Silicon powder for negative electrode material of rechargeable battery, preparation method and negative electrode material for rechargeable battery

Abstract

A silicon powder for a negative electrode material of a rechargeable battery, a method of preparing the same, and a negative electrode material for a rechargeable battery including the same are provided. The silicon powder is obtained from a waste slurry generated in a semiconductor process, and has a crystal size ranging from 24 nm to 50 nm, obtained by Equation 1 for a maximum intensity peak at 2 [theta] of 23 DEG to 33 DEG in X-ray diffraction (XRD) analysis. Crystal size (nm) = {shape factor x x-ray wavelength} / {full width at half maximum of maximum intensity peak (FWHM) x cos theta}

Description

Technical Field

[0001] This disclosure relates to silicon powder for use as a negative electrode material in rechargeable batteries, methods for preparing the same, and negative electrode materials for rechargeable batteries including the same. Background Technology

[0002] The semiconductor industry generates a massive amount of waste slurry worldwide, and most of this waste slurry contains silicon (Si). Treating and recycling this waste slurry in an environmentally friendly manner is a significant challenge. Currently, there is a need for methods to recycle this waste slurry and transform it into materials with high added value.

[0003] Therefore, technologies for recovering silicon from waste slurry are being studied, and in particular, research is being conducted to obtain high-quality silicon for use as a negative electrode material for high-performance rechargeable batteries. Summary of the Invention

[0004] The implementation provides silicon powder for use as a negative electrode material in rechargeable batteries with excellent capacity and cycle life characteristics, the silicon powder being obtained from waste slurry generated in semiconductor processes.

[0005] Another implementation provides a method for preparing silicon powder for use as a negative electrode material in rechargeable batteries.

[0006] Another embodiment provides a negative electrode material for rechargeable batteries comprising the aforementioned silicon powder.

[0007] The implementation provides silicon powder for a negative electrode material of a rechargeable battery, the silicon powder being obtained from waste slurry generated in a semiconductor process, wherein the silicon powder has a crystal size ranging from about 24 nm to about 50 nm, and its maximum intensity peak at 2θ of 23° to 33° is obtained by Equation 1 in X-ray diffraction (XRD) analysis.

[0008] [Equation 1]

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

[0010] Silica powder can have crystal sizes ranging from about 6 nm to about 25 nm, and its maximum intensity peak at 2θ of 65° to 73° is obtained by Equation 1 in X-ray diffraction (XRD) analysis.

[0011] Silica powder can have crystal sizes ranging from about 20 nm to about 32 nm, and its maximum intensity peak at 2θ of 42° to 52° is obtained by Equation 1 in X-ray diffraction (XRD) analysis.

[0012] Silica powder can have crystal sizes ranging from about 20 nm to about 30 nm, and its maximum intensity peak at 2θ of 53° to 63° is obtained by Equation 1 in X-ray diffraction (XRD) analysis.

[0013] Silica powder can have crystal sizes ranging from about 15 nm to about 30 nm, and its maximum intensity peak at 2θ of 75° to 80° is obtained in X-ray diffraction (XRD) analysis by Equation 1.

[0014] Silica powder can have crystal sizes ranging from about 15 nm to about 30 nm, and its maximum intensity peak at 2θ of 83° to 90° is obtained by Equation 1 in X-ray diffraction (XRD) analysis.

[0015] Silicon powder may contain moisture in an amount greater than about 0 wt% and less than about 2 wt% based on the total amount of silicon powder.

[0016] Another embodiment provides a method for preparing silicon powder for a negative electrode material of a rechargeable battery, comprising 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 ranging from 24 nm to 50 nm, and its maximum intensity peak at 2θ of 23° to 33° is obtained by Equation 1 in X-ray diffraction (XRD) analysis.

[0017] The concentrate may contain organosilicon in amounts of about 5 wt% to about 30 wt% based on the total amount of the concentrate.

[0018] Concentration can be achieved at a stirring speed of approximately 100 rpm to approximately 1000 rpm.

[0019] Drying can be carried out at a temperature of approximately 130°C to approximately 150°C.

[0020] Drying can be carried out at a speed of approximately 2 rpm to approximately 10 rpm.

[0021] Another implementation provides a negative electrode material for rechargeable batteries, which comprises silicon powder.

[0022] According to the implementation plan, silicon powder used as the negative electrode material in a rechargeable battery with excellent capacity and lifespan characteristics can be obtained from waste slurry generated in semiconductor processes. This allows for the conversion of discarded waste into useful materials, thereby promoting the recycling of industrial waste and contributing to environmental protection. Attached Figure Description

[0023] Figure 1 This is a flowchart illustrating a method for preparing silicon powder for a negative electrode material of a rechargeable battery according to an embodiment.

[0024] Figure 2 The image shows an X-ray diffraction (XRD) analysis of the silicon powder according to Example 1.

[0025] Figure 3 The X-ray diffraction (XRD) analysis diagram is based on the silicon powder of Comparative Example 1.

[0026] Figure 4 The X-ray diffraction (XRD) analysis diagram is based on the silicon powder of Comparative Example 2.

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

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

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

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

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

[0032] Figure 10 This is a graph showing the cycle life characteristics of the rechargeable battery according to Comparative Example 2. Detailed Implementation

[0033] The embodiments of this disclosure will now be described in detail so that those skilled in the art can understand them. However, this disclosure may be embodied in many different forms and is not to be construed as being limited to the embodiments set forth herein.

[0034] The following describes silicon powder for a negative electrode material of a rechargeable battery according to an embodiment.

[0035] According to the implementation scheme, the silicon powder for the negative electrode material of rechargeable batteries can be obtained from waste slurry generated in semiconductors. Specifically, the waste slurry, which is mainly composed of silicon, is generated in the back-side polishing process of silicon wafers (polishing the back side of silicon wafers), and silicon powder that can be used as a high-performance negative electrode material for rechargeable batteries can be obtained from this waste slurry.

[0036] According to the implementation scheme, the crystal size of silicon powder can be obtained from X-ray diffraction (XRD) analysis. Specifically, in the X-ray diffraction (XRD) analysis of silicon powder, the crystal size of silicon powder can be obtained from the maximum intensity peak appearing at any 2θ using Equation 1.

[0037] [Equation 1]

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

[0039] In Equation 1, the shape factor can be a value that varies according to the determinant and can have, for example, a value of about 0.68 to about 2.08. The X-ray wavelength can be the wavelength of CuKα rays, for example, about 0.154 nm. θ can represent the X-ray incident angle. The full width at half maximum (FWHM) can represent the half-width of the peak intensity.

[0040] According to the implementation scheme, the crystal size of the silicon powder obtained by Equation 1 for the maximum intensity peak at 2θ of 23° to 33° in X-ray diffraction (XRD) analysis can be from about 24 nm to about 50 nm, for example, from about 28 nm to about 45 nm, from about 32 nm to about 39 nm, from about 34 nm to about 38 nm, or from about 36 nm to about 38 nm. When silicon powder with the above-mentioned crystal properties, i.e., silicon powder with crystal size within the above-mentioned range, is used as a negative electrode material for rechargeable batteries, excellent capacity characteristics and cycle life characteristics can be ensured. In this process, by converting discarded waste into useful materials, the recycling of industrial waste can be promoted and environmental protection can be contributed.

[0041] Furthermore, according to the implementation scheme, the crystal size of the silicon powder obtained by Equation 1 for the maximum intensity peak at 2θ of 65° to 73° in X-ray diffraction (XRD) analysis can be from about 6 nm to about 25 nm, for example, from about 10 nm to about 25 nm, from about 15 nm to about 25 nm, or from about 20 nm to about 25 nm. When silicon powder with the above-mentioned crystal properties, i.e., silicon powder with crystal size within the above-mentioned range, is used as a negative electrode material for rechargeable batteries, excellent capacity characteristics and cycle life characteristics can be ensured.

[0042] Furthermore, according to the implementation scheme, the crystal size of the silicon powder obtained by Equation 1 for the maximum intensity peak at 2θ of 42° to 52° in X-ray diffraction (XRD) analysis can be approximately 20 nm to approximately 32 nm, for example, approximately 23 nm to approximately 32 nm, approximately 25 nm to approximately 32 nm, or approximately 27 nm to approximately 32 nm. When silicon powder with the above-mentioned crystal properties, i.e., silicon powder with crystal size within the above-mentioned range, is used as a negative electrode material for rechargeable batteries, excellent capacity characteristics and cycle life characteristics can be ensured.

[0043] Furthermore, according to the implementation scheme, the crystal size of the silicon powder obtained by Equation 1 for the maximum intensity peak at 2θ of 53° to 63° in X-ray diffraction (XRD) analysis can be approximately 20 nm to approximately 30 nm, for example, approximately 22 nm to approximately 29 nm, approximately 24 nm to approximately 28 nm, or approximately 26 nm to approximately 28 nm. When silicon powder with the above-mentioned crystal properties, i.e., silicon powder with crystal size within the above-mentioned range, is used as a negative electrode material for rechargeable batteries, excellent capacity characteristics and cycle life characteristics can be ensured.

[0044] Furthermore, according to the implementation scheme, the crystal size of the silicon powder obtained by Equation 1 for the maximum intensity peak at 2θ of 75° to 80° in X-ray diffraction (XRD) analysis can be from about 15 nm to about 30 nm, for example, from about 17 nm to about 29 nm, from about 19 nm to about 28 nm, or from about 21 nm to about 27 nm. When silicon powder with the above-mentioned crystal properties, i.e., silicon powder with crystal size within the above-mentioned range, is used as a negative electrode material for rechargeable batteries, excellent capacity characteristics and cycle life characteristics can be ensured.

[0045] Furthermore, according to the implementation scheme, the crystal size of the silicon powder obtained by Equation 1 for the maximum intensity peak at 2θ of 83° to 90° in X-ray diffraction (XRD) analysis can be from about 15 nm to about 40 nm, for example, from about 20 nm to about 39 nm, from about 25 nm to about 38 nm, or from about 30 nm to about 38 nm. When silicon powder with the above-mentioned crystal properties, i.e., silicon powder with crystal size within the above-mentioned range, is used as a negative electrode material for rechargeable batteries, excellent capacity characteristics and cycle life characteristics can be ensured.

[0046] According to the embodiment, the silicon powder may include moisture in an amount greater than about 0 wt% and less than about 2 wt% based on the total amount of silicon powder. When the silicon powder includes moisture within the above range, it can be usefully used as a high-performance negative electrode material for rechargeable batteries.

[0047] The following will refer to Figure 1 Describe the preparation method of silicon powder.

[0048] Figure 1 This is a flowchart illustrating a method for preparing silicon powder for a negative electrode material of a rechargeable battery according to an embodiment.

[0049] Reference Figure 1 Silicon powder can be prepared according to the embodiment, which includes the steps of concentrating waste slurry generated in a semiconductor process to obtain a concentrate, and drying the concentrate to obtain silicon powder.

[0050] First, the waste slurry can be concentrated by evaporating water from it to obtain a concentrate. The waste slurry can then be concentrated until the concentrate reaches a target solids concentration. Specifically, the obtained concentrate may include organosilicon in a total amount of about 5 wt% to about 30 wt%, for example, about 7 wt% to about 25 wt%, about 9 wt% to about 20 wt%, or about 11 wt% to about 15 wt% organosilicon. When the concentration of the concentrate obtained before drying is within the above range, the concentrate can have an appropriate viscosity level, allowing for increased hourly yield, and because the evaporation rate is much faster than the drying rate, thermal exposure of the material can be minimized, and a fine powder form can be obtained during the drying and pulverization processes. Therefore, silicon powder can be obtained for use as a high-performance anode material for rechargeable batteries.

[0051] Concentration can be carried out at stirring speeds of approximately 100 rpm to approximately 1000 rpm, for example, at stirring speeds of approximately 120 rpm to approximately 800 rpm, approximately 130 rpm to approximately 600 rpm, or approximately 140 rpm to approximately 400 rpm. When concentration is carried out under the above conditions, as evaporation proceeds at an appropriate rate, the heat exposure time of the material can be reduced, resulting in excellent capacity characteristics and preventing overload of the manufacturing equipment. Therefore, silicon powder suitable for use as a high-performance anode material for rechargeable batteries can be obtained.

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

[0053] Drying can be carried out at temperatures ranging from approximately 105°C to approximately 150°C, for example, from approximately 110°C to approximately 150°C, from approximately 120°C to approximately 150°C, from approximately 132°C to approximately 148°C, from approximately 135°C to approximately 145°C, or from approximately 137°C to approximately 145°C. When drying is carried out within the above temperature range, energy can be saved because sufficient cooling is achieved during the subsequent condensation process, and overloading of the equipment can be prevented because excessively high vapor pressure does not need to be applied. Therefore, silicon powder suitable for use as a high-performance negative electrode material for rechargeable batteries can be obtained.

[0054] Alternatively, drying can be performed at rotational speeds of approximately 2 rpm to approximately 10 rpm, for example, approximately 3 rpm to approximately 9 rpm, approximately 4 rpm to approximately 8 rpm, or approximately 4 rpm to approximately 7 rpm. When drying is performed within the aforementioned rotational speed range, productivity increases as it balances with the aforementioned drying temperature, process efficiency increases, and the drying and pulverization process can be easily performed. Therefore, silicon powder suitable for use as a high-performance anode material for rechargeable batteries can be obtained.

[0055] The grinding process can also be performed simultaneously during drying to obtain silicon powder with a controllable particle size. For example, when a concentrated liquid raw material comes into contact with the drum surface of a drying device such as a dual-drum dryer, the moisture evaporates due to heat, and the silicon in the raw material adheres to the drum surface. This silicon can be scraped off with a scraper to induce pulverization. At this point, by controlling the concentration, silicon powder with a controllable particle size can be obtained while suppressing the formation of large clumps of random powder.

[0056] According to another embodiment, a negative electrode material for rechargeable batteries comprising the aforementioned silicon powder is provided. According to this embodiment, when silicon powder having the aforementioned crystal size is used as a negative electrode material for rechargeable batteries, excellent capacity characteristics and cycle life characteristics can be ensured simultaneously.

[0057] The embodiments are described in more detail below with reference to examples. However, these embodiments are exemplary, and the scope of the claims is not limited thereto.

[0058] (Preparation of silicon powder)

[0059] Example 1

[0060] Waste slurry generated during semiconductor processing is input and concentrated by stirring at 176 rpm to obtain a concentrate. The concentration process continues until the silicon content based on the total amount of the obtained concentrate becomes 13.1 wt%. Next, the obtained concentrate is dried at 142°C and 5 rpm to prepare silicon powder.

[0061] Comparative Example 1

[0062] Waste slurry generated during semiconductor processing is input and concentrated by stirring at 44 rpm to obtain a concentrate. The concentration process continues until the silicon content based on the total amount of the obtained concentrate becomes 8.4 wt%. Next, the obtained concentrate is dried at 132°C and 3.75 rpm to prepare silicon powder.

[0063] Comparative Example 2

[0064] Waste slurry generated during semiconductor processing is input and concentrated by stirring at 44 rpm to obtain a concentrate. The concentration process continues until the silicon content based on the total amount of the concentrate becomes 4.1 wt%. Next, the concentrate is dried at 129°C and 2.5 rpm to prepare silicon powder.

[0065] Evaluation 1: Crystal size based on XRD analysis of silicon powder

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

[0067] Figure 2 The image shows an X-ray diffraction (XRD) analysis of the silicon powder according to Example 1. Figure 3 The X-ray diffraction (XRD) analysis diagram is based on the silicon powder of Comparative Example 1. Figure 4 The X-ray diffraction (XRD) analysis diagram is based on the silicon powder of Comparative Example 2.

[0068] from Figures 2 to 4 The crystal size was obtained for each of the X-ray diffraction (XRD) patterns by Equation 1, and the results are shown in Tables 1 to 3 below.

[0069] [Equation 1]

[0070] Crystal size (nm) = {shape factor × X-ray wavelength} / {full width at half maximum (FWHM) of maximum intensity peak × cosθ} (Table 1)

[0071]

[0072] (Table 2)

[0073]

[0074] (Table 3)

[0075]

[0076] As can be seen from Tables 1 to 3 above, 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 (XRD) analysis) is 37.1 nm, which is in the range of about 24 nm to about 50 nm. In the cases 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.

[0077] Evaluation 2: Capacity characteristics of rechargeable batteries

[0078] The silicon powder, binder, and carbon black prepared in Example 1 and Comparative Examples 1 and 2 were mixed in a weight ratio of 6:2:2 to prepare various negative electrode slurries. The binder was prepared by mixing polyacrylic acid (PAA) dissolved in water in a weight ratio of 1:1 and carboxymethyl cellulose (CMC) dissolved in water. The negative electrode slurries were applied onto copper (Cu) films and dried to manufacture various negative electrodes.

[0079] An electrolyte was prepared by dissolving 1M LiPF6 in a solvent containing ethylene carbonate (EC) and diethyl carbonate (DEC) mixed in a volume ratio of 3:7, and adding 10 wt% fluoroethylene carbonate (FEC) based on the total amount of the electrolyte.

[0080] Half-cells were fabricated using various negative electrodes, lithium counter electrodes, and the prepared electrolyte. The fabricated half-cells underwent initial charge / discharge testing at 0.05C, and the resulting discharge capacity was [value missing]. Figures 5 to 7 As shown in the image.

[0081] Figure 5 This is a graph showing the discharge capacity of the rechargeable battery according to Example 1. Figure 6 This is a graph showing the discharge capacity of the rechargeable battery according to Comparative Example 1. Figure 7 This is a graph showing the discharge capacity of the rechargeable battery according to Comparative Example 2.

[0082] Reference Figures 5 to 7 The discharge capacity was approximately 2835 mAh / g for Example 1, approximately 1714 mAh / g for Comparative Example 1, and approximately 543 mAh / g for Comparative Example 2. Furthermore, the initial coulombic efficiency (ICE), representing the discharge capacity divided by the charge capacity, was 91.2% for Example 1, 89.4% for Comparative Example 1, and 40.9% for Comparative Example 2. Thus, it can be seen that when silicon powder having a crystal size within a predetermined range according to the embodiment is used as the negative electrode material for rechargeable batteries, excellent capacity characteristics are observed.

[0083] Evaluation 3: Cycle life characteristics of rechargeable batteries

[0084] For the half-cells manufactured in Evaluation 2, five charge / discharge cycles at 0.2C were performed, followed by subsequent cycles at 0.5C to evaluate cycle life characteristics, and the results are shown in Table 4 below. Figures 8 to 10 As shown in the image.

[0085] The capacity retention rate is calculated using the following formula.

[0086] Capacity retention (%) = (Discharge capacity at 60th cycle / Discharge capacity at 6th cycle) × 100

[0087] (Table 4)

[0088]

[0089] Figure 8 This is a graph showing the cycle life characteristics of the rechargeable battery according to Example 1. Figure 9 This is a graph showing the cycle life characteristics of the rechargeable battery according to Comparative Example 1. Figure 10This is a graph showing the cycle life characteristics of the rechargeable battery according to Comparative Example 2.

[0090] Refer to Table 4 and Figures 8 to 10 Compared to the 6th cycle, the capacity retention rate after the 60th cycle was 91.91% in Example 1, while it was 77.27% and 51.4% in Comparative Examples 1 and 2, respectively. That is, Example 1 exhibited a higher capacity retention rate relative to the initial charge / discharge cycle than Comparative Examples 1 and 2. This demonstrates that when silicon powder with a crystal size within a predetermined range according to the embodiment is used as the negative electrode material for rechargeable batteries, excellent cycle life characteristics are achieved.

[0091] Although the embodiments of this disclosure have been described in detail above, the scope of this disclosure is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of this disclosure as defined in the appended claims also fall within the scope of this disclosure.

Claims

1. A silicon powder for use as a negative electrode material in rechargeable batteries. The silicon powder is obtained from waste slurry generated during semiconductor processes. The silicon powder described herein has a crystal size ranging from 24 nm to 50 nm, and its maximum intensity peak at 2θ of 23° to 33° is obtained in X-ray diffraction (XRD) analysis by Equation 1: [Equation 1] Crystal size (nm) = {shape factor × X-ray wavelength} / {full width at half maximum (FWHM) of maximum intensity peak × cosθ}.

2. The silicon powder for the negative electrode material of a rechargeable battery according to claim 1, wherein: The silicon powder has a crystal size ranging from 6 nm to 25 nm, and its maximum intensity peak at 2θ of 65° to 73° is obtained by Equation 1 in X-ray diffraction (XRD) analysis.

3. The silicon powder for the negative electrode material of a rechargeable battery according to claim 1, wherein: The silicon powder has a crystal size ranging from 20 nm to 32 nm, and its maximum intensity peak at 2θ of 42° to 52° is obtained by Equation 1 in X-ray diffraction (XRD) analysis.

4. The silicon powder for the negative electrode material of a rechargeable battery according to claim 1, wherein: The silicon powder has a crystal size ranging from 20 nm to 30 nm, and its maximum intensity peak at 2θ of 53° to 63° is obtained by Equation 1 in X-ray diffraction (XRD) analysis.

5. The silicon powder for the negative electrode material of a rechargeable battery according to claim 1, wherein: The silicon powder has a crystal size ranging from 15 nm to 30 nm, and its maximum intensity peak at 2θ of 75° to 80° is obtained by Equation 1 in X-ray diffraction (XRD) analysis.

6. The silicon powder for the negative electrode material of a rechargeable battery according to claim 1, wherein: The silicon powder has a crystal size ranging from 15 nm to 30 nm, and its maximum intensity peak at 2θ of 83° to 90° is obtained by Equation 1 in X-ray diffraction (XRD) analysis.

7. The silicon powder for the negative electrode material of a rechargeable battery according to claim 1, wherein: The silicon powder contains moisture in an amount greater than 0 wt% and less than 2 wt% based on the total amount of the silicon powder.

8. A method for preparing silicon powder for a negative electrode material in a rechargeable battery, comprising: Concentrating waste slurry generated in semiconductor processes to obtain concentrates, and The concentrate is dried to obtain silicon powder. The silicon powder described herein has a crystal size ranging from 24 nm to 50 nm, and its maximum intensity peak at 2θ of 23° to 33° is obtained in X-ray diffraction (XRD) analysis by Equation 1: [Equation 1] Crystal size (nm) = {shape factor × X-ray wavelength} / {full width at half maximum (FWHM) of maximum intensity peak × cosθ}.

9. The method for preparing silicon powder for a negative electrode material of a rechargeable battery according to claim 8, wherein: The concentrate contains 5 wt% to 30 wt% organosilicon based on the total amount of the concentrate.

10. The method for preparing silicon powder for a negative electrode material of a rechargeable battery according to claim 8, wherein: Concentration is carried out at a stirring speed of 100 rpm to 1000 rpm.

11. The method for preparing silicon powder for a negative electrode material of a rechargeable battery according to claim 8, wherein: Drying is carried out at a temperature of 130°C to 150°C.

12. The method for preparing silicon powder for a negative electrode material of a rechargeable battery according to claim 8, wherein: Drying is carried out at speeds of 2 to 10 rpm.

13. A negative electrode material for a rechargeable battery, comprising silicon powder according to any one of claims 1 to 7.

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