A method for preparing a potassium-ion battery anode composite material and the resulting material

Abstract

This invention discloses a method for preparing a potassium-ion battery anode composite material, comprising the following steps: dissolving indium nitrate hydrate and terephthalic acid in an N,N-dimethylformamide solution, then adding sodium acetate solution, heating and reacting, collecting the mixture, centrifuging and washing, and drying the washed precipitate to obtain In-MOF; sulfiding In-MOF into In2S3 / C material with thioacetamide at 400-450℃ under an argon atmosphere, wherein the mass ratio of thioacetamide to In-MOF is 4-5:1; and nitrogen doping of the In2S3 / C material with urea under an argon atmosphere at 300-600℃. The N-In2S3 / C potassium-ion battery anode composite material of this invention, with N replacing S doping on In2S3, increases defects and active sites, enhances chemical bond polarity and conductivity, lowers the diffusion barrier, which is beneficial for potassium ion storage, diffusion, and transport, thus enhancing electrochemical performance.

Description

Technical Field

[0001] This invention relates to the field of battery anode materials, specifically to a method for preparing a potassium-ion battery anode composite material and the resulting material. Background Technology

[0002] Potassium-ion batteries, as a choice for large-scale energy storage devices, have unique advantages. First, potassium is the seventh most abundant element in the Earth's crust, and compared to lithium, it is cheaper and more abundant, making it more suitable for large-scale electrochemical energy storage systems. Second, potassium-ion batteries have a rocking-chair working principle similar to lithium-ion batteries, providing a good foundation for potassium-ion battery research. Third, K... + The standard redox potential of / K (-2.93V vs. SHE) can not only be compared with Li + The redox potential of Li is comparable to that of SHE (-3.04V vs. SHE), and also surpasses that of Na. + The standard redox potential of sodium (-2.71V vs. SHE) is lower, allowing potassium-ion batteries to generate higher operating voltages. Finally, since aluminum and potassium do not form an Al-K alloy, aluminum foil can be used instead of more expensive copper foil as the current collector for the negative electrode of potassium-ion batteries, further reducing the overall production cost.

[0003] Despite the aforementioned advantages, potassium-ion batteries still face several unresolved issues. These include the large radius of potassium ions leading to severe volume expansion of the negative electrode during cycling; poor ion diffusion, which significantly limits reaction kinetics; and insufficient actual specific capacity and energy density. These problems hinder the large-scale commercial production of potassium-ion batteries. Therefore, selecting suitable negative electrode materials for potassium-ion batteries will have a significant impact on their practical applications.

[0004] In2S3 / C composite materials possess a large number of incompletely coordinated sulfur atoms, allowing them to accommodate more potassium ions and enhance electrochemical activity. The carbon coating provides higher conductivity while effectively mitigating the negative electrode volume expansion problem during the reaction process, stabilizing battery performance. Furthermore, its low cost and lack of environmental impact make it a highly promising anode material for potassium-ion batteries. However, the actual specific capacity of In2S3 / C composite materials remains relatively low. For example, Chinese Patent Publication No. CN115074570A discloses an indium-carbon composite material, but its specifications are not shown in the attached figures. Figure 4 and Figure 5 The demonstrated battery specific capacity is not ideal. Therefore, modifying the In2S3 / C composite material to develop electrode materials with higher actual specific capacity is key to advancing its practical application. Summary of the Invention

[0005] Purpose of the invention: In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing a potassium-ion battery anode composite material that improves potassium-ion storage efficiency. Another purpose of this invention is to provide a potassium-ion battery anode composite material that enhances conductivity and improves the actual specific capacity of the battery.

[0006] Technical solution: The present invention provides a method for preparing a potassium-ion battery anode composite material, comprising the following steps:

[0007] (1) Dissolve indium nitrate hydrate and terephthalic acid in N,N-dimethylformamide solution, then add sodium acetate solution, heat to react, collect the mixture, centrifuge and wash, take the washed precipitate and dry to obtain the precursor In-MOF;

[0008] (2) In-MOF is vulcanized into In2S3 / C material by thioacetamide (C2H5NS) in an argon atmosphere at 400-450℃, with the mass ratio of thioacetamide to In-MOF being 4-5:1.

[0009] (3) Nitrogen doping of In2S3 / C material was carried out in the furnace tube of a micro-tube furnace with urea and the reaction was carried out in an argon atmosphere at 300-600℃ to obtain N-In2S3 / C composite material.

[0010] Further, in step (1), the heating temperature is 115–125°C, and the reaction time is 2–3 hours. The centrifugation speed is 7500–8500 rpm, which is beneficial for better separation of the solid and liquid phases. If the speed is lower than 7500 rpm, a large amount of product will be dispersed in the washing liquid, resulting in a decrease in yield. The washing time is 3–5 minutes, and the number of washings is 6–8 times, using deionized water. The drying is vacuum drying, with a drying temperature of 70–80°C and a drying time of 10–12 hours.

[0011] Further, in step (2), the temperature is increased from room temperature to 400-450°C at a rate of 1-2°C / min, and the reaction is kept at a constant temperature for 5-6 hours, followed by natural cooling to room temperature. If the reaction temperature is below 400°C, In-MOF cannot be completely sulfided into In2S3 / C; if the reaction temperature is above 450°C, over-reaction will occur, generating other indium-based sulfides, resulting in an impure product.

[0012] Further, in step (3), the mass ratio of urea to In2S3 / C material is 5–15:1. The temperature is increased from room temperature to 300–600°C at a rate of 5–6°C / min, and the reaction is maintained at this temperature for 5–7 hours, followed by natural cooling to room temperature. If the reaction temperature is below 300°C, N ions cannot be effectively incorporated into In2S3; if the reaction temperature is above 600°C, over-reaction will occur, generating impurities. Urea (CH4N2O) is located at the upper air vent, and In2S3 / C material is located at the lower air vent. A vacuum is then evacuated from the furnace tube to remove air, and finally, argon gas is introduced into the tube.

[0013] The potassium-ion battery anode composite material obtained by the above preparation method has N-In₂S₃ uniformly coated with a C matrix. The mass percentage of N-In₂S₃ is 96.7%, and the mass percentage of C is 3.3%, with an overall specific surface area of ​​65.75 m². 2 / g.

[0014] Preparation Principle: The actual specific capacity of In2S3 / C composite materials is not high, which is insufficient for the application of potassium-ion batteries in large-scale energy storage systems. This invention involves nitrogen doping of the In2S3 / C composite material, introducing N atoms to replace some S atoms to obtain more defects and active sites, thereby improving potassium-ion storage efficiency. Simultaneously, nitrogen doping disrupts the original In2S3 bonds, enhances chemical bond polarity, lowers the diffusion barrier, and facilitates the diffusion and transport of potassium ions and electrons, thus improving the battery's actual specific capacity and overall electrochemical performance.

[0015] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0016] 1. For the first time, N-In2S3 / C composite material was applied to the negative electrode of potassium-ion battery. The doping of N atoms increased the defects and active sites of the material, while breaking the original bonds, enhancing the chemical bond polarity, and reducing the diffusion energy barrier, which is beneficial to the storage, diffusion and transport of potassium ions and enhances the conductivity of the material.

[0017] 2. The N-In2S3 / C composite material significantly improved the actual specific capacity of the battery, exhibiting excellent electrochemical performance, from 0.1Ag -1 up to 3Ag -1 At current densities, its rate performance is far superior to that of undoped In2S3 / C composite material;

[0018] 3. The preparation process is relatively stable, simple and convenient, highly reproducible, and suitable for large-scale production applications. Attached Figure Description

[0019] Figure 1 This is the X-ray diffraction pattern of the present invention;

[0020] Figure 2 These are transmission electron microscope images of Embodiment 3 of the present invention;

[0021] Figure 3 These are scanning electron microscope images of Embodiment 3 of the present invention;

[0022] Figure 4 This is a comparison chart of the rate performance of potassium-ion button cells assembled in Embodiment 3 and Comparative Example 1 of the present invention;

[0023] Figure 5 The potassium-ion coin cell assembled in Embodiment 3 and Comparative Example 1 of this invention is at 0.5Ag -1 The following is a comparison chart of the cycle performance. Detailed Implementation

[0024] Example 1

[0025] A method for preparing a potassium-ion battery anode composite material includes the following steps:

[0026] (1) Indium nitrate hydrate and terephthalic acid were dissolved in N,N-dimethylformamide solution, followed by sodium acetate solution. The mixture was heated at 120°C for 2 hours. The mixture was collected and washed with deionized water by centrifugation at 8000 rpm for 3 minutes and 6 times. The washed precipitate was then vacuum dried at 70°C for 12 hours to obtain the precursor In-MOF.

[0027] (2) Under an argon atmosphere, the temperature was increased from room temperature to 400°C at a heating rate of 2°C / min, and the reaction was kept at a constant temperature for 6 hours. The temperature was then naturally cooled to room temperature. The In-MOF was sulfided into In2S3 / C material using thioacetamide (C2H5NS). The mass ratio of thioacetamide to In-MOF was 4:1.

[0028] (3) Weigh urea and In2S3 / C material in a mass ratio of 5:1, place them in their respective crucibles and put them in the furnace tube of a micro-tube furnace, with the urea at the upper air inlet and the In2S3 / C material at the lower air inlet. Then, evacuate the furnace tube to remove the air inside, and finally introduce argon gas into the tube. Set the working procedure: heat from room temperature to 300℃ at a heating rate of 5℃ / min, and react at a constant temperature for 6 hours. Then, cool naturally to room temperature to obtain N-In2S3 / C composite material.

[0029] Example 2

[0030] (1) Indium nitrate hydrate and terephthalic acid were dissolved in N,N-dimethylformamide solution, followed by sodium acetate solution. The mixture was heated at 120°C for 2 hours. The mixture was collected and washed with deionized water by centrifugation at 8000 rpm for 3 minutes and 6 times. The washed precipitate was then vacuum dried at 70°C for 12 hours to obtain the precursor In-MOF.

[0031] (2) Under an argon atmosphere, the temperature was increased from room temperature to 400°C at a heating rate of 2°C / min, and the reaction was kept at a constant temperature for 6 hours. The temperature was then naturally cooled to room temperature. The In-MOF was sulfided into In2S3 / C material using thioacetamide (C2H5NS). The mass ratio of thioacetamide to In-MOF was 4:1.

[0032] (3) Weigh urea and In2S3 / C material in a mass ratio of 10:1, place them in their respective crucibles and put them in the furnace tube of a micro-tube furnace, with the urea at the upper air inlet and the In2S3 / C material at the lower air inlet. Then, evacuate the furnace tube to remove the air inside, and finally introduce argon gas into the tube. Set the working procedure: heat from room temperature to 500℃ at a heating rate of 5℃ / min, and react at a constant temperature for 6 hours. Then, cool naturally to room temperature to obtain N-In2S3 / C composite material.

[0033] Example 3

[0034] (1) Indium nitrate hydrate and terephthalic acid were dissolved in N,N-dimethylformamide solution, followed by sodium acetate solution. The mixture was heated at 120°C for 2 hours. The mixture was collected and washed with deionized water by centrifugation at 8000 rpm for 3 minutes and 6 times. The washed precipitate was then vacuum dried at 70°C for 12 hours to obtain the precursor In-MOF.

[0035] (2) Under an argon atmosphere, the temperature was increased from room temperature to 400°C at a heating rate of 2°C / min, and the reaction was kept at a constant temperature for 6 hours. The temperature was then naturally cooled to room temperature. The In-MOF was sulfided into In2S3 / C material using thioacetamide (C2H5NS). The mass ratio of thioacetamide to In-MOF was 4:1.

[0036] (3) Weigh urea and In2S3 / C material in a mass ratio of 15:1, place them in their respective crucibles and put them in the furnace tube of a micro-tube furnace, with the urea at the upper air inlet and the In2S3 / C material at the lower air inlet. Then, evacuate the furnace tube to remove air, and finally introduce argon gas into the tube. Set the working procedure: heat from room temperature to 600℃ at a heating rate of 5℃ / min, and maintain the temperature for 6 hours. Then, cool naturally to room temperature to obtain the N-In2S3 / C composite material. The mass percentage of N-In2S3 is 96.7wt%, the mass percentage of C is 3.3wt%, and the specific surface area of ​​the overall material is 65.75m². 2 / g.

[0037] like Figure 1 As can be seen from the XRD patterns of the N-In2S3 / C composite materials obtained in Examples 1 to 3, the final nitrogen-doped In2S3 / C composite materials were successfully prepared under all three different conditions, indicating the stability of the preparation process.

[0038] Depend on Figures 2-3 It can be seen that N-In2S3 is coated by the carbon matrix and is distributed relatively evenly. This morphology can effectively alleviate the volume expansion of In2S3 during battery cycling.

[0039] Comparative Example 1

[0040] This comparative example is an In2S3 / C composite material without any doping treatment, with the same morphology as in Example 3. The mass percentage of In2S3 is 94.7 wt%, the mass percentage of C is 5.3 wt%, and the specific surface area of ​​the overall material is 80.75 m². 2 / g.

[0041] Potassium-ion battery anodes were fabricated using the materials obtained in Example 3 and Comparative Example 1, and coin cells were assembled for relevant electrochemical performance tests. Figure 4 As shown, the nitrogen-doped N-In2S3 / C composite material at 0.1 Ag... -1 up to 3Ag -1 At seven different current densities within the range, the rate performance was significantly higher than that of the undoped In2S3 / C composite material, while the rate performance remained superior even at a current density of 0.1 Ag. -1 At this time, the N-In2S3 / C electrode exhibited good specific capacity recovery capability. These results indicate that nitrogen doping treatment not only significantly improves the electrochemical performance of the battery but also enhances its cycle stability.

[0042] Figure 5 For materials before and after nitrogen doping at 0.5Ag -1The comparison of cycle performance clearly shows that during 100 charge-discharge cycles, the specific capacity of the nitrogen-doped N-In2S3 / C electrode is consistently higher than that of the undoped In2S3 / C electrode. Furthermore, the specific capacity of the N-In2S3 / C electrode after 100 cycles is 292.64 mAh g⁻¹. -1 It still maintains a higher specific capacity than the In2S3 / C electrode during the second cycle (290.18 mAh g). -1 These results further demonstrate the comprehensive improvement of the electrochemical performance of In2S3 / C composites by nitrogen doping, which plays an important role in promoting the practical application of this material.

[0043] Example 4

[0044] A method for preparing a potassium-ion battery anode composite material includes the following steps:

[0045] (1) Indium nitrate hydrate and terephthalic acid were dissolved in N,N-dimethylformamide solution, followed by sodium acetate solution. The mixture was heated at 115°C for 3 hours. The mixture was collected and washed with deionized water by centrifugation at 7500 rpm for 5 minutes and 8 times. The washed precipitate was then vacuum dried at 80°C for 10 hours to obtain the precursor In-MOF.

[0046] (2) Under an argon atmosphere, the temperature was increased from room temperature to 450°C at a heating rate of 1°C / min, and the reaction was kept at a constant temperature for 5 hours. The temperature was then naturally cooled to room temperature. The In-MOF was sulfided into In2S3 / C material using thioacetamide (C2H5NS). The mass ratio of thioacetamide to In-MOF was 5:1.

[0047] (3) Weigh urea and In2S3 / C material in a mass ratio of 8:1, place them in their respective crucibles and put them in the furnace tube of a micro-tube furnace, with the urea at the upper air inlet and the In2S3 / C material at the lower air inlet. Then, evacuate the furnace tube to remove the air inside, and finally introduce argon gas into the tube. Set the working procedure: heat from room temperature to 400℃ at a heating rate of 6℃ / min, and react at a constant temperature for 5 hours. Then, cool naturally to room temperature to obtain N-In2S3 / C composite material.

[0048] Example 5

[0049] A method for preparing a potassium-ion battery anode composite material includes the following steps:

[0050] (1) Indium nitrate hydrate and terephthalic acid were dissolved in N,N-dimethylformamide solution, followed by sodium acetate solution. The mixture was heated at 125°C for 2.5 hours. The mixture was collected and washed with deionized water by centrifugation at 8500 rpm for 4 minutes and 7 times. The washed precipitate was dried under vacuum at 75°C for 11 hours to obtain the precursor In-MOF.

[0051] (2) Under an argon atmosphere, the temperature was increased from room temperature to 425°C at a heating rate of 1.5°C / min, and the reaction was kept at a constant temperature for 5.5 hours. The mixture was then naturally cooled to room temperature. The In-MOF was then sulfided into an In2S3 / C material using thioacetamide (C2H5NS). The mass ratio of thioacetamide to In-MOF was 5:1.

[0052] (3) Weigh urea and In2S3 / C material in a mass ratio of 12:1, place them in their respective crucibles and put them in the furnace tube of a micro-tube furnace, with the urea at the upper air inlet and the In2S3 / C material at the lower air inlet. Then, evacuate the furnace tube to remove the air inside the tube, and finally introduce argon gas into the tube. Set the working procedure: heat from room temperature to 550℃ at a heating rate of 5.5℃ / min, and react at a constant temperature for 7 hours. Then, cool naturally to room temperature to obtain N-In2S3 / C composite material.

[0053] Of the above embodiments, the preferred embodiment is Embodiment 3.

[0054] Comparative Example 2

[0055] The remaining steps of this comparative example are the same as those in Example 3, except that in step (3), the mass ratio of urea to In2S3 / C material is 30:1. X-ray diffraction analysis revealed that the obtained product is a mixture of N-In2S3 / C composite material and a small amount of InN.

[0056] Further testing of the electrochemical performance of Comparative Example 2 revealed that its rate performance at different current densities was not as good as that of Example 3, and its recovery ability was also poor. Furthermore, at 0.5 Ag... -1 After several dozen cycles, the specific capacity had already dropped to 200mAh g. -1 The cycling performance of the materials prepared in Comparative Example 2 is far inferior to that of Example 3 under the same conditions. These results indicate that the materials prepared in Comparative Example 2 not only produce impurity phases, but their electrochemical properties are also far inferior to those of the materials prepared in Example 3.

Claims

1. A method for preparing a potassium-ion battery anode composite material, characterized in that, Includes the following steps: (1) Dissolve indium hydrate and terephthalic acid in N,N-dimethylformamide solution, then add sodium acetate solution, heat to react, collect the mixture, centrifuge and wash, take the washed precipitate and dry to obtain the precursor In-MOF; (2) In-MOF is vulcanized into In2S3 / C material by thioacetamide in an argon atmosphere at 400~450℃, wherein the mass ratio of thioacetamide to In-MOF is 4~5:1; (3) Nitrogen doping of In2S3 / C material with urea was carried out in an argon atmosphere at 300~600℃ to obtain N-In2S3 / C composite material; In step (3), the mass ratio of urea to In2S3 / C material is 5~15:1; the temperature is increased from room temperature to 300~600℃ at a heating rate of 5~6℃ / min, and the reaction is kept at a constant temperature for 5~7 hours, and then naturally cooled to room temperature.

2. The method for preparing a potassium-ion battery negative electrode composite material according to claim 1, characterized in that: In step (1), the heating reaction temperature is 115~125℃ and the reaction time is 2~3 hours.

3. The method for preparing a potassium-ion battery negative electrode composite material according to claim 1, characterized in that: In step (1), the centrifugation speed is 7500~8500 rpm.

4. The method for preparing a potassium-ion battery negative electrode composite material according to claim 1, characterized in that: In step (1), the washing time is 3-5 minutes, the number of washing cycles is 6-8, and deionized water is used for washing.

5. The method for preparing a potassium-ion battery negative electrode composite material according to claim 1, characterized in that: In step (1), the drying is vacuum drying, the drying temperature is 70~80℃, and the drying time is 10~12 hours.

6. The method for preparing a potassium-ion battery negative electrode composite material according to claim 1, characterized in that: In step (2), the temperature is increased from room temperature to 400-450°C at a heating rate of 1-2°C / minute, and the temperature is kept constant for 5-6 hours before naturally cooling to room temperature.

7. The potassium-ion battery anode composite material obtained by the preparation method according to any one of claims 1 to 6, characterized in that: The N-In2S3 is uniformly coated with a C matrix.

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