Lithium silicon oxide, negative electrode comprising same, and lithium secondary battery comprising same

Abstract

The present invention relates to a lithium silicon oxide exhibiting suppressed gas generation when applied to an aqueous slurry, a negative electrode comprising the same, and a lithium secondary battery comprising the negative electrode, and a lithium silicon oxide having peaks in which 2 [theta] is 23.8 + / -0.5 DEG, 24.3 + / -0.5 DEG, and 24.7 + / -0.5 DEG in an XRD pattern measured using a non-monochromatized CuK [alpha] ray and satisfying mathematical formula 1, a negative electrode including the same, and a lithium secondary battery including the negative electrode.

Description

Technical Field

[0001] Cross - reference to related applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2023-0075096, filed with the Korean Intellectual Property Office on June 12, 2023, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0004] The present invention relates to a lithium silicon oxide that exhibits suppression of gas generation when applied to an aqueous slurry, a negative electrode including the same, and a lithium secondary battery including the negative electrode. Background Art

[0005] Recently, as the application fields of lithium secondary batteries have rapidly expanded to power storage supply for large-area devices (such as automobiles and power storage devices) and power supply for electronic devices (such as electrical devices, electronic devices, communication devices, and computer devices), the demand for high-capacity, high-output, and high-stability lithium secondary batteries has been increasing.

[0006] A lithium secondary battery is generally manufactured in such a manner that a slurry in which a positive electrode material capable of intercalating and deintercalating lithium ions and a negative electrode material or a negative electrode material capable of absorbing and desorbing lithium ions, and optionally a binder and a conductive material are mixed is applied to each of a positive electrode current collector and a negative electrode current collector, and the solvent is removed by heat or the like to manufacture a positive electrode and a negative electrode, and the positive electrode and the negative electrode are stacked on both sides of a separator to form an electrode current collector having a predetermined shape, and then the electrode current collector and a non-aqueous electrolyte are inserted into a battery case.

[0007] Graphite-based negative electrode materials are typical negative electrode materials that maintain excellent structural stability even during intercalation and deintercalation of lithium and thus exhibit a stable capacity retention rate during long-term cycling, but this material is limited by a low theoretical capacity of 350 mAh / g for LiC6 and is considered insufficient to meet the current demand for high-energy and high-power materials. In contrast, silicon-based negative electrode materials such as silicon or silicon oxide provide a low reduction potential when paired with lithium, are abundant in reserves, and have a theoretical capacity that is approximately 10 times that of graphite (2700 mAh / g to 4200 mAh / g for Li 4.4 Si) and thus have become the focus of negative electrode materials for next-generation lithium secondary batteries. However, despite these advantages, silicon-based negative electrodes consume approximately three times as much lithium as graphite-based negative electrodes, and when a lithium secondary battery provided with a silicon-based negative electrode material is charged and discharged, a large amount of lithium inserted into the negative electrode during the initial charging process cannot return to the positive electrode due to volume expansion and surface side reactions, thereby causing a large initial irreversible capacity.

[0008] In addition, particularly for silicon oxide (SiOx) particles, various methods such as Mg doping or prelithiation of silicon oxide particles with Li have been explored to improve the initial efficiency (which is hindered by the irreversible reaction of Li ions). However, in the aqueous method of preparing the negative electrode slurry using this material, the lithium compound formed within the prelithiated silicon oxide particles reacts with H2O, generating LiOH as a by - product, and this causes a decrease in the slurry viscosity, hydrogen generation, and deterioration of the slurry coating characteristics, resulting in poor adhesion between the negative electrode material layer and the current collector and volume expansion.

[0009] Therefore, there is a need to develop a negative electrode material that exhibits excellent initial capacity and capacity retention rate, has a small viscosity change when preparing the negative electrode material slurry by the aqueous method, suppresses hydrogen generation, and suppresses volume expansion during charging and discharging of the negative electrode using this negative electrode material.

[0010] [Prior Art Documents]

[0011] [Patent Documents]

[0012] (Patent Document 1) KR10 - 2014 - 0091388A Summary of the Invention

[0013] Technical Problem

[0014] The present invention aims to overcome the limitations of the prior art. Therefore, one aspect of the present invention provides a lithium silicon oxide that can be used as a negative electrode material, which has excellent initial capacity and capacity retention rate, has a minimum viscosity change during slurry preparation by the aqueous method, and suppresses hydrogen generation.

[0015] Another aspect of the present invention provides a negative electrode containing the lithium silicon oxide.

[0016] Furthermore, another aspect of the present invention provides a lithium secondary battery including the negative electrode.

[0017] Technical Solution

[0018] To solve the above tasks, the present invention provides a lithium silicon oxide, a negative electrode containing the same, and a lithium secondary battery.

[0019] (1) According to one aspect of the present invention, there is provided a lithium silicon oxide that has peaks at 2θ of 23.8 ± 0.5°, 24.3 ± 0.5°, and 24.7 ± 0.5° in the XRD pattern measured using non - monochromatized CuKα rays, and satisfies the following Mathematical Formula 1:

[0020] [Mathematical Formula 1]

[0021] y sio2,最大 ≤0.4·y si,111

[0022] In the above mathematical formula 1,

[0023] y sio2,最大 represents the height of the highest peak among the SiO2 peaks located at 2θ = 20.7 ± 0.5°, 21.6 ± 0.5°, and 26.5 ± 0.5° in the XRD pattern measured using non-monochromatized CuKα rays, and y si,111 represents the height of the Si peak located at 2θ = 28.5 ± 0.5° in the XRD pattern.

[0024] (2) The present invention provides a lithium silicon oxide according to the above (1), wherein the lithium silicon oxide satisfies the following mathematical formula 2:

[0025] [Mathematical formula 2]

[0026] I q,100 +I c,111 +I q,011 ≤0.3·I si,111

[0027] In the above mathematical formula 2,

[0028] I q,100 、I c,111 and I q,011 represent the integrated intensities of the SiO2 peaks located at 2θ = 20.7 ± 0.5°, 21.6 ± 0.5°, and 26.5 ± 0.5° respectively in the XRD pattern measured using non-monochromatized CuKα rays, and I si,111 represents the integrated intensity of the Si peak located at 2θ = 28.5 ± 0.5° in the XRD pattern.

[0029] (3) The present invention provides a lithium silicon oxide according to the above (1) or (2), wherein the lithium silicon oxide satisfies the following mathematical formula 3:

[0030] [Mathematical formula 3]

[0031] 0≤y o3,111 ≤0.1·y 背景

[0032] In the above mathematical formula 3,

[0033] y o3,111 represents the height of the Li2SiO3 peak located at 2θ = 27.0 ± 0.2° in the XRD pattern measured using non-monochromatized CuKα rays, and y 背景 represents the height of the background peak excluding the Li2SiO3 peak located at 2θ = 27.0 ± 0.2° in the XRD pattern.

[0034] (4) The present invention provides a lithium silicon oxide according to any one of (1) to (3) above, wherein the lithium silicon oxide has no peak at 27.0 ± 0.2° in the XRD pattern measured using non-monochromatized CuKα rays.

[0035] (5) The present invention provides a lithium silicon oxide according to any one of (1) to (4) above, wherein the lithium silicon oxide contains Si, SiOx (0 < x ≤ 2), and a lithium-containing compound.

[0036] (6) The present invention provides the lithium silicon oxide according to (5) above, wherein Si and SiOx (0 < x ≤ 2) include a carbon coating on the surface.

[0037] (7) The present invention provides the lithium silicon oxide according to (5) above, wherein the lithium-containing compound includes at least any one of lithium metasilicate or lithium silicide.

[0038] (8) According to another aspect of the present invention, there is provided a negative electrode, which includes a conductive metal current collector and a negative electrode material layer provided on at least one surface of the current collector, wherein the above negative electrode material layer contains the lithium silicon oxide according to any one of (1) to (7) above.

[0039] (9) According to another aspect of the present invention, there is provided a lithium secondary battery, which includes: the negative electrode according to (8) above; a positive electrode; a separator provided between the positive electrode and the negative electrode; and an electrolyte.

[0040] Advantageous Effects

[0041] Due to the lithium silicon oxide negative electrode material according to the present invention, even when it is prepared as an aqueous negative electrode material slurry, the decrease in the slurry viscosity caused by LiOH by-products is suppressed and the hydrogen generation is also suppressed, and thus it exhibits excellent initial capacity and capacity retention rate. And compared with the aqueous negative electrode material slurry containing typical silicon particles or silicon oxide particles, its viscosity change is small and the hydrogen generation is reduced, and therefore the slurry coating defects and the decrease in adhesion strength caused by the decreased slurry viscosity can be prevented, and excellent storage stability can be exhibited.

[0042] In addition, the negative electrode according to the present invention includes a negative electrode material layer containing lithium silicon oxide as the negative electrode material, and thus can exhibit excellent initial efficiency and suppressed volume expansion, thereby achieving excellent capacity retention rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The following attached drawings herein show preferred examples of the present invention as examples and are used together with the detailed description of the present invention given below to enable further understanding of the technical concept of the present invention, and therefore the present invention should not be construed only by the content in such drawings.

[0044] Figure 1 XRD patterns of the lithium silicon oxides prepared in the examples and comparative examples measured using non-monochromatized CuKα radiation. Detailed Description of the Invention

[0045] Hereinafter, the present invention will be described in detail to facilitate understanding of the present invention.

[0046] It will be understood that the words or terms used in the specification and claims of the present invention should not be construed as being limited to the meanings defined in a commonly used dictionary. It will also be understood that based on the principle that the inventor can appropriately define the meanings of the words or terms to best illustrate the invention, the words or terms should be construed as having meanings consistent with their meanings in the context of the related art and the technical concept of the present invention.

[0047] Measurement method

[0048] Here, the XRD patterns were measured using a D8 Endeavor powder X-ray diffractometer (Bruker), using CuKα radiation without using a separate monochromator. The measurement was carried out under the following conditions: voltage: 40 kV, current: 40 mA, 2θ (Bragg angle) = 20° to 80°, step size = 0.02°, and time / step = 0.30 seconds.

[0049] Here, the peak height in the XRD pattern was measured using the "net height" observed in the creation area of the Bruker DIFFRAC.EVA program. Specifically, the creation area was used as the standard for each peak to set a range of at least twice the full width at half maximum (FWHM), and then the two ends of the range were dragged until the net height reached the maximum, and the net height in this case was used as the peak height.

[0050] Here, the integrated intensity of the peaks in the XRD pattern was evaluated using single-peak fitting of the Bruker DIFFRAC.TOPAS program. The LP factor correction was not checked, and a first-order Chebyshev polynomial was used for the background. The peak type was PV (pseudo-Voigt), and fitting was performed in two separate parts: 2θ = 20.0° to 23.0° and 2θ = 25.8° to 32.0°. In this case, the PV peak was assigned to all the peaks identified in the part, and then fitting was performed. The resulting "area" was taken as the integrated intensity.

[0051] Lithium silicon oxide

[0052] The present invention provides a lithium silicon oxide usable as a negative electrode material, which has excellent initial capacity and capacity retention rate, has a minimum change in viscosity during the preparation of a slurry by a wet process, and suppresses hydrogen generation.

[0053] The lithium silicon oxide according to one embodiment of the present invention has peaks at 2θ = 23.8 ± 0.5°, 24.3 ± 0.5°, and 24.7 ± 0.5° in an XRD pattern measured using non-monochromatized CuKα rays, and satisfies the following Mathematical Formula 1:

[0054] [Mathematical Formula 1]

[0055] y sio2,最大 ≤0.4·y si,111

[0056] In the above Mathematical Formula 1,

[0057] y sio2,最大 represents the height of the highest peak among the SiO2 peaks at 2θ = 20.7 ± 0.5°, 21.6 ± 0.5°, and 26.5 ± 0.5° in the XRD pattern measured using non-monochromatized CuKα rays, and y si,111 represents the height of the Si peak at 2θ = 28.5 ± 0.5° in the XRD pattern.

[0058] Graphite-based negative electrode materials known as negative electrode materials maintain excellent structural stability even during the insertion and extraction of lithium, and thus exhibit a stable capacity retention rate during long-term cycling. However, this material is limited by a low theoretical capacity of 350 mAh / g for LiC6 and is considered insufficient to meet the current demand for high-energy and high-power materials. On the contrary, silicon or silicon oxide with a theoretical capacity about 10 times that of graphite (for Li 4.4Si (about 4200 mAh / g) is attracting attention. However, compared with graphite-based anodes, silicon-based anodes consume about three times as much lithium and cause a large initial irreversible capacity. Therefore, methods such as Li pre-lithiation have been explored to improve the initial efficiency, which is hindered by irreversible reactions of lithium ions. The pre-lithiated silicon-based anode materials provide excellent charge / discharge efficiency and are thus desirable in terms of cycling characteristics, but cause capacity degradation and gas generation during the process. In particular, there are lithium silicate crystals and crystalline silicon dioxide (SiO2) in the pre-lithiated silicon-based anode materials. Since lithium silicate crystals are easily soluble in water, when preparing an aqueous anode material slurry using the pre-lithiated silicon-based anode materials, the lithium silicate crystals dissolve in water and the internal silicon contacts water, oxidizing the silicon and reducing the water, thereby generating hydrogen gas, which changes the slurry viscosity and deteriorates the slurry coating characteristics, and this causes serious defects in slurry coating, leading to serious problems such as rapid capacity degradation due to electrical short circuit with the current collector. In addition, crystalline silicon dioxide (SiO2) forms irreversible lithium silicate crystals during the charging process, consuming lithium and reducing the initial capacity of the battery.

[0059] However, the lithium silicon oxide according to the present invention has peaks within a specific position range in the XRD pattern and satisfies Mathematical Formula 1, and thus can be made into an aqueous anode slurry without dissolving in water, thereby preventing slurry coating defects and reduced adhesion strength caused by hydrogen gas generation, and thus the anode can have excellent integrity, capacity retention rate, and initial capacity.

[0060] Hereinafter, the lithium silicon oxide according to the present invention will be described in detail.

[0061] The lithium silicon oxide according to an embodiment of the present invention can be used as an anode material, particularly as an anode material for an aqueous slurry, and has peaks at 2θ = 23.8 ± 0.5°, 24.3 ± 0.5°, and 24.7 ± 0.5° in the XRD pattern measured using non-monochromatized CuKα radiation and satisfies the following Mathematical Formula 1.

[0062] [Mathematical Formula 1]

[0063] y sio2,最大 ≤ 0.4·y si,111

[0064] In the above Mathematical Formula 1,

[0065] y sio2,最大 represents the height of the highest peak among the SiO2 peaks at 2θ = 20.7 ± 0.5°, 21.6 ± 0.5°, and 26.5 ± 0.5° in the XRD pattern measured using non-monochromatized CuKα radiation, and y si,111It represents the height of the Si peak located at 2θ=28.5±0.5° in the XRD spectrum.

[0066] In addition, lithium silicon oxide may satisfy the following Mathematical Formula 1-1.

[0067] [Mathematical formula 1-1]

[0068] 0.005·y Si,111 ≤y sio2,最大 ≤0.4·y Si,111

[0069] In the above mathematical formula 1-1,

[0070] y sio2,最大 represents the height of the highest peak among the SiO2 peaks located at 2θ=20.7±0.5°, 21.6±0.5° and 26.5±0.5° in the XRD pattern measured using non-monochromatized CuKα radiation, and y si,111 It represents the height of the Si peak located at 2θ=28.5±0.5° in the XRD spectrum.

[0071] When crystalline SiO2 (quartz, cristobalite) (which is a phase unsuitable for lithium insertion / deinsertion and satisfies mathematical formula 1-1 of lithium silicon oxide) is confined within an appropriate range, the capacity and efficiency of lithium secondary batteries containing crystalline SiO2 may not be adversely affected, and crystalline SiO2 may also be superior in suppressing gas generation by obtaining structural stability.

[0072] In addition, the lithium silicon oxide according to one embodiment of the present invention satisfies the following Mathematical Formula 2.

[0073] [Mathematical formula 2]

[0074] I q,100 +I c,111 +I q,011 ≤0.3·I si,111

[0075] In the above mathematical formula 2,

[0076] I q,100 ,I c,111 and I q,011 represents the integrated intensity of the SiO2 peaks located at 2θ = 20.7 ± 0.5°, 21.6 ± 0.5° and 26.5 ± 0.5° in the XRD spectrum measured using non-monochromatized CuKα radiation, and I si,111 It represents the integrated intensity of the Si peak located at 2θ=28.5±0.5° in the XRD spectrum.

[0077] In addition, lithium silicon oxide may satisfy the following Mathematical Formula 2-1.

[0078] [Mathematical formula 2-1]

[0079] 0.002·I si,111 ≤I q,100 +I c,111 +I q,011 ≤0.3·I si,111

[0080] In the above Mathematical formula 2-1,

[0081] I q,100 、I c,111 and I q,011 represent the integrated intensities of the SiO2 peaks located at 2θ = 20.7 ± 0.5°, 21.6 ± 0.5° and 26.5 ± 0.5° respectively in the XRD pattern measured using non-monochromatized CuKα rays, and I si,111 represents the integrated intensity of the Si peak located at 2θ = 28.5 ± 0.5° in the XRD pattern.

[0082] When the lithium silicon oxide satisfies the above Mathematical formula 2-1, crystalline SiO2 (quartz, cristobalite), which is a phase not suitable for lithium insertion / extraction, is restricted within an appropriate range, and the capacity and efficiency of a lithium secondary battery containing crystalline SiO2 can be not adversely affected, and crystalline SiO2 can also be more excellent in suppressing gas generation by obtaining structural stability.

[0083] In addition, the lithium silicon oxide can satisfy the following Mathematical formula 3.

[0084] [Mathematical formula 3]

[0085] 0≤y o3,111 ≤0.1·y 背景

[0086] In the above Mathematical formula 3,

[0087] y o3,111 represents the height of the Li2SiO3 peak located at 2θ = 27.0 ± 0.2° in the XRD pattern measured using non-monochromatized CuKα rays, and y 背景 represents the height of the background peak excluding the Li2SiO3 peak located at 2θ = 27.0 ± 0.2° in the XRD pattern.

[0088] As another example, the lithium silicon oxide may have no peak at 27.0 ± 0.2° in the XRD pattern measured using non-monochromatized CuKα rays.

[0089] As another example, the lithium silicon oxide satisfies Mathematical Formula 2 while satisfying Mathematical Formula 1, and there are or are not peaks within a specific position range in the XRD pattern.

[0090] As another example, the lithium silicon oxide satisfies Mathematical Formula 2 and Mathematical Formula 3 while satisfying Mathematical Formula 1, and there are or are not peaks within a specific position range in the XRD pattern.

[0091] In the present invention, the lithium silicon oxide is produced by prelithiation of a silicon-based compound such as silicon and / or silicon oxide with Li.

[0092] Meanwhile, when prelithiating the silicon-based compound, crystalline lithium silicate (Li2SiO3) and lithium pyrosilicate (Li2Si2O5) are usually produced by prelithiation, and since lithium silicate is easily soluble in water, when used to prepare an aqueous slurry, process and efficiency degradation may be caused due to hydrogen generation.

[0093] However, the lithium silicon oxide according to the present invention can be prepared using a specific concentration of LiBP (lithium biphenyl) through the prelithiation process to be described below, and thus may not contain crystalline lithium silicate and only contain crystalline lithium pyrosilicate that is insoluble in water. Therefore, the lithium silicon oxide has peaks at 2θ = 23.8 ± 0.5°, 24.3 ± 0.5°, and 24.7 ± 0.5° in the XRD pattern and no peak at 27.0 ± 0.2°. In addition, Mathematical Formula 1 and / or Mathematical Formula 2 can be satisfied simultaneously.

[0094] The lithium silicon oxide according to the present invention satisfies the above characteristics, thereby preventing hydrogen generation during the preparation of the slurry by the water method, and thus does not exhibit coating defects or reduced adhesion strength, but exhibits excellent initial capacity and capacity retention rate.

[0095] In addition, the lithium silicon oxide may include Si (silicon particles), SiOx (0 < x ≤ 2) (silicon oxide particles), and a lithium-containing compound.

[0096] Si and SiOx may each have an amorphous structure, and the average particle size (D 50 ) of Si may be 1 μm to 20 μm, and the average particle size (D 50 ) of SiOx may be 5 nm to 1 μm.

[0097] In addition, Si or SiOx may include a carbon coating on the surface, and in this case, the thickness of the carbon coating may be 1 nm to 1 μm, or 100 nm to 1 μm.

[0098] The carbon coating contains a carbon-based material, and the carbon-based material may include at least one of amorphous carbon or crystalline carbon.

[0099] Crystalline carbon can further enhance the conductivity of the anode material and can be at least any one selected from fluorene, carbon nanotubes, and graphene, for example.

[0100] In addition, amorphous carbon helps to maintain sufficient strength of the carbon coating and can be at least any carbide selected from, for example, tar, pitch, and other organic substances, or a carbon-based material formed using hydrocarbons as a source in chemical vapor deposition, and the carbide of other organic substances can be the carbide of sucrose, glucose, galactose, fructose, lactose, mannose, ribose, aldohexose or ketohexose, and combinations thereof.

[0101] In addition, the hydrocarbon can be a substituted or unsubstituted aliphatic hydrocarbon or alicyclic hydrocarbon, a substituted or unsubstituted aromatic hydrocarbon, and can be, for example, methane, ethane, ethylene, acetylene, propane, butane, butene, pentane, isobutane, hexane, benzene, toluene, xylene, styrene, ethylbenzene, diphenylmethane, naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, coumarone, pyridine, anthracene, or phenanthrene.

[0102] The lithium-containing compound can be a compound formed by doping Si and / or SiOx with lithium metal through prelithiation of Si and / or SiOx, and specifically can include at least any one of lithium pyrosilicate or lithium silicide.

[0103] Lithium silicide can include Li y Si(2 < y < 5), and can be, for example, at least any one selected from Li 4.4 Si, Li 3.75 Si, Li 3.25 Si, and Li 2.33 Si.

[0104] Method for preparing lithium silicon oxide

[0105] The present invention provides a method for preparing lithium silicon oxide.

[0106] The method for preparing lithium silicon oxide according to one embodiment of the present invention can include step (S1) of adding Si or SiOx (0 < x ≤ 2) particles to a solution containing a lithium compound in an inert atmosphere and stirring the mixture; and step (S2) of separating the resulting particles, then drying and firing the obtained product, and the concentration of the solution containing the lithium compound can be greater than 0.5M and less than 1.0M.

[0107] In a method for preparing a lithium silicon oxide according to an embodiment of the present invention, a silicon-based negative electrode material is added to a solution containing a lithium compound with a concentration greater than 0.5 M and less than 1.0 M (wherein the lithium compound is dissolved in an organic solvent at a specific concentration), stirred, and heat-treated, so that Li is inserted and diffused into the silicon-based negative electrode material, thereby causing an appropriate redox reaction process, and thereby preparing a lithium silicon oxide having the above characteristics.

[0108] Hereinafter, a method for preparing a lithium silicon oxide composite according to an embodiment of the present invention will be described in more detail, divided into the following steps.

[0109] Step (S1)

[0110] The above step (S1) is a step of pre-lithiating Si or SiOx (0 < x ≤ 2) to produce lithium silicon oxide particles, and involves adding Si or SiOx (0 < x ≤ 2) particles to a solution containing a lithium compound in an inert gas atmosphere and stirring the mixture, and the concentration of the solution containing the lithium compound can be greater than 0.5 M and less than 1.0 M.

[0111] Here, the solution containing a lithium compound with a concentration greater than 0.5 M and less than 1.0 M means that the lithium compound is dissolved therein at a concentration greater than 0.5 moles and less than 1.0 moles per liter of the solution.

[0112] In an embodiment of the present invention, each of Si and SiOx (0 < x ≤ 2) may have an amorphous structure, and the average particle size (D 50 ) of silicon (Si) may be from 1 μm to 20 μm, and the average particle size (D 50 ) of silicon oxide (SiOx (0 < x ≤ 2)) may be from 5 nm to 1 μm.

[0113] In addition, the silicon or silicon oxide may include a carbon coating on the surface, and in this case, the thickness of the carbon coating may be from 1 nm to 1 μm, or from 100 nm to 1 μm.

[0114] The carbon coating contains a carbon-based material, and the carbon-based material may include at least one of amorphous carbon and crystalline carbon.

[0115] Crystalline carbon can further enhance the conductivity of the negative electrode material, and may be, for example, at least any one selected from fluorene, carbon nanotubes, and graphene.

[0116] In addition, amorphous carbon helps to maintain sufficient strength of the carbon coating, and can be at least any one carbide selected from tar, pitch, and other organic substances, or a carbon-based material formed by using hydrocarbons as a source in chemical vapor deposition, and the carbide of other organic substances can be the carbide of sucrose, glucose, galactose, fructose, lactose, mannose, ribose, aldohexose or ketohexose, and combinations thereof.

[0117] In addition, the hydrocarbon can be a substituted or unsubstituted aliphatic hydrocarbon or alicyclic hydrocarbon, a substituted or unsubstituted aromatic hydrocarbon, and can be, for example, methane, ethane, ethylene, acetylene, propane, butane, butene, pentane, isobutane, hexane, benzene, toluene, xylene, styrene, ethylbenzene, diphenylmethane, naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, coumarone, pyridine, anthracene or phenanthrene.

[0118] In one embodiment of the present invention, relative to 100 parts by weight of the solution containing a lithium compound, silicon or silicon oxide can be added in an amount greater than 0.131 parts by weight and less than 0.142 parts by weight.

[0119] Here, the solution containing a lithium compound can be prepared by adding a polycyclic aromatic compound or a linear polyphenylene compound to an organic solvent and stirring the mixture to prepare a polycyclic aromatic compound solution or a linear polyphenylene compound solution, and then adding lithium particles to the polycyclic aromatic compound solution or the linear polyphenylene compound solution and reacting the mixture.

[0120] In addition, the lithium particles react with the polycyclic aromatic compound or the linear polyphenylene compound in a molar ratio of 1:1 in the polycyclic aromatic compound solution or the linear polyphenylene compound solution.

[0121] In addition, the polycyclic aromatic compound can be at least one selected from naphthalene, anthracene, phenanthrene, tetracene, pentacene, pyrene, picene, triphenylene, coronene, fluorene and 9,9-dimethylfluorene, and the linear polyphenylene compound can be at least one selected from biphenyl, terphenyl and 4,4-dimethylbiphenyl. Specifically, the polycyclic aromatic compound can be any one selected from naphthalene, fluorene and 9,9-dimethylfluorene, and the linear polyphenylene compound can be biphenyl or 4,4-dimethylbiphenyl.

[0122] In addition, the organic solvent can be an ether-based solvent, a ketone-based solvent, an ester-based solvent, an alcohol-based solvent, an amine-based solvent, or a mixed solvent thereof. For example, the ether solvent can be diethyl ether, tert-butyl methyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, di alkane, 1,2-dimethoxyethylene, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, or a mixed solvent thereof. In particular, tetrahydrofuran, 2-methyltetrahydrofuran, di Alkanes and 1,2-dimethoxyethane may be desirable.

[0123] In addition, as the ketone-based solvent, acetone, acetophenone, etc. can be used, and as the ester-based solvent, methyl formate, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, or a mixed solvent thereof can be used.

[0124] In addition, as the alcohol-based solvent, methanol, ethanol, propanol, isopropyl alcohol, or a mixed solvent thereof can be used, and as the amine-based solvent, methylamine, ethylamine, ethylenediamine, or a mixed solvent thereof can be used.

[0125] In addition, the reaction for obtaining the solution containing the lithium compound can be carried out for 0.5 hour to 6.0 hours in the temperature range of 20 °C to 90 °C while stirring, and the lithium compound can be formed more effectively by stirring for the specified time at the above-specified temperature.

[0126] In the above step (S1), considering the control of the lithium ion diffusion rate and appropriate prelithiation, the first stirring is carried out by stirring for 1 hour or longer in the temperature range of 30 °C to 90 °C, then the second stirring is carried out while cooling to room temperature, and the first stirring and the second stirring can be carried out for the same amount of time.

[0127] Step (S2)

[0128] The above step (S2) is a step of preparing lithium silicon oxide by separating, drying, and firing the lithium silicon oxide particles generated in step (S1), and it can be carried out by separating the particles generated in step (S1), and then drying and firing the obtained product.

[0129] The generated particles can be obtained by a typical method in the art by separating solid particles from the solution. For example, the solution can be centrifuged to separate the supernatant and the generated particles as the precipitate.

[0130] Drying can be carried out by a typical method in the art, and it can be carried out by allowing the solution to stand for at least 2 hours in the temperature range of 70 °C to 90 °C, or 75 °C to 85 °C.

[0131] In addition, firing can be carried out by heat-treating for 1 hour to 2 hours in the temperature range of 850 °C to 900 °C in an inert gas atmosphere.

[0132] Meanwhile, in the method for preparing lithium silicon oxide according to an embodiment of the present invention, the inert gas can be argon, nitrogen, or a combination thereof.

[0133] Negative electrode

[0134] The present invention provides a negative electrode comprising the lithium silicon oxide.

[0135] According to an embodiment of the present invention, the negative electrode includes a conductive metal current collector and a negative electrode material layer disposed on at least one surface of the current collector, and the negative electrode material layer contains the lithium silicon oxide.

[0136] The negative electrode according to the present invention includes a negative electrode material layer containing a lithium silicon oxide, and can thus exhibit excellent initial efficiency and suppressed volume expansion, resulting in excellent capacity retention and long-term stability.

[0137] The conductive metal current collector includes a conductive metal having high electrical conductivity, and the conductive metal current collector is not particularly limited as long as it is non-reactive within the voltage range of the battery. For example, stainless steel; aluminum; nickel; titanium; fired carbon; or aluminum or stainless steel surface-treated with one of carbon, nickel, titanium, and silver; etc. can be used. In addition, the thickness of the current collector can be 3 μm to 500 μm.

[0138] Meanwhile, the negative electrode can be prepared by mixing an aqueous solvent, a lithium silicon oxide, a binder, and a conductive material to prepare a negative electrode material slurry, and applying the negative electrode material slurry onto at least one surface of the conductive metal current collector and drying. Here, the aqueous solvent can be water.

[0139] In addition, as the conductive material, any conductive material can be used without particular limitation as long as it has electronic conductivity and does not cause chemical changes. Specifically, the conductive material can be graphite, such as natural graphite or artificial graphite; carbon-based materials, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powders or metal fibers, such as copper, nickel, aluminum, and silver; conductive tubes, such as carbon nanotubes; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides, such as titanium oxide; or conductive polymers, such as polyphenylene derivatives, and any one of them or a mixture of two or more of them can be used.

[0140] In addition, relative to the total weight of the negative electrode material layer, the binder can typically be added in an amount of 0.1 wt% to 10 wt%, and examples of the binder can be polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile rubber, fluororubber, and various copolymers thereof.

[0141] Lithium secondary battery

[0142] The present invention provides a lithium secondary battery including the above-described negative electrode.

[0143] According to one embodiment of the present invention, a lithium secondary battery may include a negative electrode, a positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. In addition, the lithium secondary battery may optionally include a battery case for accommodating an electrode assembly composed of the negative electrode, the positive electrode, and the separator, and a sealing member for sealing the battery case.

[0144] According to one embodiment of the present invention, the positive electrode may include a positive electrode current collector and a positive electrode active material layer positioned on the positive electrode current collector.

[0145] According to one embodiment of the present invention, the positive electrode current collector is not particularly limited as long as it has high conductivity and does not cause chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with one of carbon, nickel, titanium, silver, etc., aluminum cadmium alloy, and the like can be used. In addition, the thickness of the positive electrode current collector may typically be from 3 μm to 500 μm, and fine irregularities may be formed on the surface to improve the adhesion of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam body, and a non-woven fabric.

[0146] According to one embodiment of the present invention, in addition to the positive electrode active material, the positive electrode active material layer may optionally contain a binder and a conductive material.

[0147] According to one embodiment of the present invention, the positive electrode active material may be one selected from the following: LiCoO2, LiCoPO4, LiNiO2, Li x Ni a Co b M 1 c M 2 d O2 (M 1 and M 2 are each independently one selected from Al, Mn, Cu, Fe, V, Cr, Mo, Ga, B, W, Mo, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, F, P, S, and Y, and satisfying 0.9 ≤ x ≤ 1.1, 0 < a < 1.0, 0 < b < 1.0, 0 ≤ c < 0.5, 0 ≤ d < 0.5, and a + b + c + d = 1), LiMnO2, LiMnO3, LiMn2O3, LiMn2O4, LiMn 2-e M 3 e O2 (M 3 is at least one selected from Co, Ni, Fe, Cr, Zn, and Ta, and satisfying 0.01 ≤ e ≤ 0.1), Li2Mn3M4 O8(M 4 at least one selected from Ci, Ni, Fe, Cu, and Zn), LiFePO4, Li2CuO2, LiV3O8, V2O5, Cu2V2O7, and lithium metal.

[0148] According to one embodiment of the present invention, the binder is a component that helps the binding between the conductive material, the positive electrode material, and the current collector, and can generally be added in an amount of 0.1% by weight to 10% by weight relative to the total weight of the positive electrode material layer. Examples of the binder may include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile rubber, fluororubber, various copolymers thereof, and the like.

[0149] According to one embodiment of the present invention, the conductive material of the positive electrode material layer is a component for further improving the conductivity of the positive electrode material, and can be added in an amount of 10% by weight or less, preferably 5% by weight or less, relative to the total weight of the positive electrode material layer. Such a conductive material is not particularly limited as long as it has conductivity and does not cause chemical changes in the battery. For example, the following conductive materials can be used: graphite, such as natural graphite and artificial graphite; carbon black, such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal cracking carbon black; conductive fibers, such as carbon fibers and metal fibers; metal powders, such as carbon fluoride powder, aluminum powder, and nickel powder; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides, such as titanium oxide; or polyphenylene derivatives; and so on.

[0150] According to one embodiment of the present invention, the positive electrode can be manufactured by applying a slurry for forming the positive electrode material layer (which is prepared by dissolving or dispersing the positive electrode material and optionally the binder and the conductive material in a solvent) on the positive electrode current collector and then drying, or by casting a separate support with the slurry for forming the positive electrode material layer and then laminating the film separated from the support on the positive electrode current collector.

[0151] According to an embodiment of the present invention, the separator is used to separate the negative electrode and the positive electrode and provide a moving path for lithium ions, and any separator can be used without particular limitation as long as it is typically used as a separator in a lithium secondary battery. In particular, a separator having a high moisture retention capacity for the electrolyte and a low resistance to the movement of electrolyte ions is preferred. Specifically, a porous polymer membrane can be used, such as a porous polymer membrane prepared from a polyolefin-based polymer (e.g., ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer); or a laminated structure having two or more layers thereof. In addition, typical porous nonwoven fabrics can be used, such as nonwoven fabrics formed from high melting point glass fibers or polyethylene terephthalate fibers. In addition, a coated separator containing a ceramic component or a polymer component can be used to ensure heat resistance or mechanical strength, and a separator having a single-layer or multi-layer structure can be used.

[0152] According to an embodiment of the present invention, as the electrolyte, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, an inorganic solid electrolyte, a melt-type inorganic electrolyte, etc. that can be used to manufacture a lithium secondary battery can be used without particular limitation. As a specific example, the electrolyte can contain an organic solvent and a lithium salt.

[0153] According to an embodiment of the present invention, as the organic solvent, any organic solvent can be used without particular limitation as long as it can be used as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, as the organic solvent, an ester-based solvent such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; an ether-based solvent such as dibutyl ether or tetrahydrofuran; a ketone-based solvent such as cyclohexanone; an aromatic hydrocarbon-based solvent such as benzene and fluorobenzene; a carbonate-based solvent such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); an alcohol-based solvent such as ethanol and isopropanol; a nitrile such as R-CN (where R is a linear, branched, or cyclic C2 to C20 hydrocarbon group and may include a double bond aromatic ring or an ether bond); an amide such as dimethylformamide; a dioxolane such as 1,3-dioxolane; or sulfolane can be used. Among these solvents, carbonate-based solvents are preferred, and a mixture of a cyclic carbonate having a high ionic conductivity and a high dielectric constant (e.g., ethylene carbonate or propylene carbonate) and a linear carbonate-based compound having a low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) (a mixture that can improve the charge / discharge performance of the battery) is more preferred.

[0154] According to an embodiment of the present invention, any compound can be used as the lithium salt without particular limitation as long as it can provide lithium ions for the lithium secondary battery. Specifically, the anion of the lithium salt can be at least one selected from the following: F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - , and as the lithium salt, LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI or LiB(C2O4)2 can be used. The lithium salt can preferably be used in a concentration range of 0.1 M to 2.0 M. When the concentration of the lithium salt is included in the above range, the electrolyte has appropriate conductivity and viscosity, and thus can exhibit excellent performance, and lithium ions can move effectively.

[0155] According to one embodiment of the present invention, for the purposes of enhancing the life characteristics of the battery, suppressing the reduction of the battery capacity, enhancing the discharge capacity of the battery, etc., in addition to the above electrolyte components, the electrolyte may further contain, for example, at least one additive selected from vinylene carbonate (VC), ethylene vinylene carbonate (VEC), fluoroethylene carbonate (FEC), propanesultone (PS), 1,3 - propanesultone (PRS), ethylene sulfite (Esa), succinonitrile (SN), adiponitrile (AN), hexanetricarbonitrile (HTCN), γ - butyrolactone, biphenyl (BP), cyclohexylbenzene (CHB), and tert - amylbenzene (TAB); or at least one additive such as a compound based on a haloalkyl carbonate (e.g., difluoroethylene carbonate), pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n - glycol dimethyl ether, hexaphosphoryl triamide, nitrobenzene derivative, sulfur, quinone imine dye, N - substituted oxazolidone, N,N - substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2 - methoxyethanol, or aluminum trichloride. In this case, the additive may be included in an amount of 0.1 wt% to 5 wt% relative to the total weight of the electrolyte.

[0156] The lithium secondary battery including the negative electrode according to the present invention stably exhibits excellent capacity characteristics, output characteristics, and life characteristics, and can thus be used in portable devices such as mobile phones, laptop computers, and digital cameras, and can also be used in the field of electric vehicles such as hybrid electric vehicles (HEV) and electric vehicles (EV).

[0157] The external shape of the lithium secondary battery of the present invention is not particularly limited, and thus a cylindrical shape, a prismatic shape, a pouch shape, or a coin shape using a can may be used.

[0158] The lithium secondary battery according to the present invention can be used as a battery cell for powering small devices, and can also preferably be used as a unit cell of medium - sized and large - sized battery modules including a plurality of battery cells.

[0159] Therefore, according to one embodiment of the present invention, there are provided a battery module including a lithium secondary battery as a unit cell and a battery pack including the same.

[0160] According to one embodiment of the present invention, the battery module or the battery pack can be used as a power source for one or more medium - sized and large - sized devices such as: power tools; electric vehicles, such as electric vehicles (EV), hybrid electric vehicles (HEV), and plug - in hybrid electric vehicles (PHEV); or power storage systems.

[0161] Example

[0162] In the following, embodiments of the present invention will be described in detail in a manner that enables those skilled in the art to easily implement the present invention. However, the present invention can be embodied in many different forms and is not limited to the embodiments described herein.

[0163] Example 1

[0164] 2.78 g of biphenyl was added to 30 ml of 2-methyltetrahydrofuran and stirred for 10 minutes. When the solution became transparent, 0.125 g of Li powder was added thereto and stirred for 6 hours to prepare a dark green 0.6 M LiBP solution.

[0165] 4 g of SiOx / C (0 < x ≤ 2) powder having a carbon coating on the surface and an average particle size (D 50 ) of 5 μm was added to the LiBP solution and stirred at 80 °C for 1 hour. The evaporated solvent was collected through a reflux condenser to maintain a constant concentration. Thereafter, the resulting product was cooled to room temperature (25 °C) and stirred for an additional hour. In this case, all processes were carried out in an argon atmosphere.

[0166] Thereafter, the solution was centrifuged to separate only the powder particles therefrom. The separated particles were dried at 80 °C for 6 hours, heated to 900 °C, and heat-treated in an argon atmosphere for 2 hours to prepare lithium silicon oxide.

[0167] Example 2

[0168] Referring to Example 1, lithium silicon oxide was prepared in the same manner as in Example 1, except that 3.7 g of biphenyl and 0.166 g of Li powder were used to prepare a 0.8 M LiBP solution.

[0169] Comparative Example 1

[0170] Referring to Example 1, lithium silicon oxide was prepared in the same manner as in Example 1, except that 2.31 g of biphenyl and 0.104 g of Li powder were used to prepare a 0.5 M LiBP solution.

[0171] Comparative Example 2

[0172] Referring to Example 1, lithium silicon oxide was prepared in the same manner as in Example 1, except that 4.62 g of biphenyl and 0.21 g of Li powder were used to prepare a 1.0 M LiBP solution.

[0173] Experimental Example 1

[0174] XRD analysis was performed on each lithium silicon oxide prepared in the examples and comparative examples for comparative analysis of characteristics, and the results are shown in Figure 1 and Table 1.

[0175] The XRD pattern was measured using a D8 Endeavor powder X-ray diffractometer (Bruker), using CuKα radiation and without using a separate monochromator. The measurement was carried out under the following conditions: voltage: 40 kV, current: 40 mA, 2θ (Bragg angle) = 20° to 80°, step size = 0.02° and time / step = 0.30 s, and the presence or absence of peaks was observed at 2θ = 23.8 ± 0.5° (peak 1), 24.3 ± 0.5° (peak 2) and 24.7 ± 0.5° (peak 3) in the measured XRD pattern.

[0176] In addition, the height (y sio2,最大 ) of the highest peak among the SiO2 peaks at 2θ = 20.7 ± 0.5°, 21.6 ± 0.5° and 26.5 ± 0.5° in the XRD pattern and the height (y si,111 ) of the Si peak at 2θ = 28.5 ± 0.5° were evaluated to determine whether the mathematical formula 1 was satisfied. In this case, the "net height" observed in the creation area of the Bruker DIFFRAC.EVA program was used to measure the height of each peak in the XRD pattern. Specifically, the creation area was used as the standard for each peak to set a range of at least twice the full width at half maximum (FWHM), and then the two ends of this range were dragged until the net height reached the maximum value, and the net height in this case was used as the peak height.

[0177] [Mathematical formula 1]

[0178] y sio2,最大 ≤ 0.4y si,111

[0179] In the above mathematical formula 1,

[0180] y sio2,最大 represents the height of the highest peak among the SiO2 peaks at 2θ = 20.7 ± 0.5°, 21.6 ± 0.5° and 26.5 ± 0.5° in the XRD pattern measured using non-monochromatized CuKα radiation, and y si,111 represents the height of the Si peak at 2θ = 28.5 ± 0.5° in the XRD pattern.

[0181] In addition, the integrated intensity of the peaks in the XRD pattern was evaluated to determine whether the mathematical formula 2 was satisfied. In this case, the integrated intensity of the peaks was measured using single-peak fitting of the Bruker DIFFRAC.TOPAS program. The LP factor correction was not checked, and the first-order Chebyshev polynomial was used for the background. The type of the peak was PV (pseudo-Voigt), and the fitting was performed in the following two separate sections: 2θ = 20.0° to 23.0° and 2θ = 25.8° to 32.0°. In this case, the PV peaks were assigned to all the peaks identified in the section, and then the fitting was carried out. The obtained "area" was taken as the integrated intensity.

[0182] [Mathematical formula 2]

[0183] I q,100 +I c,111 +I q,011 ≤0.3·I si,111

[0184] In the above mathematical formula 2,

[0185] I q,100 、I c,111 and I q,011 represent the integrated intensities of the SiO2 peaks located at 2θ = 20.7 ± 0.5°, 21.6 ± 0.5° and 26.5 ± 0.5° respectively in the XRD pattern measured using non-monochromatized CuKα rays, and I si,111 represents the integrated intensity of the Si peak located at 2θ = 28.5 ± 0.5° in the XRD pattern.

[0186] In addition, the height (y o3,111 ) of the Li2SiO3 peak and the background height (y 背景 ) at the position of 2θ = 27.0 ± 0.2° in the XRD pattern were evaluated to determine whether the mathematical formula 3 was satisfied. In this case, the heights of the peaks in the XRD pattern were measured using the Bruker DIFFRAC.EVA program. At the beginning, the noise was removed using a smoothing function (smoothing factor = 0.15), and the "net height" observed in the created region was used to measure the peak height. Specifically, the created region was used as the standard for each peak to set a range of at least twice the full width at half maximum (FWHM), and then the two ends of the range were dragged until the net height reached the maximum value, and the net height in this case was used as the peak height. In addition, the difference between the total intensity observed at this point and the net height was taken as the background peak height (y 背景 ).

[0187] [Mathematical formula 3]

[0188] 0≤y o3,111 ≤0.1·y背景

[0189] In the above Mathematical Formula 3,

[0190] y o3,111 represents the height of the Li2SiO3 peak at 2θ = 27.0 ± 0.2° in the XRD pattern measured using non-monochromatized CuKα rays, and y 背景 represents the height of the background peak excluding the Li2SiO3 peak at 2θ = 27.0 ± 0.2° in the XRD pattern.

[0191] [Table 1]

[0192]

[0193] As can be seen in the above Table 1 and Figure 1 , the lithium silicon oxides of Example 1 and Example 2 have peaks 1, 2, and 3 at 2θ = 23.8 ± 0.5°, 24.3 ± 0.5°, and 24.7 ± 0.5° in the XRD pattern, and simultaneously satisfy Mathematical Formulas 1 to 3. In contrast, the lithium silicon oxides of Comparative Example 1 and Comparative Example 2 cannot satisfy Mathematical Formula 1 and Mathematical Formula 2 or cannot satisfy Mathematical Formula 3.

[0194] Experimental Example 2

[0195] Using the lithium silicon oxides prepared in the examples and comparative examples, an aqueous slurry of the negative electrode material was prepared, and the amount of gas generation was measured. The results are shown in Table 2 below.

[0196] Each lithium silicon oxide, graphite as a conductive material, Super-C65, and carboxymethyl cellulose and styrene-butadiene rubber binder as a binder were mixed in a weight ratio of 77:19.2:1:1.1:1.6 in an aqueous solvent to prepare an aqueous slurry of the negative electrode material. Thereafter, 5 g of the aqueous slurry of the negative electrode material was placed in an aluminum bag, sealed, and stored in an oven at 60°C, and the amount of gas generation was measured using a specific gravity balance.

[0197] [Table 2]

[0198]

[0199] As can be seen in the above Table 2, it was determined that the negative electrode material slurries containing the lithium silicon oxides of Example 1 and Example 2 exhibited a smaller amount of gas generation than Comparative Examples 1 to 2, and in particular, exhibited a significant reduction in gas generation after long-term storage, reaching only 1 / 8 of the level observed in Comparative Example 2 (which did not satisfy Mathematical Formula 3 as shown in the above Table 1).

[0200] Experimental Example 3

[0201] Using the lithium silicon oxides of the Examples and Comparative Examples, half-cells were fabricated and the battery characteristics were measured, and the results are shown in Table 3 below.

[0202] Each lithium silicon oxide was mixed with Super-C65 as a conductive material and li-PAA as a binder at a weight ratio of 70:15:15 to prepare a negative electrode slurry, and then the slurry was applied onto a copper foil and dried, roll-pressed, and punched to prepare a negative electrode.

[0203] Lithium metal was used as a counter electrode, and a porous polyethylene separator was placed between the negative electrode and the lithium metal, and an electrolyte (in which 1M LiPF6, 1.5 wt% VC, and 0.5 wt% PS were dissolved in a solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 30:70) was added to fabricate a coin-type half-cell.

[0204] After the coin-type half-cell was allowed to stand for 24 hours, the coin-type half-cell was charged at a constant current (CC) of 0.1C to 0.005V in the range of 0.005V to 1.5V with respect to Li / Li+, charged at a constant voltage (V) until the charging current reached 0.02C, and then discharged at a constant current (CC) of 0.1C to determine the first-cycle charge capacity, discharge capacity, and initial efficiency.

[0205] [Table 3]

[0206] Item Charge capacity (mAh / g) Discharge capacity (mAh / g) Initial efficiency (%) Example 1 1640 1300 79 Example 2 1461 1112 76 Comparative Example 1 1585 1189 75 Comparative Example 2 1419 1010 71

[0207] As can be seen from Table 3 above, it was found that the initial efficiencies of Example 1 and Example 2 were higher than those of Comparative Example 1 and Comparative Example 2.

[0208] The results in Tables 1 to 3 above show that the lithium silicon oxide according to the present invention has peaks within a specific position range in the XRD pattern, but has no peaks within another specific position range, and satisfies Mathematical Formula 1, and thus can be made into an aqueous negative electrode slurry without being dissolved in water, thereby achieving a significant reduction in gas generation, and thus the negative electrode can have excellent integrity, enhancing the storage stability, initial capacity, and capacity retention rate.

Claims

1. A lithium silicon oxide having peaks at 2θ of 23.8±0.5°, 24.3±0.5°, and 24.7±0.5° in an XRD pattern measured using non-monochromatized CuKα radiation and satisfying the following Mathematical Formula 1: [Mathematical Formula 1] and sio2,最大 ≤0.4·y si,111 wherein in the above Mathematical Formula 1, y sio2,最大 represents the height of the highest peak among the SiO2 peaks located at 2θ=20.7±0.5°, 21.6±0.5° and 26.5±0.5° in the XRD pattern measured using non-monochromatized CuKα radiation, and y si,111 It represents the height of the Si peak located at 2θ=28.5±0.5° in the XRD pattern.

2. The lithium silicon oxide according to Claim 1, satisfying the following Mathematical Formula 2: [Mathematical Formula 2] I q,100 +I c,111 +I q,011 ≤0.3·I si,111 wherein in the above Mathematical Formula 2, I q,100 ,I c,111 and I q,011 represents the integrated intensity of SiO2 peaks located at 2θ=20.7±0.5°, 21.6±0.5° and 26.5±0.5° respectively in the XRD spectrum measured using non-monochromatized CuKα radiation, and I si,111 It represents the integrated intensity of the Si peak located at 2θ=28.5±0.5° in the XRD spectrum.

3. The lithium silicon oxide according to Claim 1, satisfying the following Mathematical Formula 3: [Mathematical Formula 3] 0≤y o3,111 ≤0.1·y 背景 wherein in the above Mathematical Formula 3, y o3,111 represents the height of the Li2SiO3 peak at 2θ=27.0±0.2° in the XRD pattern measured using non-monochromatized CuKα radiation, and y 背景 It represents the height of the background peak located at 2θ=27.0±0.2° in the XRD spectrum, excluding the Li2SiO3 peak.

4. The lithium silicon oxide according to Claim 1 having no peak at 27.0±0.2° in the XRD pattern measured using non-monochromatized CuKα radiation.

5. The lithium silicon oxide according to Claim 1, comprising Si, SiOx (0 < x ≤ 2), and a lithium-containing compound.

6. The lithium silicon oxide according to Claim 5, wherein the Si and the SiOx (0 < x ≤ 2) include a carbon coating on the surface.

7. The lithium silicon oxide according to Claim 5, wherein the lithium-containing compound includes at least any one of lithium pyrosilicate or lithium silicide.

8. A negative electrode, comprising: a conductive metal current collector; and a negative electrode material layer provided on at least one surface of the current collector, wherein the negative electrode material layer contains the lithium silicon oxide according to Claim 1.

9. A lithium secondary battery, comprising the negative electrode according to Claim 8; a positive electrode; a separator provided between the positive electrode and the negative electrode; and an electrolyte.

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