Positive electrode material for sodium ion batteries, its manufacturing method, and applications

Abstract

The present invention relates to the technical field of sodium ion batteries, in particular to a cathode material for sodium ion batteries and its manufacturing method and application. The cathode material for sodium ion batteries of the present invention includes the steps of (A) grinding a mixture of sodium borohydride and ferromanganese hydroxide to obtain a first slurry, which is spray-dried and calcined to obtain a first calcined product, and (B) grinding a mixture of the first calcined product, a carbon source, a vanadium source, sodium bicarbonate and water to obtain a second slurry, which is spray-dried, calcined, crushed, sieved and iron-removed in order to obtain the cathode material for sodium ion batteries. The method has simple steps and low cost, and the produced cathode material for sodium ion batteries has the characteristics of good conductivity, high capacity, high energy density and the like.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to a Chinese patent application bearing application number 202210905141.2 and entitled "Positive electrode material for sodium ion batteries, manufacturing method thereof, and application thereof," filed with the China Patent Office on July 29, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to the technical field of sodium ion batteries, and in particular to a positive electrode material for sodium ion batteries, its manufacturing method, and applications. [Background technology]

[0003] The explosive growth in automobile production capacity has led to a surge in the price of lithium resources. Lithium batteries also use another rare metal, cobalt (Co), in addition to lithium. Research has shown that using current technology, approximately 20 kg of lithium and 40 kg of cobalt are required to produce one pure electric vehicle (EV). Scarce energy resources like lithium and cobalt inevitably face resource depletion and rising prices. Sodium, the second lightest metallic element after lithium, is present in an abundance of 2.3-2.8%, four to five orders of magnitude more than lithium. Its physicochemical properties are similar to those of lithium. Therefore, sodium-ion batteries have attracted widespread attention.

[0004] As early as the 1970s and 1980s, sodium-ion batteries, known as "post-lithium batteries," were proposed and put into practical use almost simultaneously with lithium-ion batteries. However, as the commercialization of lithium-ion batteries became more successful, research into sodium-ion batteries gradually became less important.

[0005] At the time, the electrode materials that had been successfully applied to lithium-ion batteries were simply applied to sodium-ion batteries without considering the differences in the requirements for material lattice structure between sodium-ion batteries and lithium-ion batteries, resulting in low performance of sodium-ion batteries.In recent years, the shortage of lithium resources due to the large-scale application of lithium-ion batteries has gradually been recognized, and as electrode materials are carefully designed based on the characteristics of sodium-ion batteries to achieve better performance, sodium-ion batteries have once again become a research hotspot.

[0006] Currently, layered sodium oxide battery materials have the advantage of high energy density but poor cycling performance, while Prussian blue-based sodium battery materials have too low energy density, are structurally unstable, and contain toxic and harmful raw materials, while polyanionic sodium battery materials have the advantages of structural stability and long cycling life, but generally have low capacity and energy density.

[0007] It is in light of this that the present invention is proposed. Summary of the Invention [Means for solving the problem]

[0008] A first object of the present invention is to provide a method for manufacturing a positive electrode material for a sodium ion battery, which involves simple steps, is low cost, and provides a positive electrode material for a sodium ion battery having characteristics such as good conductivity, high capacity, and high energy density.

[0009] A second object of the present invention is to provide a positive electrode material for a sodium ion battery produced by the above-mentioned method for producing a positive electrode material for a sodium ion battery.

[0010] A third object of the present invention is to provide a sodium ion battery containing the above positive electrode material for a sodium ion battery.

[0011] In order to achieve the above object of the present invention, the following technical solutions are particularly adopted: The present invention provides a method for producing a cathode material for a sodium-ion battery, the method comprising: (A) grinding a mixture of sodium borohydride and ferromanganese hydroxide to obtain a first slurry, which is then spray-dried and calcined to obtain a first calcined product; (B) grinding a mixture of the first fired product, a carbon source, a vanadium source, sodium bicarbonate, and water to obtain a second slurry, which is then spray-dried, fired, pulverized, sieved, and iron-removed in this order to obtain the positive electrode material for a sodium-ion battery.

[0012] The present invention further provides a positive electrode material for a sodium ion battery produced by the above-mentioned method for producing a positive electrode material for a sodium ion battery.

[0013] The present invention further provides a sodium ion battery comprising the above-mentioned positive electrode material for a sodium ion battery. [Effects of the Invention]

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: In the method for producing a positive electrode material for a sodium ion battery provided by the present invention, the ionic conductivity and electronic conductivity can be significantly improved by doping with metal ions and coating with sodium vanadate and carbon, and the primary particle size of the positive electrode material for a sodium ion battery can be appropriately increased, thereby improving the compaction density and resistance to oxygen and moisture. The energy density of the positive electrode material for a sodium ion battery produced thereby is close to that of lithium iron phosphate material, reaching 170Wh / kg, and is also cheaper than lithium iron phosphate material.

[0015] The positive electrode material for sodium ion batteries produced by the method for producing a positive electrode material for sodium ion batteries of the present invention has a polyanionic sodium battery material, i.e., manganese iron sodium borate, as its core, and the surface of the polyanionic sodium battery material is simultaneously coated with sodium vanadate and carbon, thereby forming a single protective layer. This sodium vanadate can protect the polyanionic sodium battery core from contact with oxygen and moisture, which helps to improve ionic conductivity, electronic conductivity, capacity, and cycle performance, and carbon can further improve electronic conductivity, so that the positive electrode material for sodium ion batteries has excellent electrochemical performance. [Brief explanation of the drawings]

[0016] In order to more clearly describe the specific embodiments of the present invention or the technical solutions of the prior art, the following briefly introduces drawings necessary for describing the specific embodiments or the prior art. Obviously, the drawings described below are only some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative efforts. [Figure 1] 1 is an SEM image of ferromanganese (II) hydroxide prepared in Example 1 of the present invention. [Figure 2] 1 is an SEM image of a first fired product prepared in Example 1 of the present invention. [Figure 3] 1 is a SEM image of the sprayed material prepared in Example 1 of the present invention. [Figure 4] 1 is a SEM image of the positive electrode material for a sodium ion battery prepared in Example 1 of the present invention. [Figure 5] FIG. 2 is a schematic diagram showing the relationship between the capacity retention rate and the number of cycles of the positive electrode material for a thorium ion battery produced in Example 1 of the present invention. [Figure 6] 1 is a graph showing the charge and discharge curves of the positive electrode material for a thorium ion battery prepared in Example 1 of the present invention. [Figure 7] FIG. 2 is a schematic diagram of the DC resistance of the positive electrode material for a thorium ion battery produced in Example 1 of the present invention at a remaining capacity of 50%. DETAILED DESCRIPTION OF THE INVENTION

[0017] The following clearly and completely describes the technical solutions of the present invention in combination with drawings and specific embodiments. However, those skilled in the art should understand that the examples described below are only a part of the examples of the present invention, but are not all of the examples, and are only for illustrating the present invention and should not be considered as limiting the scope of the present invention.

[0018] Based on the examples of the present invention, all other examples that a person skilled in the art can obtain without any creative effort fall within the scope of protection of the present invention. If no specific conditions are specified in the examples, they shall be in accordance with conventional conditions or conditions recommended by the manufacturer. Reagents or equipment without a manufacturer's name are all conventional products available on the market.

[0019] Hereinafter, the positive electrode material for a sodium ion battery according to the embodiment of the present invention, its manufacturing method, and applications will be specifically described.

[0020] In some embodiments of the present invention, a method for producing a cathode material for a sodium-ion battery is provided, the method comprising: (A) grinding a mixture of sodium borohydride and ferromanganese hydroxide to obtain a first slurry, which is then spray-dried and calcined to obtain a first calcined product; (B) grinding a mixture of the first fired product, a carbon source, a vanadium source, a sodium source, and water to obtain a second slurry, which is then spray-dried, fired, pulverized, sieved, and iron-removed in that order to obtain a positive electrode material for a sodium-ion battery.

[0021] In the method for producing a positive electrode material for a sodium-ion battery provided by the present invention, sodium borohydride and ferromanganese (II) hydroxide are used to produce a first calcined product, i.e., sodium iron manganese borate (Na(Fe,Mn)BO), and sodium borohydride is used as a boron source and a sodium source, and sodium borohydride is used as a reducing agent, The oxidation of manganese ions and ferrous ions can be avoided, high-purity manganese iron sodium borate can be obtained, and uniform doping of ferromanganese can be achieved. The produced manganese iron sodium borate is then mixed with components such as a carbon source, a vanadium source, and a sodium source, and the mixture is polished, spray-dried, and calcined. After that, sodium vanadate and carbon are simultaneously coated on the surface of the manganese iron sodium borate, thereby forming a protective layer. This protects the polyanionic sodium battery material, i.e., the sodium vanadate coated on the surface of the manganese iron sodium borate, from contact with oxygen and moisture. At the same time, the sodium vanadate has the characteristics of good ionic conductivity and electronic conductivity, high capacity, and excellent cycle performance. The carbon coated on the surface of the polyanionic sodium battery material can further improve the electronic conductivity, resulting in the produced sodium-ion battery positive electrode material having excellent electrochemical performance.

[0022] In the method for producing a positive electrode material for a sodium ion battery provided by the present invention, the voltage platform, ionic conductivity, and electronic conductivity can be improved by doping with manganese and coating with sodium vanadate and carbon, and the primary particle size of the positive electrode material for a sodium ion battery can be appropriately increased, thereby improving the compaction density and further improving the resistance to oxygen and moisture. The positive electrode material for a sodium ion battery produced thereby has the characteristics of high capacity and high energy density, and its energy density is close to that of lithium iron phosphate material, and its cost is also significantly lower than that of lithium iron phosphate material.

[0023] Calculated based on the current prices of various raw materials, the raw material cost, energy consumption, equipment depreciation cost, and labor cost of the sodium ion battery positive electrode material of the present invention is approximately 39,500 yuan / ton in total, while the raw material cost, energy consumption, equipment depreciation cost, and labor cost of the lithium iron phosphate material are approximately 132,000 yuan / ton in total. Therefore, the production cost of the sodium ion battery positive electrode material of the present invention is significantly lower than the production cost of the lithium iron phosphate material.

[0024] In some embodiments of the present invention, in step (A), the firing comprises heating the mixture in a nitrogen atmosphere to 400-500°C and maintaining the temperature for 4-5 hours, then heating the mixture to 650-700°C and maintaining the temperature for 3-5 hours, and then cooling the mixture to 120°C or less, and preferably the relative humidity during firing is 3%-5%.

[0025] In some specific embodiments of the present invention, in step (A), the firing includes heating the material in a nitrogen atmosphere to 400-500°C at a rate of 1-3°C / min, maintaining the temperature for 4-5 hours, then heating the material to 650-700°C at a rate of 1-3°C / min, maintaining the temperature for 3-5 hours, and then cooling the material to 120°C or less at a rate of 1-3°C / min to finish the firing.

[0026] In the method for producing a positive electrode material for a sodium ion battery of the present invention, nitrogen having a certain humidity is used as a protective gas and a reactant in the calcination process, which can react with sodium borohydride to obtain a reducing gas, thereby protecting the manganese ions and ferrous ions from being oxidized.

[0027] In some embodiments of the present invention, in step (A), a mixture of sodium borohydride and ferromanganese hydroxide is polished to obtain a first slurry. Preferably, the concentration of the aqueous sodium borohydride solution is 1 to 1.5 mol / L.

[0028] In some embodiments of the present invention, in step (A), the ratio of the sum of the moles of Fe and Mn in the ferromanganese(II) hydroxide to the moles of Na in the sodium borohydride is 0.97 to 1.02:1, and is typical but not limited to, for example, the ratio of the sum of the moles of Fe and Mn in the ferromanganese(II) hydroxide to the moles of Na in the sodium borohydride is 0.97:1, 0.98:1, 0.99:1, 1:1, 1.01:1, or 1.02:1.

[0029] In some embodiments of the present invention, in step (A), the particle size of the first slurry is 200 to 300 nm, and is typical but not limited to, for example, in step (A), the particle size of the first slurry is 200 nm, 220 nm, 240 nm, 260 nm, 280 nm, or 300 nm.

[0030] In some embodiments of the present invention, in step (A), the method for producing ferromanganese(II) hydroxide comprises: The method comprises the step of reacting a manganese salt, a ferrous salt, a complexing agent, sodium hydroxide, hydrazine hydrate, aqueous ammonia, and titanyl sulfate in an aqueous phase to obtain ferric manganese (II) hydroxide.

[0031] The present invention produces ferromanganese hydroxide in which ferromanganese is uniformly coprecipitated by coprecipitation, and then reacts it with sodium borohydride to achieve uniform doping of ferromanganese, thereby avoiding the separate presence of sodium manganese borate concentrate at specific locations, which would otherwise cause a reduction in capacity.

[0032] In some embodiments of the present invention, in the method for producing ferromanganese (II) hydroxide, the reaction temperature is 50 to 60° C., and the reaction time is 15 to 150 minutes.

[0033] In some embodiments of the present invention, in the method for producing ferromanganese hydroxide, the molar ratio of Mn in the manganese salt to Fe in the ferrous salt is 1:1.5 to 1:4, and typical but non-limiting examples of the molar ratio of Mn in the manganese salt to Fe in the ferrous salt include 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, or 1:4.

[0034] In some embodiments of the present invention, in the method for producing ferromanganese hydroxide, the ratio of the sum of the moles of Mn in the manganese salt and Fe in the ferrous salt to the number of moles of Ti in titanyl sulfate is 100:0.1-0.2.

[0035] In some embodiments of the present invention, in the method for producing ferromanganese hydroxide, the molar ratio of manganese salt, complexing agent, sodium hydroxide, hydrazine hydrate, and NH3·H2O in aqueous ammonia is 1:0.01-0.1:5.5-10.5:0.01-0.1:0.05-0.5.

[0036] In some embodiments of the present invention, in the method for producing ferromanganese hydroxide, the ratio of the sum of the mass of the manganese salt, the ferrous salt, the complexing agent, sodium hydroxide, hydrazine hydrate, aqueous ammonia, and titanyl acid to the mass of water is 10:1.5-3.

[0037] In some embodiments of the present invention, the method for producing ferromanganese hydroxide includes at least one of manganese sulfate, manganese chloride, and manganese acetate; the ferrous salt includes at least one of ferrous sulfate, ferrous chloride, and ferrous acetate; and the complexing agent includes at least one of ethylenediaminetetraacetic acid (EDTA), disodium ethylenediaminetetraacetic acid, sodium hexametaphosphate, and triethanolamine.

[0038] In some specific embodiments of the present invention, in the method for producing ferromanganese (II) hydroxide, the concentration of aqueous ammonia is 5 to 8 mol / L.

[0039] In some specific embodiments of the present invention, the method for producing ferromanganese(II) hydroxide comprises: The method includes slowly adding a mixed solution of manganese salt, ferrous salt, complexing agent, sodium hydroxide, hydrazine hydrate, ammonia water, titanyl sulfate, and water to a reaction vessel until the pH of the mixed solution is 9.5-10. The temperature is controlled at 50°C during the addition, and after the addition is complete, the reaction is continued for 15-30 minutes at 50-60°C, and the free ammonia concentration of the mixed solution is controlled at 8-12 g / L during the reaction. During the reaction, the ammonia water and metal ions precipitate, resulting in ammonium radicals (not free ammonia). At the same time, some of the ammonia volatilizes. Therefore, the amount of ammonia water added must be continuously adjusted to control the free ammonia in the solution.

[0040] In some embodiments of the present invention, in step (B), the vanadium source comprises ammonium metavanadate.

[0041] In some embodiments of the present invention, in step (B), the sodium source comprises at least one of sodium bicarbonate, sodium hydroxide, sodium acetate, and sodium nitrate, preferably, the sodium source comprises sodium bicarbonate.

[0042] In some embodiments of the present invention, in step (B), the carbon source comprises nanohydrophilic graphite and / or polyethylene glycol, and preferably, the mass ratio of nanohydrophilic graphite to polyethylene glycol is 1:5-10.

[0043] In the method for producing a positive electrode material for a sodium-ion battery provided by the present invention, the conductivity of the coating layer can be significantly improved by adding an inorganic carbon source before calcination in step (B). Conventional carbon obtained by pyrolysis of organic carbon sources is amorphous carbon with a very low degree of graphitization and lower conductivity than graphitized carbon. However, in the present invention, the inorganic carbon source is directly introduced and polyethylene glycol is simultaneously added to achieve dispersion. The polyethylene glycol is also pyrolyzed in the secondary calcination process to obtain carbon, thereby achieving a composite of the inorganic and organic carbon sources. The organic carbon source forms a carbon network and bonds with the inorganic carbon source, thereby solving the problem of uneven coverage of the inorganic carbon source in the coating layer.

[0044] In some embodiments of the present invention, in step (B), the molar ratio of sodium in the first calcined product, vanadium in the vanadium source, and sodium in the sodium source is 1:0.02-0.03:0.06-0.09.

[0045] In some embodiments of the present invention, in step (B), the mass ratio of the carbon source to the first calcined product is 3 to 10:100, and preferably the mass ratio of the carbon source to the first calcined product is 5 to 8:100.

[0046] In some embodiments of the present invention, in step (B), the ratio of the total mass of the first calcined product, the carbon source, the vanadium source, and the sodium source to the mass of water is 1:2-3.

[0047] In some embodiments of the present invention, in step (B), the firing comprises increasing the temperature to 720 to 750°C in a nitrogen atmosphere, maintaining the temperature for 2 to 4 hours, and then cooling to 80°C or below. Preferably, in step (B), the firing comprises increasing the temperature to 720 to 750°C at a rate of 1 to 3°C / min in a nitrogen atmosphere, maintaining the temperature for 2 to 4 hours, and then cooling to 80°C at a rate of 1 to 3°C / min.

[0048] In some embodiments of the present invention, in step (B), the particle size of the second slurry is 100 to 200 nm.

[0049] In some embodiments of the present invention, in step (B), the particle size of the second slurry after spray drying is 5 to 10 μm, and preferably, a pressurized spray dryer is used for spray drying.

[0050] In some embodiments of the present invention, in step (B), the pulverization includes pulverization using an airflow pulverizer, preferably until the particle size of the second slurry after spray drying is 0.5 to 2 μm, more preferably, the pulverization temperature is 120 to 150°C, the pulverization pressure is 0.25 to 0.5 MPa, and the pulverization includes pulverization in a nitrogen atmosphere.

[0051] In some embodiments of the present invention, in step (B), sieving includes sieving with an ultrasonic vibrating sieve of 100 to 200 mesh.

[0052] In some embodiments of the present invention, in step (B), removing iron comprises removing iron using an electromagnetic iron remover to a magnetic material of ≦1 ppm in the second slurry after milling.

[0053] In some embodiments of the present invention, there is also provided a positive electrode material for a sodium ion battery produced by the above-described method for producing a positive electrode material for a sodium ion battery.

[0054] In some embodiments of the present invention, the primary particle size of the sodium ion battery positive electrode material is 150 to 250 nm.

[0055] The positive electrode material for a sodium ion battery of the present invention is configured so that it has a surface made of layered oxide sodium vanadate and carbon, a core made of a polyanionic sodium battery material, and a surface of the polyanionic sodium battery material coated with sodium vanadate and carbon to form a single protective layer.

[0056] In some embodiments of the present invention, a sodium-ion battery including the above-described positive electrode material for a sodium-ion battery is also provided.

[0057] Example 1 The method for preparing a positive electrode material for a sodium ion battery provided by this embodiment includes the following steps: (A) A 1.3 mol / L aqueous solution of sodium borohydride and ferromanganese (II) hydroxide are mixed, and the mixture is added to a sand mill for sanding to obtain a first slurry with a particle size of 252 nm. The first slurry is then spray-dried, and then in nitrogen at a relative humidity of 4.1%, the temperature is first raised to 450°C at a rate of 3°C / min and kept at that temperature for 5 hours, then raised to 680°C at a rate of 2°C / min and kept at that temperature for 4 hours, and then cooled to 120°C at a rate of 3°C / min, and finished to obtain a first fired product.

[0058] Here, the ratio of the sum of the moles of Mn and Fe in ferromanganese (II) hydroxide to the moles of sodium borohydride is 1.01:1.

[0059] The method for producing ferromanganese (II) hydroxide is as follows: a mixture of manganese sulfate, ferrous sulfate, EDTA, sodium hydroxide, aqueous ammonia (concentration: 6 mol / L), hydrazine hydrate, titanyl sulfate, and deionized water is added to a reactor, and the molar ratio of NH3·H2O in the manganese sulfate, ferrous sulfate, EDTA, sodium hydroxide, hydrazine hydrate, and aqueous ammonia is 1:2.52:0.05:7.58:0.04:0.18, and the molar ratio of Mn in manganese sulfate to Fe in ferrous sulfate to titanyl sulfate is 1:2.52:0.05:7.58:0.04:0.18. The molar ratio of Ti to Ti is 100:0.2, the addition time is 95 min, the pH of the mixed solution during the addition is 9.76, the stirring speed is 500 r / min, and the temperature is 55°C. After the addition is completed, the reaction is continued at 55°C for 25 min to obtain a reaction solution, and the concentration of free ammonia in the solution is controlled at 10 g / L during the reaction. The reaction solution is filtered to obtain a filter cake, which is washed with 0.015 mol / L hydrazine hydrate and dried in a vacuum oven to obtain ferromanganese(II) hydroxide.

[0060] (B) The first calcined product, carbon source, ammonium metavanadate, sodium bicarbonate, and water were mixed and added to a sand mill for sanding to obtain a second slurry with a particle size of 183 nm. The second slurry was spray-dried in a pressure spray dryer to obtain a spray material with a particle size of 8.7 μm. In a nitrogen atmosphere, the spray material was first heated to 735°C at a rate of 3°C / min and held at that temperature for 3 hours, then cooled to 80°C at a rate of 3°C / min, and finished to obtain a second calcined product. The second calcined product was then pulverized at 145°C in a nitrogen atmosphere at a pressure of 0.35 MPa until the particle size of the second calcined product was 1.2 μm. Next, iron was removed using a 150-mesh ultrasonic vibrating sieve and then an electromagnetic iron remover until the magnetic substance content in the second calcined product was 0.21 ppm, and the product was vacuum-packed to obtain a positive electrode material for a sodium-ion battery.

[0061] Here, the carbon source was nanohydrophilic graphite and polyethylene glycol in a mass ratio of 1:7, the molar ratio of sodium in the first-calcined product, vanadium in ammonium metavanadate, and sodium bicarbonate was 1:0.025:0.08, the mass ratio of the carbon source to the first-calcined product was 6:100, and the ratio of the total mass of the first-calcined product, carbon source, ammonium metavanadate, and sodium bicarbonate to the mass of water was 1:2.5.

[0062] Example 2 The method for producing a positive electrode material for a sodium ion battery of this embodiment includes the following steps: (A) A 1 mol / L aqueous solution of sodium borohydride and ferromanganese (II) hydroxide are mixed and added to a sand mill for sanding to obtain a first slurry with a particle size of 200 nm. The first slurry is then spray-dried and, in a nitrogen atmosphere with a relative humidity of 3%, first heated to 400°C at a rate of 1.5°C / min and kept at that temperature for 5 hours, then heated to 650°C at a rate of 1°C / min and kept at that temperature for 5 hours, and then cooled to 120°C at a rate of 3°C / min, and finished to obtain a first fired product.

[0063] Here, the ratio of the sum of the moles of Mn and Fe in ferromanganese (II) hydroxide to the moles of sodium borohydride is 0.97:1.

[0064] The method for producing ferromanganese (II) hydroxide is as follows: a mixed solution of manganese chloride, ferrous sulfate, EDTA, sodium hydroxide, aqueous ammonia (concentration: 5 mol / L), hydrazine hydrate, titanyl sulfate, and deionized water is added to a reactor, and the molar ratio of NH3·H2O in the manganese chloride, ferrous sulfate, EDTA, sodium hydroxide, hydrazine hydrate, and aqueous ammonia is 1:1.5:0.01:5.5:0.01:0.05, and the molar ratio of Mn in the manganese chloride and Fe in the ferrous sulfate is 1:1.5:0.01:5.5:0.01:0.05. The molar ratio of Ti in the mixture is 100:0.1, the addition time is 60 min, the pH of the mixed solution during the addition is 9.6, the stirring speed is 600 r / min, and the temperature is 60°C. After the addition is completed, the reaction is continued at 60°C for 30 min to obtain a reaction solution, and the concentration of free ammonia in the solution is controlled to 10 g / L during the reaction. The reaction solution is filtered to obtain a filter cake, which is washed with 0.01 mol / L of hydrazine hydrate and dried in a vacuum oven to obtain ferromanganese(II) hydroxide.

[0065] (B) The first calcined product, carbon source, ammonium metavanadate, sodium bicarbonate, and water are mixed and added to a sand mill for sanding to obtain a second slurry with a particle size of 100 nm. The second slurry is spray-dried in a pressure spray dryer to obtain a spray material with a particle size of 5 μm. In a nitrogen atmosphere, the spray material is first heated to 720°C at a rate of 3°C / min and held at that temperature for 2 hours, then cooled to 80°C at a rate of 3°C / min, and finished to obtain a second calcined product. The second calcined product is then pulverized at 145°C in a nitrogen atmosphere at a pressure of 0.35 MPa until the particle size of the second calcined product is 1.1 μm. Next, iron is removed using a 150-mesh ultrasonic vibrating sieve and then an electromagnetic iron remover until the magnetic material in the second calcined product is 0.3 ppm, and the product is vacuum-packed to obtain a positive electrode material for a sodium-ion battery.

[0066] Here, the carbon source was nanohydrophilic graphite and polyethylene glycol in a mass ratio of 1:5, the molar ratio of sodium in the first fired product, vanadium in ammonium metavanadate, and sodium bicarbonate was 1:0.02:0.06, the mass ratio of the carbon source to the first fired product was 3:100, and the ratio of the total mass of the first fired product, carbon source, ammonium metavanadate, and sodium bicarbonate to the mass of water was 1:2.

[0067] Example 3 The method for producing a positive electrode material for a sodium ion battery of this embodiment includes the following steps: (A) A 1.5 mol / L aqueous solution of sodium borohydride and ferromanganese (II) hydroxide are mixed and added to a sand mill for sanding to obtain a first slurry with a particle size of 300 nm. The first slurry is then spray-dried and, in nitrogen at a relative humidity of 5%, first heated to 500°C at a rate of 3°C / min and kept at that temperature for 5 hours, then heated to 700°C at a rate of 1°C / min and kept at that temperature for 4 hours, and then cooled to 120°C at a rate of 1°C / min, and finished to obtain a first fired product.

[0068] Here, the ratio of the sum of the moles of Mn and Fe in ferromanganese (II) hydroxide to the moles of sodium borohydride is 1.02:1.

[0069] The method for producing ferromanganese (II) hydroxide is as follows: a mixture of manganese acetate, ferrous chloride, triethanolamine, sodium hydroxide, aqueous ammonia (concentration: 8 mol / L), hydrazine hydrate, titanyl sulfate, and deionized water is added to a reaction vessel, and the molar ratio of NH3·H2O in the manganese acetate, ferrous chloride, triethanolamine, sodium hydroxide, hydrazine hydrate, and aqueous ammonia is 1:4:0.1:10.5:0.1:0.5, and the molar ratio of the sum of Mn in the manganese chloride and Fe in the ferrous sulfate to the titanyl sulfate is 1:4:0.1:10.5:0.1:0.5. the molar ratio of Ti to Ti is 100:0.2, the addition time is 120 min, the pH of the mixed solution during the addition is 9.9, the stirring speed is 550 r / min, and the temperature is 50°C, and after the addition is completed, the reaction is continued at 50°C for 25 min to obtain a reaction solution, and the concentration of free ammonia in the solution is controlled at 10 g / L during the reaction; and the reaction solution is filtered to obtain a filter cake, which is washed with 0.015 mol / L hydrazine hydrate and dried in a vacuum oven to obtain ferromanganese(II) hydroxide.

[0070] (B) The first calcined product, carbon source, ammonium metavanadate, sodium bicarbonate, and water are mixed and added to a sand mill for sanding to obtain a second slurry with a particle size of 200 nm. The second slurry is spray-dried in a pressure spray dryer to obtain a spray material with a particle size of 10 μm. In a nitrogen atmosphere, the spray material is first heated to 750°C at a rate of 3°C / min and held at that temperature for 3 hours, then cooled to 80°C at a rate of 3°C / min, and finished to obtain a second calcined product. The second calcined product is then pulverized at 145°C in a nitrogen atmosphere at a pressure of 0.35 MPa until the particle size of the second calcined product is 1.3 μm. Next, iron is removed using a 150-mesh ultrasonic vibrating sieve and then an electromagnetic iron remover until the magnetic substance content in the second calcined product is 0.2 ppm, and the product is vacuum-packed to obtain a positive electrode material for a sodium-ion battery.

[0071] Here, the carbon source was nanohydrophilic graphite and polyethylene glycol in a mass ratio of 1:10, the molar ratio of sodium in the first fired product, vanadium in ammonium metavanadate, and sodium bicarbonate was 1:0.03:0.09, the mass ratio of the carbon source to the first fired product was 10:100, and the ratio of the total mass of the first fired product, carbon source, ammonium metavanadate, and sodium bicarbonate to the mass of water was 1:3.

[0072] Comparative Example 1 The manufacturing method of the positive electrode material for sodium ion batteries provided by this comparative example is different from Example 1 only in that ammonium metavanadate is not added in step (B).

[0073] Test Example 1 The ferromanganese (II) hydroxide prepared in Example 1 was subjected to a scanning test, the results of which are shown in FIG.

[0074] As can be seen from FIG. 1, the ferromanganese (II) hydroxide produced by the present invention is a flocculent aggregate that is spherical, has a large specific surface area, a small primary particle size, and is highly reactive.

[0075] The properties of the ferromanganese (II) hydroxide produced in Example 1 were tested and the results are shown in Table 1.

[0076] [Table 1]

[0077] Test Example 2 A scanning test was conducted on the first fired product produced in Example 1, and the results are shown in Figure 2. A test was conducted on the properties of the first fired product produced in Example 1, and the results are shown in Table 2. The compacted density is the density of the powder product at 3T pressure.

[0078] [Table 2]

[0079] Test Example 3 The sprayed material produced in Example 1 was subjected to a scanning test, the results of which are shown in Figure 3. The positive electrode material for a sodium ion battery produced in Example 1 was subjected to a scanning test, the results of which are shown in Figure 4. The properties of the positive electrode material for a sodium ion battery produced in Example 1 were tested, the results of which are shown in Table 3. The compacted density is the density of the powder product at a pressure of 3T.

[0080] [Table 3]

[0081] The positive electrode material for sodium ion batteries prepared in Example 1 and the positive electrode material for sodium ion batteries prepared in Comparative Example 1 were each manufactured using carbon-coated aluminum foil as a current collector, sodium hexafluorophosphate as an electrolyte, and hard carbon as an anode to manufacture a 3 Ah soft-pack battery. A cycle performance test was conducted at 25°C and 1C magnification.

[0082] Figure 5 is a schematic diagram of the relationship between the capacity retention rate and the number of cycles of the positive electrode material for a thorium-ion battery produced in Example 1. Figure 6 is a graph showing the charge / discharge curves of the positive electrode material for a thorium-ion battery produced in Example 1, where A1 and A are charge / discharge curves at a 0.2C multiplication factor, and B1 and B are charge / discharge curves at a 1C multiplication factor. Next, the direct current resistance (DCR) at 50% SOC (residual capacity 50%) was measured, where the discharge multiplication factor was 2C and the battery was 3 Ah. A represents two parallel experiments conducted on the first battery produced, and D represents two parallel experiments conducted on the second battery produced with the same material. The results are shown in Figure 7.

[0083] As can be seen from Figure 5, the positive electrode material for a sodium ion battery of the present invention has excellent cycle performance, with a capacity retention rate of ≥ 95% after 500 cycles at 1 C. As can be seen from Figure 6, the positive electrode material for a sodium ion battery of the present invention has a high capacity of approximately 118 mAh / g at 1 C, while the positive electrode material for a sodium ion battery of Comparative Example 1 has a capacity retention rate of only 91% after 500 cycles at 1 C and a discharge capacity of only 110.5 mAh / g at 1 C.

[0084] As can be seen from Figure 7, all DCRs are low at 16 mΩ.

[0085] As can be seen from Table 3 and Figures 5-7, the positive electrode material for sodium ion batteries of the present invention has a high compaction density of 2.37 g / mL, and the expected electrode sheet can reach a compaction density of 2.45 g / mL or more when used. Furthermore, the positive electrode material for sodium ion batteries of the present invention has excellent cycle performance, large capacity, and a high voltage platform. At the same time, calculations show that the cost of the positive electrode material for sodium ion batteries of the present invention is less than 30% of the cost of lithium iron phosphate, making it very cost-effective and suitable for applications such as motorcycles, electric buses, and short-range electric vehicles.

[0086] Finally, it should be noted that the above embodiments are only for illustrating the technical solutions of the present invention, and are not intended to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should still understand that the technical solutions described in the above embodiments can be modified or equivalently replaced with some or all of the technical features therein, and such modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for producing a positive electrode material for a sodium ion battery, comprising: (A) grinding a mixture of sodium borohydride and ferromanganese hydroxide to obtain a first slurry, which is then spray-dried and calcined to obtain a first calcined product; (B) grinding the mixture of the first fired product, a carbon source, a vanadium source, a sodium source, and water to obtain a second slurry, which is then spray-dried, fired, pulverized, sieved, and iron-removed in this order to obtain the sodium-ion battery positive electrode material; In step (A), the firing includes heating the material to 400°C to 500°C in a nitrogen atmosphere, maintaining the temperature for 4 hours to 5 hours, then heating the material to 650°C to 700°C, maintaining the temperature for 3 hours to 5 hours, and then cooling the material to 120°C or less; In the step (A), the ratio of the sum of the moles of Fe and Mn in the ferromanganese hydroxide to the moles of Na in the sodium borohydride is (0.97 to 1.02):1; in step (B), a molar ratio of elemental sodium in the first fired product, elemental vanadium in the vanadium source, and elemental sodium in the sodium source is 1:(0.02 to 0.03):(0.06 to 0.09); In the step (B), the mass ratio of the carbon source to the first fired product is (3 to 10):100; in the step (B), the ratio of the total mass of the first fired product, the carbon source, the vanadium source, and the sodium source to the mass of the water is 1:(2 to 3); In the step (B), the firing includes heating the material to 720°C to 750°C in a nitrogen atmosphere, maintaining the temperature for 2 hours to 4 hours, and then cooling the material to 80°C or less; The primary particle diameter of the positive electrode material for a sodium ion battery is 150 nm to 250 nm. A method for producing positive electrode materials for sodium-ion batteries.

2. 2. The method for producing a positive electrode material for a sodium ion battery according to claim 1, wherein in step (A), the relative humidity of the calcination is 3% to 5%.

3. In step (A), the particle size of the first slurry is 200 nm to 300 nm. The method for producing the positive electrode material for a sodium ion battery according to claim 1.

4. In step (A), the method for producing ferromanganese hydroxide comprises: a step of reacting a manganese salt, a ferrous salt, a complexing agent, sodium hydroxide, hydrazine hydrate, aqueous ammonia, and titanyl sulfate in an aqueous phase to obtain said ferromanganese hydroxide; The method for producing the positive electrode material for a sodium ion battery according to claim 1.

5. (1) The molar ratio of Mn in the manganese salt to Fe in the ferrous salt is 1:(1.5 to 4); (2) the ratio of the sum of the moles of Mn in the manganese salt and Fe in the ferrous salt to the number of moles of Ti in the titanyl sulfate is 100:(0.1 to 0.2); (3) the molar ratio of NH3·H2O in the manganese salt, the complexing agent, the sodium hydroxide, the hydrazine hydrate, and the ammonia water is 1:(0.01 to 0.1):(5.5 to 10.5):(0.01 to 0.1):(0.05 to 0.5); (4) The manganese salt includes at least one of manganese sulfate, manganese chloride, and manganese acetate; (5) The ferrous salt includes at least one of ferrous sulfate, ferrous chloride, and ferrous acetate; (6) The complexing agent includes at least one of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, sodium hexametaphosphate, and triethanolamine; The present invention has at least one of the following technical features: The method for producing the positive electrode material for a sodium ion battery according to claim 4.

6. (1) In step (B), the vanadium source comprises ammonium metavanadate; (2) in step (B), the sodium source comprises at least one of sodium bicarbonate, sodium hydroxide, sodium acetate, and sodium nitrate; (3) In step (B), the carbon source comprises nano-hydrophilic graphite and / or polyethylene glycol; (4) In step (B), the mass ratio of the nano-hydrophilic graphite to the polyethylene glycol is 1:(5-10); The present invention has at least one of the following technical features: The method for producing the positive electrode material for a sodium ion battery according to claim 1.

7. In step (B), (1) the particle size of the second slurry is 100 nm to 200 nm; (2) the particle size of the second slurry after spray drying is 5 μm to 10 μm; The present invention has at least one of the following technical features: The method for producing the positive electrode material for a sodium ion battery according to claim 1.

8. In step (A), the firing comprises heating the mixture in a nitrogen atmosphere to 400°C to 500°C at a rate of 1°C / min to 3°C / min, maintaining the temperature for 4 hours to 5 hours, then heating the mixture to 650°C to 700°C at a rate of 1°C / min to 3°C / min, maintaining the temperature for 3 hours to 5 hours, and then cooling the mixture to 120°C or less at a rate of 1°C / min to 3°C / min to obtain a positive electrode material. The method for producing the positive electrode material for a sodium ion battery according to claim 1.

9. The reaction temperature is 50°C to 60°C, and the reaction time is 15 min to 150 min. The method for producing the positive electrode material for a sodium ion battery according to claim 4.

10. In step (B), the firing comprises heating the mixture in a nitrogen atmosphere to 720°C to 750°C at a rate of 1°C / min to 3°C / min, maintaining the temperature for 2 hours to 4 hours, and then cooling the mixture to 80°C or less at a rate of 1°C / min to 3°C / min. The method for producing the positive electrode material for a sodium ion battery according to claim 8.

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