Method for preparing amorphous silicon nanowire material by using mixed silicon waste with metal salt and application thereof

Abstract

The application discloses a method for preparing amorphous silicon nanowire material by mixing silicon waste materials with metal salt and application thereof, and belongs to the technical field of lithium ion batteries. The amorphous silicon nanowire material is prepared by using photovoltaic silicon waste materials as raw materials, metal salt as a catalyst, and the two being mixed and attached on a carbon base, and then being in-situ grown into the amorphous silicon nanowire material on the base after being liquefied by Joule heat shock. The prepared amorphous silicon nanowire material is directly used as a negative electrode of a lithium ion battery, and has excellent first coulomb efficiency and cycle stability. The scheme of the application provides a new method for short-range and rapid, green and efficient preparation of the amorphous silicon nanowire material, provides a new idea for high-value utilization of photovoltaic silicon cutting waste materials, and is easy to realize industrialization.

Description

TECHNICAL FIELD

[0001] The application relates to a method for preparing amorphous silicon nanowire material by mixing silicon waste with metal salt and application thereof, and belongs to the technical field of lithium ion batteries. BACKGROUND

[0002] Developing renewable energy is an urgent task today, and solar energy is considered the best alternative to fossil energy. In recent years, the solar photovoltaic industry has grown rapidly as a sunrise industry, with a global annual growth rate of 35%. It is estimated that solar power will account for 25% of the total global demand by 2050, and the rapid growth of the industry is driving the growth of demand for silicon wafers. During the cutting and preparation process of silicon wafers, nearly 30%-40% of cutting silicon waste will be generated. It is extremely challenging to remelt cutting silicon waste to recover crystalline silicon, and when removing impurities generated during cutting, some secondary impurities may also be introduced. It is worth noting that the conversion of cutting silicon waste into high-value lithium ion battery silicon-based negative electrode new materials has attracted widespread attention.

[0003] However, the silicon-based negative electrode will undergo volume expansion / contraction (>300%) during lithium alloying / delithiation, which will cause the continuous reconstruction of the solid electrolyte interface film (SEI), irreversibly consume more and more lithium ions, and eventually lead to the performance of the electrode material to be extremely attenuated or even invalid. One-dimensional silicon nanowires can withstand huge stress without breaking, have a unique advantage of fast ion / electron transport rate, and are considered one of the promising structural designs. In addition, compared with crystalline silicon, amorphous silicon has isotropic strain / stress, higher resistance to structural fracture, and the reaction potential of amorphous silicon with lithium (-0.22V) is higher than that of crystalline silicon (-0.12V), which can inhibit the formation of lithium dendrites and improve the safety of the battery.

[0004] At present, there have been a large number of research works on the preparation method of amorphous silicon nanowires, such as chemical etching, thermal evaporation deposition, chemical vapor deposition (CVD) and supercritical flow-liquid-solid synthesis (SFLS) and the like. However, toxic silane or expensive catalysts and complex instruments are applied in these methods, which limits the potential of large-scale application, especially for lithium ion battery negative electrode materials.

[0005] Therefore, for a large amount of high-value cutting silicon waste generated in the photovoltaic industry, upgrading and preparation into an amorphous silicon nanowire material with practical significance and used as a lithium ion battery negative electrode is a new way to realize the resource utilization of photovoltaic silicon waste. SUMMARY

[0006] In order to solve the problems existing in the preparation process of amorphous silicon nanowires, one of the purposes of the present application is to provide a method for preparing amorphous silicon nanowire material by using metal salt mixed silicon waste, which uses photovoltaic cutting silicon waste as raw material and metal salt as catalyst, and the two are mixed and attached on the carbon substrate, and then the silicon waste is liquefied by Joule heat shock to grow in situ on the substrate to form amorphous silicon nanowire material, and the specific preparation method is as follows:

[0007] (1) Dissolve the metal salt in the solvent to obtain solution I.

[0008] (2) Add the silicon waste into the solution I obtained in step (1) and uniformly ultrasonic disperse to obtain a mixed slurry of metal salt and silicon waste.

[0009] (3) Soak the carbon substrate in the mixed slurry obtained in step (2), stir and then take out for vacuum drying to obtain the carbon substrate attached with metal salt and silicon waste.

[0010] (4) Load the carbon substrate attached with metal salt and silicon waste obtained in step (3) on the reaction table of the Joule heat shock equipment, turn on the power, and then obtain the amorphous silicon nanowire material grown on the carbon substrate after reaction.

[0011] Preferably, in step (1), the metal salt is one or more of copper salt, iron salt, zinc salt, silver salt, cobalt salt, nickel salt and manganese salt mixed in any proportion; and the mass percentage of metal salt in solution I is 0.5% to 10%.

[0012] Preferably, in step (1), the solvent is one or more of deionized water, ethanol, ethylene glycol, methanol, acetone and ethyl acetate mixed in any proportion.

[0013] Preferably, in step (2), the silicon waste is generated in the process of photovoltaic cutting silicon ingot; and the mass percentage of silicon waste in the mixed slurry is 3% to 15%.

[0014] Preferably, in step (2), the ultrasonic dispersion time is 5 min to 30 min.

[0015] Preferably, in step (3), the carbon substrate is any one of carbon cloth, carbon felt, graphite paper, carbon fiber and carbon film.

[0016] Preferably, in step (3), the stirring time is 10 min to 120 min, the vacuum drying temperature is 60 to 100℃, and the time is 6 to 24 h.

[0017] Preferably, in step (4), the reaction temperature of the Joule heat shock equipment is 1000 to 3000℃, and the reaction time is 0.5 to 5 s.

[0018] The second objective of this invention is to provide an application of the prepared amorphous silicon nanowire material in lithium-ion battery anode materials.

[0019] Beneficial effects of the present invention

[0020] (1) This invention provides a novel method for preparing amorphous silicon nanowires. By mixing silicon waste with metal salt, using the metal salt as a catalyst, and combining Joule thermal shock for transient heating, the silicon waste attached to the carbon substrate and the metal salt precursor are decomposed and fused, and further grown in situ into amorphous silicon nanowires. The diameter of silicon nanowires obtained by adding different metal salts is also different.

[0021] (2) The amorphous silicon nanowire material prepared by the present invention can be directly used as the negative electrode of lithium-ion battery. Compared with traditional crystalline silicon nanowires or crystalline silicon negative electrode materials, the prepared amorphous silicon nanowires can obtain more stable electrochemical performance.

[0022] (3) Compared with the conventional amorphous silicon nanowire growth and preparation method, the method disclosed in this invention is faster and shorter, and does not require complex processes or expensive and toxic precursors, making it highly commercially viable. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the amorphous silicon nanowires prepared by Joule thermal shock in this invention.

[0024] Figure 2 These are SEM images of the silicon waste used in Example 1.

[0025] Figure 3 This is a SEM image of the silicon waste and metal salt mixture used in Example 1, which was then adhered to carbon cloth and dried.

[0026] Figure 4 This is a SEM image of the amorphous silicon nanowire material obtained in Example 1.

[0027] Figure 5 These are TEM images of the amorphous silicon nanowire material obtained in Example 1. Figure 5 (A) and Selected Area Electron Diffraction (SAED) Images Figure 5 (B)).

[0028] Figure 6 The graph shows the performance of the amorphous silicon nanowire material obtained in Example 1 as the negative electrode of a lithium-ion battery and the corresponding coulombic efficiency for the first 100 cycles.

[0029] Figure 7 The image shows a TEM image of the crystalline silicon nanowire material obtained in Comparative Example 1. Figure 7 (A) and SAED image ( Figure 7 (B)). DETAILED DESCRIPTION

[0030] The technical solutions of the present application are further illustrated below in conjunction with the accompanying drawings and through specific embodiments. However, the following embodiments are merely simple examples of the present application and do not represent or limit the protection scope of the present application, and the protection scope of the present application is subject to the claims.

[0031] In the following examples, the experimental methods are all conventional methods unless otherwise specified; and the reagents and materials are all commercially available unless otherwise specified.

[0032] Example 1

[0033] The present embodiment provides a method for preparing amorphous silicon nanowire material by using mixed silicon waste material with metal salt and application thereof, comprising the following steps:

[0034] (1) 2.0 g of copper sulfate is weighed and dissolved in 100 mL of deionized water solution and stirred uniformly to obtain solution I.

[0035] (2) 5.0 g of cut silicon waste material is weighed and dispersed in the solution I obtained in step (1), and after ultrasonic dispersion for 20 min, further stirring for 30 min is performed to obtain a uniform mixed slurry.

[0036] (3) The carbon cloth is cut into small pieces (~1x5 cm) and placed in the mixed slurry obtained in step (2) to be fully infiltrated, and after 15 min, it is taken out and vacuum dried at 80°C for 12 h to obtain a carbon substrate attached with metal salt and silicon waste material.

[0037] (4) The carbon cloth substrate attached with metal salt and silicon waste material obtained in step (3) is loaded on the reaction table of the joule heat shock device, the temperature is controlled at 1800°C, and the reaction time is set to 1.0 s to obtain amorphous silicon nanowire material grown on the carbon substrate.

[0038] It is measured that the diameter of the amorphous silicon nanowire material prepared in the present embodiment is 10-15 nm.

[0039] The scanning electron microscope (JSM-7800) is used to test the cut silicon waste material, the silicon waste material mixed with metal salt attached on the carbon cloth, and the prepared amorphous silicon nanowire material under the above conditions. The test results are shown in Figure 2 , Figure 3 , Figure 4 As can be seen from the pictures, the morphology of the silicon waste material raw material is in the form of hundred-nanometer fragments, which can be uniformly dispersed and attached on the carbon cloth with the metal salt. After the joule heat shock reaction, dense silicon nanowire material is obtained.

[0040] Transmission electron microscope (JEM-2100F) was used to test the crystal structure of the silicon nanowire material prepared under the above conditions. The test results are shown in Figure 5 As can be seen from the picture, the prepared nanowire material is amorphous structure, and no obvious diffraction stripes appear.

[0041] The amorphous silicon nanowire material prepared on the carbon cloth substrate in Example 1 was directly used as the negative electrode of the lithium ion battery, with a lithium metal sheet as the counter electrode, Celgard2325 as the separator, 1 mol / L LiPF6 (solvent: 1:1 volume ratio of dimethyl carbonate and ethylene carbonate mixture) as the electrolyte, and CR2032 type button cell shell was used to assemble a button cell in an argon glove box. Charge-discharge test, test current is 0.2-0.8A / g, voltage charge-discharge interval 0.01~3.0V, charge-discharge cycle performance as Figure 6 As can be seen from the picture, the first coulombic efficiency is greater than 90%, and the reversible capacity is stable at 2400mAh / g after 100 cycles, showing excellent electrochemical cycle performance.

[0042] Example 2

[0043] The present embodiment provides a method for preparing amorphous silicon nanowire material by mixing silicon waste with metal salt and its application, comprising the following steps:

[0044] (1) Take 0.5g of silver nitrate and dissolve it in 100mL of ethanol solution and stir uniformly to obtain solution I.

[0045] (2) Take 5.0g of cut silicon waste and disperse it in the solution I obtained in step (1), ultrasonic dispersion for 20min, and further stirring for 30min to obtain a uniform mixed slurry.

[0046] (3) Cut the carbon cloth into small pieces (~1x5cm) and put it into the mixed slurry obtained in step (2) to fully soak, take it out after 15min, and vacuum dry at 80℃ for 12h to obtain a carbon substrate attached with metal salt and silicon waste.

[0047] (4) Load the carbon cloth substrate attached with metal salt and silicon waste obtained in step (3) on the reaction platform of the joule heat shock device, control the temperature at 1900℃, and set the reaction time to 1.0s to obtain amorphous silicon nanowire material grown on the carbon substrate.

[0048] The diameter of the amorphous silicon nanowire material prepared in this embodiment is 5-10nm.

[0049] Other properties are similar to the material prepared in Example 1.

[0050] Example 3

[0051] The embodiment provides a method for preparing amorphous silicon nanowire material by mixing silicon waste with metal salt and application thereof, and comprises the following steps.

[0052] (1) 10 g of ferric nitrate is weighed and dissolved in 100 mL of a mixed solution of ethylene glycol and methanol to obtain solution I.

[0053] (2) 5.0 g of cut silicon waste is weighed and dispersed in the solution I obtained in step (1), and after ultrasonic dispersion for 20 min, further stirring for 30 min is carried out to obtain a uniform mixed slurry.

[0054] (3) The carbon cloth is cut into small pieces (about 1*5 cm) and is put into the mixed slurry obtained in step (2) to be fully infiltrated, and is taken out after 15 min; vacuum drying is carried out at 80 DEG C for 12 h to obtain a carbon substrate attached with metal salt and silicon waste.

[0055] (4) The carbon cloth substrate attached with metal salt and silicon waste obtained in step (3) is loaded on a reaction table of a joule heat shock device, the temperature is controlled at 1700 DEG C, and the reaction time is set to 1.0 s to obtain amorphous silicon nanowire material grown on the carbon substrate.

[0056] It is measured that the diameter of the amorphous silicon nanowire material prepared in the embodiment is 1-5 nm.

[0057] Other performances are similar to those of the material prepared in example 1.

[0058] Example 4

[0059] The embodiment provides a method for preparing amorphous silicon nanowire material by mixing silicon waste with metal salt and application thereof, and comprises the following steps:

[0060] (1) 3.0 g of nickel nitrate is weighed and dissolved in 100 mL of an acetone solution to obtain solution I.

[0061] (2) 3.0 g of cut silicon waste is weighed and dispersed in the solution I obtained in step (1), and after ultrasonic dispersion for 20 min, further stirring for 30 min is carried out to obtain a uniform mixed slurry.

[0062] (3) The carbon cloth is cut into small pieces (about 1*5 cm) and is put into the mixed slurry obtained in step (2) to be fully infiltrated, and is taken out after 15 min; vacuum drying is carried out at 80 DEG C for 12 h;

[0063] (4) The carbon cloth substrate attached with metal salt and silicon waste obtained in step (3) is loaded on a reaction table of a joule heat shock device, the temperature is controlled at 1800 DEG C, and the reaction time is set to 1.5 s to obtain amorphous silicon nanowire material grown on the carbon substrate.

[0064] The diameter of the amorphous silicon nanowire material prepared in this embodiment is 15-20 nm.

[0065] Other properties are similar to those of the material prepared in Example 1.

[0066] Example 5

[0067] This embodiment provides a method and application for preparing amorphous silicon nanowire material by mixing silicon waste with metal salt, comprising the following steps:

[0068] (1) 3.0 g of cobalt nitrate was dissolved in 100 mL of ethyl acetate solution and stirred uniformly to obtain solution I.

[0069] (2) 15.0 g of cut silicon waste was dispersed in the solution I obtained in step (1), and after ultrasonic dispersion for 20 min, further stirring for 30 min, a uniform mixed slurry was obtained.

[0070] (3) The carbon cloth was cut into small pieces (~ 1 x 5 cm) and placed in the mixed slurry obtained in step (2) for sufficient soaking, and after 15 min, it was taken out and vacuum dried at 80°C for 12 h to obtain a carbon substrate attached with metal salt and silicon waste.

[0071] (4) The carbon cloth substrate attached with metal salt and silicon waste obtained in step (3) was loaded on the reaction platform of the joule heat shock device, and the temperature was controlled at 2300°C, and the reaction time was set to 2.0 s.

[0072] The diameter of the amorphous silicon nanowire material prepared in this embodiment is 25-30 nm.

[0073] Example 6

[0074] This embodiment provides a method and application for preparing amorphous silicon nanowire material by mixing silicon waste with metal salt, comprising the following steps:

[0075] (1) 3.0 g of cobalt nitrate was dissolved in 100 mL of ethyl acetate solution and stirred uniformly to obtain solution I.

[0076] (2) 15.0 g of cut silicon waste was dispersed in the solution I obtained in step (1), and after ultrasonic dispersion for 20 min, further stirring for 30 min, a uniform mixed slurry was obtained.

[0077] (3) The carbon cloth was cut into small pieces (~ 1 x 5 cm) and placed in the mixed slurry obtained in step (2) for sufficient soaking, and after 15 min, it was taken out and vacuum dried at 80°C for 12 h to obtain a carbon substrate attached with metal salt and silicon waste.

[0078] (4) The carbon cloth substrate with attached metal salt and silicon waste material obtained in step (3) is loaded on the reaction platform of the Joule heat shock device, the temperature is controlled at 2500°C, and the reaction time is set to 3.0 s to obtain amorphous silicon nanowire material grown on the carbon substrate.

[0079] The diameter of the amorphous silicon nanowire material prepared in this embodiment is measured to be 30-50 nm.

[0080] Other properties are similar to those of the material prepared in Example 1.

[0081] Comparative Example 1

[0082] As a comparison, the comparative example differs from Example 1 in that no metal salt is used, and the preparation method is the same as that of Example 1, and the specific steps are as follows:

[0083] (1) 5.0 g of cut silicon waste material is dissolved in 100 mL of deionized water solution and stirred uniformly, and after ultrasonic dispersion for 20 min, further stirring for 30 min is performed to obtain a uniform slurry.

[0084] (2) The carbon cloth is cut into small pieces (~1x5 cm) and immersed in the slurry obtained in step (1) for sufficient soaking, and after 15 min, it is taken out; vacuum drying at 80°C for 12 h obtains a carbon substrate with attached silicon waste material.

[0085] (3) The carbon cloth substrate with attached silicon waste material in step (2) is loaded on the reaction platform of the Joule heat shock device, and the temperature is controlled at 1800°C, and the reaction time is set to 1.0 s.

[0086] The diameter of the crystalline silicon nanowire material prepared in this embodiment is measured to be 5-15 nm.

[0087] A transmission electron microscope (JEM-2100F) is used to test the crystal structure of the crystalline silicon nanowire material prepared under the above conditions. The test results are shown in Figure 7 As can be seen, the prepared nanowire is a crystalline silicon nanowire. Further electrochemical performance test shows that the first coulombic efficiency is about 85%, and the reversible capacity is less than 1500 mAh / g after 100 cycles at a current of 0.8 A / g, and the capacity stability is much lower than that of the amorphous silicon nanowire prepared in Example 1.

[0088] Comparative Example 2

[0089] The comparative example provides a method and application for preparing crystalline silicon nanowire material using silicon waste material, including the following steps:

[0090] (1) 5.0 g of cut silicon waste material is dissolved in 100 mL of deionized water solution and stirred uniformly, and after ultrasonic dispersion for 20 min, further stirring for 30 min is performed to obtain a uniform slurry.

[0091] (2) Cut the carbon cloth into small pieces (~1x5cm) and immerse them into the slurry obtained in step (1) for 15 min. Then take out the carbon cloth and dry it at 80°C under vacuum for 12h to obtain the carbon substrate with silicon scraps attached.

[0092] (3) Load the carbon cloth substrate with silicon scraps obtained in step (2) on the reaction platform of the joule heat shock device and control the temperature at 1900°C. Set the reaction time to 2.0s.

[0093] The diameter of the crystalline silicon nanowire material prepared in this example is measured to be 30-40nm.

[0094] The material prepared in this comparative example is further tested for electrochemical performance. The first coulombic efficiency is about 78%, and the reversible capacity is less than 1350mAh / g after 100 cycles at a current of 0.8A / g, which is much lower than the amorphous silicon nanowire prepared in Example 1.

[0095] The above is a further detailed description of the present application in combination with specific embodiments, and the specific implementation of the present application should not be limited to these descriptions. For those of ordinary skill in the art to which the present application belongs, without departing from the concept of the present application, a number of simple deductions or substitutions can be made.

Claims

1. A method for preparing amorphous silicon nanowire material using a mixture of silicon waste with metal salt, characterized by: The method comprises the following steps: (1) dissolving a metal salt in a solvent to obtain solution I; (2) adding silicon waste to the solution I obtained in step (1), ultrasonic dispersion, and then stirring to obtain a mixed slurry of the metal salt and the silicon waste; (3) fully immersing a carbon substrate in the mixed slurry obtained in step (2), taking it out, and vacuum drying to obtain a carbon substrate attached with the metal salt and the silicon waste; (4) loading the carbon substrate attached with the metal salt and the silicon waste obtained in step (3) on a reaction table of a joule heat shock device, turning on the power, and obtaining amorphous silicon nanowire material grown on the carbon substrate after reaction; In step (1), the metal salt is one of copper sulfate, silver nitrate, iron nitrate, nickel nitrate, cobalt nitrate or manganese nitrate; and the mass percentage of the metal salt in solution I is 0.5% to 10%. In step (4), the reaction temperature of the joule heat shock device is 1000 to 3000℃, and the reaction time is 0.5 to 5s.

2. The method for preparing amorphous silicon nanowire material by mixing silicon waste with metal salt according to claim 1, characterized in that: In step (1), the solvent is one or more of deionized water, ethanol, ethylene glycol, methanol, acetone and ethyl acetate mixed in any proportion.

3. The method for preparing amorphous silicon nanowire material by mixing silicon waste with metal salt according to claim 1, wherein: In step (2), the silicon waste is generated in the process of cutting a silicon ingot for photovoltaic; and the mass percentage of the silicon waste in the mixed slurry is 3% to 15%.

4. The method for preparing amorphous silicon nanowire material by mixing silicon waste with metal salt according to claim 1, wherein: In step (2), the ultrasonic dispersion time is 5min to 30min, and the stirring time is 10min to 120min.

5. The method for preparing amorphous silicon nanowire material using metal salt mixed silicon waste material according to claim 1, wherein: In step (3), the carbon substrate is any one of carbon cloth, carbon felt, graphite paper, carbon fiber and carbon film.

6. The method for preparing amorphous silicon nanowire material using metal salt mixed silicon waste according to claim 1, wherein: In step (3), the temperature of vacuum drying is 60℃ to 100℃, and the time is 6h to 24h.

7. Application of the amorphous silicon nanowire material prepared by the method of any one of claims 1 to 6 in a lithium ion battery negative electrode material.

Images