A sodium-ion battery positive electrode material and a preparation method and application thereof

Abstract

The application discloses a sodium ion battery positive electrode material and a preparation method and application thereof. The sodium carbonate is embedded into the gap of a precursor through multiple times of soaking of a sodium carbonate saturated solution with the precursor, and the sodium carbonate and the precursor are more fully fused in a sintering process, so that the positive electrode material has less surface material and is more stable. The number of times of repeated soaking will affect the content of sodium in the hydroxide, the content of sodium in the hydroxide is low when the number of times of repeated soaking is small, the capacity of the sample after sintering is low, the content of sodium in the hydroxide is high when the number of times of repeated soaking is large, the capacity of the sample after sintering is slightly low, and the residual alkali content of the material is high.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sodium ion batteries, and particularly relates to a sodium ion battery positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] In recent years, sodium ion batteries have attracted widespread attention and research due to their excellent electrical performance, safety performance, abundant sodium resources, and cost advantages. Oxide positive electrode materials, as core materials of sodium ion batteries, are considered to be one of the most promising positive electrode materials for industrialization. Oxide positive electrode materials are usually obtained by mixing a metal hydroxide precursor and sodium carbonate through high-speed stirring and then sintering at high temperature. The mixing effect of the hydroxide precursor and sodium carbonate greatly affects the performance of the positive electrode material. After sintering, the positive electrode material has poor consistency, is unstable, has a high surface residual alkali content, is prone to gelation during homogenization, and has low positive electrode capacity. To obtain a positive electrode material with good processing performance, doping and coating are usually used, and a multiple sintering process is also required, which increases energy consumption.

[0003] For example, the Chinese patent application with the publication number CN113644268A discloses a sodium ion battery layered positive electrode material and a preparation method thereof: a sodium source material and an M source material are mixed by ball milling under inert gas protection to form a powder, which is calcined at high temperature to form a Na x MO2layered material, and then ground into a composite powder. The composite powder is mixed with a doping and coating salt solution under heating and stirring until the solvent is completely volatilized to obtain a doping and coating powder. The doping and coating powder is calcined again and cooled to obtain the sodium ion battery layered positive electrode material.

[0004] There are also methods of mixing a metal element directly with a sodium salt solution through a metal etching method, but etching agents and complexing agents are required to help the combination between the metal element and the sodium salt. For example, the Chinese patent application with the publication number CN115863593A discloses a sodium ion positive electrode material, a preparation method, a positive electrode, and a battery. The general formula of the positive electrode material is Na xMeO2, wherein Me is one or more of Fe, Ni, Mn, Co, Cu, Ti, Mg, Al metal, and x is 1.02-1.20; the positive electrode material is prepared by a metal etching method through metal powder and a sodium ion saturated solution, and is prepared through metal powder and a sodium ion saturated solution, comprising the following steps: (1) adding water and a sodium-containing electrolyte into a reaction container, stirring uniformly to obtain a bottom liquid A, i.e., a sodium ion saturated solution; (2) adding an etchant and a complexing agent into the bottom liquid A of step (1) in multiple times according to a certain molar ratio, stirring uniformly to obtain a solution B; (3) adding metal powder into the solution B of step (2) in two steps for reaction, and after the reaction is completed, the reaction liquid is concentrated, aged, centrifuged and dried to obtain a sodium ion positive electrode material precursor C; (4) mixing the sodium ion positive electrode material precursor C, a sodium salt and an additive, and then sintering to obtain a sodium ion positive electrode material.

[0005] Therefore, it is of great significance to develop a positive electrode material which is simple and easy to operate, has low requirements for precursors, low energy consumption and good performance. SUMMARY

[0006] The present application provides a sodium ion battery positive electrode material, a preparation method and application thereof.

[0007] A preparation method of a sodium ion battery positive electrode material, comprising the following steps:

[0008] (1) dissolving a sodium salt in water to prepare a sodium salt saturated solution;

[0009] (2) infiltrating and dispersing a metal hydroxide precursor in the sodium salt saturated solution of step (1), filtering and collecting solid substances, and drying to obtain a mixed precursor,

[0010] The metal hydroxide precursor is Ni x Fe y Mn (1-x-y) (OH)2, wherein 0

[0011] (3) repeating the treatment of step (2) on the mixed precursor until the molar ratio of Na element to metal element in the final mixed precursor is 0.95-1:1;

[0012] (4) calcining the final mixed precursor in an oxygen atmosphere to obtain the sodium ion battery positive electrode material.

[0013] Preferably, the metal hydroxide precursor is Ni x Fe y Mn 1-x-y)(OH)2, wherein 1 / 4 < x < 1 / 3, 1 / 3 < y < 2 / 5.

[0014] In the final product, the valence states of Ni, Fe and Mn in the final product are as follows: Ni is about +2, Fe is about +3, and Mn is about +4, Ni is mainly in +2, Mn is in both +3 and +4, and Fe is mainly in +3, and a small amount of +2. In the calcination process, a small amount of Na may form residual alkali and cannot be incorporated.

[0015] Preferably, the sodium salt is at least one of the following: sodium carbonate, sodium acetate, sodium oxalate, and sodium stearate.

[0016] Preferably, the preparation method of the metal hydroxide precursor comprises the following steps:

[0017] (a) Dissolve nickel sulfate, ferrous sulfate and manganese sulfate in deionized water according to the molar ratio of metal ions to prepare a metal ion solution; dissolve NaOH or KOH in deionized water to prepare an alkaline solution; and ammonia is used as a complexing agent;

[0018] (b) Mix the metal ion solution, the alkaline solution and the complexing agent under the protection of an inert atmosphere to co-precipitate, filter, wash and dry the precipitate to obtain the metal hydroxide precursor.

[0019] Preferably, the concentration of the metal ion solution is 1.8-2.5 mol / L; the concentration of the alkaline solution is 3.6-4 mol / L, and the concentration of the complexing agent is 1-2 mol / L; and the temperature during the co-precipitation is 30-50℃.

[0020] Preferably, the temperature of the sodium salt saturated solution is maintained at 35-40℃.

[0021] Preferably, the calcination is first carried out at 500-600℃ for 3-5h, and then carried out at 850-950℃ for 10-24h. The heating rate during the calcination is 5℃ / min. The oxygen atmosphere during the calcination is air or oxygen.

[0022] The application further provides a sodium ion battery cathode material prepared by the preparation method.

[0023] The application further provides an application of the sodium ion battery cathode material in the preparation of a sodium ion battery.

[0024] The application has the following beneficial effects:

[0025] The sodium carbonate is embedded into the gaps of the precursor by multiple immersions of the sodium carbonate saturated solution and the precursor, so that the sodium carbonate and the precursor are more fully fused during the sintering process, and the surface of the cathode material is less and more stable.

[0026] The number of repeated infiltrations affects the content of sodium in the hydroxide. The fewer the repeated times, the lower the sodium content in the hydroxide, and the lower the capacity of the sample after sintering. The more the repeated times, the higher the sodium content in the hydroxide, and the lower the capacity of the sample after sintering and the higher the residual alkali content of the material. BRIEF DESCRIPTION OF DRAWINGS

[0027] Fig. 1 The first charge-discharge detection result graph of the product prepared in Example 1.

[0028] Fig. 2 The first charge-discharge detection result graph of the product prepared in Example 2.

[0029] Fig. 3 The first charge-discharge detection result graph of the product prepared in Example 3.

[0030] Fig. 4 The first charge-discharge detection result graph of the product prepared in Comparative Example 1.

[0031] Fig. 5 The first charge-discharge detection result graph of the product prepared in Comparative Example 2.

[0032] Fig. 6 The first charge-discharge detection result graph of the product prepared in Comparative Example 3.

[0033] Fig. 7 The discharge cycle test graph of the products prepared in Examples 1, 2, 3 and Comparative Examples 1, 2 and 3. DETAILED DESCRIPTION

[0034] Preparation method of metal hydroxide precursor:

[0035] Nickel sulfate, ferrous sulfate and manganese sulfate are dissolved in deionized water to prepare a metal ion solution of 1.8-2.5 mol / L. NaOH (or KOH) is dissolved in deionized water to prepare an alkaline solution of 3.6-4 mol / L, and ammonia water of 1-2 mol / L is used as a complexing agent. The metal ion solution, the alkaline solution and the complexing agent are added to a reaction kettle at a temperature of 30-50°C under the protection of inert gas and stirring to co-precipitate metal hydroxide, which is filtered, washed and dried to obtain a metal hydroxide precursor Ni x Fe y Mn (1-x-y) (OH)2, wherein 0

[0036] Example 1

[0037] In this example, the metal hydroxide precursor is Ni 1 / 3 Fe 1 / 3 Mn 1 / 3(OH)₂ is prepared by dissolving nickel sulfate, ferrous sulfate, and manganese sulfate in deionized water to prepare a 1.8 mol / L metal ion solution. NaOH is dissolved in deionized water to prepare a 4 mol / L alkaline solution, and ammonia water is used as a 2 mol / L complexing agent. The metal ion solution, alkaline solution, and complexing agent are added to a reaction vessel at 50°C under inert gas (nitrogen) protection and stirring to co-precipitate metal hydroxide. After filtration, washing, and drying, the metal hydroxide precursor is obtained. The metal hydroxide particle size D50 is 3.5 μm, and the tap density is 1.43 g / cm³. 3 .

[0038] Sodium carbonate was dissolved in water at 35°C to prepare a saturated sodium carbonate solution. A metal hydroxide precursor was impregnated and dispersed in the saturated sodium carbonate solution. The solution temperature was maintained at 35°C, and the mixture was stirred for 60 min while simultaneously undergoing ultrasonic dispersion and multiple vacuum venting processes. The solution was then filtered to obtain a filter cake. The cake was washed with cold water and then dried to obtain a mixed precursor. The process of dispersing the precursor in the saturated sodium carbonate solution, stirring, ultrasonicating, vacuum venting, filtering, washing, and drying was repeated. Finally, the temperature of the saturated sodium carbonate solution was lowered before filtration, washing, and drying to obtain the final mixed precursor. The molar ratio of Na to the metal element in the metal hydroxide was controlled at 1:1. The ratio was determined using ICP detection, with sampling and testing performed after each impregnation and drying, or at intervals. The final mixed precursor was mechanically stirred and heated in a sintering furnace at a rate of 5°C / min to 600°C, held for 3 h, then heated to 850°C and held for 24 h. After natural cooling, the cathode material NaNi was obtained. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 is used in the final product. On average, Ni, Fe, and Mn have the following valence states: Ni is approximately +2, Fe is approximately +3, and Mn is approximately +4. Ni is predominantly +2, Mn exhibits both +3 and +4 valences, and Fe is primarily +3, with a small amount also in +2. Air is introduced throughout the entire heating, holding, and cooling process.

[0039] Example 2

[0040] In this embodiment, the metal hydroxide precursor is Ni. 0.25 Fe 0.4 Mn 0.35Ni(OH)2, Fe(OH)2, Mn(OH)2, in the preparation of the nickel sulfate, ferrous sulfate, manganese sulfate is dissolved in deionized water, the required metal ion solution 2.5 mol / L. NaOH dissolved in deionized water, configured into a basic solution 3.6 mol / L, ammonia 2 mol / L as complexing agent. Metal ion solution, alkaline solution, complexing agent at 40°C temperature, under the protection of inert gas (nitrogen) and stirring conditions into the reaction kettle, coprecipitation to form metal hydroxide, after filtration, washing and drying to obtain metal hydroxide precursor, metal hydroxide particle size D50 is 10 μm, tap density is 1.95 g / cm3. 3 .

[0041] Sodium carbonate is dissolved in 35°C water, preparation of sodium carbonate saturated solution. Metal hydroxide precursor infiltrated dispersion in saturated sodium carbonate solution. Solution temperature is maintained at 35°C, stirring 30 min, while ultrasonic dispersion and multiple vacuum evacuation empty, then filtered to obtain the filter cake; with cold water washing, then drying, to obtain a mixed precursor; repeat the precursor dispersed in saturated sodium carbonate solution, stirring, ultrasonic, vacuum evacuation, filtration, washing, drying, finally, the temperature of the saturated sodium carbonate solution is reduced after filtering, washing, drying, to obtain the final mixed precursor, control the molar ratio of Na element and metal elements in the metal hydroxide is 0.95:1; the final mixed precursor is mechanically stirred, in the sintering furnace 5 ℃ / min to 500 ℃, 5 h, then heated to 950 ℃, 10 h, natural cooling, to obtain the positive electrode material Na 0.95 Ni 0.25 Fe 0.4 Mn 0.35 O2. The whole heating, temperature holding, and cooling process is carried out by air.

[0042] Example 3

[0043] In this embodiment, the metal hydroxide precursor is Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)2, in the preparation of the nickel sulfate, ferrous sulfate, manganese sulfate is dissolved in deionized water, the required metal ion solution 2.5 mol / L. NaOH dissolved in deionized water, configured into a basic solution 3.6 mol / L, ammonia 1 mol / L as complexing agent. Metal ion solution, alkaline solution, complexing agent at 30°C temperature, under the protection of inert gas (nitrogen) and stirring conditions into the reaction kettle, coprecipitation to form metal hydroxide, after filtration, washing and drying to obtain metal hydroxide precursor, metal hydroxide particle size D50 is 10 μm, tap density is 1.95 g / cm3. 3 .

[0044] Sodium carbonate is dissolved in water at 40℃ to prepare a saturated sodium carbonate solution. The metal hydroxide precursor is dispersed in the saturated sodium carbonate solution. The solution is maintained at 40℃, stirred for 30 min, ultrasonically dispersed and repeatedly vacuumed and degassed, then filtered to obtain a filter cake; washed with cold water, then dried to obtain a mixed precursor; the dispersion of the precursor in the saturated sodium carbonate solution is repeated, stirring, ultrasonic dispersion, vacuuming and degassing, filtering, washing, drying, and finally, the saturated sodium carbonate solution is filtered after the temperature is reduced, washed and dried to obtain a final mixed precursor, with the molar ratio of Na element to metal element in the metal hydroxide controlled at 0.95:1; the final mixed precursor is mechanically stirred, heated to 500℃ at a rate of 5℃ / min in a sintering furnace, maintained for 5h, then heated to 900℃ and maintained for 15h, and naturally cooled to obtain a positive electrode material Na 0.95 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2. Air is supplied during the entire heating, temperature maintenance and cooling process.

[0045] Comparative Example 1

[0046] The metal hydroxide precursor used is the same as in Example 1, mixed with ground sodium carbonate, with the molar ratio of Na element to metal element controlled at 1:1, high-speed mixed, heated to 600℃ at a rate of 5℃ / min in a sintering furnace, maintained for 3h, then heated to 850℃ and maintained for 24h, and naturally cooled to obtain a positive electrode material NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2. Air is supplied during the entire heating, temperature maintenance and cooling process.

[0047] Comparative Example 2

[0048] The metal hydroxide precursor used is the same as in Example 2, mixed with ground sodium carbonate, with the molar ratio of Na element to metal element controlled at 0.95:1, high-speed mixed, heated to 500℃ at a rate of 5℃ / min in a sintering furnace, maintained for 5h, then heated to 950℃ and maintained for 10h, and naturally cooled to obtain a positive electrode material Na 0.95 Ni 0.25 Fe 0.4 Mn 0.35 O2. Air is supplied during the entire heating, temperature maintenance and cooling process.

[0049] Comparative Example 3

[0050] The metal hydroxide precursor used in Example 3 was mixed with the milled sodium carbonate to control the molar ratio of Na element to metal element to be 0.95:1, and was mixed with the milled sodium carbonate at high speed, was heated to 500 DEG C at a rate of 5 DEG C / min in a sintering furnace, was kept for 5 h, was then heated to 900 DEG C, was kept for 15 h, was naturally cooled to reduce the temperature, and Na 0.95 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2. Air was passed during the whole heating, keeping warm, and cooling process.

[0051] Detection Example 1

[0052] The products prepared in each example and the comparative example were detected.

[0053] pH detection: 5.0 g of sample was taken, was put into a beaker, 50 ml of deionized water was added, was stirred with a glass rod for 5 min, and was tested for pH with a pH meter.

[0054] Volume detection:

[0055] The positive electrode material: conductive agent: PVDF = 8:1:1 (mass ratio) was made into a positive electrode sheet according to GB / T 37201-2018, lithium metal was used as a negative electrode, a glass fiber separator, an electrolyte, a button cell shell, and the like were used to make a half cell. 0.2C was charged to 4.0V, and then 0.2C was discharged to 2.0V. According to the active material loading of the electrode plate:

[0056] Specific capacity = discharge capacity / active material loading;

[0057] First efficiency = discharge capacity / charge capacity;

[0058] 100 cycle retention rate = 100th cycle capacity / first discharge capacity.

[0059] Table 1

[0060]

[0061] The detection results are shown in Table 1 and Figs. 1-6 , Figs. 1-3 is a charge-discharge curve graph of the example, Figs. 4-6 is a charge-discharge curve graph of the example, under the same raw materials and proportions, the pH value of the positive electrode material obtained in the example is obviously lower than that in the comparative example, indicating that the residual alkali of the material in the example is obviously reduced. In addition, the specific capacity, the first efficiency, and the cycle of the example are generally higher than those of the comparative example, the performance of the positive electrode material obtained in the example is better than that in the comparative example under different conditions, indicating that the method has certain adaptability.

Claims

1. A method for preparing a sodium-ion battery cathode material, characterized in that, The method comprises the following steps: (1) dissolving sodium salt in water to prepare a saturated sodium salt solution; (2) infiltrating and dispersing a metal hydroxide precursor in the saturated sodium salt solution prepared in step (1), collecting the solid substance by filtration, and washing and drying to obtain a mixed precursor; The metal hydroxide precursor is Ni x Fe y Mn (1-x-y) (OH)2, where 0 < x < 1, 0 < y < 1; (3) repeating the treatment of step (2) on the mixed precursor until the molar ratio of Na element to metal element in the final mixed precursor is 0.95-1:1; (4) calcining the final mixed precursor in an oxygen atmosphere to obtain the sodium-ion battery cathode material.

2. The method for preparing the sodium-ion battery cathode material according to claim 1, characterized in that, The sodium salt is at least one of sodium carbonate, sodium acetate, sodium oxalate and sodium stearate.

3. The method for preparing the sodium-ion battery cathode material according to claim 1, characterized in that, The preparation method of the metal hydroxide precursor comprises the following steps: (a) dissolving nickel sulfate, ferrous sulfate and manganese sulfate in deionized water according to the molar ratio of metal ions to prepare a metal ion solution; dissolving NaOH or KOH in deionized water to prepare an alkaline solution; and using ammonia as a complexing agent; (b) mixing the metal ion solution, the alkaline solution and the complexing agent under inert atmosphere protection to co-precipitate, filtering, washing and drying the precipitate to obtain the metal hydroxide precursor.

4. The method for preparing the sodium-ion battery cathode material according to claim 3, characterized in that, The concentration of the metal ion solution is 1.8-2.5 mol / L; the concentration of the alkaline solution is 3.6-4 mol / L; and the concentration of the complexing agent is 1-2 mol / L; and the temperature during the co-precipitation is 30-50℃.

5. The method for preparing the sodium-ion battery cathode material according to claim 1, characterized in that, The temperature of the saturated sodium salt solution is kept at 35-40℃.

6. The method for preparing the sodium-ion battery cathode material according to claim 1, characterized in that, During calcination, the temperature is first kept at 500-600℃ for 3-5 h, and then kept at 850-950℃ for 10-24 h.

7. The method for preparing the sodium-ion battery cathode material according to claim 6, characterized in that, The heating rate during calcination is 5℃ / min.

8. The method for preparing the sodium-ion battery cathode material according to claim 1, characterized in that, The oxygen atmosphere during calcination is air or oxygen.

9. The sodium-ion battery cathode material prepared by the preparation method of any one of claims 1-8.

10. The sodium-ion battery cathode material of claim 9 for use in the preparation of a sodium-ion battery.

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