A method for preparing a multi-element uniformly doped sodium ferric sulfate porous sodium electric positive electrode material by a mixed alcohol precipitation method

Abstract

The application relates to the technical field of batteries, in particular to a method for preparing a multi-element uniformly doped sodium ferric sulfate porous sodium electric positive electrode material by a mixed alcohol precipitation method, characterized in that: a to-be-doped element sulfate and ferrous sulfate heptahydrate are weighed according to a molar ratio of (0.1% to 15%):1, and anhydrous sodium sulfate corresponding to a molar amount is dissolved in deionized water to form a uniform mixed solution; the mixed solution is added to a mixed alcohol solution containing a carbon source; stirring is carried out at room temperature for a certain time (1 min to 4 h); slurry is separated to obtain a powder; filtrate is collected and stored for subsequent recycling; and the powder is sintered to prepare a multi-element uniformly doped sodium ferric sulfate material. The method disclosed by the application can effectively solve the problems of difficult mixing of raw materials, impure products, many defects, uneven distribution of doped elements, and difficult regulation of secondary particle and pore distribution in the traditional synthesis and modification process, and finally improves the electrochemical performance of the doped sodium ferric sulfate positive electrode material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a method for preparing a multi-element uniformly doped sodium ferric sulfate porous sodium battery positive electrode material by a mixed alcohol precipitation method, a doped sodium ferric sulfate material prepared by the method and a battery comprising the doped sodium ferric sulfate material. BACKGROUND

[0002] In recent years, with the rapid development of the new energy industry, due to uneven distribution of lithium ore and difficulty in mining, lithium-ion batteries are facing the problem of rising costs year by year, and it is urgent to find suitable substitutes. Sodium is attracting much attention due to its similar physical and chemical properties to lithium, abundant raw materials, wide sources, and low raw material costs. Sodium-ion battery positive electrode materials can be divided into three categories: layered oxides, polyanion-type compounds, and Prussian blue analogues. Polyanion-type materials have stable crystal structures and three-dimensional sodium ion (Na + ) diffusion channels, and exhibit high voltage, high rate, and low-temperature working performance and excellent cycle performance. In particular, sodium ferric sulfate-based polyanion positive electrode materials have lower raw material costs, lower synthesis temperatures, and lower energy consumption than other polyanion materials.

[0003] Investigation shows that the common synthesis and modification method for sodium ferric sulfate materials is to mix iron source, sodium source, sulfur source, and carbon source by solid-phase ball milling (CN118676332A, CN118676332A, CN116692950A) or sand milling (CN118479548A). This method effectively reduces the preparation cost of sodium ferric sulfate materials in actual production, but cannot avoid the problems of uneven mixing of raw materials, low product purity, many defects, and uncontrollable secondary particle and pore distribution in the solid-phase mixing process. In recent years, some reports have also prepared sodium ferric sulfate materials by spray drying (CN118117067A), sol-gel method (CN118164458A), and microwave solvent thermal method (CN116553621B). The essence of the spray drying method is heating and dehydration, and the solubility of different sulfates varies greatly with temperature. The obtained solid is not a homogeneous mixture of sulfates, and the acidic solution has high corrosion on the spray inlet and outlet pipelines. The sol-gel method and the microwave solvent thermal method have high energy consumption. In summary, there is no patent or literature report on the preparation of multi-element doped sodium ferric sulfate materials with few defects, high purity, and controllable secondary particle and pore distribution by simple, low-energy room-temperature solid-liquid separation. In view of the deficiencies of the prior art, the present application first reports a simple and efficient method for preparing a multi-element uniformly doped sodium ferric sulfate material porous sodium battery positive electrode material by mixing sodium source, iron source, sulfur source, carbon source, and various doped elements sulfates at room temperature. SUMMARY

[0004] The present application aims to overcome the above-mentioned problems existing in the prior art, and provide a method for simply and efficiently preparing a multi-element uniformly doped sodium ferric sulfate porous sodium electric positive electrode material, a doped sodium ferric sulfate material prepared by the method, and a battery comprising the doped sodium ferric sulfate material. The present application has the advantages of uniform mixing, few defects, high product purity, controllable secondary particle and pore distribution, and significantly improved electrochemical activity and rate performance.

[0005] The method for preparing a multi-element uniformly doped sodium ferric sulfate porous sodium electric positive electrode material by a mixed alcohol precipitation method has the following steps:

[0006] ① Under room temperature conditions, mix and stir the ferrous sulfate heptahydrate, anhydrous sodium sulfate, and the doped element sulfate in deionized water in a certain proportion to form a mixed solution A;

[0007] ② Dissolve a certain amount of carbon source in mixed alcohol to form solution B, and mix solution B with mixed solution A in a certain volume ratio;

[0008] ③ Add mixed solution A to mixed solution B, and stir at room temperature for a period of time to obtain a slurry;

[0009] ④ Separate the slurry obtained in step ③ to obtain filtrate (supernatant) and powder, and perform subsequent operations on the powder, and collect and store the filtrate for subsequent recycling;

[0010] ⑤ Sinter the powder in step ④ in an inert atmosphere for a period of time to obtain a multi-element uniformly doped sodium ferric sulfate material.

[0011] Further, the room temperature range in step ① is 20-30℃, and the molar ratio of anhydrous sodium sulfate to ferrous sulfate heptahydrate is (1:1, 2.4:1.8, 2.5:1.75, 2.6:1.7);

[0012] Further, the molar ratio of the total of the plurality of doped element sulfates to ferrous sulfate heptahydrate in step ① is (0.1%-15%:1), and the doped element sulfates include several of nickel sulfate hexahydrate, magnesium sulfate, manganese sulfate monohydrate, copper sulfate, vanadium oxide sulfate hydrate, cobalt ammonium sulfate hexahydrate, zinc sulfate heptahydrate, lithium sulfate monohydrate, potassium sulfate, and calcium sulfate dihydrate;

[0013] Further, the mixed alcohol in step ② includes several of anhydrous ethanol, methanol, ethylene glycol, glycerol, and n-butanol, and the carbon source includes one or several of glucose, citric acid monohydrate, ascorbic acid, Super P, graphene, carbon nanotubes, PVP, and sucrose, and the volume ratio of mixed solution A to solution B is (1:1-10);

[0014] Further, the stirring time in the step ③ is 1 min-4 h;

[0015] Further, the inert atmosphere in the step ⑤ is argon-hydrogen mixed gas (hydrogen accounts for 1%-5% of the volume) and high-purity nitrogen, the sintering temperature is 300-400℃, and the sintering time is 2 h-12 h;

[0016] Compared with the prior art, the application has at least the following advantages:

[0017] (1) The method for preparing the multi-element uniformly doped sodium ferric sulfate porous sodium battery positive electrode material provided by the application does not need to be mixed for a long time, shortens the production cycle, and reduces the production cost;

[0018] (2) The method for preparing the multi-element uniformly doped sodium ferric sulfate porous sodium battery positive electrode material can realize the uniform doping of multiple doping elements, so that the electrochemical performance of the prepared sodium ferric sulfate material is obviously improved;

[0019] (3) The method for preparing the multi-element uniformly doped sodium ferric sulfate porous sodium battery positive electrode material effectively solves the problems of difficult mixing of raw materials, impurity, many defects, uneven distribution of doping elements, long preparation period, and difficult regulation of secondary particles and pore distribution in the traditional solid-phase mixing process;

[0020] (4) The method for preparing the multi-element uniformly doped sodium ferric sulfate porous sodium battery positive electrode material avoids the raw material loss in the traditional production process, and effectively improves the product yield. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 Fig. 2 shows the XRD diffraction pattern of the multi-element uniformly doped sodium ferric sulfate material prepared by an embodiment of the application.

[0022] Figure 2 Fig. 3 shows the SEM graph of the multi-element uniformly doped sodium ferric sulfate material prepared by an embodiment of the application.

[0023] Figure 3 Fig. 4 shows the SEM-EDX graph of the multi-element uniformly doped sodium ferric sulfate material prepared by an embodiment of the application.

[0024] Figure 4 Fig. 5 shows the Raman curve graph including the multi-element uniformly doped sodium ferric sulfate material prepared by an embodiment of the application.

[0025] Figure 5XPS figure of the prepared multi-element uniformly doped sodium ferric sulfate material provided by an embodiment of the present application

[0026] Figure 6 The figure shows the room temperature and-50℃ low temperature first circle charge-discharge curve figure of the prepared multi-element uniformly doped sodium ferric sulfate material provided by an embodiment of the present application.

[0027] Figure 7 The figure shows the CV curve figure of the prepared multi-element uniformly doped sodium ferric sulfate material provided by an embodiment of the present application.

[0028] Figure 8 The figure shows the capacity retention figure of the prepared multi-element uniformly doped sodium ferric sulfate material provided by an embodiment of the present application.

[0029] Figure 9 The figure shows the rate performance figure of the prepared multi-element uniformly doped sodium ferric sulfate material provided by an embodiment of the present application.

[0030] Figure 10 The figure shows the nitrogen adsorption-desorption curve figure of the prepared multi-element uniformly doped sodium ferric sulfate material provided by an embodiment of the present application, and the inset figure is the pore size distribution figure. Specific implementation method

[0031] The specific implementation of the present application is described in detail below. It should be understood that the specific implementation described herein is only used to illustrate and explain the present application, and is not used to limit the present application.

[0032] The first aspect of the present application provides a method for preparing a multi-element uniformly doped sodium ferric sulfate porous sodium electric positive electrode material, which specifically relates to a mixed alcohol precipitation method, comprising the following steps:

[0033] Example one

[0034] The application discloses a method for preparing a multi-element uniformly doped sodium ferrite sulfate porous sodium battery positive electrode material by a mixed alcohol precipitation method. 2 ·g -1 , the pore size is 28.8041nm, the 0.1C discharge specific capacity is 107.34mAh·g -1 , the 1C capacity is 105.53mAh·g -1 , the 50-cycle cycle retention rate is 89.02%, and the 1C discharge specific capacity under the condition of-50 DEG C is 74.83mAh·g -1 .

[0035] Example two

[0036] The application discloses a method for preparing a multi-element uniformly doped sodium ferrite sulfate porous sodium battery positive electrode material by a mixed alcohol precipitation method. The specific operation scheme is as follows: 48.652g of ferrous sulfate heptahydrate, 17.7553g of sodium sulfate, 0.429g of nickel sulfate hexahydrate and 0.197g of magnesium sulfate are dispersed in 300mL of deionized water to form solution A; 4.865g of citric acid monohydrate, 0.487g of glucose and 2.019g of carbon nanotubes are dispersed in 600mL of anhydrous ethanol / glycerol mixed alcohol (glycerol accounts for 20% by volume) to form solution B; solution A is slowly added to solution B under the condition of 25 DEG C and high-speed stirring, and after mixing for 5min, slurry is obtained; the slurry is extracted and filtered to obtain filtrate and powder, the filtrate is collected and stored for subsequent recycling; and the powder is sintered under the atmosphere of high-purity nitrogen at 350 DEG C for 4h to obtain a nickel and magnesium double-element co-doped sodium ferrite sulfate material. The specific surface area of the material is 11.9828m 2 ·g -1 , the pore size is 28.8371nm, the 0.1C discharge specific capacity is 109.66mAh·g -1 , the 1C capacity is 106.76mAh·g -1, the 50 cycle retention rate is 86.64%, and the 1C discharge specific capacity at-50 DEG C is 75.10 mAh.g -1 .

[0037] Example Three

[0038] The application discloses a method for preparing a multi-element uniformly doped sodium ferric sulfate porous sodium battery positive electrode material by a mixed alcohol precipitation method. 2 ·g -1 , the pore size is 28.8441 nm, the 0.1C discharge specific capacity is 102.37 mAh.g -1 , the 1C capacity is 100.66 mAh.g -1 , the 50 cycle retention rate is 85.44%, and the 1C discharge specific capacity at-50 DEG C is 74.19 mAh.g -1 .

[0039] Example Four

[0040] The application discloses a method for preparing a multi-element uniformly doped sodium ferric sulfate porous sodium battery positive electrode material by a mixed alcohol precipitation method. 2 ·g -1, the pore size is 28.8393 nm, the 0.1C discharge specific capacity is 101.17 mAh·g -1 , the 1C capacity is 99.62 mAh·g -1 , the 50-cycle retention rate is 88.63%, and the 1C discharge specific capacity under the condition of -50 DEG C is 73.87 mAh·g -1 .

[0041] Example Five

[0042] A method for preparing a multi-element uniformly doped sodium ferrite porous sodium electric positive electrode material by a mixed alcohol extraction method is disclosed. The specific operation scheme is as follows: 52.1269 g of ferrous sulfate heptahydrate, 17.755 g of sodium sulfate, 0.4682 g of copper sulfate pentahydrate, and 0.2193 g of vanadium sulfate hydrate are dispersed in 200 mL of deionized water to form solution A; 5.2127 g of citric acid monohydrate, 0.5212 g of ascorbic acid, 3.6 g of PVP, and 2.019 g of carbon nanotubes are dispersed in 720 mL of anhydrous ethanol / n-butanol mixed alcohol (the volume ratio of n-butanol is 10%) to form solution B; solution A is slowly added to solution B under high-speed stirring at 25 DEG C, and mixed for 5 min to obtain a slurry; the slurry is extracted to obtain a filtrate and a powder, and the filtrate is collected and stored for subsequent recycling; the powder is sintered at 350 DEG C for 6 h under a high-purity nitrogen atmosphere to obtain a copper and vanadium co-doped sodium ferrite material. The specific surface area of the material is 12.0145 m 2 ·g -1 , the pore size is 28.8478 nm, the 0.1C discharge specific capacity is 104.62 mAh·g -1 , the 1C capacity is 102.21 mAh·g -1 , the 50-cycle retention rate is 89.73%, and the 1C discharge specific capacity under the condition of -50 DEG C is 74.77 mAh·g -1 .

Claims

1. A method for preparing a multi-element homogeneously doped sodium ferrite porous sodium electric positive electrode material by mixed alcohol precipitation, characterized in that, The method comprises the following steps: ① mixing ferrous sulfate heptahydrate, anhydrous sodium sulfate, and a dopant element sulfate in deionized water in a certain proportion, stirring uniformly to form a mixed solution A at room temperature; ② dissolving a certain amount of carbon source in mixed alcohol to form solution B, and mixing solution B with mixed solution A in a certain volume ratio; ③ adding mixed solution A to mixed solution B, stirring at room temperature for a period of time to obtain a slurry; ④ separating the slurry obtained in step ③ to obtain a filtrate and a powder, and the powder is subjected to subsequent operation, and the filtrate is collected and stored for subsequent recycling; ⑤ sintering the powder in step ④ in an inert atmosphere for a period of time to obtain a multi-element doped sodium ferric sulfate material; The total molar ratio of the dopant element sulfate to ferrous sulfate heptahydrate is 0.1% to 15%:1, and the multi-element dopant element sulfate includes several of nickel sulfate hexahydrate, magnesium sulfate, manganese sulfate monohydrate, copper sulfate, vanadium sulfate hydrate, cobalt sulfate ammonium hexahydrate, zinc sulfate heptahydrate, lithium sulfate monohydrate, potassium sulfate, and calcium sulfate dihydrate. The mixed alcohol includes several of anhydrous ethanol, methanol, ethylene glycol, glycerol, and n-butanol, and the carbon source includes one or several of glucose, citric acid monohydrate, ascorbic acid, Super P, graphene, carbon nanotubes, and PVP. The volume ratio of mixed solution A to solution B is 1:1 to 10.

2. The method of claim 1, wherein, The room temperature in step ① is 20 to 30 °C, and the molar ratio of anhydrous sodium sulfate to ferrous sulfate heptahydrate is one of 1:1, 2.4:1.8, 2.5:1.75, and 2.6:1.

7.

3. The method of claim 1, wherein, The stirring time in step ③ is 1 minute to 4 hours.

4. The method of claim 1, wherein, The inert atmosphere in step ⑤ is argon-hydrogen mixed gas or high-purity nitrogen, the sintering temperature is 300 to 400 °C, and the sintering time is 2 to 12 hours.

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