Sodium ion battery composite positive electrode material and preparation method and application thereof

Abstract

This invention discloses a sodium-ion battery composite cathode material, its preparation method, and its application. The cathode material includes a matrix material and a double-layer heterostructure coating on the surface of the matrix material; the matrix material is NaNi. a Fe b Mn c O2, a+b+c=1, 0≤a<1, 0≤b<1, 0≤c<1; the bilayer heterogeneous structure coating is formed by the diazotization reaction of organic molecules in the inner inorganic coating and the outer organic coating; the inner inorganic coating can effectively block moisture, CO2 and electrolyte corrosion in the environment, and inhibit the dissolution of transition metals and side reactions; the organic cross-linked network formed by the diazotization reaction of the outer layer has good flexibility and hydrophobicity, further buffering volumetric strain stress and blocking environmental media. The bilayer synergistic protection enables the material to maintain structural integrity during long-term cycling, significantly improving cycling stability.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, specifically to a sodium-ion battery composite cathode material, its preparation method, and its application. Background Technology

[0002] With the rapid development of renewable energy and the increasing demand for large-scale energy storage, sodium-ion batteries, due to their abundant resources and low cost, are considered an important supplement and alternative technology to lithium-ion batteries. Among the various components of sodium-ion batteries, the cathode material is the core key determining its energy density, cycle life, and rate performance. Currently, sodium-ion battery cathode materials mainly include three major systems: layered transition metal oxides, polyanionic compounds, and Prussian blue-based materials. Among these, layered transition metal oxides (especially those with the general formula NaNi) are particularly important. a Fe b Mn c O2-based nickel-iron-manganese ternary system has become one of the most promising cathode material systems for sodium-ion batteries due to its high theoretical specific capacity and relatively simple synthesis process.

[0003] However, layered transition metal oxides are sensitive to air humidity and are prone to water absorption side reactions. At the same time, during charge and discharge, the repeated insertion and extraction of Na+ can induce large volumetric strain, which in turn leads to irreversible phase transitions, interlayer slip, and particle cracking in the crystal structure. These structural damages directly result in poor cycle stability and rapid capacity decay, thus severely limiting their electrochemical performance.

[0004] To address the aforementioned issues, common modification strategies include bulk doping, surface coating, and morphology control. Among these, surface coating is an effective means of constructing stable interfaces and suppressing side reactions. Regarding inorganic oxide coating, CN115483396A synthesized Al2O3-coated nickel-iron-manganese-based cathode materials using Al2NO3 as a raw material; CN117936748A disclosed coating schemes using titanium oxide, tungsten oxide, and tin oxide; and CN117855454A synthesized TiO2 / SiO2 composite-coated modified nickel-iron-manganese-based cathode materials. However, while traditional inert oxide coatings such as Al2O3 and TiO2 can improve interface stability to some extent, their low electronic and ionic conductivity hinders electron transport and Na+. + Migration has an adverse effect on rate performance.

[0005] Regarding organic polymer coating, CN116682937A discloses coating the electrode surface with hydrophobic organic coatings such as PVDF, PTFE, and FEP, which can protect the O3 phase layered oxide material from phase transition side reactions and improve air stability. However, pure organic coatings have the drawbacks of poor mechanical strength and thermal stability, and are prone to damage during long-term cycling.

[0006] In summary, existing single coating strategies cannot simultaneously achieve both stability and long-term cycling performance. Furthermore, the combination of general organic and inorganic coatings is achieved through simple physical adsorption, resulting in weak bonding and easy detachment during cycling, leading to poor material modification effects. Summary of the Invention

[0007] The main objective of this invention is to provide a sodium-ion battery composite cathode material, its preparation method, and its application. This invention aims to solve the technical problems that existing single coating strategies are difficult to balance stability and long-term cycling performance, and that conventional organic and inorganic coatings are combined through physical adsorption and are prone to detachment during cycling, resulting in poor modification effects.

[0008] To achieve the above objectives, the first aspect of the present invention provides a sodium-ion battery composite cathode material, comprising a matrix material and a double-layer heterostructure coating on the surface of the matrix material. The matrix material is NaNi. a Fe b Mn c O2, a+b+c =1, 0≤a<1, 0≤b<1, 0≤c<1; the double-layer heterostructure coating is formed by the diazotization reaction of organic molecules in the inner inorganic coating and the outer organic coating.

[0009] The matrix material of this invention is a layered transition metal oxide NaNi. a Fe b Mn c O2, where a, b, and c are the molar proportions of three transition metals: nickel, iron, and manganese, respectively, with the sum of the three being 1, and the proportion of each element being between 0 and 1. A typical formulation includes NaNi. 0.33 Fe 0.33 Mn 0.33 O2 (ternary equal proportion), NaNi 0.5 Fe 0.2 Mn 0.3 O2 (nickel-rich formulation), NaNi 0.15 Fe 0.5 Mn 0.35O2 (iron-rich formulation), etc. This material belongs to the O3-type layered structure, with Na+ located at octahedral sites between transition metal layers. The transition metal layers are composed of octahedrons of Ni, Fe, and Mn, connected by oxygen ions to form two-dimensional ion transport channels. This system was chosen as the matrix because it possesses advantages such as high theoretical specific capacity (140-160 mAh / g), moderate operating voltage (2.5-4.2 V vs. Na+ / Na), low raw material cost, and mature synthesis process.

[0010] The bilayer heterogeneous structure coating of this invention refers to a composite coating structure composed of an inner inorganic coating and an outer organic coating, formed by chemical bonding between the two layers, with its thickness typically controlled within the range of 1-10 nm. "Heterogeneous" refers to the significant differences in chemical composition, crystal structure, and physical properties between the two layers: the inner inorganic coating is usually a metal oxide or its composite, characterized by density, high hardness, and low ionic / electronic conductivity; the outer organic coating is a polymer network formed through a diazotization reaction, exhibiting good flexibility, strong hydrophobicity, and superior ionic conductivity. The two coatings are tightly bonded by chemical bonds, forming a complete and continuous coating layer that uniformly covers the entire surface of the matrix material particles, including the surface of primary particles and the pore walls of secondary particles.

[0011] Inner inorganic coatings refer to metal oxides or their composite layers directly coated on the surface of a substrate material. They are typically prepared using sol-gel methods, chemical precipitation, atomic layer deposition, or hydrothermal methods, forming continuous, dense, and uniform nanoscale thin films on the substrate surface. Inner inorganic coatings provide a rigid physical barrier, significantly improving the material's air and interfacial stability, reducing performance degradation during storage and side reactions during cycling. Simultaneously, the rigid structure of the inorganic coating provides a stable substrate for the subsequent adhesion of organic coatings, and the active groups such as hydroxyl groups on the surface can form chemical bonds with organic molecules, enhancing the bonding strength of the bilayer interface.

[0012] The outer organic coating is a polymer network layer formed by in-situ polymerization on the surface of the inorganic coating through a diazotization reaction. Its organic molecules are usually monomers or derivatives containing aromatic amine groups. The diazotization reaction refers to the reaction of aromatic amines with nitrites under acidic conditions to generate diazonium salts. Subsequently, the diazonium salts form a cross-linked polymer network containing azo bonds on the surface of the inorganic coating through coupling, polymerization, and other reactions.

[0013] The inventors considered that the diazotization reaction was used to construct the organic coating because of its unique in-situ polymerization and chemical bonding characteristics. The organic molecules generated by the diazotization reaction possess highly reactive diazonium groups, which can undergo nucleophilic substitution or coupling reactions with active sites such as hydroxyl and carboxyl groups on the inorganic coating surface, forming covalent bonds, rather than simple physical adsorption. This chemical bonding firmly anchors the organic coating to the inorganic surface, with a binding force stronger than physical interactions such as van der Waals forces and hydrogen bonds. This effectively resists mechanical stress during cycling and prevents the coating from peeling off.

[0014] The organic coating formed by diazotization exhibits excellent interfacial bonding strength, flexibility, and ion conductivity, solving the problems of easy peeling and low mechanical strength of existing organic coatings. The cross-linked network structure effectively buffers the volumetric strain of the matrix material, preventing cracking of the inorganic coating. Polar groups promote Na+... + Rapid transmission reduces interface impedance and improves rate performance; in addition, the hydrophobicity of the organic coating further enhances the material's air stability, forming a synergistic protection with the inner inorganic coating and significantly extending the material's cycle life.

[0015] Furthermore, the inorganic coating is one or more combinations of metal oxides and / or metal-like oxides; the organic coating is one or more combinations of para-, ortho-, and meta-substituted aromatic primary amine compounds.

[0016] Furthermore, the inorganic coating is one or more of the following: iron oxide, boron oxide, calcium oxide, bismuth oxide, niobium oxide, copper oxide, aluminum oxide, zinc oxide, silver oxide, strontium oxide, cerium oxide, chromium oxide, magnesium oxide, cadmium oxide, gadolinium oxide, yttrium oxide, titanium oxide, tin oxide, and tungsten oxide. The organic coating is one or more of the following: p-aminobenzenesulfonic acid, o-aminobenzenesulfonic acid, m-aminobenzenesulfonic acid, p-aminobenzoic acid, o-aminobenzoic acid, m-aminobenzoic acid, p-aminobenzonitrile, o-aminobenzonitrile, m-aminobenzonitrile, p-aminoacetophenone, o-aminoacetophenone, m-aminoacetophenone, p-aminobenzyl alcohol, o-aminobenzyl alcohol, m-aminobenzyl alcohol, p-aminobenzoarsic acid, o-aminobenzoarsic acid, m-aminobenzoarsic acid, p-aminophenol, o-aminophenol, m-aminophenol, p-methoxyaniline, o-methoxyaniline, m-methoxyaniline, p-aminobenzamide, o-aminobenzamide, m-aminobenzamide.

[0017] A second aspect of this invention provides a method for preparing the aforementioned sodium-ion battery composite cathode material, comprising the following steps: (1) The sodium source and nickel-iron-manganese-based precursor were subjected to high-temperature calcination to obtain the matrix material; (2) Disperse the matrix material in an ethanol solution of the metal oxide and / or metal oxide-like substances, stir and mix to obtain a homogeneous solution; dry the homogeneous solution and then sinter it at high temperature to obtain an intermediate of the matrix material coated with metal oxide and / or metal oxide-like substances; (3) The aromatic primary amine compound was dissolved in an acetonitrile solution containing tert-butyl nitrite under low temperature and inert atmosphere. After mixing evenly, the intermediate was added and stirred thoroughly to react and mix evenly. Finally, the mixture was filtered, washed, and vacuum dried to obtain the sodium-ion battery composite cathode material.

[0018] Further, the sodium source mentioned in step (1) is one or more of sodium carbonate, sodium bicarbonate, sodium acetate and sodium oxalate; And / or, the molar ratio of the nickel-iron-manganese precursor to the sodium source is 1:1 to 1:2; And / or, the high-temperature calcination treatment is carried out at a temperature of 800-1000℃ for a time of 16-24h.

[0019] Further, the stirring time in step (2) is 1-10 h; the drying temperature is 40-80℃ and the reaction time is 8-14 h; the sintering temperature is 150-250℃ and the reaction time is 1-5 h.

[0020] Further, the inert atmosphere in step (3) is nitrogen, the temperature is 0~5℃, the stirring time is 1-10 h, the vacuum drying temperature is 50-120℃, and the drying time is 7-15 h.

[0021] Furthermore, the inorganic coating is yttrium oxide, and the organic coating is p-aminobenzenesulfonic acid; And / or, the mass ratio of yttrium oxide to the matrix material is 1:100 to 1:1000; And / or, the mass ratio of p-aminobenzenesulfonic acid to the intermediate is 1:400 to 1:1000.

[0022] Furthermore, the concentration of the tert-butyl nitrite acetonitrile solution is 0.0015-0.01 g / mL.

[0023] A third aspect of the present invention provides a sodium-ion battery comprising the sodium-ion battery composite cathode material described in any of the above embodiments.

[0024] Beneficial effects: The present invention aims to provide a composite cathode material for sodium-ion batteries, comprising a bilayer heterogeneous coating on the surface of a substrate, consisting of an inner inorganic coating and an organic coating formed by diazotization. The inner inorganic coating effectively blocks moisture, CO2, and electrolyte corrosion from the environment, inhibiting transition metal dissolution and side reactions. The outer organic cross-linked network formed by diazotization possesses good flexibility and hydrophobicity, further buffering volumetric strain stress and blocking environmental media. This dual-layer synergistic protection enables the material to maintain structural integrity during long-term cycling, significantly improving cycle stability.

[0025] This invention utilizes a diazotization reaction to polymerize organic molecules in situ on the surface of an inorganic coating, forming a covalently bonded organic-inorganic heterogeneous interface, replacing the weak bonding method relying on physical adsorption in existing technologies. The strong covalent bonding of the azo bonds firmly anchors the organic coating to the surface of the inorganic coating, effectively preventing coating peeling during long-term battery cycling and ensuring long-term protection.

[0026] In this invention, the functional groups on the surface of the inorganic-organic bilayer heterostructure coating can construct a dense positive electrode-electrolyte film, which can promote the formation of Na+. + Rapid transport at the interface helps reduce interfacial impedance, improves electrochemical performance, and enables organic molecules to be evenly distributed on the inorganic surface, resulting in more uniform performance and improved overall modification effect. Attached Figure Description

[0027] Figure 1 The XRD patterns are of the cathode materials prepared in Example 1, Comparative Examples 1 and 2 of this invention. Figure 2 SEM images of the cathode materials prepared in Example 1, Comparative Examples 1 and 2 of this invention; Figure 3 These are TEM images of the cathode materials prepared in Example 1 and Comparative Example 2 of the present invention.

[0028] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0029] Unless otherwise specified, the experimental methods described in the following embodiments of the present invention are generally performed under conventional conditions or as recommended by the manufacturer. All commonly used chemical reagents used in the embodiments are commercially available products.

[0030] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0031] The following embodiments further describe the present invention, but these embodiments are not intended to limit the scope of protection of the present invention.

[0032] The specific implementation method is as follows: Example 1 (1) Sodium source Na2CO3 and nickel-iron-manganese-based precursor Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)₂ was ground and mixed evenly at a molar ratio of 1.05:1, then calcined in air at 900℃ for 20 h, and after cooling, NaNi was obtained. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 matrix materials; (2) Take 1 g of NaNi generated in step (1) 1 / 3 Fe 1 / 3 Mn 1 / 3 The O2 matrix material was dispersed in 15 mL of ethanol solution containing 0.015 g of yttrium oxide and stirred thoroughly to obtain a homogeneous solution. The homogeneous solution was dried at 80 °C and then sintered at 200 °C for 3 h in air atmosphere to obtain yttrium oxide-coated sodium nickel iron manganate intermediate. (3) Under low temperature conditions of 0-5℃ and nitrogen atmosphere, 0.0025 g of p-aminobenzenesulfonic acid was dissolved in 15 mL of acetonitrile solution containing 50 μL of tert-butyl nitrite. After mixing evenly, intermediate material was added and stirred for 6 h to mix evenly. Finally, the mixture was filtered, washed, and vacuum dried at 110℃ to obtain p-aminobenzenesulfonic acid-yttrium oxide coated nickel-iron-manganese composite cathode material.

[0033] Example 2 (1) Sodium source Na2CO3 and nickel-iron-manganese-based precursor Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)₂ was ground and mixed evenly at a molar ratio of 1.05:1, then calcined in air at 900℃ for 20 h, and after cooling, NaNi was obtained. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 matrix materials; (2) Take 1 g of NaNi generated in step (1) 1 / 3 Fe 1 / 3 Mn 1 / 3 The O2 matrix material was dispersed in 15 mL of ethanol solution containing 0.015 g of yttrium oxide and stirred thoroughly to obtain a homogeneous solution. The homogeneous solution was dried at 80 °C and then sintered at 200 °C for 3 h in air atmosphere to obtain yttrium oxide-coated sodium nickel iron manganate intermediate. (3) Under low temperature conditions of 0-5℃ and nitrogen atmosphere, 0.001 g of p-aminobenzenesulfonic acid was dissolved in 15 mL of acetonitrile solution containing 50 μL of tert-butyl nitrite. After mixing evenly, intermediate material was added and stirred for 6 h to mix evenly. Finally, the mixture was filtered, washed, and vacuum dried at 110℃ to obtain p-aminobenzenesulfonic acid-yttrium oxide coated nickel-iron-manganese composite cathode material.

[0034] Example 3 (1) Sodium source Na2CO3 and nickel-iron-manganese-based precursor Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)₂ was ground and mixed evenly at a molar ratio of 1.05:1, then calcined in air at 900℃ for 20 h, and after cooling, NaNi was obtained. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 matrix materials; (2) Take 1 g of NaNi generated in step (1) 1 / 3 Fe 1 / 3 Mn 1 / 3 The O2 matrix material was dispersed in 15 mL of ethanol solution containing 0.015 g of yttrium oxide and stirred thoroughly to obtain a homogeneous solution. The homogeneous solution was dried at 80 °C and then sintered at 200 °C for 3 h in air atmosphere to obtain yttrium oxide-coated sodium nickel iron manganate intermediate. (3) Under low temperature conditions of 0-5℃ and nitrogen atmosphere, 0.003 g of p-aminobenzenesulfonic acid was dissolved in 15 mL of acetonitrile solution containing 50 μL of tert-butyl nitrite. After mixing evenly, intermediate material was added and stirred for 6 h to mix evenly. Finally, the mixture was filtered, washed, and vacuum dried at 110℃ to obtain p-aminobenzenesulfonic acid-yttrium oxide coated nickel-iron-manganese composite cathode material.

[0035] Example 4 The method of Example 1 was followed, except that yttrium oxide in step (2) was replaced with aluminum oxide of equal mass based on the same metal element.

[0036] Example 5 The method of Example 1 was followed, except that yttrium oxide in step (2) was replaced with zinc oxide of equal mass based on the same metal element.

[0037] Example 6 The procedure was carried out according to Example 1, except that p-aminobenzenesulfonic acid in step (3) was replaced with an equal molar mass of 2-aminobenzenesulfonic acid.

[0038] Example 7 The procedure was carried out according to Example 1, except that p-aminobenzenesulfonic acid in step (3) was replaced with an equal molar mass of 3-aminobenzenesulfonic acid.

[0039] Example 8 The procedure was carried out according to Example 1, except that p-aminobenzenesulfonic acid in step (3) was replaced with an equal molar mass of p-aminoacetophenone.

[0040] Example 9 The procedure was carried out according to Example 1, except that p-aminobenzenesulfonic acid in step (3) was replaced with an equal molar mass of p-aminobenzonitrile.

[0041] Example 10 The procedure was carried out according to Example 1, except that the NaNi in Example 1 was... 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 matrix material replaced with NaNi 0.5 Mn 0.5 O2.

[0042] Example 11 The procedure was carried out according to Example 1, except that the NaNi in Example 1 was... 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 matrix material replaced with NaNi 0.2 Fe 0.2 Mn 0.6 O2.

[0043] Comparative Example 1 Sodium source Na2CO3 and nickel-iron-manganese-based precursor Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)₂ was ground and mixed evenly at a molar ratio of 1.05:1, then calcined in air at 900℃ for 20 h, and after cooling, NaNi was obtained. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 matrix material, which is directly used as the positive electrode material for subsequent performance testing.

[0044] Comparative Example 2 (1) Sodium source Na2CO3 and nickel-iron-manganese-based precursor Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)₂ was ground and mixed evenly at a molar ratio of 1.05:1, then calcined in air at 900℃ for 20 h, and after cooling, NaNi was obtained. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 matrix materials; (2) Take 1 g of NaNi generated in step (1) 1 / 3 Fe 1 / 3 Mn 1 / 3 The O2 matrix material was dispersed in 15 mL of ethanol solution containing 0.015 g of yttrium oxide and stirred thoroughly to obtain a homogeneous solution. The homogeneous solution was dried at 80°C and then sintered at 200°C for 3 h in air atmosphere to obtain yttrium oxide-coated sodium nickel iron manganate intermediate. This intermediate was directly used as the cathode material for subsequent performance testing.

[0045] Comparative Example 3 (1) Sodium source Na2CO3 and nickel-iron-manganese-based precursor Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)₂ was ground and mixed evenly at a molar ratio of 1.05:1, then calcined in air at 900℃ for 20 h, and after cooling, NaNi was obtained. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 matrix materials; (2) Dissolve 0.0025 g of p-aminobenzenesulfonic acid in 15 mL of acetonitrile solution containing 50 μL of tert-butyl nitrite under low temperature conditions of 0-5℃ and nitrogen atmosphere, mix well, and then add NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 The O2-based material was stirred and reacted for 6 hours to achieve uniform mixing. Finally, it was filtered, washed, and vacuum dried at 110°C to obtain a nickel-iron-manganese composite cathode material coated with p-aminobenzenesulfonic acid.

[0046] Comparative Example 4 (1) Sodium source Na2CO3 and nickel-iron-manganese-based precursor Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)₂ was ground and mixed evenly at a molar ratio of 1.05:1, then calcined in air at 900℃ for 20 h, and after cooling, NaNi was obtained. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 matrix materials; (2) Dissolve 0.0025 g of p-aminobenzenesulfonic acid in 15 mL of acetonitrile solution containing 50 μL of tert-butyl nitrite under low temperature conditions of 0-5℃ and nitrogen atmosphere, mix well, and then add NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 matrix material was stirred and reacted for 6 hours to mix evenly. Finally, it was filtered, washed, and dried under vacuum at 110°C to obtain a nickel-iron-manganese-based intermediate coated with p-aminobenzenesulfonic acid. (3) Take 1 g of the intermediate material generated in step (2) and disperse it in 15 mL of ethanol solution containing 0.015 g of yttrium oxide. Stir and mix thoroughly to obtain a uniform solution. Dry the uniform solution at 80°C and sinter it at 200°C for 3 h in air atmosphere to obtain the nickel-iron-manganese composite cathode material of p-aminobenzenesulfonic acid-yttrium oxide.

[0047] Performance testing The positive electrode materials obtained in the examples and comparative examples were used to prepare coin cells for sodium-ion battery electrochemical performance testing. The specific steps were as follows: Active material, conductive agent (Super P), and binder (PVDF) were mixed uniformly at a mass ratio of 8:1:1, coated onto aluminum foil, dried, and sliced ​​to obtain an electrode sheet with a diameter of approximately 12 mm. A sodium metal sheet was then used as the counter electrode, and the electrolyte was an EC / PC solution of 1 M NaClO4 (volume ratio 1:1, containing 5% FEC). A 2032 coin cell was assembled, and its electrochemical performance was tested on a Neware testing system at 25°C, 2-4.0 V, and 1 C. The test results are shown in Table 1 and... Figures 1-3 As shown.

[0048] Table 1

[0049] As can be seen from the table data, in the system with yttrium oxide as the inorganic coating and p-aminobenzenesulfonic acid as the organic coating, Example 1 showed the best 1C discharge capacity (114.27 mAh / g), first-cycle efficiency (97.21%), and 100-cycle capacity retention (90.35%). With the decrease or increase of p-aminobenzenesulfonic acid content in Examples 2 and 3, all performance characteristics decreased to varying degrees, indicating that the p-aminobenzenesulfonic acid content affects electrochemical performance. Furthermore, comparing Example 1 with Comparative Example 4 reveals that the coating order also affects performance: Example 1, using a process of "inorganic coating first, then organic coating," significantly outperformed Comparative Example 4's process of "organic coating first, then inorganic coating," in terms of first-cycle efficiency and cycle stability. The latter's first-cycle efficiency was only 88.03%, and its 100-cycle capacity retention was only 83.71%. Furthermore, the overall data also shows that the synergistic use of inorganic and organic coatings can significantly improve battery performance. Compared to Comparative Example 2, which uses only an inorganic coating, or Comparative Example 3, which uses only an organic coating, the combined examples show significant advantages in both initial efficiency and capacity retention. Regarding the choice of organic materials, p-aminobenzenesulfonic acid also exhibits superior cycle stability compared to other materials such as 2-aminobenzenesulfonic acid and 3-aminobenzenesulfonic acid. The results of Examples 10 and 11 demonstrate that the coating modification strategy is effective for NaNi batteries with different nickel-iron-manganese ratios. a Fe b Mn cO2 layered oxide matrix materials can all be effectively improved in terms of their cycle stability, which proves that the double-layer heterostructure coating of the present invention has certain applicability to improving the performance of different matrix materials.

[0050] Figure 1 The images show the XRD patterns of the cathode materials prepared in Example 1, Comparative Examples 1 and 2. It can be seen that the p-aminobenzenesulfonic acid-yttrium oxide-coated nickel-iron-manganese composite cathode material prepared in Example 1 has no impurity phases and good crystallinity, proving that the coating layer does not affect the crystal structure of the matrix material.

[0051] Figure 2 SEM images of the cathode materials prepared in Example 1, Comparative Examples 1, and Comparative Examples 2 are shown. It can be seen that the surface of the matrix material particles prepared in Comparative Example 1 is very smooth, while the surface of the material in Example 1 is coated with a coating, indicating the successful formation of an organic-inorganic heterostructure coating of p-aminobenzenesulfonic acid and yttrium oxide. In Comparative Example 1, the secondary particle surface is relatively smooth without a coating; however, after coating with a Y2O3 inorganic coating in Comparative Example 2, more small particles appear on the surface of the secondary particles, proving the presence of Y2O3. Furthermore, in Example 1, after coating with p-aminobenzoic acid on top of the Y2O3 inorganic coating, the surface of the secondary particles shows even more particles, proving the presence of p-aminobenzoic acid and the organic-inorganic heterostructure coating.

[0052] Figure 3 The images show TEM images of Comparative Example 2 and Example 1. A continuous thin coating of approximately 3 nm thickness is observed on the substrate surface of Comparative Example 2. The image on the right shows Example 1, which contains a heterostructure coating. At the same scale, a more obvious and continuous coating layer of approximately 6 nm thickness is visible on the substrate surface, and the coverage is more uniform along the interface. Compared to the Y₂O₃ coating alone, no obvious delamination gaps or peeling cracks are observed in the interface region of the heterostructure coating. This indicates that the cross-linked network formed by the diazotization reaction of the outer organic component, together with the inner Y₂O₃ inorganic coating, constructs a more complete interface coverage structure. This supports a more stable bonding of the two coating layers at the microstructural level and helps improve structural integrity during long-term cycling.

[0053] In summary, the results demonstrate that the bilayer heterogeneous coating formed by the diazotization reaction of organic molecules in the inner inorganic coating and the outer organic coating, especially the composite coating formed by p-aminobenzenesulfonic acid and yttrium oxide, can effectively inhibit the erosion of the substrate material by the electrolyte, improve the interfacial stability and structural integrity of the material, and enhance the cycle performance.

[0054] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A sodium-ion battery composite cathode material, characterized in that, Includes a substrate material and a two-layer heterogeneous coating on the surface of the substrate material; The matrix material is NaNi. a Fe b Mn c O2, a+b+c =1, 0≤a<1, 0≤b<1, 0≤c<1; the double-layer heterostructure coating is formed by the diazotization reaction of organic molecules in the inner inorganic coating and the outer organic coating.

2. The sodium-ion battery composite cathode material according to claim 1, characterized in that, The inorganic coating is one or more combinations of metal oxides and / or metal-like oxides; the organic coating is one or more combinations of para-, ortho-, and meta-substituted aromatic primary amine compounds.

3. The sodium-ion battery composite cathode material according to claim 2, characterized in that, The inorganic coating is one or more of the following: iron oxide, boron oxide, calcium oxide, bismuth oxide, niobium oxide, copper oxide, aluminum oxide, zinc oxide, silver oxide, strontium oxide, cerium oxide, chromium oxide, magnesium oxide, cadmium oxide, gadolinium oxide, yttrium oxide, titanium oxide, tin oxide, and tungsten oxide. The organic coating is one or more of the following: p-aminobenzenesulfonic acid, o-aminobenzenesulfonic acid, m-aminobenzenesulfonic acid, p-aminobenzoic acid, o-aminobenzoic acid, m-aminobenzoic acid, p-aminobenzonitrile, o-aminobenzonitrile, m-aminobenzonitrile, p-aminoacetophenone, o-aminoacetophenone, m-aminoacetophenone, p-aminobenzyl alcohol, o-aminobenzyl alcohol, m-aminobenzyl alcohol, p-aminobenzoarsic acid, o-aminobenzoarsic acid, m-aminobenzoarsic acid, p-aminophenol, o-aminophenol, m-aminophenol, p-methoxyaniline, o-methoxyaniline, m-methoxyaniline, p-aminobenzamide, o-aminobenzamide, m-aminobenzamide.

4. A method for preparing a sodium-ion battery composite cathode material according to any one of claims 2 to 3, characterized in that, Includes the following steps: (1) The sodium source and nickel-iron-manganese-based precursor were subjected to high-temperature calcination to obtain the matrix material; (2) Disperse the matrix material in an ethanol solution of the metal oxide and / or metal oxide-like substances, stir and mix to obtain a homogeneous solution; dry the homogeneous solution and then sinter it at high temperature to obtain an intermediate of the matrix material coated with metal oxide and / or metal oxide-like substances; (3) The aromatic primary amine compound was dissolved in an acetonitrile solution containing tert-butyl nitrite under low temperature and inert atmosphere. After mixing evenly, the intermediate was added and stirred thoroughly to react and mix evenly. Finally, the mixture was filtered, washed, and vacuum dried to obtain the sodium-ion battery composite cathode material.

5. The method for preparing the sodium-ion battery composite cathode material according to claim 4, characterized in that, The sodium source mentioned in step (1) is one or more of sodium carbonate, sodium bicarbonate, sodium acetate, and sodium oxalate; And / or, the molar ratio of the nickel-iron-manganese precursor to the sodium source is 1:1 to 1:2; And / or, the high-temperature calcination treatment is carried out at a temperature of 800~1000℃ for a time of 16~24h.

6. The method for preparing the sodium-ion battery composite cathode material according to claim 4, characterized in that, The stirring time in step (2) is 1~10 h; the drying temperature is 40~80℃ and the reaction time is 8~14 h; the sintering temperature is 150~250℃ and the reaction time is 1~5 h.

7. The method for preparing the sodium-ion battery composite cathode material according to claim 4, characterized in that, The inert atmosphere described in step (3) is nitrogen, the temperature is 0~5℃, the stirring time is 1~10 h, the vacuum drying temperature is 50~120℃, and the drying time is 7~15 h.

8. The method for preparing the sodium-ion battery composite cathode material according to claim 4, characterized in that, The inorganic coating is yttrium oxide, and the organic coating is p-aminobenzenesulfonic acid; And / or, the mass ratio of yttrium oxide to the matrix material is 1:100 to 1:1000; And / or, the mass ratio of p-aminobenzenesulfonic acid to the intermediate is 1:400 to 1:1000.

9. The method for preparing the sodium-ion battery composite cathode material according to claim 4, characterized in that, The concentration of the tert-butyl nitrite acetonitrile solution is 0.0015~0.01 g / mL.

10. A sodium-ion battery, comprising the sodium-ion battery composite cathode material according to any one of claims 1-3.

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