Silicon-based anode active material, and anode and lithium ion battery comprising same

Abstract

The present invention relates to a silicon-based anode active material capable of improving the charging rate and lifespan characteristics of a lithium secondary battery, and an anode and a lithium ion battery comprising same. The silicon-based anode active material for a lithium secondary battery, according to the present invention, comprises: a silicon-based material in a powder form; and iodine adsorbed on the silicon-based material. Iodine included in a silicon-based anode active material allows an iodine-based solid electrolyte interphase (SEI) to be formed on the surface of the anode so as to stabilize interface properties of the SEI.

Description

Silicon-based negative electrode active material, negative electrode containing the same, and lithium-ion battery

[0001] The present invention relates to a lithium secondary battery, and more particularly, to a silicon-based negative electrode active material capable of improving the charging speed and lifespan characteristics of a lithium secondary battery, a negative electrode including the same, and a lithium ion battery.

[0002] To achieve high energy density (over 280 Wh / kg) and rapid charging (around 20 minutes), lithium-ion batteries utilize silicon-based active materials mixed with graphite in their negative electrode plates. In some cases, graphite / silicon composite electrodes utilize electrode slurry coating in a magnetic field to improve electrode curvature and enhance the battery's charging speed and other charge-discharge performance.

[0003] However, silicon within the cathode causes volume changes and interface degradation, which can negatively impact the lifespan of lithium-ion batteries. Consequently, lithium secondary batteries using conventional silicon-based cathode active materials fall short of market demands in terms of energy density and charging speed.

[0004] Therefore, the development of materials and battery technologies that can simultaneously improve both rapid charging and cycle life is essential. Furthermore, the temperature rise that accompanies rapid charging can rapidly deteriorate battery cycle life. Therefore, materials that can mitigate this deterioration, particularly the stabilization of the interfacial properties of the solid electrolyte interphase (SEI), are considered key technologies.

[0005] [Prior Art Literature]

[0006] [Patent Document]

[0007] Patent Publication No. 2024-0097284 (June 27, 2024)

[0008] Accordingly, the purpose of the present invention is to provide a silicon-based negative electrode active material capable of improving the charging speed and life characteristics of a lithium secondary battery, and a negative electrode and a lithium ion battery including the same.

[0009] Meanwhile, the purpose of the present invention is not limited to the above purpose, and other purposes not mentioned can be clearly understood from the description below.

[0010] To achieve the above object, the present invention provides a silicon-based negative electrode active material for a lithium secondary battery, comprising: a silicon-based material in powder form; and iodine adsorbed on the silicon-based material.

[0011] The above iodine is less than 5 wt%.

[0012] The above silicon-based material may include at least one of carbon-coated SiO, a Si / C composite, carbon-coated Si, and an alloy including Si.

[0013] The above negative active material exhibited I3 in the range of 615 to 635 eV when analyzed by XPS. - and I5 - It shows the iodine peak corresponding to .

[0014] The above negative active material has a Raman spectroscopy analysis of 100 to 180 cm -1 In I3 - and I5 - It shows the iodine peak corresponding to .

[0015] The present invention also provides a negative electrode for a lithium secondary battery containing the silicon negative electrode active material.

[0016] The above cathode may further include a conductive material; and a binder.

[0017] The above-mentioned challenge material may include graphite.

[0018] The present invention also provides a lithium secondary battery including a positive electrode; an electrolyte; and a negative electrode containing the silicon negative electrode active material.

[0019] A solid electrolyte interphase (SEI) containing an iodrite compound is formed on the surface of the cathode.

[0020] And the above lithium iodide compound includes LiI.

[0021] According to the present invention, by manufacturing an anode using a silicon-based anode active material having iodine adsorbed therein, the SEI induced at the interface of the anode during initial charge / discharge is formed based on iodine, thereby stabilizing the interfacial characteristics of the SEI. Accordingly, by applying the silicon-based anode active material having iodine adsorbed therein according to the present invention to a lithium secondary battery, the charging speed and life characteristics of the lithium secondary battery can be improved.

[0022] Meanwhile, the effects of the present invention are not limited to the effects described above, and other effects not mentioned may be disclosed directly or implicitly in the detailed description according to the embodiments of the present invention to be described later.

[0023] Figure 1 is a flow chart showing a method for manufacturing a silicon-based negative electrode active material for lithium secondary batteries according to the present invention.

[0024] Figure 2 is a graph showing the results of XPS (X-ray photoelectron spectroscopy) analysis of a silicon-based negative electrode active material according to Example 1.

[0025] Figure 3 is a graph showing the results of Raman spectroscopy analysis of a silicon-based negative electrode active material according to Example 1.

[0026] Figure 4 is a graph showing the results of SEM (Scanning Electron Microscope)-EDS (Energy Dispersive Spectrometer) analysis of a silicon-based negative electrode active material according to Example 1.

[0027] Figure 5 is a graph showing the SEI and charge transfer resistance measured by the electrochemical impedance measurement method of a half cell using a silicon-based negative electrode active material according to Example 1 and Comparative Example 1.

[0028] Figure 6 is a graph showing the measurement results evaluating the high current charging performance of a full cell using a silicon-based negative electrode active material according to Example 1 and Comparative Example 1.

[0029] Figure 7 is a graph showing the life characteristics of a full cell using a silicon-based negative electrode active material according to Example 1 and Comparative Example 1 under a 1C charging current condition.

[0030] Figure 8 is a graph showing the life characteristics of a full cell using a silicon-based negative electrode active material according to Example 1 and Comparative Example 1 under a 5C charging current condition.

[0031] Figure 9 is a graph showing the XPS analysis results of the negative electrode surface after charge and discharge of a full cell using a silicon-based negative electrode active material according to Example 1 and Comparative Example 1.

[0032] It should be noted that in the following description, only the parts necessary for understanding the embodiments of the present invention are described, and the description of other parts will be omitted to the extent that it does not deviate from the gist of the present invention.

[0033] The terms and words used in this specification and claims described below should not be interpreted as limited to their conventional or dictionary meanings, but should be interpreted with meanings and concepts that conform to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term in order to explain his own invention in the best way. Therefore, it should be understood that the embodiments described in this specification and the configurations illustrated in the drawings are merely preferred embodiments of the present invention and do not represent all of the technical idea of ​​the present invention, and that there may be various equivalents and modified examples that can replace them at the time of this application.

[0034] Hereinafter, embodiments of the present invention will be described in more detail with reference to the attached drawings.

[0035] A silicon-based negative electrode active material for a lithium secondary battery according to the present invention includes a silicon material in powder form and iodine adsorbed on the silicon material.

[0036] Here, the silicon material includes at least one of carbon-coated SiO, a Si / C composite, carbon-coated Si, and an alloy including Si.

[0037] And iodine is adsorbed onto the surface of the silicon material. Following the silicon-based negative electrode active material according to the present invention, the iodine content is 5 wt% or less. If the iodine content exceeds 5 wt%, the adsorption of iodine onto the surface of the silicon material may decrease, thereby reducing the effectiveness of iodine adsorption.

[0038] The silicon-based negative electrode active material according to the present invention can be manufactured as shown in Fig. 1. Fig. 1 is a flow chart showing a method for manufacturing a silicon-based negative electrode active material for lithium secondary batteries according to the present invention.

[0039] First, prepare a silicon-based material in powder form at step S10.

[0040] Next, in step S20, the silicon-based material is immersed in an iodine solution. The iodine solution can be an ethanol solution containing dissolved iodine. The iodine solution contains 1 to 10 wt% iodine. The immersion time is 1 to 12 hours at room temperature. The immersion time may increase or decrease depending on the temperature of the iodine solution.

[0041] In step S30, a silicon-based material having iodine adsorbed thereon is obtained from an iodine solution and dried, thereby manufacturing a silicon-based negative electrode active material according to the present invention. The drying process can be performed at a temperature of 200°C or lower for at least one hour.

[0042] The amount of iodine adsorbed onto the silicone material is determined by at least one of the concentration of the ethanol solution and the drying time. For example, the amount of iodine can be controlled by the concentration of the ethanol solution.

[0043] The silicon-based negative electrode active material according to the present invention has a structure in which iodine is adsorbed onto a silicon-based material. Here, iodine is coated onto the surface of the silicon-based material, and is uniformly coated throughout the entire surface of the silicon-based material. Iodine forms a coating layer on the surface of the silicon-based material. The coating layer may be formed continuously or discontinuously on the surface of the silicon-based material, depending on the iodine content.

[0044] Meanwhile, the method of manufacturing a silicon-based negative electrode active material according to the present invention has been exemplified by a method of immersing a silicon-based material in an iodine solution, but is not limited thereto. For example, iodine can be adsorbed onto the silicon-based material by spraying an iodine solution onto the silicon-based material.

[0045] Since the silicon-based negative electrode active material according to the present invention contains iodine, it exhibits peaks in the range of 615 to 635 eV when analyzed by XPS (X-ray photoelectron spectroscopy). Specifically, the peaks at 619 eV and 631 eV are I3 - It is a chemical adsorption component of the form, and the peaks at 621 eV and 633 eV are I5 - It is a chemical adsorption component in the form of a compound.

[0046] Since the silicon-based negative electrode active material according to the present invention contains iodine, it has a Raman spectroscopy analysis of 100 to 180 cm -1 Adsorbed iodine is confirmed at 118 cm -1 and 143 cm -1 The area is I3 - It is a chemical adsorption component of the form, 166 cm -1 The area is I5 - It is a chemical adsorption component in the form of a compound.

[0047] The present invention provides a negative electrode for a lithium secondary battery containing a silicon negative electrode active material. The negative electrode according to the present invention includes a conductive material and a binder.

[0048] Conductive materials increase the overall conductivity of silicon-based negative active materials and improve the output characteristics of batteries. Any conductive material with excellent electrical conductivity and that does not cause side reactions in the internal environment of a lithium secondary battery can be used without particular restrictions. Preferably, the conductive material is a highly conductive carbon-based material, such as graphite, graphene, carbon nanotubes, carbon nanofibers, or conductive carbon. Highly conductive polymers can also be used as the conductive material. Specifically, the graphite is not limited to natural graphite or artificial graphite. The conductive carbon is preferably a highly conductive carbon-based material. Examples of the conductive carbon include carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; or a mixture of one or more materials with a crystal structure that includes graphene or graphite. Furthermore, any conductive precursor that can be converted into a conductive material during a relatively low-temperature sintering process in an oxygen-containing atmosphere, such as air, can be used without particular restrictions. The method of including a challenger is also not particularly limited, and a conventional method known in the art, such as coating of a negative electrode active material, can be adopted.

[0049] Any binder material used for lithium secondary battery electrodes may be used without restriction. For example, binders such as polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, and vinylidene fluoride / hexafluoropropylene copolymer may be used singly or in combination.

[0050] A solvent is used in the process of manufacturing the cathode according to the present invention. The solvent may be at least one selected from the group consisting of distilled water, ethylene glycol, diethylene glycol, triethylene glycol, dimethyl sulfoxide, dimethyl formide, ethanol, propanol, butanol, pentanol, hexanol, N-methyl-2-pyrrolidone, and acetone, but is not limited thereto.

[0051] A lithium secondary battery using the anode according to the present invention may further include a cathode, a separator, and an electrolyte. Since the cathode, separator, and electrolyte used in the lithium secondary battery according to the present invention can be made of common materials, a detailed description thereof will be omitted.

[0052] In the lithium secondary battery according to the present invention, a SEI is formed on the surface of the negative electrode during the initial charge / discharge process. The SEI includes an iodine-based lithium iodide compound in a silicon-based negative electrode active material. The iodine iodide compound includes LiI.

[0053] The lithium iodide compound contained in the SEI stabilizes the interfacial properties of the SEI. Therefore, by applying the iodine-adsorbed silicon-based negative electrode active material according to the present invention to a lithium secondary battery, the charging speed and lifespan characteristics of the lithium secondary battery can be improved.

[0054]

[0055] [Examples and Comparative Examples]

[0056] In order to confirm the charging characteristics and life characteristics of the silicon-based negative electrode active material according to the present invention, a silicon-based negative electrode active material according to Example 1 was manufactured.

[0057] The silicon-based negative electrode active material according to Example 1 was manufactured as follows.

[0058] First, carbon-coated SiO powder was used as a silicon-based material. Next, the silicon-based material was immersed in a 13 wt% iodine solution for 4 hours. Then, an iodine-adsorbed silicon-based material was obtained from the iodine solution and vacuum-dried at 140°C for 4 hours to produce a silicon-based negative electrode active material according to Example 1.

[0059] As a silicon-based negative electrode active material according to Comparative Example 1, SiO powder coated with carbon that does not adsorb iodine was used. That is, in Comparative Example 1, the silicon-based material itself was used as the silicon-based negative electrode active material.

[0060] In order to confirm whether iodine was included in the silicon-based negative electrode active material according to Example 1, XPS analysis and Raman spectroscopy analysis were performed on the silicon-based negative electrode active material according to Example 1, respectively. The XPS analysis result is shown in Fig. 2, and the Raman spectroscopy analysis result is shown in Fig. 3. Here, Fig. 2 is a graph showing the XPS analysis result of the silicon-based negative electrode active material according to Example 1. And Fig. 3 is a graph showing the Raman spectroscopy analysis result of the silicon-based negative electrode active material according to Example 1.

[0061] Referring to Fig. 2, according to the XPS analysis results for the silicon-based negative electrode active material according to Example 1, two peaks were observed in the regions of 615–625 eV and 627–635 eV. The two observed peaks are binding energies corresponding to iodine. Specifically, the peaks at 619 eV and 631 eV correspond to I3. - It is a chemical adsorption component of the form, and the peaks at 621 eV and 633 eV are I5 - It is a chemical adsorption component in the form of a compound.

[0062] That is, the XPS analysis results indicate that the silicon-based negative electrode active material according to Example 1 contains iodine.

[0063] Referring to Figure 3, according to the Raman spectroscopy analysis results for the silicon-based negative electrode active material according to Example 1, 100 to 180 cm -1Adsorbed iodine is confirmed at 118 cm -1 and 143 cm -1 The area is I3 - It is a chemical adsorption component of the form, 166 cm -1 The area is I5 - It is a chemical adsorption component in the form of a compound.

[0064] That is, the Raman spectroscopy analysis results indicate that the silicon-based negative electrode active material according to Example 1 contains iodine.

[0065] Thus, the XPS and Raman spectroscopy analysis results indicate that the silicon-based negative electrode active material according to Example 1 contains iodine.

[0066]

[0067] In order to confirm whether iodine was adsorbed on the silicon-based material of the silicon-based negative electrode active material according to Example 1, SEM (Scanning Electron Microscope)-EDS (Energy Dispersive Spectrometer) analysis was performed on the silicon-based negative electrode active material according to Example 1, and the SEM-EDS analysis results are as shown in Fig. 4. Here, Fig. 4 is a graph showing the SEM-EDS analysis results of the silicon-based negative electrode active material according to Example 1. The scale bar in Fig. 4 is 2 μm.

[0068] Referring to FIG. 4, according to the SEM-EDS analysis results for the silicon-based negative electrode active material according to Example 1, an iodine component was observed on the surface of the silicon-based material, and its content was confirmed to be approximately 1 wt%.

[0069]

[0070] The negative electrodes according to Example 1 and Comparative Example 1 were manufactured using the silicon-based negative electrode active material according to Example 1 and Comparative Example 1, respectively. That is, the negative electrodes were manufactured by mixing the silicon-based negative electrode active material, graphite, and binder in a weight ratio of 6:3:1.

[0071] In order to confirm the charging characteristics of a lithium secondary battery using the negative electrode according to Example 1 and Comparative Example 1, a half cell was manufactured, and then the SEI and the resistance (impedance) of charge transfer were measured using an electrochemical impedance measurement method, and the measurement results are as shown in Fig. 5. Here, Fig. 5 is a graph showing the SEI and the resistance of charge transfer measured using an electrochemical impedance measurement method of a half-cell battery using a silicon-based negative electrode active material according to Example 1 and Comparative Example 1.

[0072] Referring to Fig. 5, the measurement results are shown as a graph of a Nyquist plot, and show two semicircular impedance behaviors of SEI resistance in the high-frequency region and charge transfer resistance in the low-frequency region. In this case, in the case of the cathode according to Comparative Example 1, the SEI resistance is 102 Ohm and the charge transfer resistance is 73 Ohm. On the other hand, in the case of the cathode according to Example 1, the SEI resistance is 62 Ohm and the charge transfer resistance is 41 Ohm, and when iodine is coated, it can be confirmed that the resistance is reduced by less than half.

[0073] In the case of the cathode according to Example 1, it can be judged that the reaction resistance at the SEI interface is reduced due to iodine adsorption on the surface.

[0074] The decrease in reaction resistance at the SEI interface of the negative electrode according to Example 1 can be confirmed in Fig. 6, and an improvement in the charge / discharge characteristics of the lithium secondary battery according to Example 1 can be expected.

[0075]

[0076] A pouch-type full cell was manufactured using the negative electrode according to Example 1 and Comparative Example 1, and its performance was confirmed. In the full cell, NCM811 was used as the positive electrode, NP was 1.2, and the current per area was 4 mAh / cm 2 am.

[0077] In order to check the charging speed of the full cell according to Example 1 and Comparative Example 1, 10 C (40 mA / cm 2) was evaluated for charging performance at a high charging current, and the evaluation results are as shown in Fig. 6. Fig. 6 is a graph showing the measurement results evaluating the high-current charging performance of a full cell using a silicon-based negative electrode active material according to Example 1 and Comparative Example 1.

[0078] Referring to Fig. 6, in the case of Comparative Example 1, it took about 9.3 minutes to charge 80% of the total capacity of the full cell. On the other hand, in the case of Example 1, it took about 6.3 minutes to charge 80% of the total capacity of the full cell.

[0079] Therefore, it can be confirmed that Example 1 exhibits improved rapid charging performance compared to Comparative Example 1.

[0080]

[0081] The life characteristics of the full cells according to Example 1 and Comparative Example 1 were evaluated, and the evaluation results are as shown in FIGS. 7 and 8. FIG. 7 is a graph showing the life characteristics of the full cells using the silicon-based negative electrode active material according to Example 1 and Comparative Example 1 under 1 C charging current conditions. And FIG. 8 is a graph showing the life characteristics of the full cells using the silicon-based negative electrode active material according to Example 1 and Comparative Example 1 under 5 C charging current conditions.

[0082] Referring to Fig. 7, the life characteristics under a 1 C charging current condition for the full cells according to Example 1 and Comparative Example 1 are shown. It can be confirmed that Example 1 has a life characteristic that is superior to that of Comparative Example 1.

[0083] Referring to Fig. 8, the life characteristics under a 5 C charging current condition for the full cells according to Example 1 and Comparative Example 1 are shown. Even under a 5 C charging current condition, which is higher than a 1 C charging current, it can be confirmed that Example 1 has better life characteristics than Comparative Example 1.

[0084] It is believed that the improvement in charging speed and life characteristics of Example 1 compared to Comparative Example 1 is due to the effect of reducing the interfacial resistance of SEI. That is, the full cell according to Example 1 forms a SEI containing a lithium iodide compound (LiI) on the negative electrode surface when iodine adsorbed on the surface of the silicon material is charged and discharged, thereby forming a relatively stable surface film compared to the SEI in which a lithium iodide compound (LiI) is not formed, as in Comparative Example 1.

[0085] In order to confirm whether an SEI containing iodine was formed on the negative electrode surface after charge and discharge of the full cell according to Example 1, XPS analysis was performed on the negative electrode surface of the full cell that had been charged and discharged, and the analysis results are as shown in Fig. 9. Here, Fig. 9 is a graph showing the XPS analysis results of the negative electrode surface after charge and discharge of the full cell using the silicon-based negative electrode active material according to Example 1 and Comparative Example 1.

[0086] Referring to Figure 9, on the cathode surface of Comparative Example 1, 33 wt% of ROCO2Li component is confirmed as an organic component, and no iodine component is confirmed.

[0087] On the other hand, an iodine component is confirmed on the cathode surface of Example 1. That is, according to the XPS analysis results for the cathode surface of Example 1, a lithium iodide compound (LiI) having peaks at 619 eV and 630 eV is confirmed, and the ROCO2Li component is confirmed to be 13 wt%.

[0088] As such, it can be confirmed that the organic SEI component of Example 1 is reduced compared to Comparative Example 1, and instead, the inorganic SEI component including lithium iodide compound (LiI) is developed. This is believed to provide improved life characteristics of the battery by forming an inorganic SEI component including lithium iodide compound (LiI) with high ionic conductivity and chemical stability under high current conditions on the surface of the negative electrode according to Example 1.

[0089] Meanwhile, the embodiments disclosed in this specification and drawings are merely specific examples to aid understanding and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical concepts of the present invention are possible in addition to the embodiments disclosed herein.

Claims

1. Silicon-based material in powder form; and Iodine adsorbed on the above silicon-based material; A silicon-based negative electrode active material for a lithium secondary battery.

2. In paragraph 1, A silicon-based negative electrode active material for lithium secondary batteries, characterized in that the above iodine is 5 wt% or less.

3. In paragraph 2, A silicon-based negative electrode active material for lithium secondary batteries, characterized in that the silicon-based material comprises at least one of carbon-coated SiO, a Si / C composite, carbon-coated Si, and an alloy containing Si.

4. In paragraph 1, The above negative active material exhibited I3 in the range of 615 to 635 eV when analyzed by XPS. - and I5 - A silicon-based negative electrode active material for lithium secondary batteries, characterized by exhibiting an iodine peak corresponding to .

5. In paragraph 1, The above negative active material has a Raman spectroscopy analysis of 100 to 180 cm -1 In I3 - and I5 - A silicon-based negative electrode active material for lithium secondary batteries, characterized by exhibiting an iodine peak corresponding to .

6. A negative electrode for a lithium secondary battery containing a silicon negative electrode active material, The above silicon-based negative electrode active material is, Silicon-based material in powder form; and Iodine adsorbed on the above silicon-based material; A negative electrode for a lithium secondary battery comprising:

7. In paragraph 6, the cathode is Challenge; and bookbinder; A silicon-based negative electrode for lithium secondary batteries, characterized by further comprising:

8. In paragraph 7, A silicon-based negative electrode for lithium secondary batteries, characterized in that the above-mentioned conductive material comprises graphite.

9. A cathode comprising a positive electrode; an electrolyte; and a negative electrode containing a silicon negative electrode active material; The above silicon-based negative electrode active material is, Silicon-based material in powder form; and Iodine adsorbed on the above silicon-based material; A lithium secondary battery comprising:

10. In paragraph 9, A lithium secondary battery characterized in that a solid electrolyte interphase (SEI) containing a lithium iodide compound is formed on the surface of the negative electrode.

11. In paragraph 10, A lithium secondary battery characterized in that the above lithium iodide compound contains LiI.

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