A carbon-prussian blue-zinc oxide composite material, a preparation method thereof, a positive electrode material and a sodium ion battery

Abstract

The application belongs to the technical field of sodium ion battery cathode material preparation, and discloses a carbon-prussian blue-zinc oxide composite material, a preparation method, a cathode material and a sodium ion battery. The preparation method comprises the following steps: growing prussian blue crystals on the surface of a modified carbon source to obtain a primary growth carbon-prussian blue composite material; growing prussian blue crystals on the surface of the primary growth carbon-prussian blue composite material to obtain a secondary growth carbon-prussian blue composite material; dissolving a soluble zinc salt in a solvent, then adding the secondary growth carbon-prussian blue composite material, removing the solvent, and performing heat treatment. The application uses secondary growth to increase the particle size of prussian blue, facilitates the processing of a subsequent cathode sheet, and improves the battery performance. Through surface coating of zinc oxide, the structure of prussian blue crystals is prevented from collapsing in the charging and discharging process, and when used as an electrode material, the rate performance and cycle stability of the sodium ion battery are greatly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrode material preparation, and particularly relates to a carbon-prussian blue-zinc oxide composite material, a preparation method thereof, a positive electrode material and a sodium ion battery. BACKGROUND

[0002] Lithium ion batteries are greatly hindered in the development of electrochemical energy storage due to the resource shortage of positive electrode materials, the low safety performance and the continuously high price of raw materials. Similar in principle, sodium ion batteries have attracted widespread attention due to the advantages of abundant sodium resources, high energy conversion efficiency, long cycle life and good safety performance, and can be used as an ideal substitute for lithium ion batteries in some application scenarios. Prussian blue material has a unique open framework structure, rich sodium storage sites and large sodium ion migration channels, and can obtain high specific capacity, good cycle performance and rate performance when used as a positive electrode material of a sodium ion battery. Therefore, prussian blue is an important direction for the development of future sodium ion batteries.

[0003] In the existing preparation method, prussian blue is usually prepared by chemical co-precipitation in an aqueous solution. This method inevitably introduces coordination water and vacancies into the prussian blue crystal, thereby occupying the sodium storage sites and the sodium ion deintercalation channel, leading to the decomposition of the structure during the charging and discharging process, and further leading to poor cycle performance and rate performance. In addition, the poor conductivity of prussian blue particles inside and between particles further reduces the electrochemical performance, greatly limiting its wide application. The existing solutions usually start from the preparation process of raw materials and subsequent processing, reduce the water content to reduce vacancies to avoid the problem of structural decomposition of prussian blue during the charging and discharging cycle; and improve the conductivity of prussian blue by doping carbon nanotubes or graphene in the prussian blue positive electrode slurry. However, the material processing technology involved in the above method has relatively high requirements for experimental equipment and operation technology. In addition, the combination of carbon nanotubes and prussian blue is not high, and the conductivity of prussian blue cannot be improved by simple mechanical mixing. Only the conductivity of prussian blue particles in contact with carbon nanotubes can be improved, and the conductivity of prussian blue particles not in contact with carbon nanotubes is still low. In addition, agglomeration easily occurs during the mixing process with carbon nanotubes or graphene, leading to a significant decrease in battery performance. SUMMARY

[0004] To solve the problems of poor structural stability and poor conductivity of prussian blue, the purpose of the present application is to provide a carbon-prussian blue-zinc oxide composite material, a preparation method thereof, a positive electrode material and a sodium ion battery. The method improves the conductivity of prussian blue while overcoming the decomposition of the structure during the charging and discharging cycle, and can be used as a positive electrode material of a sodium ion electrode, which is beneficial to improve the rate performance and cycle stability.

[0005] To achieve the above object, the application adopts the following technical scheme:

[0006] A preparation method of a large-particle-size carbon-prussian blue-zinc oxide composite material, comprising the following steps:

[0007] 1) modifying a carbon source;

[0008] 2) growing prussian blue crystals on the surface of the modified carbon source to obtain a primary growth carbon-prussian blue composite material;

[0009] 3) growing prussian blue crystals on the surface of the primary growth carbon-prussian blue composite material to obtain a secondary growth carbon-prussian blue composite material;

[0010] 4) dissolving a soluble zinc salt in a solvent under stirring, then adding the secondary growth carbon-prussian blue composite material, uniformly dispersing, removing the solvent, and then heating to obtain the carbon-prussian blue-zinc oxide composite material.

[0011] Further, the specific process of modifying the carbon source is: modifying carbon nanotubes, graphene or carbon fibers by using sulfuric acid and hydrogen peroxide to make the carbon source carry a negative group to obtain the modified carbon source.

[0012] Further, the specific process of step 2) is: dissolving sodium ferrocyanide, a soluble sodium salt and a surfactant in deionized water under nitrogen protection, adjusting the pH to 1-3 to form a mixed solution A;

[0013] dissolving one of a soluble divalent manganese salt and a soluble divalent nickel salt, a soluble divalent iron salt, a soluble sodium salt and a surfactant in deionized water under nitrogen protection to obtain a solution, dispersing the modified carbon nanotubes in the solution, adjusting the pH to 1-3 to form a mixed solution B;

[0014] dissolving one of a soluble divalent manganese salt and a soluble divalent nickel salt, a soluble sodium salt and a surfactant in deionized water under nitrogen protection, adjusting the pH to 1-3 to form a mixed solution C;

[0015] mixing the mixed solution A, the mixed solution B and the mixed solution C uniformly, drying to obtain the primary growth carbon-prussian blue composite material.

[0016] Further, the specific process of step 3) is: dissolving sodium ferrocyanide, a soluble sodium salt and a surfactant in deionized water under nitrogen protection to obtain a mixed solution A;

[0017] dissolving one of a soluble divalent manganese salt and a soluble divalent nickel salt, a soluble divalent iron salt, a soluble sodium salt and a surfactant in deionized water under nitrogen protection to obtain a mixed solution B;

[0018] one of soluble divalent manganese salt, soluble divalent nickel salt, soluble sodium salt, primary growth carbon-prussian blue composite material and surfactant are dissolved in deionized water to form a mixed solution C under nitrogen protection;

[0019] The mixed solution A, the mixed solution B and the mixed solution C are mixed, stirred, dried to obtain a secondary growth carbon-prussian blue composite material.

[0020] Further, in step 2), the molar ratio of soluble sodium salt, sodium ferrocyanide and soluble divalent iron salt is (0-25):16:(16-20);

[0021] In step 2) and step 3), the soluble sodium salt is one or more of sodium citrate, sodium chloride, sodium ascorbate and sodium sulfate;

[0022] In step 2) and step 3), the surfactant is one or more of polyvinylpyrrolidone, polyethylene glycol, sodium dodecyl benzene sulfonate, polyethyleneimine and sodium hexadecyl sulfonate; the molecular weight of polyvinylpyrrolidone is 45000-58000;

[0023] In step 2) and step 3), the soluble divalent iron salt is one or more of ferrous chloride, ferrous sulfate, ferrous nitrate and ferrous acetate;

[0024] In step 2) and step 3), the soluble divalent manganese salt is one or more of manganese chloride, manganese sulfate, manganese nitrate and manganese acetate;

[0025] In step 2) and step 3), the soluble divalent nickel salt is one or more of nickel chloride, nickel sulfate, nickel nitrate and nickel acetate.

[0026] Further, in step 3), the soluble sodium salt in the mixed solution A, the mixed solution B and the mixed solution C is in a saturated state; in step 3), the total concentration of one of soluble divalent manganese salt and soluble divalent nickel salt, soluble divalent iron salt and soluble sodium salt in the mixed solution B is 2-4 mol / L; in step 3), the total concentration of one of soluble divalent manganese salt and soluble divalent nickel salt and soluble sodium salt in the mixed solution C is 1.9-3.8 mol / L.

[0027] Further, in step 4), the solvent is a mixture of ethanol and water in a volume ratio of 0.5:1-1:1; the soluble zinc salt is one or more of zinc acetate, zinc oxalate, zinc citrate and zinc gluconate; the heating treatment is carried out under an argon atmosphere, the heating treatment temperature is 100-200℃, and the heating treatment time is 4-8h.

[0028] The carbon-prussian blue-zinc oxide composite material is prepared according to the preparation method, the carbon-prussian blue-zinc oxide composite material is a gradient cubic structure, the size of prussian blue crystal grains of the carbon-prussian blue-zinc oxide composite material is 500 nm-3 mu m, and the prussian blue morphology includes a cubic type and a spherical shape.

[0029] A positive electrode material of a sodium ion battery, the positive electrode material is the carbon-prussian blue-zinc oxide composite material.

[0030] A sodium ion battery, comprising a diaphragm, an electrolyte, a positive electrode and metal sodium as a negative electrode, the material of the positive electrode is the carbon-prussian blue-zinc oxide composite material.

[0031] Compared with the prior art, the present application has the beneficial effects that:

[0032] The carbon-prussian blue-zinc oxide composite material of the present application takes the carbon nanotube with high dispersibility, high conductivity and high reactivity as a carrier, through electrostatic adsorption, the oxygen-containing group with negative electricity on the carbon surface is combined with the divalent iron ion with positive electricity in the solution, and the in-situ growth of prussian blue on the carbon is promoted. Compared with the traditional method of mechanically mixing prussian blue and carbon to improve the conductivity, the present application improves the contact degree of prussian blue and carbon from the atomic level, further improves the conductivity of prussian blue than the traditional method, in addition, through multi-step doping, the material is endowed with higher electrochemical performance. After secondary growth, the particle size of the carbon-prussian blue composite material is further increased, which is beneficial to reduce the difficulty of subsequent electrode processing and the consumption of electrolyte, and at the same time, secondary doping of other elements can be carried out, and the synergistic effect of the two doping further improves the battery performance. In addition, after the secondary growth, a uniform ZnO coating layer is successfully coated on the surface through low-temperature calcination, which improves the Na + The structural stability of the material during intercalation / deintercalation. When used as a positive electrode material of a sodium ion battery, the material is beneficial to realize high rate performance and cycle stability.

[0033] The preparation method of the carbon-prussian blue-zinc oxide composite material of the present application is simple, the raw materials are cheap and easy to obtain, special and expensive equipment and instruments are not needed, and the material can be produced on a large scale, is widely applied to the preparation of prussian blue and prussian blue analogues, and has a wide application prospect in the field of sodium ion batteries. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 A structure schematic view of the carbon nanotube-prussian blue-zinc oxide composite material prepared in Example 1;

[0035] Figure 2 A scanning electron micrograph of the primary growth cubic carbon nanotube-prussian blue composite material prepared in Example 1;

[0036] Figure 3 is a scanning electron micrograph of the secondary growth gradient structure cubic carbon nanotube-prussian blue-zinc oxide composite material prepared in Example 1;

[0037] Figure 4 is a scanning electron micrograph of the secondary growth gradient structure cubic carbon nanotube-prussian blue-zinc oxide composite material prepared in Example 1;

[0038] Figure 5 is a charge-discharge curve of the sodium ion battery assembled from the secondary growth gradient structure cubic carbon nanotube-prussian blue-zinc oxide composite material prepared in Example 1 at 0.1C;

[0039] Figure 6 is the cycle performance of the sodium ion battery assembled from the secondary growth gradient structure cubic carbon nanotube-prussian blue-zinc oxide composite material prepared in Example 1 at 1C;

[0040] Figure 7 is a scanning electron micrograph of the primary growth graphene-cubic prussian blue composite material prepared in Comparative Example 1;

[0041] Figure 8 is a scanning electron micrograph of the primary growth carbon nanotube-spherical prussian blue composite material prepared in Example 2;

[0042] In the figure, 1 is a carbon nanotube, 2 is a prussian blue particle, and 3 is a zinc oxide particle. DETAILED DESCRIPTION

[0043] The specific embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Any form in which the present application can be implemented is within the scope of the present application.

[0044] The test materials and reagents used in the following examples, unless otherwise specified, can be obtained commercially. If the specific technology or conditions are not specified in the examples, the technology or conditions described in the literature in the art or according to the product instructions are used. If the manufacturer of the reagent or instrument is not specified, it is a conventional product that can be obtained commercially.

[0045] The present application provides a preparation method of a carbon-prussian blue-zinc oxide composite material, comprising the following steps:

[0046] Step one, modification of carbon source:

[0047] The carbon source is modified by concentrated sulfuric acid (mass concentration 98%) and hydrogen peroxide to carry negative groups, thereby obtaining a modified carbon source.

[0048] The carbon source is carbon nanotubes, graphene, or carbon fibers, etc.

[0049] The carbon nanotubes include one or both of single-walled carbon nanotubes and multi-walled carbon nanotubes.

[0050] The carbon nanotubes can carry one or more of carboxyl, hydroxyl, sulfonic acid, mercapto, and carbonyl groups.

[0051] Step two, first growing carbon-Prussian blue composite material and doping:

[0052] Mixing solution A preparation process: under nitrogen protection, sodium ferrocyanide, soluble sodium salt, and surfactant are fully dissolved in deionized water, and hydrochloric acid is used to acidify to pH = 1-3 to form a uniform mixing solution A. The molar ratio of sodium ferrocyanide, soluble sodium salt, and surfactant is 4:(0-3):(0-0.0025), preferably 4:3:0.0025;

[0053] Among them, the soluble sodium salt includes one or more of sodium citrate, sodium chloride, sodium ascorbate, and sodium sulfate.

[0054] The surfactant includes one or more of polyvinylpyrrolidone (PVP), polyethylene glycol, sodium dodecylbenzenesulfonate, polyethyleneimine, and sodium hexadecylsulfate. The molecular weight of polyvinylpyrrolidone ranges from 45,000 to 58,000.

[0055] Mixing solution B preparation process: under nitrogen protection, one of soluble divalent manganese salt and soluble divalent nickel salt, soluble divalent iron salt, soluble sodium salt, and surfactant are fully dissolved in deionized water to obtain a solution, the modified carbon source is dispersed in the solution, and hydrochloric acid is used to acidify to pH = 1-3 to form a uniform mixing solution B. Among them, the molar ratio of soluble divalent manganese salt, soluble divalent iron salt, soluble sodium salt, and surfactant is 6:16:(0-6):(0-0.005), preferably 6:16:6:0.005; the molar ratio of soluble divalent nickel salt, soluble divalent iron salt, soluble sodium salt, and surfactant is 1.4:16:(0-6):(0-0.005), preferably 1.4:16:6:0.005;

[0056] Among them, the soluble divalent iron salt includes one or more of ferrous chloride, ferrous sulfate, ferrous nitrate, and ferrous acetate.

[0057] The soluble divalent manganese salt is one or more of manganese chloride, manganese sulfate, manganese nitrate, and manganese acetate.

[0058] The soluble divalent nickel salt is one or more of nickel chloride, nickel sulfate, nickel nitrate, and nickel acetate.

[0059] The mixing liquid C preparation process: under nitrogen protection, one of the soluble divalent manganese salt and the soluble divalent nickel salt, the soluble sodium salt and the surfactant are dissolved in deionized water, and the mixture is acidified to pH = 1-3 with hydrochloric acid to form a uniform mixing liquid C. The molar ratio of the soluble divalent manganese salt, the soluble sodium salt and the surfactant is 3:(0-6):(0-0.005), preferably 3:6:0.005; the molar ratio of the soluble divalent nickel salt, the soluble sodium salt and the surfactant is 0.7:(0-6):(0-0.005), preferably 0.7:6:0.005;

[0060] The soluble sodium salt includes one or more of sodium citrate, sodium chloride, sodium ascorbate and sodium sulfate. The soluble divalent manganese salt is one or more of manganese chloride, manganese sulfate, manganese nitrate and manganese acetate. The soluble divalent nickel salt is one or more of nickel chloride, nickel sulfate, nickel nitrate and nickel acetate. The molar ratio of the soluble sodium salt, sodium ferrocyanide and the soluble divalent iron salt is (0-25):16:(16-20), preferably 25:16:16.

[0061] The soluble divalent nickel salt can be used in both the mixing liquid B and the mixing liquid C, or the soluble divalent manganese salt can be used in both the mixing liquid B and the mixing liquid C, or the soluble divalent nickel salt is used in the mixing liquid B and the soluble divalent manganese salt is used in the mixing liquid C, or the soluble divalent manganese salt is used in the mixing liquid B and the soluble divalent nickel salt is used in the mixing liquid C. In the present application, it is preferred that when the soluble divalent manganese salt is used in the mixing liquid B, the soluble divalent nickel salt is used in the mixing liquid C, or when the soluble divalent nickel salt is used in the mixing liquid B, the soluble divalent manganese salt is used in the mixing liquid C.

[0062] The co-precipitation process: mixing the mixing liquid A, the mixing liquid B and the mixing liquid C at a certain temperature, after mixing, the molar ratio of the soluble sodium salt, sodium ferrocyanide and the soluble divalent manganese salt and the soluble divalent nickel salt in the mixing liquid B, the soluble divalent iron salt and the soluble sodium salt is (0-2.5):1.6:1:(0-1.6):0.6; then stirring for 24h, generating carbon-prussian blue composite material, washing the obtained carbon-prussian blue composite material with deionized water and ethanol, vacuum drying to obtain dried carbon nanotube-prussian blue composite material for standby. The temperature of the vacuum drying oven can be set to 110-260℃, the drying time can be set to 16-48h, and the vacuum degree can be set to <133Pa.

[0063] In the co-precipitation process, the mixing of the mixing liquid A, the mixing liquid B and the mixing liquid C includes dropping the mixing liquid A and the mixing liquid B into the mixing liquid C respectively, dropping the mixing liquid A into the mixture of the mixing liquid B and the mixing liquid C, or dropping the mixing liquid B into the mixture of the mixing liquid A and the mixing liquid C.

[0064] The first growth can be doped with one or more of Cu, Mg, Cr, V, Ti, Mo, Ni, Mn, Co, P, S, Al, Si, Zn and Sn.

[0065] Step three, second growth of carbon-Prussian blue composite material:

[0066] The dried carbon nanotube-Prussian blue composite material obtained in step two is dispersed in mixed solution C, and the second growth is carried out according to the experimental process of step two, except that the system does not need to be acidified with hydrochloric acid, and soluble sodium salt needs to be added and saturated in mixed solution A, mixed solution B and mixed solution C, and no carbon nanotubes need to be added again in mixed solution B, and different elements are doped in mixed solution B and mixed solution C. The specific process is as follows:

[0067] Mixed solution A preparation process: under nitrogen protection, sodium ferrocyanide, soluble sodium salt and surfactant are fully dissolved in deionized water to obtain mixed solution A, wherein the soluble sodium salt in mixed solution A is in a saturated state. The molar ratio of sodium ferrocyanide, soluble sodium salt and surfactant is 26:75:(0-0.01), and the preferred ratio is 26:75:0.01.

[0068] Among them, the soluble sodium salt includes one or more of sodium citrate, sodium chloride, sodium ascorbate and sodium sulfate.

[0069] The surfactant includes one or more of polyvinylpyrrolidone (PVP), polyethylene glycol, sodium dodecylbenzenesulfonate, polyethyleneimine and sodium hexadecylsulfate. The molecular weight of polyvinylpyrrolidone ranges from 45,000 to 58,000.

[0070] Mixed solution B preparation process: under nitrogen protection, one of soluble divalent manganese salt and soluble divalent nickel salt, soluble divalent iron salt, soluble sodium salt and surfactant are fully dissolved in deionized water to obtain a solution, which is acidified with hydrochloric acid to form a uniform mixed solution B, wherein the soluble sodium salt in mixed solution B is in a saturated state. The molar ratio of soluble divalent nickel salt, soluble divalent iron salt, soluble sodium salt and surfactant is 0.14:1.6:10:(0-0.0005), and the preferred ratio is 0.14:1.6:10:0.0005; the molar ratio of soluble divalent manganese salt, soluble divalent iron salt, soluble sodium salt and surfactant is 6:1.6:10:(0-0.0005), and the preferred ratio is 6:1.6:10:0.0005.

[0071] Among them, the soluble divalent iron salt includes one or more of ferrous chloride, ferrous sulfate, ferrous nitrate and ferrous acetate.

[0072] The soluble divalent manganese salt is one or more of manganese chloride, manganese sulfate, manganese nitrate and manganese acetate.

[0073] The soluble divalent nickel salt is one or more of nickel chloride, nickel sulfate, nickel nitrate, and nickel acetate.

[0074] The mixed solution C preparation process: under nitrogen protection, one of the soluble divalent manganese salt and the soluble divalent nickel salt, the carbon-prussian blue composite material prepared in step 2), the soluble sodium salt, and the surfactant are fully dissolved in deionized water, and hydrochloric acid is used for acidification to form a uniform mixed solution C, wherein the soluble sodium salt in the mixed solution C is in a saturated state. When the carbon-prussian blue composite material is 1 g, the amount of the soluble divalent nickel salt is 0.72 mmol, the amount of the soluble sodium salt is 0.1 mol, and the amount of the surfactant is 0.005 mmol when the nickel salt is used; the amount of the soluble divalent manganese salt is 0.03 mol, the amount of the soluble sodium salt is 0.1 mol, and the amount of the surfactant is 0.005 mmol when the manganese salt is used.

[0075] The co-precipitation process: mixing the mixed solution A, the mixed solution B, and the mixed solution C at a certain temperature, then stirring for 24 h to generate the carbon nanotube-prussian blue composite material, washing the obtained carbon nanotube-prussian blue composite material with deionized water and ethanol, and vacuum drying to obtain the dried carbon-prussian blue composite material for standby. The temperature of the vacuum drying box can be set to 110°C-260°C, the drying time can be set to 16-48 h, and the vacuum degree can be set to <133 Pa.

[0076] In the co-precipitation process, the mixed solution A, the mixed solution B, and the mixed solution C are mixed by dropping the mixed solution A and the mixed solution B into the mixed solution C, dropping the mixed solution A into the mixed solution of the mixed solution B and the mixed solution C, or dropping the mixed solution B into the mixed solution of the mixed solution A and the mixed solution C.

[0077] The first growth can be doped with one or more elements such as Cu, Mg, Cr, V, Ti, Mo, Ni, Mn, Co, P, S, Al, Si, Zn, and Sn.

[0078] The obtained second growth carbon nanotube-prussian blue composite material is washed with deionized water and ethanol, and dried for standby.

[0079] The second growth can be doped with one or more elements such as Cu, Mg, Cr, V, Ti, Mo, Ni, Mn, Co, P, S, Al, Si, Zn, and Sn.

[0080] In the second growth, the soluble sodium salt in the mixed solution A, the mixed solution B, and the mixed solution C is in a saturated state.

[0081] The concentration of the soluble sodium salt in the mixed solution C is 1.9 mol / L, wherein the molar ratio of the soluble divalent nickel salt, the soluble sodium salt and the surfactant is 0.72:100:(0-0.005), preferably 0.72:100:0.005. The molar ratio of the soluble divalent manganese salt, the soluble sodium salt and the surfactant is 3:10:(0-0.0005), preferably 3:10:0.0005.

[0082] The concentration of the soluble sodium salt in the mixed solution B is 1.9 mol / L, wherein the molar ratio of the soluble divalent nickel salt, the soluble divalent iron salt, the soluble sodium salt and the surfactant is 0.14:1.6:10:(0-0.0005), preferably 0.14:1.6:10:0.0005; the molar ratio of the soluble divalent manganese salt, the soluble divalent iron salt, the soluble sodium salt and the surfactant is 6:1.6:10:(0-0.0005), preferably 6:1.6:10:0.0005.

[0083] In the mixed solution A, the concentration of the soluble sodium salt is 0.75 mol / L, wherein the molar ratio of the sodium ferrocyanide, the soluble sodium salt and the surfactant is 26:75:(0-0.01), preferably 26:75:0.01.

[0084] Step four, the carbon-Prussian blue composite material is coated with zinc oxide.

[0085] The soluble zinc salt is fully dissolved in the mixed solution of ethanol and water under magnetic stirring, the volume ratio of ethanol and water is 0.5:1-1:1, then the dried carbon-Prussian blue composite material in step three is added, and ultrasonic and stirring are performed to make it uniformly dispersed. The uniformly dispersed mixed solution is placed in a rotary evaporator until all the solvents are evaporated. The evaporated powder is heated and treated in a tube furnace under argon atmosphere, the temperature of the tube furnace ranges from 100℃ to 200℃, and the heating and treatment time ranges from 4 to 8 hours, to obtain a gradient cubic carbon-Prussian blue-zinc oxide composite material.

[0086] The size of the Prussian blue crystal grains in the carbon-Prussian blue-zinc oxide composite material prepared by the present application can be changed in the range of 500 nm-3 μm.

[0087] The Prussian blue includes cubic and spherical morphologies.

[0088] The outermost layer coating material of the carbon nanotube-Prussian blue includes one or more of ZnO, TiO2, SiO2, Al2O3, CuO, polystyrene, polyaniline and polydopamine.

[0089] The soluble zinc salt includes one or more of zinc acetate, zinc oxalate, zinc citrate and zinc gluconate.

[0090] The first growth and the second growth after the Prussian blue show different morphologies, the first growth is a cubic shape, and the second growth is a gradient cubic structure.

[0091] The first growth and the second growth after the Prussian blue show different particle sizes, the first growth particle size is 100nm-500nm, and the second growth particle size is 500nm-3um.

[0092] The first growth and the second growth are doped with different elements to improve the battery performance.

[0093] The present application is not limited to secondary growth, but also can be three, four and more growth.

[0094] The same or different elements or chemical substances can be doped in the multiple growth process.

[0095] The carbon-Prussian blue-zinc oxide composite material of the present application comprises carbon, a first growth of carbon-Prussian blue composite material and doping, a second growth of carbon-Prussian blue composite material and doping, and a zinc oxide coated on the surface of the material.

[0096] The present application also provides a positive electrode material of a sodium ion battery, which is the carbon-Prussian blue-zinc oxide composite material.

[0097] The present application also provides a sodium ion battery, which comprises a separator, an electrolyte, a positive electrode and a metal sodium as a negative electrode, characterized in that the material of the positive electrode is the carbon-Prussian blue-zinc oxide composite material.

[0098] The present application modifies the carbon source to carry a negative group, provides a nucleation site for the growth of Prussian blue, is conducive to the growth of Prussian blue crystals on the surface of carbon nanotubes, greatly improves the contact degree of Prussian blue and carbon nanotubes, and provides a convenient channel for electron transmission. On this basis, by secondary growth, Prussian blue is continuously grown on the surface of the carbon nanotube-Prussian blue composite material to form larger particles, further increase the contact area of carbon nanotubes and Prussian blue, and improve the conductivity. At the same time, other elements can be doped in this process to improve the battery performance. In addition, a uniform zinc oxide coating layer is coated on the surface of the material by low-temperature calcination method to prevent the structure of Prussian blue crystals from being decomposed in the charging and discharging process.

[0099] Example 1 (preparation of carbon nanotube-gradient cubic Prussian blue-zinc oxide composite material)

[0100] Step one, carboxylation of carbon nanotubes includes the following steps:

[0101] The concentrated H2SO4 and H2O2 were mixed in a volume ratio of 3:1 (300 mL and 100 mL) and then poured into a 1000 mL flask containing 1 g of multi-walled carbon nanotubes. The flask was placed in an oil bath and heated to 100°C, and the constant temperature reflux reaction was stirred magnetically for 16 h. After the reaction was completed, it was cooled to room temperature, centrifuged at 18000 r / min for 30 min, the supernatant was removed, and the carbon nanotubes were dispersed in deionized water again, and the process was repeated several times until the supernatant was neutral. The carboxylated carbon nanotubes were obtained.

[0102] Step two, the first growth of carbon nanotube-prussian blue composite material includes the following steps:

[0103] Under nitrogen protection, 0.5 g of carboxylated carbon nanotubes in step one were dispersed in 50 mL of deionized water and acidified with hydrochloric acid to pH = 1. Then 4.448 g of ferrous sulfate, 1.088 g of manganese sulfate, 0.362 g of sodium chloride and 0.25 g of PVP were added in sequence under stirring to make them fully dissolved, and a mixed solution B was obtained.

[0104] Under nitrogen protection, 7.744 g of sodium ferrocyanide, 0.724 g of sodium chloride and 0.5 g of PVP were fully dissolved in 100 mL of deionized water under magnetic stirring and acidified with hydrochloric acid to pH = 1 to obtain a mixed solution A.

[0105] Under nitrogen protection, 0.362 g of sodium chloride, 0.544 g of manganese sulfate and 0.25 g of PVP were fully dissolved in 50 mL of deionized water under magnetic stirring and acidified with hydrochloric acid to pH = 1 to obtain a mixed solution C.

[0106] The A solution, B solution were added dropwise into the C solution through a peristaltic pump at a speed of 13.4 rpm and 8.1 rpm respectively, and stirred for 24 h to obtain a carbon nanotube-prussian blue composite material. The obtained carbon nanotube-prussian blue composite material was washed with deionized water and ethanol, and vacuum dried to obtain a dried cubic carbon nanotube-prussian blue composite material, which was ready for use. The temperature of the vacuum drying oven can be set to 110°C-260°C, the drying time can be set to 16-48 hours, and the vacuum degree can be set to <133 Pa.

[0107] Step three, the second growth of carbon nanotube-prussian blue composite material includes the following steps:

[0108] Under nitrogen protection, 1 g of carbon nanotube-prussian blue composite material in step two was dispersed in 50 mL of deionized water. 30 g of sodium citrate, 0.19 g of nickel sulfate and 0.25 g of PVP were added in sequence under magnetic stirring to make them fully dissolved and nitrogen was introduced to obtain a mixed solution C.

[0109] Under nitrogen protection, 4.448 g ferrous sulfate, 30 g sodium citrate, 0.25 g PVP, 0.38 g nickel sulfate were dissolved in 50 mL deionized water under magnetic stirring and nitrogen was bubbled into the solution to obtain a mixed solution B.

[0110] Under nitrogen protection, 7.744 g sodium ferrocyanide, 23 g sodium citrate, 0.5 g PVP were dissolved in 100 mL deionized water under magnetic stirring to obtain a mixed solution A.

[0111] The mixed solution A and the mixed solution B were dropped into the mixed solution C through a peristaltic pump at a speed of 13.4 rpm and 8.1 rpm respectively, and stirred for 24 h to obtain the secondary growth gradient structure carbon nanotube-Prussian blue composite material.

[0112] Step four, the preparation of the gradient cubic carbon nanotube-Prussian blue-zinc oxide composite material includes the following steps:

[0113] 0.6 g zinc gluconate was dissolved in 100 mL deionized water and 50 mL ethanol under magnetic stirring, and 1 g of dried gradient structure carbon nanotube-Prussian blue composite material was added, ultrasonic treatment for 30 min and stirring for 12 h to obtain a mixed solution.

[0114] The above mixed solution was placed in a rotary evaporator until all the solvent was evaporated.

[0115] The evaporated solid powder was heat treated in an argon atmosphere at 150°C for 8 hours in a tube furnace to obtain the secondary growth gradient structure carbon nanotube-Prussian blue-zinc oxide composite material.

[0116] The obtained composite material was washed with deionized water and ethanol for 3 times, dried in a vacuum drying oven at 60°C for 6 hours, and then placed in a vacuum drying oven at 110°C for 16 hours to obtain the large-particle-size carbon nanotube-Prussian blue-zinc oxide composite material.

[0117] Referring to Figure 1 The structure diagram of the carbon nanotube-Prussian blue-zinc oxide composite material prepared in Example 1 can be seen that the carbon nanotube 1 is connected with many cubic Prussian blue particles 2, and the black dots uniformly distributed around are zinc oxide particles 3.

[0118] Referring to Figure 2 The scanning electron microscope photo of the primary growth cubic carbon nanotube-Prussian blue composite material prepared in Example 1 can be seen that the carbon nanotube tightly connects many cubic Prussian blue together.

[0119] Referring to Figure 3The scanning electron microscope photo of the secondary growth gradient structure cubic carbon nanotube-prussian blue-zinc oxide composite material prepared in Example 1 can be seen that the prussian blue particles are in a gradient structure, and are closely combined with the carbon nanotubes, and the small particles on the surface of the prussian blue particles are zinc oxide particles, indicating that the zinc oxide is uniformly coated on the surface of the prussian blue-zinc oxide composite material.

[0120] Referring to Figure 4 The scanning electron microscope photo of the secondary growth gradient structure cubic carbon nanotube-prussian blue-zinc oxide composite material prepared in Example 1 can be seen that the prussian blue particles are in a gradient structure, and are closely combined with the carbon nanotubes, and the small particles on the surface of the prussian blue particles are zinc oxide particles, indicating that the zinc oxide is uniformly coated on the surface of the prussian blue-zinc oxide composite material.

[0121] Referring to Figure 5 The charge-discharge curve of the sodium ion battery assembled by the secondary growth gradient structure cubic carbon nanotube-prussian blue-zinc oxide composite material prepared in Example 1 at 0.1C can be seen that the initial charge-discharge capacity can reach 139.7 mAh / g and 135.4 mAh / g respectively, and the average voltage is 3.35 V.

[0122] Referring to Figure 6 The cycle performance of the sodium ion battery assembled by the secondary growth gradient structure cubic carbon nanotube-prussian blue-zinc oxide composite material prepared in Example 1 at 1C can be seen that the capacity retention rate reaches 95.7% after 100 cycles at 1C current.

[0123] Comparative Example 1 (Preparation of graphene-cubic prussian blue-zinc oxide composite material)

[0124] The same as steps two, three and four in Example 1, and different from step one is that the carbon nanotubes are replaced by graphene.

[0125] Referring to Figure 7 The scanning electron microscope photo of the primary growth graphene-cubic prussian blue composite material prepared in Comparative Example 1 can be seen that the sheet-shaped graphene is closely combined with the prussian blue particles.

[0126] Example 2 (Preparation of carbon nanotube-spherical prussian blue-zinc oxide composite material)

[0127] The same as steps one, three and four in Example 1, and different from step two is that:

[0128] Under nitrogen protection, 0.5 g of carboxylated carbon nanotubes in step one were dispersed in 50 mL of deionized water. Under stirring, 4.448 g of ferrous sulfate, 1.088 g of manganese sulfate and 30 g of sodium citrate were sequentially added, so that they were fully dissolved and nitrogen was introduced to obtain a mixed solution B.

[0129] Under nitrogen protection, 7.744 g of sodium ferrocyanide and 30 g of sodium citrate were dissolved in 100 mL of deionized water with magnetic stirring. Nitrogen gas was then introduced to obtain solution A.

[0130] Under nitrogen protection, 22.1 g of sodium citrate and 0.544 g of manganese sulfate were dissolved in 50 mL of deionized water with magnetic stirring, and 0.1 g of polyethyleneimine (PEI) was added. Nitrogen gas was then introduced to obtain solution C.

[0131] Liquids A and B were added dropwise to liquid C using a peristaltic pump at speeds of 13.4 rpm and 8.1 rpm, respectively, while stirring for 24 hours to obtain a carbon nanotube-spherical Prussian blue composite material.

[0132] See Figure 8 The image shown is a scanning electron microscope (SEM) image of the one-time grown carbon nanotube-spherical Prussian blue composite material prepared in Example 2. It can be seen that the carbon nanotubes are tightly bonded to the spherical Prussian blue particles.

[0133] Example 3

[0134] Step 1, Graphene carboxylation, includes the following steps:

[0135] Concentrated H₂SO₄ and H₂O₂ were mixed uniformly at a volume ratio of 3:1 (300 mL and 100 mL) and poured into a 1000 mL flask containing 1 g of graphene. The flask was placed in an oil bath and heated to 100 °C, then magnetically stirred and refluxed for 16 h. After the reaction was complete, the mixture was cooled to room temperature and centrifuged at 18000 r / min for 30 minutes. The supernatant was removed, and the mixture was redispersed in deionized water. This process was repeated several times until the supernatant was neutral, yielding carboxylated graphene.

[0136] Step 2, the first growth of graphene-Prussian blue composite material includes the following steps:

[0137] Under nitrogen protection, 0.5 g of carboxylated graphene from step one was dispersed in 50 mL of deionized water and acidified with hydrochloric acid to a pH of 2. Then, soluble divalent manganese salt, soluble divalent ferrous salt, soluble sodium salt, and surfactant were added and dissolved completely to obtain mixture B. The molar ratio of the soluble divalent manganese salt, soluble divalent ferrous salt, soluble sodium salt, and surfactant was 6:16:0:0.005; the soluble divalent manganese salt was manganese chloride, the soluble divalent ferrous salt was ferrous sulfate, the soluble sodium salt was sodium chloride, the surfactant was polyethylene glycol, and the amount of ferrous sulfate was 4.448 g.

[0138] Under the protection of nitrogen, 7.744 g of sodium ferrocyanide, soluble sodium salt and surfactant were fully dissolved in 100 mL of deionized water under magnetic stirring and acidified with hydrochloric acid to make the pH = 1, to obtain mixed solution A. The molar ratio of sodium ferrocyanide, soluble sodium salt and surfactant is 4:0:0.0025, and the surfactant is sodium dodecyl benzene sulfonate, and the soluble sodium salt is sodium chloride.

[0139] Under the protection of nitrogen, the soluble divalent manganese salt, the soluble sodium salt and the surfactant were fully dissolved in 50 mL of deionized water under magnetic stirring and acidified with hydrochloric acid to make the pH = 1, to obtain mixed solution C. Among them, the molar ratio of the soluble divalent manganese salt, the soluble sodium salt and the surfactant is 3:6:0.005, the soluble divalent manganese salt is manganese nitrate, the soluble sodium salt is sodium chloride, the amount of sodium chloride is 0.362 g, and the surfactant is sodium hexadecyl sulfonate.

[0140] The A solution and the B solution were added dropwise into the C solution at a speed of 13.4 rpm and 8.1 rpm respectively through a peristaltic pump, and stirred for 24 hours. A carbon-prussian blue composite material was obtained. The carbon-prussian blue composite material was washed with deionized water and ethanol, and vacuum dried to obtain a dried carbon nanotube-prussian blue composite material, which was ready for use. The temperature of the vacuum drying box can be set to 110°C, the drying time can be set to 48 hours, and the vacuum degree can be set to <133 Pa.

[0141] Step three, the second growth of the graphene-prussian blue composite material includes the following steps:

[0142] Under the protection of nitrogen, 7.744 g of sodium ferrocyanide, soluble sodium salt and surfactant were fully dissolved in 100 mL of deionized water under magnetic stirring and acidified with hydrochloric acid to make the pH = 1, to obtain mixed solution A. The molar ratio of sodium ferrocyanide, soluble sodium salt and surfactant is 4:0:0.0025, and the surfactant is sodium dodecyl benzene sulfonate, and the soluble sodium salt is sodium chloride.

[0143] Under the protection of nitrogen, the soluble divalent manganese salt, the soluble divalent iron salt, the soluble sodium salt and the surfactant were fully dissolved in 50 mL of deionized water under magnetic stirring to obtain mixed solution B. Among them, the soluble sodium salt is sodium citrate, and the amount is 30 g, and the sodium citrate is in a saturated state. The molar ratio of the soluble divalent manganese salt, the soluble divalent iron salt, the soluble sodium salt and the surfactant is 6:1.6:10:0.0005. The soluble divalent manganese salt is manganese nitrate, the soluble divalent iron salt is ferrous nitrate, and the surfactant is polyethyleneimine.

[0144] Under nitrogen protection, 7.744 g of sodium ferrocyanide, soluble sodium salt and surfactant were dissolved in 100 mL of deionized water under magnetic stirring to obtain mixed solution A. The soluble sodium salt was in a saturated state. The molar ratio of sodium ferrocyanide, soluble sodium salt and surfactant was 26:75:0.01. The soluble sodium salt was sodium citrate, and the surfactant was sodium dodecyl benzene sulfonate.

[0145] Mixed solution A and mixed solution B were added dropwise into mixed solution C at a speed of 13.4 rpm and 8.1 rpm respectively by using a peristaltic pump, and stirred for 24 h to obtain the secondary growth gradient structure graphene-prussian blue composite material.

[0146] Step four, the preparation of the gradient cubic graphene-prussian blue-zinc oxide composite material includes the following steps:

[0147] Under magnetic stirring, 0.6 g of zinc gluconate was dissolved in a mixture of 100 mL of deionized water and 50 mL of ethanol, and 1 g of dried gradient structure graphene-prussian blue composite material was added. Ultrasonic treatment was performed for 30 min and stirring was performed for 12 h to obtain a mixed solution.

[0148] The above mixed solution was placed in a rotary evaporator until all the solvent was evaporated.

[0149] The evaporated solid powder was heat treated in an argon atmosphere at 200°C for 5 hours in a tube furnace to obtain the secondary growth gradient structure graphene-prussian blue-zinc oxide composite material.

[0150] The obtained composite material was washed with deionized water and ethanol for 3 times, dried in a vacuum drying oven at 60°C for 6 hours, and then placed in a drying oven at 110°C for vacuum drying for 16 hours to obtain the large particle size graphene-prussian blue-zinc oxide composite material.

[0151] Example 4

[0152] Step one, carboxylation of carbon fibers includes the following steps:

[0153] After mixing concentrated H2SO4 and H2O2 in a volume ratio of 3:1 (300 mL and 100 mL), pour them into a 1000 mL flask containing 1 g of carbon fiber. Place the flask in an oil bath and heat to 100°C. Stir at constant temperature under reflux for 16 h. After the reaction is completed, cool to room temperature, centrifuge at 18000 r / min for 30 min, remove the supernatant, and disperse in deionized water repeatedly until the supernatant is neutral. Carboxylated carbon fibers are obtained.

[0154] Step two, the first growth of carbon fiber-prussian blue composite material includes the following steps:

[0155] Under nitrogen protection, 0.5 g of the carboxylated carbon fiber in step one was dispersed in 50 mL of deionized water and acidified with hydrochloric acid to have a pH of 3. Then, a soluble divalent manganese salt, a soluble divalent iron salt, a soluble sodium salt and a surfactant were dissolved under stirring to obtain a mixed solution B. The molar ratio of the soluble divalent manganese salt, the soluble divalent iron salt, the soluble sodium salt and the surfactant was 6:16:0:0; the soluble divalent manganese salt was manganese chloride, and the mass of the manganese chloride was 0.38 g; the soluble divalent iron salt was ferrous sulfate, and the soluble sodium salt was sodium chloride.

[0156] Under nitrogen protection, 7.744 g of sodium ferrocyanide, a soluble sodium salt and a surfactant were dissolved under magnetic stirring in 100 mL of deionized water and acidified with hydrochloric acid to have a pH of 1 to obtain a mixed solution A. The molar ratio of the sodium ferrocyanide, the soluble sodium salt and the surfactant was 4:2:0.001, the soluble sodium salt was sodium chloride, and the surfactant was sodium hexadecyl benzene sulfonate.

[0157] Under nitrogen protection, a soluble divalent manganese salt, a soluble sodium salt and a surfactant were dissolved under magnetic stirring in 50 mL of deionized water and acidified with hydrochloric acid to have a pH of 1 to obtain a mixed solution C. The molar ratio of the soluble divalent manganese salt, the soluble sodium salt and the surfactant was 3:0:0.005, the soluble divalent manganese salt was manganese nitrate, the mass of the manganese nitrate was 0.54 g, and the surfactant was sodium hexadecyl sulfonate.

[0158] The A solution and the B solution were added dropwise into the C solution through a peristaltic pump at a speed of 13.4 rpm and 8.1 rpm respectively, and stirred for 24 h to obtain a carbon-Prussian blue composite material. The obtained carbon-Prussian blue composite material was washed with deionized water and ethanol, and vacuum dried to obtain a dried carbon nanotube-Prussian blue composite material, which was ready for use. The temperature of the vacuum drying box can be set to 110-260°C, the drying time can be set to 16-48 hours, and the vacuum degree can be set to <133 Pa.

[0159] Step three, the second growth of the carbon fiber-Prussian blue composite material includes the following steps:

[0160] Under nitrogen protection, 1 g of the carbon fiber-Prussian blue composite material in step two was dispersed in 50 mL of deionized water. A soluble divalent manganese salt, a soluble sodium salt and a surfactant were added under magnetic stirring to be fully dissolved to obtain a mixed solution C. The soluble sodium salt was sodium citrate, and the sodium citrate was in a saturated state. The molar ratio of the soluble divalent manganese salt, the soluble sodium salt and the surfactant was 3:10:0.0005, the soluble divalent manganese salt was manganese chloride, and the mass of the soluble divalent manganese salt was 0.38 g.

[0161] A mixture liquid B was prepared by dissolving soluble divalent manganese salt, soluble divalent iron salt, soluble sodium salt and surfactant in 50 mL deionized water under nitrogen protection with magnetic stirring. The soluble sodium salt was sodium citrate, and the amount was 30 g. The soluble divalent manganese salt, the soluble divalent iron salt, the soluble sodium salt and the surfactant had a molar ratio of 6:1.6:10:0.0005. The soluble divalent manganese salt was manganese nitrate, the soluble divalent iron salt was ferrous nitrate, and the surfactant was polyethyleneimine.

[0162] A mixture liquid A was prepared by dissolving 7.744 g of sodium ferrocyanide, soluble sodium salt and surfactant in 100 mL deionized water under nitrogen protection with magnetic stirring. The sodium citrate was in a saturated state. The sodium ferrocyanide, the soluble sodium salt and the surfactant had a molar ratio of 16:78:0.05. The soluble sodium salt was sodium citrate, and the surfactant was sodium dodecyl benzene sulfonate.

[0163] The mixture liquid A and the mixture liquid B were added dropwise into the mixture liquid C at a speed of 13.4 rpm and 8.1 rpm respectively through a peristaltic pump with stirring for 24 h to obtain a secondary growth gradient structure carbon fiber-Prussian blue composite material.

[0164] Step four, the preparation of the gradient cubic carbon fiber-Prussian blue-zinc oxide composite material includes the following steps:

[0165] A mixture liquid was prepared by dissolving 0.6 g of zinc gluconate in 100 mL deionized water and 100 mL ethanol under magnetic stirring, and adding 1 g of dried gradient structure carbon fiber-Prussian blue composite material. The mixture was ultrasonically treated for 30 min and stirred for 12 h to obtain a mixture liquid.

[0166] The above mixture liquid was placed in a rotary evaporator until all the solvent was evaporated.

[0167] The evaporated solid powder was heat treated in an argon atmosphere at 140°C in a tube furnace for 6 hours to obtain a secondary growth gradient structure carbon fiber-Prussian blue-zinc oxide composite material.

[0168] The obtained composite material was washed with deionized water and ethanol for 3 times, dried in a vacuum drying oven at 60°C for 6 hours, and then placed in a vacuum drying oven at 110°C for 16 hours to obtain a large-particle-size carbon fiber-Prussian blue-zinc oxide composite material.

[0169] Example 5

[0170] Step one, carboxylation of carbon nanotubes includes the following steps:

[0171] After mixing concentrated H2SO4 and H2O2 in a volume ratio of 3:1 (300 mL and 100 mL) uniformly, pour them into a 1000 mL flask containing 1 g of multi-walled carbon nanotubes, place the flask in an oil bath to heat to 100°C, and magnetically stir at constant temperature for 16 h. After the reaction is completed, cool to room temperature, centrifuge at 18000 r / min for 30 min, remove the supernatant, and disperse in deionized water again, repeat several times until the supernatant is neutral, and obtain carboxylated carbon nanotubes.

[0172] Step two, first growth of carbon nanotube-prussian blue composite material includes the following steps:

[0173] Under nitrogen protection, 0.5 g of carboxylated graphene in step one is dispersed in 50 mL of deionized water and acidified with hydrochloric acid to make its pH = 2. Then, a soluble divalent manganese salt, a soluble divalent iron salt, a soluble sodium salt, and a surfactant are added, and after being fully dissolved, a mixed solution B is obtained. The molar ratio of the soluble divalent manganese salt, the soluble divalent iron salt, the soluble sodium salt, and the surfactant is 6:16:1:0.002; the soluble divalent manganese salt is manganese chloride, the soluble divalent iron salt is ferrous sulfate, the soluble sodium salt is sodium chloride, and the surfactant is polyethylene glycol. The amount of ferrous sulfate is 4.448 g.

[0174] Under nitrogen protection, 7.744 g of sodium ferrocyanide, a soluble sodium salt, and a surfactant are fully dissolved in 100 mL of deionized water under magnetic stirring and acidified with hydrochloric acid to make its pH = 1, and a mixed solution A is obtained. The molar ratio of sodium ferrocyanide, the soluble sodium salt, and the surfactant is 4:0:0.002, the soluble sodium salt is sodium chloride, and the surfactant is sodium dodecyl benzene sulfonate.

[0175] Under nitrogen protection, a soluble divalent manganese salt, a soluble sodium salt, and a surfactant are fully dissolved in 50 mL of deionized water under magnetic stirring and acidified with hydrochloric acid to make its pH = 1, and a mixed solution C is obtained. The molar ratio of the soluble divalent manganese salt, the soluble sodium salt, and the surfactant is 16:1:0.02, the soluble divalent manganese salt is manganese nitrate, the soluble sodium salt is sodium chloride, the amount of sodium chloride is 0.362 g, and the surfactant is sodium hexadecyl sulfonate.

[0176] A solution, B solution, and C solution are added dropwise into C solution through a peristaltic pump at a speed of 13.4 rpm and 8.1 rpm, respectively, and stirred for 24 h to obtain a carbon-prussian blue composite material. The obtained carbon-prussian blue composite material is washed with deionized water and ethanol, and vacuum dried to obtain a dried carbon nanotube-prussian blue composite material, which is ready for use. The temperature of the vacuum drying box can be set to 150°C, the drying time can be set to 40 hours, and the vacuum degree can be set to <133 Pa.

[0177] Step three, the second growth of carbon nanotube-prussian blue composite material includes the following steps:

[0178] The graphene-prussian blue composite material 1 g in step two was dispersed in 50 mL deionized water under nitrogen protection. A soluble divalent manganese salt, a soluble sodium salt and a surfactant were added in sequence under magnetic stirring to make them fully dissolved to obtain a mixed solution C. The soluble sodium salt was sodium citrate, and the sodium citrate was in a saturated state. The molar ratio of the soluble divalent manganese salt, the soluble sodium salt and the surfactant was 10:0.07:0.0001, the surfactant was PVP, the amount of PVP was 0.25 g, and the soluble divalent manganese salt was manganese acetate.

[0179] A soluble divalent manganese salt, a soluble divalent iron salt, a soluble sodium salt and a surfactant were fully dissolved in 50 mL deionized water under magnetic stirring to obtain a mixed solution B under nitrogen protection. The soluble sodium salt was sodium citrate, and the amount of sodium citrate was 30 g, and the sodium citrate was in a saturated state. The molar ratio of the soluble divalent manganese salt, the soluble divalent iron salt, the soluble sodium salt and the surfactant was 6:1.6:10:0. The soluble divalent manganese salt was manganese nitrate, and the soluble divalent iron salt was ferrous nitrate.

[0180] 7.744 g of sodium ferrocyanide, a soluble sodium salt and a surfactant were fully dissolved in 100 mL deionized water under magnetic stirring to obtain a mixed solution A under nitrogen protection. The sodium chloride was in a saturated state. The molar ratio of the sodium ferrocyanide, the soluble sodium salt and the surfactant was 16:78:0.01. The soluble sodium salt was sodium citrate, and the surfactant was sodium dodecyl benzene sulfonate.

[0181] The mixed solution A and the mixed solution B were respectively added dropwise into the mixed solution C at a speed of 13.4 rpm and 8.1 rpm through a peristaltic pump, and stirred for 24 h to obtain a second growth of gradient structure carbon nanotube-prussian blue composite material.

[0182] Step four, the preparation of gradient cubic carbon nanotube-prussian blue-zinc oxide composite material includes the following steps:

[0183] 0.6 g of zinc gluconate was fully dissolved in a mixed solution of 100 mL deionized water and 70 mL ethanol under magnetic stirring, and 1 g of dried gradient structure carbon nanotube-prussian blue composite material was added, ultrasonic treatment was performed for 30 min and stirring was performed for 12 h to obtain a mixed solution.

[0184] The above mixed solution was placed in a rotary evaporator until all the solvent was evaporated.

[0185] The evaporated solid powder was heat treated in an argon atmosphere at 180°C for 5 hours in a tube furnace to obtain a second growth of gradient structure carbon nanotube-prussian blue-zinc oxide composite material.

[0186] The obtained composite material is washed with deionized water and ethanol for 3 times, dried in a vacuum drying oven at 60°C for 6 hours, and then dried in a vacuum drying oven at 110°C for 16 hours to obtain a carbon nanotube-Prussian blue-zinc oxide composite material with large particle size.

[0187] Example 6

[0188] Step 1, carboxylation of carbon nanotubes includes the following steps:

[0189] After mixing concentrated H2SO4 and H2O2 in a volume ratio of 3:1 (300 mL and 100 mL) uniformly, pour them into a 1000 mL flask containing 1 g of multi-walled carbon nanotubes, place the flask in an oil bath to heat to 100°C, and magnetically stir at constant temperature for 16 hours of reflux reaction. After the reaction is completed, cool to room temperature, centrifuge at a speed of 18000 r / min for 30 minutes, remove the supernatant, and disperse in deionized water again, repeat several times until the supernatant is neutral, and obtain carboxylated carbon nanotubes.

[0190] Step 2, first growth of carbon nanotube-Prussian blue composite material includes the following steps:

[0191] Under nitrogen protection, 0.5 g of carboxylated graphene in step 1 is dispersed in 50 mL of deionized water and acidified with hydrochloric acid to make its pH = 2. Then, soluble divalent manganese salt, soluble divalent iron salt, soluble sodium salt and surfactant are added, and after being fully dissolved, a mixed solution B is obtained. The molar ratio of the soluble divalent manganese salt, the soluble divalent iron salt, the soluble sodium salt and the surfactant is 6:16:6:0.004; the soluble divalent manganese salt is manganese chloride, the soluble divalent iron salt is ferrous sulfate, the surfactant is polyethylene glycol, the soluble sodium salt is sodium chloride, and the ferrous sulfate is 4.448 g.

[0192] Under nitrogen protection, 7.744 g of sodium ferrocyanide, soluble sodium salt and surfactant are fully dissolved in 100 mL of deionized water under magnetic stirring and acidified with hydrochloric acid to make its pH = 1 to obtain a mixed solution A. The molar ratio of sodium ferrocyanide, soluble sodium salt and surfactant is 4:3:0.0005, the soluble sodium salt is sodium chloride, and the surfactant is sodium dodecyl benzene sulfonate.

[0193] Under nitrogen protection, the soluble divalent manganese salt, the soluble sodium salt and the surfactant are fully dissolved in 50 mL of deionized water under magnetic stirring and acidified with hydrochloric acid to make its pH = 1 to obtain a mixed solution C. The molar ratio of the soluble divalent manganese salt, the soluble sodium salt and the surfactant is 16:10:0.005, the soluble divalent manganese salt is manganese nitrate, the soluble sodium salt is sodium chloride, the amount of sodium chloride is 0.362 g, and the surfactant is polyvinylpyrrolidone.

[0194] A liquid, B liquid through peristaltic pump respectively at 13.4 rpm, 8.1 rpm speed drop into C liquid, drop, stirring 24h, get carbon-prussian blue composite. The resulting carbon-prussian blue composite with deionized water and ethanol, vacuum drying, get dried carbon nanotube-prussian blue composite, ready for use. The temperature of the vacuum drying oven can be set to 200℃, the drying time can be set to 30 hours, the vacuum degree can be set to <133Pa.

[0195] Step three, the second growth of carbon nanotube-prussian blue composite includes the following steps:

[0196] Under the protection of nitrogen, the graphene-prussian blue composite 1g in step two is dispersed in 50mL deionized water. Under magnetic stirring, soluble divalent manganese salt, soluble sodium salt and surfactant are added in turn to make them fully dissolved to obtain mixed solution C. Among them, the soluble sodium salt is sodium citrate, and the sodium citrate is in a saturated state. The molar ratio of the soluble divalent manganese salt, the soluble sodium salt and the surfactant is 10:0.07:0.0003, the surfactant is PVP, the amount of PVP is 0.25g, and the soluble divalent manganese salt is manganese sulfate.

[0197] Under the protection of nitrogen, 30g of sodium citrate, one of the soluble divalent manganese salt and the soluble divalent nickel salt, the soluble divalent iron salt and the surfactant are fully dissolved in 50mL deionized water under magnetic stirring to obtain mixed solution B. Among them, the sodium citrate is in a saturated state. The molar ratio of the soluble divalent manganese salt, the soluble divalent iron salt, the soluble sodium salt (sodium citrate) and the surfactant is 6:1.6:10:0.0003. The soluble divalent manganese salt is manganese nitrate, the soluble divalent iron salt is ferrous sulfate, and the surfactant is polyethyleneimine.

[0198] Under the protection of nitrogen, 7.744g of sodium ferrocyanide, soluble sodium salt and surfactant are fully dissolved in 100mL deionized water under magnetic stirring to obtain mixed solution A. Among them, the soluble sodium salt is in a saturated state. The molar ratio of sodium ferrocyanide, soluble sodium salt and surfactant is 16:78:0.007. The soluble sodium salt is sodium citrate, and the surfactant is polyethyleneimine.

[0199] The mixed solution A and the mixed solution B are dropped into the mixed solution C through the peristaltic pump respectively at 13.4 rpm and 8.1 rpm, and stirred for 24h to obtain the secondly grown gradient structure carbon nanotube-prussian blue composite.

[0200] Step four, the preparation of gradient cubic carbon nanotube-prussian blue-zinc oxide composite includes the following steps:

[0201] Under magnetic stirring, 0.6 g of zinc gluconate was dissolved in a mixture of 100 mL of deionized water and 80 mL of ethanol, and 1 g of dry gradient-structured carbon nanotube-Prussian blue composite material was added. After ultrasonic treatment for 30 min and stirring for 12 h, a mixed solution was obtained.

[0202] The above mixed solution was placed in a rotary evaporator until all the solvent was evaporated.

[0203] The evaporated solid powder was heat-treated in an argon atmosphere at 120°C for 7 hours in a tube furnace to obtain a secondary growth gradient-structured carbon nanotube-Prussian blue-zinc oxide composite material.

[0204] The obtained composite material was washed with deionized water and ethanol for 3 times, dried in a vacuum drying oven at 60°C for 6 hours, and then placed in a drying oven at 110°C for vacuum drying for 16 hours to obtain a large-particle-size carbon nanotube-Prussian blue-zinc oxide composite material.

[0205] Example 7

[0206] Step 1, carboxylation of carbon nanotubes, includes the following steps:

[0207] After mixing concentrated H2SO4 and H2O2 in a volume ratio of 3:1 (300 mL and 100 mL), pour them into a 1000 mL flask containing 1 g of multi-walled carbon nanotubes. Place the flask in an oil bath and heat to 100°C. Stir constantly at a constant temperature for 16 h. After the reaction is completed, cool to room temperature, centrifuge at 18000 r / min for 30 min, remove the supernatant, and disperse in deionized water again. Repeat several times until the supernatant is neutral. Carboxylated carbon nanotubes are obtained.

[0208] Step 2, first growth of carbon nanotube-Prussian blue composite material, includes the following steps:

[0209] Under nitrogen protection, 0.5 g of carboxylated graphene in step 1 was dispersed in 50 mL of deionized water and acidified with hydrochloric acid to pH = 2. Then add soluble divalent manganese salt, soluble divalent iron salt, soluble sodium salt and surfactant. After being dissolved, a mixed solution B is obtained. The molar ratio of soluble divalent manganese salt, soluble divalent iron salt, soluble sodium salt and surfactant is 6:16:3:0.003; the soluble divalent manganese salt is manganese chloride, the soluble divalent iron salt is ferrous sulfate, and the surfactant is polyethylene glycol. The amount of ferrous sulfate is 4.448 g.

[0210] Under the protection of nitrogen, 7.744 g of sodium ferrocyanide, soluble sodium salt and surfactant were fully dissolved in 100 mL of deionized water under magnetic stirring and acidified with hydrochloric acid to make the pH = 1, to obtain mixed solution A. The molar ratio of sodium ferrocyanide, soluble sodium salt and surfactant is 4:1:0, and the soluble sodium salt is sodium chloride.

[0211] Under the protection of nitrogen, the soluble divalent manganese salt, the soluble sodium salt and the surfactant were fully dissolved in 50 mL of deionized water under magnetic stirring and acidified with hydrochloric acid to make the pH = 1, to obtain mixed solution C. Among them, the molar ratio of the soluble divalent manganese salt, the soluble sodium salt and the surfactant is 16:20:0, the soluble divalent manganese salt is manganese acetate, the soluble sodium salt is sodium chloride, and the amount of sodium chloride is 0.362 g.

[0212] A solution, B solution was added dropwise into C solution at a speed of 13.4 rpm and 8.1 rpm respectively by peristaltic pump, and stirred for 24 h, to obtain carbon-prussian blue composite material. The obtained carbon-prussian blue composite material was washed with deionized water and ethanol, and vacuum dried to obtain dried carbon nanotube-prussian blue composite material, which was used for standby. The temperature of the vacuum drying box can be set to 230℃, the drying time can be set to 20 hours, and the vacuum degree can be set to <133 Pa.

[0213] Step three, the second growth of carbon nanotube-prussian blue composite material includes the following steps:

[0214] Under the protection of nitrogen, 7.744 g of sodium ferrocyanide, soluble sodium salt and surfactant were fully dissolved in 100 mL of deionized water under magnetic stirring and acidified with hydrochloric acid to make the pH = 1, to obtain mixed solution A. The molar ratio of sodium ferrocyanide, soluble sodium salt and surfactant is 4:1:0, and the soluble sodium salt is sodium chloride.

[0215] Under the protection of nitrogen, 7.744 g of sodium ferrocyanide, soluble sodium salt and surfactant were fully dissolved in 100 mL of deionized water under magnetic stirring and acidified with hydrochloric acid to make the pH = 1, to obtain mixed solution A. The molar ratio of sodium ferrocyanide, soluble sodium salt and surfactant is 4:1:0, and the soluble sodium salt is sodium chloride.

[0216] Under the protection of nitrogen, 7.744 g of sodium ferrocyanide, soluble sodium salt and surfactant were fully dissolved in 100 mL of deionized water under magnetic stirring to obtain mixed solution A. Among them, the sodium citrate was in a saturated state. The molar ratio of sodium ferrocyanide, soluble sodium salt and surfactant was 16:78:0. The soluble sodium salt was sodium citrate.

[0217] Mixed solution A and mixed solution B were added dropwise into mixed solution C at a speed of 13.4 rpm and 8.1 rpm respectively through a peristaltic pump under stirring for 24 h to obtain the second-growth gradient structure carbon nanotube-prussian blue composite material.

[0218] Step four, the preparation of the gradient cubic carbon nanotube-prussian blue-zinc oxide composite material includes the following steps:

[0219] Under magnetic stirring, 0.6 g of zinc gluconate was fully dissolved in a mixture of 100 mL of deionized water and 90 mL of ethanol, and 1 g of dried gradient structure carbon nanotube-prussian blue composite material was added. Ultrasonic for 30 min and stir for 12 h to obtain a mixed solution.

[0220] The above mixed solution was placed in a rotary evaporator until all the solvent was evaporated.

[0221] The evaporated solid powder was heat treated in an argon atmosphere at 200°C in a tube furnace for 4 hours to obtain the second-growth gradient structure carbon nanotube-prussian blue-zinc oxide composite material.

[0222] The obtained composite material was washed with deionized water and ethanol for 3 times, dried in a vacuum drying oven at 60°C for 6 hours, and then placed in a vacuum drying oven at 110°C for 16 hours to obtain the large-particle-size carbon nanotube-prussian blue-zinc oxide composite material. The specific embodiments of the present application are described above. It should be noted that the present application is not limited to the above specific embodiments, and those skilled in the art can make various substitutions or modifications within the scope of the claims, and the corresponding technical solutions do not deviate from the scope of the present application, and are all covered within the protection scope of the present application.

Claims

1. A method for preparing a carbon-prussian blue-zinc oxide composite material with a large particle size, characterized in that, The method comprises the following steps: 1) modifying a carbon source; 2) growing Prussian blue crystals on the surface of the modified carbon source to obtain a primary growth carbon-Prussian blue composite material; 3) growing Prussian blue crystals on the surface of the primary growth carbon-Prussian blue composite material to obtain a secondary growth carbon-Prussian blue composite material; 4) dissolving a soluble zinc salt in a solvent under stirring, then adding the secondary growth carbon-Prussian blue composite material, uniformly dispersing, removing the solvent, and then heating to obtain a carbon-Prussian blue-zinc oxide composite material.

2. The method for preparing a large-particle-size carbon-prussian blue-zinc oxide composite material according to claim 1, characterized by, The specific process of modifying the carbon source is as follows: the carbon nanotube, graphene or carbon fiber is modified by sulfuric acid and hydrogen peroxide to make the carbon source carry a negative group, and the modified carbon source is obtained.

3. The method for preparing the large-particle-size carbon-Prussian blue-zinc oxide composite material according to claim 1, characterized in that, The specific process of step 2) is as follows: under nitrogen protection, sodium ferrocyanide, a soluble sodium salt and a surfactant are dissolved in deionized water to form a mixed solution A with a pH of 1-3; Under nitrogen protection, one of a soluble divalent manganese salt and a soluble divalent nickel salt, a soluble divalent iron salt, a soluble sodium salt and a surfactant are dissolved in deionized water to obtain a solution, and the modified carbon nanotube is dispersed in the solution to form a mixed solution B with a pH of 1-3; Under nitrogen protection, one of a soluble divalent manganese salt and a soluble divalent nickel salt, a soluble sodium salt and a surfactant are dissolved in deionized water to form a mixed solution C with a pH of 1-3; The mixed solution A, the mixed solution B and the mixed solution C are mixed and dried to obtain the primary growth carbon-Prussian blue composite material.

4. The method for preparing a large-particle-size carbon-prussian blue-zinc oxide composite material according to claim 3, characterized by, The specific process of step 3) is as follows: under nitrogen protection, sodium ferrocyanide, a soluble sodium salt and a surfactant are dissolved in deionized water to obtain a mixed solution A; Under nitrogen protection, one of a soluble divalent manganese salt and a soluble divalent nickel salt, a soluble divalent iron salt, a soluble sodium salt and a surfactant are dissolved in deionized water to obtain a mixed solution B; Under nitrogen protection, one of a soluble divalent manganese salt and a soluble divalent nickel salt, a soluble sodium salt, the primary growth carbon-Prussian blue composite material and a surfactant are dissolved in deionized water to form a mixed solution C; The mixed solution A, the mixed solution B and the mixed solution C are mixed and stirred, and then dried to obtain the secondary growth carbon-Prussian blue composite material.

5. The method for preparing a large-particle-size carbon-prussian blue-zinc oxide composite material according to claim 4, characterized by, In step 2), the molar ratio of the soluble sodium salt, the sodium ferrocyanide and the soluble divalent iron salt is (0-25):16:(16-20); In steps 2) and 3), the soluble sodium salt is one or more of sodium citrate, sodium chloride, sodium ascorbate and sodium sulfate; In steps 2) and 3), the surfactant is one or more of polyvinylpyrrolidone, polyethylene glycol, sodium dodecylbenzenesulfonate, polyethyleneimine and sodium hexadecylsulfate; the molecular weight of the polyvinylpyrrolidone is 45,000-58,000; In steps 2) and 3), the soluble divalent iron salt is one or more of ferrous chloride, ferrous sulfate, ferrous nitrate and ferrous acetate; In steps 2) and 3), the soluble divalent manganese salt is one or more of manganese chloride, manganese sulfate, manganese nitrate and manganese acetate. The soluble divalent nickel salt in steps 2) and 3) is one or more of nickel chloride, nickel sulfate, nickel nitrate and nickel acetate.

6. The method for preparing the large-particle-size carbon-Prussian blue-zinc oxide composite material according to claim 1, characterized in that, In step 3), the soluble sodium salt in the mixed solution A, the mixed solution B and the mixed solution C is in a saturated state; in step 3), the total concentration of one of the soluble divalent manganese salt and the soluble divalent nickel salt, the soluble divalent iron salt and the soluble sodium salt in the mixed solution B is 2-4 mol / L; in step 3), the total concentration of one of the soluble divalent manganese salt and the soluble divalent nickel salt and the soluble sodium salt in the mixed solution C is 1.9-3.8 mol / L.

7. The method for preparing the large-particle-size carbon-Prussian blue-zinc oxide composite material according to claim 1, characterized in that, In step 4), the solvent is a mixture of ethanol and water in a volume ratio of 0.5:1-1:1; the soluble zinc salt is one or more of zinc acetate, zinc oxalate, zinc citrate and zinc gluconate; the heating treatment is carried out under an argon atmosphere, the heating treatment temperature is 100-200°C, and the heating treatment time is 4-8 h.

8. The carbon-prussian blue-zinc oxide composite material prepared according to the preparation method of any one of claims 1-7, characterized in that, The carbon-prussian blue-zinc oxide composite material has a gradient cubic structure, the size of prussian blue grains in the carbon-prussian blue-zinc oxide composite material is 500 nm-3 μm, and the prussian blue morphology includes cubic type and spherical shape.

9. A cathode material for a sodium-ion battery, characterized in that, The positive electrode material is the carbon-prussian blue-zinc oxide composite material according to claim 8.

10. A sodium-ion battery, characterized in that, The battery comprises a separator, an electrolyte, a positive electrode and metal sodium as a negative electrode, and the material of the positive electrode is the carbon-prussian blue-zinc oxide composite material according to claim 8.

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