Negative active material for secondary battery and secondary battery including the same

Abstract

To provide a negative electrode active material for a secondary battery having improved output characteristics and life characteristics, and a secondary battery including the same.SOLUTION: A negative electrode active material for a lithium secondary battery according to an embodiment of the present disclosure includes a composite particle including a carbon-based particle including pores and a silicon-containing coating formed on a surface of the carbon-based particle, wherein the composite particle has a weight increase starting temperature of 440 °C to 580 °C in thermogravimetric analysis (TGA) measured at a heating rate of 10 °C / min.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The disclosure of the present application relates to a negative electrode active material for a secondary battery, a method for producing the same, and a secondary battery including the same. [Background technology]

[0002] Secondary batteries are capable of repeated charging and discharging, and with the development of the information and communication and display industries, they have been widely used as power sources for portable electronic communication devices such as camcorders, mobile phones, and laptops. Recently, battery packs containing secondary batteries have also been developed and applied as power sources for environmentally friendly automobiles such as electric vehicles.

[0003] Examples of secondary batteries include lithium secondary batteries, nickel-cadmium batteries, nickel-metal hydride batteries, etc. Among them, lithium secondary batteries have been actively developed and applied due to their high operating voltage and energy density per unit weight, as well as advantages in terms of charging speed and light weight.

[0004] Recently, as the range of applications of secondary batteries has expanded, development of secondary batteries with higher capacity and output has been progressing. For example, a high-capacity silicon and carbon composite can be used as a negative electrode active material.

[0005] However, because silicon-carbon composite negative electrode active materials have large differences in volume expansion coefficients, repeated charge and discharge can cause cracks in the negative electrode active material and exposure of the electrolyte. Summary of the Invention [Problem to be solved by the invention]

[0006] According to one aspect of the present disclosure, it is possible to provide a negative electrode active material for a secondary battery having improved output characteristics and life characteristics.

[0007] According to another aspect of the present disclosure, a secondary battery with improved output characteristics and life characteristics can be provided. [Means for solving the problem]

[0008] A negative electrode active material for a secondary battery according to an exemplary embodiment of the present disclosure includes composite particles, the composite particles including pore-containing carbon-based particles and a silicon-containing coating formed on the surfaces of the carbon-based particles, and the composite particles exhibit a weight gain onset temperature of 440°C to 580°C in thermogravimetric analysis (TGA) at a heating rate of 10°C / min.

[0009] In some embodiments, the weight gain onset temperature may be the temperature at the intersection of a tangent line at the average weight point of the maximum weight and the minimum weight and a tangent line at the minimum weight point on the TGA graph.

[0010] In some embodiments, the weight gain onset temperature may be 451°C to 550°C.

[0011] In some embodiments, the composite particles may have a first Raman peak intensity ratio defined by the following formula 1 of 2.25 or more.

[0012] [Formula 1] First Raman peak intensity ratio = ID / IG

[0013] In Formula 1, ID is the peak at 1330 cm in the Raman spectrum of the composite particle. -1 ~1380cm -1 IG is the maximum peak intensity in the wavenumber range of 1560 cm in the Raman spectrum of the composite particle. -1 ~1585cm -1 is the maximum peak intensity in the wavenumber range.

[0014] In some embodiments, the first Raman peak intensity ratio may be 2.37 to 2.63.

[0015] In some embodiments, the Raman spectroscopy spectrum of the composite particle is obtained by analyzing the Raman spectroscopy graph of the composite particle at 1100 cm -1 ~1250cm -1 D* band with maximum peak intensity in the wavenumber range of 1330 cm -1 ~1380cm -1 D band with maximum peak intensity in the wavenumber range of 1500 cm -1 ~1550cm -1 D” band with maximum peak intensity in the wavenumber range of 1560 cm -1 ~1585cm -1 The G band has a maximum peak intensity in the wavenumber range of 1590 cm -1 ~1620cm -1 The D′ band has the maximum peak intensity in the wavenumber range of 1000 to 10 ...

[0016] In some embodiments, the composite particles may have a second Raman peak intensity ratio defined by the following formula 2 of 0.30 or more.

[0017] [Formula 2] Second Raman peak intensity ratio = ID* / IG

[0018] In Formula 2, ID* represents the peak at 1100 cm in the Raman spectrum of the composite particle. -1 ~1250cm -1 IG is the maximum peak intensity in the wavenumber range of 1560 cm in the Raman spectrum of the composite particle. -1 ~1585cm -1 is the maximum peak intensity in the wavenumber range.

[0019] In some embodiments, the second Raman peak intensity ratio may be 0.32 to 0.36.

[0020] In some embodiments, the carbon-based particles can comprise at least one selected from the group consisting of activated carbon, carbon nanotubes, carbon nanowires, graphene, carbon fiber, carbon black, graphite, porous carbon, pyrolyzed cryogel, pyrolyzed xerogel, and pyrolyzed aerogel.

[0021] In some embodiments, the silicon contained in the silicon-containing coating can include an amorphous structure.

[0022] In some embodiments, the silicon content of the composite particles may be 40% to 50% by weight based on the total weight of the composite particles.

[0023] In some embodiments, the composite particles can further include a carbon coating formed on the silicon-containing coating.

[0024] In some embodiments, the pores of the carbon-based particles may include a shape extending from the outermost portion of the carbon-based particle to the interior of the carbon-based particle.

[0025] In some embodiments, the carbon-based particles can include an amorphous structure.

[0026] A secondary battery according to an exemplary embodiment of the present disclosure includes a negative electrode including the aforementioned negative electrode active material for a secondary battery, and a positive electrode facing the negative electrode. [Effects of the Invention]

[0027] According to one embodiment of the present disclosure, it is possible to suppress the generation of gas due to a side reaction between the negative electrode active material and the electrolyte solution.

[0028] According to an embodiment of the present disclosure, the internal resistance of a secondary battery can be reduced.

[0029] According to an embodiment of the present disclosure, it is possible to improve the high-temperature life characteristics of a secondary battery.

[0030] The negative electrode active material for a secondary battery of the present disclosure and a secondary battery including the same can be widely applied in green technology fields such as electric vehicles, battery charging stations, and other battery-based solar power generation and wind power generation. The negative electrode active material for a secondary battery of the present disclosure and a secondary battery including the same can be used in eco-friendly electric vehicles, hybrid vehicles, and the like that prevent climate change by reducing air pollution and greenhouse gas emissions. [Brief explanation of the drawings]

[0031] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating a composite particle according to an exemplary embodiment. [Figure 2] FIG. 2 is a schematic plan view showing a lithium secondary battery according to an exemplary embodiment. [Figure 3] FIG. 3 is a schematic cross-sectional view showing a lithium secondary battery according to an exemplary embodiment. [Figure 4] FIG. 4 shows the Raman spectrum of the composite particles of the example. [Figure 5] FIG. 5 shows the Raman spectrum of the composite particles of the comparative example. [Figure 6] FIG. 6 is a thermogravimetric analysis (TGA) graph of the composite particles of the example as a function of temperature. [Figure 7] FIG. 7 is a thermogravimetric analysis (TGA) graph of the composite particles of the comparative example as a function of temperature. DETAILED DESCRIPTION OF THE INVENTION

[0032] An embodiment of the present disclosure provides a negative electrode active material for a secondary battery (hereinafter, sometimes abbreviated as "negative electrode active material") containing composite particles. A secondary battery including the negative electrode active material is also provided.

[0033] Hereinafter, embodiments of the present disclosure will be described in detail, but these embodiments are merely examples and do not limit the present disclosure.

[0034] FIG. 1 is a schematic cross-sectional view illustrating a composite particle according to an exemplary embodiment.

[0035] While the shape of the composite particles is shown schematically in Figure 1 for convenience of explanation, the structure and shape of the composite particles of the present disclosure are not limited to those shown in Figure 1. For example, the cross section of the carbon-based particles may vary randomly from a circular shape. Furthermore, the silicon-containing coating may be partially formed on the pores and surfaces of the carbon-based particles, or may be formed in a plurality of discontinuous islands or patterns.

[0036] 1, a composite particle 50 may include a carbon (C)-based particle 60 and a silicon (Si)-containing coating 70. For example, the negative electrode active material may include a plurality of composite particles 50.

[0037] In an exemplary embodiment of the present disclosure, the carbon-based particles 60 may include pores 65. For example, the carbon-based particles 60 may be porous particles that include a plurality of pores.

[0038] In some embodiments, "carbon-based particles" may refer to particles composed primarily of carbon. In some embodiments, carbon-based particles 60 may include carbon materials of various forms or configurations, such as activated carbon, carbon nanotubes, carbon nanowires, graphene, carbon fiber, carbon black, graphite, porous carbon, pyrolyzed cryogel, pyrolyzed xerogel, pyrolyzed aerogel, etc. These may be used alone or in combination. In various embodiments of the present invention, carbon-based particles may include one type of carbon material or a combination of two or more different carbon materials.

[0039] In some embodiments, the carbon-based particles 60 may be derived from coconut char and / or petroleum coke.

[0040] In some embodiments, carbon-based particles 60 can include an amorphous structure or a crystalline structure.

[0041] According to one embodiment, the carbon-based particles 60 may include an amorphous structure. In this case, the durability of the negative electrode active material may be increased, and the occurrence of cracks during charge / discharge or external impact may be further suppressed. This may further improve the lifespan of the secondary battery.

[0042] In some embodiments, the pores 65 of the carbon-based particle 60 may include a shape that extends from the outermost portion of the carbon-based particle 60 to the interior of the carbon-based particle 60. For example, the pores 65 may include open pores that are open to the exterior of the carbon-based particle 60.

[0043] In some embodiments, the size of the pores 65 of the carbon-based particles 60 may be 0.1 nm to 10 nm, 0.5 nm to 8 nm, or 1 nm to 5 nm. Within this range, excessive deposition of silicon is prevented, and the occurrence of cracks in the negative electrode active material during charge and discharge of the secondary battery can be further suppressed.

[0044] According to one embodiment, the size of the pores 65 may be measured using a Surface Area Analyzer (ASAP-2420) manufactured by Micromeritics, Inc. For example, the size of the pores 65 can be measured by measuring the maximum peak position of a Barrett-Joyner-Halenda (BJH) pore size distribution curve obtained from a nitrogen gas sorption isotherm of a sample of the carbon-based particles 60.

[0045] A silicon-containing coating 70 can be formed on the surface of the carbon-based particles 60, which include pores 65. For example, the pores 65 can mitigate the volumetric expansion of silicon contained in the silicon-containing coating 70. This allows for the relatively high capacity characteristics of silicon to be utilized, while preventing cracks due to the difference between the volumetric expansion rates of carbon (e.g., about 150% by volume or less) and silicon (e.g., about 400% by volume or more) during battery charge and discharge. This suppresses gas generation due to side reactions between the negative electrode active material and the electrolyte, improving the life characteristics of the secondary battery.

[0046] The "size of the pores 65" may refer to the diameter of the entrance of the pores 65 formed in the surface portion of the carbon-based particle 60.

[0047] As used herein, the terms "surface of a carbon-based particle" and / or "surface of a carbon-based particle 60" can refer to the outer surface 62 of the carbon-based particle 60, the inner surface 67 of the pores 65, or the outer surface 62 of the carbon-based particle 60 and the inner surface 67 of the pores 65.

[0048] For example, the silicon-containing coating 70 may be formed on at least a part of the outer surface 62 of the carbon-based particles 60.

[0049] For example, the silicon-containing coating 70 may be formed on at least a part of the inner surface 67 of the pores 65 of the carbon-based particles 60.

[0050] For example, the silicon-containing coating 70 may be formed on at least a part of the outer surface 62 and at least a part of the inner surface 67 of the pores 65 of the carbon-based particles 60. For example, the carbon-based particles 60 may include voids 68 in which the silicon-containing coating layer 70 is not formed among a large number of pores.

[0051] In some embodiments, the silicon-containing coating 70 contains silicon and may further contain SiO x (0 < x < 2).

[0052] In one embodiment, the silicon contained in the silicon-containing coating 70 can include an amorphous structure. Thereby, the output characteristics can be improved, and the life characteristics during repeated charge and discharge can be further improved.

[0053] In some embodiments, the composite particles 50 may further include a carbon coating (not shown) formed on the silicon-containing coating 70. Thereby, contact between the silicon of the negative electrode active material and water can be prevented. Thereby, it is possible to suppress a decrease in the discharge capacity and capacity efficiency of the secondary battery from when the negative electrode active material is manufactured until before the negative electrode is formed.

[0054] In some embodiments, the carbon coating can also be formed on a portion of the surface of the carbon-based particles 60 where the silicon-containing coating 70 is not formed. For example, the carbon coating can entirely cover the carbon-based particles 60 and the silicon-containing coating 70. Thereby, the mechanical stability and chemical stability of the negative electrode active material can be improved.

[0055] In one embodiment, the carbon coating may include at least one of carbon and a conductive polymer, for example, the conductive polymer may include polyacetylene, polyaniline, polypyrrole, polythiophene, etc.

[0056] According to exemplary embodiments of the present disclosure, the first Raman peak intensity ratio of composite particle 50, as defined by the following formula 1, may be 2.25 or greater. Alternatively, in some embodiments, it may be 2.34 or greater, 2.37 or greater, or 2.55 or greater. In some embodiments, it may be 2.25 to 2.63, or 2.37 to 2.63.

[0057] [Formula 1] First Raman peak intensity ratio = ID / IG

[0058] In Formula 1, ID is the peak at 1330 cm in the Raman spectrum of the composite particle. -1 ~1380cm -1 IG is the maximum peak intensity in the wavenumber range of 1560 cm (for example, the D band of the Raman spectrum) of the composite particle. -1 ~1585cm -1 is the maximum peak intensity in the wavenumber range (for example, the G band in a Raman spectrum).

[0059] As used herein, the term "maximum peak intensity" can refer to the maximum peak height in a particular wavenumber range of a Raman spectroscopy spectrum.

[0060] For example, the first Raman peak intensity ratio may represent the degree of amorphousness of the composite particle 50. For example, the greater the first Raman peak intensity ratio, the greater the amorphousness of the composite particle 50 may be.

[0061] Within this range of the first Raman peak intensity ratio, it is possible to improve the high-temperature stability while sufficiently ensuring the amorphousness of the composite particles 50. As a result, the internal resistance of a secondary battery including a negative electrode active material containing the composite particles 50 can be reduced, and the high-temperature life characteristics can be improved.

[0062] In some embodiments, the second Raman peak intensity ratio of the composite particle 50 defined by the following formula 2 may be 0.30 or more, and in one embodiment, may be 0.30 to 0.36, or 0.32 to 0.36.

[0063] [Formula 2] Second Raman peak intensity ratio = ID* / IG

[0064] In Formula 2, ID* represents the peak at 1100 cm in the Raman spectrum of the composite particle 50. -1 ~1250cm -1 is the maximum peak intensity in the wavenumber range (for example, the D* band of the Raman spectroscopy spectrum) of 1560 cm -1 ~1585cm -1 is the maximum peak intensity in the wavenumber range (for example, the G band of the Raman spectrum).

[0065] For example, the second Raman peak intensity ratio may represent the degree of oxidation of carbon contained in the composite particle 50. For example, as the second Raman peak intensity ratio increases, the high-temperature stability of the carbon-based particles 60 contained in the composite particle 50 can be improved.

[0066] Within this range of the second Raman peak intensity ratio, the internal resistance of a secondary battery including a negative electrode active material containing the composite particles 50 can be reduced, and the high-temperature life characteristics can be improved.

[0067] In some embodiments, the Raman spectroscopy spectrum of the composite particle 50 is obtained by plotting the Raman spectroscopy graph at 1100 cm -1 ~1250cm -1D* band with maximum peak intensity in the wavenumber range of 1330 cm -1 ~1380cm -1 D band with maximum peak intensity in the wavenumber range of 1500 cm -1 ~1550cm -1 D” band with maximum peak intensity in the wavenumber range of 1560 cm -1 ~1585cm -1 The G band has a maximum peak intensity in the wavenumber range of 1590 cm -1 ~1620cm -1 The D′ band has the maximum peak intensity in the wavenumber range of 1000 to 10 ...

[0068] For example, a Raman analyzer can be used to obtain a graph (e.g., the Raman spectroscopy analysis graph) showing the change in peak intensity depending on the wavenumber of the composite particle 50. The graph can be deconvoluted into a curve having the five mutually different maximum peak intensities using a Lorentzian curve. For example, the first Raman peak intensity ratio can be calculated by substituting the maximum peak intensity of the D band (ID in Equation 1) and the maximum peak intensity of the G band (IG in Equation 1) of the five bands into Equation 1. For example, the second Raman peak intensity ratio can be calculated by substituting the maximum peak intensity of the D* band (ID* in Equation 2) and the maximum peak intensity of the G band (IG in Equation 2) of the five bands into Equation 2.

[0069] In exemplary embodiments of the present disclosure, the weight gain onset temperature of composite particle 50 in thermogravimetric analysis (TGA) measured at a heating rate of 10°C / min may be 440°C to 580°C. In some embodiments, the weight gain onset temperature may be 450°C or higher, 480°C or higher, 510°C or higher, 530°C or higher, or 540°C or higher, or 560°C or lower, 540°C or lower, 530°C or lower, 510°C or lower, or 480°C or lower. In some embodiments, the weight gain onset temperature may be 450°C to 570°C, 451°C to 550°C, or 515°C to 550°C.

[0070] The TGA graph may be a graph showing the change in weight of the composite particle 50 depending on the heating temperature. For example, the composite particle 50 is placed in a thermogravimetric analyzer, and the mass change is measured while the temperature is increased from room temperature (25°C) to 900°C at a heating rate of 10°C / min, and the weight change of the composite particle 50 depending on the heating temperature can be shown in a graph (e.g., a TGA graph).

[0071] For example, the weight of the sample of composite particles 50 introduced into the thermogravimetric analyzer may be about 9 mg to 11 mg.

[0072] The weight gain onset temperature may be the temperature at which the composite particles 50 begin to gain weight during thermogravimetric analysis.

[0073] For example, the weight gain onset temperature can be obtained by extrapolating from the midpoint between the maximum weight and the minimum weight on the TGA graph, and may be the temperature at the intersection of a tangent line at the average weight point of the maximum weight and the minimum weight on the TGA graph with a tangent line at the minimum weight point.

[0074] Within this weight gain starting temperature range, the weight gain due to the oxidation of silicon contained in the silicon-containing coating 70 may be greater than the weight loss due to heat loss of the carbon-based particles 60. This reduces the internal resistance of a secondary battery including an anode active material containing the composite particles 50, thereby improving the high-temperature life characteristics.

[0075] In some embodiments, the silicon content of the composite particles 50 may be 40 wt % to 50 wt %, and in one embodiment, 43 wt % to 47 wt % based on the total weight of the composite particles 50. Within this range, silicon can be sufficiently oxidized while suppressing an increase in resistance. This reduces the internal resistance of a secondary battery containing a negative electrode active material containing the composite particles 50, thereby improving high-temperature life characteristics.

[0076] 2 and 3 are a schematic plan view and a cross-sectional view, respectively, showing a lithium secondary battery according to an exemplary embodiment. For example, Fig. 3 is a cross-sectional view taken along "II'" in Fig. 2 in the thickness direction.

[0077] Referring to FIGS. 2 and 3, the lithium secondary battery may include a negative electrode 130 including the above-described negative electrode active material, and a positive electrode 100 facing the negative electrode 130.

[0078] The positive electrode 100 can include a positive electrode current collector 105 and a positive electrode active material layer 110 formed on at least one surface of the positive electrode current collector 105 .

[0079] The positive electrode current collector 105 can include stainless steel, nickel, aluminum, titanium, or an alloy thereof. The positive electrode current collector 105 may also include aluminum or stainless steel that has been surface-treated with carbon, nickel, titanium, or silver. For example, the thickness of the positive electrode current collector 105 may be 10 μm to 50 μm.

[0080] The positive electrode active material layer 110 can include a positive electrode active material, which can include a compound capable of reversibly intercalating and deintercalating lithium ions.

[0081] According to an exemplary embodiment, the positive electrode active material may include a lithium-nickel metal oxide, which may further include at least one of cobalt (Co), manganese (Mn), and aluminum (Al).

[0082] In some embodiments, the positive electrode active material or the lithium-nickel metal oxide may include a layered structure or a crystalline structure represented by Formula 1:

[0083] [Chemical formula 1] Li x Ni a M b O 2+z

[0084] In Chemical Formula 1, 0.9≦x≦1.2, 0.5≦a≦0.99, 0.01≦b≦0.5, and −0.5≦z≦0.1. As mentioned above, M can include Co, Mn, and / or Al.

[0085] The chemical structure represented by Chemical Formula 1 indicates the bonding relationships contained within the layered structure or crystalline structure of the positive electrode active material and does not exclude other additional elements. For example, M may include Co and / or Mn, and Co and / or Mn may serve as the main active elements of the positive electrode active material together with Ni. Chemical Formula 1 is provided to represent the bonding relationships of the main active elements and should be understood as a formula that includes the introduction and substitution of additional elements.

[0086] In one embodiment, in addition to the main active element, an auxiliary element may be further included to improve the chemical stability of the positive electrode active material or the layered structure / crystal structure. The auxiliary element may be incorporated into the layered structure / crystal structure to form a bond. It should be understood that this case is also included within the scope of the chemical structure represented by Chemical Formula 1.

[0087] The auxiliary element may include at least one selected from the group consisting of Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Sr, Ba, Ra, P, and Zr. The auxiliary element, such as Al, may also function as an auxiliary active element that contributes to the capacity / output activity of the positive electrode active material together with Co or Mn.

[0088] For example, the positive electrode active material or the lithium-nickel metal oxide may have a layered structure or a crystalline structure represented by the following Chemical Formula 1-1.

[0089] [Chemical formula 1-1] Li x Ni a M1b1 M2 b2 O 2+z

[0090] In Chemical Formula 1-1, M1 can include Co, Mn, and / or Al, and M2 can include the aforementioned auxiliary elements. In Chemical Formula 1-1, 0.9≦x≦1.2, 0.5≦a≦0.99, 0.01≦b1+b2≦0.5, and −0.5≦z≦0.1 may be satisfied.

[0091] The positive electrode active material may further include a coating element or a doping element. For example, an element substantially the same as or similar to the auxiliary element may be used as the coating element or the doping element. For example, the above elements may be used alone or in combination of two or more.

[0092] The coating element or doping element may be present on the surface of the lithium-nickel metal oxide particles, or may penetrate from the surface of the lithium-nickel metal composite oxide particles and be included in the bonding structure represented by Chemical Formula 1 or Chemical Formula 1-1.

[0093] The positive electrode active material may include a nickel-cobalt-manganese (NCM)-based lithium oxide, in which case an NCM-based lithium oxide with an increased nickel content may be used.

[0094] Ni can be provided as a transition metal related to the output and capacity of lithium secondary batteries. Therefore, by adopting a high-Ni content (High-Ni) composition as the positive electrode active material as described above, a high-capacity positive electrode and a high-capacity lithium secondary battery can be provided.

[0095] However, as the Ni content increases, the long-term storage stability and life stability of the positive electrode or the secondary battery may relatively decrease, and the side reaction with the electrolyte may also increase. On the contrary, according to an exemplary embodiment, by including Co, the electrical conductivity can be maintained while the life stability and capacity retention characteristics can be improved by Mn.

[0096] The Ni content (for example, the molar fraction of Ni in the total number of moles of nickel, cobalt, and manganese) in the NCM-based lithium oxide may be 0.5 or more, 0.6 or more, 0.7 or more, or 0.8 or more. In some embodiments, the Ni content may be 0.8 - 0.95, 0.82 - 0.95, 0.83 - 0.95, 0.84 - 0.95, 0.85 - 0.95, or 0.88 - 0.95.

[0097] In some embodiments, the positive electrode active material may also include a lithium cobalt oxide-based active material, a lithium manganese oxide-based active material, a lithium nickel oxide-based active material, or a lithium iron phosphate-based (LFP) active material (for example, LiFePO4).

[0098] In some embodiments, the positive electrode active material may include, for example, an LLO (Li rich layered oxide) / OLO (Over Lithiated Oxide)-based active material, a Mn-rich-based active material, a Co-less-based active material, etc., having a chemical structure or crystal structure represented by Chemical Formula 2. These can be used alone or in combination of two or more.

[0099] [Chemical Formula 2] p[Li2MnO3]·(1 - p)[Li q JO2]

[0100] In Chemical Formula 2, 0 < p < 1, 0.9 ≤ q ≤ 1.2, and J can include at least one element of Mn, Ni, Co, Fe, Cr, V, Cu, Zn, Ti, Al, Mg, and B.

[0101] The positive electrode active material may be mixed in a solvent to prepare a positive electrode slurry. The positive electrode slurry may be coated on at least one surface of a positive electrode current collector 105, dried, and rolled to prepare a positive electrode active material layer 110. The coating may be performed by gravure coating, slot die coating, multi-layer simultaneous die coating, imprinting, doctor blade coating, dip coating, bar coating, casting, or the like. The positive electrode active material layer 110 may further include a binder, and may optionally further include a conductive material and / or a thickener.

[0102] As the solvent, N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, and the like may be used.

[0103] The binder may include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (poly(vinylidene fluoride-co-hexafluoropropylene)), polyacrylonitrile, polymethylmethacrylate, acrylonitrile butadiene rubber (NBR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), etc. These may be used alone or in combination of two or more.

[0104] In one embodiment, a PVDF-based binder can be used as the positive electrode binder. In this case, the amount of binder required to form the positive electrode active material layer 110 can be reduced, allowing for a relative increase in the amount of positive electrode active material. This can improve the output and capacity characteristics of the secondary battery.

[0105] The conductive material may be added to improve the conductivity and / or mobility of lithium ions or electrons of the positive electrode active material layer 110. For example, the conductive material may include a carbon-based conductive material such as graphite, carbon black, acetylene black, ketjen black, graphene, carbon nanotubes, vapor-grown carbon fiber (VGCF), or carbon fiber, and / or a metal-based conductive material including tin, tin oxide, titanium oxide, or a perovskite material such as LaSrCoO3 or LaSrMnO3. These may be used alone or in combination.

[0106] The positive electrode slurry may further include a thickener and / or a dispersant, etc. In one embodiment, the positive electrode slurry may include a thickener such as carboxymethyl cellulose (CMC).

[0107] The negative electrode 130 can include a negative electrode current collector 125 and a negative electrode active material layer 120 formed on at least one surface of the negative electrode current collector 125 .

[0108] For example, the negative electrode current collector 125 may include copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, etc. These may be used alone or in combination. For example, the thickness of the negative electrode current collector 125 may be 10 μm to 50 μm.

[0109] The negative electrode active material layer 120 may include a negative electrode active material including the above-described composite particles 50. For example, the negative electrode active material may include a plurality of composite particles 50.

[0110] In some embodiments, the negative electrode active material can include composite particles 50 and a graphite-based active material. For example, the graphite-based active material can include synthetic graphite and / or natural graphite.

[0111] The content of the composite particles 50 in the total weight of the negative electrode active material (e.g., the total weight of the plurality of composite particles 50 and the graphite-based active material) may be 3% by weight or more, 5% by weight or more, 10% by weight or more, 15% by weight or more, 20% by weight or more, 25% by weight or more, 30% by weight or more, 35% by weight or more, 40% by weight or more, or 45% by weight or more.

[0112] The content of the composite particles in the total weight of the negative electrode active material may be 99% by weight or less, 95% by weight or less, 90% by weight or less, 85% by weight or less, 80% by weight or less, 75% by weight or less, 70% by weight or less, 65% by weight or less, 60% by weight or less, 55% by weight or less, or 50% by weight or less.

[0113] In one embodiment, the negative electrode active material may consist essentially of composite particles 50 and the graphite-based active material.

[0114] The negative electrode active material may be mixed in a solvent to prepare a negative electrode slurry. The negative electrode slurry may be coated or deposited on a negative electrode current collector 125, and then dried and rolled to prepare a negative electrode active material layer 120. The coating may be performed by gravure coating, slot die coating, multi-layer simultaneous die coating, imprinting, doctor blade coating, dip coating, bar coating, casting, or the like. The negative electrode active material layer 120 may further include a binder, and may optionally further include a conductive material, a thickener, or the like.

[0115] The solvent contained in the negative electrode slurry can include water, pure water, deionized water, distilled water, ethanol, isopropanol, methanol, acetone, n-propanol, t-butanol, etc. These can be used alone or in combination of two or more.

[0116] The binder, conductive material, and thickener may be the same materials as those used in manufacturing the positive electrode 100 .

[0117] In some embodiments, the negative electrode binder may be a styrene-butadiene rubber (SBR)-based binder, a carboxymethyl cellulose (CMC), a polyacrylic acid-based binder, a polyethylenedioxythiophene (poly(3,4-ethylenedioxythiophene), PEDOT)-based binder, or the like. These may be used alone or in combination of two or more.

[0118] In an exemplary embodiment, a separator 140 may be interposed between the positive electrode 100 and the negative electrode 130. The separator 140 may be configured to prevent an electrical short circuit between the positive electrode 100 and the negative electrode 130 and allow ions to flow. For example, the thickness of the separator may be 10 μm to 20 μm.

[0119] For example, the separator 140 may include a porous polymer film or a porous nonwoven fabric.

[0120] The porous polymer film may include polyolefin polymers such as ethylene polymer, propylene polymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, which may be used alone or in combination of two or more.

[0121] The porous nonwoven fabric may include high-melting glass fibers, polyethylene terephthalate fibers, and the like.

[0122] The separator 140 may also include a ceramic material. For example, inorganic particles may be coated on or dispersed within the polymer film to improve heat resistance.

[0123] The separator 140 may have a single layer or multi-layer structure including the above-mentioned polymer film and / or nonwoven fabric.

[0124] According to an exemplary embodiment, an electrode cell is defined by the positive electrode 100, the negative electrode 130, and the separator 140, and a plurality of electrode cells may be stacked to form, for example, a jelly roll-shaped electrode assembly 150. For example, the electrode assembly 150 may be formed by winding, stacking, Z-folding, stack-folding, etc. of the separator 140.

[0125] A lithium secondary battery can be defined by housing the electrode assembly 150 together with an electrolyte in the case 160. According to an exemplary embodiment, an electrolyte solution can be contained in the case 160 together with the electrode assembly 150. A non-aqueous electrolyte solution can be used as the electrolyte solution.

[0126] The non-aqueous electrolyte solution contains a lithium salt as an electrolyte and an organic solvent. + X - and the anion (X - ) as F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P- , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , and (CF3CF2SO2)2N - Examples include:

[0127] Examples of the organic solvent include propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate, diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate, ethyl propyl carbonate, dipropyl carbonate, vinylene carbonate, methyl acetate (MA), ethyl acetate (EA), n-propyl acetate (n-PA), 1,1-dimethylethyl acetate (DMEA), methyl propionate (MP), ethyl propionate (EP), fluoroethyl acetate (FEA), difluoroethyl acetate (DFEA), trifluoroethyl acetate (TFEA), dibutyl ether (dibutyl ether), Examples of solvents that can be used include tetraethylene glycol dimethyl ether (TEGDME), diethylene glycol dimethyl ether (DEGDME), tetrahydrofuran (THF), 2-methyltetrahydrofuran, ethyl alcohol, isopropyl alcohol, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, sulfolane, gamma-butyrolactone, and propylene sulfite. These can be used alone or in combination of two or more.

[0128] The non-aqueous electrolyte may further include additives such as cyclic carbonate compounds, fluorine-substituted carbonate compounds, sultone compounds, cyclic sulfate compounds, cyclic sulfite compounds, phosphate compounds, and borate compounds, which may be used alone or in combination.

[0129] The cyclic carbonate-based compound may include vinylene carbonate (VC), vinyl ethylene carbonate (VEC), and the like.

[0130] The fluorine-substituted carbonate-based compound may include fluoroethylene carbonate (FEC).

[0131] The sultone-based compound may include 1,3-propane sultone, 1,3-propene sultone, 1,4-butane sultone, and the like.

[0132] The cyclic sulfate compound may include 1,2-ethylene sulfate, 1,2-propylene sulfate, and the like.

[0133] The cyclic sulfite-based compound may include ethylene sulfite, butylene sulfite, and the like.

[0134] The phosphate-based compound may include lithium difluoro bis-oxalato phosphate, lithium difluoro phosphate, and the like.

[0135] The borate-based compound may include lithium bis(oxalate)borate.

[0136] In some embodiments, a solid electrolyte may be used instead of the nonaqueous electrolyte solution. In this case, the lithium secondary battery may be manufactured as an all-solid-state battery. Also, a solid electrolyte layer may be disposed between the positive electrode 100 and the negative electrode 130 instead of the separator 140.

[0137] The solid electrolyte may include a sulfide-based electrolyte. Non-limiting examples of the sulfide-based electrolyte include Li2S-P2S5, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, Li2S-P2S5-LiCl-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, and Li2S-P2S5-Z. m S n (m and n are positive numbers, and Z is Ge, Zn, or Ga.), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p and q are positive numbers, and M is P, Si, Ge, B, Al, Ga, or In.) Li7-xPS6-xCl x (0≦x≦2), Li7-xPS6-xBr x (0≦x≦2), Li7-xPS 6- xI x(0≦x≦2), etc. These can be used alone or in combination of two or more.

[0138] In one embodiment, the solid electrolyte may include an oxide-based amorphous solid electrolyte such as, for example, Li2O-B2O3-P2O5, Li2O-SiO2, Li2O-B2O3, or Li2O-B2O3-ZnO.

[0139] 2 and 3, electrode tabs (positive electrode tab and negative electrode tab) may protrude from the positive electrode current collector 105 and the negative electrode current collector 125 of each electrode cell and extend to one side of the case 160. The electrode tabs may be fused to the one side of the outer case 160 to form electrode leads (positive electrode lead 107 and negative electrode lead 127) that extend or are exposed to the outside of the outer case 160.

[0140] The lithium secondary battery may be manufactured in a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

[0141] Hereinafter, embodiments of the present disclosure will be further described with reference to specific experimental examples. The examples and comparative examples included in the experimental examples are merely illustrative of the present disclosure and do not limit the scope of the appended claims. It is clear to those skilled in the art that various changes and modifications can be made to these examples within the scope and technical spirit of the present disclosure, and it is natural that these changes and modifications also fall within the scope of the appended claims.

[0142] Example 1 Production of carbon-based particles The coconut shells were dried to remove moisture, and then heated to 900°C at a rate of 10°C / min while nitrogen gas was introduced into the coconut shells. The coconut shells were then carbonized at 900°C for 1 hour and naturally cooled to room temperature (25°C) to produce coconut shell char powder.

[0143] The mixture of coconut shell charcoal powder and KOH aqueous solution was heated to 600-850°C at a rate of 10°C / min under an argon gas atmosphere, and then heat-treated at 600-850°C for 1 hour to activate the coconut shell charcoal powder.

[0144] A mixture of 1M hydrochloric acid solution and the coconut shell charcoal powder was stirred at 70°C for 12 hours, and then repeatedly washed with distilled water until the pH reached 7.

[0145] After the washing, the coconut shell charcoal powder was dried and heat-treated at 750° C. for 1 hour while introducing a hydrogen-containing gas (a mixed gas of hydrogen and nitrogen with a mass ratio of 5:95) to produce carbonaceous particles.

[0146] Formation of silicon-containing coatings A silicon-containing gas containing silane and argon gases in a volume ratio of 1:9 was injected into the CVD coater at a flow rate of 50 mL / min to 100 mL / min. The temperature was increased to 400 °C at a rate of 5 °C / min to 20 °C / min, and then the mixture was baked at 400 °C for approximately 120 minutes to produce composite particles with a silicon-containing coating.

[0147] Formation of the negative electrode A negative electrode slurry was obtained by mixing 95.5 wt% of the negative electrode active material, which was a mixture of 15 wt% of the prepared composite particles and 80.5 wt% of artificial graphite, 1 wt% of CNT as a conductive material, 2 wt% of styrene-butadiene rubber (SBR) as a binder, and 1.5 wt% of carboxymethyl cellulose (CMC) as a thickener.

[0148] The negative electrode slurry was coated on a copper substrate, dried, and pressed to prepare a negative electrode.

[0149] Lithium half cell manufacturing A lithium half cell was fabricated using the negative electrode prepared by the above method and lithium metal as a counter electrode (positive electrode).

[0150] Specifically, a separator (polyethylene, 20 μm thick) was interposed between the prepared negative electrode and lithium metal (1 mm thick) to form a CR2016 (diameter 20 mm, thickness 1.6 mm) lithium coin half-cell.

[0151] The lithium metal / separator / anode assembly was placed in a coin cell plate, the electrolyte was poured in, and the plate was then clamped with a cap. The electrolyte was a 1M LiPF6 solution prepared using a mixed solvent of EC / EMC (3:7 by volume), to which 2.0% by volume of fluoroethylene carbonate (FEC) was added. After clamping, the plate was left to soak for 3 to 24 hours, and then three charge-discharge cycles were performed at 0.1C (charge conditions: CC-CV 0.1C 0.01V 0.01C cut-off, discharge conditions: CC 0.1C 1.5V cut-off).

[0152] Lithium secondary battery manufacturing LiNi as a positive electrode active material 0.88 Co 0.1 Mn 0.02 A positive electrode slurry was prepared by mixing O2, carbon black as a conductive material, and polyvinylidene fluoride (PVdF) as a binder in a weight ratio of 96.5:2:1.5.

[0153] The positive electrode slurry was uniformly coated on an aluminum current collector (thickness: 12 μm), vacuum dried, and rolled to prepare a positive electrode.

[0154] The positive electrode and the negative electrode were notched to a predetermined size and stacked. A separator (polyethylene, 13 μm thick) was interposed between the positive electrode and the negative electrode to form an electrode cell, and the tabs of the positive electrode and the negative electrode were welded. The welded positive electrode / separator / negative electrode assembly was placed in a pouch, and three sides except for the electrolyte injection area were sealed. At this time, the area with the electrode tab was included in the sealed area. Electrolyte was injected through the electrolyte injection area, and the electrolyte injection area was also sealed. The electrolyte was then allowed to soak for 12 hours or more to produce a lithium secondary battery.

[0155] The electrolyte was prepared by preparing a 1M LiPF solution using a mixed solvent of EC / EMC / DEC (volume ratio of 25 / 45 / 30), and adding 1 wt% vinylene carbonate (VC), 0.5 wt% 1,3-propene sultone (PRS), and 0.5 wt% lithium bis(oxalato)borate (LiBOB) based on the total weight of the solution.

[0156] The lithium secondary battery was pre-charged for 36 minutes at a current equivalent to 0.25 C. After 1 hour, it was degassed and aged for 24 hours or more, after which it was subjected to chemical charge-discharge (charge conditions: CC / CV 0.2 C 4.2 V 0.05 C CUT-OFF, discharge conditions: CC 0.2 C 2.5 V CUT-OFF).

[0157] Thereafter, standard charging and discharging was performed (charging conditions: CC / CV 0.5C 4.2V 0.05C CUT-OFF, discharging conditions: CC 0.5C 2.5V CUT-OFF).

[0158] Example 2 Composite particles, a negative electrode, and a lithium half cell were produced in the same manner as in Example 1, except that the carbon-based particles were produced by the following method.

[0159] The mixture of petroleum coke powder and KOH aqueous solution was heated to 600-850°C at a rate of 10°C / min under an argon gas atmosphere, and then heat-treated at 600-850°C for 1 hour to activate the petroleum coke powder.

[0160] A mixture of 1M hydrochloric acid solution and the petroleum coke powder was stirred at 70°C for 12 hours, and then repeatedly washed with distilled water until the pH reached 7.

[0161] After the washing, the petroleum coke powder was dried and heat-treated at 750° C. for 1 hour while introducing the hydrogen-containing gas to produce carbon-based particles.

[0162] Example 3 After the washing, the coconut shell charcoal powder was dried and heat-treated at 900°C for 1 hour while introducing the hydrogen-containing gas to produce carbon-based particles. Except for this, composite particles, anodes, and lithium half cells were produced in the same manner as in Example 1.

[0163] Example 4 Composite particles, a negative electrode, and a lithium half cell were produced in the same manner as in Example 1, except that the coconut shell charcoal powder was activated by the following method. The coconut shell charcoal powder was activated by introducing CO2 gas at a flow rate of 600 mL / min into the coconut shell charcoal powder at 900°C for 5 hours.

[0164] Example 5 Composite particles, a negative electrode, and a lithium half cell were produced in the same manner as in Example 1, except that the carbon-based particles were produced by the following method.

[0165] Nitrogen gas was introduced into resol phenol formaldehyde resin, and the temperature was raised to 900°C at a rate of 10°C / min. The resin was carbonized at 900°C for 1 hour and then naturally cooled to room temperature (25°C) to produce resin-based char powder.

[0166] The mixture of the resin-based carbon powder and KOH aqueous solution was heated to 600-850°C at a rate of 10°C / min in an argon gas atmosphere, and then heat-treated at 600-850°C for 1 hour to activate the resin-based carbon powder.

[0167] A mixture of 1M hydrochloric acid solution and the resin-based carbon powder was stirred at 70°C for 12 hours, and then repeatedly washed with distilled water until the pH reached 7.

[0168] After the washing, the resin-based carbon powder was dried and heat-treated at 750° C. for 1 hour while introducing the hydrogen-containing gas to produce carbon-based particles.

[0169] Example 6 After the washing, the petroleum coke powder was dried and heat-treated at 900°C for 1 hour while introducing the hydrogen-containing gas to produce carbon-based particles. Except for this, composite particles, anodes, and lithium half-cells were produced in the same manner as in Example 2.

[0170] Example 7 After the washing, the petroleum coke powder was dried and heat-treated at 950°C for 1 hour while introducing the hydrogen-containing gas to produce carbon-based particles. Except for this, composite particles, anodes, and lithium half-cells were produced in the same manner as in Example 2.

[0171] Example 8 After the washing, the petroleum coke powder was dried and heat-treated at 650°C for 1 hour while introducing the hydrogen-containing gas to produce carbon-based particles. Except for this, composite particles, anodes, and lithium half-cells were produced in the same manner as in Example 2.

[0172] Example 9 Composite particles, a negative electrode, and a lithium half cell were produced in the same manner as in Example 1, except that the coconut shell charcoal powder was activated by the following method. The coconut shell charcoal powder was activated by introducing CO2 gas at a flow rate of 600 mL / min into the coconut shell charcoal powder at 750°C for 3 hours.

[0173] Example 10 After the washing, the coconut shell charcoal powder was dried and heat-treated at 950°C for 3 hours while introducing the hydrogen-containing gas to produce carbon-based particles. Except for this, composite particles, anodes, and lithium half cells were produced in the same manner as in Example 1.

[0174] Example 11 Composite particles, anodes, and lithium half-cells were produced in the same manner as in Example 1, except that the temperature was raised to 350°C at a rate of 5°C / min to 20°C / min during the formation of the silicon-containing coating, and then the mixture was baked at 350°C for about 90 minutes.

[0175] Example 12 Composite particles, anodes, and lithium half-cells were produced in the same manner as in Example 1, except that the temperature was raised to 450°C at a rate of 5°C / min to 20°C / min during the formation of the silicon-containing coating, and then the mixture was baked at 450°C for about 150 minutes.

[0176] Comparative Example 1 After the washing, the coconut shell charcoal powder was dried and heat-treated at 600°C for 1 hour while introducing the hydrogen-containing gas to produce carbon-based particles. Except for this, composite particles, anodes, and lithium half cells were produced in the same manner as in Example 1.

[0177] Comparative Example 2 After the washing, the resin-based carbon powder was dried and heat-treated at 600°C for 1 hour while introducing the hydrogen-containing gas to produce carbon-based particles. The composite particles, anode, and lithium half-cell were produced in the same manner as in Example 5, except that the resin-based carbon powder was dried and heat-treated at 600°C for 1 hour while introducing the hydrogen-containing gas to produce carbon-based particles.

[0178] Comparative Example 3 Composite particles, anodes, and lithium half-cells were produced in the same manner as in Example 2, except that the stirring and washing were not performed, and the petroleum coke powder was heat-treated at 750°C for 1 hour while the hydrogen-containing gas was introduced to produce carbon-based particles.

[0179] Comparative Example 4 After the washing, the petroleum coke powder was dried and heat-treated at 600°C for 1 hour while introducing the hydrogen-containing gas to produce carbon-based particles. Except for this, composite particles, anodes, and lithium half cells were produced in the same manner as in Example 2.

[0180] Comparative Example 5 After the washing, the petroleum coke powder was dried and heat-treated at 1000°C for 1 hour while introducing the hydrogen-containing gas to produce carbon-based particles. Except for this, composite particles, anodes, and lithium half-cells were produced in the same manner as in Example 2.

[0181] Comparative Example 6 Composite particles, a negative electrode, and a lithium half cell were produced in the same manner as in Example 1, except that the coconut shell charcoal powder was activated by the following method. The coconut shell charcoal powder was activated by introducing CO2 gas at a flow rate of 500 mL / min into the coconut shell charcoal powder at 600°C for 1 hour.

[0182] Experimental example (1) Measurement of the first Raman peak intensity ratio (ID / IG) and the second Raman peak intensity ratio (ID* / IG) The composite particles of the above-mentioned Examples and Comparative Examples were analyzed using a 532 nm laser Raman analyzer (model name: Invia, manufacturer: RENISHAW) to measure the wave number (Raman shift, cm -1 A Raman spectroscopy graph showing the change in peak intensity due to the

[0183] A specific measurement method using a Raman analyzer is as follows. i) The Raman analyzer was turned on. ii) The Spectral acquisition setup window was opened. iii) Select "Static" as the Grating Scan Type and set the Center value to 1000 (Raman Shift (cm -1 )) was entered. iv) In the configuration, a 532 nm edge filter was selected as the laser filter element, 1800 l / mm (vis) as the grating, and a Renishaw 1024 StreamLine CCD as the detector. v) In the acquisition condition settings, Exposure time (s) was set to 20, Objective was set to 50, Accumulation was set to 10, Laser power (%) was set to 1 (<0.5 mW), and Laser Focus Level (%) was set to 0 (beam size: 1 μm to 2 μm). vi) The composite particles were placed on a sample stage, and the measurement site was confirmed, and then a Raman spectroscopic analysis graph of the composite particles was obtained.

[0184] For the Raman spectroscopy analysis graph, WiRE TM Software baseline correction (1000cm -1 ~1800cm -1 ) and using the Lorentzian curve measured by the curve fit function, -1 ~1250cm -1 D* band with maximum peak intensity in the wavenumber range of 1330 cm -1 ~1380cm -1 D band with maximum peak intensity in the wavenumber range of 1500 cm -1 ~1550cm -1 D” band with maximum peak intensity in the wavenumber range of 1560 cm -1 ~1585cm -1 The G band has a maximum peak intensity in the wavenumber range of 1590 cm -1 ~1620cm -1 The D' bands were deconvoluted into five curves with maximum peak intensities in the wavenumber range of 1000 to 10000.

[0185] The maximum peak intensity of the D band (ID), the maximum peak intensity of the G band (IG), and the maximum peak intensity of the D* band (ID*) were substituted into Equation 1 and Equation 2 to calculate the first Raman peak intensity ratio (ID / IG) and the second Raman peak intensity ratio (ID* / IG).

[0186] 4 and 5 show the Raman spectra of the composite particles of Example 6 and Comparative Example 2, respectively.

[0187] Referring to Figures 4 and 5, the Raman spectroscopy graph was deconvoluted into five curves corresponding to each of the aforementioned bands.

[0188] (2) Thermogravimetric analysis (TGA) 10 mg of each of the composite particles of the above-mentioned Examples and Comparative Examples was separated and used as a sample.

[0189] The sample was placed in a thermogravimetric analyzer (model name: Discovery TGA550, manufacturer: TA instruments), and the mass change of the sample was measured while the temperature was increased from room temperature (25°C) to 900°C at a heating rate of 10°C / min. The change in sample weight due to heating temperature was shown in a TGA graph.

[0190] In the TGA graph, the temperature at the intersection of the tangent line at the average weight point of the maximum weight and the minimum weight and the tangent line at the minimum weight point was evaluated as the weight increase starting temperature.

[0191] 6 and 7 are thermogravimetric analysis (TGA) graphs of the composite particles of Example 6 and Comparative Example 2, respectively, as a function of temperature.

[0192] (3) Measurement of silicon content (Si content) of composite particles Samples of the composite particles prepared according to the above examples and comparative examples were placed in polypropylene tubes. Nitric acid and a small amount of hydrofluoric acid were added to the polypropylene tubes and left overnight at room temperature to dissolve. After the samples were dissolved, the polypropylene tubes were cooled, saturated boric acid water was added to neutralize the hydrofluoric acid, and the mixture was diluted with ultrapure water. Carbon components were removed using a 0.45 μm syringe filter.

[0193] The sample was put into an inductively coupled plasma spectrometer (model name: ICP-OES Optima 8300, manufacturer: Perkin Elmer) and analyzed to measure the silicon content in the total weight of the composite particles.

[0194] (4) Measurement of internal resistance The lithium batteries manufactured according to the above examples and comparative examples were charged (CC / CV 0.3C, 4.2V, 0.05C, CUT-OFF) and discharged (CC 0.3C, 2.5V, CUT-OFF) twice at room temperature (25°C). Then, they were discharged (CC 0.3C) to 50% SOC while in the charged (CC / CV 0.3C, 4.2V, 0.05C, CUT-OFF) state, and the DCIR (mΩ) at 50% SOC for 10 seconds was measured.

[0195] (5) Evaluation of high-temperature capacity retention rate (45°C) The lithium half-cells of the Examples and Comparative Examples were charged (CC-CV 0.1 C, 0.01 V, 0.01 C, cut-off) and discharged (CC 0.1 C, 1.5 V, cut-off) 100 times each in a chamber maintained at 45°C, and the high-temperature capacity retention rate was evaluated by dividing the discharge capacity at the 100th charge by the discharge capacity at the first charge and multiplying the result by 100.

[0196] Table 1 shows the first Raman peak intensity ratio (ID / IG), second Raman peak intensity ratio (ID* / IG), TGA weight gain onset temperature, and Si content relative to the total weight of the composite particles for the examples and comparative examples.

[0197] Table 2 shows the internal resistance and high-temperature capacity retention rate of the examples and comparative examples.

[0198] [Table 1]

[0199] [Table 2]

[0200] Referring to Tables 1 and 2, in the Examples where the weight gain starting temperature in the TGA analysis was 440° C. to 580° C., the internal resistance was reduced overall and the high temperature capacity retention rate was improved compared to the Comparative Examples.

[0201] In Examples 1, 3, and 4 in which the second Raman peak intensity ratio was less than 0.30, the internal resistance relatively increased and the high-temperature capacity retention rate decreased compared to the other Examples.

[0202] In Examples 9 and 10, in which the first Raman peak intensity ratio was less than 2.25, the internal resistance relatively increased and the high-temperature capacity retention rate decreased compared to the other Examples.

[0203] In Example 11, in which the silicon content in the total weight of the composite particles was less than 40 wt %, the internal resistance increased relatively compared to the other Examples.

[0204] In Example 12, in which the silicon content in the total weight of the composite particles exceeded 50 wt %, the high-temperature capacity retention rate was relatively lower than in the other Examples. [Explanation of symbols]

[0205] 50: Composite particles 60: Carbon-based particles 62: Outer surface of carbon-based particle 65: Pore 67: Inner surface of pore 70: Silicon-containing coating 100: Positive electrode 105: Positive electrode current collector 107: Positive electrode lead 110: Positive electrode active material layer 120: Negative electrode active material layer 125: Negative electrode current collector 127: Negative electrode lead 130: Negative electrode 140: Separation membrane 150: Electrode assembly 160: Case

Claims

1. carbon-based particles containing pores; a silicon-containing coating formed on the surface of the carbon-based particle, The composite particles have a weight increase starting temperature of 440°C to 580°C in thermogravimetric analysis (TGA) measured at a heating rate of 10°C / min.

2. 2. The negative electrode active material for a secondary battery according to claim 1, wherein the weight increase starting temperature is a temperature at an intersection of a tangent line at an average weight point of the maximum weight and the minimum weight and a tangent line at the minimum weight point in a TGA graph.

3. 2. The negative electrode active material for a secondary battery according to claim 1, wherein the weight increase starting temperature is 451°C to 550°C.

4. The negative electrode active material for a secondary battery according to claim 1 , wherein the composite particles have a first Raman peak intensity ratio defined by the following formula 1 of 2.25 or more: [Formula 1] First Raman peak intensity ratio = ID / IG In Formula 1, ID represents the peak at 1330 cm in the Raman spectrum of the composite particle. －１ ~1380cm －１ IG is the maximum peak intensity in the wavenumber range of 1560 cm in the Raman spectrum of the composite particle. －１ ~1585cm －１ is the maximum peak intensity in the wavenumber range.

5. 5. The negative electrode active material for a secondary battery according to claim 4, wherein the first Raman peak intensity ratio is 2.37 to 2.

63.

6. The Raman spectroscopy graph of the composite particle was obtained by －１ ~1250cm －１ D* band with maximum peak intensity in the wavenumber range of 1330 cm －１ ~1380cm －１ D band with a maximum peak intensity in the wavenumber range of 1500 cm －１ ~1550cm －１ D″ band with maximum peak intensity in the wavenumber range of 1560 cm －１ ~1585cm －１ and the G band with a maximum peak intensity in the wavenumber range of 1590 cm －１ ~1620cm －１ The negative electrode active material for a secondary battery according to claim 4, wherein the negative electrode active material is obtained by deconvolution into five curves including a D' band having a maximum peak intensity in a wave number range of 1000 Hz.

7. The negative electrode active material for a secondary battery according to claim 1 , wherein the composite particles have a second Raman peak intensity ratio defined by the following formula 2 of 0.30 or more: [Formula 2] Second Raman peak intensity ratio = ID* / IG In Formula 2, ID* represents the peak at 1100 cm in the Raman spectrum of the composite particle. －１ ~1250cm －１ IG is the maximum peak intensity in the wavenumber range of 1560 cm in the Raman spectrum of the composite particle. －１ ~1585cm －１ is the maximum peak intensity in the wavenumber range.

8. 8. The negative electrode active material for a secondary battery according to claim 7, wherein the second Raman peak intensity ratio is 0.32 to 0.

36.

9. 2. The negative electrode active material for a secondary battery according to claim 1, wherein the carbon-based particles comprise at least one selected from the group consisting of activated carbon, carbon nanotubes, carbon nanowires, graphene, carbon fibers, carbon black, graphite, porous carbon, pyrolyzed cryogel, pyrolyzed xerogel, and pyrolyzed aerogel.

10. The negative electrode active material for a secondary battery according to claim 1 , wherein the silicon contained in the silicon-containing coating has an amorphous structure.

11. 2. The negative electrode active material for a secondary battery according to claim 1, wherein the silicon content of the composite particles is 40% by weight to 50% by weight based on the total weight of the composite particles.

12. The negative electrode active material for a secondary battery according to claim 1 , wherein the composite particles further comprise a carbon coating formed on the silicon-containing coating.

13. The negative electrode active material for a secondary battery according to claim 1 , wherein the pores of the carbon-based particles have a shape extending from an outermost portion of the carbon-based particle to an interior of the carbon-based particle.

14. The negative electrode active material for a secondary battery according to claim 1 , wherein the carbon-based particles have an amorphous structure.

15. a negative electrode comprising the negative electrode active material for a secondary battery according to claim 1; a positive electrode facing the negative electrode.

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