Sodium ion capacitor positive electrode material and preparation method and application thereof

Abstract

The invention discloses a sodium ion capacitor positive electrode material and a preparation method and application thereof. The preparation method comprises the following steps: mixing and coking heavy oil and an auxiliary agent to obtain a material flow A; then carrying out activating treatment on the material flow A and an activating agent, and washing and drying to obtain a material B; and mixing the material B with the precursor solution C, and drying and roasting the obtained mixture to obtain the sodium ion capacitor positive electrode material. The sodium ion capacitor positive electrode material obtained by the method has high specific capacity, and can greatly improve the energy density when being applied to a sodium ion capacitor.

Description

Technical Field

[0001] The invention belongs to the technical field of new energy and relates to a positive electrode material for a sodium ion capacitor and a preparation method thereof. Background Art

[0002] Renewable energy such as wind energy, solar energy, and tidal energy are gradually becoming popular, but most renewable energy obtained from nature is volatile and discontinuous, making it difficult to directly enter the power grid and requiring coupling with an energy storage system. Supercapacitors are a type of electrochemical energy storage method with rapid response capabilities, suitable for smoothing fluctuations in renewable energy, and have high charging and discharging power, long service life, and a wide range of applications. At present, the energy density of traditional double-layer supercapacitors is not high and the cost is high, which limits the popularity of supercapacitors in the field of energy storage. Mixing double-layer supercapacitors with sodium-ion battery materials to form a sodium-ion capacitor can increase the energy density of supercapacitors and reduce the cost per unit power density.

[0003] Normally, the positive electrode of sodium ion capacitors uses porous carbon that can store double-layer electrostatic adsorption energy, and the negative electrode uses amorphous carbon that can be embedded in sodium ion batteries for sodium storage. The specific capacity of porous carbon for electrostatic adsorption energy storage is often lower than that of amorphous carbon embedded in sodium storage, making it the key to improve sodium ion capacitors. The reversible specific capacity of porous carbon positive electrodes in sodium ion capacitors is generally 30 to 70 mAh / g, which is mainly limited by the specific surface area of ​​the material. However, increasing the specific surface area to 3000m 2 / g is the limit of electrostatic adsorption energy storage. Composite porous carbon and sodium iron pyrophosphate, the positive electrode material of sodium ion battery, is an effective solution. At the same time, through the pore design of porous carbon, the loading sites of sodium iron pyrophosphate are limited in the pores, which can improve the conductivity, reduce the particle size, and improve the electrochemical performance of the composite electrode material.

[0004] CN114975973A relates to a modified high-performance sodium iron pyrophosphate sodium ion battery positive electrode material and its preparation and application. The modified high-performance sodium iron pyrophosphate sodium ion battery positive electrode material is prepared by a high-temperature solid phase method. 2 FeP 2 O 7 The surface of the 2 FeP 2 O 7 The surface is loaded with carbon nanotubes to form a through-conductive network, and a modified high-performance sodium iron pyrophosphate sodium ion battery positive electrode material is obtained. It is difficult to reduce the particle size of sodium iron pyrophosphate by high-temperature solid-phase surface carbon coating. The larger particle size makes the internal conductivity of sodium iron pyrophosphate particles poor, reducing the energy density of the material. Summary of the invention

[0005] In view of the problems and shortcomings existing in the prior art, the core purpose of the present invention is to provide a sodium ion capacitor positive electrode material and a preparation method thereof. The obtained sodium ion capacitor positive electrode material has a high specific capacity, solves the problems of poor electronic conductivity of sodium iron pyrophosphate and slow sodium ion transmission, and thus can improve the specific capacity of the sodium ion capacitor positive electrode and the energy density of the sodium ion capacitor.

[0006] The technical solution of the present invention mainly includes the following aspects, and the specific technical solution is as follows:

[0007] (1) A method for preparing a positive electrode material for a sodium ion capacitor, the method comprising the following steps:

[0008] S1, mixing heavy oil with an additive and performing coking treatment to obtain a material stream A;

[0009] S2, mixing the material stream A with the activating agent and performing activation treatment, after the activation is completed, washing and drying to obtain material B;

[0010] S3, uniformly mixing the iron precursor, the sodium precursor, the phosphoric acid source, and the solvent to obtain a precursor solution C;

[0011] S4. Mix material B with precursor solution C, and obtain the positive electrode material of sodium ion capacitor after drying and calcining the obtained mixed material.

[0012] As a specific implementation, in the above method for preparing the positive electrode material of the sodium ion capacitor, the heavy oil in step S1 can be selected from one or more of petroleum asphalt, ethylene tar, catalytic cracking slurry, vacuum residue oil, etc.

[0013] As a specific implementation scheme, in the preparation method of the above-mentioned sodium ion capacitor positive electrode material, the auxiliary agent in step S1 includes but is not limited to one or more of silicon dioxide, iron oxide, zinc oxide, magnesium oxide, etc., and the auxiliary agent is a nano-sized particle. More specifically, the auxiliary agent size is 5 to 50 nm.

[0014] As a specific implementation scheme, in the method for preparing the positive electrode material of the sodium ion capacitor, the mass ratio of the heavy oil to the auxiliary agent in step S1 is 50:1 to 1:3, preferably 10:1 to 1:2.

[0015] As a specific implementation, in the method for preparing the positive electrode material of the sodium ion capacitor, the coking treatment temperature of the heavy oil and the auxiliary agent in step S1 is 400-600°C, preferably 450-550°C.

[0016] As a specific implementation, in the method for preparing the positive electrode material of the sodium ion capacitor, the material stream A obtained in step S1 is preferably crushed, generally to a particle size of 200 to 50 μm.

[0017] As a specific implementation, in the method for preparing the positive electrode material of the sodium ion capacitor, the activator in step S2 is one or more of potassium hydroxide, potassium carbonate, potassium bicarbonate, zinc chloride and phosphoric acid, preferably potassium hydroxide.

[0018] As a specific implementation scheme, in the above-mentioned method for preparing the positive electrode material of the sodium ion capacitor, the ratio between the material flow A and the activator during the activation treatment in step S2 can generally be carried out under the condition of a mass ratio of 1:4 to 4:1.

[0019] As a specific embodiment, in the preparation method of the above-mentioned sodium ion capacitor positive electrode material, the temperature of the activation treatment of the material stream A and the activator during the activation treatment in step S2 is 700-1000°C, preferably 800-900°C, and the activation is carried out under inert atmosphere protection conditions, and the inert atmosphere can be nitrogen and / or inert gas.

[0020] As a specific implementation scheme, in the preparation method of the positive electrode material of the above-mentioned sodium ion capacitor, the washing in step S2 includes two steps. The first step is acid washing or alkali washing, the purpose of which is to remove the residual auxiliary agent, and the auxiliary agent is selected according to the reaction ability of the auxiliary agent with the acid / or alkali. If the auxiliary agent used is silicon dioxide nanoparticles, an alkali washing method is adopted, and the alkali is an inorganic alkali, which can be any one of NaOH solution and hydrofluoric acid solution; if the auxiliary agent used is nanoparticles of iron oxide, zinc oxide, and magnesium oxide, an acid washing method can be adopted, and the acid is an inorganic acid solution, which can be at least one of hydrochloric acid solution, sulfuric acid solution, hydrobromic acid solution, and hydrofluoric acid solution. The concentration of the acid solution or the alkali solution can generally be controlled to be 1 to 4 mol / L; the second step is to wash with water until the filtrate is neutral. The washing can be carried out at 20 to 95°C, preferably 50 to 95°C, and further stirring can be performed during the washing process to improve efficiency.

[0021] As a specific implementation scheme, in the above-mentioned method for preparing the positive electrode material of the sodium ion capacitor, the drying in step S2 is generally carried out under the following conditions: the drying temperature is 60 to 140° C., and the drying time is 2 to 24 hours.

[0022] As a specific implementation scheme, in the preparation method of the positive electrode material of the sodium ion capacitor, the material B obtained after drying in step S2 is porous carbon, and the pore size distribution of the material B has the following characteristics: the pore volume occupied by the mesopores is 20% to 70% of the total pore volume of the micropores and mesopores, and more preferably 30% to 50%; wherein the pore size of the mesopores is 2 to 50 nm, and the pore size of the micropores is less than 2 nm. Its specific surface area is 400 to 3300 m 2 / g, preferably 1000 to 2500 m 2 / g.

[0023] As a specific implementation scheme, in the preparation method of the above-mentioned sodium ion capacitor positive electrode material, the iron precursor in step S3 is an iron salt, which can be an inorganic iron salt and / or an organic iron salt. More specifically, the iron precursor can be selected from one or more of ferric chloride, ferric nitrate, ferric sulfate, ferric oxalate, ferrous acetate, ferrous oxalate, ammonium ferrous sulfate, and ferric pyrophosphate, preferably ferric chloride.

[0024] As a specific implementation scheme, in the above-mentioned method for preparing the positive electrode material of the sodium ion capacitor, the phosphate source in step S3 can be selected from one or more of phosphoric acid, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, ferrous phosphate, ammonium phosphate, diammonium hydrogen phosphate, sodium ammonium hydrogen phosphate, and diammonium phosphate, preferably phosphoric acid.

[0025] As a specific implementation scheme, in the preparation method of the above-mentioned sodium ion capacitor positive electrode material, the sodium precursor in step S3 is a sodium salt, which can be an inorganic sodium salt and / or an organic sodium salt, and can be specifically selected from sodium chloride, sodium nitrate, sodium nitrite, sodium sulfate, sodium hydroxide, sodium bromide, sodium ethoxide, sodium methoxide, sodium acetate, sodium formate, sodium oxalate, sodium oleate, sodium pyrosulfate, sodium pyrophosphate, and sodium bicarbonate. One or more, preferably one or more of sodium chloride, sodium nitrate, and sodium acetate.

[0026] As a specific implementation scheme, in the above-mentioned method for preparing the positive electrode material of the sodium ion capacitor, the solvent in step S3 is water and / or an organic solvent, and the organic solvent can be one or more of ethanol, acetone, methanol, ethylene glycol, n-propanol, and isopropanol.

[0027] As a specific embodiment, in the method for preparing the positive electrode material of the sodium ion capacitor, the molar ratio of the iron precursor, the sodium precursor, and the phosphoric acid source in step S3 can be based on the molecular composition of sodium iron pyrophosphate Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 Determine; the obtained precursor solution C is a sodium iron pyrophosphate precursor solution.

[0028] As a specific implementation scheme, in the preparation method of the positive electrode material of the sodium ion capacitor, the mass ratio of the material B to the precursor solution C in step S4 is 1:4 to 4:1. The precursor solution C is contacted with the powdered material B for impregnation treatment, preferably by multiple impregnations to ensure that the precursor solution C is fully absorbed by the pores of the material B.

[0029] As a specific implementation scheme, in the above-mentioned method for preparing the positive electrode material of the sodium ion capacitor, the drying conditions in step S4 are: the drying temperature is 60 to 150° C., preferably 80 to 120° C.; the drying time is 1 to 24 hours, preferably the drying time is 2 to 12 hours.

[0030] As a specific implementation, in the preparation method of the positive electrode material of the sodium ion capacitor, the calcination in step S4 is carried out under the conditions of an inert atmosphere and a reducing atmosphere, wherein the reducing atmosphere is a mixed gas of hydrogen and an inert atmosphere, and the volume content of hydrogen in the mixed gas is 1 to 50%; the inert atmosphere is nitrogen and / or an inert gas, and the inert gas is at least one of helium, argon, and neon. The calcination conditions are: the calcination temperature is 300 to 1000°C, preferably 500 to 800°C; the calcination time is 0.5 to 8 hours, preferably 1 to 4 hours.

[0031] As a specific implementation scheme, in the preparation method of the above-mentioned sodium ion capacitor positive electrode material, after the material B is mixed with the precursor solution C in step S4, it is preferably heat-treated under the condition of an alkaline atmosphere, and the material stream obtained after the treatment is further dried and calcined to obtain the positive electrode material; the alkaline atmosphere can be at least one of ammonia, ammonium carbonate, ammonium bicarbonate, and ethylenediamine; preferably ammonia; the heat treatment temperature is 50 to 160°C, preferably 60 to 120°C.

[0032] The second aspect of the present invention provides a sodium ion capacitor positive electrode material obtained by the above-mentioned preparation method.

[0033] A third aspect of the present invention provides a sodium ion battery, which comprises the sodium ion capacitor positive electrode material obtained by the above preparation method.

[0034] Compared with the prior art, the technical advantages of the sodium ion capacitor positive electrode material and the preparation method thereof provided by the present invention are embodied in the following aspects:

[0035] 1. In the preparation method of the positive electrode material of the sodium ion capacitor provided by the present invention, the fluidity of the heavy oil is first used to fully disperse and wrap the additive, and then after high-temperature coking, activation, and washing, a large number of mesopores will be formed in situ in the carbon material after the additive is removed to obtain porous carbon with high mesopore content, while solving the problem that the precursor solution in the pores is easily saturated during the loading of sodium iron phosphate pyrophosphate, and the particles are easily aggregated outside the porous carbon, resulting in the excessive size of the sodium iron phosphate pyrophosphate particles. The particle size of the sodium iron phosphate pyrophosphate is reduced by the confining effect of the pores, and the electrochemical properties of the composite material are improved. Furthermore, by regulating the volume ratio of mesopores to micropores in the porous carbon, the loading ratio of the sodium iron phosphate pyrophosphate can be regulated.

[0036] 2. In the method for preparing the positive electrode material of the sodium ion capacitor provided by the present invention, sodium iron phosphate pyrophosphate is synthesized by an in-situ hydrolysis method (liquid phase dissolution-in-situ hydrolysis-high temperature calcination) in a conductive carrier, which solves the problem that the ion distribution of sodium iron phosphate pyrophosphate synthesized by the traditional solid phase method, precipitation method and sol-gel method is not uniform and the particle size is large. Utilizing the capillary action of the porous carbon material, the sodium iron phosphate pyrophosphate solution is absorbed into the porous carbon material, and the precursor is formed by in-situ hydrolysis and high-temperature calcination, so that the high dispersion and nano-size of sodium iron phosphate pyrophosphate can be achieved. The existing synthesis method can only synthesize particles with a size of about 100 nanometers after high-energy ball milling, and the specific surface area of ​​the carbon introduced by the surface carbon coating to improve the conductivity is not high, and it cannot provide capacity. It is an inactive substance, which leads to a decrease in the mass specific capacity of the material. The present invention proposes to introduce sodium ferric phosphate pyrophosphate into the porous carbon pores, and composite sodium ferric phosphate pyrophosphate, a sodium ion battery positive electrode material (whose theoretical specific capacity can reach 120 mAh / g), in the porous carbon positive electrode, thereby effectively improving the specific capacity of the positive electrode of the sodium ion capacitor, and further improving the electronic conductivity of sodium ferric phosphate pyrophosphate by composite carbon and other conductive materials, and improving the problem of slow sodium ion transmission by reducing the particle size of sodium ferric phosphate pyrophosphate. Comprehensively utilizing the double-layer capacitance, good conductivity and carrier effect of porous carbon, and utilizing the high specific capacity of sodium ferric phosphate pyrophosphate, the two materials can achieve a common optimization effect.

[0037] 3. The sodium ion capacitor positive electrode material provided by the present invention can improve the tap density of the material and the volume energy density of the device. While the sodium ion battery positive electrode material fills the large-sized pores, most of the micropores are retained, so that the porous carbon of the double-layer capacitor and the sodium ion embedded battery material can work together in the sodium ion capacitor. The two are equivalent to parallel connection, which complement each other in terms of power and energy, and smooth the impact of power load fluctuations on energy storage devices. Compared with the use of sodium ion battery positive electrode materials alone, the method of the present invention can improve the conductivity of sodium ion battery positive electrode materials and reduce safety issues caused by resistive heating.

[0038] 4. In the method for preparing the positive electrode material of a sodium ion capacitor provided by the present invention, by introducing a sodium iron pyrophosphate precursor into the pores of porous carbon, the grain size of the sodium iron pyrophosphate can be reduced through the confinement effect of the porous carbon pores, thereby effectively improving the rate performance of the composite material, thereby increasing the energy density of the sodium ion capacitor while retaining a high power density.

[0039] 5. In the method for preparing the positive electrode material of a sodium ion capacitor provided by the present invention, the rate performance of the material can be improved by pretreating the porous carbon powder impregnated with the sodium iron pyrophosphate solution in an alkaline atmosphere. Pretreatment in an alkaline environment can convert the sodium iron pyrophosphate precursor solution into a precursor in situ, and improve the dispersion of the particles, so that the solid phase diffusion path of sodium ions in the particles is reduced, and the porous carbon surface is used to construct a conductive network of sodium iron pyrophosphate particles to solve the problem of low conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is an XRD comparison diagram of the samples obtained in Example 1 of the present invention (petroleum coke-based mesoporous porous carbon loaded with sodium ferric phosphate pyrophosphate) and Comparative Example 1 (ordinary porous carbon loaded with sodium ferric phosphate pyrophosphate).

[0041] Figure 2 It is a constant current charge and discharge curve diagram of the ordinary petroleum coke-based porous carbon sample before loading in Example 1 of the present invention and the petroleum coke-based mesoporous-rich porous carbon loaded with sodium iron phosphate pyrophosphate sample obtained in Example 1.

[0042] Figure 3 dQ / dV curves of the ordinary petroleum coke-based porous carbon sample before loading in Example 1 of the present invention and the petroleum coke-based mesoporous-rich porous carbon loaded with sodium iron phosphate pyrophosphate sample obtained in Example 1. DETAILED DESCRIPTION

[0043] The technical content and effects of the present invention are further illustrated below in conjunction with embodiments, but the present invention is not limited thereby.

[0044] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings and specific embodiments. However, it should be pointed out that the protection scope of the present invention is not limited by these specific implementation modes, but is determined by the claims.

[0045] In the context of this specification, pore volume, specific surface area and pore size distribution are measured using a low temperature nitrogen adsorption method.

[0046] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this specification are based on weight.

[0047] In the context of this specification, any two or more embodiments of the present invention may be arbitrarily combined, and the technical solutions thus formed belong to part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0048] Example 1

[0049] 600g of catalytic cracking oil slurry and 300g of nano-silicon dioxide (particle diameter 12nm) were fully stirred and mixed, and then delayed coking at 480℃ for 24 hours to generate petroleum coke uniformly doped with nanoparticles; the generated petroleum coke stream was crushed and mixed with potassium hydroxide at a mass ratio of 1:1.5, and heated to 900℃ in a nitrogen atmosphere for 2 hours to activate the petroleum coke by one step. The generated product was soaked in a 1mol / L potassium hydroxide aqueous solution to remove the residual nanoparticles, washed with water to neutrality and then dried to obtain petroleum coke-based porous carbon. Weigh 82.0g of anhydrous sodium acetate, dissolve it in 100mL of deionized water, add 202.5g of ferric chloride hexahydrate, add 149.1g of ammonium phosphate, and adjust the volume to 500mL to prepare a precursor solution. Weigh 200g of the obtained petroleum coke-based porous carbon powder (specific surface area 2852m 2 / g, pore volume 1.81cm 3 / g, mesoporous volume ratio is 45%), put it in an oven and dry it at 100℃ for 5 hours. Add 500mL of precursor solution dropwise to porous carbon powder, mix the two evenly, and dry the mixture in an oven at 100℃ for 5 hours. Put the mixture in a tube furnace and calcine it at 600℃ for 2 hours under argon atmosphere. The product is marked as PC / NFP-1, and the XRD pattern of the sample is shown in Figure 1 .

[0050] Combination Figure 1 According to the Scherrer formula (D = 0.89λ / (B cosθ), D is the grain size (nm), B is the half-height width of the diffraction peak, θ is the Bragg angle, λ is the wavelength of the X-ray used The crystallinity of the sodium ferric phosphate pyrophosphate in Example 1 is 10 nm (calculated based on the main diffraction peak of 2-theta=33.1°), which is lower than 12 nm of the sample in Comparative Example 1, which is beneficial to the rate performance of the sodium ferric phosphate pyrophosphate. In addition, the diffraction peak intensity of Example 1 is low and the visible diffraction peaks are few, so in addition to the crystalline sodium ferric phosphate pyrophosphate, it may contain a large amount of amorphous sodium ferric phosphate pyrophosphate.

[0051] pass Figure 2 It can be seen that the reversible specific capacity of the pure porous carbon sample before loading is 78.4 mAh / g, and the reversible specific capacity of the petroleum coke-based mesoporous porous carbon loaded with sodium iron phosphate pyrophosphate is 101.8 mAh / g, and the specific capacity of loaded sodium iron phosphate pyrophosphate is increased by 30%. In addition, the sample loaded with sodium iron phosphate pyrophosphate has a small platform between 2.7V and 3.3V, corresponding to the sodium insertion and extraction reaction of sodium iron phosphate pyrophosphate.

[0052] pass Figure 3It can be seen that the pure porous carbon sample before loading is mainly contributed by the double-layer capacitance. In contrast, the petroleum coke-based mesoporous carbon-loaded sodium iron pyrophosphate sample shows a redox peak between 2.7 and 3.3 V, representing the sodium insertion and extraction reaction of sodium iron pyrophosphate.

[0053] Example 2

[0054] 600g of ethylene tar and 300g of nano-iron oxide (particle diameter 20nm) were fully stirred and mixed, and then delayed coking at 500℃ for 20 hours to generate petroleum coke uniformly doped with nanoparticles; the generated petroleum coke stream was crushed to about 100 microns, and the generated product was soaked in 1mol / L dilute hydrochloric acid to remove residual nanoparticles, washed with water to neutrality and then dried, mixed with potassium hydroxide at a mass ratio of 1:2, heated to 900℃ under a nitrogen atmosphere and retained for 2 hours, and the petroleum coke was activated by one-step carbonization. The product was washed with water to remove residual potassium hydroxide, washed with 1mol / L dilute hydrochloric acid to further remove residual nano-iron oxide, and finally washed with water to neutrality to obtain petroleum coke-based porous carbon. Weigh 58.4g of sodium chloride, dissolve it in 100mL of deionized water, add 108.0g of ferrous oxalate, add 115.3g of 85wt% phosphoric acid, dilute to 500mL, and prepare a precursor solution. Weigh 200g of petroleum coke-based porous carbon powder (specific surface area 2538m 2 / g, pore volume 2.23cm 3 / g, mesoporous volume accounts for 58%), put it in an oven and dry it at 120°C for 12 hours. Add 500mL of precursor solution dropwise to the porous carbon powder and mix the two evenly. Take 500mL of 25wt% concentrated ammonia water and put it in beaker A, put the mixture in beaker B, put the two beakers in a sealed plastic bucket, put the plastic bucket in a 100°C blast oven for 12 hours, take out beaker B, put it in a 120°C blast oven after 12 hours, and put it in a tube furnace under an argon atmosphere at 700°C for 2 hours. The mixture is placed in a tube furnace and baked at 700°C for 2 hours under an argon atmosphere. The product is marked as PC / NFP-N-1.

[0055] Example 3

[0056] 300g of nano-magnesium oxide (particle diameter 15nm) was dispersed in 200mL of diesel, and then fully stirred and mixed with 800g of catalytic cracking oil slurry, and then delayed coking at 500℃ for 24 hours to generate petroleum coke uniformly doped with nano-magnesium oxide; the generated petroleum coke stream was crushed to about 100 mesh, and the generated product was soaked in 1mol / L dilute hydrochloric acid to remove residual nanoparticles, washed with water to neutrality and then dried, mixed with potassium carbonate at a mass ratio of 1:2, heated to 900℃ under nitrogen atmosphere for 2 hours, and activated petroleum coke by one step of carbonization. The product was washed with water to remove residual potassium hydroxide, and finally washed with water to neutrality to obtain petroleum coke-based porous carbon. Weigh 58.4g of sodium chloride, dissolve it in 100mL of deionized water, add 202.5g of ferric chloride hexahydrate, add 115.3g of 85% phosphoric acid, and dilute to 600mL to prepare a precursor solution. Weigh 250g of the petroleum coke-based porous carbon powder obtained above and put it into an oven to dry at 100°C for 5 hours. Add the precursor solution dropwise to the porous carbon powder, mix the two evenly, and dry the mixture in an oven at 100°C for 5 hours. Place the mixture in a tube furnace and calcine at 600°C for 2 hours under an argon atmosphere. The product is marked as PC / NFP-2.

[0057] Example 4

[0058] 100g of nano-silicon dioxide (particle diameter 15nm) was dispersed in 200mL of diesel, and then fully stirred and mixed with 600g of catalytic cracking oil slurry, and then delayed coking at 500℃ for 24 hours to generate petroleum coke uniformly doped with nano-silicon dioxide; the generated petroleum coke stream was crushed to about 200 microns, and the generated product was soaked in a 1mol / L potassium hydroxide aqueous solution to remove residual nano-silicon dioxide, washed with water to neutrality and then dried, mixed with potassium hydroxide at a mass ratio of 1:2, heated to 900℃ in a nitrogen atmosphere and retained for 2 hours, and the petroleum coke was activated by one-step carbonization. The product was washed in a 1mol / L potassium hydroxide aqueous solution to further remove residual nano-silicon dioxide, and finally washed with water to neutrality, and dried to obtain petroleum coke-based porous carbon. Weigh 82.0g of anhydrous sodium acetate and dissolve it in 200mL of deionized water. Add 202.5g of ferric chloride hexahydrate and 115.3g of 85wt% phosphoric acid. Stir. Add 50mL of ethanol and dilute to 450mL to prepare a precursor solution. Weigh 200g of the petroleum coke-based porous carbon powder (specific surface area 2212m 2 / g, pore volume 1.71cm 3 / g, mesoporous volume ratio is 30%), put it in an oven and dry it at 100°C for 5 hours. 450mL of the precursor solution was added dropwise to the porous carbon powder, the two were evenly mixed, and put it in a tube furnace and calcined at 500°C for 3 hours under an argon atmosphere. The product is marked as PC / NFP-3.

[0059] Example 5

[0060] 50g of nano zinc oxide (particle diameter 20nm) and 100g of nano silicon dioxide (particle diameter 7nm) were dispersed in 200mL of diesel, and then fully stirred and mixed with 500g of petroleum asphalt, and then delayed coking at 500℃ for 24 hours to generate petroleum coke uniformly doped with nano silicon dioxide; the generated petroleum coke stream was crushed to about 300 mesh, washed with water to neutrality and then dried, mixed with potassium hydroxide at a mass ratio of 1:2, heated to 900℃ under nitrogen atmosphere and retained for 2 hours, and activated the petroleum coke by one step of carbonization. The product was washed with 1mol / L potassium hydroxide aqueous solution to remove nano silicon dioxide, and then washed with 1mol / L dilute hydrochloric acid solution to remove nano zinc oxide, and finally washed with water to neutrality, and dried to obtain petroleum coke-based porous carbon. Weigh 58.4g of sodium chloride, dissolve it in 100mL of deionized water, add 303g of ferric nitrate nine hydrate, add 115.3g of 85wt% phosphoric acid, and dilute to 400mL to prepare a precursor solution. Weigh 200 g of the petroleum coke-based porous carbon powder (specific surface area 2827 m 2 / g, pore volume 1.98cm 3 / g, mesoporous volume accounts for 45%), put it in an oven and dry it at 100°C for 5 hours. Add 400mL of precursor solution dropwise to the porous carbon powder, mix the two evenly, and dry the mixture in a 100°C oven for 5 hours. Take 300g of ammonium bicarbonate powder and put it in beaker A, put the mixture in beaker B, put the two beakers in a sealed plastic bucket, put the plastic bucket in a 100°C blast oven for 12 hours, take out beaker B, and after 6 hours in a 100°C blast oven, put the mixture in a tubular furnace and calcine it at 500°C for 1 hour in an atmosphere of 90% argon / 10% hydrogen by volume. The product is marked as PC / NFP-N-2.

[0061] Example 6

[0062] 700g of ethylene tar and 300g of nano-silicon dioxide (particle diameter 12nm) were fully stirred and mixed, and then delayed coking at 480℃ for 24 hours to generate petroleum coke uniformly doped with nanoparticles; the generated petroleum coke stream was crushed and mixed with potassium hydroxide at a mass ratio of 1:1.5, and heated to 900℃ in a nitrogen atmosphere for 2 hours to activate the petroleum coke by one step. The generated product was soaked in a 1mol / L potassium hydroxide aqueous solution to remove the residual nanoparticles, washed with water to neutrality and then dried to obtain petroleum coke-based porous carbon. Weigh 136.1g of sodium acetate trihydrate, dissolve it in 100mL of deionized water, add 303g of ferric nitrate nonahydrate, add 115.1g of ammonium dihydrogen phosphate, and adjust the volume to 600mL to prepare a precursor solution. Weigh 200g of petroleum coke-based porous carbon powder (specific surface area 2516m 2 / g, pore volume 2.11cm3 / g, mesoporous volume ratio is 48%), put it in an oven and dry it at 100℃ for 5 hours. 600mL of precursor solution was added dropwise to the porous carbon powder, and the two were evenly mixed. After 6 hours in a 100℃ forced air oven, it was placed in a tube furnace and calcined at 600℃ for 2 hours under argon atmosphere. The product is marked as PC / NFP-4.

[0063] Example 7

[0064] 50g of nano zinc oxide (particle diameter 20nm) and 50g of nano magnesium oxide (particle diameter 15nm) were fully stirred and mixed with 600g of ethylene tar under nitrogen protection at 250 degrees, and then delayed coking at 500℃ for 24 hours to generate petroleum coke uniformly doped with nanoparticles; the generated petroleum coke stream was crushed to about 200 microns, washed with water to neutrality and then dried, mixed with potassium hydroxide at a mass ratio of 1:3, heated to 800℃ under nitrogen atmosphere and retained for 2 hours, and activated petroleum coke by one step carbonization. The product was first washed with water to remove residual potassium hydroxide, washed in 1mol / L hydrochloric acid solution to remove nano zinc oxide and nano magnesium oxide, and finally washed with water to neutrality, and dried to obtain petroleum coke-based porous carbon. 85g of sodium nitrate was weighed and dissolved in a mixed solution of 100mL of deionized water and 100mL of ethanol, 303g of ferric nitrate nine hydrate was added, 115.0g of ammonium dihydrogen phosphate was added, and finally the volume was adjusted to 500mL with water to prepare a precursor solution. Weigh 150 g of the petroleum coke-based porous carbon powder (specific surface area 2157 m 2 / g, pore volume 2.33cm 3 / g, mesoporous volume accounts for 50%), put it in an oven and dry it at 100°C for 5 hours. Add 500mL of the precursor solution dropwise to the porous carbon powder, mix the two evenly, and dry the mixture in an oven at 100°C for 5 hours. Place the mixture in a tube furnace and bake it at 600°C for 2 hours under an argon atmosphere. The product is marked as PC / NFP-5.

[0065] Comparative Example 1

[0066] 600g of catalytic cracking oil slurry was subjected to delayed coking at 500℃ for 20 hours. The resulting petroleum coke stream was crushed and mixed with potassium hydroxide in a mass ratio of 1:2. It was heated to 900℃ under a nitrogen atmosphere and retained for 2 hours to carbonize and activate the petroleum coke in one step. The resulting product was washed with water until neutral and then dried to obtain petroleum coke-based porous carbon. Weigh 58.4g of sodium chloride, dissolve it in 100mL of deionized water, add 202.5g of ferric chloride hexahydrate, add 115.3g of 85% phosphoric acid, and adjust the volume to 400mL to prepare a precursor solution. Weigh 200g of the petroleum coke-based porous carbon powder obtained above (specific surface area 2036m 2 / g, pore volume 1.13cm3 / g, mesoporous volume ratio 10%), put it in an oven and dry it at 100°C for 6 hours. 400mL of the precursor solution was added dropwise to the above petroleum coke-based porous carbon powder, the two were evenly mixed, and the mixture was dried in an oven at 100°C for 5 hours. The mixture was placed in a tubular furnace and calcined at 600°C for 2 hours under an argon atmosphere. The product is marked as MPC / NFP-1.

[0067] Comparative Example 2

[0068] Weigh 82.0g of anhydrous sodium acetate, dissolve it in 100mL of deionized water, add 80.9g of ferrous oxalate, add 86.5g of 85wt% phosphoric acid, add 50mL of anhydrous ethanol, and finally dilute to 500mL with deionized water to prepare a precursor solution. Weigh 200g of acetylene black powder (specific surface area 10m 2 / g), put it in an oven and dry it at 120°C for 4 hours. Add 500mL of the precursor solution dropwise into the porous carbon powder and mix the two evenly. Take 500mL of 25% concentrated ammonia water and put it in beaker A, put the mixture in beaker B, put the two beakers in a sealed plastic bucket, put the plastic bucket in a 100°C forced air oven for 12 hours, take out beaker B, put it in a 120°C forced air oven for 12 hours, and then put it in a tube furnace and calcine it at 750°C for 2 hours under an argon atmosphere. The product is marked as C / NFP-1.

[0069] Comparative Example 3

[0070] 600g of catalytic oil slurry was subjected to delayed coking at 500℃ for 20 hours. The generated petroleum coke stream was crushed and mixed with potassium hydroxide at a mass ratio of 1:3. It was heated to 900℃ under nitrogen atmosphere and retained for 2 hours to carbonize and activate the petroleum coke in one step. The generated product was washed with water to neutrality and then dried to obtain petroleum coke-based porous carbon. Weigh 200g of petroleum coke-based porous carbon powder (specific surface area 2546m 2 / g, pore volume 1.47cm3 / g, mesoporous volume accounts for 24%), put it in an oven and dry it at 120°C for 12 hours. Weigh 136.1g of sodium acetate trihydrate, dissolve it in 100mL of deionized water, add 303g of ferric nitrate nine hydrate, add 115.1g of ammonium dihydrogen phosphate, and adjust the volume to 600mL to prepare a precursor solution. Add 600mL of precursor solution dropwise to the dried porous carbon powder above and mix the two evenly. Take 500mL of 25wt% concentrated ammonia water and put it in beaker A, put the mixed porous carbon powder in beaker B, put the two beakers in a sealed plastic barrel, put the plastic barrel in a 100°C blast oven for 12 hours, take out beaker B, put it in a 120°C blast oven for 12 hours, and then put it in a tube furnace and roast it at 550°C under an argon atmosphere for 1 hour. The product is marked as MPC / NFP-N-1.

[0071] Comparative Example 4

[0072] 600g of ethylene tar and 200g of nano-silicon dioxide (particle diameter 120nm) were fully stirred and mixed. After delayed coking at 500℃ for 20 hours, petroleum coke with uniformly dispersed silicon dioxide was generated. The generated petroleum coke stream was crushed and mixed with potassium hydroxide at a mass ratio of 1:3. It was heated to 900℃ under a nitrogen atmosphere and retained for 2 hours to carbonize and activate the petroleum coke in one step. The generated product was soaked in a 1mol / L potassium hydroxide aqueous solution to remove residual nanoparticles, washed with water to neutrality and then dried to obtain petroleum coke-based porous carbon. Weigh 200g of petroleum coke-based porous carbon powder (specific surface area 1123m 2 / g, pore volume 1.07cm 3 / g, mesoporous volume accounts for 8%), put it in an oven and dry it at 120°C for 12 hours. Weigh 136.1g of sodium acetate trihydrate, dissolve it in 100mL of deionized water, add 303g of ferric nitrate nonahydrate, add 115.1g of ammonium dihydrogen phosphate, fix the volume to 600mL, and prepare it into a precursor solution. Add 600mL of precursor solution dropwise to the dried porous carbon powder and mix the two evenly. After 6 hours in a 100°C blast oven, put it in a tubular furnace and roast it at 600°C for 2 hours under an argon atmosphere. The product is marked as PC / NFP-4.

[0073] Comparative Example 5

[0074] 600g of catalytic cracking oil slurry and 300g of nano-silicon dioxide (particle diameter 12nm) were fully stirred and mixed, and then delayed coking at 480℃ for 24 hours to generate petroleum coke uniformly doped with nanoparticles; the generated petroleum coke stream was crushed and mixed with potassium hydroxide at a mass ratio of 1:1.5, and heated to 900℃ in an inert atmosphere for 2 hours to activate the petroleum coke by one step of carbonization. The generated product was soaked in a 1mol / L potassium hydroxide aqueous solution to remove the residual nanoparticles, washed with water to neutrality and then dried to obtain petroleum coke-based porous carbon. 134g of sodium oxalate, 113.1g of iron phosphate, 28.8g of diammonium phosphate and 35g of sucrose were weighed and mixed, ball-milled at 500 rpm for 12 hours, and the product was mixed with 200g of petroleum coke-based porous carbon powder (specific surface area 1926m 2 / g, pore volume 1.27cm 3 / g, the mesopore volume ratio is 10%), the mixture is placed in a tube furnace and calcined at 350°C for 5 hours and at 700°C for 2 hours under an argon atmosphere, and the product is marked as PC / NFP-1.

[0075] Evaluation test:

[0076] Electrochemical test method: Mix the product, acetylene black (conductive agent) and polyvinylidene fluoride (binder) in N-methylpyrrolidone at a mass ratio of 8:1:1 to prepare a slurry, stir thoroughly and apply it on aluminum foil, and cut the aluminum foil into 12mm discs. Put the cut discs in the positive electrode shell of the button battery, with the side loaded with the product facing up, and add a polypropylene diaphragm with a diameter of 19mm and a metal sodium disc with a diameter of 15.6mm on the discs in turn, and then put the gasket and spring of the button battery respectively, cover the negative electrode shell and package it into a button battery. The reversible specific capacity of the button battery at current densities of 0.1A / g and 2A / g was tested on the Xinwei battery charge and discharge tester, and the cyclic voltammetry curve was tested on the Swiss Metrohm electrochemical workstation.

[0077] Table 1. Reversible specific capacity of samples at different current densities

[0078]

[0079]

Claims

1. A method for preparing a positive electrode material for a sodium ion capacitor, the method comprising the following steps: S1. Mixing heavy oil with an additive and coking it to obtain a stream A; the additive includes but is not limited to one or more of silicon dioxide, iron oxide, zinc oxide, and magnesium oxide; S2, mixing the material stream A with the activating agent and performing activation treatment, after the activation is completed, washing and drying to obtain material B; S3, uniformly mixing the iron precursor, the sodium precursor, the phosphoric acid source, and the solvent to obtain a precursor solution C; S4. Mix material B with precursor solution C, and obtain the positive electrode material of sodium ion capacitor after drying and calcining the obtained mixed material.

2. The method for preparing the positive electrode material for sodium ion capacitor according to claim 1, wherein: The heavy oil in step S1 is selected from one or more of petroleum asphalt, ethylene tar, catalytic cracking slurry, and vacuum residue.

3. The method for preparing the positive electrode material for sodium ion capacitor according to claim 1, wherein: The auxiliary agent in step S1 is nano-sized particles, and the size of the auxiliary agent is 5 to 50 nm.

4. The method for preparing the positive electrode material for sodium ion capacitor according to claim 1, wherein: The mass ratio of the heavy oil to the auxiliary agent in step S1 is 50:1 to 1:3, preferably 10:1 to 1:

2.

5. The method for preparing the positive electrode material for sodium ion capacitor according to claim 1, wherein: In step S1, the coking temperature of the heavy oil and the auxiliary agent during the coking treatment is 400-600°C, preferably 450-550°C.

6. The method for preparing the positive electrode material for sodium ion capacitor according to claim 1, wherein: In step S2, the activator is one or more of potassium hydroxide, potassium carbonate, potassium bicarbonate, zinc chloride, and phosphoric acid, preferably potassium hydroxide.

7. The method for preparing a positive electrode material for a sodium ion capacitor according to claim 1, wherein: In the activation treatment process in step S2, the ratio between the material flow A and the activating agent is carried out under the condition of a mass ratio of 1:4 to 4:

1.

8. The method for preparing the positive electrode material for sodium ion capacitor according to claim 1, wherein: During the activation treatment in step S2, the temperature at which the material stream A is activated with the activating agent is 700-1000° C., preferably 800-900° C., and the activation is carried out under an inert atmosphere protection condition, and the inert atmosphere is nitrogen and / or an inert gas.

9. The method for preparing a positive electrode material for a sodium ion capacitor according to claim 1, wherein: The washing in step S2 includes two steps. The first step is acid washing or alkali washing to remove residual additives. The selection is made according to the reaction capacity of the additive with acid / or alkali, and the concentration of the acid solution or alkali solution is controlled to be 1-4 mol / L; the second step is water washing until the filtrate is neutral; the washing is carried out at 20-95°C, preferably 50-95°C.

10. The method for preparing a positive electrode material for a sodium ion capacitor according to claim 9, wherein: The base is an inorganic base, which is a NaOH solution; the acid is an inorganic acid solution, which is at least one of a hydrochloric acid solution, a sulfuric acid solution, a hydrobromic acid solution, and a hydrofluoric acid solution.

11. The method for preparing a positive electrode material for a sodium ion capacitor according to claim 1, wherein: The drying temperature in step S2 is 60 to 140° C., and the drying time is 2 to 24 h.

12. The method for preparing a positive electrode material for a sodium ion capacitor according to claim 1, wherein: The pore size distribution of material B in step S2 has the following characteristics: the pore volume occupied by the mesopores is 20% to 70% of the total pore volume of micropores and mesopores, and more preferably 30% to 50%; the pore size of the mesopores is 2 to 50 nm, and the specific surface area is 400 to 3300 m 2 / g, preferably 1000 to 2500 m 2 / g.

13. The method for preparing a positive electrode material for a sodium ion capacitor according to claim 1, wherein: The iron precursor in step S3 is an iron salt, which is an inorganic iron salt and / or an organic iron salt. The iron precursor is selected from one or more of ferric chloride, ferric nitrate, ferric sulfate, ferric oxalate, ferric acetate, ferrous oxalate, ammonium ferrous sulfate, and ferric pyrophosphate, preferably ferric chloride.

14. The method for preparing a positive electrode material for a sodium ion capacitor according to claim 1, wherein: The phosphate source in step S3 is selected from one or more of phosphoric acid, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, ferrous phosphate, ammonium phosphate, diammonium hydrogen phosphate, sodium ammonium hydrogen phosphate, and ammonium dihydrogen phosphate, preferably phosphoric acid.

15. The method for preparing a positive electrode material for a sodium ion capacitor according to claim 1, wherein: The sodium precursor in step S3 is a sodium salt, which is an inorganic sodium salt and / or an organic sodium salt, selected from one or more of sodium chloride, sodium nitrate, sodium nitrite, sodium sulfate, sodium hydroxide, sodium bromide, sodium ethoxide, sodium methoxide, sodium acetate, sodium formate, sodium oxalate, sodium oleate, sodium pyrosulfate, sodium pyrophosphate, and sodium bicarbonate, preferably one or more of sodium chloride, sodium nitrate, and sodium acetate.

16. The method for preparing a positive electrode material for a sodium ion capacitor according to claim 1, wherein: The solvent in step S3 is water and / or an organic solvent, and the organic solvent is one or more of ethanol, acetone, methanol, ethylene glycol, n-propanol, and isopropanol.

17. The method for preparing a positive electrode material for a sodium ion capacitor according to claim 1, wherein: The molar ratio of the iron precursor, the sodium precursor and the phosphate source in step S3 can be determined according to the molecular composition of sodium ferric pyrophosphate Na4Fe3(PO4)2P2O7; the obtained precursor solution C is a sodium ferric pyrophosphate precursor solution.

18. The method for preparing a positive electrode material for a sodium ion capacitor according to claim 1, wherein: In step S4, the mass ratio of material B to precursor solution C is 1:4 to 4:

1.

19. The method for preparing a positive electrode material for a sodium ion capacitor according to claim 1, wherein: The drying conditions in step S4 are as follows: drying temperature is 60 to 150° C., preferably 80 to 120° C.; drying time is 1 to 24 hours, preferably 2 to 12 hours.

20. The method for preparing a positive electrode material for a sodium ion capacitor according to claim 1, wherein: The calcination in step S4 is carried out under an inert atmosphere or a reducing atmosphere, wherein the reducing atmosphere is a mixed gas of hydrogen and an inert atmosphere, and the volume content of hydrogen in the mixed gas is 1 to 50%; the inert atmosphere is nitrogen and / or an inert gas; the calcination conditions are: the calcination temperature is 300 to 1000°C, preferably 500 to 800°C.

21. The method for preparing a positive electrode material for a sodium ion capacitor according to claim 1, wherein: In step S4, material B is mixed with precursor solution C and then heat treated in the presence of an alkaline atmosphere. The material stream obtained after the treatment is further dried and calcined to obtain a positive electrode material; the alkaline atmosphere is at least one of ammonia, ammonium carbonate, ammonium bicarbonate, and ethylenediamine; preferably ammonia; the heat treatment temperature is 50 to 160°C, preferably 60 to 120°C.

22. A positive electrode material for a sodium ion capacitor obtained by the preparation method according to any one of claims 1 to 21.

23. A sodium ion battery, comprising a sodium ion capacitor positive electrode material obtained by the preparation method according to any one of claims 1 to 21.

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