Sodium ion battery positive electrode active material and preparation method thereof, sodium ion battery

Abstract

The present application provides a sodium ion battery positive electrode active material and a preparation method thereof, and a sodium ion battery, which relates to the field of alkali metal batteries. The sodium ion battery positive electrode active material comprises a base material and a coating layer, wherein the coating layer is coated on the base material; the chemical formula of the base material is Na a Ni x Fe y Mn z M 1‑x‑y‑z O2, wherein 1.05≥a≥0.8, 1.0≥x>0, 1.0≥y>0, 1.0≥z>0, 1.0≥1‑x‑z‑y≥0; wherein the M element includes at least one of Cu, Zn, and Ti; the coating layer includes a first coating layer and a second coating layer, and the second coating layer is coated on the first coating layer; the first coating element in the first coating layer includes at least one of Ca, W, Al, and Zr; and the second coating element in the second coating layer includes F.

Description

Technical Field

[0001] The present application relates to the field of alkali metal batteries, and in particular to a sodium ion battery positive electrode active material and a preparation method thereof, and a sodium ion battery. Background Art

[0002] Among various energy storage technologies, sodium-ion batteries (Na-ion batteries) are a promising alternative to lithium-ion batteries due to their low cost, abundant sodium content, and compatibility with existing production equipment.

[0003] The cathode materials for sodium ion batteries include layered transition metal oxides, polyanionic compounds, Prussian blue analogs and organic materials. Among the many candidate materials, layered transition metal oxides (Na x TMO2) has obvious advantages such as high energy density, simple synthesis and low cost, and is a promising commercial cathode material for SiBs, especially NaO3 structure x TMO2 cathode materials have a relatively high initial sodium content (x≥0.8), which means they have a relatively high initial gram capacity. Although this type of material has obvious advantages in energy density and discharge capacity, its application is hindered by complex phase transitions, particle breakage, and side reactions with the electrolyte in the high voltage charge and discharge range, especially in fast charge mode, where the bulk transfer rate cannot keep up with the Na+ transfer caused by interfacial ion transfer. + Concentration gradients can exacerbate surface phase transitions. Therefore, interfacial modification of O3-structured sodium cathode materials to enhance stability has become a research focus. Summary of the Invention

[0004] The purpose of this application is to provide a sodium ion battery positive electrode active material and a preparation method thereof, and a sodium ion battery to solve the above problems.

[0005] To achieve the above objectives, this application adopts the following technical solutions:

[0006] The present application provides a sodium ion battery positive electrode active material, the sodium ion battery positive electrode active material comprising a base material and a coating layer, wherein the coating layer is coated on the base material;

[0007] The chemical formula of the matrix material is Na a Ni x Fe y Mn z M 1-x-y-z O2, wherein 1.05≥a≥0.8, 1.0≥x>0, 1.0≥y>0, 1.0≥z>0, 1.0>1-xzy≥0; wherein the M element includes at least one of Cu, Zn, and Ti;

[0008] The coating layer includes a first coating layer and a second coating layer, wherein the second coating layer is coated on the first coating layer; the first coating element in the first coating layer includes at least one of Ca, W, Al, and Zr; and the second coating element in the second coating layer includes F.

[0009] Among them, the first coating element is preferably Ca and W.

[0010] Optionally, the thickness of the first coating layer is 0.5-20 nm; the thickness of the second coating layer is 0.1-0.5 nm.

[0011] Optionally, the angle difference of the 003 characteristic peak of the sodium ion battery positive electrode active material is △≤0.2θ.

[0012] The present application also provides a method for preparing a positive electrode active material for a sodium ion battery, comprising:

[0013] A nickel source, a manganese source, an iron source and a solution of the M element are mixed and then added into an alkaline solution for neutralization, and a coprecipitation reaction is carried out under an inert gas atmosphere to obtain a hydroxide precursor;

[0014] mixing the hydroxide precursor with a sodium source and performing a first calcination, and cooling to obtain the first calcined product;

[0015] mixing the first calcined product with a first coating element source and then performing a second calcination, and cooling to obtain a second calcined product;

[0016] The second calcined product is mixed with the second coating element source and then subjected to a third calcination, and the sodium ion battery positive electrode active material is obtained after cooling.

[0017] Optionally, the chemical formula of the hydroxide precursor is Ni x Fe y Mn z M 1-x-y-z (OH)2; wherein, 1.0≥x>0, 1.0≥y>0, 1.0≥z>0, 1.0≥1-xzy≥0.

[0018] Optionally, the first calcined product is the matrix material.

[0019] Optionally, the second calcined product is a sodium ion battery positive electrode material co-coated with the second coating element.

[0020] Optionally, the nickel source includes nickel sulfate, the manganese source includes manganese sulfate, and the iron source includes iron sulfate.

[0021] Optionally, the molar ratio of the nickel source, the manganese source, the iron source and the M element when mixed is x:y:z:1-xyz; wherein, 1.0≥x>0, 1.0≥y>0, 1.0≥z>0, 1.0≥1-xzy≥0.

[0022] Optionally, the alkaline solution includes aqueous ammonia and sodium hydroxide.

[0023] Optionally, the inert gas includes nitrogen, and the purity of the nitrogen is not less than 99.5%.

[0024] Optionally, the reaction conditions of the coprecipitation reaction are: temperature 50-80° C., and pH value of the reaction system during the reaction is 10.5-11.9.

[0025] Optionally, the molar ratio of the metal cations in the hydroxide precursor to the sodium ions in the sodium source is 1:n; wherein 0.95≤n≤1.15.

[0026] Optionally, the first calcination is a multi-stage calcination, including: raising the temperature to 400-550°C at a heating rate of 0.5-10°C / min for pre-sintering for 4-8 hours, then raising the temperature to 800-1100°C at a heating rate of 0.5-10°C / min for sintering for 10-24 hours, and cooling to room temperature with the furnace after sintering.

[0027] Optionally, the first coating element source includes nano-scale particle Ca source, W source, Al source, and Zr source; the amount of the Ca source added is 0.05-1wt% of the mass of the first calcined product, the amount of the W source added is 0.05-0.7wt% of the mass of the first calcined product; the amount of the Al source added is 0.05-0.95wt% of the mass of the first calcined product; and the amount of the Zr source added is 0.05-0.9wt% of the mass of the first calcined product.

[0028] Optionally, the second calcination comprises: heating at a rate of 3°C / min to 650-800°C, calcining for 5-10 hours, and cooling to room temperature along with the furnace.

[0029] Optionally, the second coating element source includes lithium fluoride.

[0030] Optionally, the added amount of the second coating element source is 0.05-1.5 wt % of the mass of the second calcined product.

[0031] Optionally, the third calcination comprises: heating at a rate of 3°C / min to 450-650°C, calcining for 5-10 hours, and cooling to room temperature along with the furnace.

[0032] The present application also includes a sodium ion battery, the raw materials of which include the sodium ion battery positive electrode active material.

[0033] Optionally, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer.

[0034] The positive electrode current collector comprises one of copper foil, aluminum foil, titanium foil, nickel foil, iron foil and zinc foil;

[0035] The raw material of the positive electrode material layer is positive electrode slurry, and the raw materials of the positive electrode slurry include the sodium ion battery positive electrode active material, a first conductive agent, a first binder, and a first solvent.

[0036] The first conductive agent includes at least one of conductive carbon black, carbon fiber, acetylene black, Ketjen black, graphene, and carbon nanotubes.

[0037] The first binder includes at least one of a fluorine-containing resin, a polypropylene resin, a fiber-type binder, and a polyimide-type binder.

[0038] The first solvent includes N-methylpyrrolidone.

[0039] Taking the total mass of the positive electrode material layer as 100%, the positive electrode material layer comprises 95-98% of the sodium ion battery positive electrode active material, 1-3% of the first conductive agent, and 1-2% of the first binder.

[0040] Optionally, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer.

[0041] The negative electrode current collector includes copper foil.

[0042] The raw material of the negative electrode active material layer is negative electrode slurry, and the raw materials of the negative electrode slurry include: negative electrode active material, a second conductive agent, a second binder, and a second solvent.

[0043] The negative electrode active material includes at least one of graphite, silicon-carbon negative electrode, hard carbon and sodium titanate;

[0044] The second conductive agent includes at least one of electric carbon black, carbon fiber, acetylene black, Ketjen black, graphene, and carbon nanotubes.

[0045] The second adhesive includes at least one of a fluorine-containing resin, a polypropylene resin, a fiber-type adhesive, a rubber-type adhesive, and a polyimide-type adhesive.

[0046] The second solvent includes deionized water.

[0047] Taking the total mass of the negative electrode active material layer as 100%, the negative electrode active material layer comprises: 93-98% of the negative electrode active material, 1-3% of the second conductive agent, and 1-4% of the second binder.

[0048] Optionally, the total mass of the electrolyte is 100%, and the electrolyte includes 70-85% electrolyte solvent, 10-15% sodium salt, and 5-15% additives.

[0049] The solvent includes one of propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), 1,2-dimethoxyethane (DME) and triethyl phosphate (TEP); the sodium salt includes one of NaDFOB, NaTFSI, NaPF6, NaClO4, NaFSI and NaBF4; and the additive includes at least one of FEC, VC, PDO, PTS, DTD, TMSPi, NaFSI and NaDFOB.

[0050] Optionally, the diaphragm includes one of a single-layer polymer diaphragm, a multi-layer polymer diaphragm, a ceramic diaphragm, or a polymer-ceramic composite diaphragm.

[0051] Compared with the prior art, the advantages of this application include:

[0052] The sodium ion battery positive electrode active material provided in this application is doped and coated with elements such as F, Ca, and W. The first coating layer belongs to the inner interface of the particle, and the elements used are W and Ca. 2+ The ionic radius of Na + Close to, occupying the oxygen octahedral coordination of the alkali metal layer can alleviate the slip of the transition metal layer caused by the electrostatic repulsion generated by the sodium ion escape, and reduce the volume change of the positive electrode material during the charge and discharge process, while W 6+ The ionic radius of Ni 2+ 、Mn 4+ 、Fe 2+ Close, more inclined to occupy the oxygen octahedral coordination of the transition metal, and the WO bond energy is stronger, which is conducive to shortening the interlayer spacing of the transition metal layer and expanding the interlayer spacing of the alkali metal layer. The thickness of the second coating layer is increased by using the more electronegative F - Ion replacement of O 2- , due to F - The electronegativity of the ion is greater, and the ability to attract electrons in the transition metal is stronger. The ionic bond length of F-TM is shorter, and the Na-O bond becomes longer, which reduces the diffusion energy barrier of sodium ions, thereby increasing the sodium ion expansion rate of the first coating layer, and further promoting the sodium ion deintercalation rate inside the particles. This double-layer coating design and regulation mechanism, while not reducing the surface ion transfer rate, can also solve the surface phase change problem of the positive electrode material in a highly desodiumized state (i.e., the transformation from layered-spinel phase to salt rock phase), prevent the corrosion of the positive electrode material by HF in the electrolyte, and reduce the dissolution of transition metal elements. The sodium ion battery prepared using the positive electrode material provided by this application has better structural stability and cycle performance.

[0053] The preparation method provided in this application is simple and convenient, and can obtain a positive electrode material with performance advantages and strong stability.

[0054] The sodium ion battery provided in this application has good stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope of the present application.

[0056] Figure 1 Schematic diagram of the structure of the positive electrode active material for sodium ion batteries prepared in Example;

[0057] Figure 2 is a SEM spectrum of the positive electrode active material prepared in Example;

[0058] Figure 3 XRD spectra of the positive electrode materials of Example 1 and Comparative Example 2 after 1000 cycles;

[0059] Figure 4 for Figure 3 A locally enlarged XRD spectrum in the range of 16-17. DETAILED DESCRIPTION

[0060] In order to better explain the technical solution provided by this application, the technical solution will be described as a whole before the specific implementation methods are described.

[0061] In a first aspect, the present application provides a positive electrode active material for a sodium ion battery, the positive electrode active material for a sodium ion battery comprising a base material and a coating layer, wherein the coating layer is coated on the base material;

[0062] The chemical formula of the matrix material is Na a Ni x Fe y Mn z M 1-x-y-z O2, wherein 1.05≥a≥0.8, 1.0≥x>0, 1.0≥y>0, 1.0≥z>0, 1.0>1-xzy≥0; wherein the M element includes at least one of Cu, Zn, and Ti.

[0063] The coating layer includes a first coating layer and a second coating layer, wherein the second coating layer is coated on the first coating layer; the first coating element in the first coating layer includes at least one of Ca, W, Al, and Zr; and the second coating element in the second coating layer includes F.

[0064] The first coating layer belongs to the inner interface of the particle, and the elements used are W and Ca. 2+ The ionic radius of Na + Close to, occupying the oxygen octahedral coordination of the alkali metal layer can alleviate the slip of the transition metal layer caused by the electrostatic repulsion generated by the sodium ion escape, and reduce the volume change of the positive electrode material during the charge and discharge process, while W 6+ The ionic radius of Ni 2+ 、Mn 4+ 、Fe 2+ Close, more inclined to occupy the oxygen octahedral coordination of the transition metal, and the WO bond energy is stronger, which is conducive to shortening the interlayer spacing of the transition metal layer and expanding the interlayer spacing of the alkali metal layer. The thickness of the second coating layer is increased by using the more electronegative F - Ion replacement of O 2- , due to F - The greater electronegativity of the ions makes them more attractive to electrons from transition metals, shortening the ionic bond length of the F-TM and lengthening the Na-O bond, reducing the diffusion barrier for sodium ions. This increases the sodium ion diffusion rate in the first coating layer and further promotes the sodium ion deintercalation rate within the particle. This double-layer coating design and control mechanism not only maintains the surface ion transport rate but also addresses the surface phase transition problem (i.e., the transition from layered to spinel phase to salt rock phase) of the cathode material in a highly desodiumated state, preventing HF corrosion in the electrolyte and reducing the dissolution of transition metal elements.

[0065] In an optional embodiment, the thickness of the first coating layer is 0.5-20 nm; the thickness of the second coating layer is 0.1-0.5 nm.

[0066] Optionally, the thickness of the first coating layer can be 0.5 nm, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, or any value between 0.5-20 nm.

[0067] Optionally, the thickness of the second coating layer may be 0.1 nm, 0.2 nm, 0.3 nm, 0.4 nm, 0.5 nm, or any value between 0.1-0.5 nm.

[0068] In an optional embodiment, the angle difference of the 003 characteristic peak of the sodium ion battery positive electrode active material is △≤0.2θ.

[0069] From a technical perspective, the position of the 003 peak directly reflects the c-axis parameters for layered oxides. Converted to interplanar spacing, the d value fluctuates by less than 0.0005 nm. Sodium-ion battery cathodes and active materials often have layered structures, and their (003) interplanar spacing directly influences the insertion and extraction kinetics and structural stability of Na⁺. A 003 peak shift of ≤0.2θ before and after charge and discharge indicates good structural stability.

[0070] In a second aspect, the present application further provides a method for preparing a positive electrode active material for a sodium ion battery, comprising:

[0071] A nickel source, a manganese source, an iron source and a solution of the M element are mixed and then added into an alkaline solution for neutralization, and a coprecipitation reaction is carried out under an inert gas atmosphere to obtain a hydroxide precursor;

[0072] mixing the hydroxide precursor with a sodium source and performing a first calcination, and cooling to obtain the first calcined product;

[0073] mixing the first calcined product with a first coating element source and then performing a second calcination, and cooling to obtain a second calcined product;

[0074] The second calcined product is mixed with the second coating element source and then subjected to a third calcination, and the sodium ion battery positive electrode active material is obtained after cooling.

[0075] In an optional embodiment, the chemical formula of the hydroxide precursor is Ni x Fe y Mn z M 1-x-y-z (OH)2; wherein, 1.0≥x>0, 1.0≥y>0, 1.0≥z>0, 1.0≥1-xzy≥0.

[0076] Wherein, the first calcined product is the matrix material.

[0077] In an optional embodiment, the second calcined product is a sodium ion battery positive electrode material co-coated with the second coating element.

[0078] In an optional embodiment, the nickel source includes nickel sulfate, the manganese source includes manganese sulfate, and the iron source includes iron sulfate.

[0079] In an optional embodiment, the molar ratio of the nickel source, the manganese source, the iron source and the M element when mixed is x:y:z:1-xyz; wherein, 1.0≥x>0, 1.0≥y>0, 1.0≥z>0, 1.0≥1-xzy≥.

[0080] In an optional embodiment, the alkaline solution includes aqueous ammonia and sodium hydroxide.

[0081] In an optional embodiment, the inert gas includes nitrogen, and the purity of the nitrogen is 99.5%.

[0082] Optionally, the purity of the nitrogen may be 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or 100%, or the purity of the nitrogen may be any value between 99.5% and 100%.

[0083] In an optional embodiment, the reaction conditions of the coprecipitation reaction are: temperature 50-80° C., and pH value of the reaction system during the reaction is 10.5-11.9.

[0084] Optionally, the temperature of the coprecipitation reaction can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, or any value between 50-80°C; the pH value of the reaction system during the reaction can be 10.5, 10.6, 10.7, 10.8, 10.9, 11, 11.1, 11.2, 11.3, 11.4, 11.5, 11.6, 11.7, 11.8, 11.9, or any value between 10.5-11.9.

[0085] In an optional embodiment, the molar ratio of the metal cations in the hydroxide precursor to the sodium ions in the sodium source is 1:n; wherein 0.95≤n≤1.15.

[0086] Optionally, the molar ratio of the metal cations in the hydroxide precursor to the sodium ions in the sodium source can be 1:0.95, 1:0.96, 1:0.97, 1:0.98, 1:0.99, 1:1, 1:1.01, 1:1.02, 1:1.03, 1:1.04, 1:1.05, 1:1.06, 1:1.07, 1:1.08, 1:1.09, 1:1.1, 1:1.11, 1:1.12, 1:1.13, 1:1.14, 1:1.15, or any value between 1:0.95 and 1.15.

[0087] In an optional embodiment, the first calcination is a multi-stage calcination, including: raising the temperature to 400-550°C at a heating rate of 0.5-10°C / min for pre-sintering for 4-8 hours, then raising the temperature to 800-1100°C at a heating rate of 0.5-10°C / min for sintering for 10-24 hours, and cooling to room temperature with the furnace after sintering.

[0088] Optionally, the heating rate of the pre-sintering can be 0.5℃ / min, 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, or any value between 0.5-10℃ / min; the pre-sintering temperature can be 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃, 550℃ or any value between 400-550℃; the pre-sintering time can be 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h, or any value between 4-8h.

[0089] Optionally, the sintering heating rate can be 0.5°C / min, 1°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, or any value between 0.5-10°C / min; the sintering temperature can be 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C, 900°C, 910°C, 920°C, 930°C, 940°C ℃, 950℃, 960℃, 970℃, 980℃, 990℃, 1000℃, 1010℃, 1020℃, 1030℃, 1040℃, 1050℃, 1060℃, 1070℃, 1080℃, 1090℃, 1100℃, or any value between 800-1100℃; the sintering time can be 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, or any value between 10-24h.

[0090] In an optional embodiment, the first coating element source includes nano-sized particles of Ca source, W source, Al source, and Zr source; the amount of the Ca source added is 0.05-1wt% of the mass of the first calcined product, the amount of the W source added is 0.05-0.7% of the mass of the first calcined product; the amount of the Al source added is 0.05-0.95% of the mass of the first calcined product; and the amount of the Zr source added is 0.05-0.9% of the mass of the first calcined product.

[0091] In an optional embodiment, the second calcination comprises: heating at a rate of 3°C / min to 650-800°C, calcining for 5-10 hours, and cooling to room temperature along with the furnace.

[0092] Optionally, the endpoint temperature of the second calcination can be 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, 760℃, 770℃, 780℃, 790℃, 800℃, or any value between 650-800℃; the calcination time of the second calcination can be 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, 10h, or any value between 5-10h.

[0093] In an optional embodiment, the second coating element source includes lithium fluoride.

[0094] In an optional embodiment, the added amount of the second coating element source is 0.05-1.5 wt % of the mass of the second calcined product.

[0095] Optionally, the amount of the second coating element source added is 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, or any value between 0.05-1.5 wt% of the mass of the second calcined product.

[0096] In an optional embodiment, the third calcination comprises: heating at a rate of 3°C / min to 450-650°C for 5-10 hours, and cooling to room temperature with the furnace. Optionally, the temperature of the third calcination can be 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, or any value between 450-650°C; the time of the third calcination can be 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, 10h, or any value between 5-10h.

[0097] The present application also includes a sodium ion battery, the raw materials of which include the sodium ion battery positive electrode active material.

[0098] In an optional embodiment, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer.

[0099] The positive electrode current collector comprises one of copper foil, aluminum foil, titanium foil, nickel foil, iron foil and zinc foil;

[0100] The raw material of the positive electrode material layer is positive electrode slurry, and the raw materials of the positive electrode slurry include the sodium ion battery positive electrode active material, a first conductive agent, a first binder, and a first solvent.

[0101] The first conductive agent includes at least one of conductive carbon black, carbon fiber, acetylene black, Ketjen black, graphene, and carbon nanotubes.

[0102] The first binder includes at least one of a fluorine-containing resin, a polypropylene resin, a fiber-type binder, and a polyimide-type binder.

[0103] The first solvent includes N-methylpyrrolidone.

[0104] Taking the total mass of the positive electrode material layer as 100%, the positive electrode material layer comprises 95-98% of the sodium ion battery positive electrode active material, 1-3% of the first conductive agent, and 1-3% of the first binder.

[0105] Optionally, based on the total mass of the positive electrode material layer as 100%, the content of the positive electrode active material can be 95%, 96%, 97%, 98%, or any value between 95-98%; the content of the first conductive agent can be 1%, 2%, 3%, or any value between 1-3%; the content of the first binder can be 1%, 2%, 3%, or any value between 1-3%.

[0106] Optionally, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer.

[0107] The negative electrode current collector includes copper foil.

[0108] The raw material of the negative electrode active material layer is negative electrode slurry, and the raw materials of the negative electrode slurry include: negative electrode active material, a second conductive agent, a second binder, and a second solvent.

[0109] The negative electrode active material includes at least one of graphite, silicon-carbon negative electrode, hard carbon and sodium titanate;

[0110] The second conductive agent includes at least one of electric carbon black, carbon fiber, acetylene black, Ketjen black, graphene, and carbon nanotubes.

[0111] The second adhesive includes at least one of a fluorine-containing resin, a polypropylene resin, a fiber-type adhesive, a rubber-type adhesive, and a polyimide-type adhesive.

[0112] The second solvent includes deionized water.

[0113] Taking the total mass of the negative electrode active material layer as 100%, the negative electrode active material layer comprises: 92-98% of the negative electrode active material, 1-3% of the second conductive agent, and 1.5-4% of the second binder.

[0114] Optionally, based on the total mass of the negative electrode active material layer as 100%, the content of the negative electrode active material can be 92%, 93%, 94%, 95%, 96%, 97%, 98%, or any value between 92-98%; the content of the second conductive agent can be 1%, 2%, 3%, or any value between 1-3%; the amount of the second binder can be 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, or any value between 1.5-4%.

[0115] In an optional embodiment, the total mass of the electrolyte is 100%, and the electrolyte comprises 70-85% electrolyte solvent, 10-15% sodium salt, and 5-15% additives.

[0116] Optionally, based on the total mass of the electrolyte as 100%, the amount of electrolyte solvent used can be 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, or any value between 70-85%; the amount of the additive can be 10%, 11%, 12%, 13%, 14%, 15%, or any value between 10-15%; the amount of the additive can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any value between 5-15%.

[0117] The solvent includes one of propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), 1,2-dimethoxyethane (DME) and triethyl phosphate (TEP); the sodium salt includes one of NaDFOB, NaTFSI, NaPF6, NaClO4, NaFSI and NaBF4; and the additive includes at least one of FEC, VC, PDO, PTS, DTD, TMSPi, NaFSI and NaDFOB.

[0118] In an optional embodiment, the separator includes one of a single-layer polymer separator, a multi-layer polymer separator, a ceramic separator, or a polymer-ceramic composite separator.

[0119] The embodiments of the present application will be described in detail below in conjunction with specific examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. The reagents or instruments used are not specified by the manufacturer and are conventional products that can be purchased commercially.

[0120] Example 1

[0121] This embodiment provides a positive electrode active material for a sodium ion battery, and the specific preparation method is as follows:

[0122] Nickel sulfate, manganese sulfate, and ferric sulfate solutions were mixed evenly in a molar ratio of Ni:Fe:Mn = 33:30:37, and 2 mol / L ammonia and sodium hydroxide solution were added to the solution for neutralization. Co-precipitation reaction was carried out under a nitrogen atmosphere with a purity of 99.5% to obtain the hydroxide precursor Ni 0.33 Fe 0.3 Mn 0.37 (OH)2, the obtained precipitate was filtered and washed, and dried at 150°C for 5h to obtain a dried product.

[0123] The hydroxide precursor Ni 0.33 Fe 0.3 Mn 0.37 (OH)2 and sodium carbonate were weighed according to the molar ratio of metal cations to Na ions in the precursor of 1:1.05, and the two substances were mixed evenly, and then sintered in stages in a sintering furnace: first, the temperature was raised to 400 ° C at a heating rate of 3 ° C / min for 8 hours of pre-sintering in an air atmosphere, and then the temperature was raised to 940 ° C at a heating rate of 3 ° C / min for 16 hours in an air atmosphere. After sintering, the furnace was cooled and the matrix material Na was obtained. 0.98 Ni 0.33 Fe 0.3 Mn 0.37 O2, crush the material through a roller mill / air flow crusher, sieve through 300 mesh, and set aside.

[0124] The matrix material Na 0.98 Ni 0.33 Fe 0.3 Mn 0.37 CaCO3 and WO3 with a particle size of 30-200 nm were added to O2 in amounts of 0.3% wt and 0.1% wt of the matrix material, respectively. After mixing evenly, the mixture was calcined at 750° C. for 7 h to obtain a second calcined product.

[0125] 30-200 nm LiF was added to the second calcined product in an amount of 0.15% of the mass percentage of the second calcined product, mixed evenly and calcined at 590 ° C for 5 h to finally obtain a secondary coated sodium cathode material, which is a single crystal material with Dv50 = 4.2 μm and BET of 0.45 m 2 / g. The schematic diagram of the obtained positive electrode material is shown in Figure 1 As shown, the SEM spectrum of the prepared sodium ion battery positive electrode active material is as follows Figure 2 shown.

[0126] This embodiment also provides a sodium ion battery, whose raw materials include the above-mentioned positive electrode material, binder, polyacrylonitrile copolymer, and carbon nanotubes in a ratio of 95.5%:1.5%:2%:1% to make a positive electrode slurry, which is coated on aluminum foil to make a positive electrode sheet. The negative electrode sheet uses a hard carbon negative electrode material. The electrolyte includes an organic solvent and a sodium salt. Propylene carbonate, ethylene carbonate, and dimethyl carbonate are uniformly mixed in an inert atmosphere at a mass ratio of 1:1:1, and then sodium hexafluorophosphate is dissolved in the mixed solvent to prepare a 1 mol / L electrolyte. A polyethylene film or a polyethylene plus ceramic coating film is used as a separator. The remaining steps are assembled into a sodium ion battery according to conventional methods, and corresponding electrical performance tests are performed.

[0127] Example 2

[0128] This embodiment provides a positive electrode active material for a sodium ion battery, and the specific preparation method is as follows:

[0129] Nickel sulfate, manganese sulfate, iron sulfate and zinc sulfate solutions were mixed evenly in a molar ratio of Ni:Fe:Mn:Zn=33:30:30:7, 2 mol / L ammonia water and sodium hydroxide solution were added to the solution for neutralization, and a coprecipitation reaction was carried out under a nitrogen atmosphere with a purity of 99.5% to obtain the hydroxide precursor Ni 0.33 Fe 0.3 Mn 0.3 (OH)2, the obtained precipitate was filtered and washed, and dried at 150°C for 5h to obtain a dried product.

[0130] The hydroxide precursor Ni 0.33 Fe 0.3 Mn 0.3 (OH)2 and sodium carbonate were weighed according to the molar ratio of metal cations to Na ions in the precursor of 1:1.05, and the two substances were mixed evenly, and then sintered in stages in a sintering furnace: first, the temperature was raised to 400 ° C at a heating rate of 3 ° C / min for 8 hours of pre-sintering in an air atmosphere, and then the temperature was raised to 940 ° C at a heating rate of 3 ° C / min for 16 hours in an air atmosphere. After sintering, the furnace was cooled and the matrix material Na was obtained. 0.98 Ni 0.33 Fe 0.3 Mn 0.3 O2, crush the material through a roller mill / air flow crusher, sieve through 300 mesh, and set aside.

[0131] The matrix material Na 0.98 Ni 0.33 Fe 0.3 Mn 0.3CaCO3 and WO3 with a particle size of 30-200 nm were added to O2 in amounts of 0.3% wt and 0.1% wt of the matrix material, respectively. After mixing evenly, the mixture was calcined at 750° C. for 7 h to obtain a second calcined product.

[0132] 30-200 nm LiF was added to the second calcined product in an amount of 0.15% of the mass percentage of the second calcined product, mixed evenly and calcined at 590 ° C for 5 h to finally obtain a secondary coated sodium cathode material, which is a single crystal material with Dv50 = 3.95 μm and BET of 0.49 m 2 / g.

[0133] This embodiment also provides a sodium ion battery, whose raw materials include the above-mentioned positive electrode material, binder, polyacrylonitrile copolymer, and carbon nanotubes in a ratio of 95.5%:1.5%:2%:1% to make a positive electrode slurry, which is coated on aluminum foil to make a positive electrode sheet. The negative electrode sheet uses a hard carbon negative electrode material. The electrolyte includes an organic solvent and a sodium salt. Propylene carbonate, ethylene carbonate, and dimethyl carbonate are uniformly mixed in an inert atmosphere at a mass ratio of 1:1:1, and then sodium hexafluorophosphate is dissolved in the mixed solvent to prepare a 1 mol / L electrolyte. A polyethylene film or a polyethylene plus ceramic coating film is used as a separator. The remaining steps are assembled into a sodium ion battery according to conventional methods, and corresponding electrical performance tests are performed.

[0134] Example 3

[0135] This embodiment provides a positive electrode active material for a sodium ion battery, and the specific preparation method is as follows:

[0136] Nickel sulfate, manganese sulfate, iron sulfate and zinc sulfate solutions were mixed evenly in a molar ratio of Ni:Fe:Mn:Zn=33:30:30:7, 2 mol / L ammonia water and sodium hydroxide solution were added to the solution for neutralization, and a coprecipitation reaction was carried out under a nitrogen atmosphere with a purity of 99.5% to obtain the hydroxide precursor Ni 0.33 Fe 0.3 Mn 0.3 Zn 0.07 (OH)2, the obtained precipitate was filtered and washed, and dried at 150°C for 5h to obtain a dried product.

[0137] The hydroxide precursor Ni 0.33 Fe 0.3 Mn 0.3 Zn 0.07(OH)2 and sodium carbonate were weighed according to the molar ratio of metal cations to Na ions in the precursor of 1:1.05, and the two substances were mixed evenly, and then sintered in stages in a sintering furnace: first, the temperature was raised to 400 ° C at a heating rate of 3 ° C / min for 8 hours of pre-sintering in an air atmosphere, and then the temperature was raised to 940 ° C at a heating rate of 3 ° C / min for 16 hours in an air atmosphere. After sintering, the furnace was cooled and the matrix material Na was obtained. 0.98 Ni 0.33 Fe 0.3 Mn 0.3 Zn 0.07 O2, crush the material through a roller mill / air flow crusher, sieve through 300 mesh, and set aside.

[0138] The matrix material Na 0.98 Ni 0.33 Fe 0.3 Mn 0.3 CaCO3 and WO3 with a particle size of 30-200 nm were added to O2 in amounts of 0.3% wt and 0.1% wt of the matrix material, respectively. After mixing evenly, the mixture was calcined at 750° C. for 7 h to obtain a second calcined product.

[0139] 30-200 nm LiF was added to the second calcined product in an amount of 0.3% of the mass percentage of the second calcined product. After mixing evenly, it was calcined at 590 ° C for 5 h to finally obtain a secondary coated sodium positive electrode material, which is a single crystal material with Dv50 = 4.13 μm and BET of 0.42 m 2 / g.

[0140] This embodiment also provides a sodium ion battery, whose raw materials include the above-mentioned positive electrode material, binder, polyacrylonitrile copolymer, and carbon nanotubes in a ratio of 95.5%:1.5%:2%:1% to make a positive electrode slurry, which is coated on aluminum foil to make a positive electrode sheet. The negative electrode sheet uses a hard carbon negative electrode material. The electrolyte includes an organic solvent and a sodium salt. Propylene carbonate, ethylene carbonate, and dimethyl carbonate are uniformly mixed in an inert atmosphere at a mass ratio of 1:1:1, and then sodium hexafluorophosphate is dissolved in the mixed solvent to prepare a 1 mol / L electrolyte. A polyethylene film or a polyethylene plus ceramic coating film is used as a separator. The remaining steps are assembled into a sodium ion battery according to conventional methods, and corresponding electrical performance tests are performed.

[0141] Example 4

[0142] This embodiment provides a positive electrode active material for a sodium ion battery, and the specific preparation method is as follows:

[0143] Nickel sulfate, manganese sulfate, iron sulfate and zinc sulfate solutions were mixed evenly in a molar ratio of Ni:Fe:Mn:Zn=33:30:30:7, 2 mol / L ammonia water and sodium hydroxide solution were added to the solution for neutralization, and a coprecipitation reaction was carried out under a nitrogen atmosphere with a purity of 99.5% to obtain the hydroxide precursor Ni 0.33 Fe 0.3 Mn 0.3 Zn 0.07 (OH)2, the obtained precipitate was filtered and washed, and dried at 150°C for 5h to obtain a dried product.

[0144] The hydroxide precursor Ni 0.33 Fe 0.3 Mn 0.3 Zn 0.07 (OH)2 and sodium carbonate were weighed according to the molar ratio of metal cations to Na ions in the precursor of 1:1.05, and the two substances were mixed evenly, and then sintered in stages in a sintering furnace: first, the temperature was raised to 400 ° C at a heating rate of 3 ° C / min for 8 hours of pre-sintering in an air atmosphere, and then the temperature was raised to 940 ° C at a heating rate of 3 ° C / min for 16 hours in an air atmosphere. After sintering, the furnace was cooled and the matrix material Na was obtained. 0.98 Ni 0.33 Fe 0.3 Mn 0.3 O2, crush the material through a roller mill / air flow crusher, sieve through 300 mesh, and set aside.

[0145] The matrix material Na 0.98 Ni 0.33 Fe 0.3 Mn 0.3 CaCO3 and WO3 with a particle size of 30-200nm were added to O2, and the added amounts were 0.3%wt and 0.1%wt of the matrix material respectively. Al2O3 with an additional mass percentage of 0.6wt% of the matrix material was also added. After mixing evenly, the mixture was calcined at 750℃ for 7h to obtain a second calcined product.

[0146] 30-200 nm LiF was added to the second calcined product in an amount of 0.3% of the mass percentage of the second calcined product. After mixing evenly, it was calcined at 590 ° C for 5 h to finally obtain a secondary coated sodium positive electrode material, which is a single crystal material with Dv50 = 2.85 μm and BET of 0.51 m 2 / g.

[0147] This embodiment also provides a sodium ion battery, whose raw materials include the above-mentioned positive electrode material, binder, polyacrylonitrile copolymer, and carbon nanotubes in a ratio of 95.5%:1.5%:2%:1% to make a positive electrode slurry, which is coated on aluminum foil to make a positive electrode sheet. The negative electrode sheet uses a hard carbon negative electrode material. The electrolyte includes an organic solvent and a sodium salt. Propylene carbonate, ethylene carbonate, and dimethyl carbonate are uniformly mixed in an inert atmosphere at a mass ratio of 1:1:1, and then sodium hexafluorophosphate is dissolved in the mixed solvent to prepare a 1 mol / L electrolyte. A polyethylene film or a polyethylene plus ceramic coating film is used as a separator. The remaining steps are assembled into a sodium ion battery according to conventional methods, and corresponding electrical performance tests are performed.

[0148] Example 5

[0149] This embodiment provides a positive electrode active material for a sodium ion battery, and the specific preparation method is as follows:

[0150] Nickel sulfate, manganese sulfate, iron sulfate and zinc sulfate solutions were mixed evenly in a molar ratio of Ni:Fe:Mn:Zn=33:30:30:7, 2 mol / L ammonia water and sodium hydroxide solution were added to the solution for neutralization, and a coprecipitation reaction was carried out under a nitrogen atmosphere with a purity of 99.5% to obtain the hydroxide precursor Ni 0.33 Fe 0.3 Mn 0.3 (OH)2, the obtained precipitate was filtered and washed, and dried at 150°C for 5h to obtain a dried product.

[0151] The hydroxide precursor Ni 0.33 Fe 0.3 Mn 0.3 (OH)2 and sodium carbonate were weighed according to the molar ratio of metal cations to Na ions in the precursor of 1:1.05, and the two substances were mixed evenly, and then sintered in stages in a sintering furnace: first, the temperature was raised to 400 ° C at a heating rate of 3 ° C / min for 8 hours of pre-sintering in an air atmosphere, and then the temperature was raised to 940 ° C at a heating rate of 3 ° C / min for 16 hours in an air atmosphere. After sintering, the furnace was cooled and the matrix material Na was obtained. 0.98 Ni 0.33 Fe 0.3 Mn 0.3 O2, crush the material through a roller mill / air flow crusher, sieve through 300 mesh, and set aside.

[0152] The matrix material Na 0.98 Ni 0.33 Fe 0.3 Mn 0.3CaCO3 and WO3 with a particle size of 30-200nm were added to O2, and the added amounts were 0.3%wt and 0.1%wt of the matrix material respectively. ZrO2 with a matrix material percentage of 0.6wt% was also added. After mixing evenly, the mixture was calcined at 750℃ for 7h to obtain a second calcined product.

[0153] 30-200 nm LiF was added to the second calcined product in an amount of 0.3% of the mass percentage of the second calcined product. After mixing evenly, it was calcined at 590 ° C for 5 h to finally obtain a secondary coated sodium positive electrode material, which is a single crystal material with Dv50 = 3.72 μm and BET of 0.487 m 2 / g.

[0154] This embodiment also provides a sodium ion battery, whose raw materials include the above-mentioned positive electrode material, binder, polyacrylonitrile copolymer, and carbon nanotubes in a ratio of 95.5%:1.5%:2%:1% to make a positive electrode slurry, which is coated on aluminum foil to make a positive electrode sheet. The negative electrode sheet uses a hard carbon negative electrode material. The electrolyte includes an organic solvent and a sodium salt. Propylene carbonate, ethylene carbonate, and dimethyl carbonate are uniformly mixed in an inert atmosphere at a mass ratio of 1:1:1, and then sodium hexafluorophosphate is dissolved in the mixed solvent to prepare a 1 mol / L electrolyte. A polyethylene film or a polyethylene plus ceramic coating film is used as a separator. The remaining steps are assembled into a sodium ion battery according to conventional methods, and corresponding electrical performance tests are performed.

[0155] Example 6

[0156] This embodiment provides a positive electrode active material for a sodium ion battery, and the specific preparation method is as follows:

[0157] Nickel sulfate, manganese sulfate, iron sulfate and titanium sulfate solutions were mixed evenly in a molar ratio of Ni:Fe:Mn:Ti=33:20:42:5, 2 mol / L ammonia water and sodium hydroxide solution were added to the solution for neutralization, and a coprecipitation reaction was carried out under a nitrogen atmosphere with a purity of 99.5% to obtain the hydroxide precursor Ni 0.33 Fe 0.2 Mn 0.42 Ti 0.05 (OH)2, the obtained precipitate was filtered and washed, and dried at 150°C for 5h to obtain a dried product.

[0158] The hydroxide precursor Ni 0.33 Fe 0.2 Mn 0.42 Ti 0.05(OH)2 and sodium carbonate were weighed according to the molar ratio of metal cations to Na ions in the precursor of 1:1.05, and the two substances were mixed evenly, and then sintered in stages in a sintering furnace: first, the temperature was raised to 400 ° C at a heating rate of 3 ° C / min for 8 hours of pre-sintering in an air atmosphere, and then the temperature was raised to 940 ° C at a heating rate of 3 ° C / min for 16 hours in an air atmosphere. After sintering, the furnace was cooled and the matrix material Ni was obtained. 0.33 Fe 0.2 Mn 0.42 Ti 0.05 (OH)2, crush the material with a roller mill / air flow crusher, sieve with 300 mesh, and set aside.

[0159] The matrix material Na 0.98 Ni 0.33 Fe 0.2 Mn 0.42 Ti 0.05 CaCO3 and WO3 with a particle size of 30-200nm were added to O2, and the added amounts were 0.3%wt and 0.1%wt of the matrix material respectively. ZrO2 with an additional mass percentage of 0.6wt% of the matrix material was also added. After mixing evenly, the mixture was calcined at 750℃ for 7h to obtain a second calcined product.

[0160] 30-200 nm LiF was added to the second calcined product in an amount of 0.3% of the mass percentage of the second calcined product, mixed evenly and calcined at 590 ° C for 5 h to finally obtain a secondary coated sodium cathode material, which is a single crystal material with Dv50 = 4.28 μm and BET of 0.52 m 2 / g.

[0161] This embodiment also provides a sodium ion battery, whose raw materials include the above-mentioned positive electrode material, binder, polyacrylonitrile copolymer, and carbon nanotubes in a ratio of 95.5%:1.5%:2%:1% to make a positive electrode slurry, which is coated on aluminum foil to make a positive electrode sheet. The negative electrode sheet uses a hard carbon negative electrode material. The electrolyte includes an organic solvent and a sodium salt. Propylene carbonate, ethylene carbonate, and dimethyl carbonate are uniformly mixed in an inert atmosphere at a mass ratio of 1:1:1, and then sodium hexafluorophosphate is dissolved in the mixed solvent to prepare a 1 mol / L electrolyte. A polyethylene film or a polyethylene plus ceramic coating film is used as a separator. The remaining steps are assembled into a sodium ion battery according to conventional methods, and corresponding electrical performance tests are performed.

[0162] Example 7

[0163] This embodiment provides a positive electrode active material for a sodium ion battery, and the specific preparation method is as follows:

[0164] Nickel sulfate, manganese sulfate, iron sulfate and copper sulfate solutions were mixed evenly in a molar ratio of Ni:Fe:Mn:Cu=33:20:42:5, 2 mol / L ammonia water and sodium hydroxide solution were added to the solution for neutralization, and a coprecipitation reaction was carried out under a nitrogen atmosphere with a purity of 99.5% to obtain the hydroxide precursor Ni 0.33 Fe 0.2 Mn 0.42 Cu 0.05 (OH)2, the obtained precipitate was filtered and washed, and dried at 150°C for 5h to obtain a dried product.

[0165] The hydroxide precursor Ni 0.33 Fe 0.2 Mn 0.42 Cu 0.05 (OH)2 and sodium carbonate were weighed according to the molar ratio of metal cations to Na ions in the precursor of 1:1.05, and the two substances were mixed evenly, and then sintered in stages in a sintering furnace: first, the temperature was raised to 400 ° C at a heating rate of 3 ° C / min for 8 hours of pre-sintering in an air atmosphere, and then the temperature was raised to 940 ° C at a heating rate of 3 ° C / min for 16 hours in an air atmosphere. After sintering, the furnace was cooled and the matrix material Na was obtained. 0.98 Ni 0.33 Fe 0.2 Mn 0.42 Cu 0.05 O2, crush the material through a roller mill / air flow crusher, sieve through 300 mesh, and set aside.

[0166] The matrix material Na 0.98 Ni 0.33 Fe 0.2 Mn 0.42 Cu 0.05 CaCO3 and WO3 with a particle size of 30-200nm are added to O2, and the added amounts are 0.3%wt and 0.1%wt of the matrix material respectively. ZrO2 with a mass percentage of 0.6wt% of the matrix material and Al2O3 with a mass percentage of 0.06wt% of the matrix material are also added. After mixing evenly, the mixture is calcined at 750℃ for 7h to obtain a second calcined product.

[0167] 30-200 nm LiF was added to the second calcined product in an amount of 0.3% of the mass percentage of the second calcined product. After mixing evenly, it was calcined at 590 ° C for 5 h to finally obtain a secondary coated sodium positive electrode material, which is a single crystal material with Dv50 = 4.34 μm and BET of 0.51 m 2 / g.

[0168] This embodiment also provides a sodium ion battery, whose raw materials include the above-mentioned positive electrode material, binder, polyacrylonitrile copolymer, and carbon nanotubes in a ratio of 95.5%:1.5%:2%:1% to make a positive electrode slurry, which is coated on aluminum foil to make a positive electrode sheet. The negative electrode sheet uses a hard carbon negative electrode material. The electrolyte includes an organic solvent and a sodium salt. Propylene carbonate, ethylene carbonate, and dimethyl carbonate are uniformly mixed in an inert atmosphere at a mass ratio of 1:1:1, and then sodium hexafluorophosphate is dissolved in the mixed solvent to prepare a 1 mol / L electrolyte. A polyethylene film or a polyethylene plus ceramic coating film is used as a separator. The remaining steps are assembled into a sodium ion battery according to conventional methods, and corresponding electrical performance tests are performed.

[0169] Example 8

[0170] This embodiment provides a positive electrode active material for a sodium ion battery, and the specific preparation method is as follows:

[0171] Nickel sulfate, manganese sulfate, iron sulfate and titanium sulfate solutions were mixed evenly in a molar ratio of Ni:Fe:Mn:Ti=33:20:42:5, 2 mol / L ammonia water and sodium hydroxide solution were added to the solution for neutralization, and a coprecipitation reaction was carried out under a nitrogen atmosphere with a purity of 99.5% to obtain the hydroxide precursor Ni 0.33 Fe 0.2 Mn 0.42 Ti 0.05 (OH)2, the obtained precipitate was filtered and washed, and dried at 150°C for 5h to obtain a dried product.

[0172] The hydroxide precursor Ni 0.33 Fe 0.2 Mn 0.42 Ti 0.05 (OH)2 and sodium carbonate were weighed according to the molar ratio of metal cations to Na ions in the precursor of 1:1.05, and the two substances were mixed evenly, and then sintered in stages in a sintering furnace: first, the temperature was raised to 400 ° C at a heating rate of 3 ° C / min for 8 hours of pre-sintering in an air atmosphere, and then the temperature was raised to 940 ° C at a heating rate of 3 ° C / min for 16 hours in an air atmosphere. After sintering, the furnace was cooled and the matrix material Na was obtained. 0.98 Ni 0.33 Fe 0.2 Mn 0.42 Ti 0.05 O2, crush the material through a roller mill / air flow crusher, sieve through 300 mesh, and set aside.

[0173] The matrix material Na 0.98 Ni 0.33 Fe 0.2 Mn0.42 Ti 0.05 CaCO3 and WO3 with a particle size of 30-200nm are added to O2, and the added amounts are 0.5%wt and 0.1%wt of the matrix material respectively. ZrO2 with a mass percentage of 0.06wt% of the matrix material and Al2O3 with a mass percentage of 0.08wt% of the matrix material are also added. After mixing evenly, the mixture is calcined at 750℃ for 7h to obtain a second calcined product.

[0174] 30-200 nm LiF was added to the second calcined product in an amount of 0.3% of the mass percentage of the second calcined product, mixed evenly and calcined at 590 ° C for 5 h to finally obtain a secondary coated sodium cathode material, which is a single crystal material with Dv50 = 4.28 μm and BET of 0.52 m 2 / g.

[0175] This embodiment also provides a sodium ion battery, whose raw materials include the above-mentioned positive electrode material, binder, polyacrylonitrile copolymer, and carbon nanotubes in a ratio of 95.5%:1.5%:2%:1% to make a positive electrode slurry, which is coated on aluminum foil to make a positive electrode sheet. The negative electrode sheet uses a hard carbon negative electrode material. The electrolyte includes an organic solvent and a sodium salt. Propylene carbonate, ethylene carbonate, and dimethyl carbonate are uniformly mixed in an inert atmosphere at a mass ratio of 1:1:1, and then sodium hexafluorophosphate is dissolved in the mixed solvent to prepare a 1 mol / L electrolyte. A polyethylene film or a polyethylene plus ceramic coating film is used as a separator. The remaining steps are assembled into a sodium ion battery according to conventional methods, and corresponding electrical performance tests are performed.

[0176] Example 9

[0177] This embodiment provides a positive electrode active material for a sodium ion battery, and the specific preparation method is as follows:

[0178] Nickel sulfate, manganese sulfate, and ferric sulfate solutions were mixed evenly in a molar ratio of Ni:Fe:Mn = 33:30:37, and 2 mol / L ammonia and sodium hydroxide solution were added to the solution for neutralization. Co-precipitation reaction was carried out under a nitrogen atmosphere with a purity of 99.5% to obtain the hydroxide precursor Ni 0.33 Fe 0.3 Mn 0.37 (OH)2, the obtained precipitate was filtered and washed, and dried at 150°C for 5h to obtain a dried product.

[0179] The hydroxide precursor Ni 0.33 Fe 0.3 Mn 0.37(OH)2 and sodium carbonate were weighed according to the molar ratio of metal cations to Na ions in the precursor of 1:1.05, and the two substances were mixed evenly, and then sintered in stages in a sintering furnace: first, the temperature was raised to 400 ° C at a heating rate of 3 ° C / min for 8 hours of pre-sintering in an air atmosphere, and then the temperature was raised to 940 ° C at a heating rate of 3 ° C / min for 16 hours in an air atmosphere. After sintering, the furnace was cooled and the matrix material Na was obtained. 0.98 Ni 0.33 Fe 0.3 Mn 0.37 O2, crush the material through a roller mill / air flow crusher, sieve through 300 mesh, and set aside.

[0180] The matrix material Na 0.98 Ni 0.33 Fe 0.3 Mn 0.37 CaCO3 with a particle size of 30-200 nm was added to O2 in an amount of 0.3% wt of the mass percentage of the matrix material. After mixing evenly, the mixture was calcined at 750° C. for 7 h to obtain a second calcined product.

[0181] 30-200 nm LiF was added to the second calcined product in an amount of 0.15% of the mass percentage of the second calcined product, mixed evenly and calcined at 590 ° C for 5 h to finally obtain a secondary coated sodium cathode material, which is a single crystal material with Dv50 = 4.2 μm and BET of 0.45 m 2 / g.

[0182] This embodiment also provides a sodium ion battery, whose raw materials include the above-mentioned positive electrode material, binder, polyacrylonitrile copolymer, and carbon nanotubes in a ratio of 95.5%:1.5%:2%:1% to make a positive electrode slurry, which is coated on aluminum foil to make a positive electrode sheet. The negative electrode sheet uses a hard carbon negative electrode material. The electrolyte includes an organic solvent and a sodium salt. Propylene carbonate, ethylene carbonate, and dimethyl carbonate are uniformly mixed in an inert atmosphere at a mass ratio of 1:1:1, and then sodium hexafluorophosphate is dissolved in the mixed solvent to prepare a 1 mol / L electrolyte. A polyethylene film or a polyethylene plus ceramic coating film is used as a separator. The remaining steps are assembled into a sodium ion battery according to conventional methods, and corresponding electrical performance tests are performed.

[0183] Example 10

[0184] This embodiment provides a positive electrode active material for a sodium ion battery, and the specific preparation method is as follows:

[0185] Nickel sulfate, manganese sulfate, and ferric sulfate solutions were mixed evenly in a molar ratio of Ni:Fe:Mn = 33:30:37, and 2 mol / L ammonia and sodium hydroxide solution were added to the solution for neutralization. Co-precipitation reaction was carried out under a nitrogen atmosphere with a purity of 99.5% to obtain the hydroxide precursor Ni 0.33 Fe 0.3 Mn 0.37 (OH)2, the obtained precipitate was filtered and washed, and dried at 150°C for 5h to obtain a dried product.

[0186] The hydroxide precursor Ni 0.33 Fe 0.3 Mn 0.37 (OH)2 and sodium carbonate were weighed according to the molar ratio of metal cations to Na ions in the precursor of 1:1.05, and the two substances were mixed evenly, and then sintered in stages in a sintering furnace: first, the temperature was raised to 400 ° C at a heating rate of 3 ° C / min for 8 hours of pre-sintering in an air atmosphere, and then the temperature was raised to 940 ° C at a heating rate of 3 ° C / min for 16 hours in an air atmosphere. After sintering, the furnace was cooled and the matrix material Na was obtained. 0.98 Ni 0.33 Fe 0.3 Mn 0.37 O2, crush the material through a roller mill / air flow crusher, sieve through 300 mesh, and set aside.

[0187] The matrix material Na 0.98 Ni 0.33 Fe 0.3 Mn 0.37 Al2O3 with a particle size of 30-200 nm was added to O2 in an amount of 0.15% wt of the mass percentage of the matrix material. After mixing evenly, the mixture was calcined at 750°C for 7 hours to obtain a second calcined product.

[0188] 30-200 nm LiF was added to the second calcined product in an amount of 0.15% of the mass percentage of the second calcined product, mixed evenly and calcined at 590 ° C for 5 h to finally obtain a secondary coated sodium positive electrode material, which is a single crystal material with Dv50 = 3.48 μm and BET of 0.528 m 2 / g.

[0189] This embodiment also provides a sodium ion battery, whose raw materials include the above-mentioned positive electrode material, binder, polyacrylonitrile copolymer, and carbon nanotubes in a ratio of 95.5%:1.5%:2%:1% to make a positive electrode slurry, which is coated on aluminum foil to make a positive electrode sheet. The negative electrode sheet uses a hard carbon negative electrode material. The electrolyte includes an organic solvent and a sodium salt. Propylene carbonate, ethylene carbonate, and dimethyl carbonate are uniformly mixed in an inert atmosphere at a mass ratio of 1:1:1, and then sodium hexafluorophosphate is dissolved in the mixed solvent to prepare a 1 mol / L electrolyte. A polyethylene film or a polyethylene plus ceramic coating film is used as a separator. The remaining steps are assembled into a sodium ion battery according to conventional methods, and corresponding electrical performance tests are performed.

[0190] Comparative Example 1

[0191] This comparative example provides a sodium ion battery positive electrode active material, and the specific preparation method is as follows:

[0192] Nickel sulfate, manganese sulfate, and ferric sulfate solutions were mixed evenly in a molar ratio of Ni:Fe:Mn = 33:30:37, and 2 mol / L ammonia and sodium hydroxide solution were added to the solution for neutralization. Co-precipitation reaction was carried out under a nitrogen atmosphere with a purity of 99.5% to obtain the hydroxide precursor Ni 0.33 Fe 0.3 Mn 0.37 (OH)2, the obtained precipitate was filtered and washed, and dried at 150°C for 5h to obtain a dried product.

[0193] The hydroxide precursor Ni 0.33 Fe 0.3 Mn 0.37 (OH)2 and sodium carbonate were weighed according to the molar ratio of metal cations to Na ions in the precursor of 1:1.05, and the two substances were mixed evenly, and then sintered in stages in a sintering furnace: first, the temperature was raised to 400 ° C at a heating rate of 3 ° C / min for 8 hours of pre-sintering in an air atmosphere, and then the temperature was raised to 940 ° C at a heating rate of 3 ° C / min for 16 hours in an air atmosphere. After sintering, the furnace was cooled and the matrix material Na was obtained. 0.98 Ni 0.33 Fe 0.3 Mn 0.37 O2, the material was crushed by roller mill / air flow crusher, sieved through 300 mesh, and single crystal material was obtained, Dv50 = 4.58 μm, BET was 0.489 m 2 / g.

[0194] This comparative example also provides a sodium ion battery, the raw materials of which include the above-mentioned positive electrode material, binder, polyacrylonitrile copolymer, and carbon nanotubes in a ratio of 95.5%:1.5%:2%:1% to make a positive electrode slurry, which is coated on aluminum foil to make a positive electrode sheet. The negative electrode sheet uses a hard carbon negative electrode material. The electrolyte includes an organic solvent and a sodium salt. Propylene carbonate, ethylene carbonate, and dimethyl carbonate are uniformly mixed in an inert atmosphere at a mass ratio of 1:1:1, and then sodium salt sodium hexafluorophosphate is dissolved in the mixed solvent to prepare a 1 mol / L electrolyte; and a polyethylene film or a polyethylene plus ceramic coating film is used as a diaphragm. The remaining steps are assembled into a sodium ion battery according to conventional methods, and the corresponding electrical performance tests are carried out.

[0195] Comparative Example 2

[0196] This comparative example provides a sodium ion battery positive electrode active material, and the specific preparation method is as follows:

[0197] Nickel sulfate, manganese sulfate, and ferric sulfate solutions were mixed evenly in a molar ratio of Ni:Fe:Mn = 33:30:37, and 2 mol / L ammonia and sodium hydroxide solution were added to the solution for neutralization. Co-precipitation reaction was carried out under a nitrogen atmosphere with a purity of 99.5% to obtain the hydroxide precursor Ni 0.33 Fe 0.3 Mn 0.37 (OH)2, the obtained precipitate was filtered and washed, and dried at 150°C for 5h to obtain a dried product.

[0198] The hydroxide precursor Ni 0.33 Fe 0.3 Mn 0.37 (OH)2 and sodium carbonate were weighed according to the molar ratio of metal cations to Na ions in the precursor of 1:1.05, and the two substances were mixed evenly, and then sintered in stages in a sintering furnace: first, the temperature was raised to 400 ° C at a heating rate of 3 ° C / min for 8 hours of pre-sintering in an air atmosphere, and then the temperature was raised to 940 ° C at a heating rate of 3 ° C / min for 16 hours in an air atmosphere. After sintering, the furnace was cooled and the matrix material Na was obtained. 0.98 Ni 0.33 Fe 0.3 Mn 0.37 O2, crush the material through a roller mill / air flow crusher, sieve through 300 mesh, and set aside.

[0199] The matrix material Na 0.98 Ni 0.33 Fe 0.3 Mn 0.37CaCO3 and WO3 with particle sizes of 30-200 nm were added to O2 in amounts of 0.3% wt and 0.1% wt of the matrix material, respectively. After mixing evenly, the mixture was calcined at 750 ° C for 7 h to obtain a single crystal material with Dv50 = 4.1 μm and BET of 0.5 m 2 / g.

[0200] This comparative example also provides a sodium ion battery, the raw materials of which include the above-mentioned positive electrode material, binder, polyacrylonitrile copolymer, and carbon nanotubes in a ratio of 95.5%:1.5%:2%:1% to make a positive electrode slurry, which is coated on aluminum foil to make a positive electrode sheet. The negative electrode sheet uses a hard carbon negative electrode material. The electrolyte includes an organic solvent and a sodium salt. Propylene carbonate, ethylene carbonate, and dimethyl carbonate are uniformly mixed in an inert atmosphere at a mass ratio of 1:1:1, and then sodium salt sodium hexafluorophosphate is dissolved in the mixed solvent to prepare a 1 mol / L electrolyte; and a polyethylene film or a polyethylene plus ceramic coating film is used as a diaphragm. The remaining steps are assembled into a sodium ion battery according to conventional methods, and the corresponding electrical performance tests are carried out.

[0201] Comparative Example 3

[0202] This comparative example provides a sodium ion battery positive electrode active material, and the specific preparation method is as follows:

[0203] Nickel sulfate, manganese sulfate, iron sulfate and zinc sulfate solutions were mixed evenly in a molar ratio of Ni:Fe:Mn = 33:30:37, 2 mol / L ammonia water and sodium hydroxide solution were added to the solution for neutralization, and a coprecipitation reaction was carried out under a nitrogen atmosphere with a purity of 99.5% to obtain the hydroxide precursor Ni 0.33 Fe 0.3 Mn 0.37 (OH)2, the obtained precipitate was filtered and washed, and dried at 150°C for 5h to obtain a dried product.

[0204] The hydroxide precursor Ni 0.33 Fe 0.3 Mn 0.37 (OH)2 and sodium carbonate were weighed according to the molar ratio of metal cations to Na ions in the precursor of 1:1.05, and the two substances were mixed evenly, and then sintered in stages in a sintering furnace: first, the temperature was raised to 400 ° C at a heating rate of 3 ° C / min for 8 hours of pre-sintering in an air atmosphere, and then the temperature was raised to 940 ° C at a heating rate of 3 ° C / min for 16 hours in an air atmosphere. After sintering, the furnace was cooled and the matrix material Na was obtained. 0.98 Ni 0.33 Fe 0.3 Mn 0.37O2, crush the material through a roller mill / air flow crusher, sieve through 300 mesh, and set aside.

[0205] The matrix material Na 0.98 Ni 0.33 Fe 0.3 Mn 0.37 LiF with a particle size of 30-200 nm was added to O2, and the addition amount was 0.1 wt% of the mass percentage of the first calcined product. After mixing evenly, it was calcined at 590 ° C for 5 h to finally obtain a single-crystal sodium positive electrode material with Dv50 = 4.04 μm and BET of 0.49 m 2 / g.

[0206] This comparative example also provides a sodium ion battery, the raw materials of which include the above-mentioned positive electrode material, binder, polyacrylonitrile copolymer, and carbon nanotubes in a ratio of 95.5%:1.5%:2%:1% to make a positive electrode slurry, which is coated on aluminum foil to make a positive electrode sheet. The negative electrode sheet uses a hard carbon negative electrode material. The electrolyte includes an organic solvent and a sodium salt. Propylene carbonate, ethylene carbonate, and dimethyl carbonate are uniformly mixed in an inert atmosphere at a mass ratio of 1:1:1, and then sodium salt sodium hexafluorophosphate is dissolved in the mixed solvent to prepare a 1 mol / L electrolyte; and a polyethylene film or a polyethylene plus ceramic coating film is used as a diaphragm. The remaining steps are assembled into a sodium ion battery according to conventional methods, and the corresponding electrical performance tests are carried out.

[0207] Comparative Example 4

[0208] This comparative example provides a sodium ion battery positive electrode active material, and the specific preparation method is as follows:

[0209] Nickel sulfate, manganese sulfate, and ferric sulfate solutions were mixed evenly in a molar ratio of Ni:Fe:Mn = 33:30:37, and 2 mol / L ammonia and sodium hydroxide solution were added to the solution for neutralization. Co-precipitation reaction was carried out under a nitrogen atmosphere with a purity of 99.5% to obtain the hydroxide precursor Ni 0.33 Fe 0.3 Mn 0.37 (OH)2, the obtained precipitate was filtered and washed, and dried at 150°C for 5h to obtain a dried product.

[0210] The hydroxide precursor Ni 0.33 Fe 0.3 Mn 0.37(OH)2 and sodium carbonate were weighed according to the molar ratio of metal cations to Na ions in the precursor of 1:1.05, and the two substances were mixed evenly, and then sintered in stages in a sintering furnace: first, the temperature was raised to 400 ° C at a heating rate of 3 ° C / min for 8 hours of pre-sintering in an air atmosphere, and then the temperature was raised to 940 ° C at a heating rate of 3 ° C / min for 16 hours in an air atmosphere. After sintering, the furnace was cooled and the matrix material Na was obtained. 0.98 Ni 0.33 Fe 0.3 Mn 0.37 O2, crush the material through a roller mill / air flow crusher, sieve through 300 mesh, and set aside.

[0211] The matrix material Na 0.98 Ni 0.33 Fe 0.3 Mn 0.37 MgO and WO3 with a particle size of 30-200 nm were added to O2 in amounts of 0.3% wt and 0.1% wt of the matrix material, respectively. After mixing evenly, the mixture was calcined at 750° C. for 7 h to obtain a second calcined product.

[0212] 30-200 nm LiF was added to the second calcined product in an amount of 0.15% of the mass percentage of the second calcined product, mixed evenly and calcined at 590 ° C for 5 h to finally obtain a secondary coated sodium positive electrode material, which is a single crystal material with Dv50 = 3.65 μm and BET of 0.482 m 2 / g.

[0213] This comparative example also provides a sodium ion battery, the raw materials of which include the above-mentioned positive electrode material, binder, polyacrylonitrile copolymer, and carbon nanotubes in a ratio of 95.5%:1.5%:2%:1% to make a positive electrode slurry, which is coated on aluminum foil to make a positive electrode sheet. The negative electrode sheet uses a hard carbon negative electrode material. The electrolyte includes an organic solvent and a sodium salt. Propylene carbonate, ethylene carbonate, and dimethyl carbonate are uniformly mixed in an inert atmosphere at a mass ratio of 1:1:1, and then sodium salt sodium hexafluorophosphate is dissolved in the mixed solvent to prepare a 1 mol / L electrolyte; and a polyethylene film or a polyethylene plus ceramic coating film is used as a diaphragm. The remaining steps are assembled into a sodium ion battery according to conventional methods, and the corresponding electrical performance tests are carried out.

[0214] The performance of the sodium ion batteries prepared in the examples and comparative examples of the present application is shown in Table 1:

[0215] Table 1 Performance of sodium ion batteries obtained in Examples and Comparative Examples

[0216]

[0217] As can be seen from Table 1, the present invention compares each embodiment with comparative examples 1-3 by using O3 structure Na a Ni x Fe y Mn z M 1-x-y-z The double-layer coating on the surface of the O2 positive electrode material has a good first discharge specific capacity and a low initial DCR value. This is mainly because the surface diffusion rate of sodium ions is increased by anion doping, while the internal interface coating layer of W and Ca reduces the contact area between the electrolyte and the interior of the positive electrode material, thereby slowing down the occurrence of side reactions. The XRD spectra of the positive electrode materials of Example 1 and Comparative Example 2 after 1000 cycles are shown in Figure 2. Figure 3 As shown, Figure 3 The XRD spectrum of the local magnification in the range of 16-17 is as follows Figure 4 As shown, compared with the 003 peak position in the XRD spectrum, the overall offset angle difference of the embodiment is ≤0.12, indicating that the double-layer coating effectively enhances the stability of the material crystal structure. Since the comparative example does not have a sophisticated coating design, the first discharge specific capacity and cycle capacity retention rate in the high voltage window are worse than those of the embodiment.

[0218] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

[0219] Furthermore, those skilled in the art will appreciate that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and to form distinct embodiments. For example, in the claims above, any of the claimed embodiments may be used in any combination. The information disclosed in this background section is intended solely to enhance understanding of the overall background of this application and should not be construed as an admission or any implication that such information constitutes prior art known to those skilled in the art.

Claims

1. A positive electrode active material for a sodium ion battery, characterized in that The sodium ion battery positive electrode active material includes a base material and a coating layer, wherein the coating layer is coated on the base material; The chemical formula of the matrix material is Na a Ni x Fe y Mn z M 1-x-y-z O2, wherein 1.05≥a≥0.8, 1.0≥x>0, 1.0≥y>0, 1.0≥z>0, 1.0>1-xzy≥0; wherein the M element includes at least one of Cu, Zn, and Ti; The coating layer includes a first coating layer and a second coating layer, wherein the second coating layer is coated on the first coating layer; the first coating element in the first coating layer includes at least one of Ca, W, and Al; and the second coating element in the second coating layer includes F.

2. The sodium ion battery positive electrode active material according to claim 1, characterized in that The thickness of the first coating layer is 0.5-20 nm; the thickness of the second coating layer is 0.1-5 nm.

3. The sodium ion battery positive electrode active material according to claim 1 or 2, characterized in that The angle difference of the 003 characteristic peak of the sodium ion battery positive electrode active material is △≤0.2θ.

4. A method for preparing a positive electrode active material for a sodium ion battery according to any one of claims 1 to 3, characterized in that: include: A nickel source, a manganese source, an iron source and a solution of the M element are mixed and then added into an alkaline solution for neutralization, and a coprecipitation reaction is carried out under an inert gas atmosphere to obtain a hydroxide precursor; The hydroxide precursor is mixed with a sodium source and then subjected to a first calcination, and a first calcined product is obtained after cooling; mixing the first calcined product with a first coating element source and then performing a second calcination, and cooling to obtain a second calcined product; The second calcined product is mixed with the second coating element source and then subjected to a third calcination, and the sodium ion battery positive electrode active material is obtained after cooling.

5. The method for preparing a positive electrode active material for a sodium ion battery according to claim 4, wherein: At least one of the following conditions is met: a. The chemical formula of the hydroxide precursor is Ni x Fe y Mn z M 1-x-y-z (OH)2; where 1.0≥x>0, 1.0≥y>0, 1.0≥z>0, 1.0>1-xzy≥0; b. The first calcined product is the matrix material; c. The second calcined product is a sodium ion battery positive electrode material co-coated with the first coating element.

6. The method for preparing a positive electrode active material for a sodium ion battery according to claim 4, wherein: The coprecipitation reaction conditions meet at least one of the following conditions: d. The nickel source comprises nickel sulfate, the manganese source comprises manganese sulfate, and the iron source comprises iron sulfate; e. The molar ratio of the nickel source, the manganese source, the iron source and the M element when mixed is x:y:z:1-xyz; wherein, 1.0≥x>0, 1.0≥y>0, 1.0≥z>0, 1.0>1-xzy≥0; f. The alkaline solution comprises aqueous ammonia and sodium hydroxide; g. The inert gas includes nitrogen, the purity of the nitrogen is not less than 99.5%; h. The reaction conditions of the coprecipitation reaction are: temperature 50-80°C, pH value of the reaction system during the reaction is 10.5-11.

9.

7. The method for preparing a positive electrode active material for a sodium ion battery according to claim 4, wherein: The first calcination satisfies at least one of the following conditions: i. The molar ratio of the metal cation in the hydroxide precursor to the sodium ion in the sodium source is 1:n; wherein 0.95≤n≤1.15; j. The first calcination is a multi-stage calcination, including: raising the temperature to 400-550°C at a heating rate of 0.5-10°C / min for pre-sintering for 4-8h, then raising the temperature to 800-1100°C at a heating rate of 0.5-10°C / min for sintering for 10-24h, and cooling to room temperature with the furnace after sintering.

8. The method for preparing a positive electrode active material for a sodium ion battery according to claim 4, wherein: The second calcination satisfies at least one of the following conditions: k. The first coating element source includes a Ca source, a W source, and an Al source of nano-sized particles; the Ca source is added in an amount of 0.05-1wt% by mass of the first calcined product, the W source is added in an amount of 0.05-0.7wt% by mass of the first calcined product; the Al source is added in an amount of 0.05-0.95wt% by mass of the first calcined product; l. The second calcination comprises: heating to 650-800°C at a rate of 3°C / min and calcining at this temperature for 5-10h, and cooling to room temperature with the furnace.

9. The method for preparing a positive electrode active material for a sodium ion battery according to any one of claims 4 to 8, wherein: The third calcination satisfies at least one of the following conditions: m. The second coating element source includes lithium fluoride; n. The amount of the second coating element source added is 0.05-1.5wt% of the mass of the second calcined product; o. The third calcination comprises: heating to 450-650°C at a rate of 3°C / min and calcining at this temperature for 5-10h, and cooling to room temperature with the furnace.

10. A sodium ion battery, characterized in that: The raw materials include the sodium ion battery positive electrode active material according to any one of claims 1 to 3, and meet at least one of the following conditions: A. The positive electrode sheet includes a positive electrode current collector and a positive electrode material layer; The positive electrode current collector comprises one of copper foil, aluminum foil, titanium foil, nickel foil, iron foil and zinc foil; The raw material of the positive electrode material layer is a positive electrode slurry, and the raw materials of the positive electrode slurry include the positive electrode active material of the sodium ion battery, a first conductive agent, a first binder, and a first solvent; The first conductive agent includes at least one of conductive carbon black, carbon fiber, acetylene black, Ketjen black, graphene, and carbon nanotubes; The first binder includes at least one of a fluorine-containing resin, a polypropylene resin, a fiber-type binder, and a polyimide-type binder; The first solvent includes N-methylpyrrolidone; Taking the total mass of the positive electrode material layer as 100%, the positive electrode material layer comprises 95-98% of the sodium ion battery positive electrode active material, 1-3% of the first conductive agent, and 1-2% of the first binder; B. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer; The negative electrode current collector includes copper foil; The raw material of the negative electrode active material layer is a negative electrode slurry, and the raw materials of the negative electrode slurry include: a negative electrode active material, a second conductive agent, a second binder, and a second solvent; The negative electrode active material includes at least one of graphite, silicon-carbon negative electrode, hard carbon and sodium titanate; The second conductive agent comprises at least one of electric carbon black, carbon fiber, acetylene black, Ketjen black, graphene and carbon nanotubes; The second binder includes at least one of a fluorine-containing resin, a polypropylene resin, a fiber-type binder, a rubber-type binder, and a polyimide-type binder; The second solvent includes deionized water; The negative electrode active material layer comprises, based on the total mass of the negative electrode active material layer being 100%, 93-98% of the negative electrode active material, 1-3% of the second conductive agent, and 1-4% of the second binder; C. Calculated based on the total mass of the electrolyte as 100%, including electrolyte solvent 70-85%, sodium salt 10-15%, and additives 5-15%; The solvent includes one of propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), 1,2-dimethoxyethane (DME) and triethyl phosphate (TEP); the sodium salt includes one of NaDFOB, NaTFSI, NaPF6, NaClO4, NaFSI and NaBF4; the additive includes at least one of FEC, VC, PDO, PTS, DTD, TMSPi, NaFSI and NaDFOB; D. The diaphragm includes a single-layer polymer diaphragm, a multi-layer polymer diaphragm, a ceramic diaphragm, or a polymer-ceramic composite diaphragm.

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