2) mix evenly to form Na x Mn a O2·(M b O2)·(U c O2) composite precursors are used to achieve pre-dispersion homogenization of elements.

[0040] 2. Low-temperature sintering to form a molten coating layer: A low-temperature constant-temperature sintering process of 400~600℃ for 5~8 hours is employed, utilizing the low melting point characteristic of the glassy phase to form a glassy phase (U... cO2) forms a stable micro-molten state at the interface, while simultaneously driving the doped phase (M) b O2 is uniformly coated around the manganese-based core layer, forming a continuous and dense interfacial micro-molten coating layer, which lays the foundation for subsequent medium- and high-temperature sodium source fusion and doping.

[0041] 3. Medium-temperature sintering promotes sodium source fusion: Based on the higher melting temperature of sodium source compared to glassy phase, medium-temperature sintering is adopted to further fuse sodium source and interfacial micro-molten elements in a eutectic glassy state, thereby enhancing interfacial bonding and uniform element dispersion.

[0042] 4. High-temperature sintering promotes doping nucleation: After medium- and low-temperature sintering, high-temperature sintering is carried out. With the help of the high kinetic and thermodynamic characteristics of the molten environment, the doping elements, sodium source, and glassy phase elements are gradually penetrated into the manganese-based core layer lattice, achieving deep and uniform doping of elements. This fundamentally avoids the problem of crystal phase separation and promotes the fusion of the coating layer and the core layer to form a stable shell-core structure.

[0043] 5. Sodium-deficient phase multi-component doping adaptation: Leveraging the technological advantages of interfacial micro-melting, this process can be directly applied to the preparation of multi-component doped sodium-deficient phase materials. While avoiding phase separation, it forms a stable core-shell structure consisting of a manganese-based large-particle core and a multi-component doped sodium-deficient phase capacity layer, balancing structural stability and high capacity characteristics. Simultaneously, the sodium-deficient phase design effectively reduces alkali residue in the sintered material, prevents water absorption, and significantly increases the material's stability in air.

[0044] This application provides a method for preparing the above-mentioned glass-ceramic structured sodium transition metal oxide cathode material, which includes the following steps: According to stoichiometric ratios, sodium-containing compounds, manganese-containing compounds, M-containing compounds, and U-containing compounds are mixed, ball-milled, refined, pressed into tablets, and sintered. This yields a sodium-transition metal oxide cathode material with a glass-ceramic structure and a sodium-deficient manganese-based phase, characterized by interfacial micro-melting sintering.

[0045] The preparation method will be explained in detail below.

[0046] The sodium-containing compound involved in the raw materials may be at least one of sodium carbonate, sodium acetate, sodium bicarbonate, and sodium hydroxide; the manganese-containing compound may be at least one of manganese sulfoxide, manganese dioxide, manganese tetroxide, manganese hydroxide, manganese carbonate, and manganese oxalate; and the M-containing compound may be at least one of M-containing oxide, M-containing carbonate, M-containing oxalate, and M-containing hydroxide, where M represents one or more of Cu, Ca, Mg, Zn, Fe, Co, Al, La, Ti, Ni, or Zr; and the U-containing compound may be at least one of U-containing carbonate, U-containing hydroxide, and U-containing amorphous oxide, where U is selected from one or more of Li, K, B, and Si.

[0047] The manganese-containing compound has a particle size of 5-15 μm, and the M-containing and U-containing compounds have a particle size of 500 nm-5 μm, so as to achieve the sintering particle size distribution of the hard core part, the ceramic part, and the glass part.

[0048] In some embodiments, the manganese-containing compound is at least one of manganese compounds with a high melting point (e.g., greater than or equal to 1000°C), such as manganese sulfide or manganese tetroxide.

[0049] In some embodiments, the U-containing compound (glass-forming portion) is at least one of a low-melting-point (e.g., less than 1000°C) carbonate, hydroxide, or amorphous oxide to achieve optimal interfacial micro-melting during sintering.

[0050] In some embodiments, the sodium-containing compound may be at least one of sodium carbonate, sodium bicarbonate, and sodium hydroxide to achieve optimal interfacial micro-melting during sintering.

[0051] In some embodiments, the molar ratio of sodium in the sodium-containing compound: manganese in the manganese-containing compound: M in the M-containing compound: U in the U-containing compound is (0.55~0.65): (0.5~0.75): (0.05~0.25): (0~0.2). In some embodiments, when mixing sodium-containing compounds, manganese-containing compounds, M-containing compounds, and U-containing compounds, mechanical grinding can be used, or they can be made into a solution or turbid liquid, mixed and ultrasonically vibrated to form a slurry, and then dried, ball-milled, etc. The purpose of mixing is to make the sodium-containing compounds, manganese-containing compounds, M-containing compounds, and U-containing compounds uniformly mixed, so as to facilitate sintering into a sodium-deficient phase manganese-based sodium transition metal oxide cathode material with a glass ceramic structure containing interfacial micro-melting sintering.

[0052] In some embodiments, the sintering conditions are as follows: first, constant temperature sintering at 400-600°C for 5-12 hours; then, heating to 800-850°C and constant temperature sintering for 5-12 hours; finally, heating to 900-1000°C and constant temperature sintering for 2-8 hours; the sintering atmosphere is oxygen, air, or a mixture of oxygen and air. The method for preparing sodium transition metal oxide cathode materials with glass-ceramic structures provided in this application employs a three-step heating and calcination method, achieving ordered structural construction through precise temperature gradient control. First, the interfacial micro-melted glass-ceramic structure is constructed in a lower temperature range (400-600℃), laying a stable foundation for subsequent element doping and structural shaping. Then, the temperature is increased to a medium temperature range (800-850℃) to further fuse the sodium source and interfacial micro-melted elements in a glassy state, enhancing the interfacial melting effect and ensuring uniform element dispersion. Finally, the temperature is increased to a high temperature environment (900-1000℃) to further advance the kinetics and thermodynamics of the overall material synthesis, ultimately forming a stable core-shell structure with a hard manganese-based material as the core and a sodium-deficient phase as the shell. This design features readily available and inexpensive raw materials, a simple preparation process, and yields a sodium transition metal oxide cathode material with a sodium-deficient phase manganese and a glass-ceramic structure, exhibiting complete crystal structure and high purity.

[0053] Because the sodium-transition metal oxide cathode material with a sodium-deficient manganese-based structure containing a glass-ceramic structure, formed by interfacial micro-melting sintering, is used as the active material of the cathode, this cathode material has a typical core-shell energy structure. It uses layered transition metal oxides as the core (P2, P3 phases, or a mixture of phases) and a molten, sintered sodium-deficient phase as the energy layer. This results in high specific capacity while enhancing the stability of the core material. The sodium-ion battery made from this material shows significant improvements in specific capacity and cycle stability. Therefore, this application also provides cathode sheets and sodium-ion batteries using the sodium-deficient manganese-based cathode material with a glass-ceramic structure formed by interfacial micro-melting sintering.

[0054] The positive electrode uses sodium transition metal oxide positive electrode material with sodium-deficient phase manganese based on glass ceramic structure, which is sintered by interfacial micro-melting, as the positive electrode active material. It also contains conductive agent and binder.

[0055] Specifically, a sodium transition metal oxide cathode material with a sodium-deficient manganese-based structure and a glass-ceramic structure, which is sintered at the interface, is mixed with a conductive agent, a binder, and a solvent to form a cathode slurry. This slurry is then coated onto the surface of the cathode current collector, and subsequently dried, rolled, and cut into cathode sheets. The mass ratio of the sodium transition metal oxide cathode material with a sodium-deficient manganese-based structure and a glass-ceramic structure, the conductive agent, and the binder in the cathode sheet is 8:1:1. N-methylpyrrolidone (NMP) can be used as the solvent in preparing the cathode slurry.

[0056] Sodium-ion batteries include the above-mentioned positive electrode sheet, or the positive electrode material containing the sodium-deficient phase manganese-based sodium transition metal oxide positive electrode material with a glass-ceramic structure and interfacial micro-melting sintering according to the embodiments of this application.

[0057] In some embodiments of the present application, the core portion of the sodium-ion battery cathode material containing a sodium-deficient manganese-based sodium transition metal oxide with a glass-ceramic structure and micro-melting sintering at the interface can be at least one of P2 phase transition metal oxide, P3 phase transition metal oxide, and O3 phase transition metal oxide.

[0058] In some embodiments, the sodium-ion battery provided in this application uses metallic sodium as the negative electrode material and any one of the following electrolytes: 1M NaPF6 / (EC:DMC=1:1), 1M NaPF6 / PC, and 1M NaClO4 / (EC:PC=1:1), wherein EC represents ethylene carbonate, DMC represents dimethyl carbonate, PC represents propylene carbonate, EC:DMC=1:1 represents a solvent formed by ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1, and EC:PC represents a solvent formed by ethylene carbonate and propylene carbonate in a volume ratio of 1:1.

[0059] In some embodiments, the sodium-ion battery provided in this application uses a polyolefin microporous membrane such as polyethylene or polypropylene, or a Celgard membrane.

[0060] Example 1 A method for preparing a sodium transition metal oxide cathode material with a sodium-deficient phase manganese based and a glass-ceramic structure via interfacial micro-melting sintering includes the following steps: (a) Sodium carbonate, manganese tetroxide, titanium dioxide, nickel hydroxide, potassium hydroxide and lithium hydroxide were mixed in a molar ratio of 0.31:0.2:0.1:0.15:0.05:0.1 and added to a ball mill jar along with an equal weight of grinding beads. Ethanol was also added and added to the ball mill jar along with an equal weight of grinding beads. The mixture was ball milled at 200 r / min for 2 h. The mixed powder was then taken out, mixed evenly in a mortar, and dried in a vacuum drying oven.

[0061] (b) Press the powder mixed evenly in step (a) into a disc with a diameter of 20 mm on a cold press at a pressure of 100 MPa for 5 min.

[0062] (c) The pressed sheet mixture from step (b) was placed in a tube furnace and sintered at 500°C for 5 hours under a mixed atmosphere of oxygen and air (mixing ratio 2:8). The temperature was then increased to 850°C and sintered at that temperature for 5 hours. Finally, the temperature was increased to 1000°C and sintered at that temperature for 3 hours. The mixture was then allowed to cool naturally to room temperature to obtain sample 1, whose molecular formula is Na. 0.62 Mn 0.6 O2·(Ti 0.1 O2Ni 0.15 O2)·(K 0.05O2Li 0.1 O2).

[0063] Sample 1 was subjected to XRD and SEM (Scanning Electron Microscope) tests. For detailed test results, please refer to [link to relevant documentation]. Figure 1 and Figure 2 The cyclic performance is shown in Table 1.

[0064] Example 2 Referring to Example 1, sodium carbonate, manganese tetroxide, lanthanum trioxide, nickel hydroxide, and lithium carbonate were mixed in a molar ratio of 0.3:0.183:0.075:0.15:0.075, and added to a ball mill jar along with an equal weight of grinding beads. A portion of ethanol was also added. The mixture was ball-milled at 300 rpm for 8 hours. The resulting powder was dried, thoroughly mixed in a mortar, and then processed according to the methods described in (b)-(c) of Example 1. After pressing and sintering, a sodium transition metal oxide cathode material with a glass-ceramic structure and a sodium-deficient manganese-based structure, Na, was obtained. 0.6 Mn 0.55 O2·(La 0.15 O2Ni 0.15 O2)·(Li 0.15 O2), its XRD pattern is as follows Figure 1 As shown in Table 1, the cyclic performance is as follows.

[0065] Example 3 Referring to Example 1, sodium carbonate, manganese tetroxide, calcium oxide, nickel hydroxide, zinc oxide, and amorphous silicon dioxide were mixed in a molar ratio of 0.275:0.2:0.05:0.15:0.15:0.05, and added to a ball mill jar along with an equal weight of grinding beads. A portion of ethanol was also added. The mixture was ball-milled at 300 rpm for 8 hours. The resulting powder was dried, thoroughly mixed in a mortar, and then processed according to the methods described in (b)-(c) of Example 1. After pressing and sintering, a sodium transition metal oxide cathode material with a glass-ceramic structure and a sodium-deficient manganese-based structure, Na, was obtained. 0.55 Mn 0.6 O2·(Ca 0.05 O2Ni 0.15 O2Zn 0.15 O2)(Si 0.05 O2), its XRD pattern is as follows Figure 1 As shown in Table 1, the cyclic performance is as follows.

[0066] Example 4 Referring to Example 1, sodium carbonate, manganese tetroxide, zirconium dioxide, nickel hydroxide, copper oxide, and potassium hydroxide were mixed in a molar ratio of 0.3:0.167:0.1:0.2:0.1:0.1, and added to a ball mill jar along with an equal weight of grinding beads. A portion of ethanol was also added. The mixture was ball-milled at 300 rpm for 8 hours. The resulting powder was dried, thoroughly mixed in a mortar, and then processed according to the methods described in (b)-(c) of Example 1. After pressing and sintering, a sodium transition metal oxide cathode material with a glass-ceramic structure and a manganese-based, sodium-deficient phase, Na, was obtained. 0.6 Mn 0.5 O2·(Zr 0.1 O2Ni 0.2 O2Cu 0.1 O2)·(K 0.1 O2), its XRD pattern is as follows Figure 1 As shown in Table 1, the cyclic performance is as follows.

[0067] Example 5 Referring to Example 1, sodium carbonate, manganese tetroxide, ferric oxide, nickel hydroxide, and lithium carbonate were mixed in a molar ratio of 0.31:0.25:0.025:0.15:0.025 and added to a ball mill jar along with an equal weight of grinding beads. A portion of ethanol was also added. The mixture was ball-milled at 300 rpm for 8 hours. The resulting powder was dried, thoroughly mixed in a mortar, and then processed according to the methods described in (b)-(c) of Example 1. After pressing and sintering, a sodium transition metal oxide cathode material with a glass-ceramic structure and a manganese-based sodium-deficient phase, Na, was obtained. 0.62 Mn 0.75 O2·(Fe 0.05 O2Ni 0.15 O2)·(Li 0.05 O2), its XRD pattern is as follows Figure 1 As shown in Table 1, the cyclic performance is as follows.

[0068] Example 6 Referring to Example 1, sodium carbonate, manganese tetroxide, cobalt trioxide, and lithium hydroxide were mixed in a molar ratio of 0.31:0.217:0.075:0.2, and added to a ball mill jar along with an equal weight of grinding beads. A portion of ethanol was also added. The mixture was ball-milled at 300 rpm for 8 hours. The resulting powder was dried, thoroughly mixed in a mortar, and then processed according to the methods described in (b)-(c) of Example 1. After pressing and sintering, a sodium transition metal oxide cathode material with a glass-ceramic structure and a manganese-based, sodium-deficient phase, Na, was obtained. 0.62 Mn 0.65 O2·(Co0.15 O2)·(Li 0.2 O2), its XRD pattern is as follows Figure 1 As shown in Table 1, the cyclic performance is as follows.

[0069] Example 7 Referring to Example 1, sodium carbonate, manganese tetroxide, aluminum oxide, and potassium hydroxide were mixed in a molar ratio of 0.31:0.25:0.075:0.1, and added to a ball mill jar along with an equal weight of grinding beads. A portion of ethanol was also added. The mixture was ball-milled at 300 rpm for 8 hours. The resulting powder was dried, thoroughly mixed in a mortar, and then processed according to the methods described in (b)-(c) of Example 1. After pressing and sintering, a sodium transition metal oxide cathode material with a glass-ceramic structure and a manganese-based sodium-deficient phase, Na, was obtained. 0.62 Mn 0.75 O2·(Al 0.15 O2)·(K 0.1 O2), its XRD pattern is as follows Figure 1 As shown in Table 1, the cyclic performance is as follows.

[0070] Example 8 Referring to Example 1, sodium carbonate, manganese tetroxide, magnesium oxide, and boron trioxide were mixed in a molar ratio of 0.325:0.25:0.1:0.075 and added to a ball mill jar along with an equal weight of grinding beads. A portion of ethanol was also added. The mixture was ball-milled at 300 rpm for 8 hours. The resulting powder was dried, thoroughly mixed in a mortar, and then processed according to the methods described in (b)-(c) of Example 1. After pressing and sintering, a sodium transition metal oxide cathode material with a glass-ceramic structure and a sodium-deficient manganese-based structure, Na, was obtained. 0.65 Mn 0.75 O2·(Mg 0.1 O2)·(B 0.15 O2), its XRD pattern is as follows Figure 1 As shown in Table 1, the cyclic performance is as follows.

[0071] Comparative Example 1 A sodium transition metal oxide cathode material with sodium-deficient manganese phase and no interfacial micro-melting sintering: (a) Sodium carbonate, manganese tetroxide, nickel hydroxide and titanium dioxide were mixed in a molar ratio of 0.31:0.2:0.15:0.25 and added to a ball mill jar along with an equal weight of grinding beads. Ethanol was also added and added to the ball mill jar along with an equal weight of grinding beads. The mixture was ball milled at 200 r / min for 2 h. The mixed powder was then taken out and mixed evenly in a mortar and dried in a vacuum drying oven.

[0072] (b) Press the powder mixed evenly in step (a) into a disc with a diameter of 20 mm on a cold press at a pressure of 100 MPa for 5 min.

[0073] (c) The pressed sheet mixture from step (b) was placed in a tube furnace and sintered at 500°C for 5 hours under a mixed atmosphere of oxygen and air (mixing ratio 2:8). Then, the temperature was increased to 1000°C and sintered at the same temperature for 8 hours. After natural cooling to room temperature, the comparative sample Na was obtained. 0.62 Mn 0.6 Ni 0.15 Ti 0.25 O2, its XRD pattern is as follows Figure 1 As shown.

[0074] Comparative Example 2 A sodium-rich manganese-based sodium transition metal oxide cathode material without interfacial micro-melting sintering: (d) Sodium carbonate, manganese tetroxide, nickel hydroxide and titanium dioxide were mixed in a molar ratio of 0.4:0.2:0.15:0.25 and added to a ball mill jar along with an equal weight of grinding beads. At the same time, some ethanol was added and added to the ball mill jar along with an equal weight of grinding beads. The mixture was ball milled at 200 r / min for 2 h. The mixed powder was then taken out and mixed evenly in a mortar and dried in a vacuum drying oven.

[0075] (e) Press the uniformly mixed powder from step (a) into a disc with a diameter of 20 mm on a cold press at a pressure of 100 MPa for 5 min.

[0076] (f) The pressed sheet mixture from step (b) was placed in a tube furnace and sintered at 500°C for 5 hours under a mixed atmosphere of oxygen and air (mixing ratio 2:8). Then, the temperature was increased to 1000°C and sintered at the same temperature for 8 hours. After natural cooling to room temperature, the comparative sample Na was obtained. 0.8 Mn 0.6 Ni 0.15 Ti 0.25 O2, its XRD pattern is as follows Figure 1 As shown.

[0077] Application Example 1 A sodium-ion battery, the preparation method of which includes the following steps: (1) The sample obtained in Example 1 was left to stand in air for 24 hours. The sample was used as the positive electrode active material. It was mixed with conductive carbon black and polyvinylidene fluoride (PVDF) binder in a mass ratio of 8:1:1 and then dissolved in N-methylpyrrolidone (NMP) solvent to make a positive electrode slurry. The slurry was coated on aluminum foil, dried and cut to obtain a positive electrode sheet.

[0078] (2) Assemble the positive electrode obtained in step (1) with metallic sodium and Celgard membrane to form a sodium-ion battery. The electrolyte of the sodium-ion battery is a 1M NaPF6 / (EC:DMC=1:1) electrolyte mixture (by volume EC:DMC=1:1). After assembly, let it stand for 24 hours, and then perform charge-discharge activation test.

[0079] Specifically, the test method was as follows: three charge-discharge cycles were performed at a current density of 0.1 C (1C=100 mA / g) within a voltage range of 2.0-4.3V; followed by a cycle performance test at 0.5C (1C=100 mA / g). The results are shown in Table 1.

[0080] Application Example 2 A sodium-ion battery, the preparation method of which includes the following steps: (1) The sample obtained in Example 2 was left to stand in air for 24 hours. It was used as the positive electrode active material and mixed with conductive carbon black and polyvinylidene fluoride (PVDF) binder in a mass ratio of 8:1:1. The mixture was then dissolved in N-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry. The slurry was coated on aluminum foil, dried, and cut to obtain a positive electrode sheet.

[0081] (2) Assemble the positive electrode obtained in step (1) with metallic sodium and Celgard membrane to form a sodium-ion battery. The electrolyte of the sodium-ion battery is a 1M NaPF6 / (EC:DMC=1:1) electrolyte mixture (by volume EC:DMC=1:1). After assembly, let it stand for 24 hours, and then perform charge-discharge activation test.

[0082] Specifically, the test method was as follows: three charge-discharge cycles were performed at a current density of 0.1 C (1C=100 mA / g) within a voltage range of 2.0-4.3V; followed by a cycle performance test at 0.5C (1C=100 mA / g). The results are shown in Table 1.

[0083] Application Example 3 A sodium-ion battery, the preparation method of which includes the following steps: (1) The sample obtained in Example 3 was left to stand in air for 24 hours. It was used as the positive electrode active material and mixed with conductive carbon black and polyvinylidene fluoride (PVDF) binder in a mass ratio of 8:1:1. The mixture was then dissolved in N-methylpyrrolidone (NMP) solvent to form a positive electrode slurry. The slurry was coated on aluminum foil, dried, and cut to obtain a positive electrode sheet.

[0084] (2) Assemble the positive electrode obtained in step (1) with metallic sodium and Celgard membrane to form a sodium-ion battery. The electrolyte of the sodium-ion battery is a 1M NaPF6 / (EC:DMC=1:1) electrolyte mixture (by volume EC:DMC=1:1). After assembly, let it stand for 24 hours, and then perform charge-discharge activation test.

[0085] Specifically, the test method was as follows: three charge-discharge cycles were performed at a current density of 0.1 C (1C=100 mA / g) within a voltage range of 2.0-4.3V; followed by a cycle performance test at 0.5C (1C=100 mA / g). The results are shown in Table 1.

[0086] Application Example 4 A sodium-ion battery, the preparation method of which includes the following steps: (1) The sample obtained in Example 4 was left to stand in air for 24 hours. It was used as the positive electrode active material and mixed with conductive carbon black and polyvinylidene fluoride (PVDF) binder in a mass ratio of 8:1:1. The mixture was then dissolved in N-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry. The slurry was coated on aluminum foil, dried, and cut to obtain a positive electrode sheet.

[0087] (2) Assemble the positive electrode obtained in step (1) with metallic sodium and Celgard membrane to form a sodium-ion battery. The electrolyte of the sodium-ion battery is a 1M NaPF6 / (EC:DMC=1:1) electrolyte mixture (by volume EC:DMC=1:1). After assembly, let it stand for 24 hours, and then perform charge-discharge activation test.

[0088] Specifically, the test method was as follows: three charge-discharge cycles were performed at a current density of 0.1 C (1C=100 mA / g) within a voltage range of 2.0-4.3V; followed by a cycle performance test at 0.5C (1C=100 mA / g). The results are shown in Table 1.

[0089] Application Example 5 A sodium-ion battery, the preparation method of which includes the following steps: (1) The sample obtained in Example 5 was left to stand in air for 24 hours. It was used as the positive electrode active material and mixed with conductive carbon black and polyvinylidene fluoride (PVDF) binder in a mass ratio of 8:1:1. The mixture was then dissolved in N-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry. The slurry was coated on aluminum foil, dried, and cut to obtain a positive electrode sheet.

[0090] (2) Assemble the positive electrode obtained in step (1) with metallic sodium and Celgard membrane to form a sodium-ion battery. The electrolyte of the sodium-ion battery is a 1M NaPF6 / (EC:DMC=1:1) electrolyte mixture (by volume EC:DMC=1:1). After assembly, let it stand for 24 hours, and then perform charge-discharge activation test.

[0091] Specifically, the test method was as follows: three charge-discharge cycles were performed at a current density of 0.1 C (1C=100 mA / g) within a voltage range of 2.0-4.3V; followed by a cycle performance test at 0.5C (1C=100 mA / g). The results are shown in Table 1.

[0092] Application Example 6 A sodium-ion battery, the preparation method of which includes the following steps: (1) The sample obtained in Example 6 was left to stand in air for 24 hours. It was used as the positive electrode active material and mixed with conductive carbon black and polyvinylidene fluoride (PVDF) binder in a mass ratio of 8:1:1. The mixture was then dissolved in N-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry. The slurry was coated on aluminum foil, dried, and cut to obtain a positive electrode sheet.

[0093] (2) Assemble the positive electrode obtained in step (1) with metallic sodium and Celgard membrane to form a sodium-ion battery. The electrolyte of the sodium-ion battery is a 1M NaPF6 / (EC:DMC=1:1) electrolyte mixture (by volume EC:DMC=1:1). After assembly, let it stand for 24 hours, and then perform charge-discharge activation test.

[0094] Specifically, the test method was as follows: three charge-discharge cycles were performed at a current density of 0.1 C (1C=100 mA / g) within a voltage range of 2.0-4.3V; followed by a cycle performance test at 0.5C (1C=100 mA / g). The results are shown in Table 1.

[0095] Application Example 7 A sodium-ion battery, the preparation method of which includes the following steps: (1) The sample obtained in Example 7 was left to stand in air for 24 hours. It was used as the positive electrode active material and mixed with conductive carbon black and polyvinylidene fluoride (PVDF) binder in a mass ratio of 8:1:1. The mixture was then dissolved in N-methylpyrrolidone (NMP) solvent to form a positive electrode slurry. The slurry was coated on aluminum foil, dried, and cut to obtain a positive electrode sheet.

[0096] (2) Assemble the positive electrode obtained in step (1) with metallic sodium and Celgard membrane to form a sodium-ion battery. The electrolyte of the sodium-ion battery is a 1M NaPF6 / (EC:DMC=1:1) electrolyte mixture (by volume EC:DMC=1:1). After assembly, let it stand for 24 hours, and then perform charge-discharge activation test.

[0097] Specifically, the test method was as follows: three charge-discharge cycles were performed at a current density of 0.1 C (1C=100 mA / g) within a voltage range of 2.0-4.3V; followed by a cycle performance test at 0.5C (1C=100 mA / g). The results are shown in Table 1.

[0098] Application Example 8 A sodium-ion battery, the preparation method of which includes the following steps: (1) The sample obtained in Example 8 was left to stand in air for 24 hours. It was used as the positive electrode active material and mixed with conductive carbon black and polyvinylidene fluoride (PVDF) binder in a mass ratio of 8:1:1. The mixture was then dissolved in N-methylpyrrolidone (NMP) solvent to form a positive electrode slurry. The slurry was coated on aluminum foil, dried, and cut to obtain a positive electrode sheet.

[0099] (2) Assemble the positive electrode obtained in step (1) with metallic sodium and Celgard membrane to form a sodium-ion battery. The electrolyte of the sodium-ion battery is a 1M NaPF6 / (EC:DMC=1:1) electrolyte mixture (by volume EC:DMC=1:1). After assembly, let it stand for 24 hours, and then perform charge-discharge activation test.

[0100] Specifically, the test method was as follows: three charge-discharge cycles were performed at a current density of 0.1 C (1C=100 mA / g) within a voltage range of 2.0-4.3V; followed by a cycle performance test at 0.5C (1C=100 mA / g). The results are shown in Table 1.

[0101] Application Example 9 A sodium-ion battery, the preparation method of which includes the following steps: (1) Comparative Example 1 was left to stand in air for 24 hours. The obtained sample was used as the positive electrode active material. It was mixed with conductive carbon black and polyvinylidene fluoride (PVDF) binder in a mass ratio of 8:1:1 and then dissolved in N-methylpyrrolidone (NMP) solvent to make a positive electrode slurry. The slurry was coated on aluminum foil, dried, and cut to obtain a positive electrode sheet.

[0102] (2) Assemble the positive electrode obtained in step (1) with metallic sodium and Celgard membrane to form a sodium-ion battery. The electrolyte of the sodium-ion battery is a 1M NaPF6 / (EC:DMC=1:1) electrolyte mixture (by volume EC:DMC=1:1). After assembly, let it stand for 24 hours, and then perform charge-discharge activation test.

[0103] Specifically, the test method was as follows: three charge-discharge cycles were performed at a current density of 0.1 C (1C=100 mA / g) within a voltage range of 2.0-4.3V; followed by a cycle performance test at 0.5C (1C=100 mA / g). The results are shown in Table 1.

[0104] Application Example 10 A sodium-ion battery, the preparation method of which includes the following steps: (1) Comparative Example 2 was left to stand in air for 24 hours. The obtained sample was used as the positive electrode active material. It was mixed with conductive carbon black and polyvinylidene fluoride (PVDF) binder in a mass ratio of 8:1:1 and then dissolved in N-methylpyrrolidone (NMP) solvent to make a positive electrode slurry. The slurry was coated on aluminum foil, dried, and cut to obtain a positive electrode sheet.

[0105] (2) Assemble the positive electrode obtained in step (1) with metallic sodium and Celgard membrane to form a sodium-ion battery. The electrolyte of the sodium-ion battery is a 1M NaPF6 / (EC:DMC=1:1) electrolyte mixture (by volume EC:DMC=1:1). After assembly, let it stand for 24 hours, and then perform charge-discharge activation test.

[0106] Specifically, the test method was as follows: three charge-discharge cycles were performed at a current density of 0.1 C (1C=100 mA / g) within a voltage range of 2.0-4.3V; followed by a cycle performance test at 0.5C (1C=100 mA / g). The results are shown in Table 1.

[0107] Figure 1 The diffraction peaks of all sodium-deficient phase samples with interfacial micro-melting sintering in Examples 1 to 8 show a P2 structure of sodium transition metal oxides, with few impurity peaks, proving that the main material obtained is a sodium-containing transition metal oxide cathode material. However, Comparative Example 1, as a sodium-deficient manganese-based sodium transition metal oxide cathode material without interfacial micro-melting sintering, shows phase separation in XRD, indicating that the sintering is incomplete in the absence of glass-forming elements; while Comparative Example 2, as a sodium-rich manganese-based sodium transition metal oxide cathode material without interfacial micro-melting sintering, shows further intensified phase separation.

[0108] from Figure 2SEM analysis of the intermediate electrode shows that after standing in air for 24 hours, the sample obtained in Example 1 was mixed and homogenized to prepare the electrode. The sample in Example 1 still maintained a complete crystalline state in the electrode, and the material particles showed stable interfacial adhesion (good interfacial micro-melting effect). This indicates that the sodium transition metal oxide cathode material with a sodium-deficient phase manganese based and a glass-ceramic structure, sintered by interfacial micro-melting, maintains a complete crystalline state after standing in air, does not decompose, has good water resistance, and allows for smooth electrode preparation. Please note... Figure 2 The size in the lower right corner is labeled as 500nm.

[0109] The sodium transition metal oxide cathode material Na with a sodium-deficient manganese-based phase and a glass-ceramic structure, prepared in Example 1, was subjected to interfacial micro-melting sintering. 0.62 Mn 0.6 O2·(Ti 0.1 O2Ni 0.15 O2)·(K 0.05 O2Li 0.1 O2) was left to stand in air for 24 hours, and sodium-ion batteries were assembled with sodium metal anodes and their electrochemical performance was tested. The results are as follows: Figure 3 As shown, the sodium-ion battery assembled from the sample of Example 1 has a reversible initial capacity of approximately 117 mAh / g (solid line, Na content is only 0.62) when cycled at a current density of 0.1C (10 mA / g) within a voltage range of 2.0~4.3V. In contrast, Comparative Example 2, as a sodium-rich manganese-based sodium transition metal oxide cathode material without interfacial micro-melting sintering, shows... 0.8 Mn 0.6 Ni 0.15 Ti 0.25 O2, when cycled at the same current density, also exhibits a reversible initial capacity of only 124 mAh / g (dashed line, Na content is 0.8%). The sodium-ion batteries corresponding to Example 1 and Comparative Example 2 have significantly different initial Na contents, but after standing in air for 24 hours, their capacities are not significantly different. This is mainly because the sodium-ion battery corresponding to Comparative Example 2 is unstable in air, and standing causes some of the positive electrode material to absorb water and decompose. Meanwhile, the sodium-ion battery prepared in Example 1 has a higher average voltage range compared to Comparative Example 2. This indicates that although Example 1 was designed with a sodium-deficient phase, the use of interfacial micro-melting sintering technology allowed the Na source to be fully sintered into the material structure, enabling complete insertion and extraction of sodium ions during charging and discharging, and resulting in a higher average voltage.

[0110] In the multiplier test, such as Figure 4As shown, Example 1 exhibits reversible initial capacities of approximately 118 mAh / g, 111 mAh / g, 100 mAh / g, 94 mAh / g, 87 mAh / g, and 70 mAh / g during cycling at current densities of 0.1C (10 mA / g), 0.2C (20 mA / g), 0.5C (50 mA / g), 1C (100 mA / g), 2C (200 mA / g), and 10C (1000 mA / g), respectively. These are significantly higher than the rate retention of Comparative Example 2 (which only achieved approximately 41 mAh / g at 10C). This is because Example 1 employs a sodium defect design principle, which, while enhancing material stability in air (reducing the impact of alkali residue water absorption), also provides more sodium vacancies within the structure itself, offering a wider space for sodium ion migration and further improving the material's rate performance.

[0111] In long-cycle testing, batteries were assembled using relevant cathode materials that had been left to stand in air for 24 hours, such as... Figure 5 As shown, when cycled at 0.5C (50mA / g), the material of Example 1 still retains a discharge specific capacity of approximately 100mAh / g, and after 100 long cycles, the capacity retention rate is still approximately 88%, demonstrating strong cycle stability. In contrast, although Comparative Example 2 maintains a high discharge capacity at the initial stage, its capacity rapidly decays after 100 long cycles, with the capacity retention rate dropping to approximately 36%. This is because the material of Example 1, when left to stand in air for 24 hours, does not absorb water or decompose, thus maintaining its original specific capacity and cycle performance. In contrast, the material of Comparative Example 2 absorbs water in air, even undergoing partial decomposition, resulting in a decrease in the initial specific capacity and a significant reduction in cycle performance.

[0112] In addition, Table 1 shows the materials of Examples 1-8, the intrinsic alkali residue (residual alkali content), the moisture content after standing in air for 24 hours, and the first-cycle specific capacity of the cathode materials after standing in air when assembled into batteries. The results show that, as sodium-deficient manganese-based sodium transition metal oxide cathode materials obtained through special design, Examples 1-8 all exhibit extremely low residual alkali content and extremely high air stability. Furthermore, as cathode materials prepared using interfacial micro-melting sintering technology, the materials themselves do not exhibit phase separation (…). Figure 1(XRD). Therefore, although Examples 1-8 are sodium-deficient phase designs, they still maintain a high initial specific capacity. In contrast, although the material of Comparative Example 1 is designed with a sodium-deficient phase, the lack of interfacial micro-melting sintering technology caused phase separation, resulting in a lower initial specific capacity, alkaline residue, and higher moisture content. The material of Comparative Example 2 is designed with a sodium-rich phase and was not sintered using interfacial micro-melting technology, leading to further phase separation. Therefore, although its initial specific capacity is high (sodium-rich phase), its alkaline residue is also extremely high, making the material highly susceptible to moisture absorption and deterioration in air. In summary, the sodium-deficient manganese-based sodium transition metal oxide cathode material with a glass-ceramic structure and interfacial micro-melting sintering technology of this application significantly improves the sintering effect of sodium-deficient phase sodium battery cathode materials, simultaneously enhancing the material's air stability, cycle stability, and rate performance. This greatly broadens the preparation path and application scenarios of sodium-ion battery cathode materials, providing key technical support for the industrialization of high-performance sodium-ion batteries.

[0113] Table 1

[0114] It should be understood that the terminology used in this application specification is for the purpose of describing particular embodiments only and is not intended to limit the application.

[0115] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0116] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and such modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A sodium transition metal oxide cathode material containing a glass-ceramic structure, characterized in that, The sodium transition metal oxide cathode material has the following general formula: Na x Mn a O2·(M b O2)·(U c O2); Among them, 0.5≤x≤0.7, a>0, b>0, c>0, a+b+c=1; Na x Mn a O2 is the inner layer structure of the sodium transition metal oxide cathode material, (M b O2) and (U c O2) is the outer layer structure of the sodium transition metal oxide cathode material, and M is a ceramic element, the melting point of the compound of the ceramic element is greater than or equal to 1000℃, and U is a glass-forming element, the melting point of the compound of the glass-forming element is less than 1000℃.

2. The cathode material as described in claim 2, characterized in that, Na x Mn a The particle size corresponding to O2 is greater than (M) b The particle size corresponding to O2; and / or, Na x Mn a The particle size corresponding to O2 is larger than (U c The particle size corresponding to O2).

3. The cathode material as described in claim 1, characterized in that, M is selected from one or more of Cu, Ca, Mg, Zn, Fe, Co, Al, La, Ti, Ni or Zr, and U is selected from one or more of Li, K, B, Si.

4. The positive electrode material as described in claim 1, characterized in that, 0.55≤x≤0.65、0.75≥a≥0.5、0.25≥b≥0.05、0.2≥c≥0.

05.

5. The positive electrode material as described in claim 4, characterized in that, x+c≥0.

7.

6. The cathode material as described in claim 4, characterized in that, The sodium transition metal oxide containing a glass-ceramic structure is: Na 0.62 Mn 0.6 O2·(Ti 0.1 O2 Ni 0.15 O2)·(K 0.05 O2 Li 0.1 O2); Na 0.6 Mn 0.55 O2·(La 0.15 O2 Ni 0.15 O2)·(Li 0.15 O2); Na 0.55 Mn 0.6 O2·(Ca 0.05 O2Ni 0.15 O2Zn 0.15 O2)(Si 0.05 O2); Na 0.6 Mn 0.5 O2·(Zr 0.1 O2Ni 0.2 O2Cu 0.1 O2)·(K 0.1 O2); Na 0.62 Mn 0.75 O2·(Fe 0.05 O2Ni 0.15 O2)·(Li 0.05 O2); So 0.62 Mr 0.65 O2·(Co 0.15 O2)·(Li 0.2 O2); Na 0.62 Mn 0.75 O2·(Al 0.15 O2)·(K 0.1 O2); And 0.65 Mn 0.75 O2·(Mg 0.1 O2)·(B 0.15 O2); At least one of them.

7. The cathode material according to any one of claims 1 to 6, characterized in that, The main phase of the cathode material is the P2 phase.

8. A method for preparing a sodium transition metal oxide cathode material with a glass-ceramic structure as described in any one of claims 1 to 7, characterized in that, The preparation method includes: According to the stoichiometric ratio, sodium-containing compounds, manganese-containing compounds, M-containing compounds, and U-containing compounds are mixed, ball-milled, refined, pressed into tablets, and sintered to obtain the sodium transition metal oxide cathode material with a glass-ceramic structure.

9. The preparation method according to claim 8, characterized in that, According to the molar ratio, the proportion of sodium in the sodium-containing compound: manganese in the manganese-containing compound: M in the M-containing compound: U in the U-containing compound is (0.55~0.65): (0.5~0.75): (0.05~0.25): (0~0.2). The sintering conditions are as follows: first, sinter at a constant temperature of 400-600℃ for 5-12 hours, then raise the temperature to 800-850℃ and sinter at a constant temperature for 5-12 hours, and finally raise the temperature to 900-1000℃ and sinter at a constant temperature for 2-8 hours. The sintering atmosphere is oxygen, air, or a mixture of oxygen and air. The sodium-containing compound is at least one of sodium carbonate, sodium acetate, sodium bicarbonate, and sodium hydroxide. The manganese-containing compound is at least one of manganese sulfide, manganese dioxide, manganese tetroxide, manganese hydroxide, manganese carbonate, and manganese oxalate. The M-containing compound is at least one of M-containing oxides, M-containing carbonates, M-containing oxalates, and M-containing hydroxides; The U-containing compound is at least one of U-containing carbonates, U-containing hydroxides, and U-containing amorphous oxides.

10. The preparation method according to claim 8, characterized in that, The manganese-containing compound has a particle size of 5-15 μm, and the M-containing compound and the U-containing compound have a particle size of 500 nm-5 μm.

11. A sodium-ion battery, comprising a positive electrode material, characterized in that, The cathode material comprises the sodium transition metal oxide cathode material with a glass-ceramic structure as described in any one of claims 1 to 7, or the sodium transition metal oxide cathode material with a glass-ceramic structure prepared by the preparation method described in any one of claims 8 to 10.

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