A tunnel-type oxide composite cathode material, its preparation method and application

Abstract

The present invention provides a tunnel-type oxide composite cathode material, a preparation method thereof and an application. The preparation method includes: (1) mixing a sodium source and a manganese source and then sintering them to obtain a tunnel-type oxide; (2) mixing the tunnel-type oxide with an organic acid, aniline and water to obtain a mixed solution; the mixed solution undergoes a polymerization reaction in the presence of an oxidant to obtain a primary product; (3) mixing the primary product with an organic solvent, followed by solid-liquid separation and oil-water separation to obtain a solid phase and an organic phase; (4) mixing and drying the solid phase and the organic phase in sequence to obtain the tunnel-type oxide composite cathode material. Through the design and synergistic effect of raw materials and process routes, the obtained tunnel-type oxide composite cathode material has significantly improved conductivity and charge-discharge specific capacity, good stability, excellent rate performance and cycling performance. The process route of the preparation method is simple, the raw materials are easily available, and it has good development prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium-ion battery materials, and particularly relates to a tunnel-type oxide composite cathode material, a preparation method thereof, and an application thereof. Background Art

[0002] Lithium batteries are efficient energy storage and conversion devices that do not rely on fossil fuels. They have many advantages such as high energy density, high power density, light weight, small size, and environmental friendliness, and have been widely used in recent years. With the rapid popularization of lithium batteries, the problems of limited lithium resource reserves and uneven geographical distribution have become increasingly prominent, resulting in an upward trend in the price of lithium materials and a gradual increase in the raw material cost of lithium batteries, seriously affecting the development of lithium batteries. Sodium and lithium are homologous elements with similar physical and chemical properties. Moreover, sodium is rich in reserves and widely distributed in the earth's crust, and its use cost is low, making it a good substitute for lithium. As a rechargeable ion battery, the sodium-ion battery has a similar working principle to the lithium-ion battery and has recently been considered promising to replace the lithium-ion battery in the future and become a new generation of energy storage devices, which are widely used in the field of large-scale energy storage. Therefore, developing room-temperature sodium-ion battery technology for large-scale energy storage applications has important strategic significance.

[0003] It is understood that the key characteristics of the battery, such as specific capacity, cycle stability, and working voltage, are mainly determined by the inherent electrochemical characteristics of the electrode material. Therefore, at the present stage, the main concern of sodium-ion batteries is to find suitable electrode materials, especially cathode materials that determine the energy density of the battery. At present, the cathode materials of sodium-ion batteries mainly include polyanion materials, Prussian blue analogs, layered oxides, tunnel-type oxides, etc. Among them, the synthesis steps of polyanion materials are generally complex, and carbon coating is required to improve their conductivity; there are bound water, interstitial water, etc. in Prussian blue analogs, which will affect the effective performance of the electrochemical properties of the cathode material; layered oxides have serious stability problems due to water absorption or reaction with water-oxygen / water-carbon dioxide, cannot be stored in air for a long time, and there are many phase transformation processes during the electrochemical cycle, with large structural changes, affecting long-term cycle stability. Compared with the other three types of cathode materials, the preparation method of tunnel-type oxides is relatively simple, with a unique S-shaped channel, which ensures structural stability during the cycle, and does not contain bound water and interstitial water, and is very stable in air and water, making it one of the most promising cathode materials.

[0004] A typical representative of tunnel-type oxides is Na 0.44MnO2 was first proposed by Hagenmuller ("Electrochemical intercalation and deintercalation of NaxMnO2 bronzes", Hagenmuller P. et al., Journal of Solid State Chemistry, 1985, 57, 323). It belongs to the orthorhombic system and consists of MnO5 square pyramids and MnO6 octahedrons to form S-shaped and pentagonal tunnels. Sodium at three different sites is in the tunnels. Later, Doeff studied the sodium storage performance of Na 0.44 MnO2 ("Orthorhombic NaxMnO2 as a Cathode Material for Secondary Sodium and Lithium Polymer Batteries", Doeff M.M. et al., Journal of Electrochemistry Society, 1994, 141). It has reversible sodium storage performance and good structural stability, but its discharge capacity is not high and its rate performance is poor. In order to improve the electrochemical performance of tunnel-type oxides, researchers modified them by changing the phase structure. For example, CN113140724A discloses a synthesis method of sodium manganese oxide, a cathode material for sodium-ion batteries with a tunnel-layered symbiotic phase. First, NaHCO3 or Na2CO3, NaF, and MnCO3 are ball-milled and mixed to obtain a uniformly mixed precursor, and then the precursor is subjected to high-temperature solid-phase sintering at 800-900 °C to obtain a fluorine-containing sodium-ion cathode material with a tunnel-layered symbiotic phase. CN114447300A discloses a preparation method of a cathode material for sodium-ion batteries with a composite structure of tunnel phase and layered phase. The steps are as follows: (1) A sodium source compound and a manganese source compound are mixed to obtain a mixed powder, and the molar ratio of sodium to manganese is 0.52-0.55:1, and sodium is in excess by 3% based on this molar ratio; (2) The mixed powder obtained in step (1) is sintered twice. The temperature of the first sintering is 400-600 °C, and the temperature of the second sintering is 800-1000 °C; this method forms a two-phase structure by regulating the content of sodium, and the tunnel phase is the main phase and the layered phase is less in the synthesized material. Although the composite structure of the tunnel phase and the layered phase can combine the characteristics of the two phases to a certain extent and improve the capacity and stability of the material, the problem of excessive irreversible capacity in the first cycle and low Coulomb efficiency of tunnel-type oxides has not been well solved; moreover, tunnel-type oxides have the problem of insufficient conductivity, which further affects their rate performance.

[0005] Therefore, improving the electrochemical performance of tunnel-type oxides, especially improving their conductivity and material utilization efficiency, is the research focus in this field. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a tunnel-type oxide composite cathode material, a preparation method thereof and an application thereof. Through the design and synergistic cooperation of raw materials and process routes, a uniform, complete and stable polyaniline coating layer is formed on the surface of the tunnel-type oxide, so that the obtained tunnel-type oxide has excellent conductivity and first-cycle discharge specific capacity, high material utilization efficiency, and significantly improved electrochemical performance.

[0007] To achieve this purpose, the present invention adopts the following technical solutions:

[0008] In the first aspect, the present invention provides a preparation method of a tunnel-type oxide composite cathode material, and the preparation method includes the following steps:

[0009] (1) Mix a sodium source and a manganese source and then sinter them to obtain a tunnel-type oxide;

[0010] (2) Mix the tunnel-type oxide obtained in step (1) with an organic acid, aniline and water to obtain a mixed solution; the mixed solution undergoes a polymerization reaction in the presence of an oxidant to obtain a primary product;

[0011] (3) After mixing the primary product obtained in step (2) with an organic solvent, perform solid-liquid separation and oil-water separation to obtain a solid phase and an organic phase;

[0012] (4) Mix and dry the solid phase and the organic phase obtained in step (3) in sequence to obtain the tunnel-type oxide composite cathode material.

[0013] In the preparation method provided by the present invention, the tunnel-type oxide is obtained by a solid-phase method in step (1). In step (2), the tunnel-type oxide is mixed with aniline, an organic acid and water and dispersed evenly to form an emulsion-like mixed solution; in the presence of an oxidant, aniline monomers (An) undergo in-situ oxidative polymerization coating on the surface of the tunnel-type oxide to form a polyaniline coating layer, and the primary product is obtained; in step (3), the primary product is mixed with an organic solvent and demulsified, and the polyaniline not coated on the surface of the tunnel-type oxide in the system is extracted into the liquid phase (organic phase), and the tunnel-type oxide that has completed in-situ oxidative polymerization coating precipitates, which is the solid phase. At this time, the system is divided into a solid-liquid two-phase, and the liquid phase is further divided into an organic phase (oil phase) and an aqueous phase; after solid-liquid separation and oil-water separation, in step (4), the obtained solid phase and organic phase are mixed evenly and dried, so that the polyaniline in the organic phase deposits and interacts with the solid phase (the tunnel-type oxide that has completed polymerization coating), making the polyaniline coating layer on the surface of the tunnel-type oxide more uniform and complete.

[0014] The present invention first prepares tunnel-type oxides by a solid-phase method, which has low agglomeration degree and good uniformity. Then, aniline monomers are introduced, and a process route including two coating processes is designed. Through the design and compounding synergy of raw materials and process routes, a polyaniline coating layer with uniform performance, uniform thickness and complete structure is formed on the surface of the tunnel-type oxides. The polyaniline coating layer has good conductivity and can significantly improve the conductivity of the tunnel-type oxide composite cathode material. At the same time, the polyaniline coating layer has excellent uniformity and can provide a protective effect for the tunnel-type oxides, reducing the contact between the tunnel-type oxides and the electrolyte and decreasing the occurrence probability of side reactions, thereby improving the cycle performance of the material. Moreover, a layer of organic polymer material (polyaniline) is coated on the surface of the tunnel-type oxides, and based on the structural characteristics of the polymer material, the physical properties such as the strength and toughness of the tunnel-type oxide composite cathode material can be increased. Therefore, the tunnel-type oxide composite cathode material prepared by the present invention has significantly improved conductivity and first-cycle charge-discharge specific capacity, higher material utilization efficiency, good stability, and excellent rate performance and cycle performance. The process route of the preparation method is simple, the raw materials are easy to obtain, the cost is low, continuous and large-scale production can be realized, and it has broad application prospects.

[0015] Preferably, the sodium source in step (1) includes sodium hydroxide and / or sodium salts.

[0016] Preferably, the sodium source in step (1) includes any one or a combination of at least two of sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium acetate, sodium sulfate, sodium nitrate, and sodium chloride.

[0017] Preferably, the manganese source in step (1) includes manganese oxides and / or manganese salts.

[0018] Preferably, the manganese oxides include any one or a combination of at least two of MnO, MnO2, Mn2O3, and Mn3O4.

[0019] Preferably, the manganese salts include any one or a combination of at least two of manganese carbonate, manganese sulfate, manganese chloride, manganese nitrate, and manganese acetate; the manganese salts may optionally contain water of crystallization.

[0020] In the present invention, the dosages of the sodium source and the manganese source are determined according to the stoichiometric ratio of Na to Mn in the tunnel-type oxides.

[0021] Preferably, the sodium source can be added in excess relative to the manganese source.

[0022] Preferably, the molar ratio of sodium in the sodium source to manganese in the manganese source in step (1) is (0.2 - 0.51):1, and for example, it can be 0.22:1, 0.25:1, 0.28:1, 0.3:1, 0.32:1, 0.35:1, 0.38:1, 0.4:1, 0.42:1, 0.45:1, 0.48:1 or 0.5:1, etc.

[0023] Preferably, before the mixing in step (1), the sodium source and the manganese source are each independently subjected to an optional pretreatment step to control the particle size of the material and release the agglomerated particles into a homogeneous material for subsequent mixing (ball milling).

[0024] Preferably, the mixing method in step (1) is ball milling, and further preferably wet ball milling.

[0025] As a preferred technical solution of the present invention, the sodium source and the manganese source are fully and evenly mixed by wet ball milling to achieve uniform element distribution and facilitate the formation of a target product (tunnel-type oxide) with a fixed ratio; compared with dry ball milling, the present invention preferably uses wet ball milling, which can avoid problems such as wall sticking, ball sticking, uneven material mixing, and excessive element distribution differentiation, enabling the sodium source and the manganese source to be more fully mixed and the elements to be evenly distributed; during the wet ball milling process, under the action of the mechanical energy of ball milling, the raw materials (sodium source and manganese source) are evenly mixed, the particle size is refined, the surface of the material is activated, reducing the reaction barrier between the raw materials and contributing to the occurrence of subsequent solid-phase reactions at a relatively low temperature.

[0026] Preferably, the ball milling is carried out in the presence of an organic solvent (wet ball milling), and the organic solvent includes an alcohol solvent and / or a ketone solvent.

[0027] Preferably, the alcohol solvent includes any one or a combination of at least two of methanol, ethanol, n-propanol, and isopropanol, and further preferably ethanol.

[0028] Preferably, the ketone solvent includes acetone and / or methyl ethyl ketone, and further preferably acetone.

[0029] Preferably, based on the total mass of the sodium source and the manganese source being 100%, the mass of the organic solvent is 100 - 150%, and for example, it can be 105%, 110%, 115%, 120%, 125%, 130%, 135%, 140% or 145%, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0030] Preferably, the rotation speed of the ball milling is 200 - 600 rpm. For example, it can be 220 rpm, 250 rpm, 280 rpm, 300 rpm, 320 rpm, 350 rpm, 380 rpm, 400 rpm, 420 rpm, 450 rpm, 480 rpm, 500 rpm, 520 rpm, 550 rpm or 580 rpm, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range. Further preferably, it is 300 - 550 rpm.

[0031] Preferably, the time of the ball milling is 2 - 5 h. For example, it can be 2.5 h, 3 h, 3.5 h, 4 h or 4.5 h, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0032] Preferably, after the ball milling, a drying step is further included.

[0033] Preferably, the temperature of the drying is 60 - 100 °C. For example, it can be 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, 90 °C or 95 °C, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0034] Preferably, the time of the drying is 0.5 - 6 h. For example, it can be 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h or 5.5 h, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0035] Preferably, the sintering in step (1) is carried out in an aerobic atmosphere, and more preferably in an air atmosphere.

[0036] Preferably, the temperature of the sintering in step (1) is 700 - 950 °C. For example, it can be 720 °C, 750 °C, 780 °C, 800 °C, 850 °C, 880 °C, 900 °C, 920 °C or 940 °C, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0037] Preferably, the time of the sintering in step (1) is 3 - 24 h. For example, it can be 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 15 h, 17 h, 19 h, 20 h or 22 h, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range. Further preferably, it is 3 - 18 h.

[0038] As a preferred technical solution of the present invention, in step (1), a method of first ball-milling and mixing and then sintering is adopted to obtain a tunnel-type oxide by a solid-phase method. The ball-milling process realizes the activation treatment of the material, which can effectively reduce the temperature and time of the solid-phase reaction (sintering), with low energy consumption; and no waste liquid or waste gas is generated during the preparation process, which conforms to the concept of green chemistry and meets the needs of developing an environmentally friendly and resource-saving economy. The degree of agglomeration of the tunnel-type oxide obtained in step (1) is low, and it has controllable particle size and excellent uniformity.

[0039] Preferably, after the sintering in step (1), steps of crushing and screening are further included.

[0040] Preferably, the sieve mesh for screening is a 300-mesh sieve mesh.

[0041] Preferably, the organic acid in step (2) is dodecylbenzenesulfonic acid.

[0042] As a preferred technical solution of the present invention, the organic acid is dodecylbenzenesulfonic acid (DBSA), which is an organic protonic acid. Compared with inorganic protonic acids (such as hydrochloric acid, sulfuric acid, and phosphoric acid, etc.), DBSA has good environmental stability, is not prone to migration, and will not affect the polarity in the molecular chain of the formed polyaniline (PANI) after doping; moreover, as an organic sulfonic acid, DBSA contains both polar and non-polar groups in its molecular structure, has a relatively large molecular weight, and has greatly improved conductivity and solubility, etc. Its use in the in-situ oxidative polymerization of aniline on the surface of the tunnel-type oxide is conducive to the formation of a uniform polyaniline coating layer with a high yield, so that the obtained tunnel-type oxide composite cathode material has significantly improved conductivity, charge-discharge capacity, and cycle stability.

[0043] Preferably, the molar ratio of the organic acid to aniline in step (2) is (0.5 - 1.0):1, for example, it can be 0.55:1, 0.6:1, 0.65:1, 0.7:1, 0.75:1, 0.8:1, 0.85:1, 0.9:1, or 0.95:1, etc.

[0044] Preferably, in step (2), based on the mass of the organic acid (preferably DBSA) being 1 g, the volume of the water is 100 - 500 mL, for example, it can be 150 mL, 200 mL, 250 mL, 300 mL, 350 mL, 400 mL, or 450 mL, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range, and 200 - 400 mL is further preferred.

[0045] Preferably, the mass ratio of the tunnel-type oxide to aniline in step (2) is 1:(0.01 - 0.1), for example, it can be 1:0.02, 1:0.03, 1:0.04, 1:0.05, 1:0.06, 1:0.07, 1:0.08, or 1:0.09, etc.

[0046] As a preferred technical solution of the present invention, the mass ratio of the tunnel-type oxide to aniline is 1:(0.01 - 0.1). Aniline undergoes a polymerization reaction in the presence of an organic acid and an oxidant to form an in-situ polymerization coating on the surface of the tunnel-type oxide, and through the treatment steps of steps (3) and (4), the effect of secondary coating is formed, so that the obtained tunnel-type oxide composite cathode material contains a polyaniline coating layer with uniform properties and thickness, complete and stable structure. The tunnel-type oxide composite cathode material has excellent electrical conductivity, first-cycle charge-discharge specific capacity and stability, and excellent electrochemical performance. If the dosage of aniline monomer is too small, a uniform polyaniline coating layer cannot be obtained, and the conductivity and stability of the tunnel-type oxide cannot be effectively improved; if the dosage of aniline monomer is too large, the polyaniline layer coated on the surface of the tunnel-type oxide will be too thick. The thick polyaniline coating layer can provide a physical barrier between the cathode and the electrolyte, but it will also hinder the diffusion of sodium during the insertion and extraction process, resulting in low capacity of the material; in addition, too high monomer dosage also increases the overall cost of the material.

[0047] Preferably, the oxidant in step (2) is persulfate, and ammonium persulfate is further preferred.

[0048] As a preferred technical solution of the present invention, the oxidant is ammonium persulfate (APS), which has strong oxidation ability, does not contain metal ions, and is easy to handle.

[0049] Preferably, the molar ratio of the oxidant to aniline in step (2) is (0.5 - 2.0):1, for example, it can be 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, or 1.9:1, etc.

[0050] Preferably, in step (2), after mixing the tunnel-type oxide, organic acid and water evenly, aniline is added thereto, mixed and dispersed evenly to form an emulsion-like mixture; an oxidant is added to the mixture and a polymerization reaction is carried out to obtain a primary product.

[0051] Preferably, the oxidant is added to the mixture in the form of its aqueous solution.

[0052] Preferably, the addition method of the oxidant is dropwise addition.

[0053] Preferably, the polymerization reaction in step (2) is carried out in the presence of a protective atmosphere.

[0054] Preferably, the protective atmosphere includes any one or a combination of at least two of a nitrogen atmosphere, an argon atmosphere, and a helium atmosphere.

[0055] Preferably, the temperature of the polymerization reaction in step (2) is 15 - 40 °C, for example, it can be 16 °C, 18 °C, 20 °C, 22 °C, 25 °C, 28 °C, 30 °C, 32 °C, 35 °C, or 38 °C, as well as the specific point values between the above point values. Due to space limitations and for the sake of brevity, the specific point values included in the scope of the present invention are not exhaustively listed. Further preferably, it is at room temperature.

[0056] Preferably, the time of the polymerization reaction in step (2) is 6 - 8 h, for example, it can be 6.25 h, 6.5 h, 6.75 h, 7 h, 7.25 h, 7.5 h, or 7.75 h, as well as the specific point values between the above point values. Due to space limitations and for the sake of brevity, the specific point values included in the scope of the present invention are not exhaustively listed.

[0057] Preferably, the organic solvent in step (3) includes any one or a combination of at least two of dichloromethane, chloroform, carbon tetrachloride, chlorobenzene, and dichlorobenzene. Further preferably, it is chloroform.

[0058] Preferably, the volume ratio of the crude product to the organic solvent in step (3) is 1:(0.1 - 2.0), for example, it can be 1:0.2, 1:0.3, 1:0.5, 1:0.6, 1:0.8, 1:1, 1:1.1, 1:1.3, 1:1.5, 1:1.7, or 1:1.9, etc. Further preferably, it is 1:(1.0 - 1.0).

[0059] In the present invention, the crude product is an emulsion system. After mixing it with the organic solvent, demulsification occurs. The free polyaniline that is not coated on the surface of the tunnel - type oxide in the crude product is extracted into the organic phase. After standing and separating into layers, the system is divided into a solid - liquid two - phase. The tunnel - type oxide that has completed in - situ oxidative polymerization coating forms a precipitate (i.e., the solid phase), and the liquid phase is further divided into an aqueous phase and an organic phase (oil phase); after solid - liquid separation and oil - water separation, the solid phase (preliminarily coated tunnel - type oxide) and the organic phase are obtained respectively, and the organic phase contains polyaniline.

[0060] In the present invention, the order of the solid - liquid separation and the oil - water separation is not particularly limited. The precipitate (solid phase, tunnel - type oxide that has completed in - situ oxidative polymerization coating) can be separated from the liquid phase first, and then the organic phase and the aqueous phase in the liquid phase can be separated.

[0061] Preferably, the solid phase and the organic phase obtained by the solid - liquid separation and the oil - water separation in step (3) each independently undergo a washing step.

[0062] Preferably, the mixing in step (4) is carried out under stirring conditions.

[0063] Preferably, the mixing time in step (4) is 0.1 - 12 h, for example, it can be 0.2 h, 0.3 h, 0.4 h, 0.5 h, 0.6 h, 0.8 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h or 11 h, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the said range. Further preferably, it is 0.1 - 1 h.

[0064] Preferably, the drying method in step (4) is vacuum drying.

[0065] Preferably, the drying temperature in step (4) is 60 - 100 °C, for example, it can be 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, 90 °C or 95 °C, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the said range. Further preferably, it is 60 - 80 °C.

[0066] Preferably, the drying time in step (4) is 12 - 48 h, for example, it can be 14 h, 16 h, 18 h, 20 h, 24 h, 28 h, 30 h, 32 h, 36 h, 40 h or 44 h, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the said range. Further preferably, it is 24 - 48 h.

[0067] As a preferred technical solution of the present invention, in step (4), first, the solid phase and the organic phase are fully and uniformly mixed under stirring conditions, and then they are placed in an environment of 60 - 100 °C for drying. The mixing and drying steps enable the polyaniline originally dispersed in the organic phase to perform secondary coating on the tunnel - type oxide that has completed in - situ oxidative polymerization coating, so that the obtained tunnel - type oxide composite cathode material has a polyaniline coating layer with uniform thickness, uniform properties, complete coating structure and good binding property, endowing it with excellent conductivity, charge - discharge specific capacity, rate performance, cycle stability and material utilization efficiency.

[0068] Preferably, after the drying in step (4), a screening step is further included.

[0069] Preferably, the sieve for screening is a 300 - mesh sieve.

[0070] Preferably, the preparation method specifically includes the following steps:

[0071] (1) Mix the sodium source and the manganese source by wet ball - milling, and the mixed material is dried and sintered to obtain a tunnel - type oxide;

[0072] Among them, the rotation speed of the wet ball milling is 200 - 600 rpm, and the time is 2 - 5 h;

[0073] The sintering is carried out in an aerobic atmosphere, the temperature is 700 - 950 °C, and the time is 3 - 24 h;

[0074] (2) Mix the tunnel - type oxide obtained in step (1) with dodecylbenzenesulfonic acid, aniline, and water to obtain a mixed solution; the mixed solution undergoes a polymerization reaction in the presence of an oxidant to obtain a primary product;

[0075] Among them, the mass ratio of the tunnel - type oxide to aniline is 1:(0.01 - 0.1), and the molar ratio of dodecylbenzenesulfonic acid, oxidant, and aniline is (0.5 - 1.0):(0.5 - 2.0):1;

[0076] The polymerization reaction is carried out in a protective atmosphere, the temperature is 15 - 40 °C, and the time is 6 - 8 h;

[0077] (3) Demulsify the primary product obtained in step (2) with an organic solvent, and perform solid - liquid separation and oil - water separation on the stratified system to obtain a solid phase, an organic phase, and an aqueous phase; the volume ratio of the primary product to the organic solvent is 1:(0.1 - 2.0);

[0078] (4) Mix the solid phase and the organic phase obtained in step (3) evenly, and dry them at 60 - 100 °C for 12 - 48 h to obtain the tunnel - type oxide composite cathode material.

[0079] In a second aspect, the present invention provides a tunnel - type oxide composite cathode material, which is prepared by the preparation method as described in the first aspect.

[0080] Preferably, the tunnel - type oxide composite cathode material is a tunnel - type oxide coated with polyaniline, and the chemical formula of the tunnel - type oxide is NaxMnO2.

[0081] Among them, 0 < x < 0.5, for example, x is 0.1, 0.2, 0.3, 0.35, 0.4, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, or 0.49, as well as the specific point values between the above - mentioned point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list all the specific point values included in the range.

[0082] In a preferred technical solution, the tunnel - type oxide is Na 0.44 MnO2.

[0083] Preferably, the particle size of the tunnel-type oxide composite cathode material is <80 μm, and for example, it can be 0.1 μm, 0.5 μm, 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm or 75 μm, etc. Further preferably, it is <60 μm, more preferably ≤50 μm, and most preferably ≤20 μm.

[0084] The tunnel-type oxide composite cathode material provided by the present invention has significantly improved conductivity, charge-discharge capacity and stability, excellent rate performance and cycle performance, and significantly improved material utilization efficiency.

[0085] Preferably, the specific capacity of the tunnel-type oxide composite cathode material at 0.1C is ≥115 mAh / g, further preferably ≥116 mAh / g, and can reach 116.34 - 133.01 mAh / g.

[0086] Preferably, the specific capacity of the tunnel-type oxide composite cathode material at 0.5C is >100 mAh / g, further preferably ≥110 mAh / g, and can reach 110.05 - 128.34 mAh / g.

[0087] Preferably, the specific capacity of the tunnel-type oxide composite cathode material at 1.0C is >95 mAh / g, further preferably ≥98 mAh / g, and can reach 98.78 - 113.18 mAh / g.

[0088] Preferably, the specific capacity of the tunnel-type oxide composite cathode material at 2.0C is >85 mAh / g, further preferably ≥87 mAh / g, more preferably ≥91 mAh / g, and can reach 91.03 - 106.23 mAh / g.

[0089] Preferably, the specific capacity of the tunnel-type oxide composite cathode material at 5.0C is >80 mAh / g, further preferably ≥83 mAh / g, and can reach 83.93 - 101.26 mAh / g.

[0090] In the third aspect, the present invention provides an application of the tunnel-type oxide composite cathode material as described in the second aspect in an electrochemical device.

[0091] Preferably, the electrochemical device includes a sodium-ion battery or a capacitor.

[0092] Preferably, the tunnel-type oxide composite cathode material is applied as a positive electrode active material of a sodium-ion battery.

[0093] Fourthly, the present invention provides a sodium-ion battery, which includes the tunnel-type oxide composite cathode material as described in the second aspect.

[0094] Compared with the prior art, the present invention has the following beneficial effects:

[0095] (1) In the preparation method provided by the present invention, first, a tunnel-type oxide is prepared by a solid-phase method, and then aniline monomer is introduced, and a process route including two coating processes is designed. Through the design and synergistic effect of raw materials and process routes, a polyaniline coating layer with uniform performance, uniform thickness, and complete structure is formed on the surface of the tunnel-type oxide, so that the obtained tunnel-type oxide composite cathode material has significantly improved conductivity and first-cycle charge-discharge specific capacity, higher material utilization efficiency, good stability, and excellent rate performance and cycle performance.

[0096] (2) The process route of the preparation method is simple, the raw materials are easy to obtain, the cost is low, continuous and large-scale production can be realized, and it has good development prospects and market value.

[0097] (2) The tunnel-type oxide composite cathode material has excellent electrochemical performance, especially high conductivity, high charge-discharge capacity, and high stability, and has excellent performance in rate performance and cycle stability. As a positive active material, it effectively improves the rate performance and cycle performance of the sodium-ion battery, and the retention rate after 300 cycles at 0.5C is ≥85%. Detailed Embodiments

[0098] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0099] As used herein, the terms "comprising", "including", "having", "containing" or any other variation thereof are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or device containing the listed elements is not necessarily limited to those elements, but may also include other elements not expressly listed or elements inherent to such composition, step, method, article, or device.

[0100] "Optionally" or "any one" means that the subsequent described matter or event may or may not occur, and the description includes the case where the event occurs and the case where the event does not occur.

[0101] The indefinite articles "a" and "an" before the elements or components of the present invention do not limit the quantity requirements (i.e., the number of occurrences) of the elements or components. Therefore, "a" or "an" should be construed as including one or at least one, and the singular form of the element or component also includes the plural form, unless the quantity clearly refers only to the singular form.

[0102] The description of terms such as "one embodiment", "some embodiments", "exemplarily", "specific example", or "some examples" in the present invention means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this document, the schematic expressions of the above terms are not necessarily directed to the same embodiment or example.

[0103] Moreover, the technical features involved in each embodiment of the present invention can be combined with each other as long as they do not conflict with each other.

[0104] Embodiment 1

[0105] A tunnel-type oxide composite cathode material and a preparation method thereof, the preparation method comprising the following steps:

[0106] (1) Take appropriate amounts of Na2CO3 and MnCO3, perform grinding pretreatment, and set aside; feed Na2CO3 and MnCO3 in a molar ratio of 0.250:1, perform simple uniform mixing in a mixer, transfer to a zirconia ball mill jar, add ethanol solvent, and perform ball milling at 300 rpm for 3 h. After collecting and drying the ball-milled product, transfer it to a muffle furnace and sinter at 850 °C in air atmosphere for 15 h. After sintering, cool with the furnace to obtain a tunnel-type oxide with the chemical formula Na 0.44 MnO2;

[0107] (2) Prepare the tunnel-type oxide obtained in step (1) and aniline (An) in a mass ratio of 1:0.06; prepare Dodecylbenzenesulfonic acid (DBSA) and An in a molar ratio of 0.75:1, and ammonium persulfate (APS) and An in a molar ratio of 1:1;

[0108] In a nitrogen atmosphere, mix the tunnel-type oxide, DBSA, and 300 mL of deionized water obtained in step (1), add An thereto and disperse evenly to obtain an emulsion-like mixture; slowly drop the APS solution into the above mixture, stop stirring after stirring and polymerizing at room temperature for 7 h to obtain a primary product;

[0109] (3) Add 100 mL of chloroform to the primary product (400 mL) obtained in step (2) for demulsification and extraction. After standing and separating into layers, perform solid-liquid separation. Wash the obtained solid phase (precipitate) and set aside; perform oil-water separation on the obtained liquid phase, retain the organic phase (polyaniline extraction solution), wash it and set aside;

[0110] (4) Mix the organic phase and the solid phase obtained in step (3), stir at room temperature for 40 min to mix evenly, and then place it in a vacuum oven and dry at 80 °C under vacuum for 24 h to obtain the tunnel-type oxide composite cathode material.

[0111] Example 2

[0112] A tunnel-type oxide composite cathode material and a preparation method thereof. The preparation method includes the following steps:

[0113] (1) Take appropriate amounts of Na2CO3 and MnCO3, perform grinding pretreatment, and set aside. Feed Na2CO3 and MnCO3 in a molar ratio of 0.250:1, perform simple uniform mixing in a mixer, transfer to a zirconia ball milling tank, add acetone solvent, and perform ball milling at 300 rpm for 3 h. After collecting and drying the ball-milled product, transfer it to a muffle furnace and sinter at 850 °C in air atmosphere for 15 h. After sintering, cool with the furnace to obtain a tunnel-type oxide with the chemical formula Na 0.44 MnO2;

[0114] (2) Prepare the tunnel-type oxide obtained in step (1) and An in a mass ratio of 1:0.06; prepare DBSA and An in a molar ratio of 0.65:1 and APS and An in a molar ratio of 1:1;

[0115] In a nitrogen atmosphere, mix the tunnel-type oxide, DBSA, and 300 mL of deionized water obtained in step (1), add An thereto and disperse evenly to obtain an emulsion-like mixture; slowly drop the APS solution into the above mixture, stop stirring after stirring and polymerizing at room temperature for 7 h to obtain a primary product;

[0116] (3) Add 100 mL of chloroform to the primary product (400 mL) obtained in step (2) for demulsification and extraction. After standing and separating layers, perform solid-liquid separation. Wash the obtained solid phase (precipitate) and set aside; perform oil-water separation on the obtained liquid phase, retain the organic phase (polyaniline extract), wash it and set aside;

[0117] (4) Mix the organic phase and the solid phase obtained in step (3), stir at room temperature for 40 min to mix evenly, and then place it in a vacuum oven for vacuum drying at 80 °C for 24 h to obtain the tunnel-type oxide composite cathode material.

[0118] Example 3

[0119] A tunnel-type oxide composite cathode material and a preparation method thereof. The preparation method includes the following steps:

[0120] (1) Take appropriate amounts of Na2CO3 and MnCO3, conduct grinding pretreatment, and set aside. Feed Na2CO3 and MnCO3 in a molar ratio of 0.250:1, conduct simple uniform mixing in a mixer, transfer to a zirconia ball mill tank, add ethanol solvent, and conduct ball milling treatment at 300 rpm for 3 h. After collecting and drying the ball-milled product, transfer it to a muffle furnace and sinter in air atmosphere at 850 °C for 15 h. After the sintering is completed, cool it with the furnace to obtain a tunnel-type oxide with the chemical formula Na 0.44 MnO2;

[0121] (2) Prepare the tunnel-type oxide obtained in step (1) and An in a mass ratio of 1:0.06; prepare materials in a ratio where the molar ratio of DBSA to An is 0.90:1 and the molar ratio of APS to An is 1:1;

[0122] In a nitrogen atmosphere, mix the tunnel-type oxide, DBSA, and 300 mL of deionized water obtained in step (1), add An thereto and disperse evenly to obtain an emulsion-like mixture; slowly drop the APS solution into the above mixture, stop stirring after stirring and polymerizing at room temperature for 7 h to obtain a primary product;

[0123] (3) Add 100 mL of chloroform to the primary product (400 mL) obtained in step (2) for demulsification and extraction. After standing and separating into layers, conduct solid-liquid separation. Wash the obtained solid phase (precipitate) and set aside; conduct oil-water separation on the obtained liquid phase, retain the organic phase (polyaniline extraction solution), wash it, and set aside;

[0124] (4) Mix the organic phase and the solid phase obtained in step (3), stir at room temperature for 40 min to mix evenly, and then place it in a vacuum oven and dry it under vacuum at 80 °C for 24 h to obtain the tunnel-type oxide composite cathode material.

[0125] Example 4

[0126] A tunnel-type oxide composite cathode material and a preparation method thereof, the preparation method comprising the following steps:

[0127] (1) Take appropriate amounts of Na2CO3 and MnCO3, conduct grinding pretreatment, and set aside. Feed Na2CO3 and MnCO3 in a molar ratio of 0.250:1, conduct simple uniform mixing in a mixer, transfer to a zirconia ball mill tank, add ethanol solvent, and conduct ball milling treatment at 300 rpm for 3 h. After collecting and drying the ball-milled product, transfer it to a muffle furnace and sinter in air atmosphere at 850 °C for 15 h. After the sintering is completed, cool it with the furnace to obtain a tunnel-type oxide with the chemical formula Na 0.44 MnO2;

[0128] (2) Prepare the tunnel-type oxide obtained in step (1) and An in a mass ratio of 1:0.06; prepare materials in a ratio where the molar ratio of DBSA to An is 0.75:1 and the molar ratio of APS to An is 0.55:1;

[0129] In a nitrogen atmosphere, mix the tunnel-type oxide, DBSA, and 300 mL of deionized water obtained in step (1), then add An thereto and disperse evenly to obtain an emulsion-like mixture; slowly drip the APS solution into the above mixture, stop stirring after stirring for 7 h at room temperature for the polymerization reaction to obtain a primary product;

[0130] (3) Add 100 mL of chloroform to the primary product (400 mL) obtained in step (2) for demulsification and extraction. After standing and separating into layers, perform solid-liquid separation. The obtained solid phase (precipitate) is washed and reserved; perform oil-water separation on the obtained liquid phase, retain the organic phase (polyaniline extract), and wash and reserve it;

[0131] (4) Mix the organic phase and the solid phase obtained in step (3), stir at room temperature for 40 min to mix evenly, and then place it in a vacuum oven for vacuum drying at 80 °C for 24 h to obtain the tunnel-type oxide composite cathode material.

[0132] Example 5

[0133] A tunnel-type oxide composite cathode material and a preparation method thereof. The preparation method includes the following steps:

[0134] (1) Take appropriate amounts of Na2CO3 and MnCO3, perform grinding pretreatment, and then reserve; feed Na2CO3 and MnCO3 in a molar ratio of 0.250:1, perform simple uniform mixing in a mixer, and then transfer to a zirconia ball milling tank, and add an ethanol solvent. Perform ball milling at 300 rpm for 3 h. The product after ball milling is collected, dried, and then transferred to a muffle furnace for sintering at 850 °C for 15 h in an air atmosphere. After sintering, cool with the furnace to obtain a tunnel-type oxide with the chemical formula Na 0.44 MnO2;

[0135] (2) Prepare the tunnel-type oxide obtained in step (1) and An in a mass ratio of 1:0.06; prepare materials in a ratio where the molar ratio of DBSA to An is 0.75:1 and the molar ratio of APS to An is 1.45:1;

[0136] In a nitrogen atmosphere, mix the tunnel-type oxide, DBSA, and 300 mL of deionized water obtained in step (1), then add An thereto and disperse evenly to obtain an emulsion-like mixture; slowly drip the APS solution into the above mixture, stop stirring after stirring for 7 h at room temperature for the polymerization reaction to obtain a primary product;

[0137] (3) Add 100 mL of chloroform to the crude product (400 mL) obtained in step (2) for demulsification and extraction. After standing for phase separation, perform solid-liquid separation. The obtained solid phase (precipitate) is washed and reserved; perform oil-water separation on the obtained liquid phase, retain the organic phase (polyaniline extraction solution), and wash and reserve it;

[0138] (4) Mix the organic phase obtained in step (3) with the solid phase, stir at room temperature for 40 min to mix evenly, and then place it in a vacuum oven for vacuum drying at 80 °C for 24 h to obtain the tunnel-type oxide composite cathode material.

[0139] Example 6

[0140] A tunnel-type oxide composite cathode material and a preparation method thereof. The preparation method includes the following steps:

[0141] (1) Take appropriate amounts of Na2CO3 and MnCO3, perform grinding pretreatment, and reserve; Charge Na2CO3 and MnCO3 in a molar ratio of 0.250:1, perform simple uniform mixing in a mixer, then transfer to a zirconia ball milling tank, add an ethanol solvent, and perform ball milling at 300 rpm for 3 h. After collecting and drying the ball-milled product, transfer it to a muffle furnace and sinter in air at 850 °C for 15 h. After sintering, cool with the furnace to obtain a tunnel-type oxide with the chemical formula Na 0.44 MnO2;

[0142] (2) Prepare the tunnel-type oxide obtained in step (1) and An in a mass ratio of 1:0.01; Prepare DBSA and An in a molar ratio of 0.75:1 and APS and An in a molar ratio of 1:1;

[0143] In a nitrogen atmosphere, mix the tunnel-type oxide, DBSA, and 300 mL of deionized water obtained in step (1), add An thereto and disperse evenly to obtain an emulsion-like mixture; Slowly drop the APS solution into the above mixture, stop stirring after stirring and polymerizing at room temperature for 7 h to obtain a crude product;

[0144] (3) Add 100 mL of chloroform to the crude product (400 mL) obtained in step (2) for demulsification and extraction. After standing for phase separation, perform solid-liquid separation. The obtained solid phase (precipitate) is washed and reserved; perform oil-water separation on the obtained liquid phase, retain the organic phase (polyaniline extraction solution), and wash and reserve it;

[0145] (4) Mix the organic phase obtained in step (3) with the solid phase, stir at room temperature for 40 min to mix evenly, and then place it in a vacuum oven for vacuum drying at 80 °C for 24 h to obtain the tunnel-type oxide composite cathode material.

[0146] Example 7

[0147] A tunnel-type oxide composite cathode material and a preparation method thereof, the preparation method comprising the following steps:

[0148] (1) Take appropriate amounts of Na2CO3 and MnCO3, perform grinding pretreatment, and set aside; feed Na2CO3 and MnCO3 in a molar ratio of 0.250:1, perform simple uniform mixing in a mixer, transfer to a zirconia ball mill jar, add an ethanol solvent, and perform ball milling at 300 rpm for 3 h. After collecting and drying the ball-milled product, transfer it to a muffle furnace and sinter at 850 °C in an air atmosphere for 15 h. After the sintering is completed, cool it with the furnace to obtain a tunnel-type oxide with the chemical formula Na 0.44 MnO2;

[0149] (2) Prepare the tunnel-type oxide obtained in step (1) and An in a mass ratio of 1:0.1; prepare DBSA and An in a molar ratio of 0.75:1 and APS and An in a molar ratio of 1:1;

[0150] In a nitrogen atmosphere, mix the tunnel-type oxide, DBSA, and 300 mL of deionized water obtained in step (1), add An thereto and disperse evenly to obtain an emulsion-like mixture; slowly drop the APS solution into the above mixture, stop stirring after stirring and polymerizing at room temperature for 7 h to obtain a primary product;

[0151] (3) Add 100 mL of chloroform to the primary product (400 mL) obtained in step (2) for demulsification and extraction. After standing and separating the layers, perform solid-liquid separation. Wash the obtained solid phase (precipitate) and set aside; perform oil-water separation on the obtained liquid phase, retain the organic phase (polyaniline extraction solution), wash it, and set aside;

[0152] (4) Mix the organic phase and the solid phase obtained in step (3), stir at room temperature for 40 min to mix evenly, and then place it in a vacuum oven and dry it at 80 °C under vacuum for 24 h to obtain the tunnel-type oxide composite cathode material.

[0153] Example 8

[0154] A tunnel-type oxide composite cathode material and a preparation method thereof, the preparation method comprising the following steps:

[0155] (1) Take appropriate amounts of Na2CO3 and MnCO3, conduct grinding pretreatment, and set aside. Feed Na2CO3 and MnCO3 in a molar ratio of 0.250:1, conduct simple uniform mixing in a mixer, transfer to a zirconia ball mill jar, add ethanol solvent, and conduct ball milling treatment at 300 rpm for 3 h. After collecting and drying the ball-milled product, transfer it to a muffle furnace and sinter at 850 °C in air atmosphere for 15 h. After the sintering is completed, cool it with the furnace to obtain a tunnel-type oxide with the chemical formula Na 0.44 MnO2;

[0156] (2) Prepare the tunnel-type oxide obtained in step (1) and An in a mass ratio of 1:0.12; prepare materials in a ratio where the molar ratio of DBSA to An is 0.75:1 and the molar ratio of APS to An is 1:1;

[0157] In a nitrogen atmosphere, mix the tunnel-type oxide, DBSA, and 300 mL of deionized water obtained in step (1), add An thereto and disperse evenly to obtain an emulsion-like mixture; slowly drop the APS solution into the above mixture, stop stirring after stirring and polymerizing at room temperature for 7 h to obtain a primary product;

[0158] (3) Add 100 mL of chloroform to the primary product (400 mL) obtained in step (2) for demulsification and extraction. After standing and separating into layers, conduct solid-liquid separation. Wash the obtained solid phase (precipitate) and set aside; conduct oil-water separation on the obtained liquid phase, retain the organic phase (polyaniline extraction solution), wash it, and set aside;

[0159] (4) Mix the organic phase and the solid phase obtained in step (3), stir at room temperature for 40 min to mix evenly, and then place it in a vacuum oven and dry at 80 °C under vacuum for 24 h to obtain the tunnel-type oxide composite cathode material.

[0160] Example 9

[0161] A tunnel-type oxide composite cathode material and a preparation method thereof, the preparation method comprising the following steps:

[0162] (1) Take appropriate amounts of Na2CO3 and MnCO3, conduct grinding pretreatment, and set aside. Feed Na2CO3 and MnCO3 in a molar ratio of 0.250:1, conduct simple uniform mixing in a mixer, transfer to a zirconia ball mill jar, add ethanol solvent, and conduct ball milling treatment at 300 rpm for 3 h. After collecting and drying the ball-milled product, transfer it to a muffle furnace and sinter at 850 °C in air atmosphere for 15 h. After the sintering is completed, cool it with the furnace to obtain a tunnel-type oxide with the chemical formula Na 0.44 MnO2;

[0163] (2) Prepare the tunnel-type oxide obtained in step (1) and An in a mass ratio of 1:0.06; prepare materials in a ratio where the molar ratio of p-toluenesulfonic acid (TSA) to An is 0.75:1 and the molar ratio of APS to An is 1:1;

[0164] In a nitrogen atmosphere, mix the tunnel-type oxide, TSA, and 300 mL of deionized water obtained in step (1), then add An thereto and disperse evenly to obtain an emulsion-like mixture; slowly drip the APS solution into the above mixture, stop stirring after stirring the polymerization reaction at room temperature for 7 h to obtain a primary product;

[0165] (3) Add 100 mL of chloroform to the primary product (400 mL) obtained in step (2) for demulsification and extraction. After standing and separating into layers, perform solid-liquid separation. The obtained solid phase (precipitate) is washed and reserved; perform oil-water separation on the obtained liquid phase, retain the organic phase (polyaniline extract), and wash and reserve it;

[0166] (4) Mix the organic phase and the solid phase obtained in step (3), stir at room temperature for 40 min to mix evenly, and then place it in a vacuum oven for vacuum drying at 80 °C for 24 h to obtain the tunnel-type oxide composite cathode material.

[0167] Comparative Example 1

[0168] A tunnel-type oxide cathode material and its preparation method. The preparation method is step (1) in Example 1 to obtain a tunnel-type oxide cathode material with a theoretical chemical formula of Na 0.44 MnO2.

[0169] Comparative Example 2

[0170] A tunnel-type oxide cathode material and its preparation method. The preparation method includes the following steps: Take appropriate amounts of Na2CO3 and MnCO3, perform grinding pretreatment, and then reserve; Feed Na2CO3 and MnCO3 in a molar ratio of 0.280:1, perform simple uniform mixing in a mixer, transfer to a zirconia ball mill tank, and add an ethanol solvent. Perform ball milling at 300 rpm for 3 h. The ball-milled product is collected, dried, transferred to a muffle furnace, and sintered at 850 °C in an air atmosphere for 15 h. After sintering, cool with the furnace to obtain the tunnel-type oxide cathode material.

[0171] Comparative Example 3

[0172] A tunnel-type oxide composite cathode material and its preparation method. The preparation method includes the following steps:

[0173] (1) Obtain a tunnel-type oxide by the method in step (1) of Example 1;

[0174] (2) preparing the tunnel oxide obtained in step (1) and An in a mass ratio of 1:0.06; preparing the molar ratio of DBSA to An in a ratio of 0.75:1 and the molar ratio of APS to An in a ratio of 1:1;

[0175] In a nitrogen atmosphere, the tunnel oxide obtained in step (1), DBSA and 300 mL of deionized water are mixed, and An is added thereto and dispersed evenly to obtain an emulsion-like mixed solution; the APS solution is slowly added dropwise to the mixed solution, and the polymerization reaction is stirred at room temperature for 7 hours, and then the stirring is stopped to obtain a primary product;

[0176] (3) Filtering the initial product obtained in step (2), collecting the solid phase, washing the solid phase, and placing it in a vacuum oven at 80° C. for 24 hours to obtain the tunnel-type oxide composite positive electrode material.

[0177] Comparative Example 4

[0178] A tunnel-type oxide composite positive electrode material and a preparation method thereof, the preparation method comprising the following steps:

[0179] (1) obtaining a tunnel oxide by the method of step (1) in Example 1;

[0180] (2) preparing the tunnel-type oxide obtained in step (1) and polyaniline (98%, Aladdin) at a mass ratio of 1:0.06; mixing polyaniline with chloroform to obtain a solution with a polyaniline concentration of 0.4 mol / L; adding the tunnel-type oxide to the solution, stirring at room temperature for 40 min to fully mix, and then placing the solution in a vacuum oven at 80° C. and vacuum drying for 24 h to obtain the tunnel-type oxide composite positive electrode material.

[0181] The electrochemical performance test of the tunnel-type oxide positive electrode materials provided in Examples 1-9 and Comparative Examples 1-4 was carried out, and the specific method is as follows:

[0182] Assemble a sodium-ion coin cell using the cathode material to be tested: Mix the cathode material, conductive agent (conductive carbon black SP), and binder (polyvinylidene fluoride, PVDF) in a mass ratio of 8:1:1, add the solvent N-methylpyrrolidone (NMP) for homogenization to obtain a slurry with a solid content of 24.2%; then coat the slurry on aluminum foil, roll, punch, and vacuum dry to form a cathode electrode; use the prepared cathode electrode as the working electrode, metallic sodium as the counter electrode, glass fiber cloth as the separator, and use a 1M NaClO4 solution as the electrolyte (the solvent is a mixture of propylene carbonate PC and fluoroethylene carbonate FEC with a mass ratio of 97:3); assemble into a CR2016 coin cell in a glove box filled with an argon atmosphere; after the coin cell is assembled, perform electrochemical performance tests on a BlueTEC battery test system according to the following steps, with the test voltage range of 2.0 - 4.0V and the rates of 0.1C, 0.5C, 1.0C, 2.0C, 5.0C respectively; perform constant current charge and discharge cycling under the condition of 0.5C for 300 cycles to obtain the capacity retention rate.

[0183] Table 1

[0184]

[0185]

[0186] Combined with the performance test data in Table 1, compared with the tunnel-type oxide synthesized by the solid-phase method without coating modification (Comparative Example 1), in the preparation method provided by the present invention, aniline monomer is introduced and a specific two-step coating process is carried out. Through the cooperation and synergistic effect of the raw material design and the specific process method, the obtained tunnel-type oxide composite cathode material has significantly improved conductivity and charge-discharge capacity, good rate performance, and excellent cycling performance. The specific capacities at 0.1C, 0.5C, 1.0C, 2.0C, and 5.0C are 116.34 - 133.01 mAh / g, 110.05 - 128.34 mAh / g, 98.78 - 113.18 mAh / g, 91.03 - 106.23 mAh / g, and 83.93 - 101.26 mAh / g respectively, and the capacity retention rate after 300 cycles at 0.5C is ≥85%, which can reach 85.01 - 92.32%. In addition, in the present invention, through the dosage design of aniline monomer, the screening of organic acid DBSA, and the mutual compounding of process routes, the electrochemical performance of the tunnel-type oxide composite cathode material can be further optimized; if the dosage of aniline monomer is too much (Example 8) or the preferred DBSA is not used (Example 9), the capacity will decrease, especially the rate performance and cycling performance will decline, and the electrochemical performance of the material cannot be effectively improved.

[0187] In the preparation method provided by the present invention, first, tunnel-type oxides are prepared by a solid-phase method, and then aniline monomers are introduced. A process route including two coating processes is designed to form a polyaniline coating layer with uniform properties, uniform thickness, and complete structure on the surface of the tunnel-type oxides, so that the obtained tunnel-type oxide composite cathode material has excellent electrochemical properties, specifically manifested as improvements in conductivity, charge-discharge capacity, rate performance, and cycle stability. Comparative Example 1 is a tunnel-type oxide prepared by a solid-phase method, and its rate performance and cycle performance are significantly poor; in Comparative Example 2, a tunnel-type oxide with increased Na content prepared by a solid-phase method, although the specific capacity at a low rate is improved compared with Comparative Example 1, the charge-discharge capacity and cycle performance are still significantly insufficient. Comparative Examples 3-4 perform coating modification on the tunnel-type oxides, but they do not adopt the preparation method defined in the present invention, and the coating process steps are different, so a polyaniline coating layer with uniform thickness and complete structure cannot be obtained, and the conductivity and charge-discharge specific capacity of the tunnel-type oxide composite cathode material are not effectively improved, manifested as low capacity and poor rate performance. Although the cycle performance is slightly better than that of the untreated material, it still cannot reach the ideal performance level of the cathode material for sodium ion batteries.

[0188] The applicant declares that the present invention uses the above embodiments to illustrate the tunnel-type oxide composite cathode material, its preparation method and application of the present invention, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A preparation method of a tunnel-type oxide composite cathode material, characterized in that, The preparation method comprises the following steps: (1) Mix a sodium source and a manganese source and then perform sintering to obtain a tunnel-type oxide; (2) Mix the tunnel-type oxide obtained in step (1) with an organic acid, aniline, and water to obtain a mixed solution; the mixed solution undergoes a polymerization reaction in the presence of an oxidant to obtain a primary product; (3) Mix the primary product obtained in step (2) with an organic solvent, and then perform solid-liquid separation and oil-water separation to obtain a solid phase and an organic phase; (4) Mix and dry the solid phase and the organic phase obtained in step (3) in sequence to obtain the tunnel-type oxide composite cathode material; In step (1), the molar ratio of sodium in the sodium source to manganese in the manganese source is (0.2 - 0.51):1; The sintering in step (1) is carried out in an aerobic atmosphere; The organic acid in step (2) is dodecylbenzenesulfonic acid; In step (2), the mass ratio of the tunnel-type oxide to aniline is 1:(0.01 - 0.1).

2. The preparation method according to claim 1, wherein The sodium source in step (1) includes sodium hydroxide and / or sodium salt.

3. The preparation method according to claim 1, wherein The sodium source in step (1) includes any one or a combination of at least two of sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium acetate, sodium sulfate, sodium nitrate, and sodium chloride.

4. The preparation method according to claim 1, wherein The manganese source in step (1) includes manganese oxide and / or manganese salt.

5. The preparation method according to claim 4, characterized in that, The manganese oxide includes any one or a combination of at least two of MnO, MnO₂, Mn₂O₃, and Mn₃O₄.

6. The preparation method according to claim 4, characterized in that, The manganese salt includes any one or a combination of at least two of manganese carbonate, manganese sulfate, manganese chloride, manganese nitrate, and manganese acetate.

7. The preparation method according to claim 1, characterized in that, The mixing method in step (1) is ball milling.

8. The preparation method according to claim 7, characterized in that, The mixing method is wet ball milling.

9. The preparation method according to claim 7, characterized in that, The ball milling is carried out in the presence of an organic solvent, and the organic solvent includes an alcohol solvent and / or a ketone solvent.

10. The preparation method according to claim 7, characterized in that, The rotation speed of the ball milling is 200 - 600 rpm.

11. The preparation method according to claim 10, characterized in that, The rotation speed of the ball milling is 300 - 550 rpm.

12. The preparation method according to claim 7, characterized in that, The time of the ball milling is 2 - 5 h.

13. The preparation method according to claim 7, characterized in that, After the ball milling, a drying step is further included.

14. The preparation method according to claim 13, characterized in that, The drying temperature is 60 - 100 °C.

15. The preparation method according to claim 13, wherein The drying time is 0.5 - 6 h.

16. The preparation method according to claim 1, characterized in that, The sintering temperature in step (1) is 700 - 950 °C.

17. The preparation method according to claim 1, characterized in that, The sintering time in step (1) is 3 - 24 h.

18. The preparation method according to claim 1, characterized in that, In step (2), the molar ratio of the organic acid to aniline is (0.5 - 1.0):

1.

19. The preparation method according to claim 1, characterized in that, In step (2), based on 1 g of the mass of the organic acid, the volume of water is 100 - 500 mL.

20. The preparation method according to claim 1, wherein The oxidant in step (2) is persulfate.

21. The preparation method according to claim 20, characterized in that, The oxidant is ammonium persulfate.

22. The preparation method according to claim 1, characterized in that, In step (2), the molar ratio of the oxidant to aniline is (0.5 - 2.0):

1.

23. The preparation method according to claim 1, characterized in that, The polymerization reaction in step (2) is carried out in the presence of a protective atmosphere.

24. The preparation method according to claim 1, wherein The temperature of the polymerization reaction in step (2) is 15 - 40 °C.

25. The preparation method according to claim 1, characterized in that, The time of the polymerization reaction in step (2) is 6 - 8 h.

26. The preparation method according to claim 1, characterized in that, The organic solvent in step (3) includes any one or a combination of at least two of dichloromethane, chloroform, carbon tetrachloride, chlorobenzene, and dichlorobenzene.

27. The preparation method according to claim 26, wherein The organic solvent is chloroform.

28. The preparation method according to claim 1, wherein In step (3), the volume ratio of the primary product to the organic solvent is 1:(0.1 - 2.0).

29. The preparation method according to claim 1, characterized in that, The solid phase and the organic phase obtained by the solid-liquid separation and oil-water separation in step (3) each independently undergo a washing step.

30. The preparation method according to claim 1, characterized in that, The mixing described in step (4) is carried out under stirring conditions.

31. The preparation method according to claim 1, characterized in that, The time for the mixing described in step (4) is 0.1 - 12 h.

32. The preparation method according to claim 31, characterized in that, The time for the mixing is 0.1 - 1 h.

33. The preparation method according to claim 1, characterized in that, The drying method described in step (4) is vacuum drying.

34. The preparation method according to claim 1, characterized in that, The temperature for the drying described in step (4) is 60 - 100 °C.

35. The preparation method according to claim 1, wherein The time for the drying described in step (4) is 12 - 48 h.

36. The preparation method according to claim 1, characterized in that, The preparation method specifically includes the following steps: (1) Mix a sodium source and a manganese source by wet ball milling. The material obtained by mixing is dried and sintered to obtain a tunnel-type oxide. Among them, the rotation speed of the wet ball milling is 200 - 600 rpm, and the time is 2 - 5 h. The sintering is carried out in an aerobic atmosphere, the temperature is 700 - 950 °C, and the time is 3 - 24 h. (2) Mix the tunnel-type oxide obtained in step (1) with dodecylbenzenesulfonic acid, aniline, and water to obtain a mixed solution. The mixed solution undergoes a polymerization reaction in the presence of an oxidant to obtain a primary product. Among them, the mass ratio of the tunnel-type oxide to aniline is 1:(0.01 - 0.1), and the molar ratio of dodecylbenzenesulfonic acid, the oxidant, and aniline is (0.5 - 1.0):(0.5 - 2.0):

1. The polymerization reaction is carried out in a protective atmosphere, the temperature is 15 - 40 °C, and the time is 6 - 8 h. (3) Demulsify the primary product obtained in step (2) with an organic solvent, and carry out solid-liquid separation and oil-water separation on the layered system to obtain a solid phase, an organic phase, and an aqueous phase. The volume ratio of the primary product to the organic solvent is 1:(0.1 - 2.0). (4) Mix the solid phase and the organic phase obtained in step (3) evenly, and dry at 60 - 100 °C for 12 - 48 h to obtain the tunnel-type oxide composite cathode material.

37. A tunnel-type oxide composite cathode material, characterized in that, The tunnel-type oxide composite cathode material is prepared by the preparation method described in any one of claims 1 - 36.

38. The tunnel-type oxide composite cathode material according to claim 37, wherein The tunnel-type oxide composite cathode material is a tunnel-type oxide coated with polyaniline. The chemical formula of the tunnel-type oxide is NaxMnO2, where 0 < x < 0.

5.

39. Use of a tunnel-type oxide composite cathode material as described in claim 37 or 38 in an electrochemical device.

40. The application according to claim 39, characterized in that, The electrochemical device includes a sodium-ion battery or a capacitor.

41. A sodium-ion battery, characterized in that, The sodium-ion battery includes the tunnel-type oxide composite cathode material as described in claim 37 or 38.

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