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

Abstract

Provided are silicon powder for a secondary battery negative electrode material, a preparation method therefor, and a secondary battery negative electrode material comprising same . The silicon powder is obtained from waste slurry generated in a semiconductor process and comprises: silicon; and a film positioned on the surface of the silicon and containing oxygen, wherein the content of the oxygen is 1-12 wt% based on the total amount of the silicon powder, and the content of the oxygen is obtained by content analysis of gas released during dissolution when the silicon powder is heat-treated.

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 use as a secondary battery negative electrode material, which is obtained from waste slurry generated in a semiconductor process, and which includes silicon and a film located on the surface of the silicon and containing oxygen, wherein the content of the oxygen is 1 wt% to 12 wt% based on the total amount of the silicon powder, and the content of the oxygen is obtained by analyzing the content of gas released when the silicon powder is melted by heat treatment.

[0008] The content of the oxygen may be 3 wt% to 10 wt% with respect to the total amount of the silicon powder.

[0009] The above film may further comprise one or more selected from nitrogen and hydrogen.

[0010] The above film may include the nitrogen, and the content of the nitrogen may be 0.001 wt% to 0.10 wt% with respect to the total amount of the silicon powder, and the content of the nitrogen may be obtained by content analysis of gas released when the silicon powder is heat-treated and melted.

[0011] The above heat treatment can be performed by heating at a temperature of 2000°C or higher.

[0012] The above silicon powder may further contain moisture in an amount of more than 0 wt% and less than 2 wt% based on the total amount of the silicon powder.

[0013] Another embodiment provides a method for producing silicon powder for 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 includes silicon and a film located on a surface of the silicon and containing oxygen, the content of the oxygen being 1 wt% to 12 wt% based on the total amount of the silicon powder, and the content of the oxygen being obtained by content analysis of a gas released when the silicon powder is melted by heat treatment.

[0014] The concentrate may contain from 5 wt% to 30 wt% of silicone based on the total amount of the concentrate.

[0015] The above concentration can be performed under a stirring speed of 100 rpm to 1000 rpm.

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

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

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

[0019] 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.

[0020] Figure 1 is a flow chart showing a method for manufacturing silicon powder for a secondary battery negative electrode material according to one embodiment.

[0021] Figure 2 is a graph showing the discharge capacity of a secondary battery according to Example 1.

[0022] Figure 3 is a graph showing the discharge capacity of a secondary battery according to Comparative Example 1.

[0023] Figure 4 is a graph showing the discharge capacity of a secondary battery according to Comparative Example 2.

[0024] Figure 5 is a graph showing the life characteristics of a secondary battery according to Example 1.

[0025] Figure 6 is a graph showing the life characteristics of a secondary battery according to Comparative Example 1.

[0026] Figure 7 is a graph showing the life characteristics of a secondary battery according to Comparative Example 2.

[0027] 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.

[0028] The following describes a silicon powder for use as a secondary battery negative electrode material according to an implementation example.

[0029] 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.

[0030] Silicon powder obtained from waste slurry generated during semiconductor processes may have trace amounts of oxygen, nitrogen, hydrogen, etc. adsorbed on the surface of the silicon to form a film. According to one embodiment, by controlling the content of oxygen, etc. present on the surface of the silicon, silicon powder usable as a high-performance secondary battery anode material is provided.

[0031] Specifically, the silicon powder according to one embodiment may include silicon and a film positioned on the surface of the silicon, and the film may include oxygen.

[0032] At this time, the oxygen content may be 1 wt% to 12 wt% with respect to the total amount of silicon powder, for example, 3 wt% to 10 wt%, 4 wt% to 9 wt%, or 5 wt% to 8 wt%. If the oxygen content is less than 1 wt%, the structural stability of the silicon may be reduced, such as cracks occurring on the silicon. The silicon powder containing oxygen within the above content range on the silicon surface has excellent structural stability, and when used as a secondary battery negative electrode material, it can secure excellent capacity characteristics and life characteristics. In this process, by converting discarded waste into useful materials, it can promote the recycling of industrial waste and contribute to environmental protection.

[0033] Oxygen content can be measured by analyzing the gases released during the heat treatment of silicon powder. Specifically, during the process of melting silicon powder obtained from waste slurry generated during semiconductor processes through heat treatment, gases such as oxygen present on the surface of the silicon powder are released. Analysis of the released oxygen and other gases can be performed.

[0034] The film located on the surface of the silicon may further contain one or more selected from nitrogen and hydrogen in addition to oxygen.

[0035] When the film contains nitrogen, the nitrogen content may be 0.001 wt% to 0.10 wt% with respect to the total amount of the silicon powder, for example, 0.005 wt% to 0.08 wt%, or 0.01 wt% to 0.05 wt%. When nitrogen is present on the silicon surface within the above content range, it can be usefully used as a secondary battery negative electrode material with excellent capacity characteristics and lifespan characteristics.

[0036] Heat treatment for analyzing the gas content from silicon powder can be performed at a temperature of 2000°C or higher, for example, by heating the silicon powder at a temperature of 2000°C to 5000°C.

[0037] Analysis of the content of the above gas can be performed using an ONH analyzer. The ONH analyzer can be an ONH-p model from ELTRA or a TC-600 from LECO.

[0038] Additionally, detection can be measured with an infrared absorption detector (IR cell) for oxygen gas after conversion to CO or CO2, and with a thermal conductivity detector (TCD cell) for nitrogen gas and hydrogen gas.

[0039] According to one embodiment, the silicon powder may further include 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 includes moisture within the above range, it can be usefully used as a high-performance negative electrode material for a secondary battery.

[0040] Hereinafter, a method for manufacturing the aforementioned silicon powder will be described with reference to FIG. 1.

[0041] Figure 1 is a flow chart showing a method for manufacturing silicon powder for a secondary battery negative electrode material according to one embodiment.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] Next, the obtained concentrate is dried to obtain silicon powder.

[0046] 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 within the above temperature range, sufficient cooling is achieved in the subsequent condensation process, thereby saving energy, and overloading of the equipment can be prevented since 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.

[0047] 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.

[0048] 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.

[0049] 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 containing a predetermined content range of oxygen on the silicon surface is used as a negative electrode material for a secondary battery, excellent capacity characteristics and lifespan characteristics can be secured simultaneously.

[0050] 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.

[0051] (Manufacture of silicone powder)

[0052] Example 1

[0053] 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.

[0054] Comparative Example 1

[0055] 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.

[0056] Comparative Example 2

[0057] 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.

[0058] Evaluation 1: Oxidation analysis of silicon powder

[0059] Oxidation analysis was performed on the silicon powders manufactured in Example 1 and Comparative Examples 1 and 2 using the following method.

[0060] After drying the silicon powder sample to remove moisture and measuring the weight, the silicon powder sample was heated in a high-temperature furnace at 3000℃ to 4000℃ in an ONH analyzer (ELTRA, ONH-p model). The gases released during the melting process of the silicon powder sample in the high-temperature furnace were separated and detected. In the case of oxygen gas, it was converted to CO or CO2 and measured with an infrared absorption detector (IR cell) (ELTRA, ONH-p), and in the case of nitrogen gas, it was measured with a thermal conductivity detector (TCD cell). The weight ratio of the measured gases and the initially introduced silicon powder sample was calculated, and the results are shown in Table 1 below.

[0061] In Table 1 below, the contents of oxygen and nitrogen are expressed as percentages of the total amount of initially introduced silicon powder sample.

[0062] Oxygen (wt%) Nitrogen (wt%) Example 16.7990.012 Comparative Example 113.63-Comparative Example 233.860.126

[0063] As shown in Table 1 above, the silicon powder of Example 1 contained 6.799 wt% of oxygen as a result of analysis of the content of the gas released through heat treatment of the silicon powder, whereas the silicon powders of Comparative Examples 1 and 2 contained 13.63 wt% and 33.86 wt% of oxygen, respectively.

[0064] Evaluation 2: Capacity characteristics of secondary batteries

[0065] 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.

[0066] 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.

[0067] 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 2 to 4.

[0068] FIG. 2 is a graph showing the discharge capacity of a secondary battery according to Example 1, FIG. 3 is a graph showing the discharge capacity of a secondary battery according to Comparative Example 1, and FIG. 4 is a graph showing the discharge capacity of a secondary battery according to Comparative Example 2.

[0069] Referring to FIGS. 2 to 4, 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 containing oxygen in a predetermined content range according to one embodiment is used as an anode material for a secondary battery, the capacity characteristics are excellent.

[0070] Evaluation 3: Life characteristics of secondary batteries

[0071] 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 to evaluate the life characteristics, and the results are shown in Table 2 and Figures 5 to 7 below.

[0072] The capacity retention rate was calculated by the following formula.

[0073] Capacity retention rate (%) = (discharge capacity at 60 cycles / discharge capacity at 6 cycles) X 100

[0074] 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

[0075] FIG. 5 is a graph showing the life characteristics of a secondary battery according to Example 1, FIG. 6 is a graph showing the life characteristics of a secondary battery according to Comparative Example 1, and FIG. 7 is a graph showing the life characteristics of a secondary battery according to Comparative Example 2.

[0076] Referring to Table 2 and Figures 5 to 7, 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 a silicon powder containing oxygen in a predetermined content range according to one embodiment is used as an anode material for a secondary battery, the life characteristics are excellent.

[0077] 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. Silicon powder obtained from waste slurry generated in the semiconductor process. Comprising silicon and a film containing oxygen located on the surface of the silicon, The content of the oxygen is 1 wt% to 12 wt% based on the total amount of the silicon powder, The above oxygen content is obtained by analyzing the content of gas released when the above silicon powder is melted by heat treatment, and is a silicon powder for use as a negative electrode material for a secondary battery.

2. In paragraph 1, A silicon powder for use as a negative electrode material for a secondary battery, wherein the oxygen content is 3 wt% to 10 wt% based on the total amount of the silicon powder.

3. In paragraph 1, The above film is a silicon powder for a secondary battery negative electrode material, further comprising at least one selected from nitrogen and hydrogen.

4. In paragraph 3, The above film contains the nitrogen, The content of the above nitrogen is 0.001 wt% to 0.10 wt% with respect to the total amount of the above silicon powder, The above nitrogen content is obtained by analyzing the content of gas released when the above silicon powder is heat-treated and melted, and is a silicon powder for use as a negative electrode material for a secondary battery.

5. In paragraph 1, The above heat treatment is performed by heating the silicon powder for use as a negative electrode material for secondary batteries at a temperature of 2000°C or higher.

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

7. 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. The above silicon powder comprises silicon and a film containing oxygen located on the surface of the silicon, The content of the oxygen is 1 wt% to 12 wt% based on the total amount of the silicon powder, A method for manufacturing silicon powder for use as a secondary battery negative electrode material, wherein the oxygen content is obtained by analyzing the content of gas released when the silicon powder is heat-treated and melted.

8. In paragraph 7, 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.

9. In paragraph 7, 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.

10. In paragraph 7, 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.

11. In paragraph 7, 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.

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

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