Carbon-doped sodium iron aluminum titanium sulfate positive electrode material and preparation method therefor

Abstract

A carbon-doped sodium iron aluminum titanium sulfate positive electrode material and a preparation method therefor. The carbon-doped sodium iron aluminum titanium sulfate positive electrode material comprises a carbon material and sodium iron aluminum titanium sulfate modified by the carbon material in situ. The general formula of sodium iron aluminum titanium sulfate is NaxFeyAlzTi1-y-z(SO4)m. Compared with single-ion doping, aluminum-titanium double-ion doping and the in-situ modification with the carbon material can produce a synergistic effect, thereby comprehensively improving the performance of the positive electrode material. Compared with the operations of directly ball milling raw materials and then calcining same, the preparation method, in which spray drying is mainly used for preparing a precursor, achieves more uniform distribution of various elements, is beneficial for obtaining a spherical carbon-doped sodium iron aluminum titanium sulfate positive electrode material, and can further improve the performance of the positive electrode material. The preparation method is simple in terms of technological process and easy to industrialize.

Description

A carbon-doped sodium iron aluminum titanium sulfate cathode material and its preparation method Technical Field

[0001] The present application relates to the technical field of sodium ion batteries, and in particular to a carbon-doped sodium iron aluminum titanium sulfate positive electrode material and a preparation method thereof. Background Art

[0002] Many companies are currently developing sodium-ion batteries, which promise to alleviate the constraints on the energy storage battery industry caused by lithium resource shortages and uneven distribution. As an important supplement to lithium-ion batteries, sodium-ion batteries can also gradually replace lead-acid batteries, which are severely polluting, and possess considerable economic value and strategic significance. The development of the sodium-ion battery industry requires careful consideration of two key issues: whether the technological approach to materials can ultimately achieve large-scale mass production; and whether advanced manufacturing can reduce production costs.

[0003] At present, there are three main routes for the positive electrode materials of sodium ion batteries, namely layered transition metal oxides, Prussian compounds and polyanion compounds. However, the above mainstream positive electrode materials have many technical bottlenecks and large-scale mass production difficulties in industrial applications. For example, layered transition metal oxides such as copper-iron-manganese-based or nickel-iron-manganese-based have problems such as high raw material prices, complex precursor preparation processes, high product sintering temperatures, and strong alkaline wastewater and CO2 gas emissions during the preparation process. The corresponding prepared positive electrode materials have insufficient performance such as low working potential and poor cycle stability, resulting in high production costs and unsatisfactory economic and environmental benefits for this type of positive electrode material, affecting its practical application. The positive electrode materials of the Prussian blue or white system are difficult to control the content of crystalline water in the crystal structure during their preparation process, which seriously affects the crystallinity and electrochemical sodium storage stability of the material. In addition, the high application risk of cyanide greatly increases the difficulty of industrial production of this type of positive electrode material. Compared with the above two types of positive electrode materials, polyanion-type transition metal-based positive electrode materials have a stable crystal structure and three-dimensional sodium ions (Na + ) diffusion channel, showing high sodium storage working voltage and excellent cycle stability, high rate characteristics and low temperature working performance. In particular, sodium iron sulfate-based polyanion positive electrode materials also have the advantages of abundant raw material resources and low cost. They are considered to be the ideal sodium ion battery positive electrode materials in the future and are very cost-effective. Sodium iron sulfate material is a kind of polyanion compound with low raw material price, high product purity, simple production process, easy industrialization, and broad application prospects in the fields of large-scale energy storage and low-speed electric tools. However, pure phase Na x Fe(SO4) y Due to its poor air stability and circulation performance, the material cannot fully meet the requirements for industrial use.

[0004] In summary, it is necessary to develop a carbon-doped sodium iron aluminum titanium sulfate positive electrode material and a preparation method thereof.

[0005] Summary of the Invention

[0006] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0007] In view of the problems existing in the prior art, the present application provides a carbon-doped sodium ferric aluminum titanium sulfate cathode material and a preparation method thereof; the carbon-doped sodium ferric aluminum titanium sulfate cathode material comprises a carbon material and sodium ferric aluminum titanium sulfate in situ modified by the carbon material, and the general formula of the sodium ferric aluminum titanium sulfate is Na x Fe y Al z Ti 1-y-z (SO4) m Compared with single ion doping, the present application can play a synergistic role through dual ion doping of aluminum and titanium and in-situ modification of carbon materials to comprehensively improve the performance of positive electrode materials; the preparation method focuses on using spray drying to prepare the precursor. Compared with directly ball milling the raw materials and then calcining them, the distribution of various elements is more uniform, and it is conducive to obtaining spherical carbon-doped sodium iron aluminum titanium sulfate positive electrode materials, which can further improve the performance of positive electrode materials. The preparation method described in the present application has a simple process flow and is easy to industrialize.

[0008] To achieve this goal, this application adopts the following technical solutions:

[0009] One of the purposes of the present application is to provide a carbon-doped sodium ferric aluminum titanium sulfate positive electrode material, comprising a carbon material and sodium ferric aluminum titanium sulfate in situ modified by the carbon material, wherein the general formula of the sodium ferric aluminum titanium sulfate is Na x Fe y Al z Ti 1-y-z (SO4) m .

[0010] Compared with single ion doping, the carbon-doped sodium ferric sulfate aluminum titanium cathode material described in this application can play a synergistic role through dual ion doping of aluminum and titanium and in-situ modification of carbon materials, comprehensively improving the performance of the cathode material. Aluminum can increase the capacity by promoting the redox reaction of oxygen, titanium can significantly improve the structural stability of the cathode material and thus improve the cycle performance, and carbon can improve the conductivity of the cathode material. The carbon-doped sodium ferric sulfate aluminum titanium cathode material described in this application effectively improves the capacity and cycle performance of the sulfate polyanion sodium cathode material, meeting the use requirements.

[0011] As an optional technical solution of this application, the general formula of the sodium ferric aluminum titanium sulfate is Na x Fe y Al z Ti1-y-z (SO4) m , where 1.5 ≤ x ≤ 1.8, 0.6 < y < 1, 0 < z < 0.4, and x, y, z, and m satisfy charge balance.

[0012] As an optional technical solution of the present application, the mass fraction of the carbon material is 1-5%, such as 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, etc., but not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0013] A second object of the present application is to provide a preparation method for the carbon-doped sodium iron aluminum titanium sulfate positive electrode material described in the first object, and the preparation method includes the following steps:

[0014] (1) Prepare a mixed aqueous solution by mixing sodium sulfate, iron sulfate, aluminum sulfate, titanium oxysulfate and a carbon source;

[0015] (2) Spray-dry the mixed aqueous solution in step (1) to obtain a precursor;

[0016] (3) Calcinate the precursor in step (2) to obtain a carbon-doped sodium iron aluminum titanium sulfate positive electrode material.

[0017] The preparation method of the present application focuses on using spray drying to prepare the precursor. Compared with directly ball-milling the raw materials and then calcining, the distribution of each element is more uniform, and it is beneficial to obtain a spherical carbon-doped sodium iron aluminum titanium sulfate positive electrode material, which can further improve the performance of the positive electrode material. The preparation method of the present application has a simple process flow and is easy to industrialize.

[0018] As an optional technical solution of the present application, step (1) includes: first prepare a mixed aqueous solution of metal ions by mixing sodium sulfate, iron sulfate, aluminum sulfate and titanium oxysulfate, and then add the carbon source and mix evenly to obtain the mixed aqueous solution.

[0019] As an optional technical solution of the present application, the carbon source in step (1) includes any one or a combination of at least two of urea, glucose, sucrose, methanol or ethanol. Typical but non-limiting examples of the combination are: the combination of urea and glucose, the combination of glucose and sucrose, the combination of sucrose and methanol, or the combination of methanol and ethanol, etc.

[0020] In one embodiment, the total metal concentration of the mixed aqueous solution in step (1) is 100-250 g / L, such as 100 g / L, 110 g / L, 130 g / L, 150 g / L, 160 g / L, 180 g / L, 200 g / L, 210 g / L, 230 g / L or 250 g / L, etc., but not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0021] It is worth noting that the total metal concentration of the mixed aqueous solution described in this application refers to the sum of the mass concentrations of all metal elements.

[0022] As an optional technical solution of the present application, the inlet air temperature of the spray drying in step (2) is 250-400°C, for example, 250°C, 260°C, 280°C, 300°C, 310°C, 330°C, 350°C, 360°C, 380°C or 400°C, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0023] In one embodiment, the outlet temperature of the spray drying in step (2) is 80-200°C, for example, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C or 200°C, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0024] In one embodiment, the particle size of the precursor in step (2) is 3-20 μm, for example, 3 μm, 4 μm, 6 μm, 8 μm, 10 μm, 11 μm, 13 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm or 20 μm, etc., but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0025] As an optional technical solution of the present application, the calcination in step (3) is carried out under a nitrogen atmosphere.

[0026] As an optional technical solution of the present application, the calcination temperature in step (3) is 400-500°C, for example, 400°C, 410°C, 430°C, 450°C, 460°C, 480°C or 500°C, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0027] In one embodiment, the calcination time in step (3) is 15-20 hours, for example, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours or 20 hours, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0028] As an optional technical solution of this application, the preparation method comprises the following steps:

[0029] (1) Sodium sulfate, ferric sulfate, aluminum sulfate and titanyl sulfate are first prepared into a mixed aqueous solution of metal ions, and then a carbon source is added and mixed uniformly to obtain a mixed aqueous solution;

[0030] The carbon source includes any one of urea, glucose, sucrose, methanol or ethanol, or a combination of at least two thereof; the total metal concentration of the mixed aqueous solution is 100-250 g / L;

[0031] (2) spray drying the mixed aqueous solution of step (1) to obtain a precursor;

[0032] The inlet air temperature of the spray drying is 250-400°C, and the outlet air temperature is 80-200°C; the particle size of the precursor is 3-20 μm;

[0033] (3) calcining the precursor described in step (2) under a nitrogen atmosphere, controlling the calcination temperature to 400-500° C. and the calcination time to 15-20 h, to obtain a carbon-doped sodium iron aluminum titanium sulfate positive electrode material.

[0034] It is worth noting that the amount of carbon source used in the preparation method described in this application is calculated according to the carbon doping amount. Different types of carbon sources correspond to different amounts of carbon source, and those skilled in the art can determine the amount according to actual conditions.

[0035] Compared with the existing technical solutions, this application has at least the following beneficial effects:

[0036] (1) Compared with single ion doping, the carbon-doped sodium ferric aluminum sulfate titanium cathode material described in the present application can play a synergistic role through dual ion doping of aluminum and titanium and in-situ modification of carbon materials, thereby comprehensively improving the performance of the cathode material. Aluminum can increase the capacity by promoting the redox reaction of oxygen, titanium can significantly improve the structural stability of the cathode material and thus improve the cycle performance, and carbon can improve the conductivity of the cathode material;

[0037] (2) The carbon-doped sodium iron aluminum titanium sulfate cathode material described in this application effectively improves the capacity and cycle performance of the sulfate polyanion sodium cathode material, meeting the use requirements;

[0038] (3) The preparation method described in this application focuses on the use of spray drying to prepare the precursor. Compared with directly ball-milling the raw materials and then calcining them, the distribution of various elements is more uniform, and it is conducive to obtaining spherical carbon-doped sodium iron aluminum titanium sulfate positive electrode materials, which can further improve the performance of the positive electrode materials. The preparation method described in this application has a simple process flow and is easy to industrialize.

[0039] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0040] To facilitate understanding of the present application, the present application lists the following examples. Those skilled in the art should understand that the examples are only provided to help understand the present application and should not be considered as specific limitations of the present application.

[0041] Example 1

[0042] This embodiment provides a carbon-doped sodium ferric aluminum titanium sulfate cathode material and a preparation method thereof. The carbon-doped sodium ferric aluminum titanium sulfate cathode material comprises a carbon material and sodium ferric aluminum titanium sulfate in situ modified by the carbon material. The general formula of the sodium ferric aluminum titanium sulfate is Na 1.5 Fe 0.8 Al 0.1 Ti 0.1 (SO4) 1.9 , the mass fraction of the carbon material is 1%;

[0043] Weigh the raw materials according to the target ratio corresponding to the carbon-doped sodium ferric aluminum sulfate titanium cathode material, and the preparation method comprises the following steps:

[0044] (1) Sodium sulfate, ferric sulfate, aluminum sulfate, and titanyl sulfate are first prepared into a metal ion mixed aqueous solution at a metal molar ratio of 1.5:0.8:0.1:0.1, and then urea is added and mixed uniformly to obtain a mixed aqueous solution; the total metal concentration of the mixed aqueous solution is 200 g / L, and the concentration of urea is 48 g / L;

[0045] (2) spray drying the mixed aqueous solution of step (1) to obtain a precursor;

[0046] The inlet air temperature of the spray drying is 380°C and the outlet air temperature is 180°C; the particle size of the precursor is 5 μm;

[0047] (3) The precursor of step (2) is calcined in a nitrogen atmosphere, the calcination temperature is controlled to be 400° C., and the calcination time is controlled to be 20 h to obtain a carbon-doped sodium iron aluminum titanium sulfate positive electrode material.

[0048] Example 2

[0049] This embodiment provides a carbon-doped sodium ferric aluminum titanium sulfate cathode material and a preparation method thereof. The carbon-doped sodium ferric aluminum titanium sulfate cathode material comprises a carbon material and sodium ferric aluminum titanium sulfate in situ modified by the carbon material. The general formula of the sodium ferric aluminum titanium sulfate is Na 1.5 Fe 0.7 Al 0.2 Ti 0.1 (SO4) 1.95 , the mass fraction of the carbon material is 2%;

[0050] Weigh the raw materials according to the target ratio corresponding to the carbon-doped sodium ferric aluminum sulfate titanium cathode material, and the preparation method comprises the following steps:

[0051] (1) Sodium sulfate, ferric sulfate, aluminum sulfate, and titanyl sulfate are first prepared into a metal ion mixed aqueous solution at a metal molar ratio of 1.5:0.7:0.2:0.1, and then urea is added and mixed uniformly to obtain a mixed aqueous solution; the total metal concentration of the mixed aqueous solution is 100 g / L, and the concentration of urea is 43 g / L;

[0052] (2) spray drying the mixed aqueous solution of step (1) to obtain a precursor;

[0053] The inlet air temperature of the spray drying is 300°C and the outlet air temperature is 100°C; the particle size of the precursor is 10 μm;

[0054] (3) The precursor of step (2) is calcined in a nitrogen atmosphere, and the calcination temperature is controlled to be 450° C. and the calcination time is 18 h to obtain a carbon-doped sodium iron aluminum titanium sulfate positive electrode material.

[0055] Example 3

[0056] This embodiment provides a carbon-doped sodium ferric aluminum titanium sulfate cathode material and a preparation method thereof. The carbon-doped sodium ferric aluminum titanium sulfate cathode material comprises a carbon material and sodium ferric aluminum titanium sulfate in situ modified by the carbon material. The general formula of the sodium ferric aluminum titanium sulfate is Na 1.8 Fe 0.8 Al 0.1 Ti 0.1 (SO4) 2.05 , the mass fraction of the carbon material is 5%;

[0057] Weigh the raw materials according to the target ratio corresponding to the carbon-doped sodium ferric aluminum sulfate titanium cathode material, and the preparation method comprises the following steps:

[0058] (1) Sodium sulfate, ferric sulfate, aluminum sulfate, and titanyl sulfate were first prepared into a metal ion mixed aqueous solution at a metal molar ratio of 1.8:0.8:0.1:0.1, and then urea was added and mixed uniformly to obtain a mixed aqueous solution; the total metal concentration of the mixed aqueous solution was 250 g / L, and the concentration of urea was 255 g / L;

[0059] (2) spray drying the mixed aqueous solution of step (1) to obtain a precursor;

[0060] The inlet air temperature of the spray drying is 260°C and the outlet air temperature is 80°C; the particle size of the precursor is 20 μm;

[0061] (3) The precursor of step (2) is calcined in a nitrogen atmosphere, and the calcination temperature is controlled to be 500° C. and the calcination time is 15 h to obtain a carbon-doped sodium iron aluminum titanium sulfate positive electrode material.

[0062] Comparative Example 1

[0063] This comparative example provides a positive electrode material and a preparation method thereof. Compared with Example 1, the difference is that the aluminum sulfate in the preparation method is completely omitted, but the iron sulfate and titanyl sulfate are increased in equal proportions to ensure that the total metal concentration of the mixed aqueous solution is still 200g / L. The general formula of the prepared positive electrode material is Na 1.5 Fe 0.89 Ti 0.11 (SO4) 1.86 , the mass fraction of the carbon material is 1%.

[0064] Comparative Example 2

[0065] This comparative example provides a positive electrode material and a preparation method thereof. Compared with Example 1, the difference is that titanyl sulfate in the preparation method is completely omitted, but iron sulfate and aluminum sulfate are increased in equal proportions to ensure that the total metal concentration of the mixed aqueous solution is still 200g / L. The general formula of the prepared positive electrode material is Na 1.5 Fe 0.89 Al 0.11 (SO4) 1.81 , the mass fraction of the carbon material is 1%.

[0066] Comparative Example 3

[0067] This comparative example provides a positive electrode material and a preparation method thereof. Compared with Example 1, the difference is that urea in the preparation method is completely omitted, and the general formula of the prepared positive electrode material is Na 1.5 Fe 0.8 Al 0.1 Ti 0.1 (SO4) 1.9 , but does not contain carbon material, that is, no carbon doping.

[0068] Performance characterization:

[0069] The positive electrode materials obtained in the above examples and comparative examples were used as the positive electrode active material. The positive electrode active material was then mixed with acetylene black and polyvinylidene fluoride in a mass ratio of 70:20:10. 1-Methyl-2-pyrrolidone was used as a dispersant. The mixture was mixed evenly to form a slurry, which was then coated on aluminum foil. After vacuum drying at 120°C, the resulting slurry was cut to obtain a 13 mm diameter positive electrode sheet. A sodium metal sheet (16 mm diameter) was used as the negative electrode, a glass fiber membrane (Whatman GF / D) was used as the separator, and 1 M NaClO4 dissolved in EC:PC (1:1 volume ratio) (5 wt.% FEC additive) was used as the electrolyte. A stainless steel shell was used as the outer shell to assemble a CR2025 button cell. The sodium battery assembled in the above process was subjected to charge and discharge tests at room temperature in the potential range of 2.0-4.2 V. The discharge capacity and capacity retention after 1000 cycles are shown in Table 1.

[0070] Table 1

[0071] In summary, the present application provides a carbon-doped sodium ferric aluminum titanium sulfate cathode material and a preparation method thereof; the carbon-doped sodium ferric aluminum titanium sulfate cathode material comprises a carbon material and sodium ferric aluminum titanium sulfate in situ modified by the carbon material, and the general formula of the sodium ferric aluminum titanium sulfate is Na x Fe y Al z Ti 1-y-z (SO4) m Compared with single ion doping, the present application can play a synergistic role through dual ion doping of aluminum and titanium and in-situ modification of carbon materials to comprehensively improve the performance of positive electrode materials; the preparation method focuses on using spray drying to prepare the precursor. Compared with directly ball milling the raw materials and then calcining them, the distribution of various elements is more uniform, and it is conducive to obtaining spherical carbon-doped sodium iron aluminum titanium sulfate positive electrode materials, which can further improve the performance of positive electrode materials. The preparation method described in the present application has a simple process flow and is easy to industrialize.

[0072] This application uses the above-mentioned embodiments to illustrate the detailed process equipment and process flow of this application. However, this application is not limited to the above-mentioned detailed process equipment and process flow, that is, it does not mean that this application must rely on the above-mentioned detailed process equipment and process flow to be implemented. Those skilled in the art should understand that any improvements to this application, equivalent replacement of various raw materials of the product of this application, addition of auxiliary ingredients, selection of specific methods, etc., all fall within the scope of protection and disclosure of this application.

Claims

1. A carbon-doped sodium ferric aluminum titanium sulfate positive electrode material, comprising a carbon material and sodium ferric aluminum titanium sulfate in situ modified by the carbon material, wherein the general formula of the sodium ferric aluminum titanium sulfate is Na x Fe y Al z Ti 1-y-z (SO4) m .

2. The carbon-doped sodium iron aluminum titanium sulfate positive electrode material according to claim 1, wherein: The general formula of the sodium aluminum iron titanium sulfate is Na x Fe y Al z Ti 1-y-z (SO4) m , where 1.5 ≤ x ≤ 1.8, 0.6 < y < 1, 0 < z < 0.4, and x, y, z, and m satisfy charge balance.

3. The carbon-doped sodium iron aluminum titanium sulfate positive electrode material according to claim 1 or 2, wherein: The mass fraction of the carbon material is 1-5%.

4. A method for preparing the carbon-doped sodium iron aluminum titanium sulfate positive electrode material according to any one of claims 1 to 3, comprising the following steps: (1) preparing a mixed aqueous solution of sodium sulfate, ferric sulfate, aluminum sulfate, titanyl sulfate and a carbon source; (2) spray drying the mixed aqueous solution of step (1) to obtain a precursor; (3) calcining the precursor described in step (2) to obtain a carbon-doped sodium iron aluminum titanium sulfate positive electrode material.

5. The preparation method according to claim 4, wherein Step (1) comprises: firstly preparing sodium sulfate, ferric sulfate, aluminum sulfate and titanyl sulfate into a metal ion mixed aqueous solution, then adding the carbon source and mixing evenly to obtain the mixed aqueous solution.

6. The preparation method according to claim 4 or 5, wherein: The carbon source in step (1) includes any one of urea, glucose, sucrose, methanol or ethanol, or a combination of at least two thereof; Optionally, the total metal concentration of the mixed aqueous solution in step (1) is 100-250 g / L; 7. The preparation method according to any one of claims 4 to 6, wherein: The inlet air temperature of the spray drying in step (2) is 250-400°C; Optionally, the outlet air temperature of the spray drying in step (2) is 80-200°C; Optionally, the particle size of the precursor in step (2) is 3-20 μm.

8. The preparation method according to any one of claims 4 to 7, wherein: The calcination in step (3) is carried out under a nitrogen atmosphere.

9. The preparation method according to any one of claims 4 to 8, wherein: The calcination temperature in step (3) is 400-500°C; Optionally, the calcination time in step (3) is 15-20 hours.

10. The preparation method according to any one of claims 4 to 9, wherein: The preparation method comprises the following steps: (1) firstly prepare sodium sulfate, iron sulfate, aluminum sulfate and titanyl sulfate into a metal ion mixed aqueous solution, then add a carbon source and mix evenly to obtain a mixed aqueous solution; The carbon source includes any one of urea, glucose, sucrose, methanol or ethanol or a combination of at least two thereof; the total metal concentration of the mixed aqueous solution is 100-250 g / L; (2) spray drying the mixed aqueous solution of step (1) to obtain a precursor; The inlet air temperature of the spray drying is 250-400°C, and the outlet air temperature is 80-200°C; the particle size of the precursor is 3-20 μm; (3) calcining the precursor described in step (2) under a nitrogen atmosphere, controlling the calcination temperature to 400-500° C. and the calcination time to 15-20 h, to obtain a carbon-doped sodium iron aluminum titanium sulfate positive electrode material.

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