Two-dimensional porous silicon, its preparation method and application in lithium battery

Abstract

This invention discloses a two-dimensional porous silicon, its preparation method, and its application in lithium batteries, belonging to the field of materials technology. The silicon-calcium alloy powder is immersed in hydrochloric acid solution, and after the reaction is complete, it is filtered and dried to obtain siloxane powder. The siloxane powder is then heat-treated in a vacuum environment, during which the siloxane is first oxidized to SiO. x SiO x Further high-temperature processing leads to a disproportionation reaction, generating uniformly distributed two-dimensional Si / SiO2. The two-dimensional Si / SiO2 is then immersed in a hydrofluoric acid solution, where the hydrofluoric acid reacts with the SiO2. After complete reaction, the mixture is repeatedly centrifuged and washed, then vacuum dried to obtain a two-dimensional silicon material with a porous structure. The preparation method of this invention is simple, controllable, and highly practical. The two-dimensional porous silicon prepared by this method possesses a crystalline structure and an ultrathin layered structure, which can effectively mitigate volume changes in the negative electrode material and accelerate lithium-ion diffusion when used in lithium-ion batteries.

Description

Technical Field

[0001] This invention belongs to the field of materials technology, specifically relating to a two-dimensional porous silicon, its preparation method, and its application in lithium batteries. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Silicon, with its high theoretical specific capacity, is one of the most promising anode materials for lithium-ion batteries. However, silicon anodes experience volume changes of up to 300% during lithium insertion / extraction, leading to particle breakage and the shedding of active material from the electrode, all of which cause rapid capacity decay. Two-dimensional porous structures can effectively mitigate the volume expansion of silicon materials during charging and discharging, and also provide more lithium-ion transport channels, improving the lithium-ion transport rate. Therefore, two-dimensional porous silicon materials are widely used as silicon anodes. Patent CN 115403046 A discloses a two-dimensional silicon structure, but the ion propagation speed in the direction perpendicular to the layers is slow, hindering its application in batteries.

[0004] Therefore, optimizing the properties of two-dimensional porous silicon and the transport rate of feed ions in the material are of great significance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a two-dimensional porous silicon, its preparation method, and its application in lithium batteries. The two-dimensional porous silicon preparation method of the present invention, through acid etching, can accelerate the transport of ions in the material. It is simple to prepare, highly practical, and easy to promote.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A first aspect of the present invention provides a method for preparing two-dimensional porous silicon, comprising:

[0008] The silicon-calcium alloy powder was soaked in an acidic solution, filtered, and vacuum dried to obtain siloxane powder.

[0009] The siloxane powder was heat-treated in a vacuum environment to obtain two-dimensional Si / SiO2.

[0010] The two-dimensional Si / SiO2 is immersed in hydrofluoric acid solution, centrifuged, and vacuum dried to obtain a two-dimensional porous silicon material.

[0011] In some embodiments of the present invention, the chemical formula of the silicon-calcium alloy powder is CaSi2.

[0012] In some embodiments of the present invention, the acidic solution includes one of hydrochloric acid, sulfuric acid, oxalic acid, nitric acid, perchloric acid, hypochlorous acid, and phosphoric acid.

[0013] In some embodiments of the present invention, the acid is a hydrochloric acid solution with a concentration of 12-37 wt%.

[0014] In some embodiments of the present invention, the vacuum drying conditions are a temperature of 60-80°C, a time of 8-12 hours, and a vacuum degree of 0.2-0.5 Pa.

[0015] In some embodiments of the present invention, the heat treatment conditions are a temperature of 300-1000°C and a time of 6-15 hours. Preferably, the heat treatment process is a gradient heating process. During the heating process, the siloxane can be fully oxidized to SiO. x SiO x Further high-temperature processing leads to a disproportionation reaction that generates uniformly distributed two-dimensional Si / SiO2. Compared to holding at a fixed temperature, gradient heating allows for a more complete reaction and increases the yield of two-dimensional porous silicon.

[0016] In some embodiments of the present invention, the concentration of the hydrofluoric acid solution is 5-15 wt%. The silica generated during the disproportionation process can be removed using hydrofluoric acid, and the two-dimensional porous silicon is obtained after the reaction is complete.

[0017] In some embodiments of the present invention, the mass-to-volume ratio of the two-dimensional Si / SiO2 to the hydrofluoric acid solution is 0.6g:40-120mL.

[0018] In a second aspect, the present invention provides two-dimensional porous silicon prepared by the above-described method for preparing two-dimensional porous silicon.

[0019] A third aspect of the present invention provides the application of the above-described two-dimensional porous silicon in lithium batteries. Preferably, the application is that the two-dimensional porous silicon serves as the negative electrode of the lithium battery.

[0020] The beneficial effects of this invention are as follows:

[0021] (1) The precursors used in this invention are all commercial samples, and the preparation method is simple and controllable, and they have great potential for application in lithium-ion battery anodes.

[0022] (2) The two-dimensional porous silicon of the present invention utilizes topological chemical reaction to convert silicon-calcium alloy into siloxane. During the heating process, the siloxane is first oxidized to SiO. x SiO xFurther high-temperature processing results in a disproportionation reaction that generates uniformly distributed two-dimensional Si / SiO2. The silica produced during disproportionation can be removed using hydrofluoric acid. The two-dimensional porous silicon prepared by this method exhibits both a crystalline structure and an ultrathin layered structure.

[0023] Patent CN 115403046 A utilizes the thermal reaction between calcium and nitrogen in a silicon-calcium alloy, with nitrogen acting as a reactant to remove calcium. The resulting calcium nitride is then removed using dilute hydrochloric acid to prepare two-dimensional silicon. This method primarily utilizes SiO₂. x A disproportionation reaction occurs at high temperatures, and the generated SiO2 can be removed using hydrofluoric acid. After the reaction is complete, two-dimensional porous silicon can be obtained. Furthermore, the method for preparing two-dimensional porous silicon in this invention, through acid etching, can accelerate ion transport in the material. The preparation method is simple, practical, and easy to promote.

[0024] (3) The two-dimensional porous silicon of the present invention can effectively alleviate the volume change of the negative electrode material and accelerate the diffusion of lithium ions when used as a lithium-ion battery. Attached Figure Description

[0025] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0026] Figure 1 This is a SEM image of the siloxane produced by the reaction of silicon-calcium alloy with hydrochloric acid in Example 1.

[0027] Figure 2 This is a SEM image of two-dimensional Si / SiO2 after heat treatment of siloxane in Example 1.

[0028] Figure 3 This is a SEM image of the two-dimensional porous silicon in Example 1.

[0029] Figure 4 The cycling performance diagram is shown for the two-dimensional Si / SiO2 anode prepared in Example 1.

[0030] Figure 5 The coulombic efficiency diagram of the two-dimensional Si / SiO2 anode prepared in Example 1. Detailed Implementation

[0031] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0032] A method for preparing two-dimensional porous silicon, comprising:

[0033] (1) The silicon-calcium alloy powder was soaked in an acidic solution, filtered, and vacuum dried to obtain silicon oxide powder;

[0034] (2) The above-mentioned siloxane powder was heat-treated in a vacuum environment to obtain two-dimensional Si / SiO2;

[0035] (3) The above two-dimensional Si / SiO2 was soaked in hydrofluoric acid solution, centrifuged and vacuum dried to obtain two-dimensional porous silicon.

[0036] In some embodiments, the heat treatment conditions are: temperature 300-1000℃, time 6-15h;

[0037] In some embodiments, the concentration of the hydrochloric acid solution is 12-37 wt%;

[0038] In some embodiments, the concentration of the hydrofluoric acid solution is 5-15 wt%.

[0039] In some embodiments, the mass-to-volume ratio of the reaction product to hydrofluoric acid is 0.6:40 to 120 (g:mL).

[0040] In some embodiments, the specific conditions for vacuum drying are: temperature 60-80°C, time 8-12 hours, and vacuum degree 0.2-0.5 Pa.

[0041] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0042] Example 1

[0043] A method for preparing two-dimensional porous silicon is as follows:

[0044] (1) The silicon-calcium alloy powder was soaked in a 37wt% concentrated hydrochloric acid solution, filtered, and then vacuum dried for 12h at 80℃ and 0.2Pa to obtain silicon oxide powder. Figure 1 The image shows a SEM image of siloxane, and the sheet-like structure confirms the successful preparation of siloxane.

[0045] (2) The above-mentioned siloxane powder was subjected to a vacuum environment at 5°C for 5 min. -1 The heating rates were adjusted, and two-dimensional Si / SiO2 was obtained by holding at 300℃, 400℃, and 900℃ for 3h, 2h, and 1h, respectively. Figure 2 The SEM images of the two-dimensional Si / SiO2 also show a two-dimensional structure.

[0046] (3) Soak 0.6g of the above two-dimensional Si / SiO2 in 50mL of 10wt% hydrofluoric acid solution, centrifuge, and then vacuum dry for 12h at 80℃ and 0.2Pa to obtain two-dimensional porous silicon. Figure 3 SEM images of the two-dimensional porous silicon show that the SiO2 in the two-dimensional Si / SiO2 was successfully etched, and the sample exhibits a two-dimensional porous structure.

[0047] (4) Two-dimensional porous silicon is used as the negative electrode active material, lithium sheet is used as the counter electrode and reference electrode, and the electrolyte is 1M LiPF6+DC:DEC(1:1) with 10% FEC, with a voltage range of 0.01V-3.0V. Figure 4 and Figure 5 This indicates that at 200mAg -1 Under the test conditions of current density, after 200 cycles, the battery capacity is 838.4 mAh g. -1 The coulombic efficiency is 99.58%, demonstrating the excellent electrochemical performance of this material.

[0048] Example 2

[0049] A method for preparing two-dimensional porous silicon is as follows:

[0050] (1) The silicon-calcium alloy powder was soaked in a 37wt% concentrated hydrochloric acid solution, filtered, and then vacuum dried for 12h at 80℃ and 0.2Pa to obtain silicon oxide powder.

[0051] (2) The above-mentioned siloxane powder was subjected to a vacuum environment at 5°C for 5 min. -1 The heating rates were adjusted to allow for holding at 300℃, 800℃, and 900℃ for 2 hours, 2 hours, and 2 hours respectively to obtain two-dimensional Si / SiO2.

[0052] (3) Soak 0.6g of the above two-dimensional Si / SiO2 in 50mL of 10wt% hydrofluoric acid solution, centrifuge, and then vacuum dry for 12h at 80℃ and 0.2Pa to obtain two-dimensional porous silicon.

[0053] Example 3

[0054] A method for preparing two-dimensional porous silicon is as follows:

[0055] (1) The silicon-calcium alloy powder was soaked in a 37wt% concentrated hydrochloric acid solution, filtered, and then vacuum dried for 12h at 80℃ and 0.2Pa to obtain silicon oxide powder.

[0056] (2) The above-mentioned siloxane powder was subjected to a vacuum environment at 5°C for 5 min. -1The heating rate was adjusted, and two-dimensional Si / SiO2 was obtained by holding at 300℃, 800℃, and 1000℃ for 2h, 2h, and 2h, respectively.

[0057] (3) Soak 0.6g of the above two-dimensional Si / SiO2 in 50mL of 10wt% hydrofluoric acid solution, centrifuge, and then vacuum dry for 12h at 80℃ and 0.2Pa to obtain two-dimensional porous silicon.

[0058] Example 4

[0059] A method for preparing two-dimensional porous silicon is as follows:

[0060] (1) The silicon-calcium alloy powder was soaked in a 37wt% concentrated hydrochloric acid solution, filtered, and then vacuum dried for 12h at 80℃ and 0.2Pa to obtain silicon oxide powder.

[0061] (2) The above-mentioned siloxane powder was subjected to a vacuum environment at 5°C for 5 min. -1 The heating rate was adjusted, and two-dimensional Si / SiO2 was obtained by holding at 300℃, 400℃, and 900℃ for 3h, 2h, and 3h, respectively.

[0062] (3) Soak 0.6g of the above two-dimensional Si / SiO2 in 50mL of 10wt% hydrofluoric acid solution, centrifuge, and then vacuum dry for 12h at 80℃ and 0.2Pa to obtain two-dimensional porous silicon.

[0063] Example 5

[0064] A method for preparing two-dimensional porous silicon is as follows:

[0065] (1) The silicon-calcium alloy powder was soaked in a 37wt% concentrated hydrochloric acid solution, filtered, and then vacuum dried for 12h at 80℃ and 0.2Pa to obtain silicon oxide powder.

[0066] (2) The above-mentioned siloxane powder was subjected to a vacuum environment at 10°C for 1 minute. -1 The heating rate was adjusted, and two-dimensional Si / SiO2 was obtained by holding at 300℃, 400℃, and 900℃ for 3h, 2h, and 6h, respectively.

[0067] (3) Soak 0.6g of the above two-dimensional Si / SiO2 in 50mL of 15wt% hydrofluoric acid solution, centrifuge, and then vacuum dry for 12h at 80℃ and 0.2Pa to obtain two-dimensional porous silicon.

[0068] Example 6

[0069] A method for preparing two-dimensional porous silicon is as follows:

[0070] (1) The silicon-calcium alloy powder was soaked in a 37wt% concentrated hydrochloric acid solution, filtered, and then vacuum dried for 12h at 80℃ and 0.2Pa to obtain silicon oxide powder.

[0071] (2) The above-mentioned siloxane powder was subjected to a vacuum environment at 10°C for 1 minute. -1 The heating rates were adjusted to obtain two-dimensional Si / SiO2 by holding at 300℃, 800℃, and 1000℃ for 3h, 2h, and 6h, respectively.

[0072] (3) Soak 0.6g of the above two-dimensional Si / SiO2 in 50mL of 15wt% hydrofluoric acid solution, centrifuge, and then vacuum dry for 12h at 80℃ and 0.2Pa to obtain two-dimensional porous silicon.

[0073] Example 7

[0074] A method for preparing two-dimensional porous silicon is as follows:

[0075] (1) The silicon-calcium alloy powder was soaked in a 37wt% concentrated hydrochloric acid solution, filtered, and then vacuum dried for 12h at 80℃ and 0.2Pa to obtain silicon oxide powder.

[0076] (2) The above-mentioned siloxane powder was subjected to a vacuum environment at 10°C for 1 minute. -1 The heating rates were adjusted to obtain two-dimensional Si / SiO2 by holding at 300℃, 800℃, and 900℃ for 3h, 2h, and 1h, respectively.

[0077] (3) Soak 0.6g of the above two-dimensional Si / SiO2 in 50mL of 15wt% hydrofluoric acid solution, centrifuge, and then vacuum dry for 12h at 80℃ and 0.2Pa to obtain two-dimensional porous silicon.

[0078] Example 8

[0079] A method for preparing two-dimensional porous silicon is as follows:

[0080] (1) The silicon-calcium alloy powder was soaked in a 37wt% concentrated hydrochloric acid solution, filtered, and then vacuum dried for 12h at 80℃ and 0.2Pa to obtain silicon oxide powder.

[0081] (2) The above-mentioned siloxane powder was subjected to a vacuum environment at 5°C for 5 min. -1 The heating rates were adjusted to obtain two-dimensional Si / SiO2 by holding at 300℃, 800℃, and 900℃ for 2h, 2h, and 6h, respectively.

[0082] (3) Soak 0.6g of the above two-dimensional Si / SiO2 in 50mL of 15wt% hydrofluoric acid solution, centrifuge, and then vacuum dry for 12h at 80℃ and 0.2Pa to obtain two-dimensional porous silicon.

[0083] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing two-dimensional porous silicon, characterized in that, include: The silicon-calcium alloy powder was soaked in an acidic solution, filtered, and vacuum dried to obtain siloxane powder. The siloxane powder was heat-treated in a vacuum environment to obtain two-dimensional Si / SiO2; the vacuum drying conditions were a temperature of 60-80℃, a time of 8-12 h, and a vacuum degree of 0.2-0.5 Pa; the heat treatment was a gradient temperature increase; the two-dimensional Si / SiO2 was then immersed in hydrofluoric acid solution, centrifuged, and vacuum-dried to obtain a two-dimensional porous silicon material; the two-dimensional porous silicon material has a crystalline structure and an ultrathin layered structure. The gradient heating is as follows: holding at 300℃, 400℃, and 900℃ for 3 h, 2 h, and 1 h respectively; or holding at 300℃, 800℃, and 900℃ for 2 h, 2 h, and 2 h respectively; or holding at 300℃, 800℃, and 1000℃ for 2 h, 2 h, and 2 h respectively; or holding at 300℃, 400℃, and 900℃ for 3 h, 2 h, and 3 h respectively; or holding at 300℃, 400℃, and 900℃ for 3 h, 2 h, and 6 h respectively; or holding at 300℃, 800℃, and 1000℃ for 3 h, 2 h, and 6 h respectively; or holding at 300℃, 800℃, and 900℃ for 3 h, 2 h, and 1 h respectively; or holding at 300℃, 800℃, and 900℃ for 2 h, 2 h, and 6 h respectively.

2. The method for preparing two-dimensional porous silicon as described in claim 1, characterized in that, The chemical formula of the silicon-calcium alloy powder is CaSi2.

3. The method for preparing two-dimensional porous silicon as described in claim 1, characterized in that, The acidic solution includes one of hydrochloric acid, sulfuric acid, oxalic acid, nitric acid, perchloric acid, hypochlorous acid, and phosphoric acid.

4. The method for preparing two-dimensional porous silicon as described in claim 1, characterized in that, The acid is hydrochloric acid, and the concentration of hydrochloric acid is 12-37 wt%.

5. The method for preparing two-dimensional porous silicon as described in claim 1, characterized in that, The concentration of the hydrofluoric acid solution is 5-15 wt%.

6. The method for preparing two-dimensional porous silicon as described in claim 1, characterized in that, The mass-to-volume ratio of the two-dimensional Si / SiO2 to the hydrofluoric acid solution is 0.6 g: 40-120 mL.

7. Two-dimensional porous silicon prepared by the method for preparing two-dimensional porous silicon according to any one of claims 1-6.

8. The application of the two-dimensional porous silicon as described in claim 7 in lithium batteries.

9. The application as described in claim 8, characterized in that, The application is that two-dimensional porous silicon is used as the negative electrode of a lithium battery.

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