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

Abstract

This disclosure provides a silicon powder for a secondary battery negative electrode material, a method for preparing the same, and a secondary battery negative electrode material containing the silicon powder. The silicon powder is obtained from waste slurry generated during semiconductor manufacturing. The silicon powder contains silicon and a coating film located on the surface of the silicon and contains oxygen. The oxygen content relative to the total amount of the silicon powder is 1% to 12% by weight. The oxygen content is obtained by analyzing the content of gases released when the silicon powder is dissolved by heat treatment.

Description

[Technical Field]

[0001] This disclosure relates to a silicon powder for a secondary battery negative electrode material, a method for preparing the same, and a secondary battery negative electrode material containing the silicon powder. [Previous Technology]

[0002] The global semiconductor industry generates a massive amount of waste slurry, most of which contains silicon (Si). Environmentally friendly treatment and recycling of this waste slurry is a significant challenge. Currently, a method is needed to recycle this waste slurry and transform it into high-value-added materials.

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

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

[0005] Another embodiment provides a method for preparing silicon powder for the negative electrode material of the secondary battery.

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

[0007] One embodiment provides a silicon powder for a secondary battery negative electrode material, which is a silicon powder obtained from waste slurry generated in a semiconductor manufacturing process. The silicon powder contains silicon and a coating film located on the surface of the silicon and contains oxygen. The oxygen content is 1% to 12% by weight relative to the total amount of the silicon powder. The oxygen content is obtained by analyzing the content of gases released when the silicon powder is dissolved by heat treatment.

[0008] The oxygen content may be 3% to 10% by weight relative to the total amount of silicon powder.

[0009] The coating membrane may also contain one or more of nitrogen and hydrogen.

[0010] The coating film may contain nitrogen, and the nitrogen content may be from 0.001% by weight to 0.10% by weight relative to the total amount of silicon powder. The nitrogen content can be obtained by analyzing the content of gases released when the silicon powder is dissolved by heat treatment.

[0011] This heat treatment can be performed at temperatures above 2000°C.

[0012] The silicon powder may also contain more than 0% by weight and less than 2% by weight of moisture relative to the total amount of the silicon powder.

[0013] Another embodiment provides a method for preparing silicon powder for a secondary battery negative electrode material, comprising: a step of concentrating waste slurry generated in a semiconductor process to obtain a concentrate; and a step of drying the concentrate to obtain silicon powder, wherein the silicon powder comprises silicon and a coating film located on the surface of the silicon and contains oxygen, and the oxygen content is 1% to 12% by weight relative to the total amount of the silicon powder, and the oxygen content is obtained by analyzing the content of gases released when the silicon powder is dissolved by heat treatment.

[0014] The concentrate may contain 5% to 30% by weight of silicon relative to the total amount of the concentrate.

[0015] This concentration can be carried out at a stirring speed of 100 rpm to 1000 rpm.

[0016] The drying can be carried out at a temperature of 130°C to 150°C.

[0017] The drying can be carried out at a rotation speed of 2 rpm to 10 rpm.

[0018] Another embodiment provides a negative electrode material for secondary batteries containing the silicon powder.

[0019] According to one embodiment, silicon powder for secondary battery anode materials with excellent capacity and lifespan characteristics can be ensured from waste slurry generated in semiconductor manufacturing processes. This converts waste materials into useful materials, thereby promoting the recycling of industrial waste and contributing to environmental protection.

Implementation Method

[0021] In the following, embodiments will be described in detail to enable those skilled in the art to implement the invention. However, it can be implemented in various different ways, and the scope of the claim is not limited to the embodiments described herein.

[0022] The following describes silicon powder for a secondary battery negative electrode material according to one embodiment.

[0023] The silicon (Si) powder for secondary battery anode material according to one embodiment can be obtained from waste slurry generated in semiconductor manufacturing processes. Specifically, waste slurry composed of silicon is mostly generated in the back-side grinding process of silicon wafers, and silicon powder that can be used as a high-performance secondary battery anode material can be obtained from these waste slurries.

[0024] Silicon powder obtained from waste slurry generated during semiconductor manufacturing processes may have trace amounts of oxygen, nitrogen, hydrogen, etc. adsorbed on the silicon surface to form a coating film. According to one embodiment, the content of oxygen, etc., present on the silicon surface is adjusted to provide silicon powder that can be used as a high-performance secondary battery anode material.

[0025] Specifically, according to one embodiment, the silicon powder may include silicon and a coating film located on the silicon surface, the coating film may include oxygen.

[0026] At this point, the oxygen content relative to the total amount of silicon powder can be from 1% to 12% by weight, for example, from 3% to 10% by weight, 4% to 9% by weight, or 5% to 8% by weight. If the oxygen content is less than 1% by weight, the structural stability may decrease, for example, cracks may appear in the silicon. Silicon powder containing oxygen within this range on the silicon surface has excellent structural stability, and when used as a negative electrode material for secondary batteries, it can ensure excellent capacity and lifespan characteristics. In this process, waste materials are converted into useful materials, thereby promoting the recycling of industrial waste and contributing to environmental protection.

[0027] The oxygen content is determined by analyzing the content of gases released during the heat treatment of silicon powder. That is, during the process of heat treating and dissolving silicon powder obtained from waste slurry generated in semiconductor manufacturing, gases such as oxygen existing on the surface of silicon powder are released, and the content of the released oxygen and other gases can be analyzed.

[0028] In addition to oxygen, the coating film on the silicon surface may also contain one or more of nitrogen and hydrogen.

[0029] When the coating contains nitrogen, the nitrogen content relative to the total amount of silicon powder can be from 0.001% to 0.10% by weight, for example, from 0.005% to 0.08% by weight or from 0.01% to 0.05% by weight. When nitrogen is present on the silicon surface within this range, it can be effectively used as a secondary battery anode material with excellent capacity and lifetime characteristics.

[0030] The heat treatment for analyzing the gas content of silicon powder can be carried out at a temperature of 2000°C or higher, for example, by heating the silicon powder at a temperature of 2000°C to 5000°C.

[0031] The content analysis of this gas can be performed using an ONH analyzer. The ONH analyzer can be the ONH-p model from ELTRA or the TC-600 from LECO.

[0032] In addition, for detection, in the case of oxygen, after conversion to CO or CO2, it can be measured by an infrared adsorption detector (IR cell), and in the case of nitrogen and hydrogen, it can be measured by a thermal conductivity detector (TCD cell).

[0033] Relative to the total amount of silicon powder, the silicon powder according to one embodiment may also contain more than 0% by weight and less than 2% by weight of moisture. When the silicon powder contains moisture within this range, it can be effectively used as a high-performance negative electrode material for secondary batteries.

[0034] In the following, the method for preparing the aforementioned silicon powder will be described with reference to FIG1.

[0035] Figure 1 is a flowchart illustrating a method for preparing silicon powder for a secondary battery negative electrode material according to an embodiment.

[0036] Referring to FIG1, according to an embodiment of silicon powder, it can be prepared by a method including the following steps: concentrating waste slurry generated in a semiconductor process to obtain a concentrate; and drying the concentrate to obtain silicon powder.

[0037] First, a concentrate is obtained by evaporating water from the waste slurry. Concentration continues until the concentrate reaches a target solids concentration. Specifically, the obtained concentrate may contain 5% to 30% silicon relative to the total amount of concentrate, for example, 7% to 25%, 9% to 20%, or 11% to 15% silicon. If the concentration of the concentrate obtained before the drying step is within this range, it has an appropriate level of viscosity, thereby increasing the hourly production rate. Since the evaporation rate is much faster than the drying rate, the material is heated to a minimum, and a fine powder form can be obtained during the drying and powdering process. Thus, silicon powder useful as a high-performance secondary battery anode material can be obtained.

[0038] Concentration can be carried out at stirring speeds of 100 rpm to 1000 rpm, for example, at stirring speeds of 120 rpm to 800 rpm, 130 rpm to 600 rpm, or 140 rpm to 400 rpm. If concentration is carried out under these conditions, an appropriate level of evaporation rate is achieved, thus reducing the material's heating time, resulting in excellent capacity characteristics, and preventing overloading of the manufacturing equipment. Therefore, silicon powder useful as a high-performance secondary battery anode material can be obtained.

[0039] Next, the obtained concentrate is dried to obtain silicon powder.

[0040] Drying can be carried out at temperatures ranging from 105°C to 150°C, for example, from 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. If drying is carried out within this temperature range, energy can be saved as sufficient cooling occurs during subsequent condensation, and excessively high vapor pressures are not required, thus preventing equipment overload. Therefore, silicon powder useful as a high-performance secondary battery anode material can be obtained.

[0041] Furthermore, drying can be carried out at a rotational speed of 2 rpm to 10 rpm, for example, at a rotational speed of 3 rpm to 9 rpm, 4 rpm to 8 rpm, or 4 rpm to 7 rpm. If drying is carried out within this rotational speed range, the production volume increases and the process efficiency increases as the aforementioned drying temperature is maintained, allowing the drying and powdering processes to be carried out easily. Thus, silicon powder useful as a high-performance secondary battery anode material can be obtained.

[0042] During the drying step, a pulverization process can also be performed simultaneously to obtain silicon powder with adjusted particle size. For example, when concentrated liquid raw material comes into contact with the drum surface of a drying device such as a double 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 blades to pulverize. At this time, by adjusting the concentration, the formation of large-sized powder agglomerates can be suppressed, thereby obtaining silicon powder with adjusted particle size.

[0043] According to another embodiment, a negative electrode material for a secondary battery comprising the aforementioned silicon powder is provided. According to one embodiment, when silicon powder containing oxygen within a predetermined content range on the surface of silicon is used as a negative electrode material for a secondary battery, excellent capacity characteristics and lifetime characteristics can be ensured simultaneously.

[0044] The above-described embodiments will be described in further detail below. However, the following embodiments are intended to describe the invention only and are not intended to limit the scope of the claims.

[0045] (Preparation of silicon powder)

[0046] Example 1

[0047] Waste slurry generated during semiconductor manufacturing is added and concentrated by stirring at 176 rpm to obtain a concentrate. At this point, the concentration process continues until the silicon content reaches 13.1% by weight relative to the total amount of the concentrate obtained. Then, the concentrate obtained is dried at 142°C with a rotation speed of 5 rpm to prepare silicon powder.

[0048] Comparative Example 1

[0049] Waste slurry generated during semiconductor manufacturing is added and concentrated by stirring at 44 rpm to obtain a concentrate. At this point, the concentration process continues until the silicon content reaches 8.4% by weight relative to the total amount of the concentrate obtained. Then, the concentrate obtained is dried at 132°C with a rotation speed of 3.75 rpm to prepare silicon powder.

[0050] Comparative Example 2

[0051] Waste slurry generated during semiconductor manufacturing is added and concentrated by stirring at 44 rpm to obtain a concentrate. At this point, the concentration process continues until the silicon content reaches 4.1% by weight relative to the total amount of the concentrate obtained. Then, the concentrate obtained is dried at 129°C with a rotation speed of 2.5 rpm to prepare silicon powder.

[0052] Evaluation 1: Oxidation degree analysis of silicon powder

[0053] The oxidation degree of the silicon powder prepared in Example 1 and Comparative Examples 1 and 2 was analyzed by the following method.

[0054] After drying the silicon powder sample to remove moisture, its weight was measured. The sample was then placed in a high-temperature furnace at 3000°C to 4000°C within an ONH analyzer (ELTRA, ONH-p model) for heating. The gases released during the dissolution process of the silicon powder sample in the high-temperature furnace were separated and detected. For detection, under oxygen conditions, after conversion to CO or CO2, it could be measured using an infrared adsorption detector (IR cell) (ELTRA's ONH-p). Under nitrogen conditions, it could be measured using a thermal conductivity detector (TCD cell). The weight ratio of the measured gas to the initially added silicon powder sample was calculated, and the results are shown in Table 1 below.

[0055] In Table 1 below, the oxygen and nitrogen contents are expressed as a percentage relative to the total amount of silicon powder sample initially added.

[0056]

Table 1

[0057] As shown in Table 1 above, the analysis results of the content of gases released by silicon powder after heat treatment show that the silicon powder of Example 1 contains 6.799% by weight of oxygen, while the silicon powder of Comparative Examples 1 and 2 contains 13.63% by weight and 33.86% by weight of oxygen, respectively.

[0058] Evaluation 2: Capacity characteristics of secondary batteries

[0059] The silicon powder, binder, and carbon black prepared in Example 1, Comparative Examples 1 and 2 were mixed in a weight ratio of 6:2:2 to prepare each negative electrode slurry. For the binder, polyacrylic acid (PAA) dissolved in water and carboxymethyl cellulose (CMC) dissolved in water were mixed in a weight ratio of 1:1. This negative electrode slurry was coated onto a copper (Cu) film and dried to prepare each negative electrode.

[0060] Dissolve 1 M of LiPF6 in a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed in a volume ratio of 3:7, and add 10% by weight of fluoroethylene carbonate (FEC) relative to the total amount of electrolyte to prepare the electrolyte.

[0061] A half-cell was prepared using each negative electrode and lithium counter electrode, and using the prepared electrolyte. The prepared half-cell was initially charged and discharged at 0.05C, and the resulting discharge capacity is shown in Figures 2 to 4.

[0062] Figure 2 is a graph showing the discharge capacity of the secondary battery according to Example 1, Figure 3 is a graph showing the discharge capacity of the secondary battery according to Comparative Example 1, and Figure 4 is a graph showing the discharge capacity of the secondary battery according to Comparative Example 2.

[0063] Referring to Figures 2 to 4, in Example 1, the discharge capacity is approximately 2835 mAh / g; in Comparative Example 1, the discharge capacity is approximately 1714 mAh / g; and in Comparative Example 2, the discharge capacity is approximately 543 mAh / g. Furthermore, it can be seen that the initial coulombic efficiency (ICE), which represents the value of discharge capacity divided by charge capacity, is 91.2% in Example 1, 89.4% in Comparative Example 1, and 40.9% in Comparative Example 2. Therefore, according to one embodiment, when silicon powder containing oxygen within a predetermined content range is used as the negative electrode material for a secondary battery, it exhibits excellent capacity characteristics.

[0064] Evaluation 3: Lifetime characteristics of secondary batteries

[0065] The half-cells prepared in Evaluation 2 were subjected to 5 charge-discharge cycles at 0.2C and then to 0.5C to evaluate their lifetime characteristics. The results are shown in Table 2 and Figures 5 to 7 below.

[0066] Capacity retention is calculated using the following formula: Capacity retention (%) = (Discharge capacity at 60 cycles / Discharge capacity at 6 cycles) × 100

[0067]

Table 2

[0068] Figure 5 is a graph illustrating the life characteristics of the secondary battery according to Example 1, Figure 6 is a graph illustrating the life characteristics of the secondary battery according to Comparative Example 1, and Figure 7 is a graph illustrating the life characteristics of the secondary battery according to Comparative Example 2.

[0069] Referring to Table 2 and Figures 5 to 7, in the case of Example 1, the capacity retention rate after 60 cycles is 91.91% relative to 6 cycles, while in the cases of Comparative Examples 1 and 2, they are 77.27% and 51.4%, respectively. That is, it can be seen that, compared with Comparative Examples 1 and 2, the capacity retention rate relative to the initial charge and discharge is higher in the case of Example 1. Therefore, it can be seen that, according to one embodiment, when silicon powder containing oxygen within a predetermined content range is used as the negative electrode material for a secondary battery, it has excellent lifetime characteristics.

[0070] The preferred embodiments of the present invention have been described above, but the present invention is not limited thereto. Various modifications can be made within the scope of the claims, the specification and the drawings, and these modifications also fall within the scope of the present invention. [Simplified Explanation of the Diagram]

[0020] Figure 1 is a flowchart illustrating the preparation method of silicon powder for the negative electrode material of a secondary battery according to an embodiment. Figure 2 is a graph illustrating the discharge capacity of the secondary battery according to Example 1. Figure 3 is a graph illustrating the discharge capacity of the secondary battery according to Comparative Example 1. Figure 4 is a graph illustrating the discharge capacity of the secondary battery according to Comparative Example 2. Figure 5 is a graph illustrating the lifespan characteristics of the secondary battery according to Example 1. Figure 6 is a graph illustrating the lifespan characteristics of the secondary battery according to Comparative Example 1. Figure 7 is a graph illustrating the lifespan characteristics of the secondary battery according to Comparative Example 2.

Claims

1. A silicon powder for use as a negative electrode material in a secondary battery, wherein, The silicon powder is obtained from waste slurry generated in semiconductor manufacturing processes. The silicon powder contains silicon and a coating film on the silicon surface and contains oxygen and nitrogen. The oxygen content is 1% to 12% by weight relative to the total amount of silicon powder, and the oxygen content is obtained by analyzing the content of gases released when the silicon powder is dissolved by heat treatment.

2. The silicon powder for the negative electrode material of the secondary battery as described in claim 1, wherein, The oxygen content is 3% to 10% by weight relative to the total amount of silicon powder.

3. The silicon powder for the negative electrode material of the secondary battery as described in claim 1, wherein, The coating also contains hydrogen.

4. Silicon powder for the negative electrode material of a secondary battery as described in claim 1, wherein, The nitrogen content is 0.001% to 0.10% by weight relative to the total amount of silicon powder, and the nitrogen content is obtained by analyzing the content of gases released when the silicon powder is dissolved by heat treatment.

5. Silicon powder for the negative electrode material of a secondary battery as described in claim 1, wherein, The heat treatment is performed at temperatures above 2000°C.

6. Silicon powder for the negative electrode material of a secondary battery as described in claim 1, wherein, The silicon powder contains more than 0% by weight and less than 2% by weight of moisture relative to the total amount of the silicon powder.

7. A method for preparing silicon powder for a secondary battery negative electrode material, comprising: a step of concentrating waste slurry generated in a semiconductor process to obtain a concentrate; and a step of drying the concentrate to obtain silicon powder, wherein the silicon powder comprises silicon and a coating film located on the silicon surface and comprises oxygen and nitrogen, wherein the oxygen content relative to the total amount of the silicon powder is 1% to 12% by weight, and the oxygen content is obtained by analyzing the content of gases released when the silicon powder is dissolved by heat treatment.

8. The method for preparing silicon powder for the negative electrode material of a secondary battery as described in claim 7, wherein, The concentrate contains 5% to 30% silicon relative to the total amount of the concentrate.

9. The method for preparing silicon powder for the negative electrode material of a secondary battery as described in claim 7, wherein, The concentration was carried out with a stirring speed of 100 rpm to 1000 rpm.

10. A method for preparing silicon powder for a secondary battery negative electrode material as described in claim 7, wherein, The drying process is carried out at a temperature of 130°C to 150°C.

11. The method for preparing silicon powder for the negative electrode material of a secondary battery as described in claim 7, wherein, The drying process is carried out at a rotation speed of 2 rpm to 10 rpm.

12. A negative electrode material for a secondary battery, comprising the silicon powder described in any one of claims 1 to 6.

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