Silicon nanowire and its preparation method and application

Abstract

The present invention provides a silicon nanowire, a preparation method thereof, and an application thereof. The preparation method of the silicon nanowire comprises the following steps: (1) depositing a tin catalytic film on a stainless steel current collector by a magnetron sputtering method; (2) transferring the stainless steel current collector obtained in step (1) to a reaction chamber, and reducing the tin catalytic film by hydrogen plasma; (3) performing core growth on the stainless steel current collector obtained in step (2) by a first plasma-assisted chemical vapor deposition technique; and (4) performing shell growth on the stainless steel current collector obtained in step (3) by a second plasma-assisted chemical vapor deposition technique to obtain the silicon nanowire. The present invention prepares a three-dimensional "breathable" silicon nanowire by plasma-enhanced chemical vapor deposition technology, and utilizes its "breathable" structure to effectively alleviate the volume expansion of the silicon negative electrode during the charge and discharge process, thereby achieving higher cycle stability and longer service life.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state batteries, and in particular to a silicon nanowire and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries (LIBs) have become one of the most promising energy storage technologies. However, the increasingly stringent requirements for battery capacity and charging speed in modern electric vehicles and high-performance portable electronic devices have gradually exposed the shortcomings of traditional liquid-state lithium-ion batteries in terms of energy density, cycle life, and safety. Therefore, the development of all-solid-state batteries (SSBs) with higher energy density, longer cycle life, and improved safety is highly desirable.

[0003] In all-solid-state batteries, the selection and preparation of negative electrode materials play a key role in battery performance, especially silicon negative electrode materials. Silicon has a high theoretical specific capacity (about 4200mAh g -1 ), far exceeding traditional graphite (about 372mAh g -1 ), is widely considered to be one of the ideal negative electrode materials to replace graphite. However, silicon undergoes a dramatic volume expansion during the charge and discharge process, which can reach 300%. This change often leads to structural damage of the electrode material, causing problems such as rapid capacity decay and poor cycle stability. To solve this problem, the Lee research team used reactive ion technology to design a three-dimensional nano-silicon rod negative electrode, and applied it to an all-solid-state battery with 77.5Li2S-22.5P2S5 as a solid electrolyte. This structure significantly alleviated the volume expansion problem, allowing the battery to maintain stable capacity decay over 20 cycles. The Kaskel team prepared a columnar silicon negative electrode by physical vapor deposition (PVD) technology, showing a capacity of 3.5mAh / cm 2 The high areal capacity of the product is 82% after 100 cycles, and it supports a high charge flow rate of 1.5 mA cm at room temperature. -2 Talin et al. combined chemical vapor deposition (CVD) and magnetron sputtering techniques to successfully fabricate single-crystalline silicon nanowires (Si NWs) and their multilayer core-shell structures. They also constructed an all-solid-state lithium-ion battery with a diameter of 0.5-1.2 μm and a length of 7 μm, achieving a theoretical maximum discharge capacity of 0.17 pAh.

[0004] Although these technologies have made significant progress under laboratory conditions, they still have preparation limitations. For example, reactive ion deposition (RID) faces challenges in processing precision and material damage control, while physical vapor deposition (PVD) deposition efficiency and interface stability need to be improved. While CVD is suitable for the preparation of complex thin films, its high temperature and high cost limit its practical application prospects. Therefore, improving the volume expansion and interface stability of silicon anodes remains a major challenge for all-solid-state batteries, and optimization of the preparation process is also a concurrent task. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the present invention provides a silicon nanowire, a preparation method and application thereof, and prepares a three-dimensional "breathable" silicon nanowire through plasma enhanced chemical vapor deposition technology. Its "breathable" structure effectively alleviates the volume expansion of the silicon negative electrode during the charging and discharging process, achieves higher cycle stability and longer service life, and solves the problems raised in the above background technology.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0007] According to a first aspect of the present invention, there is provided a method for preparing silicon nanowires, comprising the following steps:

[0008] (1) Deposition of tin catalytic film on stainless steel current collector by magnetron sputtering;

[0009] (2) transferring the stainless steel current collector obtained in step (1) into a reaction chamber, and reducing the tin catalytic film using hydrogen plasma;

[0010] (3) performing nucleation growth on the stainless steel current collector obtained in step (2) using a first plasma-assisted chemical vapor deposition technique;

[0011] (4) A second plasma-assisted chemical vapor deposition technique is used to grow a shell on the stainless steel current collector obtained in step (3) to obtain the silicon nanowires.

[0012] Preferably, in step (3), the conditions for the nucleus growth are: the temperature of the stainless steel current collector substrate is 232-600°C, the radio frequency power density is 0.05-1.23 W / cm 2 , the chamber pressure is 100~1000 Pa, the first plasma includes H2, SiH4 and PH3, the flow rate of H2 is 100~500 sccm, the flow rate of SiH4 is 0.1~10 sccm, the flow rate of PH3 is 0.1~10sccm, and the nuclear growth time is 5~120 min.

[0013] Further preferably, in step (3), the conditions for the nucleus growth are: the temperature of the stainless steel collector substrate is 450°C, the radio frequency power density is 1W / cm 2 The chamber pressure is 500 Pa, the first plasma includes H2, SiH4 and PH3, the flow rate of H2 is 200 sccm, the flow rate of SiH4 is 2.9 sccm, the flow rate of PH3 is 10 sccm, and the nuclear growth time is 30 min.

[0014] Preferably, in step (4), the shell growth conditions are: the stainless steel collector substrate temperature is 50-600 °C, the radio frequency power density is 0.01-1.23 W / cm 2 , the chamber pressure is 50 ~1000 Pa, the second plasma includes H2, SiH4 and PH3, the flow rate of H2 is 100 ~500 sccm, the flow rate of SiH4 is 0.1 ~20 sccm, the flow rate of PH3 is 0.1 ~10 sccm, and the shell growth time is 5 ~180 min.

[0015] Further preferably, in step (4), the shell growth conditions are: the stainless steel current collector substrate temperature is 450°C, the radio frequency power density is 1W / cm 2 , the chamber pressure is 500 Pa, the second plasma includes H2, SiH4 and PH3, the flow rate of H2 is 200 sccm, the flow rate of SiH4 is 5 sccm, the flow rate of PH3 is 10 sccm, and the shell growth time is 60 min.

[0016] Preferably, in step (1), the conditions for depositing the tin catalytic film on the stainless steel current collector by magnetron sputtering are as follows: the reaction chamber is evacuated to a vacuum value of 1×10 -3 ~1×10 -5 Pa, fill with argon at a flow rate of 50 ~ 200 sccm, adjust the gas pressure of the reaction chamber to 3 ~ 5 Pa, and the RF power to 5 ~ 50 W. After successful ignition, adjust the gas pressure of the reaction chamber to 1 ~ 2 Pa, and continue coating for 1 ~ 30 min until the film thickness is 10 ~ 100 nm. Among them, the target material used for magnetron sputtering is tin target.

[0017] Further preferably, in step (1), the conditions for depositing the tin catalytic film on the stainless steel current collector by magnetron sputtering are as follows: the reaction chamber is evacuated to a vacuum value of 2×10 -4 Pa, argon is filled in at a flow rate of 100 sccm, the gas pressure of the reaction chamber is adjusted to 3Pa, the RF power is conditioned at 20W, and after successful ignition, the gas pressure of the reaction chamber is adjusted to 1Pa, and the coating is continued for 12 minutes until the film thickness is 60nm. Among them, the target material used for magnetron sputtering is tin target.

[0018] Preferably, in step (2), the reduction treatment conditions are: the temperature of the stainless steel current collector substrate is 232-600°C, the radio frequency power density is 0.05-1.23 W / cm 2 , the chamber pressure is 100~1000 Pa, the flow rate of hydrogen plasma is 100~500 sccm, and the reduction treatment time is 2~30 min.

[0019] Further preferably, in step (2), the reduction treatment conditions are: the temperature of the stainless steel current collector substrate is 450°C, the radio frequency power density is 1 W / cm 2 , the chamber pressure is 130 Pa, the flow rate of hydrogen plasma is 100 sccm, and the reduction treatment time is 10 min.

[0020] According to a second aspect of the present invention, a silicon nanowire obtained according to the above-mentioned preparation method is provided, wherein the silicon nanowire is a columnar three-dimensional cross-linked structure perpendicular to the surface of the stainless steel current collector, comprising a core layer and a shell layer, wherein the core layer is crystalline silicon with a lattice spacing of 0.31 nm and a crystal plane index of (111), and the shell layer is amorphous silicon.

[0021] According to a third aspect of the present invention, there is provided a use of silicon nanowires as a negative electrode material in a solid-state battery.

[0022] The present invention provides a silicon nanowire and its preparation method and application. It has the following beneficial effects:

[0023] (1) This proposal provides a method for preparing silicon nanowires, which uses plasma-enhanced chemical vapor deposition technology to prepare a three-dimensional "breathable" columnar silicon nanowire structure, which can effectively alleviate the volume expansion problem of the silicon negative electrode during the charging and discharging process. The plasma-enhanced chemical vapor deposition technology can efficiently and accurately control the growth of silicon nanowires, and can be carried out at a lower temperature. It also has excellent scalability and can achieve large-scale production.

[0024] (2) This solution provides a silicon nanowire with a three-dimensional "breathable" columnar crystalline silicon nanowire structure, a large specific surface area and efficient ion channels. When used as a negative electrode material in all-solid-state batteries, it can effectively buffer the volume change of the silicon negative electrode during the charge and discharge process, thereby improving the cycle stability and service life of the all-solid-state battery. In addition, it also has excellent interface stability with the solid electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Scanning electron microscope images of silicon nanowires prepared in Example 1 of the present invention, wherein (a) is a surface morphology image of the silicon nanowires, and (b) is a cross-sectional image of the silicon nanowires;

[0026] Figure 2 Transmission electron micrographs of silicon nanowires prepared in Example 1 of the present invention, wherein (a) is a transmission electron micrograph of the shell layer, (b) is a scanning electron micrograph of the core layer, and (c) is the lattice structure of the core layer;

[0027] Figure 3 This is the first cycle charge-discharge curve of the silicon nanowires prepared in Example 1 of the present invention when assembled into a half-cell;

[0028] Figure 4 This is a graph showing the long cycle performance of the silicon nanowires prepared in Example 1 of the present invention when assembled into a half-cell;

[0029] Figure 5 This is the first cycle charge-discharge curve of the silicon nanowires prepared in Example 1 of the present invention when assembled into an all-solid-state battery;

[0030] Figure 6 This is a diagram showing the long-cycle performance of the silicon nanowires prepared in Example 1 of the present invention when assembled into an all-solid-state battery. DETAILED DESCRIPTION

[0031] In order to better illustrate the content of the present invention, it is described below in conjunction with specific embodiments.

[0032] Example 1

[0033] A process for preparing silicon nanowires comprises the following steps:

[0034] (1) Place the stainless steel current collector in an ultra-high vacuum multifunctional magnetron sputtering system and evacuate the reaction chamber to 2×10 -4 Pa, then introduce argon with a flow rate of 100 sccm, adjust the reaction chamber pressure to 3 Pa, and then adjust the RF power to 20 W. After successful ignition, adjust the reaction chamber pressure to 1 Pa, continue coating for 12 minutes, and control the coating thickness to 60 nm. Among them, the target material used for magnetron sputtering is tin target;

[0035] (2) The stainless steel current collector obtained in step (1) was transferred to the reaction chamber of the plasma enhanced chemical vapor deposition system, and the temperature of the stainless steel current collector substrate was regulated to 450 ° C and the radio frequency power density was 1 W / cm 2 The pressure in the reaction chamber was 500 Pa, and H2 plasma with a flow rate of 100 sccm was introduced for reduction treatment for 10 minutes;

[0036] (3) Maintain the temperature of the stainless steel current collector substrate at 450°C and the RF power density at 1 W / cm 2, the temperature of the reaction chamber was adjusted to 500 Pa, and a first plasma with a flow rate of 200 sccm of H2, 2.9 sccm of SiH4 and 10 sccm of PH3 was introduced to carry out nucleus growth for 30 minutes;

[0037] (4) Maintain the temperature of the stainless steel current collector substrate at 450°C, the pressure of the reaction chamber at 500 Pa, and the RF power density at 1 W / cm 2 A second plasma with a flow rate of 200 sccm of H2, 5 sccm of SiH4 and 10 sccm of PH3 was introduced to perform shell growth for 60 minutes to obtain columnar silicon nanowires.

[0038] The morphology of the silicon nanowires prepared in this example was characterized by scanning electron microscopy. Figure 1 As shown, through Figure 1 As shown in Figure (a), the silicon nanowires prepared in this embodiment have a columnar three-dimensional cross-linked structure with a uniform size distribution; Figure 1 As shown in Figure (b), the silicon nanowires grow perpendicular to the stainless steel current collector. This vertical arrangement helps to enhance the overall mechanical stability and conductivity.

[0039] The internal structure of the silicon nanowires prepared in this embodiment was characterized by transmission electron microscopy. Figure 2 As shown, according to Figure 2 From the electron diffraction patterns of (a) and (b), we can see that the silicon nanowire consists of a shell layer and a core layer, where the shell layer is amorphous silicon and the core layer is crystalline silicon. Figure 2 The lattice spacing analysis of Figure (c) shows that the lattice spacing of the core layer is 0.31 nm, and the crystal plane index is (111), corresponding to the silicon (111) crystal plane.

[0040] The silicon nanowires prepared in this example were used as negative electrode materials in a half-cell to test their electrochemical properties. Specifically, 150 mg of sulfide electrolyte (Li6PS5Cl) was transferred to a polyetherketone mold with a diameter of 10 mm and pressed under 3.5 tons of pressure. 1 mg of the silicon nanowires prepared in this example was then placed on one side of the sulfide electrolyte particles as the anode. A 99.99% indium foil with a diameter of 10 mm and a thickness of 0.1 mm and a lithium sheet were then placed on the other side of the sulfide electrolyte as the counter electrode to form a multilayer sheet. Finally, the multilayer sheet was pressed between two stainless steel rods to form a half-cell.

[0041] The half-cell was subjected to constant current charge and discharge tests using a battery tester, with the voltage controlled between 0.01V and 2V. The electrochemical impedance spectroscopy was performed on an electrochemical workstation, with a recording frequency range of 10MHz to 10mHz and an amplitude of 10mV. The applied pressure and test temperature of the half-cell were fixed at 62.8MPa and 25°C, respectively. Five cycles of 0.05C pre-cycling were performed before the 0.2C cycle test. Figure 3 It can be seen that the first-round Coulomb efficiency is 91.5%, and the first-round discharge capacity reaches 2852.8 mAh g -1 The appearance of the platform during the charge and discharge process indicates that the insertion and extraction of lithium ions have good reversibility, and exhibits typical chemical behavior during the first charge and discharge process, indicating that the silicon nanowires prepared in this embodiment have a high specific capacity.

[0042] according to Figure 4 It can be seen that after 400 cycles, the capacity retention rate is still as high as over 90%, and the Coulombic efficiency is always close to 100%. After 1000 cycles, the discharge specific capacity is still maintained at 1527.6mAh g-1, the capacity retention rate exceeds 60%, and the Coulombic efficiency is always close to 100%. It can be seen that the columnar three-dimensional cross-linked structure can effectively alleviate the problem of volume expansion during charge and discharge, and has excellent interface stability between the electrode and the solid electrolyte.

[0043] The silicon nanowires prepared in this example are used as negative electrode materials in all-solid-state batteries. First, LiNi 0.83 Co 0.085 Mn 0.085 O2 and Li3InCl6 are placed in a mortar and ground evenly to make a mixed positive electrode. Then 55 mg of Li6PS5Cl and Li6PS5Cl are taken respectively, and the Li6PS5Cl is pressed into a thin sheet with slight pressure. On this basis, the Li3InCl6 is pressed into a thin sheet with the same pressure. 15.7 mg of the positive electrode is placed on top of the electrolyte. The three are pressed into thin sheets under a pressure of 3.5 tons. Finally, 1 mg of silicon nanowire counter electrode is placed on the thin sheet to form an all-solid-state battery structure with the positive electrode. Finally, it is placed between two stainless steel rods and pressed tightly to form an all-solid-state battery.

[0044] The constant current charge and discharge test was carried out by a battery tester, with the voltage controlled at 2.0 V to 4.5 V; the electrochemical impedance spectroscopy (EIS) was carried out on an electrochemical workstation, with the recording frequency range of 10 MHz to 10 mHz and the amplitude of 10 mV; the applied pressure and test temperature of the all-solid-state battery were fixed at 62.8 MPa and 25 °C, respectively, and the all-solid-state battery was pre-cycled at 0.05 C for 5 cycles before the 0.5 C cycle test. Figure 5It can be seen that the silicon nanowires prepared in this embodiment are used as negative electrode materials in all-solid-state batteries, with an initial coulombic efficiency of 88.7% and a first-cycle discharge capacity of 169.4 mAh g -1 , indicating that the insertion and extraction of lithium ions have good reversibility, further verifying that the silicon nanowires prepared in this example have excellent application potential as negative electrode materials in all-solid-state batteries.

[0045] according to Figure 6 It can be seen that after 200 cycles, the discharge capacity of the battery is 59.1 mAh g -1 The capacity retention rate reached 75%, and the Coulombic efficiency was always close to 100%, indicating that the columnar three-dimensional cross-linked silicon nanowires prepared in this embodiment effectively alleviated the volume expansion during the charge and discharge process. At the same time, the negative electrode material and the electrolyte had excellent cross-sectional stability, thereby significantly improving the cycle stability and energy density of the all-solid-state battery.

[0046] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing silicon nanowires, characterized in that: The following steps are involved: (1) Deposition of tin catalytic film on stainless steel current collector by magnetron sputtering; (2) transferring the stainless steel current collector obtained in step (1) into a reaction chamber, and reducing the tin catalytic film using hydrogen plasma; (3) performing nucleation growth on the stainless steel current collector obtained in step (2) using a first plasma-assisted chemical vapor deposition technique; (4) growing a shell on the stainless steel current collector obtained in step (3) using a second plasma-assisted chemical vapor deposition technique to obtain the silicon nanowires; Wherein, in step (3), the conditions for the nucleus growth are: the temperature of the stainless steel collector substrate is 450~600℃, the RF power density is 1~1.23W / cm 2 , the chamber pressure is 500~1000Pa, the first plasma includes H2, SiH4 and PH3, the flow rate of H2 is 200~500sccm, the flow rate of SiH4 is 2.9~10sccm, the flow rate of PH3 is 10sccm, and the nuclear growth time is 30~120min; In step (4), the shell growth conditions are: the temperature of the stainless steel collector substrate is 450-600°C, the radio frequency power density is 1-1.23W / cm 2 The chamber pressure is 500~1000Pa, the second plasma includes H2, SiH4 and PH3, the flow rate of H2 is 200~500sccm, the flow rate of SiH4 is 5~20sccm, the flow rate of PH3 is 10sccm, and the shell growth time is 60~180min.

2. The method for preparing silicon nanowires according to claim 1, wherein: In step (1), the conditions for depositing the tin catalytic film on the stainless steel current collector by magnetron sputtering are as follows: the reaction chamber is evacuated to a vacuum value of 1×10 -3 ~1×10 -5 Pa, fill with argon at a flow rate of 50 ~ 200 sccm, adjust the gas pressure of the reaction chamber to 3 ~ 5 Pa, and the RF power to 5 ~ 50W. After successful ignition, adjust the gas pressure of the reaction chamber to 1 ~ 2Pa, and continue coating for 1 ~ 30 minutes until the film thickness is 10 ~ 100 nm. Among them, the target material used for magnetron sputtering is tin target.

3. The method for preparing silicon nanowires according to claim 1, wherein: In step (2), the reduction treatment conditions are: the temperature of the stainless steel current collector substrate is 232~600℃, the radio frequency power density is 0.05~1.23 W / cm 2 , the chamber pressure is 100~1000 Pa, the flow rate of hydrogen plasma is 100~500 sccm, and the reduction treatment time is 2~30min.

4. A silicon nanowire obtained by the preparation method according to any one of claims 1 to 3, characterized in that: The silicon nanowire is a columnar three-dimensional cross-linked structure perpendicular to the surface of the stainless steel current collector, including a core layer and a shell layer. The core layer is crystalline silicon with a lattice spacing of 0.31 nm and a crystal plane index of (111), and the shell layer is amorphous silicon.

5. Use of the silicon nanowire according to claim 4 as a negative electrode material in an all-solid-state battery.

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