Silicon powder for anode material of secondary battery, method of preparing same, and anode material for secondary battery

Abstract

Provided are a silicon powder for an anode material of a secondary battery, a method of preparing same, and an anode material for a secondary battery, comprising same, the silicon powder being obtained from waste slurry generated during a semiconductor process and having a crystal size of 24-50 nm, which is obtained by means of mathematical relation 1 with respect to the maximum intensity peak at 2θ of 23° to 33° in X-ray diffraction (XRD) analysis. [Mathematical relation 1] Crystal size (nm) = {shape factor × X-ray wavelength} / {the full width at half maximum (FWHM) of the maximum intensity peak × cosθ}

Description

Silicon powder for secondary battery anode materials, manufacturing method, and secondary battery anode materials

[0001] The present disclosure relates to a silicon powder for a secondary battery negative electrode material, a method for producing the same, and a secondary battery negative electrode material including the same.

[0002] The amount of waste slurry generated globally by the semiconductor industry is enormous, most of which contains silicon (Si). Environmentally sound processing and recycling of this waste slurry presents a significant challenge. Currently, there is a pressing need for a method to recycle this waste slurry and convert it into high-value materials.

[0003] Accordingly, technologies for recovering silicon from waste slurry are being studied, and in particular, research is underway to obtain high-quality silicon for use as a high-performance secondary battery anode material.

[0004] One embodiment provides a silicon powder for use as a secondary battery negative electrode material, which is obtained from waste slurry generated in a semiconductor process and has excellent capacity characteristics and lifespan characteristics.

[0005] Another embodiment provides a method for producing silicon powder for use as a negative electrode material for a secondary battery.

[0006] Another embodiment provides a negative electrode material for a secondary battery including the silicon powder.

[0007] One embodiment provides a silicon powder for a secondary battery negative electrode material, which is obtained from waste slurry generated in a semiconductor process and has a crystal size of 24 nm to 50 nm obtained by the following mathematical formula 1 for a maximum intensity peak at 2θ of 23° to 33° in X-ray diffraction analysis (XRD).

[0008] [Mathematical Formula 1]

[0009] Crystal size (nm) = {shape factor x X-ray wavelength} / {full width at half maximum (FWHM) of maximum intensity peak x cosθ}

[0010] The above silicon powder may have a crystal size of 6 nm to 25 nm obtained by the above mathematical formula 1 for a maximum intensity peak at 2θ of 65° to 73° in X-ray diffraction analysis (XRD).

[0011] The above silicon powder may have a crystal size of 20 nm to 32 nm obtained by the above mathematical formula 1 for a maximum intensity peak at 2θ of 42° to 52° in X-ray diffraction analysis (XRD).

[0012] The above silicon powder may have a crystal size of 20 nm to 30 nm obtained by the above mathematical formula 1 for a maximum intensity peak at 2θ of 53° to 63° in X-ray diffraction analysis (XRD).

[0013] The above silicon powder may have a crystal size of 15 nm to 30 nm obtained by the above mathematical formula 1 for a maximum intensity peak at 2θ of 75° to 80° in X-ray diffraction analysis (XRD).

[0014] The above silicon powder may have a crystal size of 15 nm to 30 nm obtained by the above mathematical formula 1 for a maximum intensity peak at 2θ of 83° to 90° in X-ray diffraction analysis (XRD).

[0015] The above silicon powder may contain moisture in an amount of more than 0% by weight and less than 2% by weight based on the total amount of the silicon powder.

[0016] Another embodiment provides a method for producing silicon powder for use as a secondary battery negative electrode material, comprising the steps of concentrating waste slurry generated in a semiconductor process to obtain a concentrate; and drying the concentrate to obtain silicon powder, wherein the silicon powder has a crystal size of 24 nm to 50 nm obtained by the above mathematical formula 1 for a maximum intensity peak at 2θ of 23° to 33° in X-ray diffraction analysis (XRD).

[0017] The concentrate may contain 5 to 30 wt% of silicone based on the total amount of the concentrate.

[0018] The above concentration can be performed under a stirring speed of 100 rpm to 1000 rpm.

[0019] The above drying can be performed at a temperature of 130°C to 150°C.

[0020] The above drying can be performed at a rotation speed of 2 rpm to 10 rpm.

[0021] Another embodiment provides a negative electrode material for a secondary battery including the silicon powder.

[0022] According to one implementation example, silicon powder for secondary battery anode materials with excellent capacity and cycle life characteristics can be obtained from waste slurry generated during semiconductor manufacturing. This can convert discarded waste into useful materials, promoting the recycling of industrial waste and contributing to environmental protection.

[0023] Figure 1 is a flow chart showing a method for manufacturing silicon powder for a secondary battery negative electrode material according to one embodiment.

[0024] Figure 2 is an X-ray diffraction analysis (XRD) graph of silicon powder according to Example 1.

[0025] Figure 3 is an X-ray diffraction analysis (XRD) graph of silicon powder according to Comparative Example 1.

[0026] Figure 4 is an X-ray diffraction analysis (XRD) graph of silicon powder according to Comparative Example 2.

[0027] Figure 5 is a graph showing the discharge capacity of a secondary battery according to Example 1.

[0028] Figure 6 is a graph showing the discharge capacity of a secondary battery according to Comparative Example 1.

[0029] Figure 7 is a graph showing the discharge capacity of a secondary battery according to Comparative Example 2.

[0030] Figure 8 is a graph showing the life characteristics of a secondary battery according to Example 1.

[0031] Figure 9 is a graph showing the life characteristics of a secondary battery according to Comparative Example 1.

[0032] Figure 10 is a graph showing the life characteristics of a secondary battery according to Comparative Example 2.

[0033] Below, implementation examples are described in detail to facilitate their implementation by those skilled in the art. However, the scope of the rights may be implemented in various different forms and is not limited to the implementation examples described herein.

[0034] The following describes a silicon powder for use as a secondary battery negative electrode material according to an implementation example.

[0035] According to one embodiment, silicon (Si) powder for use as a secondary battery anode material can be obtained from waste slurry generated during a semiconductor process. Specifically, waste slurry consisting mostly of silicon is generated during processes such as backgrinding silicon wafers to grind the back surface of the silicon wafer, and silicon powder usable as a high-performance secondary battery anode material can be obtained from this waste slurry.

[0036] According to one embodiment, the crystal size of the silicon powder can be obtained from X-ray diffraction analysis (XRD). Specifically, in X-ray diffraction analysis (XRD) of the silicon powder, the crystal size of the silicon powder can be obtained from the maximum intensity peak appearing at any 2θ by the following mathematical equation 1.

[0037] [Mathematical Formula 1]

[0038] Crystal size (nm) = {shape factor x X-ray wavelength} / {full width at half maximum (FWHM) of maximum intensity peak x cosθ}

[0039] In the above mathematical expression 1, the shape factor is a value that varies depending on the crystallite, and can be, for example, a value of 0.68 to 2.08. The X-ray wavelength is the wavelength of CuKα rays, and can be, for example, 0.154 nm. θ represents the X-ray incident angle. The full width at half maximum (FWHM) represents the half value of the maximum intensity peak width.

[0040] According to one embodiment, the crystal size of the silicon powder obtained from Equation 1 for the maximum intensity peak at 2θ of 23° to 33° in X-ray diffraction (XRD) analysis may be 24 nm to 50 nm, for example, 28 nm to 45 nm, 32 nm to 39 nm, 34 nm to 38 nm, or 36 nm to 38 nm. When the silicon powder having the above crystal characteristics, i.e., the silicon powder having a crystal size within the above range, is used as a secondary battery negative electrode material, excellent capacity characteristics and life characteristics can be secured. In this process, by converting discarded waste into useful materials, it is possible to promote the recycling of industrial waste and also contribute to environmental protection.

[0041] In addition, according to one embodiment, the crystal size of the silicon powder obtained from Equation 1 for the maximum intensity peak at 2θ of 65° to 73° in X-ray diffraction (XRD) analysis may be 6 nm to 25 nm, for example, 10 nm to 25 nm, 15 nm to 25 nm, or 20 nm to 25 nm. When the silicon powder having the above crystal characteristics, i.e., the silicon powder having the crystal size within the above range, is used as a secondary battery negative electrode material, excellent capacity characteristics and life characteristics can be secured.

[0042] In addition, according to one embodiment, the crystal size of the silicon powder obtained from Equation 1 for the maximum intensity peak at 2θ of 42° to 52° in X-ray diffraction (XRD) analysis may be 20 nm to 32 nm, for example, 23 nm to 32 nm, 25 nm to 32 nm, or 27 nm to 32 nm. When the silicon powder having the above crystal characteristics, i.e., the silicon powder having the crystal size within the above range, is used as a secondary battery negative electrode material, excellent capacity characteristics and life characteristics can be secured.

[0043] In addition, according to one embodiment, the crystal size of the silicon powder obtained from Equation 1 for the maximum intensity peak at 2θ of 53° to 63° in X-ray diffraction (XRD) analysis may be 20 nm to 30 nm, for example, 22 nm to 29 nm, 24 nm to 28 nm, or 26 nm to 28 nm. When the silicon powder having the above crystal characteristics, i.e., the silicon powder having the crystal size within the above range, is used as a secondary battery negative electrode material, excellent capacity characteristics and life characteristics can be secured.

[0044] In addition, according to one embodiment, the crystal size of the silicon powder obtained from Equation 1 for the maximum intensity peak at 2θ of 75° to 80° in X-ray diffraction (XRD) analysis may be 15 nm to 30 nm, for example, 17 nm to 29 nm, 19 nm to 28 nm, or 21 nm to 27 nm. When the silicon powder having the above crystal characteristics, i.e., the silicon powder having the crystal size within the above range, is used as a secondary battery negative electrode material, excellent capacity characteristics and life characteristics can be secured.

[0045] In addition, according to one embodiment, the crystal size of the silicon powder obtained from Equation 1 for the maximum intensity peak at 2θ of 83° to 90° in X-ray diffraction (XRD) analysis may be 15 nm to 40 nm, for example, 20 nm to 39 nm, 25 nm to 38 nm, or 30 nm to 38 nm. When the silicon powder having the above crystal characteristics, i.e., the silicon powder having the crystal size within the above range, is used as a secondary battery negative electrode material, excellent capacity characteristics and life characteristics can be secured.

[0046] According to one embodiment, the silicon powder may contain moisture in an amount of more than 0 wt% and less than 2 wt% based on the total amount of the silicon powder. When the silicon powder contains moisture within the above range, it can be usefully used as a high-performance negative electrode material for a secondary battery.

[0047] Hereinafter, a method for manufacturing the aforementioned silicon powder will be described with reference to FIG. 1.

[0048] Figure 1 is a flow chart showing a method for manufacturing silicon powder for a secondary battery negative electrode material according to one embodiment.

[0049] Referring to FIG. 1, a silicon powder according to one embodiment can be manufactured including a step of concentrating waste slurry generated in a semiconductor process to obtain a concentrate, and a step of drying the concentrate to obtain a silicon powder.

[0050] First, the waste slurry is concentrated by evaporating moisture to obtain a concentrate. At this time, the concentrate is concentrated until it reaches a target solids concentration. Specifically, the obtained concentrate may contain 5 to 30 wt% of silicon based on the total amount of the concentrate, for example, 7 to 25 wt%, 9 to 20 wt%, or 11 to 15 wt% of silicon. When the concentration of the concentrate obtained before the drying step is within the above range, it has an appropriate level of viscosity, which can increase the hourly production volume. Since the evaporation rate is much faster than the drying rate, the heat exposure of the material can be minimized. In addition, a fine powder form can be obtained during the drying and powdering processes. Accordingly, a silicon powder useful as a high-performance secondary battery anode material can be obtained.

[0051] The concentration can be performed under a stirring speed of 100 rpm to 1000 rpm, for example, 120 rpm to 800 rpm, 130 rpm to 600 rpm, or 140 rpm to 400 rpm. When the concentration is performed under the above conditions, the heat exposure time of the material can be reduced as the evaporation proceeds at an appropriate level of speed, thereby improving capacity characteristics and preventing overload of the manufacturing equipment. Accordingly, a silicon powder useful as a high-performance secondary battery negative electrode material can be obtained.

[0052] Next, the obtained concentrate is dried to obtain silicon powder.

[0053] Drying can be performed at a temperature of 105°C to 150°C, for example, 110°C to 150°C, 120°C to 150°C, 132°C to 148°C, 135°C to 145°C, or 137°C to 145°C. When drying is performed in the above temperature range, energy can be saved as sufficient cooling is performed in the subsequent condensation process, and overload of the equipment can be prevented as there is no need to apply excessively high steam pressure. Accordingly, a silicon powder useful as a high-performance secondary battery negative electrode material can be obtained.

[0054] In addition, drying can be performed at a rotation speed of 2 rpm to 10 rpm, for example, 3 rpm to 9 rpm, 4 rpm to 8 rpm, or 4 rpm to 7 rpm. When drying is performed within the above rotation speed range, the productivity increases due to the balance with the aforementioned drying temperature, thereby increasing process efficiency, and the drying and powdering processes can be easily performed. Accordingly, a silicon powder useful as a high-performance secondary battery negative electrode material can be obtained.

[0055] The grinding process can also be performed concurrently with the drying stage to obtain silicon powder with controlled particle size. For example, when concentrated liquid raw material comes into contact with the drum surface of drying equipment such as a double drum dryer, the heat causes the moisture to evaporate, and the silicon within the raw material adheres to the drum surface. This silicon can then be scraped off with a blade to proceed with powderization. By controlling the concentration, the production of large, clumped powder can be suppressed, while silicon powder with controlled particle size can be obtained.

[0056] According to another embodiment, a negative electrode material for a secondary battery is provided, which includes the aforementioned silicon powder. According to one embodiment, when a silicon powder having the aforementioned crystal size is used as a negative electrode material for a secondary battery, excellent capacity characteristics and lifespan characteristics can be simultaneously secured.

[0057] The implementation examples described above are described in more detail through the following examples. However, the following examples are for illustrative purposes only and do not limit the scope of the rights.

[0058] (Manufacture of silicone powder)

[0059] Example 1

[0060] Waste slurry generated during semiconductor processes was introduced and concentrated at a stirring speed of 176 rpm to obtain a concentrate. The concentration process was continued until the silicon content reached 13.1 wt% of the total amount of the obtained concentrate. Subsequently, the obtained concentrate was dried at a temperature of 142°C and a rotation speed of 5 rpm to produce silicon powder.

[0061] Comparative Example 1

[0062] Waste slurry generated during semiconductor processes was introduced and concentrated at a stirring speed of 44 rpm to obtain a concentrate. The concentration process continued until the silicon content reached 8.4 wt% of the total amount of the obtained concentrate. Subsequently, the obtained concentrate was dried at a temperature of 132°C and a rotation speed of 3.75 rpm to produce silicon powder.

[0063] Comparative Example 2

[0064] Waste slurry generated during semiconductor processes was introduced and concentrated at a stirring speed of 44 rpm to obtain a concentrate. The concentration process continued until the silicon content reached 4.1 wt% of the total amount of the obtained concentrate. Subsequently, the obtained concentrate was dried at a temperature of 129°C and a rotation speed of 2.5 rpm to produce silicon powder.

[0065] Evaluation 1: Crystal size according to XRD analysis of silicon powder

[0066] X-ray diffraction analysis (XRD) using CuKα rays was performed on the silicon powders manufactured in Example 1 and Comparative Examples 1 and 2, and the results are shown in Figures 2 to 4.

[0067] FIG. 2 is an X-ray diffraction analysis (XRD) graph of a silicon powder according to Example 1, FIG. 3 is an X-ray diffraction analysis (XRD) graph of a silicon powder according to Comparative Example 1, and FIG. 4 is an X-ray diffraction analysis (XRD) graph of a silicon powder according to Comparative Example 2.

[0068] The crystal size was obtained from each X-ray diffraction analysis (XRD) graph of Figures 2 to 4 using the following mathematical formula 1, and the results are shown in Tables 1 to 3 below.

[0069] [Mathematical Formula 1]

[0070] Crystal size (nm) = {shape factor x X-ray wavelength} / {full width at half maximum (FWHM) of maximum intensity peak x cosθ}

[0071] Example 1 X-ray wavelength 0.154 nm Peak no. 2θ (°) Full width at half maximum (FWHM) (°) Crystal size (nm) Peak 128.4 15 20.23 13 7.1 Peak 247.27 60.29 3 1.2 Peak 356.10 50.33 8 27.8 Peak 469.11 20.43 23.7 Peak 576.34 10.39 226.9 Peak 688.0 1 20.44 37.1

[0072] Comparative Example 1 X-ray wavelength 0.154 nm Peak no. 2θ (°) Half width (FWHM) (°) Crystal size (nm) Peak 128.490 20.21 650.6 Peak 247.34 50.27 54 2.1 Peak 356.17 60.32 237.3 Peak 469.17 30.38 33.9 Peak 576.40 60.37 535.9 Peak 688.06 30.38 937.9

[0073] Comparative Example 2 X-ray wavelength 0.154 nm Peak no. 2θ (°) Half width (FWHM) (°) Crystal size (nm) Peak 128.46 20.33 23.7 Peak 247.33 10.47 17.6 Peak 356.16 70.44 19.6 Peak 469.36 2.43.8 Peak 576.3 130.85 11.4 Peak 688.16 0.94 11.2

[0074] Through the above Tables 1 to 3, it can be seen that in the case of Example 1, the crystal size of the silicon powder obtained from Peak 1, which is the maximum intensity peak at 2θ of 23° to 33° in X-ray diffraction analysis (XRD), is 37.1 nm, which is within the range of 24 nm to 50 nm, whereas in the case of Comparative Examples 1 and 2, the crystal sizes of the silicon powder obtained from the same Peak 1 are 50.6 nm and 23.7 nm, respectively.

[0075] Evaluation 2: Capacity characteristics of secondary batteries

[0076] The silicon powder, binder, and carbon black manufactured in Example 1 and Comparative Examples 1 and 2 were mixed in a weight ratio of 6:2:2 to manufacture each negative electrode slurry. At this time, the binder was used by mixing polyacrylic acid (PAA) dissolved in water and carboxymethylcellulose (CMC) dissolved in water in a weight ratio of 1:1. The above negative electrode slurry was applied to a copper (Cu) thin film and dried to manufacture each negative electrode.

[0077] An electrolyte was prepared by dissolving 1M LiPF6 in a solvent containing ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 3:7, and adding 10 wt% of fluoroethylene carbonate (FEC) based on the total amount of the electrolyte.

[0078] Half-cells were manufactured using each cathode and lithium counter electrode and the manufactured electrolyte. Initial charge / discharge cycles were performed at 0.05 C for the manufactured half-cells, and the resulting discharge capacities are shown in Figures 5 to 7.

[0079] FIG. 5 is a graph showing the discharge capacity of a secondary battery according to Example 1, FIG. 6 is a graph showing the discharge capacity of a secondary battery according to Comparative Example 1, and FIG. 7 is a graph showing the discharge capacity of a secondary battery according to Comparative Example 2.

[0080] Referring to FIGS. 5 to 7, it can be seen that the discharge capacity is about 2835 mAh / g for Example 1, about 1714 mAh / g for Comparative Example 1, and about 543 mAh / g for Comparative Example 2. In addition, it can be seen that the initial coulombic efficiency (ICE), which represents the discharge capacity divided by the charge capacity, is 91.2% for Example 1, 89.4% for Comparative Example 1, and 40.9% for Comparative Example 2. From this, it can be seen that when a silicon powder having a crystal size in a predetermined range according to one embodiment is used as an anode material for a secondary battery, the capacity characteristics are excellent.

[0081] Evaluation 3: Life characteristics of secondary batteries

[0082] For the half-cell manufactured in Evaluation 2, 5 charge-discharge cycles were performed at 0.2 C, and then charge-discharge cycles were performed at 0.5 C thereafter to evaluate the life characteristics, and the results are shown in Table 4 and Figures 8 to 10 below.

[0083] The capacity retention rate was calculated by the following formula.

[0084] Capacity retention rate (%) = (discharge capacity at 60 cycles / discharge capacity at 6 cycles) X 100

[0085] Discharge capacity at 6 cycles (mAh / g) Discharge capacity at 60 cycles (mAh / g) Capacity retention rate (%) Example 12250206891.91 Comparative example 11562120777.27 Comparative example 272837451.4

[0086] FIG. 8 is a graph showing the life characteristics of a secondary battery according to Example 1, FIG. 9 is a graph showing the life characteristics of a secondary battery according to Comparative Example 1, and FIG. 10 is a graph showing the life characteristics of a secondary battery according to Comparative Example 2.

[0087] Referring to Table 4 and Figures 8 to 10, in the case of Example 1, the capacity retention rate at 60 cycles compared to 6 cycles was 91.91%, whereas in the case of Comparative Examples 1 and 2, it was 77.27% and 51.4%, respectively. That is, it can be seen that in the case of Example 1, the capacity retention rate compared to the initial charge / discharge is higher than in the cases of Comparative Examples 1 and 2. From this, it can be seen that when silicon powder having a crystal size within a predetermined range according to one embodiment is used as an anode material for a secondary battery, the life characteristics are excellent.

[0088] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the claims, the description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

Claims

1. Obtained from waste slurry generated in the semiconductor process, A silicon powder for use as a secondary battery negative electrode material, having a crystal size of 24 nm to 50 nm obtained by the following mathematical formula 1 for a maximum intensity peak at 2θ of 23° to 33° in X-ray diffraction (XRD). [Mathematical Formula 1] Crystal size (nm) = {shape factor x X-ray wavelength} / {full width at half maximum (FWHM) of maximum intensity peak x cosθ} 2. In paragraph 1, The above silicon powder is a silicon powder for use as a secondary battery negative electrode material, having a crystal size of 6 nm to 25 nm obtained by the above mathematical formula 1 for a maximum intensity peak at 2θ of 65° to 73° in X-ray diffraction analysis (XRD).

3. In paragraph 1, The above silicon powder is a silicon powder for use as a secondary battery negative electrode material, having a crystal size of 20 nm to 32 nm obtained by the above mathematical formula 1 for a maximum intensity peak at 2θ of 42° to 52° in X-ray diffraction analysis (XRD).

4. In paragraph 1, The above silicon powder is a silicon powder for use as a secondary battery negative electrode material, having a crystal size of 20 nm to 30 nm obtained by the above mathematical formula 1 for a maximum intensity peak at 2θ of 53° to 63° in X-ray diffraction analysis (XRD).

5. In paragraph 1, The above silicon powder is a silicon powder for use as a secondary battery negative electrode material, having a crystal size of 15 nm to 30 nm obtained by the above mathematical formula 1 for a maximum intensity peak at 2θ of 75° to 80° in X-ray diffraction analysis (XRD).

6. In paragraph 1, The above silicon powder is a silicon powder for use as a secondary battery negative electrode material, having a crystal size of 15 nm to 30 nm obtained by the above mathematical formula 1 for a maximum intensity peak at 2θ of 83° to 90° in X-ray diffraction analysis (XRD).

7. In paragraph 1, The above silicon powder is a silicon powder for use as a secondary battery negative electrode material, which contains moisture of more than 0% by weight and less than 2% by weight based on the total amount of the silicon powder.

8. A step of concentrating waste slurry generated in a semiconductor process to obtain a concentrate; and A step of drying the above concentrate to obtain silicon powder is included. A method for producing silicon powder for use as a secondary battery negative electrode material, wherein the silicon powder has a crystal size of 24 nm to 50 nm obtained by the following mathematical formula 1 for a maximum intensity peak at 2θ of 23° to 33° in X-ray diffraction analysis (XRD). [Mathematical Formula 1] Crystal size (nm) = {shape factor x X-ray wavelength} / {full width at half maximum (FWHM) of maximum intensity peak x cosθ} 9. In paragraph 8, A method for producing silicon powder for a secondary battery negative electrode material, wherein the concentrate contains silicon in an amount of 5 to 30 wt% based on the total amount of the concentrate.

10. In paragraph 8, A method for producing silicon powder for a secondary battery negative electrode material, wherein the above concentration is performed at a stirring speed of 100 rpm to 1000 rpm.

11. In paragraph 8, A method for producing silicon powder for a secondary battery negative electrode material, wherein the above drying is performed at a temperature of 130°C to 150°C.

12. In paragraph 8, A method for producing silicon powder for a secondary battery negative electrode material, wherein the above drying is performed at a rotation speed of 2 rpm to 10 rpm.

13. A negative electrode material for a secondary battery comprising the silicon powder of any one of claims 1 to 7.

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