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KR-20260065119-A - Negative electrode active material for secondary battery, method for preparing the same and lithium secondary battery including the same

KR20260065119AKR 20260065119 AKR20260065119 AKR 20260065119AKR-20260065119-A

Abstract

One embodiment of the present invention provides a negative electrode active material for a secondary battery comprising a silicon-based composite comprising a first compound (Li-Si-N) containing at least lithium, silicon, and nitrogen; and/or a second compound (Li-Si-O) containing at least lithium, silicon, and oxygen; and silicon nitride (SiNx, 0<x≤2); and/or silicon oxide (SiOy, 0<y≤2); wherein the peak area ratio A/B according to X-ray diffraction analysis is 0.1 to 9.

Inventors

  • 전민영
  • 이총민
  • 채태성
  • 서유경
  • 이동욱

Assignees

  • 주식회사 에코프로비엠

Dates

Publication Date
20260508
Application Date
20241031

Claims (16)

  1. A first compound (Li-Si-N) containing at least lithium, silicon, and nitrogen; and/or a second compound (Li-Si-O) containing at least lithium, silicon, and oxygen; and A silicon-based composite comprising silicon nitride (SiNx, 0<x≤2); and/or silicon oxide (SiOy, 0<y≤2); and A negative electrode active material for a secondary battery having a peak area ratio A/B of 0.1 to 9 according to X-ray diffraction analysis. (A above is the total peak area of the first and second compounds in X-ray diffraction analysis, and B is the total peak area of the silicon nitride (SiNx) and silicon oxide (SiOy) in X-ray diffraction analysis)
  2. In paragraph 1, A negative electrode active material for a secondary battery having a peak area ratio C/D of less than 0.5 as determined by X-ray diffraction analysis. (C above is the peak area of a third compound (Li-Si) composed of lithium and silicon in X-ray diffraction analysis, and D above is the peak area of silicon (Si) in X-ray diffraction analysis)
  3. In paragraph 1, A negative electrode active material for a secondary battery having a peak area ratio C/A of 0.1 to 3 according to X-ray diffraction analysis. (A above is the total peak area of the first and second compounds in X-ray diffraction analysis, and C is the peak area of the third compound (Li-Si) composed of lithium and silicon in X-ray diffraction analysis)
  4. In paragraph 1, A negative electrode active material for a secondary battery, wherein, based on the total weight of the negative electrode active material, the nitrogen (N) content is 10 weight% or less and the weight ratio of lithium to nitrogen Li/N is 0.1 to 10.
  5. In paragraph 2, The above first, second, and third compounds are negative electrode active materials for secondary batteries, each represented by the following chemical formulas 1, 2, and 3: [Chemical Formula 1] Li x1 Si y1 N z1 In the above chemical formula 1, 1≤x1≤3, 1≤y1≤3 and 1≤z1≤3, [Chemical Formula 2] Li x2 Si y2 O z2 In the above chemical formula 2, 1≤x2≤6, 1≤y2≤3 and 1≤z2≤7, [Chemical Formula 3] Li x3 Si y3 In the above chemical formula 3, 2≤x3≤6 and 1≤y3≤3.
  6. In paragraph 1, The above silicon-based composite comprises silicon particles; and a coating layer formed on at least a portion of the silicon particles. The coating layer comprises at least one selected from the group consisting of the first compound (Li-Si-N) and the second compound (Li-Si-O); and A negative electrode active material for a secondary battery, comprising: at least one selected from the group consisting of the coating layer, silicon nitride (SiNx, 1≤x<4) and silicon oxide (SiOy, 0<y≤2).
  7. In paragraph 6, A negative electrode active material for a secondary battery, wherein at least one of the lithium (Li), silicon (Si), oxygen (O), and nitrogen (N) has a concentration gradient in the direction from the surface of the composite particle toward the center in at least a portion of the silicon-based composite.
  8. In paragraph 6, At least one of the lithium (Li), oxygen (O), and nitrogen (N) has a concentration gradient that decreases in the direction from the surface of the composite particle toward the center in at least a portion of the silicon-based composite, and The above silicon (Si) is a negative electrode active material for a secondary battery, having a concentration gradient that increases from the surface portion of the composite particle toward the center in at least a portion of the silicon-based composite.
  9. In paragraph 6, The above silicon-based composite has an average particle size (D50) of 10 to 800 nm, and The above coating layer is a negative electrode active material for a secondary battery having a thickness of 1 to 100 nm.
  10. a) a microwave heating process for forming silicon particles by irradiating a silicon raw material with microwaves; and silicon nitride (SiNx, 0<x≤2) on at least a portion of the silicon particles; and b) a pre-lithiation process comprising mixing and heat-treating silicon particles and silicon nitride (SiNx, 0<x≤2) produced in the microwave heating process above with a lithium source; a method for manufacturing a negative electrode active material for a secondary battery.
  11. In Paragraph 10, A method for manufacturing a negative electrode active material for a secondary battery, wherein the above a) microwave heating process maintains the reactor at a vacuum of 10⁻⁸ to 10⁻⁴ torr and then injects nitrogen to a pressure of 0.5 to 2 bar.
  12. In Paragraph 10, A method for manufacturing a negative electrode active material for a secondary battery, wherein the silicon raw material comprises nano-sized silicon particles in the above a) microwave heating process.
  13. In Paragraph 10, A method for manufacturing a negative electrode active material for a secondary battery, wherein in the above b) pre-lithiation process, the mixing is performed by mixing silicon particles and silicon nitride (SiNx, 0<x≤2) produced in a microwave heating process with a lithium source such that the molar ratio of Li/Si is 0.3 to 1.0.
  14. In Paragraph 10, A method for manufacturing a negative electrode active material for a secondary battery, wherein in the above b) pre-lithiation process, the heat treatment is performed at 300 to 1,000°C for 1 to 12 hours under an inert atmosphere.
  15. A negative electrode for a secondary battery comprising a negative electrode active material according to any one of claims 1 to 9.
  16. A secondary battery comprising a negative electrode according to paragraph 15; a positive electrode; and an electrolyte.

Description

Negative electrode active material for secondary battery, method for preparing the same and lithium secondary battery including the same The present invention relates to a negative electrode active material for a secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same. With the recent increase in demand for electronic devices, including mobile phones, technological development for these devices is expanding. Consequently, the demand for lithium-ion batteries, such as lithium batteries, lithium-ion batteries, and lithium-ion polymer batteries, is rising significantly as power sources for these electronic devices. Furthermore, driven by the global trend of tightening regulations on vehicle fuel efficiency and exhaust emissions, the growth of the electric vehicle (EV) market is accelerating. Along with this, demand for medium- and large-sized secondary batteries, such as those for EVs and Energy Storage Systems (ESS), is expected to surge. Meanwhile, as the demand for higher capacity in secondary batteries, such as medium and large-sized batteries, has recently increased, silicon-based anode materials with excellent theoretical capacity are being researched as anode materials for secondary batteries. However, silicon-based anode materials cause significant volume changes during lithium insertion and extraction, leading to electrical delamination due to the pulverization of silicon-based composites and problems of reversible capacity loss under repeated cycles. Figure 1 is a cross-sectional TEM (Transmission Electron Microscope) image of the silicon-based composite negative electrode active material prepared in Example 1. Figure 2 is a cross-sectional Scanning electron microscope (SEM) image of the silicon-based composite negative electrode active material prepared in Example 1 and Comparative Example 1. Figure 3 shows the XRD analysis results of the silicon-based composite cathode active materials prepared in Examples 1 and 2. The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Unless otherwise defined, all terms used in this specification (including technical and scientific terms) may be used in a meaning that is commonly understood by those skilled in the art to which the present invention pertains. Throughout the specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. Additionally, when a part such as a layer, film, region, plate, etc. is described in this specification as being “on” or “on” another part, this includes not only cases where it is “immediately on” another part, but also cases where there is another part in between. In this specification, "A to B" means "A or more and B or less" unless specifically defined otherwise. Additionally, "A and/or B" means at least one selected from the group consisting of A and B, unless specifically defined otherwise. One embodiment of the present invention provides a negative electrode active material for a secondary battery comprising a silicon-based composite. The silicon-based composite comprises a first compound (Li-Si-N) containing at least lithium, silicon, and nitrogen; and/or a second compound (Li-Si-O) containing at least lithium, silicon, and oxygen; and comprises silicon nitride (SiNx, 0<x≤2); and/or silicon oxide (SiOy, 0<y≤2). Research is underway to form silicon nitride (SiNx) and/or silicon oxide ( SiO2 ) within silicon particles to suppress volume expansion of silicon particles during the charging and discharging process of secondary batteries and improve cycle life. However, a problem arises where the initial efficiency is lowered because SiNx and SiOy react with lithium during the initial charging and discharging process. In the present invention, by pre-lithiating SiNx and/or SiOy to form the first compound and/or second compound, it was possible to increase the reversible capacity of the silicon anode active material and improve the initial efficiency characteristics. The silicon-based composite may include at least one selected from the group consisting of a first compound (Li-Si-N) and a second compound (Li-Si-O). The composite particles may include the first compound or the second compound, and preferab