KR20220105418A - Manufacturing method of Silicon/Carbon nanotube/Graphene Composite film as Anode Materials for Lithiumion Batteries and Manufacturing method for Lithiumion Batteries using it - Google Patents

Abstract

The present invention provides a method for manufacturing a silicon/carbon nanotube/graphene composite and a method for manufacturing a secondary battery using the same. The method for manufacturing a silicon/carbon nanotube/graphene composite includes: a step (a) of preparing a SiNPs/CNT mixed solution by adding predetermined silicon nanoparticles and carbon nanotube powder to ethanol, stirring a mixture, and ultrasonicating the mixture for a predetermined time; a step (b) of preparing a SiNPs/CNT/GO dispersion by adding a GO aqueous solution to the SiNPs/CNT mixed solution prepared in the step (a), ultrasonicating a resulting mixture, and stirring the same for a predetermined time; a step (c) of producing a SiNPs/CNT/GO composite film by filtering and drying the SiNPs/CNT/GO dispersion; and a step (d) of producing a thermally reduced SiNPs/CNT/rGO composite film through a heat treatment process. According to the present invention, cycle efficiency can be improved.

Description

Silicon/carbon nanotube/graphene composite manufacturing method and secondary battery manufacturing method using the same

The present invention relates to a negative electrode material for a lithium ion battery, and more particularly, to a method for manufacturing a silicon/carbon nanotube/graphene composite and a secondary battery manufacturing method using the same as a negative electrode material for a lithium ion secondary battery.

Batteries are divided into primary batteries that can be used once and secondary batteries that can be recharged and used repeatedly. The development of secondary batteries coincided with the development of automobiles in the 1900s. Starting with lead-acid batteries used in automobiles and industrial devices that require constant power supply to devices, nickel-based batteries have developed into lithium-ion batteries. Lithium-ion batteries (LIBs) are attracting attention as the most promising secondary batteries because they have advantages such as high energy density and voltage per unit volume, excellent output density, stable cycle, and environmental friendliness. Previous batteries were used as parts to be installed in small electronic devices and portable electronic devices, and were focused on high capacity and light weight. However, for next-generation batteries to be used as parts for moving larger devices such as electric vehicles, high-capacity, high-stability, and long-life batteries with a long lifespan, high energy capacity, and guaranteed stability will be required.

Graphite, which is currently commercialized as an anode material for lithium-ion batteries, has abundant reserves, is inexpensive, and exhibits low potential and excellent cycle performance. In addition, the layered structure facilitates insertion and desorption of lithium ions into the structural gap, and is stable even if this process is repeated. However, it has a capacity limitation with a low theoretical capacity of 372 mAh/g, and the charging speed is not fast, so it is not sufficient as a next-generation lithium-ion battery anode material that requires high capacity and high output. Therefore, in order to increase the energy density of lithium-ion batteries, research using silicon as a high-capacity anode material is being actively conducted.

Silicon, which has recently been attracting attention as an anode material, has abundant reserves, a moderate operating potential, and a high theoretical capacity of 4,200 mAh/g. However, in the process of charging and discharging, it undergoes volume expansion and contraction of up to 400%, and cracks and pulverization of the material occur, resulting in a sharp decrease in the life of the electrode. In addition, the solid electrolyte interphase (SEI) formed on the silicon surface at a potential of less than 1 V changes in volume as the charge/discharge cycle progresses and becomes thicker. In this case, lithium ions cannot enter the silicon, causing capacity loss, and increasing the internal impedance of the battery, which eventually leads to deterioration of the battery. The volume expansion process of silicon is shown in FIG. 1 .

To solve these problems, nanoparticles, nanowires, nanotubes, and nanospheres Research on forming a composite material by using nano-structured silicon such as, or combining silicon and carbon materials is being actively conducted. In particular, research on the combination of carbon materials and silicon is receiving a lot of attention from the industrial point of view. The demand for medium and large-sized lithium ion batteries requires lithium ion batteries with high capacity and high initial coulombic efficiency and capacity retention. Silicon has high capacity and graphite has excellent capacity retention and coulombic efficiency. / Research and development of a method of forming a carbon material is being carried out. The recent development of a silicon-based next-generation anode material is shown in FIG. 2 .

Korean Patent Publication No. 10-2020-0133134 (published on November 26, 2020)

The present invention has been devised to solve the above-described problems, and a method for manufacturing a secondary battery by forming a silicon nanoparticle/carbon nanotube/graphene composite film without a binder and using it as a negative electrode material for a lithium ion secondary battery. intended to provide

To this end, an embodiment of the present invention comprises the steps of: (a) adding predetermined silicon nanoparticles and carbon nanotube powder to ethanol, stirring the mixture, and ultrasonically treating the mixture for a predetermined time to prepare a SiNPs/CNT mixed solution; (b) preparing a SiNPs/CNT/GO dispersion by adding an aqueous GO solution to the SiNPs/CNT mixed solution prepared in step (a), sonicating the resulting mixture and stirring for a predetermined time; (c) filtering and drying the SiNPs/CNT/GO dispersion to prepare a SiNPs/CNT/GO composite film; and (d) preparing a thermally reduced SiNPs/CNT/rGO composite film through a heat treatment process.

Another embodiment of the present invention, (a) preparing a SiNPs/CNT mixed solution by adding a predetermined silicon nanoparticles and carbon nanotube powder to ethanol, stirring the mixture, and then sonicating the mixture for a predetermined time; (b) preparing a SiNPs/CNT/GO dispersion by adding an aqueous GO solution to the SiNPs/CNT mixed solution prepared in step (a), sonicating the resulting mixture and stirring for a predetermined time; (c) filtering and drying the SiNPs/CNT/GO dispersion to prepare a SiNPs/CNT/GO composite film; (d) preparing a thermally reduced SiNPs/CNT/rGO composite film through a heat treatment process; And (e) using the SiNPs / CNT / rGO composite film as an anode material provides a secondary battery manufacturing method comprising the step of manufacturing a secondary battery.

In addition, in the step (a), the silicon nanoparticles and the carbon nanotube powder is characterized in that it is added in a mass ratio of 1: 1.

In addition, in step (b), it is characterized in that it is added in a volume ratio of 7.5% to 12.5% compared to the SiNPs/CNT mixed solution prepared in step (a).

In addition, in step (c), the SiNPs / CNT / GO dispersion is characterized in that the vacuum filtering using a PTFE filter.

In addition, in step (c), the thickness of the SiNPs/CNT/GO composite film is controlled by adjusting the volume of the dispersion during the filtering process of the SiNPs/CNT/GO dispersion.

In addition, it is characterized in that the discharge capacity is controlled by adding the SiNPs/CNT/GO dispersion in the range of 20 to 30 ml.

In addition, in step (d), the SiNPs/CNT/GO composite film was put into a quartz tube during the heat treatment process, and the temperature was raised to a maximum of 550° C. to flow Ar gas to prepare a thermally reduced SiNPs/CNT/rGO composite film. characterized in that

In addition, in step (e), the electrolyte is formed by dissolving 1M LiPF ₆ in a solution mixed with ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) in a 1:1:1 volume ratio. characterized.

In addition, it is characterized in that the SiNPs/CNT/rGO composite film is used as a working electrode without using a conductive additive and a binder, and Li metal is used as a counter electrode and a reference electrode.

In the present invention, carbon-based material and silicon are combined to improve the performance of the lithium-ion battery used in the past and used as an anode material for a lithium-ion battery. By combining fins and carbon nanotubes, the disadvantages of individual materials were supplemented.

Through this, by preventing the direct contact of the silicon surface with the electrolyte to suppress the additive reaction, the solid electrolyte interfacial layer formation is prevented, and the carbon nanotubes provide a flexible three-dimensional space that alleviates the volume expansion of silicon, thereby improving cycle efficiency and battery life. can be seen to improve.

1 is a schematic diagram showing the volume expansion process of silicon during cycling;
2 is a schematic diagram showing the development direction of a recent silicon-based next-generation anode material;
Figure 3 is a view showing the manufacturing process of the SiNPs / CNT / rGO composite film according to a preferred embodiment of the present invention;
4 is a view showing the SEM image of each magnification of the SiNPs / CNT / rGO composite film and the SiNPs / rGO composite film according to a preferred embodiment of the present invention;
5 is a view showing a TEM image of each magnification of the SiNPs / CNT / rGO composite film and the SiNPs / rGO composite film according to a preferred embodiment of the present invention;
6 is a view showing an elemental mapping image of a SiNPs/CNT/rGO composite film and a SiNPs/rGO composite film according to a preferred embodiment of the present invention;
7 is a diagram showing a high magnification TEM image of a SiNPs/CNT/rGO composite film and a SiNPs/rGO composite film according to a preferred embodiment of the present invention;
Figure 8a is a graph showing the XRD patterns of GO, rGO, Si, SiNPs/rGO, CNT, SiNPs/CNT/rGO according to a preferred embodiment of the present invention, Figure 8b is GO, rGO according to a preferred embodiment of the present invention , a graph showing the Raman spectra of SiNPs/rGO, SiNPs/CNT/rGO,
9a to 9d are graphs showing C1s XPS spectra of SiNPs/GO, SiNPs/rGO, SiNPs/CNT/GO and SiNPs/CNT/rGO according to a preferred embodiment of the present invention, and FIG. 9e is SiNPs/CNT/rGO A graph showing the Si 2p XPS spectrum of
FIG. 10 shows 0.01-15 V (vs. Li/ A graph showing the cyclic voltammogram showing the voltage range of Li ⁺ ) and the first and fifth cycles measured at 0.1 mV/s,
11 is a Nyquist plot and cycle performance by thickness of a SiNPs/CNT/rGO composite film according to a preferred embodiment of the present invention with current density and voltage range of 0.1 A/g and 0.01-1.5 V. the drawing shown.

Hereinafter, with reference to the accompanying drawings, the manufacturing process of the silicon nanoparticle/carbon nanotube/rGO composite film according to a preferred embodiment of the present invention will be described in detail.

1. Synthesis of SiNPs/CNT/rGO Composite Films

The manufacturing process of the nano-silicon/carbon nanotube/graphene composite film is shown in FIG. 3 .

Silicon nanoparticles (powder, APS≤50 nm, 98%, Alfa Aesar, Inc, 0.3g) and carbon nanotube (0.3g) powder were placed in ethanol (anhydrous, 99.9%, Sigma-Aldrich, 300 mL) and stirred. After that, sonication was performed for 2 hours. At this time, it is preferable that silicon nanoparticles (0.3 g) and carbon nanotube powder (0.3 g) are added in a mass ratio of 1: 1.

Then, an aqueous solution of graphene oxide (30 mL) was added to the SiNPs/CNT mixed solution and sonicated for 2 hours. At this time, compared to the SiNPs / CNT mixed solution (300ml), the graphene oxide aqueous solution is preferably added in a volume ratio of 7.5% to 12.5%, and optimally in a range of 10% (30ml). After stirring for 2 hours, a SiNPs/CNT/GO dispersion was obtained. The SiNPs/CNT/GO dispersion was vacuum filtered using a PTFE filter (0.5 um) to obtain a composite film and dried for 48 hours.

The prepared SiNPs/CNT/GO composite film was placed in a horizontal quartz tube, the temperature was raised to 550 °C, and a constant flow rate of argon gas was flowed. In this way, a thermally reduced SiNPs/CNT/rGO composite film was finally prepared. Carbon nanotubes and graphene oxide were purchased from JEIO (Jeno Tube 10B) and Angstron materials (N002-PS, 5.0%), respectively, and used as they are.

The manufacturing process of the SiNPs/rGO composite film used as a control for characterization was carried out in the same manner as above without carbon nanotubes, and the electrochemical performance of the SiNPs/CNT/GO dispersion was applied to the film by varying the volume of the solution during the vacuum filter process. was compared by adjusting the thickness of

2. Material properties

To analyze the morphology and microstructure of the SiNPs/CNT/rGO composite film and the Si/rGO composite film used as a control, a scanning electron microscope (SEM, Scanning Electron Microscope, Hitachi, S-4800) and a transmission electron microscope (TEM) microscope, JEOL, JEM-2100) was used.

In order to check the composition and crystallinity of the sample, the range of 2θ is 5-85° and X-ray diffraction analysis (XRD, X-ray Diffraction, PANalytical, X'pert PRO-) with Cu Kαradiation (λ= 1.5425Å) MPD) was performed. Raman spectroscopy (Raman, Raman spectroscopy, Horiba Jobin-Yvon, LABRAM HR-800) was analyzed in the range of 100-3000 cm ^-1 . The binding energy of the sample was measured by X-ray photoelectron spectroscopy (XPS, X-ray Photoelectron Spectroscopy, Thermo Fisher Scientific, Multilab-2000).

2.3 Electrochemical properties

In the present invention, the SiNPs/CNT/rGO composite film was used as an anode active material for a lithium ion battery to prepare a battery without other conductive additives and binders. A lithium metal foil was used as a counter electrode and a reference electrode, and Celgard 2600 was used as a separator. A 1M LiPF ₆ solution dissolved in a solution of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) in a 1:1 volume ratio was used as the electrolyte in a glove box filled with argon ( CR2032) was assembled.

The assembled cells have a voltage range of 0.01-1.5V (vs. Li/Li+) and charge/discharge capacity up to 30 cycles through galvanostatic charge-discharge (WonATech Co., Ltd, WBCS3000). measured.

In addition, electrochemical properties were investigated through cyclic voltammetry and electrochemical impedance spectroscopy.

3. Results and Discussion

4a to 4c show SEM images of the SiNPs/rGO composite film for each magnification, and FIGS. 4d to 4f show the SEM images for each magnification of the SiNPs/CNT/rGO composite film.

4A to 4F , in both samples, silicon and wrinkled graphene sheets were observed in both samples, and silicon nanoparticles were uniformly dispersed on the graphene.

4D to 4F, unlike the SiNPs/rGO composite film, long filamentous carbon nanotubes were additionally observed, and the carbon nanotubes were densely entangled with silicon and graphene to form a stable three-dimensional structure. knew what to do

TEM analysis was performed to further investigate the shape and composition of the sample, which is shown in FIG. 5 .

5a to 5c show TEM images of SiNPs/rGO composite films at different magnifications, and FIGS. 5d to 5f show TEM images of SiNPs/CNT/rGO composite films at different magnifications.

Referring to FIGS. 5A to 5F , as in the SEM image, round silicon nanoparticles and wrinkled graphene sheets were seen in the SiNPs/rGO composite film and the SiNPs/CNT/rGO composite film. It can be seen more clearly in Figure 5c. Referring to FIGS. 5D to 5F , long and thin carbon nanotubes could be additionally observed, and it could be seen that the carbon nanotubes formed a structure woven with SiNPs/rGO together with SiNPs/rGO in the composite.

6a to 6d are respectively (a) TEM image of SiNPs/rGO composite film, (b) C element mapping image of SiNPs/rGO composite film, (c) O element mapping image of SiNPs/rGO composite film, (d) This shows the Si element mapping image of the SiNPs/rGO composite film.

6e to 6h are respectively (e) TEM image of SiNPs/CNT/rGO composite film, (f) C element mapping image of SiNPs/CNT/rGO composite film, and (g) O element of SiNPs/CNT/rGO composite film. Mapping image, (h) shows the Si element mapping image of SiNPs/CNT/rGO composite film

Looking at the element mapping image of FIG. 6 , it was confirmed that carbon, oxygen, and silicon appeared and uniformly dispersed in both samples. As can be seen from Table 1, the content of each element in the two samples was about 30-32% carbon, 6-7% oxygen, and 61% silicon. In the case of the SiNPs/CNT/rGO composite film, as carbon nanotubes were added, the carbon content slightly increased and the oxygen and silicon content decreased compared to the SiNPs/rGO composite film.

element C (%) O(%) Si (%) Total (%) SiNPs/rGO (wt%) 30.8 7.75 61.5 100 SiNPs/CNT/rGO (wt%) 32.1 6.74 61.2 100

7a shows a high magnification TEM image of the SiNPs/rGO composite film, and FIGS. 7b and 7c show a high magnification TEM image of the SiNPs/CNT/rGO composite film.

In FIG. 7, which is a high-magnification TEM image, the lattice spacing of silicon is 0.31 nm and the lattice spacing of graphene is 0.19 nm, which is the same as in FIGS. 7a and 7b, which corresponds to the crystal structure 111 of silicon.

Looking at the SAED (Selected Area Electron Diffraction) pattern inserted in FIG. 7b, (002) corresponding to the graphite crystal structure, (111), (220), (311), and (400) corresponding to the silicon crystal structure are ring shapes. The diffraction pattern of , coincided with the XRD pattern of the complex. The presence of carbon nanotubes in the SiNPs/CNT/rGO composite film was confirmed as the lattice spacing of carbon nanotubes of 0.36 nm was observed in FIG. 7c.

In order to investigate the crystallinity of the SiNPs/CNT/rGO composite film, XRD analysis of GO, rGO, Si, SiNPs/rGO, CNT, and SiNPs/CNT/rGO was performed, shown in Fig. 8a and comparatively analyzed.

Referring to FIG. 8a, first, graphene oxide (GO) showed a strong and narrow peak at 2θ = 9.6°. After thermal reduction of reduced graphene oxide (rGO), the characteristic peak of GO at 9.6° disappeared and a broad peak corresponding to graphene appeared at 25.2°. This indicates that GO was successfully reduced to rGO. In silicon (Si), characteristic peaks of crystalline silicon were observed at 28.4°Si(111), 47.3°Si(220), 56.1°Si(311), 69.1°Si(400), and 76.4°Si(331). These strong and narrow characteristic peaks and the peak at 25.2° also appeared in the SiNPs/rGO composite film, confirming the presence of Si and rGO. The carbon nanotube (CNT) has characteristic peaks at 43°, 53° and 78°, including the graphite peak corresponding to the crystal plane (002), showing a typical multi-walled carbon nanotube (MWCNT) peak. In SiNPs/CNT/rGO, amorphous carbon characteristic peak, crystalline silicon peak, and carbon nanotube peak all appeared and remained unchanged even after the reaction, indicating that the SiNPs/CNT/rGO composite film was well synthesized.

Figure 8b shows the Raman spectra of SiNPs/CNT/rGO, SiNPs/rGO, rGO and GO.

Referring to FIG. 8b , a peak of silicon appeared at about 514 cm ⁻¹ in the SiNPs/CNT/rGO and SiNPs/rGO composite films, indicating that silicon did not change after the composite was formed. In the SiNPs/CNT/rGO composite film, the G band due to sp ² bonding of carbon was found at 1,590 cm ^-1 , and the D band due to intra-crystal defects was revealed at 1,352 cm ^-1 . G band and D band are characteristic peaks of carbon materials, and the relative intensity ratio (ID/IG) of the peaks decreased from 1.06 to 0.95 after GO was reduced to rGO. This is because the sp2 region increased after reduction. For the same reason, when comparing SiNPs/rGO (1.13) and SiNPs/CNT/rGO (1.01), it can be seen that the strength ratio decreased after adding carbon nanotubes. This is because the bond of the carbon nanotube consists of an sp ² bond, so that the G band is significantly increased by the introduction of the carbon nanotube, and the strength of the D band decreases as the degree of carbonization increases.

To find out the chemical composition and binding energy of the complex, the samples were analyzed by XPS and shown in Figure 6. 9a to 9d are C 1s XPS spectra of composite SiNPs/GO, SiNPs/rGO, SiNPs/CNT/GO and SiNPs/CNT/rGO.

9A to 9D, the strong peaks of 284 eV and 286 eV, which appear in common, are C=C and C-O bonds, respectively, and the weak peaks at 287 eV and 289 eV are C=O bonds and O-C=O bonds, respectively. corresponds to Overall, the intensity of the C=O bond peak is stronger than that of the O-C=O bond.

When comparing Figures 9a and 9b, the C-O bond peak is significantly weakened due to the loss of oxygen after reduction. For the same reason, when comparing FIGS. 9c and 9d, the intensity of the peaks for the C-O, C=O, and O-C=O bonds of FIG. 9d decreased.

Referring to FIG. 9c , after adding the carbon nanotubes, a peak corresponding to the sp ³ bond at 285.87 eV and a peak corresponding to the π-π bond at 290.68 eV were additionally appeared.

In FIG. 9d , the intensity of the carbon peak corresponding to sp ³ was strengthened as rGO and CNT were CC-bonded due to the reduction of GO and CNT.

9e shows the Si 2p spectrum of the SiNPs/CNT/rGO composite film, in which three peaks are observed. Referring to FIG. 9E , Si 2p 3/2 and Si 2p 1/2 peaks were shown at 99.98 eV and 101.44 eV, respectively, and Si-O bonding peaks were shown at 104.01 eV. This is a peak that appears when a small amount of silicon nanoparticles is oxidized in air during the composite synthesis process.

10 is 0.01-15 V (vs. Li/Li ⁺ ) to investigate the electrochemical properties of a coin cell battery assembled by applying the SiNPs/CNT/rGO composite film synthesized in the present invention as a negative electrode material for a lithium secondary battery. This is a cyclic voltammogram showing the first cycle and the fifth cycle measured at 0.1 mV/s in the voltage range of . In FIG. 10, the cell was compared to prepare a film by adjusting the volume of the dispersion solution to 20 mL (refer to FIG. 10a), 25 mL (refer to FIG. 10b) and 30 mL (refer to FIG. 10c) during the vacuum filtering process.

First, it can be seen that a broad and weak peak of 1.3 V appears in the first cycle of FIG.

The strong reduction peak near 0.5 V in FIGS. 10b and 10c means that amorphous silicon is alloyed with lithium as LixSi in a reversible lithium intercalation reaction. Oxidation peaks near 0.3 V and 0.5 V appearing during discharge indicate a reverse reaction in which silicon is produced as lithium is desorbed from LixSi. Also, as the cycle progresses, the oxidation peak becomes stronger, and lithium ions diffuse into silicon to activate the electrode. was known to have been

The cycle performance and Nyquist plots for each thickness of the SiNPs/CNT/rGO composite film were shown in FIG. 11 at current density and voltage range of 0.1 A/g and 0.01-1.5 V. When the discharge capacity of the three composite films was measured up to 30 cycles, the capacity of the first cycle was highest in the order of 20 mL, 25 mL, and 30 mL. In the case of 20 mL, capacity loss occurred rapidly after the 4th cycle, and the lowest capacity among the three films was maintained after 30 cycles. 25 mL showed the most stable cycle performance, and the capacity after 30 cycles was 198 mAh/g, maintaining the highest capacity. Although 30 mL had the lowest initial capacity, it showed a higher capacity than 20 mL from the 16th cycle. Table 2 shows the initial capacity of each electrode and the capacity after 30 cycles.

20ml 25ml 30ml Initial discharge capacity (mAh/g) 1712 1336 796 Discharge capacity after 30 cycles (mAh/g) 71 198 115

It is thought that carbon nanotubes act as a cross-linker in the three-dimensional structure of silicon nanoparticles and graphene, thereby preventing graphene desorption occurring in the process of changing the volume of silicon and improving conductivity, thereby exhibiting high capacity and stable cycle performance. And this structure provides an efficient channel for the rapid transport of electrons and ions.

The coulombic efficiency of a battery indicates the percentage of the discharge capacity with respect to the amount of electricity charged during charging when the battery is discharged after being charged, and is also called charge/discharge efficiency. If the coulombic efficiency is high, most of the charged electricity can be discharged, which is a good battery. Looking at the coulombic efficiency of each electrode, all three electrodes show over 99% coulombic efficiency up to 30 cycles.

To further analyze the electrochemical performance of SiNPs/CNT/rGO composite films, electrochemical impedance spectroscopy was performed. The Nyquist curve contains a semicircle in the high-frequency region and region, and a sloped line in the low-frequency region. The semicircle represents the charge transfer resistance and the slanted line represents the ion diffusion resistance. 11c and 11d show Nyquist plots before and after cycles of SiNPs/CNT/rGO-20 mL, 25 mL and 30 mL. Before the cell operation, the charge transfer resistance of the SiNPs/CNT/rGO-25 mL composite film was the lowest among the three electrodes, and the SiNPs/CNT/rGO-30 mL composite film had the lowest after cycling. This is determined by the diameter of the semicircle, and the smaller the diameter, the better the electrochemical performance of the electrode by effectively transferring electrons and charges.

4. Conclusion

In the present invention, binder-free SiNPs/rGO and SiNPs/CNT/rGO composite films were synthesized by simple physical mixing and thermal reduction.

First, through SEM and TEM analysis, a three-dimensional structure in which silicon, carbon nanotubes, and reduced graphene oxide were uniformly dispersed could be seen. An additional peak appeared, proving the existence of carbon nanotubes. At this time, carbon nanotubes provide efficient channels for electron and ion transport through the three-dimensional structure of the reduced graphene oxide and silicon nanoparticles in the SiNPs/CNT/rGO composite film, and maintain a stable structure of the electrode. gave. In addition, the three-dimensional three-dimensional structure prevents direct contact between the electrolyte and silicon to form a stable SEI layer. In addition, rGO not only increases the conductivity of the electrode in the composite, but also acts as a matrix to buffer the volume change of silicon, thereby preventing the indiscriminate pulverization of silicon nanoparticles during the cycle.

Then, when the electrochemical performance was investigated by controlling the film thickness for each volume of the complex solution, the initial discharge capacity was the highest in the order of 20 mL, 25 mL, and 30 mL.

The results of the present invention are expected to be expandable even in the case of other anode materials having a large volume change during charging and discharging in a lithium ion battery.

As described above, the technical ideas described in the embodiments of the present invention may be implemented independently, or may be implemented in combination with each other. In addition, although the present invention has been described through the embodiments described in the drawings and detailed description of the invention, these are merely exemplary, and those of ordinary skill in the art to which the present invention pertains may make various modifications and equivalent other embodiments therefrom. It is possible. Accordingly, the technical protection scope of the present invention should be defined by the appended claims.

Claims (15)

(a) preparing a SiNPs/CNT mixed solution by adding predetermined silicon nanoparticles and carbon nanotube powder to ethanol, stirring the mixture, and sonicating the mixture for a predetermined time;
(b) preparing a SiNPs/CNT/GO dispersion by adding an aqueous GO solution to the SiNPs/CNT mixed solution prepared in step (a), sonicating the resulting mixture and stirring for a predetermined time;
(c) filtering and drying the SiNPs/CNT/GO dispersion to prepare a SiNPs/CNT/GO composite film; and
(d) a silicon/carbon nanotube/graphene composite manufacturing method comprising the step of preparing a thermally reduced SiNPs/CNT/rGO composite film through a heat treatment process. According to claim 1,
In the step (a), the silicon nanoparticles and the carbon nanotube powder is a silicon/carbon nanotube/graphene composite manufacturing method, characterized in that it is added in a mass ratio of 1: 1. According to claim 1,
In the step (b), the silicon/carbon nanotube/graphene composite manufacturing method, characterized in that it is added in a volume ratio of 7.5% to 12.5% compared to the SiNPs/CNT mixed solution prepared in step (a). According to claim 1,
In the step (c), the silicon/carbon nanotube/graphene composite manufacturing method, characterized in that the SiNPs/CNT/GO dispersion is vacuum filtered using a PTFE filter. According to claim 1,
In the step (c), silicon/carbon nanotube/graphene, characterized in that the thickness of the SiNPs/CNT/GO composite film is controlled by adjusting the volume of the dispersion during the filtering process of the SiNPs/CNT/GO dispersion. Composite manufacturing method. According to claim 1,
In step (d),
In the heat treatment process, the SiNPs/CNT/GO composite film is placed in a quartz tube, the temperature is raised to a maximum of 550° C., and Ar gas is flowed thereto to prepare a thermally reduced SiNPs/CNT/rGO composite film. A method for manufacturing a tube/graphene composite. (a) preparing a SiNPs/CNT mixed solution by adding predetermined silicon nanoparticles and carbon nanotube powder to ethanol, stirring the mixture, and sonicating the mixture for a predetermined time;
(b) preparing a SiNPs/CNT/GO dispersion by adding an aqueous GO solution to the SiNPs/CNT mixed solution prepared in step (a), sonicating the resulting mixture and stirring for a predetermined time;
(c) filtering and drying the SiNPs/CNT/GO dispersion to prepare a SiNPs/CNT/GO composite film;
(d) preparing a thermally reduced SiNPs/CNT/rGO composite film through a heat treatment process; and
(e) using the SiNPs/CNT/rGO composite film as an anode material to prepare a secondary battery. 8. The method of claim 7,
The electrolyte in step (e) is,
A method for manufacturing a secondary battery, characterized in that it is formed by dissolving 1M LiPF ₆ in a solution of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) in a 1:1:1 volume ratio. 8. The method of claim 7,
A method for manufacturing a secondary battery, characterized in that the working electrode uses the SiNPs/CNT/rGO composite film without using conductive additives and binders, and Li metal is used as a counter electrode and a reference electrode. 8. The method of claim 7,
In the step (a), the silicon nanoparticles and the carbon nanotube powder is a secondary battery manufacturing method, characterized in that it is added in a mass ratio of 1: 1. 8. The method of claim 7,
In step (b), compared to the SiNPs/CNT mixed solution prepared in step (a), the secondary battery manufacturing method characterized in that it is added in the range of 7.5% to 12.5% by volume. 8. The method of claim 7,
In the step (c), the secondary battery manufacturing method, characterized in that the SiNPs / CNT / GO dispersion is vacuum filtered using a PTFE filter. 8. The method of claim 7,
In the step (c), the thickness of the SiNPs/CNT/GO composite film is controlled by adjusting the volume of the dispersion during the filtering process of the SiNPs/CNT/GO dispersion. 14. The method of claim 13,
A secondary battery manufacturing method, characterized in that by adding the SiNPs / CNT / GO dispersion in the range of 20 ~ 30ml to control the discharge capacity. 8. The method of claim 7,
In step (e),
In the heat treatment process, the SiNPs/CNT/GO composite film is placed in a quartz tube, and the temperature is raised to a maximum of 550° C. .

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