A prussian blue-like nanometer positive electrode material, a preparation method thereof and a sodium ion battery

Abstract

The application belongs to the technical field of battery materials, and particularly relates to a Prussian blue-like nano positive electrode material, a preparation method thereof and a sodium ion battery. x M y [Fe(CN)6] z , wherein M is a transition metal element, and 0

Description

Technical Field

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

[0002] Sodium is abundant (2.75% of the Earth's crust) and evenly distributed. Furthermore, sodium-ion batteries offer the advantage of being compatible with the production equipment and processes of lithium-ion batteries. Therefore, sodium-ion batteries are gradually becoming a focal point of competition in new energy technologies. Cathode materials are a crucial component of sodium-ion batteries, and exploring suitable cathode materials is of great significance for promoting the industrialization of sodium-ion batteries.

[0003] Currently, among cathode materials such as Prussian blue-like materials, layered transition metal oxides, and polyanionic compounds, Prussian blue-like materials are considered the most promising for industrialization due to their unique three-dimensional framework structure, which facilitates the reversible insertion and extraction of sodium ions, and their low cost. Traditional aqueous co-precipitation methods can yield large quantities of Prussian blue-like materials at room temperature; however, the particle size of these materials is concentrated in the micrometer or submicrometer range (Reference: Advanced Functional Materials, 2022, 32, 2108616). Solid-state synthesis methods can obtain nano-sized Prussian blue-like materials, but the material uniformity is poor (Reference: Chemical Engineering Journal, 2022, 428, 131083). Template methods are a commonly used approach for preparing nanomaterials. Patent application number 201610307227.X discloses a method for constructing substrate-free, interconnected two-dimensional Prussian blue-like compound nanosheets using hydrotalcite (also known as layered double hydroxides) as a template. The method involves selecting intercalable hydrotalcite as a template, intercalating ferrocyanide ions, adding trivalent metal ions in situ to coordinate between the layers to construct Prussian blue-like compounds, and finally dissolving the hydrotalcite layers with an inorganic acid to obtain substrate-free, interconnected two-dimensional Prussian blue-like compound nanosheets. The resulting two-dimensional Prussian blue-like compound nanosheets exhibit uniform primary particle size and a concentrated nanoscale distribution, resulting in a large specific surface area. However, this method is only applicable to the preparation of Fe... 3+ 4[Fe 2+ [CN]6]3 and Cr 3+ 4[Fe 2+ (CN)6]3; at the same time [Fe 2+ (CN)6] 4- Due to the large ion size, during the preparation process, it interacts with the anions (Cl-) in the template. - Or NO3 - The low efficiency during the exchange process resulted in a low yield of Prussian blue-like products.

[0004] The common drawbacks of existing Prussian blue-like materials are as follows: Prussian blue-like materials obtained by traditional aqueous coprecipitation methods have particle sizes concentrated in the micrometer or submicrometer range, resulting in a small specific surface area; nano-Prussian blue-like materials obtained by solid-phase synthesis methods exhibit poor uniformity; and the template method based on layered hydrotalcite templates is only used for preparing trivalent transition metal elements (Fe). 3+ or Cr 3+ Ferrocyanate, but with low yield.

[0005] Furthermore, when Prussian blue-like materials prepared using existing methods are used as cathode materials in sodium-ion batteries, they suffer from drawbacks such as low sodium ion diffusion rate, poor sodium storage capacity, and poor rate performance.

[0006] Therefore, there is an urgent need to provide a new method for preparing Prussian blue-like nano-cathode materials. These materials have a large specific surface area, a high sodium ion diffusion rate, and are universally applicable to transition metal elements. The resulting products have good uniformity, thereby improving sodium storage capacity and rate performance. Summary of the Invention

[0007] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention proposes a Prussian blue-like nano-cathode material, its preparation method, and a sodium-ion battery.

[0008] The inventive concept of this invention is as follows: This invention employs a spatially confined growth method, using ordinary layered bimetallic hydroxides as templates. Based on their unique structural memory effect, the calcined layered transition metal oxides are immersed in a substrate containing [Fe...] 2+ (CN)6] 4- In an aqueous solution, a layered bimetallic hydroxide with ferrocyanide anion intercalation is obtained. This hydroxide then reacts with added transition metal ions in a confined interlayer reaction. Further acid treatment to remove the layered bimetallic hydroxide template yields a Prussian blue-like nano-cathode material. The preparation method described in this invention achieves nanoscale control of the Prussian blue-like nano-cathode material, increasing its specific surface area and sodium ion diffusion rate, thereby improving its sodium storage capacity and rate performance. 2+ (CN)6] 4- Competition with anions in layered bimetallic hydroxide templates improves yield; at the same time, it has strong universality for transition metal ions and the resulting products have good uniformity.

[0009] The first aspect of the present invention provides a Prussian blue-like nano cathode material.

[0010] Specifically, a Prussian blue-like nano-cathode material with the general chemical formula Na x M y [Fe(CN)6] z, where M is a transition metal element, and 0 < x < 2, 0 < y < 1, 0 < z < 1; the Prussian blue-like nano cathode material is granular, and the particle size of the Prussian blue-like nano cathode material is less than 60 nm.

[0011] The Prussian blue-like nano cathode material of the present invention has universality for transition metal elements, a particle size less than 60 nm, a large specific surface area, and a high sodium ion diffusion rate. When the Prussian blue-like nano cathode material is applied in a sodium ion battery, the sodium ion diffusion rate is high, improving the sodium storage capacity and rate performance. Moreover, the preparation method of the material has a high yield, which is beneficial to the large-scale industrial production of the Prussian blue-like nano cathode material of the present invention.

[0012] Further preferably, the particle size of the Prussian blue-like nano cathode material is less than 50 nm. Specifically, for example, less than 40 nm, less than 30 nm, less than 20 nm.

[0013] Preferably, M is selected from at least one of Fe, Co, Ni, Mn, Cu, and Zn.

[0014] Preferably, the valence of M is +2 or +3; further preferably, the valence of M is +2.

[0015] Preferably, the Prussian blue-like nano cathode material is selected from sodium ferrocyanoferrate (Na x Fe y [Fe(CN)6] z ), sodium cobaltocyanide (Na x Co y [Fe(CN)6] z ), sodium nickelocyanide (Na x Ni y [Fe(CN)6] z ), sodium manganocyanide (Na x Mn y [Fe(CN)6] z ), sodium copper cyanide (Na x Cu y [Fe(CN)6] z ), or sodium zincocyanide (Na x Zn y [Fe(CN)6] z ).

[0016] The second aspect of the present invention provides a preparation method of a Prussian blue-like nano cathode material.

[0017] Specifically, a preparation method of a Prussian blue-like nano cathode material includes the following steps:

[0018] (1) The layered bimetallic hydroxide template was calcined and then placed in a solution containing ferrocyanide ions and stirred to obtain a layered bimetallic hydroxide with ferrocyanide ion intercalation.

[0019] (2) The layered bimetallic hydroxide intercalated with ferrocyanide ions is mixed and dispersed with a solvent, then a transition metal salt is added, stirred, and centrifuged to obtain a precipitate. The precipitate is then mixed with an inorganic acid solution, stirred, and centrifuged to obtain the Prussian blue-like nano cathode material.

[0020] Preferably, in step (1), the preparation process of the layered bimetallic hydroxide template is as follows: an alkaline solution is added to an aqueous solution of metal salts containing divalent and trivalent metal salts, wherein the molar ratio of the alkali in the alkaline solution to the total molar amount of divalent and trivalent metal salts is 12-28:1, and the molar ratio of divalent and trivalent metal salts is 1-3:1; the reaction is carried out by heating, centrifugation, washing, and drying to obtain the layered bimetallic hydroxide template.

[0021] More preferably, in step (1), the preparation process of the layered bimetallic hydroxide template is as follows: first, prepare 1.0–2.0 mol·L⁻¹ -1 Prepare a NaOH aqueous solution containing 0.1–0.3 mol·L⁻¹. -1 Divalent metal salts and 0.1–0.3 mol·L⁻¹ -1 Aqueous solutions of trivalent metal salts are prepared by rapidly adding the prepared NaOH aqueous solution to the metal salt aqueous solution and stirring for 20–40 min. Then, deionized water is added and stirring is continued for another 20–40 min. The resulting mixture is transferred to a high-pressure reactor, tightened, and placed in a high-temperature oven at 90–150 °C for 8–16 h. After the reaction is complete, the oven and high-pressure reactor are cooled to room temperature and then opened. The mixture in the high-pressure reactor is then centrifuged at 7000–8000 rpm for 5–10 min, washed with deionized water, and repeated 3–5 times. Finally, it is dried in a vacuum oven at 60–80 °C for 8–12 h to obtain a layered bimetallic hydroxide template.

[0022] More preferably, the molar ratio of the total molar amount of NaOH to the divalent and trivalent metal salts is 15–25:1.

[0023] The volume of deionized water added again is the same as the total volume of the NaOH aqueous solution and the metal salt aqueous solution.

[0024] Preferably, the temperature of the heating reaction is 100–140°C.

[0025] Preferably, during the reaction, the pressure in the high-pressure reactor is 0.08–3.1 MPa; more preferably, during the reaction, the pressure in the high-pressure reactor is 0.1–2.8 MPa.

[0026] Preferably, in the preparation process of the layered bimetallic hydroxide template, the divalent metal salt is selected from magnesium nitrate (Mg(NO3)2), magnesium chloride (MgCl2), magnesium sulfate (MgSO4), magnesium acetate (Mg(CH3COO)2), zinc nitrate (Zn(NO3)2), zinc chloride (ZnCl2), zinc sulfate (ZnSO4), zinc acetate (Zn(CH3COO)2), nickel nitrate (Ni(NO3)2), nickel chloride (NiCl2), nickel sulfate (NiSO4), nickel acetate (Ni(CH3COO)2), and cobalt nitrate (Co(NO3)2). Cobalt chloride (CoCl2), cobalt sulfate (CoSO4), cobalt acetate (Co(CH3COO)2), calcium nitrate (Ca(NO3)2), calcium chloride (CaCl2), calcium acetate (Ca(CH3COO)2), ferrous nitrate (Fe(NO3)2), ferrous chloride (FeCl2), ferrous sulfate (FeSO4), ferrous acetate (Fe(CH3COO)2), copper nitrate (Cu(NO3)2), copper chloride (CuCl2), copper sulfate (CuSO4), copper acetate (Cu(CH3COO)2), and one or more of their hydrates.

[0027] Preferably, in the preparation of the layered bimetallic hydroxide template, the trivalent metal salt is selected from one or more of aluminum nitrate (Al(NO3)3), aluminum chloride (AlCl3), aluminum sulfate (Al2(SO4)3), ferric nitrate (Fe(NO3)3), ferric chloride (FeCl3), ferric sulfate (Fe2(SO4)3), chromium nitrate (Cr(NO3)3), chromium chloride (CrCl3), chromium sulfate (Cr2(SO4)3), gallium nitrate (Ga(NO3)3), gallium chloride (GaCl3), gallium sulfate (Ga2(SO4)3), and their hydrates.

[0028] More preferably, in the preparation process of the layered bimetallic hydroxide template, the trivalent metal salt is aluminum nitrate nonahydrate or aluminum nitrate.

[0029] Preferably, in step (1), the calcination temperature is 300-500°C; more preferably, the calcination temperature is 350-500°C.

[0030] Preferably, in step (1), the calcination time is 2.5 to 6 hours; more preferably, the calcination temperature is 3 to 6 hours.

[0031] Preferably, in step (1), the calcination is carried out in an inert gas atmosphere.

[0032] Preferably, in step (1), the solution containing ferrocyanide ions includes a sodium ferrocyanide solution.

[0033] Preferably, in step (1), the concentration of the solution containing ferrocyanide ions is 0.5–6 mg·mL. -1 More preferably, the concentration of the solution containing ferrocyanide ions is 1–4 mg·mL. -1 .

[0034] Preferably, in step (1), the stirring time is 12 to 30 hours, and more preferably, the stirring time is 18 to 30 hours.

[0035] Preferably, in step (1), after stirring, the process further includes centrifugation, washing, and drying.

[0036] Preferably, the centrifugation is performed at a speed of 6000-8000 rpm for 5-10 minutes.

[0037] Preferably, the washing is done with deionized water, and the washing process is repeated 1 to 5 times.

[0038] Preferably, the drying temperature is 60-80°C and the drying time is 10-12 hours.

[0039] Preferably, in step (1), after calcination, the mass ratio of the layered bimetallic hydroxide template to sodium ferrocyanide is 1:(1-12); more preferably, after calcination, the mass ratio of the layered bimetallic hydroxide template to sodium ferrocyanide is 1:(2-10).

[0040] Preferably, in step (2), the solvent is deionized water.

[0041] Preferably, in step (2), the mixing and dispersion is performed by ultrasonic dispersion, and after mixing and dispersion, a suspension is formed.

[0042] Preferably, in step (2), the concentration of the suspension formed after mixing and dispersion is 0.5–2.5 mg·mL. -1 Further preferred, 0.5–2 mg / mL -1 .

[0043] Preferably, in step (2), the transition metal salt is selected from ferrous chloride (FeCl2), ferrous nitrate (Fe(NO3)2), ferrous sulfate (FeSO4), ferric acetate (Fe(CH3COO)2), cobalt chloride (CoCl2), cobalt nitrate (Co(NO3)2), cobalt sulfate (CoSO4), cobalt acetate (Co(CH3COO)2), nickel chloride (NiCl2), nickel nitrate (Ni(NO3)2), nickel sulfate (NiSO4), and nickel acetate (Ni(CH3COO)2). 2) One or more of the following: manganese chloride (MnCl2), manganese nitrate (Mn(NO3)2), manganese sulfate (MnSO4), manganese acetate (Mn(CH3COO)2), copper chloride (CuCl2), copper nitrate (Cu(NO3)2), copper sulfate (CuSO4), copper acetate (Cu(CH3COO)2), zinc chloride (ZnCl2), zinc nitrate (Zn(NO3)2), zinc sulfate (ZnSO4), zinc acetate (Zn(CH3COO)2), and their possible hydrates.

[0044] Preferably, in step (2), the stirring time is 0.5 to 3.5 hours, more preferably 1 to 3 hours.

[0045] Preferably, in step (2), after the stirring is completed, the mixture is allowed to stand for 20 to 24 hours and then centrifuged.

[0046] Preferably, in step (2), the centrifugation is performed at a speed of 6000-8000 rpm for 5-10 minutes.

[0047] Preferably, in step (2), after centrifugation, the product is washed with deionized water, and the washing process is repeated 1 to 5 times.

[0048] Preferably, in step (2), the inorganic acid solution is selected from one or more of hydrochloric acid, nitric acid solution, and sulfuric acid solution. Preferably, the inorganic acid is hydrochloric acid.

[0049] Preferably, in step (2), the drying temperature is 60-80°C and the drying time is 10-12 hours.

[0050] Preferably, in step (2), the mass ratio of the ferrocyanide ion-intercalated layered bimetallic hydroxide to the transition metal salt is 1:(3-12); more preferably, the mass ratio of the ferrocyanide ion-intercalated layered bimetallic hydroxide to the transition metal salt is 1:(5-10).

[0051] Preferably, in step (2), the mass ratio of the inorganic acid in the inorganic acid solution to the layered bimetallic hydroxide intercalated with ferrocyanide ions is 2 to 8:1, and more preferably, the mass ratio is 4 to 5:1.

[0052] A third aspect of the present invention provides an application of a Prussian blue-like nano cathode material.

[0053] Specifically, a sodium-ion battery includes: a negative electrode, an electrolyte, a separator, and a positive electrode; the positive electrode includes a positive electrode active material and a positive electrode current collector, and the positive electrode active material includes a Prussian blue-like nano-positive electrode material.

[0054] Preferably, the negative electrode includes a negative electrode active material and a negative electrode current collector.

[0055] Preferably, the negative electrode current collector is selected from aluminum, copper, titanium, stainless steel, and nickel foil.

[0056] More preferably, the negative electrode current collector is copper foil.

[0057] Preferably, the negative electrode active material is selected from one or more of the following: carbon-based materials such as hard carbon, soft carbon, graphene, and carbon nanotubes; alloying and conversion materials such as tin, phosphorus, metal oxides, metal chalcogenides, and metal phosphides; NASICON-type materials such as sodium titanium phosphate; and transition metal carbon / nitrides.

[0058] Preferably, the negative electrode further includes a conductive agent and a binder.

[0059] Preferably, the electrolyte comprises a sodium salt electrolyte and an organic solvent.

[0060] Preferably, the sodium salt electrolyte is selected from one or more of the following: sodium trifluoromethanesulfonate (NaCF3SO3), sodium bis(trifluoromethanesulfonyl)imide [NaN(CF3SO2)2] and its derivatives, sodium perfluoroalkyl phosphate [NaPF3(C2F5)3], sodium tetrafluorooxalate phosphate [NaPF4(C2O4)], sodium bis(oxalate borate) [NaB(C2O4)2], sodium tri(catechol) phosphate (NTBP), sodium sulfonated polysulfonamide, sodium hexafluorophosphate (NaPF6), sodium perchlorate (NaClO4), sodium tetrafluoroborate (NaBF4), sodium hexafluoroarsenate (NaAsF6), sodium nitrate (NaNO3), sodium carbonate (Na2CO3), and sodium chloride (NaCl).

[0061] More preferably, the sodium electrolyte salt is sodium hexafluorophosphate (NaPF6) with a concentration range of 0.1–10 mol·L⁻¹. -1 (Preferred concentration: 0.8–1.0 mol·L⁻¹) -1 ).

[0062] Preferably, the organic solvent in the electrolyte is selected from propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl formate (MF), methyl acetate (MA), N,N-dimethylacetamide (DMA), fluoroethylene carbonate (FEC), methyl propionate (MP), ethyl propionate (EP), ethyl acetate (EA), γ-butyrolactone (GBL), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2MeTHF), 1,3-dioxolane (DOL), 4-methyl-1,3-dioxolane (4MeDOL), dimethoxymethane (DMM), 1,2-dimethoxypropane (DMP), triethylene glycol dimethyl ether (TEGDME), dimethyl sulfone (MSM), diethylene glycol dimethyl ether (DME), vinyl sulfite (ES), propylene sulfite (PS), dimethyl sulfite (DMS), and diethyl sulfite (DES). Crown ether (12-crown-4), 1-ethyl-3-methylimidazolium-hexafluorophosphate, 1-ethyl-3-methylimidazolium-tetrafluoroborate, 1-ethyl-3-methylimidazolium-bis(trifluoromethanesulfonyl)imide, 1-propyl-3-methylimidazolium-hexafluorophosphate, 1-propyl-3-methylimidazolium-tetrafluoroborate, 1-propyl-3-methylimidazolium-bis(trifluoromethanesulfonyl)imide, 1-butyl-1-methylimidazolium-hexafluorophosphate, 1-butyl-1-methylimidazolium-tetrafluoroboric acid One or more of the following organic solvents: salts, 1-butyl-1-methylimidazolium-bis(trifluoromethanesulfonyl)imide salt, N-butyl-N-methylpyrrolidine-bis(trifluoromethanesulfonyl)imide salt, 1-butyl-1-methylpyrrolidine-bis(trifluoromethanesulfonyl)imide salt, N-methyl-N-propylpyrrolidine-bis(trifluoromethanesulfonyl)imide salt, N-methyl,propylpiperidine-bis(trifluoromethanesulfonyl)imide salt, and N-methyl,butylpiperidine-bis(trifluoromethanesulfonyl)imide salt, which are esters, sulfones, ethers, nitriles, or ionic liquids.

[0063] More preferably, the organic solvent in the electrolyte is a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in equal volumes.

[0064] Preferably, the diaphragm is selected from one or more of insulating porous polymer films or inorganic porous films.

[0065] More preferably, the separator is selected from one or more of porous polypropylene film, porous polyethylene film, porous composite polymer film, glass fiber paper, and porous ceramic separator. Preferably, the separator is glass fiber paper.

[0066] Preferably, the positive electrode current collector is selected from one of aluminum foil, carbon-coated aluminum foil, iron foil, tin foil, zinc foil, nickel foil, titanium foil, and manganese foil. Preferably, the positive electrode current collector is carbon-coated aluminum foil.

[0067] Preferably, the positive electrode further includes a conductive agent and a binder.

[0068] A method for preparing a sodium-ion battery includes the following steps:

[0069] The positive electrode active material is prepared into a slurry and then coated on the surface of the positive electrode current collector to form a positive electrode active layer, thereby obtaining the positive electrode;

[0070] The sodium-ion battery is prepared by assembling the positive electrode, negative electrode, electrolyte, and separator.

[0071] Preferably, the method for preparing the sodium-ion battery further includes the following steps:

[0072] Preparation of negative electrode: The negative electrode active material is prepared into a slurry and then coated on the surface of the negative electrode current collector to form a negative electrode active layer, thereby obtaining the negative electrode;

[0073] Preparation of electrolyte: The sodium salt electrolyte and organic solvent are mixed and stirred to obtain the electrolyte;

[0074] Prepare the diaphragm: Cut the diaphragm to the required size and set aside.

[0075] Preferably, a method for preparing a sodium-ion battery includes the following steps:

[0076] Preparation of negative electrode: Take negative electrode active material, conductive agent and binder, add them to solvent and mix them thoroughly to form a uniform slurry. Clean the negative electrode current collector, and then uniformly coat the slurry on the surface of the negative electrode current collector. After the slurry is completely dry, cut it to obtain the battery negative electrode of the required size.

[0077] Preparation of electrolyte: Add sodium salt electrolyte to organic solvent and stir thoroughly to dissolve to obtain electrolyte;

[0078] Preparation of the diaphragm: Cut the diaphragm to the required size and clean it thoroughly;

[0079] Preparation of positive electrode: Take positive electrode active material, conductive agent and binder, add them to solvent and mix thoroughly to form a uniform slurry. Clean the positive electrode current collector, then coat the slurry evenly on the surface of the positive electrode current collector. After drying, cut to obtain the positive electrode of the required size.

[0080] The sodium-ion battery is obtained by assembling the negative electrode, electrolyte, separator, and positive electrode.

[0081] An electrical product comprising the sodium-ion battery.

[0082] Preferably, the electrical products include mobile phones, computers, and electric vehicles.

[0083] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0084] (1) The Prussian blue-like nano-cathode material of the present invention has a particle size of less than 60 nm, a large specific surface area, and a high sodium ion diffusion rate. When applied in sodium-ion batteries, the high sodium ion diffusion rate of the Prussian blue-like nano-cathode material improves sodium storage capacity and rate performance. Furthermore, the preparation method of the material has a high yield (or high raw material conversion rate), which is beneficial for the large-scale industrial production of the Prussian blue-like nano-cathode material of the present invention.

[0085] (2) This invention employs a spatially confined growth method, using ordinary layered bimetallic hydroxides as templates. Based on their unique structural memory effect, the heat-treated layered transition metal oxides are immersed in a substrate containing [Fe]. 2+ (CN)6] 4- In an aqueous solution, a layered bimetallic hydroxide intercalated with ferrocyanide anions is obtained. This hydroxide then reacts with added transition metal ions in a confined space within the layers. Further acid treatment removes the layered bimetallic hydroxide template, yielding a Prussian blue-like nano-cathode material. This invention utilizes the unique structural memory effect and confined space within the layers of layered bimetallic hydroxides to synthesize Prussian blue-like nano-cathode materials. The preparation method described in this invention achieves nanoscale control of the Prussian blue-like nano-cathode material, increasing its specific surface area and sodium ion diffusion rate, thereby improving its sodium storage capacity and rate performance. The preparation method described in this invention eliminates the [Fe]... 2+ (CN)6] 4- Competition with anions in layered bimetallic hydroxide templates improves yield; at the same time, it has strong universality and the resulting products have good uniformity. Attached Figure Description

[0086] Figure 1 The Prussian blue-like Na prepared in Example 1 of this invention x Ni y [Fe(CN)6] z Scanning electron microscope image of nano-cathode material;

[0087] Figure 2 The Prussian blue-like Na prepared in Example 1 of this invention x Ni y [Fe(CN)6] z The nano-cathode material and the cathode material prepared in Comparative Example 1 were tested at 50 mA·g. -1 Long-cycle performance curves;

[0088] Figure 3 The Prussian blue-like Na prepared in Example 1 of this invention x Ni y[Fe(CN)6] z Rate performance of nano-cathode materials and the cathode material prepared in Comparative Example 1 at different current densities. Detailed Implementation

[0089] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0090] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0091] Example 1: Prussian Blue-like Na x Ni y [Fe(CN)6] z Preparation of nano cathode materials

[0092] In this embodiment, magnesium nitrate hexahydrate is used as a divalent metal salt, aluminum nitrate nonahydrate is used as a trivalent metal salt, and nickel nitrate hexahydrate is used as a transition metal salt for preparing Prussian blue-like substances.

[0093] A type of Prussian blue Na x Ni y [Fe(CN)6] z The preparation method of nano-cathode materials is as follows:

[0094] Step 1: First, prepare 24 mL of 1.5 mol·L⁻¹ solution. -1 Prepare 6 mL of a NaOH aqueous solution containing 0.2 mol·L⁻¹ NaOH. -1 Magnesium nitrate hexahydrate and 0.1 mol·L -1 Aqueous solution of aluminum nitrate nonahydrate metal salt; quickly add the prepared NaOH aqueous solution to the metal salt aqueous solution, stir for 30 min, then add 30 mL of deionized water, and continue stirring for 30 min; transfer the stirred mixture to a 100 mL high-pressure reactor, tighten it, and place it in a high-temperature oven at 120 °C for 12 h. After the reaction is complete, cool the oven and reactor to room temperature and open it. Centrifuge the mixture in the high-pressure reactor at 8000 rpm for 5 min, then wash with deionized water. Repeat the washing three times. Place the resulting solid material in an 80 °C vacuum oven and dry for 12 h to obtain a magnesium-aluminum layered bimetallic hydroxide template.

[0095] Step two: The magnesium-aluminum layered bimetallic hydroxide template synthesized in step one was placed in a magnetic boat and transferred to a tube furnace, where it was calcined at 400°C for 4 hours in an inert gas (argon) atmosphere; the calcined magnesium-aluminum layered bimetallic hydroxide template was then placed in 50 mL of a 2 mg / mL solution. -1In a sodium ferrocyanide solution, after stirring for 24 hours, the mixture was centrifuged at 8000 rpm for 5 minutes, then washed with deionized water. The resulting solid was washed three times and then dried in a vacuum oven at 80°C for 12 hours to obtain a magnesium-aluminum layered bimetallic hydroxide with ferrocyanide ion intercalation.

[0096] Step 3: The ferrocyanide ion-intercalated magnesium-aluminum layered bimetallic hydroxide obtained in Step 2 is ultrasonically dispersed in deionized water to prepare a solution of 1 mg·mL⁻¹. -1 The suspension was mixed with 300 mg of nickel nitrate hexahydrate, stirred for 2 hours, and then allowed to stand for 24 hours. The mixture was then centrifuged at 8000 rpm for 5 minutes, washed with deionized water, and the resulting precipitate was washed three times. The precipitate was then added to 100 mL of 1 mol·L⁻¹ hydrochloric acid solution. -1 In hydrochloric acid, the mixture was stirred for 2 hours and then allowed to stand for 24 hours to age. The resulting product was centrifuged at 8000 rpm for 5 minutes, then washed with deionized water. The precipitate was washed three times and then dried in a vacuum oven at 80℃ for 12 hours to obtain Prussian blue-like Na with a particle size of approximately 20 nm. x Ni y [Fe(CN)6] z Nanomaterials for cathodes.

[0097] Example 1 of this invention: Preparation of Prussian Blue-like Na x Ni y [Fe(CN)6] z In the process of producing nano-cathode materials, 480 mg of the magnesium-aluminum layered bimetallic hydroxide template in step one can ultimately yield approximately 120 mg of the Prussian blue-like Na in step three. x Ni y [Fe(CN)6] z Nanomaterials for cathodes.

[0098] Figure 1 The Prussian blue-like Na prepared in Example 1 of this invention x Ni y [Fe(CN)6] z Scanning electron microscope image of nano-cathode material; from Figure 1 As can be seen from the above, the Prussian blue-like Na prepared in Example 1 of this invention... x Ni y [Fe(CN)6] z The particle size of the nano cathode material is approximately 20 nm.

[0099] The Prussian blue-like Na prepared in Example 1 x Ni y [Fe(CN)6] zNanomaterials are used as positive electrode active materials in sodium-ion batteries, with sodium sheets as the counter electrode, at a concentration of 0.8 mol·L⁻¹. -1 NaPF6 / EC-DEC (1:1, v / v) was used as the electrolyte to assemble half-cells, and electrochemical performance was tested.

[0100] Comparative Example 1: Na x Ni y [Fe(CN)6] z Preparation of cathode materials

[0101] In this comparative example, pure-phase Na was prepared using the traditional co-precipitation method. x Ni y [Fe(CN)6] z The specific preparation process of the cathode material is as follows:

[0102] Step 1: Add 1.5484g of trisodium citrate dihydrate and 1.5mmol of nickel nitrate hexahydrate to 50mL of deionized water and stir (referred to as solution A). Dissolve 1.5mmol of sodium ferrocyanide decahydrate in 50mL of deionized water and stir (referred to as solution B).

[0103] Step 2: Under continuous vigorous stirring, add the prepared solution A dropwise to solution B. After the addition is complete, continue stirring for another 30 minutes. After stirring, age the solution at room temperature for 12 hours. Pour the aged mixture into a centrifuge tube and centrifuge at 8000 rpm for 5 minutes. Then wash with deionized water. Repeat the washing process three times with the precipitate. Finally, place the precipitate in a 1 mol·L⁻¹ solution. -1 In hydrochloric acid, stir for 2 hours and then let stand for 24 hours to age. Centrifuge the obtained product at 8000 rpm for 5 minutes, then wash with deionized water. Repeat the washing three times, and then dry in a vacuum oven at 80℃ for 12 hours to obtain pure phase Na. x Ni y [Fe(CN)6] z The cathode material has a particle size of 300–500 nm.

[0104] Pure phase Na prepared according to Comparative Example 1 x Ni y [Fe(CN)6] z The positive electrode material is used as the positive electrode active material in sodium-ion batteries, with a sodium sheet as the counter electrode, and a concentration of 0.8 mol·L⁻¹. -1 NaPF6 / EC-DEC (1:1, v / v) was used as the electrolyte to assemble half-cells, and electrochemical performance was tested.

[0105] Figure 2 The Prussian blue-like Na prepared in Example 1 of this invention x Ni y[Fe(CN)6] z The nano-cathode material and the cathode material prepared in Comparative Example 1 were tested at 50 mA·g. -1 The following is a long-cycle performance curve.

[0106] Figure 3 The Prussian blue-like Na prepared in Example 1 of this invention x Ni y [Fe(CN)6] z Rate performance of nano-cathode materials and the cathode material prepared in Comparative Example 1 at different current densities.

[0107] from Figure 2 and Figure 3 It can be seen that at 50mA·g -1 Cycling at a current density of 1500 cycles, the Prussian blue-like Na prepared in Example 1 of this invention... x Ni y [Fe(CN)6] z The specific capacity of the nano-cathode material can still be maintained at 64.5 mAh·g. -1 Around 99%, the coulombic efficiency is 99%, demonstrating good cycle performance; at high rates of 1 A·g -1 The specific capacity remains at 35.6 mAh·g. -1 It exhibits good rate capability.

[0108] from Figure 2 and Figure 3 It can be seen that at 50mA·g -1 After cycling at a current density of 1500 times, the specific capacity of the cathode material prepared in Comparative Example 1 was only 51.5 mAh·g. -1 The coulomb efficiency is approximately 93.2%; at high magnification (1 A·g), the efficiency is 1%. -1 The specific capacity is 19.8 mAh·g. -1 about.

[0109] Examples 2-3: Preparation of Na from magnesium-aluminum layered bimetallic hydroxides synthesized based on different concentration ratios x Ni y [Fe(CN)6] z Nano cathode materials

[0110] Na in Examples 2-3 and Example 1 x Ni y [Fe(CN)6] z The preparation process of the nano cathode material is the same, except that the concentration ratio of magnesium nitrate hexahydrate and aluminum nitrate nonahydrate used in step one is different. The half-cell electrochemical performance of the nano cathode materials of Examples 2-3 was tested and compared with that of Example 1. The test results are shown in Table 1.

[0111] Table 1: Half-cell test data of nano-cathode materials in Examples 2-3 of the present invention

[0112]

[0113] Examples 4-7: Na prepared based on different hydrothermal reaction temperatures x Ni y [Fe(CN)6] z Nano cathode materials

[0114] Na in Examples 4-7 and Example 1 x Ni y [Fe(CN)6] z The preparation process of the nano cathode material is the same, except that the reaction temperature used in step one is different. The half-cell electrochemical performance of the nano cathode materials in Examples 4-7 was tested and compared with that in Example 1. The test results are shown in Table 2.

[0115] Table 2: Half-cell test data of nano-cathode materials in Examples 4-7 of the present invention

[0116]

[0117] Examples 8-9: Na prepared based on different hydrothermal reaction times x Ni y [Fe(CN)6] z Nano cathode materials

[0118] Na in Examples 8-9 and Example 1 x Ni y [Fe(CN)6] z The preparation process of the nano cathode material is the same, except that the hydrothermal reaction time used in step one is different. The half-cell electrochemical performance of the nano cathode materials in Examples 8-9 was tested and compared with that in Example 1. The test results are shown in Table 3.

[0119] Table 3: Half-cell test data of nano-cathode materials in Examples 8-9 of the present invention

[0120]

[0121] Examples 10-12: Na prepared at different calcination temperatures x Ni y [Fe(CN)6] z Nano cathode materials

[0122] Na in Examples 10-12 and Example 1 x Niy [Fe(CN)6] z The preparation process of the nano cathode material is the same, except that the calcination temperature used in step two is different. The half-cell electrochemical performance of the nano cathode materials in Examples 10-12 was tested and compared with that in Example 1. The test results are shown in Table 4.

[0123] Table 4: Half-cell test data of the cathode material in Examples 10-12 of the present invention

[0124]

[0125] Examples 13-25: Based on Na x Ni y [Fe(CN)6] z Half-cells assembled with nano-cathode materials in different electrolytes

[0126] Examples 13-25 use the same Na as in Example 1. x Ni y [Fe(CN)6] z The nano-cathode materials differ only in that they are assembled into sodium-ion half-cells using different electrolytes. The half-cell electrochemical performance of the nano-cathode materials in Examples 13-25 was tested and compared with that in Example 1. The test results are shown in Table 5.

[0127] Table 5: Half-cell test data of Examples 13-25 of the present invention

[0128]

[0129]

[0130] Examples 26-186: Preparation of Na based on different divalent metal salts and different transition metal salts in layered bimetallic hydroxides x M y [Fe(CN)6] z Nano cathode materials

[0131] Na in Examples 26-186 and Example 1 x Ni y [Fe(CN)6] z The preparation process of the nano cathode material is the same, the only difference being the divalent metal salt in the layered bimetallic hydroxide in step one and the transition metal salt in step three. The half-cell electrochemical performance of the nano cathode materials in Examples 26-186 was tested and compared with that in Example 1. The test results are shown in Table 6.

[0132] Table 6. Half-cell test data of nano-cathode materials in Examples 26-186 of the present invention

[0133]

[0134]

[0135]

[0136]

[0137]

[0138]

[0139]

[0140]

[0141]

[0142]

[0143]

[0144]

[0145] Comparative Example 2: Na prepared based on Comparative Example 1 x Ni y [Fe(CN)6] z Full cells with cathode materials

[0146] Na prepared using Comparative Example 1 of the present invention x Ni y [Fe(CN)6] z A sodium-ion full battery is constructed using a positive electrode material as the positive electrode active material, while the negative electrode active material is hard carbon. The specific preparation steps of the sodium-ion full battery are as follows:

[0147] Positive electrode preparation: Take positive electrode active material, conductive carbon black and polyvinylidene fluoride (PVDF) and mix them evenly in a mass ratio of 8:1:1. Add them to N-methylpyrrolidone (NMP) solvent and mix them thoroughly to form a uniform slurry. Clean the carbon-coated aluminum foil of the positive electrode current collector. Then coat the surface of the positive electrode current collector evenly with the slurry. After drying at 80℃ for 48h, cut it to obtain the positive electrode of the required size.

[0148] Electrolyte preparation: at 0.8 mol·L⁻¹ -1 NaPF6 / EC-DEC (1:1, v / v) is the electrolyte;

[0149] Negative electrode preparation: Hard carbon, conductive carbon black and polyvinylidene fluoride (PVDF) are mixed evenly in a mass ratio of 8:1:1. Then, N-methylpyrrolidone (NMP) solvent is added and stirred thoroughly to obtain a slurry. The slurry is then evenly coated on the surface of copper foil and placed in a vacuum oven for drying at 80°C for 48 hours. The foil is then cut to obtain the negative electrode of the required size.

[0150] Full cell assembly: Assemble the negative electrode, electrolyte, separator (glass fiber paper) and positive electrode to obtain a sodium-ion full cell.

[0151] The sodium-ion full cell prepared in Comparative Example 2 operates at 1C (1C = 100 mA·g). -1 Under a charge-discharge rate of ), after 200 cycles, the capacity retention rate was only 54.7%.

[0152] Comparative Examples 3-16: Na based on Comparative Example 1 x Ni y [Fe(CN)6] z Sodium-ion full cells assembled with positive electrode materials and different negative electrode active materials

[0153] Comparative Example 3-16 and Comparative Example 2 share the same sodium-ion full cell preparation steps, the only difference being the use of different negative electrode active materials in Comparative Example 3-16. The corresponding electrochemical performance of the sodium-ion full cell in Comparative Example 3-16 was also tested (at 1C (1C = 100 mA·g)). -1 The charge-discharge test was conducted at a rate of ), and the test results are shown in Table 7.

[0154] Examples 187-201 and Comparative Example 2 follow the same sodium-ion full cell preparation steps, the difference being that Examples 187-201 use the Na₂O₃ prepared in Example 1. x Ni y [Fe(CN)6] z Nanoparticles were used as positive electrode active materials and matched with different negative electrode active materials to test the electrochemical performance of sodium-ion full cells (also known as sodium-ion batteries) in Examples 187-201 (at 1C = 100 mA·g). -1 The test results were compared with those of Comparative Example 2-16 at a charge / discharge rate of 10 ...

[0155] Table 7: Test data of sodium-ion full cells of Examples 187-201 and Comparative Examples 2-16 of the present invention

[0156]

[0157]

[0158] As can be seen from Table 7, the Na prepared in the embodiments of the present invention x Ni y [Fe(CN)6] z Sodium-ion batteries made using nano-cathode materials as the positive electrode active material exhibit good rate performance.

[0159] In the process of preparing substrate-free linked two-dimensional Prussian blue compound nanosheets in Example 1 of the patent document with duplicate patent application number 201610307227.X, 300 mg of Mg2Al-Cl-LDH in step A yielded less than 45 mg of substrate-free linked two-dimensional Prussian blue compound nanosheets in step D.

[0160] Example 1 of this invention prepares Prussian blue-like Na. x Ni y [Fe(CN)6] z In the process of producing nano-cathode materials, 480 mg of the magnesium-aluminum layered bimetallic hydroxide template from step one can ultimately yield approximately 120 mg of the Prussian blue-like Na from step three. x Ni y [Fe(CN)6] z Nanoparticle cathode material. As can be seen, the conversion rate of raw materials is higher during the preparation of the Prussian blue-like nanoparticle cathode material in this invention.

[0161] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a Prussian blue-like nano-cathode material, wherein the Prussian blue-like nano-cathode material is in particulate form, and the particle size of the Prussian blue-like nano-cathode material is less than 60 nm; characterized in that, The preparation method includes the following steps: (1) The layered bimetallic hydroxide template is calcined at a temperature of 300-500℃ and for a time of 2.5-6h. Then it is placed in a sodium ferrocyanide solution and stirred to obtain a layered bimetallic hydroxide with ferrocyanide ion intercalation. (2) The layered bimetallic hydroxide intercalated with ferrocyanide ions is mixed and dispersed with a solvent, then a transition metal salt is added, stirred, and centrifuged to obtain a precipitate. The precipitate is then mixed with an inorganic acid solution, stirred, and centrifuged to obtain the Prussian blue-like nano cathode material. In step (1), the preparation process of the layered bimetallic hydroxide template is as follows: an alkaline solution is added to an aqueous solution of metal salts containing divalent and trivalent metal salts, wherein the molar ratio of the alkali in the alkaline solution to the total molar amount of divalent and trivalent metal salts is 12~28:1, the molar ratio of divalent and trivalent metal salts is 1~3:1, the mixture is stirred, and the mixture formed after stirring is transferred to a high-pressure reactor, heated to 90~150℃ and reacted for 8~16h, centrifuged, washed, and dried to obtain the layered bimetallic hydroxide template; In step (2), the mass ratio of the ferrocyanide ion-intercalated layered bimetallic hydroxide to the transition metal salt is 1:(3~12).

2. The method for preparing the Prussian blue-like nano-cathode material according to claim 1, characterized in that, The particle size of the Prussian blue-like nano cathode material is less than 40 nm.

3. The preparation method according to claim 1, characterized in that, In step (2), the transition metal salt is selected from one or more of ferrous chloride, ferrous nitrate, ferrous sulfate, ferric acetate, cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt acetate, nickel chloride, nickel nitrate, nickel sulfate, nickel acetate, manganese chloride, manganese nitrate, manganese sulfate, manganese acetate, copper chloride, copper nitrate, copper sulfate, copper acetate, zinc chloride, zinc nitrate, zinc sulfate, zinc acetate, and their hydrates.

Images