Negative electrode material for lithium secondary battery and secondary battery comprising same

Abstract

The present invention relates to: a negative electrode material for a secondary battery; and a secondary battery comprising same. The negative electrode material for a secondary battery according to the present invention comprises a silicon-based core and a carbon coating layer located on the surface of the silicon-based core, and may have a high output, excellent cycle characteristics, and uniform electrochemical characteristics.

Description

Anode material for lithium secondary batteries and secondary batteries containing the same

[0001] The present invention relates to a negative electrode material for a lithium secondary battery and a secondary battery including the same.

[0002] Demand for secondary batteries with high energy density, high power density, and long lifespan continues to grow across a wide range of industries, including electronics, electric vehicles (EVs), energy storage systems (ESS), and aerospace / drones.

[0003] Typically, a rechargeable lithium secondary battery is composed of a cathode, an anode, an electrolyte, and a separator. Among these, the representative cathode material used commercially in the cathode is graphite, but the theoretical maximum capacity of graphite is only 372 mAh / g.

[0004] In order to realize high-energy-density secondary batteries, research is continuously being conducted to use chalcogen-based materials such as sulfur (maximum capacity 1,675 mAh / g), silicon-based materials such as silicon (maximum capacity 4,200 mAh / g) or silicon oxide (maximum capacity 1,500 mAh / g), and transition metal oxides as secondary battery anode materials. Among various materials, silicon-based anode materials are receiving the most attention due to their high theoretical capacity, low reaction potential with lithium, and being environmentally friendly.

[0005] However, when using particulate silicon as an anode material, there is a problem that the battery characteristics rapidly deteriorate due to insulation, particle detachment, and increased contact resistance caused by large volume changes in the silicon as charge and discharge cycling are repeated, thereby losing its function as a battery. On the other hand, in the case of silicon oxide, there is a problem that lithium is lost due to irreversible products such as lithium silicate or lithium oxide, and the initial charge and discharge efficiency rapidly decreases.

[0006] To address these issues with silicon-based anode materials, a cathode material has been disclosed in which a carbon coating layer is formed on the surface of a metal-doped silicon oxide anode material through chemical vapor deposition (CVD). However, the anode material requires the use of expensive hydrocarbon gases, and its conversion efficiency to carbon is low in the temperature range that suppresses silicon phase growth, making it uneconomical. In addition, it is difficult to uniformly coat the surface of silicon oxide particles when mass-producing the anode material.

[0007] Furthermore, the CVD coating process inevitably generates a temperature gradient within the reactor because hydrocarbon gas is continuously supplied from the outside and heat is supplied through the reactor's outer wall. Furthermore, because hydrocarbon decomposition is an endothermic reaction, the temperature gradient increases as the silicon oxide particles move away from the heat source, reducing the uniformity of the deposited carbon coating layer.

[0008] This non-uniformity of the carbon coating layer leads to non-uniformity in the electrochemical properties of the anode material, which negatively impacts initial charge / discharge efficiency, cycle characteristics, and cycle life. Therefore, there is a continuing need for the development of anode materials for silicon-based secondary batteries that exhibit superior initial charge / discharge efficiency, cycle characteristics, and cycle life, as well as high-power characteristics.

[0009] According to one embodiment of the present invention, a negative electrode material for a silicon-based secondary battery having improved initial charge / discharge efficiency, cycle characteristics, and life characteristics, and a lithium secondary battery including the same can be provided.

[0010] According to one embodiment of the present invention, a silicon-based secondary battery negative electrode material having uniform electrochemical properties not only between negative electrode particles but also within negative electrode particles, and a lithium secondary battery including the same can be provided.

[0011] The objectives of the present invention are not limited to the above-described scope. Those skilled in the art will have no difficulty understanding the additional objectives of the present invention from the overall content of this specification.

[0012] According to one embodiment of the present invention, a negative electrode material for a secondary battery comprises a silicon-based core; and a carbon coating layer positioned on the surface of the silicon-based core; and a ratio (I) of intensities of a D band peak and a G band peak in a Raman spectroscopy spectrum of the negative electrode material D / I G ) is the ratio of the full width at half maximum (FWHM) of the D band and G band peaks (F D / F G ) is smaller than the full width at half maximum (FWHM) ratio (F D / F G ) is 1.3 or more, and the silicon core has a Type Ⅱ behavior in the nitrogen adsorption / desorption isotherm graph.

[0013] In a negative electrode material for a secondary battery according to one embodiment, in the infrared spectral spectrum of the negative electrode material, 1400 to 1625±5 cm -1 The area (A1) of the peak of the first wave number (n1) of the range is 1625±5 to 2100 cm -1 It may be smaller than the area (A2) of the peak of the second wave number (n2) of the range.

[0014] In a negative electrode material for a secondary battery according to one embodiment, the ratio (A2 / A1) of the area (A1) of the peak of the first wave number (n1) and the area (A2) of the peak of the second wave number (n2) may be 2 or more.

[0015] In a negative electrode material for a secondary battery according to one embodiment, the ratio of the strength (I D / I G ) may be less than 1.3.

[0016] In a negative electrode material for a secondary battery according to one embodiment, the full width at half maximum (F) of the G band peak G ) is 60 cm-1 It could be strange.

[0017] In a negative electrode material for a secondary battery according to one embodiment, the silicon-based core may include a matrix including silicon oxide, and silicon nanocrystals dispersed and embedded in the matrix.

[0018] In a negative electrode material for a secondary battery according to one embodiment, the following equation 1 can be satisfied based on a silicon Raman signal.

[0019] (Formula 1)

[0020] 1 > WN(Si) / WN(ref)

[0021] In Equation 1, WN(ref) is the center wavenumber of the Raman peak of bulk single crystal silicon, and WN(Si) is the center wavenumber of the Raman peak of silicon nanocrystals contained in the cathode material.

[0022] In an anode material for a secondary battery according to one embodiment, the full width half maximum (FWHM) of a silicon Raman peak of nanocrystals contained in the anode material may be greater than the FWHM of a Raman peak of bulk single crystal silicon.

[0023] In a negative electrode material for a secondary battery according to one embodiment, the full width half maximum (FWHM) of the Raman peak of the nanoparticle-type silicon contained in the negative electrode material is 4 to 20 cm -1 It could be.

[0024] In a negative electrode material for a secondary battery according to one embodiment, the silicon core is randomly arranged at 10 different locations such that the difference between the maximum and minimum values ​​of the central wavenumber WN(Si) of the Raman peak of the silicon nanocrystal is 5 cm. -1 It could be as follows:

[0025] In a negative electrode material for a secondary battery according to one embodiment, the specific surface area of ​​the negative electrode material is 10 m 2 / g can be less.

[0026] In a negative electrode material for a secondary battery according to one embodiment, the ratio of the full width at half maximum (F D / F G ) can be greater than 1.5.

[0027] In a negative electrode material for a secondary battery according to one embodiment, the carbon coating layer may include a plurality of carbon nanoparticles.

[0028] In a negative electrode material for a secondary battery according to one embodiment, the carbon coating layer may include a dispersed phase including a plurality of carbon nanoparticles and a continuous phase physically bonding the dispersed phase and being made of carbon.

[0029] In a negative electrode material for a secondary battery according to one embodiment, the carbon coating layer may be included in an amount of 0.5 to 8 wt% of the total weight of the negative electrode material.

[0030] In a negative electrode material for a secondary battery according to one embodiment, the carbon coating layer may be derived from coal tar or petroleum residue.

[0031] In a negative electrode material for a secondary battery according to one embodiment, the D1 particle size of the negative electrode material is 0.8 to 5 ㎛, and D 10 / D1 can be 1 to 3.

[0032] In a negative electrode material for a secondary battery according to one embodiment, D of the negative electrode material 90 The particle size is 8.5 to 25 ㎛, D 99 / D 90 can be 1.1 to 3.

[0033] A secondary battery according to one embodiment of the present invention may include the negative electrode material for a secondary battery described above.

[0034] A negative electrode material for a silicon-based secondary battery according to one embodiment of the present invention can have a high initial capacity and excellent initial charge / discharge efficiency and lifespan characteristics.

[0035] A silicon-based secondary battery negative electrode material according to one embodiment of the present invention has uniform electrochemical properties at any location within a single negative electrode material particle, and further, can have uniform electrochemical properties between negative electrode material particles.

[0036] Figure 1 is a graph showing the Raman spectroscopy spectrum of a negative electrode material for a secondary battery according to an embodiment of the present invention.

[0037] Figure 2 is a graph showing the Raman spectroscopy spectrum of a negative electrode material for a secondary battery according to a comparative example.

[0038] Figure 3 is a graph showing a silicon Raman spectroscopy spectrum of a negative electrode material for a secondary battery according to one embodiment of the present invention.

[0039] Figure 4 is a graph of nitrogen adsorption and desorption isotherms of a silicon core of a negative electrode material for a secondary battery according to one embodiment of the present invention.

[0040] Figure 5 is a graph showing an infrared spectral spectrum of a negative electrode material for a secondary battery according to one embodiment of the present invention.

[0041] Hereinafter, preferred embodiments of the present invention will be described with reference to the attached drawings. However, the embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

[0042] In addition, the embodiments of the present invention are provided to more completely explain the present invention to a person having average knowledge in the relevant technical field.

[0043] The shape and size of elements in the drawing may be exaggerated for clearer explanation.

[0044] In describing the embodiments of the present invention, if a detailed description of a known technology related to the present invention is judged to unnecessarily obscure the gist of the present invention, such detailed description will be omitted. In addition, the terms described below are terms defined in consideration of their functions in the present invention, and these may vary depending on the intention or custom of the user or operator. Therefore, the definitions should be made based on the contents throughout this specification. The terminology used in the detailed description is only for the purpose of describing the embodiments of the present invention and should in no way be limiting. Unless clearly defined otherwise, expressions in the singular form include plural meanings.

[0045] In this description, expressions such as "including" or "having" are intended to indicate certain features, numbers, steps, operations, elements, portions or combinations thereof, and should not be construed to exclude the presence or possibility of one or more other features, numbers, steps, operations, elements, portions or combinations thereof other than those described.

[0046] Unless otherwise specified in the specification of the present invention, the % unit means weight %.

[0047] In this specification, terms such as 'top', 'upper part', 'top surface', 'bottom', 'lower part', 'bottom', 'side', etc. are based on the drawings, and in reality, they may vary depending on the direction in which the elements or components are arranged.

[0048] Additionally, throughout the specification, when we say that a part is 'connected' to another part, this includes not only cases where it is 'directly connected', but also cases where it is 'indirectly connected' with other elements in between.

[0049] Below, the present invention will be described in detail through each embodiment or example of the present invention. It should be noted that each embodiment or example described in this specification is not limited to a single embodiment or example, but may be combined with other embodiments or examples. Therefore, the citation of a claim in the patent claims is only an example of an embodiment, and the technical concept of the present invention should not be interpreted solely as a combination with the cited claim, and combinations with various claims also fall within the scope of the technical concept of the present invention.

[0050] In this specification, particle size distribution refers to a measurement using the laser diffraction method. To analyze the particle size distribution, the target powder is dispersed in a dispersion medium, then introduced into a laser diffraction particle size measuring device. When the particles pass through the laser beam, the difference in diffraction pattern according to particle size is measured to calculate the particle size distribution.

[0051] The present applicant discovered that in a silicon-based anode material having a carbon coating layer formed on a silicon-based oxide, the mechanical and electrochemical properties of the anode material are significantly affected by Raman spectral characteristics. Based on this discovery, the applicant further researched and found that in a silicon-based core-coated anode material, when the Raman spectral spectrum of the anode material satisfies a specific aspect and the nitrogen adsorption / desorption isotherm graph of the silicon-based core satisfies a specific behavior, the electrochemical properties of the anode material are significantly improved, thereby completing the present invention.

[0052] In the present invention, the negative electrode material for a secondary battery includes, but is not necessarily limited to, a negative electrode material for a lithium secondary battery. The negative electrode material of the present invention may also be utilized as an active material in secondary batteries such as sodium batteries, aluminum batteries, magnesium batteries, calcium batteries, and zinc batteries.

[0053] The negative electrode material according to the present invention includes a silicon-based core and a carbon coating layer positioned on the surface of the silicon-based core, and the ratio of intensities of the D band peak and the G band peak in the Raman spectroscopy spectrum of the negative electrode material (I D / I G ) is the ratio of the full width at half maximum (FWHM) of the D band and G band peaks (F D / F G ) is smaller than the full width at half maximum (FWHM) ratio (F D / F G ) is 1.3 or higher, and is characterized by Type Ⅱ behavior in the nitrogen adsorption / desorption isotherm graph of the silicon core.

[0054] Specifically, the D band peak intensity (I) in the Raman spectroscopy spectrum of the cathode material D ) is 1310 to 1380 cm -1 The maximum intensity of the peak located in the waveband region, and the intensity of the G band peak (I G ) in the same Raman spectroscopy analysis, 1560 to 1630 cm -1 It refers to the maximum intensity of a peak located in the wavenumber region. Although not necessarily limited to this, experimentally, the Raman spectroscopy spectrum may be measured using a Raman spectroscopy analyzer (WITec GmbH) at room temperature and in an air atmosphere using a laser with a wavelength of 532 nm.

[0055] The above full width at half maximum (FWHM) is the width of the spectrum measured at half the height of each spectral peak (D band and G band) measured from the baseline, after peak deconvolution of the D band and G band based on the baseline of the Raman spectral spectrum.

[0056] The infrared spectral spectrum may be obtained by Fourier transform infrared spectroscopy (FTIR). The infrared spectral spectrum includes a spectrum with the wavenumber of the irradiated infrared light as one axis and the transmittance according to the wavenumber of the light as the other axis. The transmittance along the other axis includes the transmittance having 100% transmittance when all light of a specific wavenumber irradiated is transmitted. The peaks on the FTIR spectrum may include peaks in the direction of decreasing transmittance.

[0057] The nitrogen adsorption / desorption isotherm graph of the above silicon core means an isotherm obtained by combining the isotherm of the nitrogen adsorption process (nitrogen adsorption isotherm) and the isotherm of the nitrogen desorption process (nitrogen desorption isotherm) obtained by nitrogen adsorption measurement. In the above isotherm, the nitrogen relative pressure (P / P0) is on the x-axis, and the nitrogen adsorption amount (cm 3 / g STP) is the y-axis, and the nitrogen adsorption / desorption isotherm can be measured using a BET surface area analyzer (Micromeritics, ASAP 2020 PLUS). The above Type Ⅱ behavior means that it is defined by the classification standardized by IUPAC (International Union of Pure and Applied Chemistry).

[0058] In this way, the silicon-based secondary battery anode material satisfying the above-described aspects in the Raman spectroscopy spectrum and nitrogen adsorption / desorption isotherm graph can effectively disperse stress caused by volume changes of silicon while maintaining excellent ionic conductivity by organically bonding the silicon-based core and carbon coating layer more than the conventional silicon-based secondary battery anode material known in the art. The silicon-based secondary battery anode material as described above can have overall improved capacity, lifespan, and charge / discharge performance.

[0059] In one embodiment, the infrared spectral spectrum of the cathode material is 1400 to 1625±5 cm-1 The area (A1) of the peak of the first wave number (n1) of the range is 1625±5 to 2100 cm -1 It may be smaller than the area (A2) of the peak of the second wave number (n2) of the range.

[0060] Infrared spectroscopy can be obtained by Fourier transform infrared spectroscopy (FTIR). In the infrared spectroscopy, the first and second wave numbers each represent the range of wave numbers, and the point where the first and second wave numbers are separated is 1625±5 cm. -1 can be defined as the position where peaks separate from each other in the vicinity of . For example, 1625 cm -1 1625 cm with one or more peaks in a smaller wavenumber range -1 The peak converges at 1625 cm -1 1625 cm, with one or more peaks in a larger wavenumber range. -1 When the peak converges at 1625 cm -1 can be defined as the position that separates the peak of the first wave and the peak of the second wave.

[0061] Peak areas can be derived by direct integration, for example, 1400 to 1625 cm -1 The area (A1) of the peak of the first wave number (n1) of the range is 1400 cm -1 Spectral position at 1625 cm -1 The spectral position in the range of 1625 to 2100 cm can be defined as the area of ​​the region enclosed by the curve of the infrared spectral spectrum and the straight line. Similarly, -1 The area (A2) of the peak of the second wave number (n2) of the range is 1625 cm -1 Location in and 2100 cm -1 The position in can be defined as a straight line drawn through the infrared spectral curve and the area of ​​the region closed by the straight line.

[0062] There is no particular limitation as long as the area (A1) of the peak of the first wave number (n1) in the infrared spectroscopy spectrum is smaller than the area (A2) of the peak of the second wave number (n2). In non-limiting terms, the ratio (A2 / A1) of the area (A1) of the peak of the first wave number (n1) to the area (A2) of the peak of the second wave number (n2) may be 2 or more or 3 or more, and specifically may be 2.5 to 10, and more specifically may be 3 to 7.

[0063] In one embodiment, the ratio of the intensities of the D band peak and the G band peak in the Raman spectroscopy spectrum (I D / I G ) is the ratio of the full width at half maximum of the intensity of the D band peak and the G band peak (F D / F G ) may be smaller than that. Specifically, the ratio of the above intensities (I D / I G ) may be less than 1.3, 1.25 or less, 1.2 or less, 1.15 or less, or 1.13 or less, and may be, but is not limited to, 0.5 or more. Specifically, it may be 0.5 or more and less than 1.3, 0.5 to 1.25, 0.6 to 1.2, or 0.7 to 1.15. In addition, the ratio of the full width at half maximum (F D / F G ) may be 1.3 or greater, 1.4 or greater, 1.5 or greater, or 1.7 or greater, and may be, but is not limited to, 2.5 or less. Specifically, it may be 1.3 to 2.5, 1.4 to 2.5, 1.5 to 2.5, 1.6 to 2.3, or 1.7 to 2.1.

[0064] In one embodiment, the ratio of the Raman intensities in the Raman spectral spectrum (I D / I G ) is 0.5 to 1.25 and the ratio of the full width at half maximum (F D / F G ) is 1.3 to 2.5, the ratio of Raman intensities (I D / I G ) is 0.6 to 1.2 and the ratio of the full width at half maximum (F D / FG ) is 1.5 to 2.1, or the ratio of the Raman intensities (I D / I G ) is 0.7 to 1.15 and the ratio of the full width at half maximum (F D / F G ) may satisfy 1.7 to 2.1 simultaneously.

[0065] In this way, the silicon-based secondary battery anode material satisfying the above-described aspects in the Raman spectroscopy spectrum and the infrared spectroscopy spectrum can have a silicon-based core and a carbon coating layer that are more organically bonded than silicon-based secondary battery materials known in the art, and can also have superior carbon film quality. Accordingly, the silicon-based secondary battery anode material according to the present invention can have significantly improved electrochemical characteristics, and thus can exhibit excellent initial charge / discharge efficiency, cycle characteristics, and lifespan characteristics.

[0066] In one embodiment, the full width at half maximum (F) of the G band peak G ) is 60 cm -1 Ideal, 80 cm -1 Ideal, 90 cm -1 Ideal, 95 cm -1 Ideal, 100 cm -1 It can be any height, but is not limited to 130 cm -1 It may be less than 60 to 130 cm. More specifically, it may be less than 60 to 130 cm. -1 , 80 to 120 cm -1 , 95 to 110 cm -1 It could be.

[0067] In one embodiment, the specific surface area of ​​the negative electrode material according to the present invention is 10 m 2 / g or less, specifically 5 m 2 / g or less, more specifically 0.5 to 5 m 2 / g may be. Accordingly, the negative electrode material for a secondary battery according to the present invention can suppress irreversible side reactions and reduce the adsorption of electrode binder, thereby having improved electrical characteristics.

[0068] The silicon-based core may contain silicon components in an elemental silicon state and silicon components in an oxide state, and the silicon component in an oxide state may mean the oxide state of silicon alone. Silicon oxide is SiO x (x is a real number greater than 0.1 and less than 2, specifically a real number greater than 0.3 and less than 1.8), and may include a first silicon oxide and a second silicon oxide having different x.

[0069] In one embodiment, the silicon-based core may include a silicon oxide matrix and silicon nanocrystals dispersed and embedded in the silicon oxide matrix. However, the present invention does not exclude an embodiment in which the silicon-based core includes only a silicon oxide matrix without substantially including silicon nanocrystals.

[0070] In one embodiment, the silicon-based core may comprise 1 to 70 wt %, 2 to 60 wt %, 5 to 50 wt %, or 10 to 50 wt % of silicon nanocrystals relative to the total weight of the silicon-based core, with the remainder comprising a silicon oxide matrix.

[0071] The above silicon oxide matrix may refer to a solid medium in which silicon nanocrystals are dispersed and incorporated, and may refer to a material that forms a continuum compared to the silicon nanocrystals that are dispersed in the negative electrode material. In the present specification, the matrix may refer to a material excluding silicon (Si) nanocrystals in the negative electrode material.

[0072] For example, silicon oxide contained in a silicon oxide matrix is ​​SiO y (y can be a real number less than 2, specifically, a real number between 0.1 and 1.8, and more specifically, a real number between 0.1 and 1.5).

[0073] The silicon oxide matrix may be crystalline, amorphous, or a composite phase in which crystalline and amorphous phases are mixed. Specifically, the matrix may be crystalline or a composite phase in which crystalline and amorphous phases are mixed. In addition, the silicon included in the silicon oxide matrix is ​​Si 1+ , Si 2+ , Si 3+ and Si 4+ It may include a silicon of a singer corresponding to one or more combinations selected from the group consisting of .

[0074] The silicon nanocrystals can have a size (diameter) that is typically defined as a nanocrystal. In practice, they can have a diameter of less than or equal to 100 nm, a diameter of less than or equal to 50 nm, a diameter of less than or equal to 20 nm, a diameter of less than or equal to 15 nm, and for example, can mean crystals having a diameter of from 1 to 20 nm, from 1 to 15 nm, or from 1 to 10 nm. The size of the silicon nanocrystals can be calculated by substituting the full width at half maximum of the Si (220) crystal plane measured by X-ray diffraction into the Scherrer equation.

[0075] The above carbon coating layer refers to a carbon film coated on the surface of a silicon core, which can protect the silicon core and suppress volume change of silicon of the silicon core, and can impart excellent conductivity and electrochemical properties despite having properties close to amorphous.

[0076] In one embodiment, the carbon coating layer may be an amorphous carbon layer. The amorphous carbon layer can stably wrap the surface of the core and prevent volume changes in the silicon.

[0077] In one embodiment, the carbon coating layer may be included in an amount of 0.5 to 8 wt%, specifically 0.5 to 6 wt%, of the total weight of the negative electrode material.

[0078] The thickness of the carbon coating layer is not particularly limited, but the average thickness of the carbon coating layer may be 1 to 200 nm, 1 to 150 nm, 1 to 100 nm, 2 to 50 nm, 3 to 30 nm, or 5 to 15 nm. Experimentally, the thickness of the carbon coating layer may be obtained by randomly measuring the thickness of the carbon coating layer at 10 or more locations, or practically 10 to 20 locations, using images obtained through a transmission electron microscope (TEM), a scanning transmission electron microscope (STEM), etc., and taking the average value. In the above range, the surface of the core can be stably wrapped while minimizing the electrical resistance component.

[0079] In one embodiment, the carbon coating layer may include a plurality of carbon nanoparticles. The carbon nanoparticles may be positioned at least partially in one or more regions selected from the interior and surface of the carbon coating layer.

[0080] Specifically, the carbon coating layer may be composed of a dispersed phase and a continuous phase. Within the carbon coating layer, a plurality of carbon nanoparticles may form a dispersed phase, and the dispersed phase may be physically bonded to form a continuous phase composed of carbon. Although the dispersed phase and the continuous phase are both composed of carbon, they may be distinguished as different phases within the carbon coating layer. For example, when observed through a scanning electron microscope (SEM), the dispersed phase may be visually identified in an image obtained from a fracture surface analysis of the negative electrode material.

[0081] Carbon nanoparticles may be primary particles of carbon, or secondary particles that are aggregates of primary particles, and the carbon coating layer may be provided with primary particles and secondary particles alone or in a mixture of primary particles and secondary particles.

[0082] Specifically, the carbon nanoparticles may be in a state where they are embedded in the carbon coating layer and in contact with the core, in a state where some of them are protruding from the surface of the carbon coating layer and in a state where some of them are embedded in the carbon coating layer and the remaining part is protruding from the surface of the carbon coating layer, or in a state where they are bound to the surface of the carbon coating layer.

[0083] In this way, a carbon coating layer containing carbon nanoparticles can improve the electrical conductivity of the externally exposed surface and suppress side reactions with the electrolyte. Furthermore, the inter-particle resistance (contact resistance) of the negative electrode material can be reduced, and stable and smooth electrical contact between the negative electrode material particles can be maintained.

[0084] The above carbon nanoparticles may be spherical or elliptical, but are not limited to a specific shape, and specifically may be spherical bead-shaped. The average particle diameter of the carbon nanoparticles is not particularly limited, but may be 2 nm to 1 μm, specifically 5 to 0.5 μm, and more specifically 5 to 200 nm. Such carbon nanoparticles are relatively coarse compared to the thickness of the carbon coating layer, and thus can provide stable contact between the negative electrode materials even when the volume of the negative electrode material changes due to silicon. At this time, the ratio of the area occupied by the carbon nanoparticles among the surface of the particle-shaped negative electrode material may be 30% or more, specifically 50% or more, and more specifically 70% or more and less than 100%. Experimentally, the ratio of the area occupied by carbon nanoparticles can be obtained by calculating the total surface area by using an image obtained through a transmission electron microscope (TEM) or a scanning electron microscope (SEM), assuming that the surface is formed by completely covering the core with a virtual film having the same thickness as the carbon coating layer without carbon nanoparticles, and then measuring the area occupied by carbon nanoparticles in the film (virtual film).

[0085] Preferably, the carbon coating layer may be derived from a liquid carbon precursor. The liquid carbon precursor may refer to a carbon precursor that is liquid at room temperature, for example, 25°C, and may be a polycyclic aromatic compound having an average molecular weight of 100 to 2,000 Da, specifically 100 to 1,000 Da, as measured by MALDI-TOF.

[0086] The above carbon precursor may be a compound having a polycyclic aromatic structure with three or more aromatic rings. Specifically, it may be a polycyclic aromatic structure composed of three to ten aromatic rings, but is not limited thereto.

[0087] As a non-limiting example, the liquid carbon precursor may be coal tar or petroleum residue, and more specifically, the liquid carbon precursor may be liquid coal tar.

[0088] The above liquid coal tar may refer to coal tar that is liquid in itself at room temperature (25°C) and atmospheric pressure (1 atm) without the aid of a chemical substance such as a solvent or the application of external energy such as heat.

[0089] Specifically, the liquid coal tar may have a specific gravity of 1.1 to 1.3 g / cc, specifically, 1.3 to 1.28 g / cc, and more specifically, 1.2 to 1.26 g / cc.

[0090] Additionally, the liquid coal tar may have an initial boiling point (IBP) of 50 to 70°C, 55 to 70°C, 60 to 70°C, or 65 to 70°C. In this case, the IBP may be measured according to ASTM D86.

[0091] The above-described liquid coal tar is advantageous not only because it can be uniformly coated on the surface of core particles, but also because it can easily penetrate into the internal pores of the core particles.

[0092] In one embodiment, the negative electrode material for a secondary battery according to the present invention can satisfy the following equation 1 based on a silicon Raman signal.

[0093] (Formula 1)

[0094] 1 > WN(Si) / WN(ref)

[0095] In Equation 1, WN(ref) is the center wavenumber of the Raman peak of bulk single crystal silicon, and WN(Si) is the center wavenumber of the Raman peak of silicon nanocrystals contained in the cathode material.

[0096] Experimentally, the Raman spectrum of silicon contained in the cathode material was obtained at room temperature (20 to 25°C), atmospheric pressure, with an excitation laser wavelength of 532 nm, a laser power of 0.5 mW, and a spectrometer resolution of 1 cm. -1 , it may be measured under the conditions of 1 g of cathode material and 15 s of detector exposure time.

[0097] In Equation 1, the ratio of the Raman peak center wavenumber of the silicon nanocrystals contained in the cathode material to the Raman peak center wavenumber of the bulk single crystal silicon is a parameter indicating the type and magnitude of the stress (residual stress) remaining in the silicon nanoparticles dispersed and embedded in the matrix.

[0098] In Equation 1, the term "bulk single-crystal silicon" should be interpreted to mean silicon having a size that substantially exhibits the properties of bulk single-crystal silicon. To provide a clear comparison standard and ensure ease of purchase, bulk single-crystal silicon may refer to a single-crystal silicon wafer having a thickness on the sub-mm order, specifically, a thickness of 0.4 to 0.7 mm.

[0099] In Equation 1, the fact that WN(Si) / WN(ref) is less than 1 means that the center wavenumber of the Raman peak of the silicon nanocrystals contained in the cathode material is shifted to a shorter wavenumber compared to bulk single crystal silicon, and means that the silicon nanocrystals have residual tensile stress.

[0100] In Equation 1, the Raman peak of silicon in bulk single crystal silicon and silicon nanocrystals, respectively, is 450 to 540 cm in the Raman spectrum of silicon. -1 Area, 480 to 530 cm -1 , 500 to 525 cm -1 Area, or 510 to 520 cm -1 It can mean a Raman peak located in the region. The central wavenumber of the peak, that is, the wavenumber corresponding to the center of the peak, can mean the wavenumber having the maximum intensity value at the peak. At this time, if two or more Raman peaks exist in the Raman Shift region described above, the peak with the highest intensity can correspond to the Raman peak of silicon in Equation 1, and if two or more Raman peaks overlap each other to form a twin peak shape, the wavenumber having the maximum intensity value in the twin peak with the higher intensity can correspond to the central wavenumber of the peak.

[0101] The full width at half maximum of the Raman peak of the silicon nanocrystals contained in the above-described negative electrode material may be larger than the full width at half maximum of the Raman peak of bulk single crystal silicon. The larger full width at half maximum value compared to bulk single crystal silicon may be due to the structure in which the silicon contained in the negative electrode material is dispersed and incorporated into the matrix in the form of ultrafine particles.

[0102] Specifically, the half-maximum width of the Raman peak of the silicon nanocrystals contained in the cathode material is 4 to 25 cm. -1 , 5 to 22 cm -1 , 6 to 20 cm -1 , 6 to 18 cm -1 or 8 to 15 cm -1It may be. At this time, the Raman peak of the silicon nanocrystals contained in the cathode material may mean a single peak rather than a deconvoluted peak.

[0103] The full width at half maximum (FWHM) of the Raman peak of the nanoparticle-like silicon contained in the above-mentioned negative electrode material may be larger than the full width at half maximum (FWHM) of the Raman peak of the bulk single crystal silicon. The larger FWHM value compared to the bulk single crystal silicon may be due to the structure in which the silicon contained in the negative electrode material is dispersed and embedded in the matrix in the form of ultrafine particles. Specifically, the full width at half maximum (FWHM) of the Raman peak of the nanoparticle-like silicon contained in the negative electrode material is 4 to 20 cm -1 , 6 to 20 cm -1 , 6 to 18 cm -1 , 6 to 16 cm -1 , 8 to 20 cm -1 , 8 to 18 cm -1 , 8 to 16 cm -1 , 10 to 20 cm -1 , 10 to 18 cm -1 , or 10 to 16 cm -1 It may be, but is not necessarily limited to, this.

[0104] As described above, the silicon core is SiO x(x is a real number greater than 0.1 and less than 2, specifically greater than 0.3 and less than 1.8) refers to silicon oxide, which may be undoped with metal. In general, a technology for doping a silicon oxide-based negative electrode material with a metal such as lithium or magnesium is known to suppress the generation of lithium oxide, which causes initial irreversibility during charge and discharge of a secondary battery. Metal-doped silicon oxide-based negative electrode materials can improve the initial charge and discharge efficiency by converting lithium oxide, which does not participate in the electrochemical reaction, into an irreversible phase, and can improve the cycle characteristics by reducing the size of silicon nanocrystals, and can make the silicon nanocrystals have generally uniform characteristics as the matrix is ​​converted to metal-silicon oxide. For example, the size, crystallinity, and stress characteristics of silicon nanocrystals can be more uniform and significantly improved in a metal-doped silicon oxide matrix than in a silicon oxide matrix.

[0105] In contrast, the negative electrode material for a secondary battery according to the present invention has a technical advantage in that the size of silicon nanocrystals can be controlled to be very small even though the material is not doped with metal, and the crystal and stress characteristics can be maintained at a level equivalent to that of a metal-doped silicon oxide matrix. As described above, the full width at half maximum (FWHM) of the Raman peak of the silicon nanocrystals contained in the negative electrode material exhibits a low value, so not only can the size of the silicon nanocrystals be controlled to be very small, but the stress applied to the silicon nanocrystals can also be uniformly controlled.

[0106] In one embodiment, the silicon-based core is randomly arranged at 10 different locations such that the difference between the maximum and minimum values ​​of the central wavenumber WN(Si) of the Raman peak of the silicon nanocrystal is 10 cm. -1 Below, 8 cm -1 Below, 6 cm -1 , 5 cm -1 Below and 1 cm -1 It can be 1 to 10 cm in diameter.-1 , 2 to 8 cm -1 , or 2 to 6 cm -1 It could be.

[0107] At this time, the standard deviation of the maximum and minimum values ​​of the central wave number WN(Si) of the Raman peak of the silicon nanocrystal is 5 cm. -1 Below, 3 cm -1 Below, 2 cm -1 Below, 1.5 cm -1 Below and 0.1 cm -1 It can be abnormal, 0.1 to 5 cm -1 , 0.1 to 3 cm -1 , 0.1 to 2 cm -1 , or 0.1 to 1.5 cm -1 It could be.

[0108] The small difference between the maximum and minimum values ​​indicates that the stress applied to the silicon nanocrystals contained in the cathode material is nearly constant and uniform. Furthermore, it implies that the magnitude of the residual tensile stress in all silicon nanocrystals dispersed in the silicon oxide matrix is ​​virtually identical.

[0109] In addition, as defined in the above equation 1, it means that most of the silicon nanocrystals dispersed in the silicon oxide matrix have residual tensile stress, and further, it means that the magnitude of the residual tensile stress in most of the silicon nanocrystals dispersed in the silicon oxide matrix is ​​substantially almost the same. As a specific example, the ratio of the residual tensile stress measured in the silicon nanocrystals present at different locations may be 80% or more, 90% or more, or 95% or more, and may be 90% to 100%, 95% to 100%, or 98% to 100%.

[0110] The negative electrode material for a secondary battery according to the present invention has uniform electrochemical characteristics at any location within a single negative electrode particle, and further, has uniform electrochemical characteristics between different negative electrode particles, thereby enabling excellent rate characteristics. Specifically, the negative electrode material for a secondary battery according to the present invention may have an average capacity retention rate of 90% or more, 91% or more, 93% or more, specifically 95% or more, and more specifically 98% or more within 3 to 25 charge and discharge cycles.

[0111] In addition, the initial charge / discharge efficiency of the negative electrode material according to the present invention may be 70% or more, 73% or more, or 74% or more, and the initial discharge capacity may be 1300 mAh / g or more, 1400 mAh / g or more, 1500 mAh / g or more, 1600 mAh / g, or 1700 mAh / g.

[0112] The negative electrode material for a secondary battery according to the present invention is provided in the form of particles. Specifically, the negative electrode material may be one or more particles selected from primary particles and secondary particles. That is, the negative electrode material may be primary particles, secondary particles, or particles comprising a mixture of primary and secondary particles. A primary particle may refer to a single particle, and a secondary particle may refer to an aggregate formed by coagulating two or more particles.

[0113] Average particle diameter of cathode material (D 50 ) is not particularly limited. The average particle diameter is the volume-based median diameter (D) calculated by laser diffraction method. 50 ) can mean volume criterion D 50 It means the particle diameter at the point where the cumulative volume % is 50% in the cumulative distribution curve (cumulative distribution curve) accumulated in order of particle diameter. Experimentally, D 50 The cumulative distribution curve including can be obtained by a conventional particle size analyzer using a laser diffraction method or a dynamic light scattering method.

[0114] D of cathode material 50 The value may be 1 μm to 20 μm, 2 μm to 18 μm, 3 to 15 μm or 5 to 15 μm.

[0115] At this time, the D1 particle size of the negative electrode material is 0.5 to 5 ㎛, 0.8 to 5 ㎛, 1.5 to 4.5 ㎛, or 2 to 4 ㎛, and D 10 / D1 can be 1 to 3, 1 to 2.5 or 1 to 2.3.

[0116] The above D1 diameter and D 10 As the value of / D1 satisfies the above conditions, the initial efficiency and output characteristics of the battery can be improved by improving the composite density of the electrode without causing excessive side reactions with the electrolyte.

[0117] Also, D of the negative electrode material 90 The particle size is 8.5 to 25 ㎛ or 9 to 21 ㎛, D 99 / D 90 may be 1 to 3.5, 1.1 to 3, or 1.2 to 2.1.

[0118] Above D 90 Entry and D 99 / D 90 As the value satisfies the above conditions, an appropriate balance can be achieved between the composite density of the electrode and the expansion of the electrode, thereby improving the output characteristics and life characteristics of the battery.

[0119] Average particle diameter of cathode material (D 50 ) as defined above, D1, D 10 , D 90 , D 99 refers to the particle size at points where the cumulative volume % is 1, 10, 90 and 99 volume %, respectively, on the cumulative distribution curve based on volume.

[0120] The negative electrode material as described above is a particle having a relatively uniform particle size distribution, and when forming a negative electrode composite layer, stable conductivity is secured while reducing the diffusion time of metal ions involved in charge and discharge, for example, lithium ions, thereby exhibiting improved and more stable charge and discharge cycle characteristics.

[0121] The negative electrode material for a secondary battery according to the present invention can be obtained through the steps of S1) manufacturing a silicon-based core and S2) forming a carbon coating layer.

[0122] S1) The silicon core manufacturing step is not particularly limited as long as it is a method for manufacturing silicon particles conventionally used as an active material, and is a commercialized silicon oxide, SiO. x (x is a real number greater than 0.1 and less than 2, specifically a real number greater than 0.3 and less than 1.8) can be obtained and used, or it can be manufactured by vaporizing Si and SiO2.

[0123] For a specific example, step S1) comprises: a) a step of mixing metal silicon powder (Si) and silicon dioxide powder (SiO2) to obtain a mixed raw material; b) a step of molding the mixed raw material into pellets; c) a step of heating and vaporizing the pellets under vacuum conditions to obtain a gaseous silicon oxide gas; d) a step of condensing the gaseous silicon oxide gas on a heated collecting plate to obtain silicon oxide (SiO x ) may include a step of obtaining a silicon-based core.

[0124] In the above step a), the Si: SiO2 mole ratio may be mixed at 1:0.1 to 7, 1:0.5 to 5, 1:0.5 to 3, 1:0.7 to 2, or 1:0.9 to 1.5. The mixing may be performed by homogeneously mixing Si and SiO2 after they are introduced into a powder mixer.

[0125] The above step b) is a step of pelletizing the mixed raw material, and can be performed, for example, by molding the mixed raw material in a pellet mold. The above step c) is a step of vaporizing the pellet, and the temperature during heating and vaporization can be performed at 1,000 to 1,700°C, specifically 1,200 to 1,600°C, and more specifically 1,300 to 1,500°C, and can be performed under reduced pressure conditions. The above step d) is a step of condensing the gaseous silicon oxide gas to obtain particulate silicon oxide, and can be performed by maintaining the temperature of the condensing plate at 300 to 1,200°C, specifically 400 to 1,000°C.

[0126] In one embodiment, step S1) may further include a step of crushing the obtained silicon core after step d). The crushing may be performed using a crushing device such as a jet mill, and after crushing at a high rotational speed, the crushed silicon core may be recovered through a cyclone. Through crushing, the center particle diameter (D) of the silicon core may be reduced. 50 ) and distribution by appropriately controlling the center particle diameter (D) of the cathode material. 50 ) and distribution can be easily controlled.

[0127] The above step S2) is a step of forming a carbon coating layer on the silicon-based core, which is a silicon oxide manufactured in step S1).

[0128] Step S2) comprises the steps of: f) mixing a liquid carbon precursor into the silicon oxide obtained in step S1) to obtain a mixture; and g) carbonizing the mixture.

[0129] In the above step f), the mixing ratio of the silicon oxide and the liquid carbon precursor is not particularly limited. For example, the mixing ratio of silicon oxide:carbon precursor may be mixed at a weight ratio of 20 to 0.5:1, specifically 15 to 1:1. The liquid carbon precursor to be introduced may advantageously be a sulfur-containing carbon precursor, and may be coal tar or petroleum residue in a liquid state at room temperature as described above. In the above step f), the mixing time may be appropriately adjusted in proportion to the amount of the mixture to be mixed, and may be mixed at a linear speed of 0.5 to 40 m / s, specifically 0.8 to 30 m / s, but is not limited thereto.

[0130] The above step g) is a step of carbonizing the mixture, and is not particularly limited as long as it is a method capable of carbonizing a carbon precursor to form a carbon coating layer on silicon oxide. Specifically, the carbonization may be performed at a temperature of 700 to 1,500°C, specifically 800 to 1,200°C, for 0.5 to 3 hours, specifically 0.6 to 2 hours.

[0131] The carbonization in the above step g) may be performed as a multi-stage carbonization step. Specifically, the carbonization may be performed in n carbonization steps (n is a natural number greater than 1). As a non-limiting example, when n is 3, the carbonization may include a step of first carbonization under the first temperature condition after the temperature is raised to reach a first temperature condition, a step of second carbonization under the second temperature condition after reaching a second temperature condition, and a step of third carbonization under the third temperature condition after reaching a third temperature condition. The first to third temperatures may all have different values, or the two temperatures may have the same value, but the three temperatures do not all have the same value. The negative electrode material manufactured in the above step g) may be naturally cooled from room temperature (20±5°C) to room temperature.

[0132] In one embodiment, after step g), a step of crushing the obtained negative electrode material may be further included.

[0133] The above-mentioned disintegration can be performed through various mechanical means, and the thickness and properties of the carbon coating layer can be uniformly controlled by applying a mechanical shear force in a device such as a pin mill crusher, and at the same time the center particle diameter (D) of the negative electrode material 50 ) and distribution can be easily controlled. The above disintegration step may not be performed when the content of carbon precursor is low compared to silicon oxide. However, when the content of carbon precursor is high compared to silicon oxide, performing the disintegration step further may be preferable because the cycle characteristics and life characteristics can be improved.

[0134] The present invention provides a negative electrode containing the above-described negative electrode material. The negative electrode may be an negative electrode for a secondary battery, specifically, an negative electrode for a lithium secondary battery. The negative electrode may include a current collector and a negative electrode composite layer positioned on at least one surface of the negative electrode current collector and containing the above-described negative electrode material.

[0135] According to one embodiment, the negative electrode composite layer including the negative electrode material may further include a carbon-based negative electrode active material. The carbon-based negative electrode active material may be at least one selected from artificial graphite, natural graphite, and hard carbon, but the present invention is not limited thereto.

[0136] For example, the weight ratio of the negative electrode material: carbon-based negative electrode active material included in the negative electrode composite layer according to one embodiment may be 1:99 to 99:1, specifically 5:95 to 95:5, more specifically 5:95 to 50:50, and even more specifically 5:95 to 20:80.

[0137] The above-described negative electrode for a secondary battery can be manufactured by coating and drying a slurry containing the negative electrode material, binder, conductive material, and solvent according to the above-described embodiments on a negative electrode current collector. Methods for manufacturing negative electrodes are known in the art, and known methods for manufacturing negative electrodes can be used without limitation.

[0138] The above conductive material may be, for example, a carbon-based conductive material such as carbon black, ultrafine graphite particles, acetylene black, graphene, carbon nanotubes, or carbon nanofibers, but is not limited thereto.

[0139] The above binder may include one or a combination of two or more selected from the group consisting of styrene-butadiene rubber (SBR), fluorine rubber, ethylene-propylene rubber, butyl acrylate rubber, butadiene rubber, isoprene rubber, acrylonitrile rubber, acrylic rubber, silane rubber, polyacrylic acid (PAA), a copolymer including an acrylic acid structural unit, polyvinyl alcohol (PVA), and a copolymer including a vinyl alcohol structural unit. Specifically, the binder may be a copolymer including polyacrylic acid (PAA) or an acrylic acid structural unit.

[0140] The present invention provides a secondary battery including the above-described negative electrode.

[0141] A secondary battery according to one embodiment may be a lithium secondary battery, and the lithium secondary battery may include a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte.

[0142] The above positive electrode may include a positive electrode current collector and a positive electrode composite layer positioned on at least one surface of the positive electrode current collector.

[0143] The cathode composite layer includes a cathode material as a main component and may include, for example, a Li compound including one or more metals selected from the group consisting of Ni, Co, Mn, Al, Cr, Fe, Mg, Sr, V, La, and Ce and one or more non-metallic elements selected from the group consisting of O, F, S, and P. The cathode composite layer may include cathode material particles having a size of 0.01 μm to 200 μm and may be appropriately selected depending on the required characteristics of the battery.

[0144] The above-described positive electrode can be manufactured by coating and drying a slurry containing the positive electrode material, binder, conductive material, and solvent as described above on a positive electrode current collector. Methods for manufacturing electrodes are known in the art, and known methods for manufacturing electrodes can be used without limitation.

[0145] The above conductive material may include, but is not limited to, carbon-based conductive materials such as carbon black, ultrafine graphite particles, acetylene black, graphene, carbon nanotubes, or carbon nanofibers, or nano-metal particle paste.

[0146] The positive electrode current collector serves to support the positive electrode composite layer. Examples of positive electrode current collectors that can be used include, but are not limited to, aluminum foil, nickel foil, or a combination thereof.

[0147] The separator above separates the positive and negative electrodes and provides a passage for lithium ions, and any separator commonly used in lithium secondary batteries can be used. That is, a separator having high lithium mobility for ion movement of the electrolyte and excellent electrolyte moisture retention capacity can be used. The separator may be selected from, for example, glass fiber, polyester, polyethylene, polypropylene, polytetrafluoroethylene, or a combination thereof, and may be in the form of a non-woven fabric or a microporous membrane. Meanwhile, when a solid electrolyte is used as the electrolyte, a conventional separator may not be included, and the solid electrolyte may be replaced with the separator and serve as both.

[0148] A lithium secondary battery may be first assembled into an electrode assembly comprising a positive electrode, a negative electrode, and a separator positioned between the positive electrode. The electrode assembly is wound or folded and housed in a battery case. The battery case may have a cylindrical, square, pouch-shaped, coin-shaped, or other shape. An electrolyte may be injected into the battery case and sealed to complete the lithium secondary battery.

[0149] As the electrolyte injected into the lithium secondary battery, an electrolyte that conducts active ions involved in charging and discharging of the battery, for example, lithium ions, may be selected, such as a non-aqueous electrolyte or a solid electrolyte.

[0150] The above non-aqueous electrolyte may include a lithium salt and an organic solvent. The lithium salt may include, for example, anions 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 - It can be any one selected from the group consisting of .

[0151] As the organic solvent, any one or a combination of two or more solvents commonly used in electrolytes for lithium secondary batteries can be used without limitation, and for example, any one selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), methylpropyl carbonate, dipropyl carbonate, dimethylsulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite, and tetrahydrofuran can be used.

[0152] The above solid electrolyte may be, for example, a gel polymer electrolyte in which an electrolyte is impregnated into a polymer electrolyte such as polyethylene oxide or polyacrylonitrile, or an inorganic solid electrolyte such as LiI or Li3N.

[0153] Meanwhile, the secondary battery according to one embodiment may be a half battery.

[0154] A half-cell may be a cell comprising: a negative electrode including a negative electrode current collector and a negative electrode material positioned on at least one surface of the current collector according to one embodiment; a counter electrode being a metallic lithium foil; a separator interposed between the negative electrode and the counter electrode; and an electrolyte. For example, the electrolyte may be a mixture of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1:1 in which LiPF6 is dissolved at a concentration of 1 M.

[0155] The negative electrode material according to the present invention is not limited to lithium secondary batteries, and can also be used as an active material in secondary batteries such as sodium batteries, aluminum batteries, magnesium batteries, calcium batteries, and zinc batteries.

[0156] The present invention also provides a power supply comprising a secondary battery including a cathode material according to one specific embodiment. Examples of the power supply include, but are not limited to, a battery module, a battery pack, or an ESS (Energy Storage System).

[0157] Hereinafter, the present invention will be described in detail through examples. However, it should be noted that the examples described below are intended only to illustrate and concretize the present invention and are not intended to limit the scope of the invention. This is because the scope of the invention is determined by the matters set forth in the patent claims and matters reasonably inferred therefrom.

[0158]

[0159] <Example 1>

[0160] 1) Silicon oxide (SiO x ) manufacturing

[0161] Powdered Si and SiO2 were added to a powder mixer in a molar ratio of 1:1, mixed homogeneously to produce a mixed raw material, and then the mixed raw material was molded through a mold to produce pellets.

[0162] 26 kg of pellets were placed in a crucible in a vacuum chamber of 0.1 torr or less, heated to 1,400°C to vaporize, and then condensed onto a collecting plate maintained at 800°C (± 25°C) to form solid silicon oxide (SiO x ) was obtained. The obtained solid silicon oxide was coarsely pulverized through a pulverizer and then finely pulverized through an air jet mill to obtain a center particle size (D 50 ) Silicon oxide (SiO) in fine powder form with a diameter of 5.6 ㎛ x ) was obtained.

[0163] 2) Formation of carbon coating layer

[0164] As a liquid carbon precursor, coal tar (specific gravity = 1.1-1.3 g / cc, carbonization yield of approximately 25% when carbonized at 900℃) in a liquid state at room temperature, which is produced during the dry distillation of raw coal in a steel mill, was used.

[0165] The fine powder silicon oxide obtained in 1) and coal tar were added to a planetary mixer maintained at 37°C (±3°C) at a weight ratio of 10:1 and mixed at a linear speed of 0.6 m / s for 1 hour to obtain a mixture. After that, 5 kg of the mixture was placed in a graphite crucible, and after reaching 900°C in a nitrogen atmosphere, 900°C was maintained for 120 minutes. Then, the inside of the crucible was heated again to 930°C and maintained at 930°C for 30 minutes. After naturally cooling the inside of the crucible to 900°C, 900°C was maintained for 30 minutes. After that, the inside of the crucible was naturally cooled to room temperature (20±5°C) to manufacture a particle-shaped negative electrode material. The specific surface area (SSA, m) of the negative electrode material 2 / g) was measured through BET analysis by nitrogen gas adsorption using a surface area measuring device (Micromeritics, ASAP 2020 PLUS), and the average particle diameter was measured using a laser diffraction particle size measuring device (Microtrac S3500), and the results are shown in Table 1 below.

[0166] <Example 2>

[0167] In the above Example 1, the negative electrode material was manufactured in the same manner as in Example 1, except that the temperature reached by the graphite crucible was changed when forming the carbon coating layer in step 2). Specifically, after the mixture was introduced into the graphite crucible and reached 950°C, it was maintained at 950°C for 120 minutes, then the inside of the crucible was heated again to reach 980°C, and then 980°C was maintained for 30 minutes, and finally, after naturally cooling the inside of the crucible to 950°C, it was maintained at 950°C for 30 minutes.

[0168] <Example 3>

[0169] In the above Example 1, the negative electrode material was manufactured in the same manner as in Example 1, except that the temperature reached by the graphite crucible was changed when forming the carbon coating layer in step 2). Specifically, the graphite crucible containing the mixture was heated to 1000°C, maintained at 1000°C for 120 minutes, then the inside of the crucible was heated again to 1030°C, maintained at 1030°C for 30 minutes, and finally, the inside of the crucible was naturally cooled to 1000°C, and then maintained at 1000°C for 30 minutes.

[0170] <Example 4>

[0171] In the above Example 1, when the silicon oxide and coal tar in the form of fine powder obtained in 1) were introduced into a mixer, a weight ratio of silicon oxide:coal tar was introduced as 5:1, and a negative electrode material was manufactured in the same manner as in Example 1.

[0172] <Example 5>

[0173] In the above Example 4, the manufactured particle-shaped negative electrode material was fed into an ACM (Automatic Classification Mill) to obtain an average particle diameter (D 50 ) was crushed to 5.8 μm, and the negative electrode material was manufactured in the same manner as in Example 1.

[0174] <Example 6>

[0175] In the above Example 1, when forming a carbon coating layer in step 2), after the mixture was introduced into the graphite crucible and reached 950°C, the temperature was maintained at 950°C for 40 minutes, then the inside of the crucible was heated again to reach 980°C, and then 980°C was maintained for 10 minutes, and finally the inside of the crucible was naturally cooled to 950°C and then 950°C was maintained for 10 minutes, except that the negative electrode material was manufactured in the same manner as Example 1.

[0176] <Example 7>

[0177] In Example 1, a negative electrode material was manufactured in the same manner as in Example 1, except that the temperature of the graphite crucible was kept constant when forming the carbon coating layer in step 2). Specifically, the graphite crucible containing the mixture was allowed to reach 900°C and then maintained for 1 hour.

[0178] <Comparative Example 1>

[0179] In the above Example 1, in step 2), silicon oxide (SiO x ) A cathode material was manufactured in the same manner as in Example 1, except that 50 g of the powder was charged into a thermal CVD device maintained at 900°C, and methane and argon were continuously supplied into the device at 1 L / min each to perform carbon deposition for 1 hour.

[0180] Comparative Example 2

[0181] In the above Example 1, in step 2), silicon oxide (SiO x ) A cathode material was manufactured in the same manner as in Example 1, except that 50 g of powder was charged into a thermal CVD device maintained at 950°C, and methane and argon were continuously supplied into the device at 1 L / min each to perform carbon deposition for 1 hour.

[0182] Comparative Example 2

[0183] In Comparative Example 1, the negative electrode material was manufactured in the same manner as in Example 1, except that carbon deposition was performed for 3 hours.

[0184]

[0185] It was confirmed that the negative electrode material according to the present invention had a smaller specific surface area in most cases compared to the comparative examples, and in particular, the negative electrode material according to Examples 1 to 4 had a specific surface area of ​​2 m 2 / g was confirmed to be less than.

[0186] [Measurement of cathode material properties]

[0187] 1. Raman spectroscopy

[0188] Raman spectroscopy spectra were measured at five different random locations of the cathode materials according to the examples and comparative examples using μ-Raman (equipment name: XperRam C, Nanobase, Korea) under the following analysis conditions, and are shown in Figs. 1 and 2, and the D band intensity (I) of the Raman spectroscopy spectra D ) and the intensity of the G band (I G ), their intensity ratio (I D / I G ) and the ratio of the full width at half maximum (FWHM) of the D band and G band peaks (F D / F G ) were calculated and recorded in Table 2 below. In addition, the full width at half maximum (FWHM) of the D band and G band peaks were recorded in Table 3 below. In addition, the silicon Raman signals of the negative electrode materials according to the examples and comparative examples were measured at five different random locations of the negative electrode material, and recorded in Fig. 3 and Table 4 below.

[0189] Analysis conditions: Laser wavelength 532 nm, laser power 0.5 mW, spectrometer resolution 1 cm -1 , 1 g of powdered cathode material, detector exposure time 15 sec.

[0190]

[0191]

[0192]

[0193] Referring to FIGS. 1 and 2 and Tables 2 and 3 above, the negative electrode material according to the embodiment has an average intensity ratio (I) of the D band peak and the G band peak. D / I G )go The ratio of the average full width at half maximum (F D / F G ) and it was confirmed that the average full width at half maximum (FWHM) was 1.3 or higher.

[0194] Also, referring to Table 3, the average full width at half maximum (FWHM) of the G band is 60 cm. -1 I was able to confirm that it was abnormal.

[0195] In addition, referring to FIG. 3 and Table 4, it was confirmed that the negative electrode material according to one embodiment satisfies the deviation of the central wavenumber of the Raman peak of the silicon nanocrystals being less than 3, and the difference between the maximum and minimum values ​​of the central wavenumber of the Raman peak of the silicon nanocrystals being less than 4. On the other hand, it was confirmed that the negative electrode material according to the comparative example is generally heterogeneous, with the deviation of the central wavenumber of the Raman peak of the silicon nanocrystals being 3 or more, and the difference between the maximum and minimum values ​​of the central wavenumber of the Raman peak of the silicon nanocrystals being 10 or more.

[0196] 2. Nitrogen adsorption / desorption isotherm

[0197] Nitrogen adsorption / desorption isotherms of silicon cores according to the examples and comparative examples were obtained using a BET surface area analyzer (Micromeritics, ASAP 2020 PLUS). The nitrogen adsorption / desorption isotherm measurement results according to the examples and comparative examples are disclosed in Table 5 and Figure 4 below.

[0198]

[0199] Referring to Table 5 and Figure 4 above, the example was found to have Type Ⅱ behavior in the nitrogen adsorption / desorption isotherm graph.

[0200] 3. Infrared spectroscopy

[0201] The FTIR of the negative electrode materials according to the above examples and comparative examples was measured using a Fourier transform infrared spectroscopy (FTIR), and the results are shown in Fig. 5. The ratio (A2 / A1) of the area of ​​the peak of the first wave number (A1) and the area of ​​the peak of the second wave number (A2) for each example and comparative example is shown in Table 6 below.

[0202]

[0203] The examples confirmed that the area of ​​A2 is larger than the area of ​​A1, and the ratio (A2 / A1) of the area of ​​the peak of the first wave number (A1) and the area of ​​the peak of the second wave number (A2) is 2 or more.

[0204] Battery manufacturing

[0205] The final anode powder was used as an active material, and the active material:conductive material (carbon black):CMC (Carboxymethyl cellulose):SBR (Styrene Butadiene Rubber) was mixed in a weight ratio of 8:1:0.5:0.5, applied to a 17 ㎛ thick copper foil, and dried at 90℃ for 40 minutes. After drying, it was stamped into a diameter of 14 mm, and a 16 mm diameter metallic lithium was used as a counter electrode, and an 18 mm diameter separator was sandwiched between them to fill the electrolyte to manufacture a CR2032 coin-type half-cell. The electrolyte was prepared by dissolving 1 M LiPF6 in a solvent containing a 1:1 volume ratio of EC (Ethylene carbonate) / DEC (Diethyl carbonate), and using 3 wt% FEC (fluoroethylene carbonate) as an additive.

[0206] Battery Performance Evaluation

[0207] The Martian process was performed by charging (lithiating) the manufactured battery to 0.005 V with a constant current of 0.1 C, charging at a constant voltage of 0.005 V until it reached 0.01 C, discharging (delithiating) to 1.5 V with a constant current of 0.1 C (first martian step), charging (lithiating) again to 0.005 V with a constant current of 0.1 C, charging at a constant voltage of 0.005 V until it reached 0.01 C, and discharging (delithiating) to 1.0 V with a constant current of 0.1 C (second martian step).

[0208] The half-cells on which the formation process was performed were charged (lithiated) to 0.005 V with a constant current of 0.5 C, charged at a constant voltage of 0.005 V until 0.05 C was reached, and then discharged (de-lithiated) to 1.0 V with a constant current of 0.5 C to evaluate the charge-discharge cycle characteristics, and the discharge capacity retention rate according to the charge-discharge cycle (total of 30 cycles) was evaluated. The discharge capacity (initial capacity) of the first charge-discharge cycle and the initial efficiency of the first charge-discharge cycle were measured and are shown in Table 7 below. Capacity retention rate ((C 25 / C3)×100, C 25 is the 25th charge / discharge cycle, and C3 is the discharge capacity at the 3rd charge / discharge cycle.) are also shown in Table 7 below.

[0209]

[0210] It was confirmed that the negative electrode material according to the example had excellent electrochemical properties compared to the comparative example, with an initial discharge capacity of 1700 mAh / g or more, an initial efficiency of 74% or more, and a charge / discharge capacity retention rate (rate characteristic) of 92% or more.

[0211] As described above, the present invention has been described with specific details and limited examples and drawings, but these are provided only to help a more general understanding of the present invention, and the present invention is not limited to the above examples, and those skilled in the art to which the present invention pertains can make various modifications and variations based on this description.

Claims

1. A silicon-based core; and a carbon coating layer positioned on the surface of the silicon-based core; The ratio of the intensities of the D band peak and the G band peak in the Raman spectral spectrum (I D / I G ) is the ratio of the full width at half maximum (FWHM) of the D-band and G-band peaks (F D / F G ) is smaller than the full width at half maximum (FWHM) ratio (F D / F G ) is 1.3 or higher, A negative electrode material for a secondary battery having Type II behavior in the nitrogen adsorption / desorption isotherm graph of the above silicon core.

2. In paragraph 1, In the infrared spectroscopy spectrum of the above cathode material, 1400 to 1625±5 cm -1 The peak area (A1) of the first wave number (n1) of the range is 1625±5 to 2100 cm -1 A negative electrode material for a secondary battery, the area (A2) of the peak of the second wave number (n2) of the range being smaller.

3. In paragraph 2, A negative electrode material for a secondary battery, wherein the ratio (A2 / A1) of the area (A1) of the peak of the first wave number (n1) and the area (A2) of the peak of the second wave number (n2) is 2 or more.

4. In paragraph 1, The ratio of the above intensities (I D / I G ) is less than 1.3, a negative electrode material for secondary batteries.

5. In paragraph 1, The full width at half maximum (F) of the above G band peak G ) is 60 cm -1 Ideal, negative electrode material for secondary batteries.

6. In paragraph 1, The above silicon core A negative electrode material for a secondary battery, comprising a matrix comprising silicon oxide, and silicon nanocrystals dispersed and incorporated in the matrix.

7. In paragraph 6, A negative electrode material for a secondary battery, satisfying Equation 1 below based on a silicon Raman signal. (Formula 1) 1 > WN(Si) / WN(ref) (In Equation 1, WN(ref) is the central wavenumber of the Raman peak of bulk single crystal silicon, and WN(Si) is the central wavenumber of the Raman peak of the silicon nanocrystals contained in the cathode material.) 8. In paragraph 7, A negative electrode material for a secondary battery, wherein the full width half maximum (FWHM) of the silicon Raman peak of the nanocrystals contained in the negative electrode material is larger than the FWHM of the Raman peak of bulk single crystal silicon.

9. In paragraph 7, The full width half maximum (FWHM) of the Raman peak of the nanoparticle silicon contained in the above cathode material is 4 to 20 cm -1 Anode material for secondary batteries.

10. In paragraph 7, The above silicon core is randomly selected at 10 different locations, and the difference between the maximum and minimum values ​​of the central wavenumber WN(Si) of the Raman peak of the silicon nanocrystal is 5 cm. -1 Below, negative electrode material for secondary batteries.

11. In paragraph 1, The specific surface area of ​​the above cathode material is 10 m 2 / g or less, negative electrode material for secondary batteries.

12. In paragraph 1, The ratio of the above half-width (F D / F G ) is a negative electrode material for secondary batteries with a value of 1.5 or higher.

13. In paragraph 1, A negative electrode material for a secondary battery, wherein the carbon coating layer comprises a plurality of carbon nanoparticles.

14. In paragraph 13, A negative electrode material for a secondary battery, wherein the carbon coating layer comprises a dispersed phase including a plurality of carbon nanoparticles and a continuous phase physically bonding the dispersed phase and made of carbon.

15. In paragraph 1, A negative electrode material for a secondary battery, wherein the carbon coating layer is included in an amount of 0.5 to 8 wt% of the total weight of the negative electrode material.

16. In paragraph 1, A negative electrode material for a secondary battery, wherein the carbon coating layer is derived from coal tar or petroleum residue.

17. In paragraph 1, The D1 particle size of the above cathode material is 0.8 to 5 ㎛, and D 10 / D1 is 1 to 3, negative electrode material for secondary batteries.

18. In paragraph 1, D of the above cathode material 90 The particle size is 8.5 to 25 ㎛, D 99 / D 90 Silver 1.1 to 3, negative electrode material for secondary batteries.

19. A secondary battery comprising a negative electrode material for a secondary battery according to any one of claims 1 to 18.

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