Positive electrode material, preparation method, positive electrode sheet, and sodium-ion battery

Abstract

The present invention relates to the technical field of batteries, and in particular to a positive electrode material, a preparation method, a positive electrode sheet, and a sodium-ion battery. The positive electrode material comprises cation-doped sodium iron sulfate and a carbon material, and the chemical formula of the cation-doped sodium iron sulfate is NaxAyFe1-zBz(SO4)m, wherein 1.1≤x+y≤1.7, 0≤y≤0.17, 0≤z≤0.1, y and z are not 0 at the same time, and x, y, z and m comply with charge balance; A is K+, B is selected from one or more of Mn2+, Ni2+, Co2+, Cu2+, Ca2+, Mg2+, Ba2+, and Zn2+. The present application improves the quality and consistency of positive electrode material products, improves the electrochemical sodium storage performance of positive electrode materials, improves the cycle performance and the rate performance of the positive electrode materials, ensures the large-scale mass production of the materials, and improves the production efficiency of finished materials, thereby reducing costs.

Description

A positive electrode material, preparation method, positive electrode sheet and sodium ion battery Technical Field

[0001] The present invention belongs to the technical field of batteries, and in particular relates to a positive electrode material, a preparation method, a positive electrode plate and a sodium ion battery. Background Art

[0002] Currently, in the preparation process of battery positive electrode materials, a high-energy planetary ball milling synthesis process is generally used to process the preparation raw materials to obtain composite positive electrode materials. Specifically, the preparation raw materials are placed in a ball mill according to a certain ratio, a certain ball-to-material ratio and planetary ball milling parameters are set, the precursor material is processed, and then sintered under an inert atmosphere to prepare the composite positive electrode material. However, when using the high-energy planetary ball milling synthesis process to process the preparation raw materials, due to the differences in physical and chemical properties such as the material, hardness, density and original particle size of the various preparation raw material components, the components are crushed to different degrees during the high-energy planetary ball milling process, easily stratified or locally agglomerated, resulting in uneven mixing of the prepared precursor materials. The material formed after sintering has poor consistency and cannot form atomic-level uniformity. It is easy to form inactive impurity phases, resulting in poor cycle performance and poor rate performance of the prepared positive electrode material. In addition, the planetary high-energy ball milling preparation technology requires a high ball-to-material ratio, and most of the energy is lost in the form of heat due to the interaction between the balls and the jar, resulting in extremely low production efficiency of the finished material and high production energy consumption.

[0003] Therefore, it is necessary to provide a new type of positive electrode material and its preparation scheme to improve the quality and consistency of positive electrode material products, improve the electrochemical sodium storage performance of positive electrode materials, improve the cycle performance and rate performance of positive electrode materials, ensure large-scale mass production of materials, improve the production efficiency of finished materials, and reduce costs.

[0004] Summary of the Invention

[0005] In view of the above problems of the prior art, the present application provides a positive electrode material, comprising cation-doped sodium ferric sulfate and a carbon material, wherein the carbon material in situ modifies the cation-doped sodium ferric sulfate, and the general formula of the cation-doped sodium ferric sulfate (NFS) is Na x A y Fe 1-z B z (SO4) m ;

[0006] Where 1.1≤x+y≤1.7, 0≤y≤0.17, 0≤z≤0.1, y and z are not 0 at the same time and x, y, z and m are in charge balance; A is K + , B is selected from Mn 2+ 、Ni 2+ 、Co2+ 、Cu 2+ , Ca 2+ Mg 2+ 、Ba 2+ and Zn 2+ One or more of the .

[0007] Furthermore, the carbon source of the carbon material is selected from carbon nanotubes, carbon fibers, graphene, reduced graphene oxide, conductive carbon black or MXene.

[0008] Furthermore, the mass fraction of the carbon material is 0.1-10 wt%.

[0009] Furthermore, the positive electrode material is prepared by the following steps:

[0010] S11: mixing the sulfate of A and / or B with Na2SO4, FeSO4 and a carbon source to obtain a precursor material;

[0011] S12: performing pressing and sintering on the precursor material to obtain the positive electrode material.

[0012] Furthermore, in step S11, the mixing treatment method includes at least one of air flow milling and vibration milling.

[0013] Furthermore, in step S12, the pressure of the pressing treatment is 0.01-2 GPa, and the pressing time is 0.1-60 min.

[0014] Furthermore, the sintering temperature is 300-400° C., the sintering time is 0.1-72 hours, and the sintering atmosphere is an inert atmosphere.

[0015] The present application also provides a positive electrode plate, comprising a positive electrode active material layer, wherein the positive electrode active material layer comprises the above-mentioned positive electrode material.

[0016] The present application also provides a sodium ion battery, comprising the above-mentioned positive electrode plate.

[0017] Furthermore, the sodium ion battery is a button battery, a soft pack battery, a cylindrical battery or a square battery.

[0018] Due to the above technical solution, the present application provides a positive electrode material, preparation method, positive electrode plate and sodium ion battery, which have the following beneficial effects: the present application adds cation-doped sodium ferric sulfate and carbon material to the positive electrode material, performs intra-lattice cation doping on the sodium ferric sulfate and modifies the carbon material. The in-situ cation doping can improve the crystal structure stability of the sodium ferric sulfate active material, and at the same time, in conjunction with the co-modification with the carbon material, improves the electronic conductivity and sodium ion diffusion rate of the sodium ferric sulfate material and the stability of its crystal structure, thereby improving the quality and consistency of the positive electrode material product, improving the electrochemical sodium storage performance of the positive electrode material, and the long-cycle stability and high-rate performance of the positive electrode material during the electrochemical sodium storage process, ensuring large-scale mass production of the material, improving the production efficiency of the finished material, and reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the present application or the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0020] FIG1 is a 1C cycle diagram of NFS doping Examples 1-8 and Comparative Example 1.

[0021] FIG2 is a 2C cycle diagram of NFS doping Examples 1-8 and Comparative Example 1.

[0022] FIG3 is a graph showing the rate performance of NFS-doped Examples 2, 4-8 and Comparative Example 1.

[0023] FIG4 is the XRD patterns of NFS-doped Examples 1, 2, 3, 4, 8 and Comparative Example 1.

[0024] FIG5 is the XRD patterns of NFS-doped Examples 5, 6, 7, and 9.

[0025] FIG6 is a 1C cycle diagram of Examples 2, 10, 11 and 12 doped with (Zn) at different sodium to iron ratios.

[0026] FIG7 is a 2C cycle diagram of Examples 2, 10, 11 and 12 doped with (Zn) at different sodium to iron ratios.

[0027] FIG8 is the XRD patterns of Examples 2, 10, 11 and 12 doped with (Zn) at different sodium to iron ratios.

[0028] FIG9 is a 1C cycle diagram of NFS doped with different percentages of Zn in Examples 2, 13, 14 and 15.

[0029] FIG10 is a 2C cycle diagram of NFS doped with different percentages of Zn in Examples 2, 13, 14 and 15.

[0030] FIG11 is the XRD patterns of NFS doped with Zn in Examples 2, 13, 14 and 15 with different percentage contents.

[0031] FIG12 is a 2C cycle diagram of NFS-doped Examples 11 and 16 and Comparative Example 2.

[0032] FIG13 is the XRD patterns of NFS-doped Examples 11 and 16 and Comparative Example 2.

[0033] FIG14 is a graph showing the rate performance of NFS multi-element doping embodiments 2, 17, 18, and 19.

[0034] Figure 15 is a graph showing the first cycle data of the full battery soft pack at 0.1C in Example 21. DETAILED DESCRIPTION

[0035] The following will be combined with the accompanying drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0036] For the following defined terms, these definitions shall apply unless a different definition is given in the claims or elsewhere in this specification. All numerical values, whether or not explicitly indicated, are defined herein as being modified by the term "about". The term "about" generally refers to a numerical range that one of ordinary skill in the art would consider equivalent to the stated value to produce substantially the same properties, functions, results, etc. A numerical range indicated by a lower value and an upper value is defined to include all numerical values ​​included in the numerical range and all subranges included in the numerical range.

[0037] It should be noted that the terms "include" and "have" in the specification and claims of this application and the above drawings, as well as any variations thereof, are intended to cover non-exclusive inclusions.

[0038] The following describes a positive electrode material provided by the present application, with reference to Figures 1-15. It includes cation-doped sodium ferric sulfate and a carbon material, wherein the carbon material in situ modifies the cation-doped sodium ferric sulfate. The general formula of the cation-doped sodium ferric sulfate is Na x A y Fe 1-z B z (SO4) m; Among them, 1.1≤x+y≤1.7, 0≤y≤0.17, 0≤z≤0.1, y and z are not 0 at the same time and x, y, z and m are in charge balance; A is K + , B is selected from Mn 2+ 、Ni 2+ 、Co 2+ 、Cu 2+ , Ca 2+ Mg 2+ 、Ba 2+ and Zn 2+ It should be noted that x, y, z and m are in charge balance, that is, m=(x+y+2) / 2.

[0039] The present application adds cation-doped sodium ferric sulfate and carbon material to the positive electrode material, performs intra-lattice cation doping on the sodium ferric sulfate and modifies the carbon material. The in-situ cation doping can improve the crystal structure stability of the sodium ferric sulfate active material. At the same time, the co-modification with the carbon material improves the electronic conductivity and sodium ion diffusion rate of the sodium ferric sulfate material and the stability of its crystal structure, thereby improving the quality and consistency of the positive electrode material product, improving the electrochemical sodium storage performance of the positive electrode material, and the long-cycle stability and high-rate performance of the positive electrode material during the electrochemical sodium storage process, ensuring large-scale mass production of the material, improving the production efficiency of the finished material, and reducing costs.

[0040] In some embodiments, the carbon source of the carbon material is selected from carbon nanotubes (CNTs), carbon fibers, graphene, reduced graphene oxide, conductive carbon black, or MXene (a two-dimensional inorganic compound).

[0041] Specifically, carbon nanotubes (CNTs) are tubular nanoscale graphite crystals, which are seamless nanoscale tubes formed by curling single or multilayer graphite sheets around a central axis at a certain spiral angle. The carbon in each layer is sp2 hybridized, forming a hexagonal cylindrical surface.

[0042] In some embodiments, the mass fraction of the carbon material is 0.1-10 wt %, that is, the carbon material accounts for 0.1-10% of the mass of the positive electrode material.

[0043] In other embodiments, the mass fraction of the carbon material is 4-10 wt%.

[0044] In other embodiments, the mass fraction of the carbon material is 2-8 wt %.

[0045] The surface modification of the carbon-based wrapping material facilitates a stable connection between the carbon-based wrapping material and the active sodium ferric sulfate material, thereby improving the uniformity of the surface coating of the sodium ferric sulfate. Furthermore, the modified carbon-based wrapping material not only achieves surface modification but also stabilizes the microporous channels within the carbon-based wrapping material, greatly enhancing the effect of the modified microporous channels and thus improving the electrochemical sodium storage performance of the positive electrode material.

[0046] In some embodiments, y=0 and 0<z≤0.1, in the absence of K + In the case of doping, at least one B material is doped in situ.

[0047] In some embodiments, 0<y≤0.17 and 0<z≤0.1, in K + If present, it also includes in-situ doping of at least one B material.

[0048] In this way, by doping at least one B material with iron, the structure can be stabilized, the intrinsic conductivity of the material can be improved, the interlayer spacing can be increased, and the kinetics can be improved, which is beneficial to the Na + Deintercalation and intercalation can improve the capacity retention rate, and doping with more active metal ions such as Co and Ni can increase the discharge capacity of the material.

[0049] In some embodiments, 1.3≤x+y≤1.7. By controlling the ratio of monovalent positive ions in the material to the above range, the structural stability, material activity, and electrical conductivity of the material are optimized, thereby improving the electrical performance of the battery. Preferably, 1.3≤x+y≤1.5.

[0050] In some embodiments, the ratio of the sum of the contents of Na and A to the sum of the contents of Fe and B is greater than or equal to 1.1 and less than or equal to 1.7. By controlling the content ratio of monovalent elements to divalent elements in the material, and combining it with the proportion of monovalent positive ions, the electrical properties of the material can be further improved. Preferably, the ratio of the sum of the contents of Na and A to the sum of the contents of Fe and B is greater than or equal to 1.3 and less than or equal to 1.5.

[0051] In some embodiments, the positive electrode material is prepared by the following steps:

[0052] S11: mixing the sulfate of A and / or B with Na2SO4, FeSO4 and a carbon source to obtain a precursor material;

[0053] S12: performing pressing and sintering on the precursor material to obtain a positive electrode material.

[0054] In some embodiments, the sulfate salt of A and / or B is a hydrated sulfate salt or an anhydrous sulfate salt.

[0055] In some embodiments, the pressing process involves pressing and granulating the precursor material. This extrusion-molded granulation reduces the gaps between the material particles, allowing the material to grow evenly on a carbon material such as a carbon tube, improving the sintering degree of the material and making the material crystal more complete. This significantly improves the specific capacity and related electrical properties compared to non-pressed granulated cathode materials. In some embodiments, the mixing process comprises at least one of airflow milling and vibration milling.

[0056] The present application adopts air flow milling or vibration milling for mixing treatment. Compared with the planetary ball milling in the prior art, the use of this grinding or air flow milling can make the particle size of the material precursor reach the submicron and micron level, which is more efficient, has lower energy consumption, higher yield, and better mixing effect, providing a good foundation for the subsequent material pressing and molding. The precursor material after the mixing treatment by air flow milling or vibration milling is sintered under an inert atmosphere, and the material crystal phase is better, and the prepared positive electrode material has good material consistency and excellent sodium storage electrochemical performance.

[0057] The present application adopts a mixing treatment method of a jet mill to repeatedly subject multi-component materials to collision friction, strong shearing and impact crushing, thereby achieving the effect of crushing and grinding the multi-component materials, so that Na2SO4, FeSO4, MSO4 or hydrated MSO4·nH2O (M is one or both of A and B) and carbon materials form a uniform mixed precursor at the nanoscale, while improving the production efficiency of precursor preparation.

[0058] In some embodiments, the air pressure of the jet mill can be 0.1-2.0 MPa, the grinding time of the jet mill can be 0.1-20 min, and the air flow of the jet mill can be dry air.

[0059] In other embodiments, the air pressure of the jet mill may be 1-2.0 MPa, or 0.5-1.2 MPa.

[0060] In other embodiments, the pulverizing time of the jet mill may be 5-15 minutes, or the pulverizing time of the jet mill may be 10-20 minutes.

[0061] The present invention utilizes high pressure forming to granulate the precursor material, so that the four components of Na2SO4, FeSO4, MSO4 or hydrated MSO4·nH2O (M is one or two of A and B) and carbon material in the precursor material can further fully contact physically, reduce the gaps at the interface between the substances, reduce the thermal diffusion resistance of the material during the sintering process, and improve the activity and Na x A y Fe 1-z B z (SO4) m / C material product consistency and purity.

[0062] In some embodiments, in step S12, the pressure of the pressing treatment may be 0.01-2 GPa, and the pressing time may be 0.1-60 min.

[0063] In other embodiments, the pressure of the pressing process may be 0.5-1.5 GPa, or the pressure of the pressing process may be 1-1.8 GPa.

[0064] In a preferred embodiment, the pressure of the pressing process is 1 GPa.

[0065] In other embodiments, the pressing time may be 30-60 min, or the pressing time may be 10-40 min.

[0066] In a preferred embodiment, the pressing time is 60 min.

[0067] In some embodiments, in step S12 , the sintering temperature may be 300-400° C., the sintering time may be 0.1-72 hours, and the sintering atmosphere may be an inert atmosphere.

[0068] In other embodiments, the temperature of the sintering process may be 330-370°C, or 300-350°C.

[0069] In other embodiments, the sintering time may be 6-18 hours, the sintering time may be 10-27 hours, or the sintering time may be 30-60 hours.

[0070] In a preferred embodiment, the sintering temperature is 350°C.

[0071] In a preferred embodiment, the sintering time is 12 hours.

[0072] In some embodiments, the inert atmosphere is a nitrogen atmosphere or a helium atmosphere.

[0073] The present application also provides a positive electrode plate, comprising a positive electrode active material layer, wherein the positive electrode active material layer comprises the above-mentioned positive electrode material.

[0074] In some embodiments, the positive electrode sheet further includes a positive current collector.

[0075] In some embodiments, the positive electrode sheet is prepared by the following steps S201-S203:

[0076] S201: Providing a positive electrode current collector, a conductive agent, a binder, a positive electrode material and an N-methylpyrrolidone solvent;

[0077] S202: uniformly mixing the conductive agent, the binder, the positive electrode material and the N-methylpyrrolidone solvent to obtain a mixed solvent;

[0078] S203: Apply the mixed solvent to the positive electrode current collector and dry it to obtain a positive electrode sheet.

[0079] In some embodiments, the mass ratio of the conductive agent, the binder, and the positive electrode material is 1-5:1-5:85-95.

[0080] In some embodiments, the binder may be polytetrafluoroethylene.

[0081] In some embodiments, the drying temperature of the drying process may be 100-140° C., and the drying time may be 10-14 hours.

[0082] In other embodiments, the drying temperature of the drying process may be 110-140° C., and the drying time may be 11-14 hours.

[0083] In other embodiments, the drying temperature of the drying process may be 100-130° C.; and the drying time may be 10-13 hours.

[0084] In some embodiments, the surface density of the positive electrode sheet obtained in this application is 9.5-11.5 mg / cm 2 .

[0085] The present application also provides a sodium ion battery, comprising the above-mentioned positive electrode plate.

[0086] In some embodiments, a sodium ion battery is prepared by the following steps S21-S22:

[0087] S21: Prepare the positive electrode sheet and the negative electrode sheet respectively.

[0088] S22: Assemble the positive electrode sheet and the negative electrode sheet into a sodium-lithium ion battery to obtain a sodium ion battery.

[0089] In some embodiments, the sodium-lithium ion battery further includes an electrolyte; the solute of the electrolyte may be sodium perchlorate or sodium hexafluorophosphate, and the solvent of the electrolyte may be one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and propylene carbonate.

[0090] In some embodiments, the concentration of sodium perchlorate or sodium hexafluorophosphate is 0.5-1.5 mol / L.

[0091] In some embodiments, the volume ratio of ethylene carbonate to dimethyl carbonate is 1-2:1-2.

[0092] In some embodiments, the negative electrode is a metal sodium plate or a hard carbon negative electrode.

[0093] In some embodiments, the negative electrode sheet is prepared by the following steps S31-S33:

[0094] S31: providing a negative electrode current collector, a conductive agent, a binder, styrene-butadiene rubber and hard carbon.

[0095] S32: Dispersing the conductive agent, the binder, the styrene-butadiene rubber and the hard carbon in water and uniformly mixing them to obtain a mixed solution.

[0096] S33: coating the mixed solution on the negative electrode current collector and drying it to obtain a negative electrode sheet.

[0097] In some embodiments, the binder may be carboxymethyl cellulose.

[0098] In some embodiments, the mass ratio of hard carbon, conductive agent, carboxymethyl cellulose and styrene-butadiene rubber is 90-100:1-2:1-2:1-3.

[0099] In a specific embodiment, the mass ratio of the hard carbon, the conductive agent, the binder and the styrene-butadiene rubber is 95:1.5:1.5:2.

[0100] In some embodiments, the drying temperature of the drying process may be 60-100° C., and the drying time may be 10-14 hours.

[0101] In other embodiments, the drying temperature of the drying process may be 60-90° C., and the drying time may be 10-13 hours.

[0102] In other embodiments, the drying temperature of the drying process may be 80-100° C.; and the drying time may be 11-14 hours.

[0103] In some embodiments, the surface density of the negative electrode obtained in this application is 2.5-3.5 mg / cm 2 .

[0104] In some embodiments, the positive electrode current collector and the negative electrode current collector are both aluminum foil, and the conductive agent is Super-p conductive agent.

[0105] In some embodiments, the sodium ion battery is a button cell, a soft pack cell, a cylindrical cell, or a prismatic cell.

[0106] Specifically, the model of the button battery can be a CR2032 button battery; it should be noted that when the sodium ion battery is assembled, the button battery is prepared by placing the positive electrode sheet, the negative electrode sheet, the diaphragm, the gasket and the spring in the button battery; the soft-pack battery is made by encapsulating the positive electrode sheet, the negative electrode sheet and the diaphragm in an aluminum-plastic film.

[0107] In a specific embodiment, a method for preparing a sodium ion battery comprises the following steps:

[0108] S301: Provide a conductive agent, a binder, a positive electrode material and an organic solvent, wherein the conductive agent is Super-p and the binder is polyvinylidene fluoride; the mass ratio of the conductive agent, the binder and the positive electrode material is 5:5:90.

[0109] S302: mixing a conductive agent, a binder, a positive electrode material, and an organic solvent to obtain a first mixed solvent;

[0110] S303: applying the first mixed solvent on aluminum foil and performing drying treatment to obtain a positive electrode plate, wherein the drying treatment temperature is 120° C. and the drying treatment time is 12 hours.

[0111] S304: Provides sodium metal sheets, Super-p, carboxymethyl cellulose, styrene-butadiene rubber and hard carbon;

[0112] S305: dispersing the sodium metal sheet, Super-p, carboxymethyl cellulose, styrene-butadiene rubber, and hard carbon in water to obtain a second mixed solvent;

[0113] S306: applying the second mixed solvent on the aluminum foil and performing drying treatment to obtain a negative electrode plate, wherein the drying treatment temperature is 80° C. and the drying treatment time is 12 hours.

[0114] It should be noted that the order of preparing the positive electrode sheet and the negative electrode sheet is not limited here.

[0115] In some embodiments, steps S307-S308 are performed, and in other embodiments, steps S309-S310 are performed.

[0116] S307: Providing a battery assembly, wherein the battery assembly includes a diaphragm, a gasket, and a spring;

[0117] S308: Installing the positive electrode sheet, the negative electrode sheet and the battery assembly into a button battery to obtain a sodium ion battery, which is a button battery.

[0118] S309: Provide diaphragm and aluminum-plastic film;

[0119] S310: Encapsulating the positive electrode sheet, the negative electrode sheet and the separator in an aluminum-plastic film to obtain a sodium ion battery, which is a soft-pack battery.

[0120] In some embodiments, the solute of the sodium ion electrolyte is 1 mol / L sodium perchlorate and 5 wt % vinylene carbonate, and the solvent is ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1.

[0121] The following lists some specific embodiments of this specification based on the above technical solutions.

[0122] Example 1

[0123] The following describes a method for preparing a sodium ion battery provided in Example 1 of the present application, the method comprising:

[0124] Step 1: Preparation of cathode material (Na 1.5 Fe 0.97 Mn 0.03 (SO4) 1.75 / CNT-5wt% positive electrode material, code number NFS1.5-Mn-3%)

[0125] 1. Dry ferrous sulfate heptahydrate in a vacuum oven at 200°C for 10 h to obtain anhydrous ferrous sulfate.

[0126] 2. Weigh 39.16g of sodium sulfate, 54.17g of anhydrous ferrous sulfate, 1.67g of anhydrous manganese sulfate, and 5.0g of carbon nanotubes (CNTs), add them into the airflow mill chamber, and perform airflow milling. The airflow is dry air, the air pressure is 1 MPa, and the airflow milling time is 10 min.

[0127] 3. The ground composite precursor is transferred to a mold and subjected to high-pressure pressing at a pressure of 1 GPa and a pressing time of 0.1 h to form a cylindrical sheet.

[0128] 4. The pressed precursor sheet was transferred to a box furnace and heat treated under a nitrogen atmosphere at 350°C for 12 hours. The calcined product was ground into powder to obtain a composite material containing 5 wt% of carbon nanotubes, thereby obtaining a positive electrode material.

[0129] Step 2: Prepare the sodium-ion battery

[0130] 1. Preparation of positive electrode sheet: According to the mass ratio of 90:5:5, 0.9g of positive electrode material, 0.05g of Super-p as a conductive agent, and 0.05g of polyvinylidene fluoride as a binder were weighed respectively. The above three materials were dispersed in N-methylpyrrolidone solvent, mixed evenly, and then coated on aluminum foil. Dry under vacuum conditions at 120℃ for 12h to obtain a positive electrode sheet with an area density of 11mg / cm 2 .

[0131] 2. Prepare the negative electrode: Use a metal sodium sheet as the negative electrode.

[0132] 3. Place the positive electrode sheet, diaphragm, negative electrode sheet, gasket, and spring in the order of CR2032 button battery, add sodium perchlorate as solute, ethylene carbonate and dimethyl carbonate with a volume ratio of 1:1 as solvent, 5wt% vinylene carbonate as additive, and electrolyte with a solute concentration of 1mol / L, and obtain a sodium ion battery after packaging.

[0133] Example 2

[0134] The following describes a method for preparing a sodium ion battery provided in Example 2 of the present application, the method comprising:

[0135] Step 1: Preparation of cathode material (Na 1.5 Fe 0.97 Zn 0.03 (SO4) 1.75 / CNT-5wt% positive electrode material, code number NFS1.5-Zn-3%)

[0136] Example 2 of the present application is based on the technical solution of Example 1, and the similarities are not repeated here. The difference between Example 2 and Example 1 is that 39.12g of sodium sulfate, 54.11g of anhydrous ferrous sulfate, 1.78g of anhydrous zinc sulfate, and 5.0g of carbon nanotubes are weighed and added into the air flow mill bin for air flow mill mixing.

[0137] Step 2: The method for preparing a sodium ion battery is the same as that in Example 1.

[0138] Example 3

[0139] The following describes a method for preparing a sodium ion battery provided in Example 3 of the present application, the method comprising:

[0140] Step 1: Preparation of cathode material (Na 1.5 Fe 0.97 Mg 0.03 (SO4) 1.75 / CNT-5wt% positive electrode material, code number NFS1.5-Mg-3%)

[0141] Example 3 of the present application is based on the technical solution of Example 1, and the similarities are not repeated here. The difference between Example 3 and Example 1 is that 39.30g of sodium sulfate, 54.36g of anhydrous ferrous sulfate, 1.33g of anhydrous magnesium sulfate, and 5.0g of carbon nanotubes are weighed and added into the air flow mill bin for air flow mill mixing.

[0142] Step 2: The method for preparing a sodium ion battery is the same as that in Example 1.

[0143] Example 4

[0144] The following describes a method for preparing a sodium ion battery provided in Example 4 of the present application, the method comprising:

[0145] Step 1: Preparation of cathode material (Na 1.5 Fe 0.97 Ca 0.03 (SO4) 1.75 / CNT-5wt% positive electrode material, numbered NFS1.5-Ca-3%)

[0146] Step 1 is the same as Example 1, except that 39.23 g of sodium sulfate, 54.27 g of anhydrous ferrous sulfate, 1.5 g of anhydrous calcium sulfate, and 5.0 g of carbon nanotubes are weighed and added into the airflow mill chamber to perform airflow mill mixing.

[0147] Step 2: The method for preparing a sodium ion battery is the same as that in Example 1.

[0148] Example 5

[0149] The following describes a method for preparing a sodium ion battery provided in Example 5 of the present application, the method comprising:

[0150] Step 1: Preparation of cathode material (Na 1.5 Fe 0.97 Ni 0.03 (SO4) 1.75 / CNT-5wt% positive electrode material, code number NFS1.5-Ni-3%)

[0151] Step 1 is the same as Example 1, except that 39.15 g of sodium sulfate, 54.15 g of anhydrous ferrous sulfate, 1.71 g of anhydrous nickel sulfate, and 5.0 g of carbon nanotubes are weighed and added into the airflow mill chamber for airflow mill mixing.

[0152] Step 2: The method for preparing a sodium ion battery is the same as that in Example 1.

[0153] Example 6

[0154] The following describes a method for preparing a sodium ion battery provided in Example 6 of the present application, the method comprising:

[0155] Step 1: Preparation of cathode material (Na 1.5 Fe 0.97 Cu 0.03 (SO4) 1.75 / CNT-5wt% positive electrode material, code number NFS1.5-Cu-3%)

[0156] Step 1 is the same as Example 1, except that 39.12 g of sodium sulfate, 54.12 g of anhydrous ferrous sulfate, 1.76 g of anhydrous copper sulfate, and 5.0 g of carbon nanotubes are weighed and added into the airflow mill chamber to perform airflow mill mixing.

[0157] Step 2: The method for preparing a sodium ion battery is the same as that in Example 1.

[0158] Example 7

[0159] The following describes a method for preparing a sodium ion battery provided in Example 7 of the present application, the method comprising:

[0160] Step 1: Preparation of cathode material (Na 1.5 Fe 0.97 Ba 0.03 (SO4) 1.75 / CNT-5wt% positive electrode material, code number NFS1.5-Ba-3%)

[0161] Step 1 is the same as Example 1, except that 38.79 g of sodium sulfate, 53.66 g of anhydrous ferrous sulfate, 2.55 g of anhydrous barium sulfate, and 5.0 g of carbon nanotubes are added to the airflow mill chamber and mixed by airflow milling.

[0162] Step 2: The method for preparing a sodium ion battery is the same as that in Example 1.

[0163] Example 8

[0164] The following describes a method for preparing a sodium ion battery provided in Example 8 of the present application, the method comprising:

[0165] Step 1: Preparation of cathode material (K 0.03 Na 1.47 Fe(SO4) 1.75 / CNT-5wt% positive electrode material, code number NFS1.5-K-3%)

[0166] Step 1 is the same as Example 1, except that 38.31 g of sodium sulfate, 0.96 g of potassium sulfate, 55.74 g of anhydrous ferrous sulfate, and 5.0 g of carbon nanotubes are weighed and added into the airflow mill chamber for airflow mill mixing.

[0167] Step 2: The method for preparing a sodium ion battery is the same as that in Example 1.

[0168] Example 9

[0169] The following describes a method for preparing a sodium ion battery provided in Example 9 of the present application, the method comprising:

[0170] Step 1: Preparation of cathode material (Na 1.5 Fe 0.97 Co 0.03 (SO4) 1.75 / CNT-5wt% positive electrode material, code number NFS1.5-Co-3%)

[0171] Step 1 is the same as Example 1, except that 39.15 g of sodium sulfate, 54.15 g of anhydrous ferrous sulfate, 1.71 g of anhydrous cobalt sulfate, and 5.0 g of carbon nanotubes are weighed and added into the airflow mill chamber to perform airflow mill mixing.

[0172] Step 2: The method for preparing a sodium ion battery is the same as that in Example 1.

[0173] Example 10

[0174] The following describes a method for preparing a sodium ion battery provided in Example 10 of the present application, the method comprising:

[0175] Step 1: Preparation of cathode material (Na 1.1 Fe 0.97 Zn 0.03 (SO4) 1.55 / CNT-5wt% positive electrode material, numbered NFS1.1-Zn-3%)

[0176] Step 1 is the same as Example 1, except that 32.22 g of sodium sulfate, 60.78 g of anhydrous ferrous sulfate, 2 g of anhydrous zinc sulfate, and 5.0 g of carbon nanotubes are weighed and added into the airflow mill chamber to perform airflow mill mixing.

[0177] Step 2: The method for preparing a sodium ion battery is the same as that in Example 1.

[0178] Example 11

[0179] The following describes a method for preparing a sodium ion battery provided in Example 11 of the present application, the method comprising:

[0180] Step 1: Preparation of cathode material (Na 1.3 Fe 0.97 Zn 0.03 (SO4) 1.65 / CNT-5wt% positive electrode material, code number NFS1.3-Zn-3%)

[0181] Step 1 is the same as Example 1, except that 35.87 g of sodium sulfate, 57.25 g of anhydrous ferrous sulfate, 1.88 g of anhydrous zinc sulfate, and 5.0 g of carbon nanotubes are weighed and added into the airflow mill chamber to perform airflow mill mixing.

[0182] Step 2: The method for preparing a sodium ion battery is the same as that in Example 1.

[0183] Example 12

[0184] The following describes a method for preparing a sodium ion battery provided in Example 12 of the present application, the method comprising:

[0185] Step 1: Preparation of cathode material (Na 1.7 Fe0.97 Zn 0.03 (SO4) 1.85 / CNT-5wt% positive electrode material, code number NFS1.7-Zn-3%)

[0186] Step 1 is the same as Example 1, except that 42.02 g of sodium sulfate, 51.29 g of anhydrous ferrous sulfate, 1.69 g of anhydrous zinc sulfate, and 5.0 g of carbon nanotubes are weighed and added into the airflow mill chamber to perform airflow mill mixing.

[0187] Step 2: The method for preparing a sodium ion battery is the same as that in Example 1.

[0188] Example 13

[0189] The following describes a method for preparing a sodium ion battery provided in Example 13 of the present application, the method comprising:

[0190] Step 1: Preparation of cathode material (Na 1.5 Fe 0.95 Zn 0.05 (SO4) 1.75 / CNT-5wt% positive electrode material, code number NFS1.5-Zn-5%)

[0191] Step 1 is the same as Example 1, except that 39.09 g of sodium sulfate, 52.95 g of anhydrous ferrous sulfate, 2.96 g of anhydrous zinc sulfate, and 5.0 g of carbon nanotubes are weighed and added into the airflow mill chamber to perform airflow mill mixing.

[0192] Step 2: The method for preparing a sodium ion battery is the same as that in Example 1.

[0193] Example 14

[0194] The following describes a method for preparing a sodium ion battery provided in Example 14 of the present application, the method comprising:

[0195] Step 1: Preparation of cathode material (Na 1.5 Fe 0.90 Zn 0.10 (SO4) 1.75 / CNT-5wt% positive electrode material, code number NFS1.5-Zn-10%)

[0196] Step 1 is the same as Example 1, except that 39.02 g of sodium sulfate, 50.07 g of anhydrous ferrous sulfate, 5.91 g of anhydrous zinc sulfate, and 5.0 g of carbon nanotubes are weighed and added into the airflow mill chamber to perform airflow mill mixing.

[0197] Step 2: The method for preparing a sodium ion battery is the same as that in Example 1.

[0198] Example 15

[0199] The following describes a method for preparing a sodium ion battery provided in Example 15 of the present application, the method comprising:

[0200] Step 1: Preparation of cathode material (Na 1.5 Fe 0.99 Zn 0.01 (SO4) 1.75 / CNT-5wt% positive electrode material, code number NFS1.5-Zn-1%)

[0201] Step 1 is the same as Example 1, except that 39.15 g of sodium sulfate, 55.26 g of anhydrous ferrous sulfate, 0.59 g of anhydrous zinc sulfate, and 5.0 g of carbon nanotubes are weighed and added into the airflow mill chamber to perform airflow mill mixing.

[0202] Step 2: The method for preparing a sodium ion battery is the same as that in Example 1.

[0203] Example 16

[0204] The following describes a method for preparing a sodium ion battery provided in Example 16 of the present application, the method comprising:

[0205] Step 1: Preparation of cathode material (Na 1.3 Fe 0.97 Mg 0.03 (SO4) 1.65 / CNT-5wt% positive electrode material, numbered NFS1.3-Mg-3%)

[0206] Step 1 is the same as Example 1, except that 36.05 g of sodium sulfate, 57.54 g of anhydrous ferrous sulfate, 1.41 g of anhydrous magnesium sulfate, and 5.0 g of carbon nanotubes are weighed and added into the airflow mill chamber to perform airflow mill mixing.

[0207] Step 2: The method for preparing a sodium ion battery is the same as that in Example 1.

[0208] Example 17

[0209] The following describes a method for preparing a sodium ion battery provided in Example 17 of the present application, the method comprising:

[0210] Step 1: Preparation of cathode material (Na 1.5 Fe 0.97 Zn 0.015 Cu 0.015 (SO4) 1.75 / CNT-5wt% positive electrode material, numbered NFS1.5-Zn-1.5%-Cu-1.5%)

[0211] Step 1 is the same as Example 1, except that 39.12 g of sodium sulfate, 54.11 g of anhydrous ferrous sulfate, 0.89 g of anhydrous zinc sulfate, 0.88 g of anhydrous copper sulfate, and 5.0 g of carbon nanotubes are weighed and added into the airflow mill chamber for airflow mill mixing.

[0212] Step 2: The method for preparing a sodium ion battery is the same as that in Example 1.

[0213] Example 18

[0214] The following describes a method for preparing a sodium ion battery provided in Example 18 of the present application, the method comprising:

[0215] Step 1: Preparation of cathode material (Na 1.5 Fe 0.97 Zn 0.015 Ni 0.015 (SO4) 1.75 / CNT-5wt% positive electrode material, numbered NFS1.5-Zn-1.5%-Ni-1.5%)

[0216] Step 1 is the same as Example 1, except that 39.13 g of sodium sulfate, 54.13 g of anhydrous ferrous sulfate, 0.89 g of anhydrous zinc sulfate, 0.85 g of anhydrous nickel sulfate, and 5.0 g of carbon nanotubes are weighed and added into the airflow mill chamber for airflow mill mixing.

[0217] Step 2: The method for preparing a sodium ion battery is the same as that in Example 1.

[0218] Example 19

[0219] The following describes a method for preparing a sodium ion battery provided in Example 19 of the present application, the method comprising:

[0220] Step 1: Preparation of cathode material (Na 1.5 Fe 0.97 Zn 0.01 Cu 0.01 Ni 0.01 (SO4) 1.75 / CNT-5wt% positive electrode material, numbered NFS1.5-Zn-1%-Cu-1%-Ni-1%)

[0221] Step 1 is the same as Example 1, except that 39.13 g of sodium sulfate, 54.12 g of anhydrous ferrous sulfate, 0.59 g of anhydrous zinc sulfate, 0.59 g of anhydrous copper sulfate, 0.57 g of anhydrous nickel sulfate, and 5.0 g of carbon nanotubes are weighed and added into the airflow mill chamber for airflow mill mixing.

[0222] Step 2: The method for preparing a sodium ion battery is the same as that in Example 1.

[0223] Example 20

[0224] The following describes a method for preparing a sodium ion battery provided in Example 20 of the present application, the method comprising:

[0225] Step 1: Prepare the positive electrode material

[0226] (K 0.03 Na 1.47 Fe 0.97 Zn 0.006 Cu 0.006 Ni 0.006 Co 0.006 Mg 0.006 (SO4) 1.75 / CNT-5wt% positive electrode material, numbered NFS1.5-Zn-0.6%-Cu-0.6%-Ni-0.6%-Co-0.6%-Mg-0.6%-K-3%)

[0227] Step 1 is the same as Example 1, except that 38.31 g of sodium sulfate, 54.07 g of anhydrous ferrous sulfate, 0.36 g of anhydrous zinc sulfate, 0.35 g of anhydrous copper sulfate, 0.34 g of anhydrous nickel sulfate, 0.34 g of anhydrous cobalt sulfate, 0.27 g of anhydrous magnesium sulfate, 0.96 g of anhydrous potassium sulfate, and 5.0 g of carbon nanotubes are weighed and added to the airflow mill chamber for airflow mill mixing.

[0228] Step 2: The method for preparing a sodium ion battery is the same as that in Example 1.

[0229] Example 21

[0230] The following describes a method for preparing a sodium ion battery provided in Example 21 of the present application, the method comprising:

[0231] Step 1: Preparation of cathode material (Na 1.5 Fe 0.97 Zn 0.03 (SO4) 1.75 / CNT-5wt% positive electrode material, code number NFS1.5-Zn-3%)

[0232] Step 1 is the same as Example 1, except that 39.12 g of sodium sulfate, 54.11 g of anhydrous ferrous sulfate, 1.78 g of anhydrous zinc sulfate, and 5.0 g of carbon nanotubes are weighed and added into the airflow mill chamber to perform airflow mill mixing.

[0233] Step 2: Prepare the sodium-ion battery

[0234] 1. Preparation of positive electrode sheet: Weigh 0.9g of positive electrode material, weigh 0.05g of Super-p as a conductive agent and 0.05g of polyvinylidene fluoride as a binder in a mass ratio of 90:5:5, disperse the above three materials in N-methylpyrrolidone solvent, mix them evenly and apply them on aluminum foil, and dry them under vacuum at 120℃ for 12h to obtain a positive electrode sheet with an area density of 9.5-11.5mg / cm 2 .

[0235] 2. Preparation of negative electrode sheet: Weigh 0.95g of hard carbon negative electrode material, weigh 0.015g of Super-p as a conductive agent, 0.02g of styrene-butadiene rubber, and 0.015g of carboxymethyl cellulose as a binder in a mass ratio of 95:1.5:2:1.5. Disperse the above four materials in pure water, mix them evenly, and then apply them on aluminum foil. Dry them under vacuum at 80℃ for 12h to obtain a negative electrode sheet with an area density of 2.5-3.5mg / cm 2 .

[0236] 3. Place the positive electrode sheet, diaphragm, negative electrode sheet, gasket, and spring in the order of CR2032 button battery, add sodium perchlorate as solute, ethylene carbonate and dimethyl carbonate with a volume ratio of 1:1 as solvent, 5wt% vinylene carbonate as additive, and electrolyte with a solute concentration of 1mol / L, and obtain a sodium ion battery after packaging.

[0237] Example 22

[0238] The following describes a method for preparing a sodium ion battery provided in Example 22 of the present application, the method comprising:

[0239] Step 1: Preparation of cathode material (Na 1.5 Fe 0.97 Zn 0.03 (SO4) 1.75 / CNT-5wt% positive electrode material)

[0240] 1. Dry ferrous sulfate heptahydrate in a vacuum oven at 200°C for 10 h to obtain anhydrous ferrous sulfate.

[0241] 2. Weigh 39.12 g of sodium sulfate, 54.11 g of anhydrous ferrous sulfate, 1.78 g of anhydrous zinc sulfate, and 5.0 g of carbon nanotubes, add them into the airflow mill chamber, and perform airflow milling. The airflow is dry air, the air pressure is 0.1 MPa, and the airflow milling time is 20 min.

[0242] 3. The ground composite precursor was transferred to a mold and subjected to high-pressure pressing at a pressure of 0.01 GPa for 60 minutes to form a cylindrical sheet.

[0243] 4. The pressed precursor sheet was transferred to a box furnace and heat treated under a nitrogen atmosphere at 300°C for 72 hours. The calcined product was ground into powder to obtain a composite material containing 5 wt% of carbon nanotubes, thereby obtaining a positive electrode material.

[0244] Step 2: Prepare the sodium-ion battery

[0245] 1. Preparation of positive electrode sheet: Weigh 0.9 g of positive electrode material, weigh Super-p as a conductive agent and polyvinylidene fluoride as a binder in a mass ratio of 85:1:1, disperse the above three materials in N-methylpyrrolidone solvent, mix them evenly and apply them on aluminum foil, and dry them under vacuum at 100°C for 10 hours to obtain a positive electrode sheet with an area density of 9.5 mg / cm 2 .

[0246] 2. Prepare the negative electrode: Use a metal sodium sheet as the negative electrode.

[0247] 3. Place the positive electrode sheet, separator, negative electrode sheet, gasket, and spring in the order of CR2032 button battery, add sodium perchlorate as solute, ethylene carbonate and dimethyl carbonate with a volume ratio of 1:1 as solvent, 3wt% of vinylene carbonate as additive, and electrolyte with a solute concentration of 0.5mol / L, and encapsulate to obtain a sodium ion battery.

[0248] Example 23

[0249] The following describes a method for preparing a sodium ion battery provided in Example 23 of the present application, the method comprising:

[0250] Step 1: Preparation of cathode material (Na 1.5 Fe 0.97 Zn 0.03 (SO4) 1.75 / CNT-5wt% positive electrode material)

[0251] 1. Dry ferrous sulfate heptahydrate in a vacuum oven at 200°C for 10 h to obtain anhydrous ferrous sulfate.

[0252] 2. Weigh 39.12 g of sodium sulfate, 54.11 g of anhydrous ferrous sulfate, 1.78 g of anhydrous zinc sulfate, and 5.0 g of carbon nanotubes, add them into the airflow mill chamber, and vibrate and mix them. The airflow is dry air, the air pressure is 2 MPa, and the airflow milling time is 0.1 min.

[0253] 3. The ground composite precursor was transferred to a mold and subjected to high-pressure pressing at a pressure of 2 GPa and a pressing time of 0.1 min to form a cylindrical sheet.

[0254] 4. The pressed precursor sheet was transferred to a box furnace and heat treated under a nitrogen atmosphere at 400°C for 0.1 h. The calcined product was ground into powder to obtain a composite material containing 5 wt% of carbon nanotubes, thereby obtaining a positive electrode material.

[0255] Step 2: 1. Prepare the positive electrode sheet: Weigh 0.9 g of the positive electrode material, weigh Super-p as a conductive agent and polyvinylidene fluoride as a binder in a mass ratio of 95:5:5, disperse the above three materials in N-methylpyrrolidone solvent, mix them evenly, and then apply them on aluminum foil. Dry them under vacuum at 140°C for 14 hours to obtain the positive electrode sheet. The obtained sheet has an area density of 11.5 mg / cm 2 .

[0256] 2. Preparation of negative electrode sheet: Weigh 0.95g of hard carbon negative electrode material, weigh Super-p as a conductive agent, styrene-butadiene rubber, and carboxymethyl cellulose as a binder in a mass ratio of 100:2:3:2, disperse the above four materials in pure water, mix them evenly, and then apply them on aluminum foil. Dry them under vacuum at 100℃ for 10h to obtain a negative electrode sheet with an area density of 3.5mg / cm 2 .

[0257] 3. Place the positive electrode sheet, separator, negative electrode sheet, gasket, and spring in the order of CR2032 button battery, add sodium perchlorate as the solute, the solvent is ethylene carbonate and dimethyl carbonate with a volume ratio of 1:2, the additive is 7wt% of vinylene carbonate, and the electrolyte with a solute concentration of 1.5mol / L, and encapsulate to obtain a sodium ion battery.

[0258] Example 24

[0259] The following describes a method for preparing a sodium ion battery provided in Example 24 of the present application, the method comprising:

[0260] Step 1: Same as Example 22.

[0261] Step 2: Prepare the sodium-ion battery

[0262] 1. Preparation of positive electrode sheet: Weigh 0.9 g of positive electrode material, weigh 0.05 g of Super-p as a conductive agent and 0.05 g of polyvinylidene fluoride as a binder in a mass ratio of 90:5:5, disperse the above three materials in N-methylpyrrolidone solvent, mix them evenly, and then apply them on aluminum foil. Dry them under vacuum at 120 ° C for 12 hours to obtain a positive electrode sheet with an area density of 9.5 mg / cm 2 .

[0263] 2. Prepare the negative electrode: Use a metal sodium sheet as the negative electrode.

[0264] 3. Place the positive electrode sheet, diaphragm, negative electrode sheet, gasket, and spring in the order of soft-pack battery, add sodium perchlorate as solute, solvent as ethylene carbonate and dimethyl carbonate with a volume ratio of 1:1, additive as 3wt% vinylene carbonate, and electrolyte with a solute concentration of 0.5mol / L, and obtain a sodium ion battery after packaging.

[0265] Example 25

[0266] The following describes a method for preparing a sodium ion battery provided in Example 25 of the present application, the method comprising:

[0267] Step 1: Same as Example 22.

[0268] Step 2: Prepare the sodium-ion battery

[0269] 1. Preparation of positive electrode sheet: Weigh 0.9 g of positive electrode material, weigh 0.05 g of Super-p as a conductive agent and 0.05 g of polyvinylidene fluoride as a binder in a mass ratio of 90:5:5, disperse the above three materials in N-methylpyrrolidone solvent, mix them evenly, and then apply them on aluminum foil. Dry them under vacuum at 120 ° C for 12 hours to obtain a positive electrode sheet with an area density of 9.5 mg / cm 2 .

[0270] 2. Prepare the negative electrode: Use a metal sodium sheet as the negative electrode.

[0271] 3. Place the positive electrode sheet, diaphragm, negative electrode sheet, gasket, and spring in the order of the positive electrode sheet and the negative electrode sheet in a soft-pack battery, add an electrolyte with sodium hexafluorophosphate as the solute, diethyl carbonate and ethyl methyl carbonate in a volume ratio of 1:1 as the solvent, 3 wt% of vinylene carbonate as the additive, and a solute concentration of 0.5 mol / L, and obtain a sodium ion battery after packaging.

[0272] Example 26

[0273] The following describes a method for preparing a sodium ion battery provided in Example 26 of the present application, the method comprising:

[0274] Step 1: Preparation of cathode material (K 0.17 Na 1.53 Fe(SO4) 1.85 / CNT-5wt% positive electrode material, numbered NFS1.7-K-17%)

[0275] Step 1 is the same as Example 1, except that 39.87 g of sodium sulfate, 5.44 g of potassium sulfate, 55.74 g of anhydrous ferrous sulfate, and 5.0 g of carbon nanotubes are weighed and added into the airflow mill chamber for airflow mill mixing.

[0276] Step 2: Prepare the sodium-ion battery

[0277] 1. Preparation of positive electrode sheet: Weigh 0.9 g of positive electrode material, weigh 0.05 g of Super-p as a conductive agent and 0.05 g of polyvinylidene fluoride as a binder in a mass ratio of 90:5:5, disperse the above three materials in N-methylpyrrolidone solvent, mix them evenly, and then apply them on aluminum foil. Dry them under vacuum at 120 ° C for 12 hours to obtain a positive electrode sheet with an area density of 9.5 mg / cm 2 .

[0278] 2. Prepare the negative electrode: Use a metal sodium sheet as the negative electrode.

[0279] 3. Place the positive electrode sheet, separator, negative electrode sheet, gasket, and spring in the order of CR2032 button battery, add sodium perchlorate as the solute, propylene carbonate with a volume ratio of 1:2 as the solvent, 7 wt% of vinylene carbonate as the additive, and an electrolyte with a solute concentration of 1.5 mol / L, and encapsulate to obtain a sodium ion battery.

[0280] Example 27

[0281] The following describes a method for preparing a sodium ion battery provided in Example 27 of the present application, the method comprising:

[0282] Step 1 and step 2 are the same as Example 22, except that 39.12 g of sodium sulfate, 54.11 g of anhydrous ferrous sulfate, 1.78 g of anhydrous zinc sulfate, and 5.0 g of carbon fiber are weighed and added to the airflow mill bin for airflow mill mixing.

[0283] Example 28

[0284] The following describes a method for preparing a sodium ion battery provided in Example 28 of the present application, the method comprising:

[0285] Step 1 and step 2 are the same as Example 22, except that 39.12 g of sodium sulfate, 54.11 g of anhydrous ferrous sulfate, 1.78 g of anhydrous zinc sulfate, and 5.0 g of graphene are weighed and added to the airflow mill bin for airflow mill mixing.

[0286] Example 29

[0287] The following describes a method for preparing a sodium ion battery provided in Example 29 of the present application, the method comprising:

[0288] Step 1 and step 2 are the same as Example 22, except that 39.12 g of sodium sulfate, 54.11 g of anhydrous ferrous sulfate, 1.78 g of anhydrous zinc sulfate, and 5.0 g of reduced graphene oxide are weighed and added to the airflow mill bin for airflow mill mixing.

[0289] Example 30

[0290] The following describes a method for preparing a sodium ion battery provided in Example 30 of the present application, the method comprising:

[0291] Step 1 and step 2 are the same as Example 22, except that 39.12 g of sodium sulfate, 54.11 g of anhydrous ferrous sulfate, 1.78 g of anhydrous zinc sulfate, and 5.0 g of conductive carbon black are weighed and added to the airflow mill bin for airflow mill mixing.

[0292] Example 31

[0293] The following describes a method for preparing a sodium ion battery provided in Example 31 of the present application, the method comprising:

[0294] Step 1 and step 2 are the same as Example 22, except that 39.12 g of sodium sulfate, 54.11 g of anhydrous ferrous sulfate, 1.78 g of anhydrous zinc sulfate, and 5.0 g of MXene are weighed and added to the airflow mill bin for airflow mill mixing.

[0295] Example 32

[0296] The following describes a method for preparing a sodium ion battery provided in Example 32 of the present application, the method comprising:

[0297] Step 1 and step 2 are the same as Example 22, except that 39.12 g of sodium sulfate, 54.11 g of anhydrous ferrous sulfate, 1.78 g of anhydrous zinc sulfate, and 0.1 g of carbon nanotubes are weighed and added to the airflow mill chamber for airflow mill mixing.

[0298] Example 33

[0299] The following describes a method for preparing a sodium ion battery provided in Example 33 of the present application, the method comprising:

[0300] Step 1 and step 2 are the same as Example 22, except that 39.12 g of sodium sulfate, 54.11 g of anhydrous ferrous sulfate, 1.78 g of anhydrous zinc sulfate, and 10 g of carbon nanotubes are weighed and added to the airflow mill chamber for airflow mill mixing.

[0301] Comparative Example 1

[0302] Step 1: Preparation of cathode material (Na 1.5 Fe 1.0 (SO4) 1.75 / CNT-5wt% cathode material, NFS1.5-P)

[0303] Step 1 is the same as Example 1, except that 39.15 g of sodium sulfate, 55.88 g of anhydrous ferrous sulfate, and 5.0 g of carbon nanotubes are weighed and added into the airflow mill chamber to perform airflow mill mixing.

[0304] Step 2: The method for preparing a sodium ion battery is the same as that in Example 1.

[0305] Comparative Example 2

[0306] Step 1: Preparation of cathode material (Na 1.3 Fe 1.0 (SO4) 1.75 / CNT-5wt% cathode material, NFS1.3-P)

[0307] Step 1 is the same as Example 1, except that 39.15 g of sodium sulfate, 55.88 g of anhydrous ferrous sulfate, and 5.0 g of carbon nanotubes are weighed and added into the airflow mill chamber to perform airflow mill mixing.

[0308] Step 2: The method for preparing a sodium ion battery is the same as that in Example 1.

[0309] The XRD diffraction peaks of the above embodiments and comparative examples are shown in Figures 4, 5, 8, 11 and 13.

[0310] Effect evaluation

[0311] Table 1 Capacity retention rate of positive electrode materials doped with different metal cations

[0312] Figures 1, 2, and Table 1 show the electrochemical properties of positive electrode materials doped with a single metal cation. Referring to Figures 1, 2, and Table 1, in Examples 1-9, after 500 cycles at a current density of 1C, the battery capacity retention rate remained above 94.6%, which was higher than 93.03% in Comparative Example 1. Among them, the capacity retention rate of Example 2 (doped with zinc ions) was even as high as 97.22%, much higher than 93.03% in Comparative Example 1, demonstrating excellent cycle stability.

[0313] Please refer to Figure 1, Figure 2, and Table 1. In Examples 1-9, after 500 cycles at a current density of 2C, the battery capacity retention rate is still maintained at above 94.6%, which is higher than the 94.13% of Comparative Example 1. Among them, the capacity retention rates of Example 2 (doped with zinc ions) and Example 6 (doped with copper ions) are even as high as 98.12% and 98.13%, which are much higher than the 94.13% of Comparative Example 1, showing excellent cycle stability.

[0314] Please refer to Figure 1, Figure 2, and Table 1. In Examples 1-9, the capacity retention rate at a current density of 2C is higher than that at a current density of 1C, showing excellent rate performance.

[0315] 3 , in Examples 2 and 4-8, at a current density of 5C, the discharge specific capacity of the positive electrode materials doped with metal cations is higher than that of Comparative Example 1, demonstrating excellent high-rate performance.

[0316] Table 2 Capacity retention rate of positive electrode materials doped with (Zn) at different sodium-iron ratios

[0317] Figures 6-7 and Table 2 show the electrochemical properties of positive electrode materials doped with different sodium-iron ratios. Please refer to Figures 6, 7 and Table 2. In Examples 2 and 10-12, after 400 cycles at a current density of 2C, the battery capacity retention rate is still maintained at more than 96.77%. Among them, the capacity retention rate of Example 2 (doped with zinc ions) is even as high as 99.1%, which is much higher than the 95.34% of Comparative Example 1, showing excellent cycle stability and rate performance.

[0318] Table 3 Capacity retention of positive electrode materials with different percentages of NFS doped with Zn

[0319] Figures 9-10 and Table 3 show the electrochemical properties of positive electrode materials doped with different Zn percentages. Please refer to Figures 9, 10, and Table 3. In Examples 2 and 13-15, after 400 cycles at a current density of 2C, the battery capacity retention rate is still maintained at more than 94.42%. Among them, the capacity retention rate of Example 2 (zinc content 3%) is even as high as 99.1%, showing excellent cycle stability and rate performance.

[0320] Table 4 Capacity retention of positive electrode materials doped with different metal cations

[0321] Figure 12 and Table 4 show the electrochemical performance of positive electrode materials doped with different metal cations when x = 1.3. Please refer to Figure 12 and Table 4. In Examples 11 and 16, after 500 cycles at a current density of 2C, the battery capacity retention rate is still maintained at more than 95.93%, which is much higher than the 93.73% of Comparative Example 2, showing excellent cycle stability and rate performance.

[0322] Table 5 Capacity retention of NFS multi-element doped cathode materials

[0323] Figure 14 and Table 5 show the electrochemical properties of the NFS multi-element doped positive electrode material. Please refer to Table 5. In Examples 17-20, after 500 cycles at a current density of 2C, the battery capacity retention rate is still maintained at above 95.36%, which is higher than 94.13% of Comparative Example 1, showing excellent cycle stability and rate performance.

[0324] Referring to FIG14 , in Example 19, after charge and discharge at 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, and 0.1C, the battery capacity retention rate is maintained at approximately 99%, demonstrating excellent rate performance.

[0325] Figure 15 shows the electrochemical performance of a zinc-doped full cell. In Example 21, the specific testing method was as follows: After the assembled full cell rested for 2 hours, it was charged at a constant current of 0.2C to 4.5V at a current density of 0.5C. The voltage was then maintained until the current dropped below 0.05C. The cell was then allowed to rest for 5 hours and discharged at a constant current of 0.2C to 2.0V, completing the first cycle of formation. As shown in Figure 15, at a current density of 0.1C, the first-cycle charge capacity of the pouch cell was 27.8mAh, the first-cycle discharge capacity was 26.8mAh, the charge-discharge efficiency was 96.41%, and the operating potential reached 3.7V, demonstrating excellent first-cycle coulombic efficiency.

[0326] In Examples 21-26, after the batteries were cycled 500 times at a current density of 2C, the capacity retention rates were 96.35%, 97.27%, 95.33%, 97.19%, 95.43%, and 96.16%, respectively. The capacity retention rates were all maintained above 95%, reflecting excellent cycle stability and rate performance.

[0327] In Examples 27-33, after the batteries were cycled 500 times at a current density of 2C, the capacity retention rates were maintained above 95%, demonstrating excellent cycle stability and rate performance.

[0328] In addition, for each of the technical solutions of Examples 1-14, a comparative example without material pressing was provided. That is, after uniform mixing by airflow milling or vibration milling, the materials were not high-pressure pressed into cylindrical sheets, but were directly sintered under an inert protective atmosphere. The discharge specific capacity of the comparative example without pressing corresponding to each embodiment was tested. The results are shown in Table 6, where the discharge specific capacity is expressed in mAh / g. Based on the data in Table 6, it can be seen that, under the same system, the discharge specific capacity can be significantly improved by pressing the materials.

[0329] Table 6 Discharge capacity of pressed and unpressed

[0330] Due to the above technical solution, the present application provides a positive electrode material, preparation method, positive electrode plate and sodium ion battery, which have the following beneficial effects:

[0331] The present application adds cation-doped sodium ferric sulfate and carbon material to the positive electrode material, performs intra-lattice cation doping on the sodium ferric sulfate and modifies the carbon material. The in-situ cation doping can improve the crystal structure stability of the sodium ferric sulfate active material. At the same time, the co-modification with the carbon material improves the electronic conductivity and sodium ion diffusion rate of the sodium ferric sulfate material and the stability of its crystal structure, thereby improving the quality and consistency of the positive electrode material product, improving the electrochemical sodium storage performance of the positive electrode material, and the long-cycle stability and high-rate performance of the positive electrode material during the electrochemical sodium storage process, ensuring large-scale mass production of the material, improving the production efficiency of the finished material, reducing costs, and rapidly promoting the commercialization and practical application of high-performance sodium ferric sulfate-based sodium ion battery products.

[0332] The present invention adopts in-situ preparation technology to dope metal cations into the crystal structure of sodium ferric sulfate material to obtain a positive electrode material with high working voltage, high structural stability, excellent cycle and rate performance. The positive electrode material includes cation-doped sodium ferric sulfate (Na x A y Fe 1-z B z (SO4) m The NAFBS / C composite material is prepared through a three-step process of precursor mixing, material granulation and molding, and low-temperature sintering to achieve in-situ cation doping of sodium ferrous sulfate and composite carbon materials, resulting in a cathode material with high material consistency and quality. This further improves the structural stability of the sodium ferrous sulfate-based cathode material and its comprehensive performance during long-term cycling stability and high rate electrochemical sodium storage, providing process optimization for the industrialization of polyanionic cathode materials.

[0333] The above description has fully disclosed the specific embodiments of this application. It should be noted that any changes made by those skilled in the art to the specific embodiments of this application do not depart from the scope of the claims of this application. Accordingly, the scope of the claims of this application is not limited to the above specific embodiments.

Claims

1. A positive electrode material, characterized in that: The invention comprises cation-doped sodium iron sulfate and a carbon material, wherein the carbon material in situ modifies the cation-doped sodium iron sulfate, and the general formula of the cation-doped sodium iron sulfate is Na x A y Fe 1-z B z (SO4) m ; Among them, 1.1≤x+y≤1.7, 0≤y≤0.17, 0≤z≤0.1, y and z are not 0 at the same time and x, y, z and m are in charge balance; A is K + , B is selected from Mn 2+ 、Ni 2+ 、Co 2+ , Cu 2+ , Ca 2+ Mg 2+ , Ba 2+ and Zn 2+ One or more of the .

2. The positive electrode material according to claim 1, characterized in that The carbon source of the carbon material is selected from carbon nanotubes, carbon fibers, graphene, reduced graphene oxide, conductive carbon black or MXene.

3. The positive electrode material according to claim 1 or 2, characterized in that The mass fraction of the carbon material is 0.1-10 wt%.

4. The positive electrode material according to claim 1 or 2, characterized in that The positive electrode material satisfies at least one of the following characteristics: y = 0 and 0 < z ≤ 0.1; 0 < y ≤ 0.17 and 0 < z ≤ 0.1; 1.3 ≤ x + y ≤ 1.7; The ratio between the sum of the contents of Na and A and the sum of the contents of Fe and B is greater than or equal to 1.1 and less than or equal to 1.

7.

5. A positive electrode material according to claim 1 or 2, characterized in that: The positive electrode material satisfies at least one of the following characteristics: 1.3 ≤ x + y ≤ 1.5; The ratio between the sum of the contents of Na and A and the sum of the contents of Fe and B is greater than or equal to 1.3 and less than or equal to 1.

5.

6. The positive electrode material according to claim 3, characterized in that The carbon nanotube is a seamless nanoscale tube formed by curling single-layer or multi-layer graphite sheets around a central axis at a certain helix angle.

7. The method for preparing a positive electrode material according to any one of claims 1 to 6, characterized in that: The preparation method includes: S11: Mixing the sulfate of A and / or B with Na2SO4, FeSO4 and a carbon source to obtain a precursor material; S12: Performing pressing treatment and sintering treatment on the precursor material to obtain the positive electrode material.

8. The preparation method according to claim 7, characterized in that: Step S11 satisfies at least one of the following characteristics: In step S11, the mixing treatment method includes at least one of a jet mill and a vibration mill; The sulfate of A and / or B is a hydrated sulfate or an anhydrous sulfate.

9. The preparation method according to claim 7, characterized in that: Step S12 satisfies at least one of the following characteristics: The pressure of the pressing treatment is 0.01-2 GPa, and the pressing time is 0.1-60 min; The pressing treatment refers to pressing and granulating the precursor material; The temperature of the sintering treatment is 300-400 °C, the sintering time is 0.1-72 h, and the sintering atmosphere is an inert atmosphere.

10. A positive electrode sheet, comprising a positive electrode active material layer, characterized in that: The positive electrode active material layer contains the positive electrode material according to any one of claims 1-7.

11. A sodium ion battery, characterized in that: Including the positive electrode plate according to claim 10.

12. The sodium ion battery according to claim 11, characterized in that The sodium ion battery is a button battery, a soft package battery, a cylindrical battery or a square battery.

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