A silicon-air battery using a silicon MIL-88 composite material as an anode and a preparation method thereof

Abstract

The present invention provides a silicon-air battery using a silicon-MIL-88 composite material as the anode and a preparation method thereof, comprising the following steps: uniformly dissolving FeCl3·6H2O and fumaric acid in deionized water to obtain solution I; placing single crystal silicon in solution I, and then heating solution I in oil at a specific temperature and time. This allows MIL-88 to be evenly deposited on the smooth surface of the silicon wafer, followed by simple cleaning and drying to obtain a silicon / MIL-88 composite electrode material. This composite material is used as the air battery anode, and a KOH aqueous solution is used as the electrolyte, combined with a platinum-carbon cathode to form a novel silicon-air battery. Electrochemical testing revealed that the discharge voltage of this air battery did not change significantly compared to an air battery assembled from a blank silicon wafer, but the actual discharge time was improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery preparation, and in particular to a silicon-air battery using a silicon MIL-88 composite material as an anode and a preparation method thereof. Background Art

[0002] At present, among various battery energy sources, air batteries have a higher theoretical energy density than traditional batteries and lithium batteries because their reactants are oxygen molecules, which can be fully replenished in the air. Therefore, air batteries are more popular among primary batteries. At present, air batteries are mainly composed of metal-air batteries and semiconductor-air batteries. However, the uneven metal deposition in metal batteries will lead to the growth of dendrites. The growth of dendrites will cause the battery to short-circuit, leaving a hidden danger of fire. The silicon-air battery in the semiconductor air battery will not generate dendrites on the anode surface, thus eliminating the occurrence of such safety hazards. Secondly, silicon-air batteries have a higher theoretical energy density (8470Wh·kg -1 ), and the content of silicon is at the forefront in the earth's crust. The reaction product is SiO2, which is a common substance with little impact on the environment and can be reused, so silicon-air batteries have huge development potential.

[0003] However, self-corrosion reaction and passivation reaction on the surface of silicon anode always accompany the discharge process. These two reactions often lead to ineffective loss of anode and premature termination of discharge process, resulting in a reduction in the actual capacity of the battery, which seriously affects the practical application of the battery. Therefore, it is crucial to coat the silicon anode with a protective film.

[0004] MIL-88 is a three-dimensional framework material composed of Fe elements, which has a wide specific surface area and large pore size. The pore size of MIL-88 can ensure OH - This free movement prevents larger water molecules from coming into direct contact with the single-crystal silicon, thereby slowing down the self-corrosion reaction and reducing ineffective silicon consumption. MIL-88's large surface area also provides more reactive sites for the anodic oxidation reaction. Furthermore, MIL-88 maintains stable physical properties in environments with a pH of 2 to 12.

[0005] Therefore, if MIL-88 is used in the anode of silicon-air batteries, it is expected to reduce the ineffective loss of silicon wafers, inhibit the passivation reaction, and extend the actual discharge time. However, how to compound MIL-88 onto the surface of silicon anodes and assemble them into silicon-air batteries has become an urgent problem to be solved. Summary of the Invention

[0006] The purpose of the present invention is to provide a silicon-air battery with a silicon MIL-88 composite material as the anode and a preparation method thereof. An oil bath method is used to form MIL-88 rod-shaped crystals on the surface of a silicon wafer. MIL-88 can directly prevent direct contact between silicon and water molecules, effectively inhibiting self-corrosion reactions, while isolating the direct deposition of SiO2 generated by the passivation reaction, thereby extending the actual discharge time.

[0007] According to one object of the present invention, the present invention provides a method for preparing a silicon-air battery using a silicon MIL-88 composite material as an anode, comprising the following steps:

[0008] S1, Preparation of silicon / MIL-88 composite anode

[0009] S101, weighing appropriate amounts of FeCl3·6H2O and fumaric acid into a beaker, adding deionized water to the beaker and stirring to obtain solution I;

[0010] S102, placing the cleaned silicon wafer with the polished surface facing upward into solution I and heating;

[0011] S103, cooling to room temperature after heating, taking out the silicon wafer, cleaning it, and drying it;

[0012] S2, Preparation of KOH Electrolyte

[0013] Place the weighed solid KOH into a beaker, add an appropriate amount of deionized water and stir to accelerate heat dissipation until the beaker wall is no longer hot, and pour the KOH in the beaker into a volumetric flask to make up the volume;

[0014] S3, Preparation of Pt / C cathode

[0015] An appropriate amount of platinum-carbon catalyst was weighed and placed in a beaker. Naphthol solution was first added to the beaker using a pipette, followed by isopropyl alcohol. The beaker containing the three substances was placed in an ultrasonic bath for ultrasonic dissolution. The dissolved solution was evenly applied to carbon paper using a pipette and then dried at room temperature to prepare a Pt / C cathode.

[0016] S4, Assembly of air battery

[0017] The silicon / MIL-88 composite anode and Pt / C cathode obtained above were assembled on an air battery mold, and then KOH solution was added to the electrolytic cell using a dropper to obtain a silicon-air battery.

[0018] Furthermore, in S1, the molar ratio of FeCl3·6H2O to fumaric acid is 0.8 to 1.2.

[0019] Furthermore, in S1, the concentration of the FeCl3·6H2O solution is 10 to 100 mmol / L, and the concentration of the fumaric acid solution is 10 to 100 mmol / L.

[0020] Furthermore, in S1, the mixture in the beaker is stirred for 30 to 45 minutes to obtain solution I.

[0021] Furthermore, in S1, the silicon wafer has a diameter of 10 to 70 mm, a thickness of 200 to 800 μm, and is doped with arsenic, boron, or phosphorus. After the silicon wafer is placed in a beaker, it is heated at 95 to 105° C. for 240 to 270 minutes. The heated solution is naturally cooled to 18 to 20° C. in silicone oil.

[0022] Furthermore, in S1, after the solution is cooled, the silicon wafer in the beaker is taken out and rinsed repeatedly with anhydrous ethanol and deionized water in sequence.

[0023] Furthermore, in S1, the cleaned silicon wafer is placed in a vacuum environment at 60-80° C. and dried for 10-15 minutes.

[0024] Furthermore, in S2, the concentration of KOH is 1.5 to 6 mol / L.

[0025] Furthermore, in S3, the amount of the platinum-carbon catalyst used is 2-5 mg, the amount of the naphthol solution used is 600-800 μL, and the amount of isopropanol used is 200-400 μL.

[0026] According to another object of the present invention, the present invention provides a silicon-air battery with a silicon MIL-88 composite material as an anode, which is prepared using the above method.

[0027] Beneficial effects

[0028] The present invention can control the morphology of surface MIL-88 growth on a silicon wafer by controlling the amounts of FeCl3·6H2O and fumaric acid. Using an oil bath for heating provides a uniform and stable heating source, allowing the MIL-88 to be evenly distributed on the silicon wafer surface and resisting detachment. The method provided by the present invention is simple and reliable, suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A model diagram of a battery prepared according to an embodiment of the present invention.

[0030] Figure 2 This is an electron microscope image of the silicon / MIL-88 composite electrode obtained in an embodiment of the present invention before discharge.

[0031] Figure 3 This is an electron microscope image of the silicon / MIL-88 composite electrode obtained in an embodiment of the present invention after discharge for 50 hours.

[0032] Figure 4The composite silicon anode obtained by the present invention in Example 2 with the concentrations of FeCl3·6H2O and fumaric acid being 30 mmol / L was heated at a current density of 150 μA / cm 2 The constant current discharge test diagram below.

[0033] Figure 5 The composite silicon anode obtained by the present invention in Example 3 with the concentrations of FeCl3·6H2O and fumaric acid being 70mmol / L was heated at a current density of 150μA / cm 2 The constant current discharge test diagram below. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate directions or positional relationships are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as limiting the present invention.

[0036] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the said features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a communication between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0037] Example 1

[0038] A method for preparing a silicon-air battery using a silicon MIL-88 composite material as an anode comprises the following steps:

[0039] 1) Ultrasonic cleaning of single crystal silicon wafers with methanol and ethanol for 5 to 10 minutes to remove organic impurities on the surface. The wafers are then placed in a mixture of concentrated sulfuric acid and hydrogen peroxide (3:1) for 120 to 150 minutes and hydrofluoric acid for 2 to 5 minutes to remove the surface oxide layer. The wafers are then ultrasonically cleaned in methanol and ethanol for 5 to 10 minutes to remove any residual hydrofluoric acid on the wafer surface.

[0040] 2) Using a weighing balance, FeCl₃·6H₂O and fumaric acid are weighed in a mass ratio of 0.8 to 1.2 and placed in a beaker. Deionized water is then added to the beaker to adjust the concentrations of the FeCl₃·6H₂O and fumaric acid to 10 to 100 mmol / L, respectively. The beaker is placed on a magnetic stirrer and stirred for 30 to 45 minutes to uniformly mix the FeCl₃·6H₂O and fumaric acid.

[0041] 3) Place the cleaned single crystal silicon wafer with the polished surface facing upward into a uniform FeCl3·6H2O and fumaric acid solution;

[0042] 4) Place the beaker containing the single crystal silicon wafer, FeCl3·6H2O, and fumaric acid solution in a heating dish filled with silicone oil. Turn on the thermostatic heating stirrer and set the temperature to 95-105°C to maintain a constant temperature during the heating process. Place the raw materials in the thermostatic heater for 240-270 minutes.

[0043] 5) After heating, turn off the constant temperature heating stirrer switch and allow it to cool naturally to 18-20°C until the solution turns orange-yellow. Use tweezers to remove the silicon wafer from the solution, and repeatedly rinse the silicon wafer with anhydrous ethanol and deionized water to remove impurities remaining on the surface. Thereafter, place the silicon wafer in a vacuum oven with air evacuated and dry it in a vacuum environment at 50-70°C for 10-15 minutes to obtain a silicon / MIL-88 composite material.

[0044] Example 2:

[0045] The single crystal silicon wafer was ultrasonically cleaned with methanol and ethanol for 10 minutes in sequence to remove organic impurities on the surface. It was then placed in a mixed solution of concentrated sulfuric acid and hydrogen peroxide (3:1) and hydrofluoric acid for 2 hours and 5 minutes respectively to remove the surface oxide layer. The silicon wafer was then ultrasonically cleaned in methanol and ethanol for 10 minutes again in sequence to remove the hydrofluoric acid remaining on the surface of the silicon wafer.

[0046] Use a weighing balance to weigh 1.5 mmol of FeCl3·6H2O and fumaric acid respectively into a beaker. Then use a measuring cylinder to measure 50 ml of deionized water and pour it into the beaker. Place the beaker on a magnetic stirrer and stir for 30 minutes to allow FeCl3·6H2O and fumaric acid to be evenly dissolved in the deionized water.

[0047] Place the cleaned single crystal silicon wafer with the polished surface facing up into a uniform FeCl3·6H2O and fumaric acid solution. Wrap plastic wrap around the mouth of the beaker and poke uniform small holes in the plastic wrap so that the atmospheric pressure in the beaker is consistent with the atmospheric pressure in the air.

[0048] Place the beaker containing the single crystal silicon wafer, FeCl3·6H2O and fumaric acid solution in a heating dish filled with silicone oil, turn on the constant temperature heating stirrer and set the temperature to 100℃ so that the temperature can be kept constant during the heating process, and place the raw materials in the beaker in the constant temperature heater for 4 hours.

[0049] After heating, turn off the constant temperature heating stirrer switch and let it cool naturally to 18°C until the solution turns orange-yellow. Use tweezers to take out the silicon wafer from the solution, and repeatedly rinse the silicon wafer with anhydrous ethanol and deionized water to remove impurities remaining on the surface. Then, place the silicon wafer in a vacuum environment at 60°C and dry it for 15 minutes to obtain a silicon / MIL-88 composite material.

[0050] Figure 2 This is a plane electron microscope image of the silicon / MIL-88 composite material prepared in Example 2. Figure 3 This is a plane electron microscope image of Example 2 after 50 hours of discharge, as shown in FIG. Figure 2 As shown, through the electron microscope image, it can be observed that the MIL-88 material has been successfully compounded with the silicon wafer to form a battery anode.

[0051] Example 3:

[0052] The single crystal silicon wafer was ultrasonically cleaned with methanol and ethanol for 10 minutes in sequence to remove organic impurities on the surface. It was then placed in a mixed solution of concentrated sulfuric acid and hydrogen peroxide (3:1) and hydrofluoric acid for 2 hours and 5 minutes respectively to remove the surface oxide layer. The silicon wafer was then ultrasonically cleaned in methanol and ethanol for 10 minutes again in sequence to remove the hydrofluoric acid remaining on the surface of the silicon wafer.

[0053] Use a weighing balance to weigh 3.5 mmol of FeCl3·6H2O and fumaric acid respectively into a beaker. Then use a measuring cylinder to measure 50 ml of deionized water and pour it into the beaker. Place the beaker on a magnetic stirrer and stir for 30 minutes to allow FeCl3·6H2O and fumaric acid to be evenly dissolved in the deionized water.

[0054] Place the cleaned single crystal silicon wafer with the polished surface facing up into a uniform FeCl3·6H2O and fumaric acid solution. Wrap plastic wrap around the mouth of the beaker and poke uniform small holes in the plastic wrap so that the atmospheric pressure in the beaker is consistent with the atmospheric pressure in the air.

[0055] Place the beaker containing the single crystal silicon wafer, FeCl3·6H2O and fumaric acid solution in a heating dish filled with silicone oil, turn on the constant temperature heating stirrer and set the temperature to 100℃ so that the temperature can be kept constant during the heating process, and place the raw materials in the beaker in the constant temperature heater for 4 hours.

[0056] After heating, turn off the constant temperature heating stirrer switch and let it cool naturally to 18°C until the solution turns orange-yellow. Use tweezers to take out the silicon wafer from the solution, and repeatedly rinse the silicon wafer with anhydrous ethanol and deionized water to remove impurities remaining on the surface. Then, place the silicon wafer in a vacuum environment at 60°C and dry it for 15 minutes to obtain a silicon / MIL-88 composite material.

[0057] Weigh 2.8 mg of platinum-carbon catalyst using a balance, add 700 μL of naphthol solution using a pipette, then add 300 μL of isopropanol (note: the order cannot be changed), mix thoroughly, and then ultrasonicate for 90 to 120 minutes. Finally, add 10 ml of 6 mol KOH solution (such as Figure 1 shown).

[0058] Figure 4 At a current density of 150 μA / cm 2 When the discharge time of the composite silicon-air battery in Example 2 is compared with that of the blank silicon-air battery, as shown in FIG. Figure 4 As shown, at 150μA / cm 2 By constant current discharge at a current density of 1.5, it was found that compared with the air battery assembled with blank silicon wafers, the discharge voltage of this new silicon / MIL-88 air battery did not change significantly, and the discharge time was increased by one third (100-120h).

[0059] Figure 5 The current density is 150μA / cm 2 When the discharge time of the composite silicon-air battery in Example 3 is compared with that of the blank silicon-air battery, as shown in FIG. Figure 5 As shown, at 150μA / cm 2 By constant current discharge at a current density of 100 nm, it was found that compared with the air battery assembled with blank silicon wafers, the discharge voltage of this new silicon / MIL-88 air battery did not change significantly, and the discharge time was increased by 30 h.

[0060] The present invention can control the morphology of surface MIL-88 growth on a silicon wafer by controlling the amounts of FeCl3·6H2O and fumaric acid. Using an oil bath for heating provides a uniform and stable heating source, allowing the MIL-88 to be evenly distributed on the silicon wafer surface and resisting detachment. The method provided by the present invention is simple and reliable, suitable for large-scale industrial production.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a silicon-air battery using a silicon MIL-88 composite material as an anode, characterized in that: The steps include: S1, Preparation of silicon / MIL-88 composite anode S101, weighing appropriate amounts of FeCl3·6H2O and fumaric acid into a beaker, adding deionized water to the beaker and stirring to obtain a solution I; the molar ratio of FeCl3·6H2O to fumaric acid is 0.8 to 1.2; The concentration of FeCl3·6H2O solution is 10~100mmol / L, and the concentration of fumaric acid solution is 10~100mmol / L; S102, placing the cleaned silicon wafer with the polished surface facing upward into solution I and heating it; the silicon wafer has a diameter of 10 to 70 mm, a thickness of 200 to 800 μm, and is doped with arsenic, boron, or phosphorus; the silicon wafer is placed in a beaker and heated in an environment of 95 to 105° C. for 240 to 270 minutes; the heated solution is naturally cooled to 18 to 20° C. in silicone oil; S103, cooling to room temperature after heating, taking out the silicon wafer, cleaning it, and drying it; S2, Preparation of KOH Electrolyte Place the weighed solid KOH into a beaker, add an appropriate amount of deionized water and stir to accelerate heat dissipation until the beaker wall is no longer hot, and pour the KOH in the beaker into a volumetric flask to make up the volume; S3, Preparation of Pt / C cathode An appropriate amount of platinum-carbon catalyst was weighed and placed in a beaker. Naphthol solution was first added to the beaker using a pipette, followed by isopropyl alcohol. The beaker containing the three substances was placed in an ultrasonic bath for ultrasonic dissolution. The dissolved solution was evenly applied to carbon paper using a pipette and then dried at room temperature to prepare a Pt / C cathode. S4, Assembly of air battery The silicon / MIL-88 composite anode and Pt / C cathode obtained above were assembled on an air battery mold, and then KOH solution was added to the electrolytic cell using a dropper to obtain a silicon-air battery.

2. The method for preparing a silicon-air battery using the silicon MIL-88 composite material as an anode according to claim 1, characterized in that: In S1, the mixture in the beaker is stirred for 30-45 min to obtain solution I.

3. The method for preparing a silicon-air battery using the silicon MIL-88 composite material as an anode according to claim 1, characterized in that: In S1, after the solution is cooled, the silicon wafer in the beaker is taken out and rinsed repeatedly with anhydrous ethanol and deionized water.

4. The method for preparing a silicon-air battery using the silicon MIL-88 composite material as an anode according to claim 1, characterized in that: In S1, the cleaned silicon wafer is placed in a vacuum environment at 60-80° C. and dried for 10-15 minutes.

5. The method for preparing a silicon-air battery using the silicon MIL-88 composite material as an anode according to claim 1, characterized in that: In S2, the concentration of KOH is 1.5 to 6 mol / L.

6. The method for preparing a silicon-air battery using the silicon MIL-88 composite material as an anode according to claim 1, characterized in that: In S3, the amount of platinum-carbon catalyst used is 2-5 mg, the amount of naphthol solution used is 600-800 μL, and the amount of isopropyl alcohol used is 200-400 μL.

7. A silicon-air battery with a silicon MIL-88 composite material as an anode, characterized in that: The silicon-air battery is prepared according to the preparation method of the silicon MIL-88 composite material as the anode according to any one of claims 1 to 6.

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