Silicon nanowire and preparation method and application thereof

Abstract

The invention provides a silicon nanowire and a preparation method and application thereof. The preparation method comprises the following steps: carrying out first evaporation on a silicon source to obtain silicon source steam, carrying out second evaporation on alloy ABx to obtain alloy steam, mixing the silicon source steam with the alloy steam, and reacting to obtain the silicon nanowire, wherein A is a reducing agent element and is selected from any one or a combination of at least two of Al, Mg or Zn, B is a catalyst element and is selected from any one or a combination of at least two of Au, Ag, Cu, Co, Ni, Fe, Ti, Nb, Sn, Al or Zn, and x is larger than or equal to 0.0001 and smaller than or equal to 3. The silicon nanowire is prepared in an alloy form, and the preparation process is simple and easy to control.

Description

Technical Field

[0001] The present invention belongs to the field of lithium ion batteries, and in particular relates to a silicon nanowire and a preparation method and application thereof. Background Art

[0002] In lithium-ion batteries, compared with traditional graphite negative electrode materials, silicon has an extremely high mass specific capacity. Compared with metallic lithium, the stacking density of silicon in alloy materials is similar to that of lithium. Therefore, silicon has both high mass specific capacity and high volume specific capacity. Compared with nano-silicon particles, silicon nanowires do not have obvious lateral volume effects during the process of lithium insertion and extraction, and the nano-silicon particles will not be crushed. Therefore, silicon nanowires have better cycle stability. Choosing silicon nanowires as negative electrode materials achieves the advantages of high mass specific capacity, high volume specific capacity and cycle stability.

[0003] The preparation methods of silicon nanowires can be divided into two types according to the growth mode: "top-down" and "bottom-up". "Bottom-up" is a mode of continuous deposition and growth of nanostructures from the atomic level through self-assembly, mainly including chemical vapor deposition, molecular beam epitaxy, laser ablation, oxide-assisted method and solution method, etc. "Top-down" is a growth mode in which the template is first etched and pre-treated to etch the sample into a nanostructure of the desired size, mainly including electron beam lithography, nanoimprint lithography and metal-assisted chemical etching technology.

[0004] CN106207144A discloses a silicon nanowire and a preparation method thereof and use thereof for preparing a carbon-coated silicon nanowire negative electrode material. A mixed powder of silicon dioxide and sodium chloride is pressed into a cathode sheet, the cathode sheet is sintered at a low temperature, and then the obtained cathode sheet is fixed on an iron-chromium-aluminum wire as a cathode, high-purity graphite is used as an anode, and electrolysis is performed in a molten salt system of CaCl2 in an atmosphere of high-purity argon to obtain the silicon nanowire.

[0005] CN102086024A discloses a method for preparing silicon nanowires. The method comprises depositing a first silicon dioxide layer on a single crystal silicon substrate, defining the width of the silicon nanowires by photolithography, etching the first silicon dioxide layer, etching the single crystal silicon substrate with the remaining first silicon dioxide as a mask to form silicon nanowires, depositing a second silicon dioxide layer and a silicon nitride layer; etching the silicon oxide layer so that the remaining silicon oxide layer forms the side wall of the silicon nanowires, testing the second etching of the second silicon dioxide layer until the bottom of the silicon nanowires is exposed; removing the silicon nitride side wall of the silicon nanowires; etching the silicon exposed at the bottom of the silicon nanowires so that the bottom of the silicon nanowires is hollowed out to form suspended silicon nanowires; and removing the remaining first and second silicon dioxide layers around the silicon nanowires.

[0006] However, the methods for preparing silicon nanowires disclosed in the above patents are too complicated. Therefore, how to simply prepare silicon nanowires on a large scale is an important research direction in this field. Summary of the invention

[0007] The purpose of the present invention is to provide a silicon nanowire and a preparation method and application thereof. The silicon nanowire is prepared in alloy form, one-time feeding is achieved, the ratio of reducing agent and catalyst elements can be controlled during the preparation process, and the preparation process is simple and easy to control.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] One of the purposes of the present invention is to provide a method for preparing silicon nanowires, the preparation method comprising:

[0010] The silicon source is first evaporated to obtain silicon source vapor, and the alloy AB x The second evaporation is performed to obtain alloy vapor, and the silicon source vapor and the alloy vapor are mixed and reacted to obtain the silicon nanowires.

[0011] Wherein, A is a reducing agent element, and A is selected from any one of Al, Mg or Zn or a combination of at least two thereof, wherein typical but non-limiting examples of the combination include: a combination of Al and Mg, a combination of Mg and Zn, or a combination of Al and Zn, etc.

[0012] B is a catalyst element, and B is selected from any one of Au, Ag, Cu, Co, Ni, Fe, Ti, Nb, Sn, Al or Zn, or a combination of at least two of them. Typical but non-limiting examples of the combination include: a combination of Au and Ag, a combination of Ag and Cu, a combination of Cu and Co, a combination of Co and Ni, a combination of Ni and Fe, a combination of Ti and Nb, a combination of Sn and Al, a combination of Al and Zn, etc.

[0013] 0.0001≤x≤3, preferably 0.001≤x≤2, and more preferably 0.001≤x≤1. The value of x can be 0.0001, 0.01, 0.1, 0.5, 1, 2, or 3, but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0014] In the present invention, an alloy containing a catalyst element and a reducing agent element is selected, wherein the catalyst element in the alloy plays a role in promoting the growth of silicon nanowires according to the VLS mechanism, and the reducing agent element plays a role in reducing the silicon compound in the silicon source into silicon atoms. In the present invention, the alloy is used to prepare silicon nanowires, and the alloy AB x The A element and the B element are fed at the same time, and the ratio of the reducing agent and the catalyst element can be controlled and maintained during the preparation process, and the preparation process is simple and easy to control.

[0015] As a preferred technical solution of the present invention, the silicon source includes any one of silicon tetrachloride, trichlorosilane or silicon tetrafluoride, or a combination of at least two of them, wherein typical but non-limiting examples of the combination include: a combination of silicon tetrachloride and trichlorosilane, a combination of silicon tetrachloride and silicon tetrafluoride, or a combination of trichlorosilane and silicon tetrafluoride, etc.

[0016] Preferably, the purity of the silicon source is ≥95%, wherein the purity may be 95%, 96%, 97%, 98%, 99% or 100%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] As a preferred technical solution of the present invention, the temperature of the first evaporation is 50-600°C, wherein the temperature can be 50°C, 70°C, 100°C, 200°C, 300°C, 400°C, 500°C, or 600°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0018] Preferably, the first evaporation atmosphere includes an argon atmosphere.

[0019] As a preferred technical solution of the present invention, the alloy AB x Including AlAg x 、ZnCu x 、AlTi x SnCu x or SnZn x Any one or a combination of at least two of the above, wherein a typical but non-limiting example of the combination is: AlAg x and ZnCu x Combination of ZnCu x and AlTi x Combination of AlTi x SnCu x Combination of SnCu x and SnZn x Among them, 0.0001≤x≤3, preferably 0.001≤x≤2, and more preferably 0.001≤x≤1.

[0020] As a preferred technical solution of the present invention, the temperature of the second evaporation is 600-2500°C, wherein the temperature can be 600°C, 800°C, 1000°C, 1200°C, 1400°C, 1600°C, 1800°C, 2000°C, 2200°C, 2400°C or 2500°C, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0021] Preferably, the second evaporation atmosphere includes an argon atmosphere.

[0022] As a preferred technical solution of the present invention, the mixing method includes: passing silicon source vapor into alloy vapor or passing alloy vapor into silicon source vapor.

[0023] Preferably, the introduction rate is 50 to 5000 L / min, wherein the rate may be 50 L / min, 100 L / min, 200 L / min, 400 L / min, 600 L / min, 800 L / min, 1000 L / min, 1500 L / min, 2000 L / min, 2500 L / min, 3000 L / min, 3500 L / min, 4000 L / min, 4500 L / min or 5000 L / min, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are equally applicable.

[0024] Preferably, the reaction temperature is 800-2500°C, wherein the temperature may be 800°C, 900°C, 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, 1500°C, 1600°C, 1700°C, 1800°C, 1900°C, 2000°C, 2100°C, 2200°C, 2300°C, 2400°C or 2500°C, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] As a preferred technical solution of the present invention, the reaction time is 5 min to 8 h, wherein the time can be 5 min, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h or 8 h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 30 min to 3 h.

[0026] As a preferred technical solution of the present invention, the preparation method comprises:

[0027] The silicon source with a purity of ≥95% is first evaporated at a temperature of 50-600°C to obtain silicon source vapor, and the alloy AB x A second evaporation at a temperature of 600-2500° C. is performed to obtain alloy vapor. The silicon source vapor and the alloy vapor are mixed and reacted at 800-2500° C. for 5 min-8 h to obtain the silicon nanowires, wherein A is a reducing agent element, and A is selected from any one of Al, Mg or Zn or a combination of at least two thereof.

[0028] B is a catalyst element, and B is selected from any one or a combination of at least two of Au, Ag, Cu, Co, Ni, Fe, Ti, Nb, Sn, Al or Zn, and 0.0001≤x≤3.

[0029] A second object of the present invention is to provide a silicon nanowire, characterized in that the silicon nanowire is prepared by the method for preparing the silicon nanowire as described in one of the objects.

[0030] The diameter of the silicon nanowire is <500nm, and the length is >20μm, wherein the diameter of the silicon nanowire can be 100nm, 200nm, 300nm, 400nm or 450nm, etc., and the length of the silicon nanowire can be 25μm, 50μm, 70μm, 90μm, 100μm, 150μm or 200μm, etc., but are not limited to the listed values, and other unlisted values ​​within the above numerical ranges are also applicable.

[0031] The third object of the present invention is to provide an application of the silicon nanowires as described in the second object, wherein the silicon nanowires are applied to lithium ion negative electrode plates.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The present invention uses an alloy as a raw material, and feeds element A and element B at the same time, so that the ratio of the reducing agent and the catalyst elements can be controlled during the preparation process, and the element ratio of the obtained silicon nanowires can be controlled;

[0034] (2) The purity of the raw materials in the process of preparing silicon nanowires in the present invention is not high, and the cost is controllable;

[0035] (3) The method for preparing silicon nanowires in the present invention has simple and reliable procedures and can be used for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the evaporation reaction device of the present invention.

[0037] In the figure: 1-evaporation chamber; 2-reaction chamber; 3-pipeline; 4-silicon source; 5-alloy source. DETAILED DESCRIPTION

[0038] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0039] It is worth noting that, in the specific implementation manner described in the present invention, Figure 1 The evaporation reaction device shown in the figure is completed, the evaporation device includes an evaporation chamber 1 and a reaction chamber 2, the evaporation chamber 1 and the reaction chamber 2 are connected by a pipeline 3, the silicon source 4 is first evaporated to obtain silicon source vapor, and the alloy AB xThe second evaporation is performed to obtain alloy vapor, and the silicon source vapor is introduced into the reaction chamber 2 through the pipeline 3 to react with the alloy vapor to obtain silicon nanowires. Figure 1 The direction of the arrow in the middle represents the flow direction of the silicon source vapor.

[0040] Example 1

[0041] This embodiment provides a silicon nanowire and a preparation method thereof, the preparation method comprising:

[0042] In an argon atmosphere, 97% pure silicon tetrachloride was first evaporated at a temperature of 50°C to obtain silicon source vapor, and the alloy AlAg 0.01 A second evaporation at a temperature of 2500° C. is performed to obtain alloy vapor, and silicon source vapor is introduced into the alloy vapor at a rate of 50 L / min to react at 2500° C. for 5 minutes to obtain the silicon nanowires.

[0043] Example 2

[0044] This embodiment provides a silicon nanowire and a preparation method thereof, the preparation method comprising:

[0045] In an argon atmosphere, 96% pure trichlorosilane was first evaporated at a temperature of 200°C to obtain silicon source vapor, and the alloy ZnCu 0.0001 A second evaporation at a temperature of 1000° C. is performed to obtain alloy vapor, and silicon source vapor is introduced into the alloy vapor at a rate of 100 L / min to react at 1000° C. for 1 hour to obtain the silicon nanowires.

[0046] Example 3

[0047] This embodiment provides a silicon nanowire and a preparation method thereof, the preparation method comprising:

[0048] In an argon atmosphere, 97% pure silicon tetrafluoride is first evaporated at a temperature of 600°C to obtain silicon source vapor, and in an argon atmosphere, the alloy SnCu3 is second evaporated at a temperature of 800°C to obtain alloy vapor. The silicon source vapor is introduced into the alloy vapor at a rate of 300 L / min and reacted at 800°C for 2 hours to obtain the silicon nanowires.

[0049] Example 4

[0050] In this embodiment, except that the rate at which the silicon source vapor is introduced into the alloy vapor is changed to 500 L / min, other conditions are the same as those in Embodiment 1.

[0051] Example 5

[0052] In this embodiment, except that the rate at which the silicon source vapor is introduced into the alloy vapor is changed to 5000 L / min, other conditions are the same as those in Embodiment 1.

[0053] Example 6

[0054] In this embodiment, in addition to AlAg 0.01 Replaced by AlAg 0.0001 Except for this, other conditions are the same as those in Example 1.

[0055] Example 7

[0056] In this embodiment, in addition to AlAg 0.01 Except for replacing with ZnCu2, the alloy vapor was introduced into the reaction at 900°C, and other conditions were the same as those in Example 1.

[0057] Comparative Example 1

[0058] In this comparative example, AlAg 0.01 Except for replacing the aluminum plate with a silver-plated surface, other conditions are the same as those in Example 1.

[0059] The sizes of the silicon nanowires prepared in the above Examples 1-7 and Comparative Example 1 were tested, and the testing method was as follows:

[0060] The diameter range of silicon nanowires was measured by scanning electron microscopy (SEM), and the average length of silicon nanowires was measured by image pro plus 6.0;

[0061] The test results of the silicon nanowires obtained in the above examples and comparative examples are listed in Table 1.

[0062] Table 1

[0063]

[0064]

[0065] From Table 1, we can get the following points:

[0066] (1) It can be seen from Examples 1-3 that the silicon nanowires obtained by the method for preparing silicon nanowires of the present invention have an average diameter of less than 500 nm and an average length of more than 20 μm.

[0067] (2) By comparing Example 1 with Example 6, it can be seen that the alloy AB of the present invention x The most preferred range of x is 0.001≤x≤1. Beyond the most preferred range, the distribution range of silicon nanowire diameters is relatively wide.

[0068] (3) By comparing Example 1 with Comparative Example 1, it can be seen that the alloy AlAg 0.01 Replacing the aluminum plate with a silver-plated surface does not allow for obtaining silicon nanowires with a thinner wire diameter.

[0069] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing silicon nanowires, characterized in that: The preparation method comprises: The silicon source is first evaporated to obtain silicon source vapor, and the alloy AB x Performing a second evaporation to obtain alloy vapor, wherein the silicon source vapor and the alloy vapor are mixed and reacted to obtain the silicon nanowires; Wherein, A is a reducing agent element, and A is selected from any one or a combination of at least two of Al, Mg or Zn, B is a catalyst element, and B is selected from any one or a combination of at least two of Au, Ag, Cu, Co, Ni, Fe, Ti, Nb, Sn, Al or Zn, and 0.0001≤x≤3.

2. The preparation method according to claim 1, characterized in that: Alloy AB x , 0.001≤x≤2, preferably 0.001≤x≤1; Preferably, the silicon source includes any one of silicon tetrachloride, trichlorosilane or silicon tetrafluoride, or a combination of at least two thereof; Preferably, the purity of the silicon source is ≥95%.

3. The preparation method according to claim 1 or 2, characterized in that: The temperature of the first evaporation is 50-600°C; Preferably, the first evaporation atmosphere includes an argon atmosphere.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The alloy AB x Including AlAg x 、ZnCu x 、AlTi x SnCu x or SnZn x Any one or a combination of at least two of the following, wherein 0.0001≤x≤3, preferably 0.001≤x≤2, and more preferably 0.001≤x≤1.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The temperature of the second evaporation is 600-2500°C; Preferably, the second evaporation atmosphere includes an argon atmosphere.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The mixing method includes: passing silicon source vapor into alloy vapor or passing alloy vapor into silicon source vapor; Preferably, the introduction rate is 50 to 5000 L / min; Preferably, the reaction temperature is 800-2500°C.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The reaction time is 5 min to 8 h, preferably 30 min to 3 h.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The preparation method comprises: The silicon source with a purity of ≥95% is first evaporated at a temperature of 50-600°C to obtain silicon source vapor, and the alloy AB x Performing a second evaporation at a temperature of 600 to 2500° C. to obtain alloy vapor, the silicon source vapor and the alloy vapor are mixed and reacted at 800 to 2500° C. for 5 min to 8 h to obtain the silicon nanowires; Wherein, A is a reducing agent element, and A is selected from any one or a combination of at least two of Al, Mg or Zn, B is a catalyst element, and B is selected from any one or a combination of at least two of Au, Ag, Cu, Co, Ni, Fe, Ti, Nb, Sn, Al or Zn, and 0.0001≤x≤3.

9. A silicon nanowire, characterized in that: The silicon nanowire is prepared by the method for preparing silicon nanowire according to any one of claims 1 to 8; The silicon nanowire has a diameter of less than 500 nm and a length of more than 20 μm.

10. A use of the silicon nanowire according to claim 9, characterized in that: The silicon nanowires are applied to lithium ion negative electrode plates.

Images