Silicon carbon composite, negative electrode active material, negative electrode composition, negative electrode, and secondary battery

Abstract

The present invention relates to: a silicon carbon composite having a peak A present in a range of 130 ppm to 150 ppm, a peak B present in a range of 110 ppm to 130 ppm, and a peak C present in a range of 15 ppm to 40 ppm during 13C-NMR analysis, and satisfying equation 1 below; a negative electrode active material comprising same; a negative electrode composition; a negative electrode; a lithium secondary battery; a battery module; and a battery pack. [Equation 1] 0.3 ≤ peak C intensity / (peak A intensity + peak B intensity) ≤ 2.1

Description

Silicon carbon composite, negative electrode active material, negative electrode composition, negative electrode and secondary battery

[0001] This application claims the benefit of Korean Patent Application No. 10-2023-0179544 filed with the Korean Intellectual Property Office on December 12, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present application relates to a silicon carbon composite, a negative electrode active material including the same, a negative electrode including the negative electrode active material, and a secondary battery including the negative electrode.

[0003] The recent rapid proliferation of battery-powered electronic devices, including mobile phones, laptops, electric vehicles, power tools, and vacuum cleaners, has led to a rapid increase in demand for compact, lightweight, and relatively high-capacity and / or high-output secondary batteries. In particular, lithium secondary batteries, with their lightweight design and high energy density, are attracting significant attention as power sources for electronic devices. Accordingly, active research and development efforts are underway to improve the performance of lithium secondary batteries.

[0004] In general, a lithium secondary battery includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, an electrolyte, an organic solvent, etc. In addition, an active material layer including a positive electrode active material and a negative electrode active material may be formed on a current collector on the positive electrode and the negative electrode, respectively. In general, a lithium-containing metal oxide such as LiCoO2 or LiMn2O4 is used as a positive electrode active material for the positive electrode, and a carbon-based active material or a silicon-based active material that does not contain lithium is used as an negative electrode active material for the negative electrode.

[0005] Batteries using graphite as a negative active material can exhibit a high discharge voltage of 3.6 V, but their low capacity limits their ability to increase energy density.

[0006] On the other hand, silicon-based active materials are attracting attention as next-generation cathode active materials due to their high capacity and efficiency. Therefore, the development of silicon-based active materials with high capacity or efficiency characteristics is required.

[0007] One embodiment of the present invention provides a silicon carbon composite, an anode active material, an anode composition, an anode, and a lithium secondary battery that have excellent capacity and / or efficiency characteristics and can be used as a high-energy-density anode active material.

[0008] One embodiment of the present invention provides a silicon carbon composite having peak A present in a range of 130 ppm to 150 ppm, peak B present in a range of 110 ppm to 130 ppm, and peak C present in a range of 15 ppm to 40 ppm when analyzed by 13C-NMR, and an intensity ratio of peak C to the sum of the intensities of peak A and peak B (peak C intensity / (peak B intensity + peak A intensity)) of 0.3 to 2.1.

[0009] One embodiment of the present invention provides a negative electrode active material comprising a silicon carbon composite according to the above-described embodiments.

[0010] One embodiment of the present invention provides a negative electrode composition comprising a negative electrode active material according to the above-described embodiment.

[0011] One embodiment of the present invention provides a cathode comprising a cathode composition according to the above-described embodiment.

[0012] One embodiment of the present invention provides a lithium secondary battery including a negative electrode, a positive electrode, and a separator according to the above-described embodiment.

[0013] One embodiment of the present invention provides a battery module including a lithium secondary battery according to the above-described embodiment.

[0014] One embodiment of the present invention provides a battery pack including a lithium secondary battery according to the above-described embodiment.

[0015] One embodiment of the present invention provides a battery pack including a battery module according to the above-described embodiment.

[0016] According to embodiments of the present invention, a lithium secondary battery with improved capacity and / or efficiency can be provided by using a silicon-carbon composite having a specific ratio of peaks within a specific range during 13C-NMR analysis as an anode active material. Furthermore, by satisfying the above range, problems with process suitability and gas generation of aqueous binders, which occur when using silicon-based active materials, can be improved.

[0017] Figure 1 is a graph showing the results of 13C-NMR analysis of a silicon carbon composite manufactured in Example 1.

[0018] Figure 2 is a graph showing the results of 13C-NMR analysis of the silicon carbon composite manufactured in Example 2.

[0019] Figure 3 is a graph showing the results of 13C-NMR analysis of the silicon carbon composite manufactured in Example 3.

[0020] Figure 4 is a graph showing the results of 13C-NMR analysis of the silicon carbon composite manufactured in Example 4.

[0021] Figure 5 is a graph showing the results of 13C-NMR analysis of the silicon carbon composite manufactured in Example 5.

[0022] Figure 6 is a graph showing the results of 13C-NMR analysis of the silicon carbon composite manufactured in Comparative Example 1.

[0023] Figure 7 is a graph showing the results of 13C-NMR analysis of the silicon carbon composite manufactured in Comparative Example 2.

[0024] Figure 8 is a graph showing the results of 13C-NMR analysis of the silicon carbon composite manufactured in Comparative Example 3.

[0025] Figure 9 is a graph showing the results of 13C-NMR analysis of the silicon carbon composite manufactured in Comparative Example 4.

[0026] Figure 10 is a graph showing the results of 13C-NMR analysis of the silicon carbon composite manufactured in Comparative Example 5.

[0027] Figure 11 shows a method for separating peaks and analyzing waveforms based on the 13C-NMR analysis results of a silicon carbon composite.

[0028] Hereinafter, the present invention will be described in more detail to facilitate understanding. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0029] It should be understood that the terms “include,” “comprising,” or “having” used in this specification are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0030] Furthermore, when we say that a part of a layer or the like is "above" or "on" another part, this includes not only cases where it is "directly above" that part, but also cases where there is another part in between. Conversely, when we say that a part is "directly above" another part, it means that there is no other part in between. Furthermore, when we say that a part is "above" or "on" a reference part, it means that it is located above or below that reference part, and does not necessarily mean that it is located "above" or "on" in the direction opposite to gravity.

[0031] In this specification, the expression “p to q” means a range greater than or equal to p and less than or equal to q, and this range includes the two end values ​​p and q.

[0032] The terms and words used in this specification should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0033] As used herein, the singular expression of a term includes the plural expression unless the context clearly indicates otherwise.

[0034] Hereinafter, preferred embodiments of the present invention will be described in detail. However, the embodiments of the present invention may be modified in various ways, and the scope of the present invention is not limited to the embodiments described below.

[0035] In this specification, 13C-NMR analysis is performed under the following conditions.

[0036] < NMR measurement conditions >

[0037] Solid 400MHz WB (wide bore) NMR system

[0038] MAS(magic angle spinning)rate: 12.5kHz

[0039] Spectral frequency(sfo1): 100.64 MHz (13C)

[0040] Temperature: ambient temperature

[0041] 13C chemical shift reference: adamantane (s) at 38.6 ppm (of CH group at higher frequency)

[0042] Pulse program: 1D CPMG (Carr-Purcell-Meiboom-Gill) MAS

[0043] Spectral width (sw): 50kHz

[0044] Acquisition time: 0.96 s

[0045] Carrier frequency (o1p) at 70 ppm

[0046] Pulse length (p1): 3.5㎲

[0047] Recycle delay (d1):60s

[0048] Number of scans: 1k~5k

[0049] In one embodiment of the present specification, a CPMG (Carr-Purcell-Meiboom-Gill) spectrum obtained through an experiment can be used to generate a superimposed echo using a Python script embedded in Bruker Topspin 4.1, and then a one-dimensional (1D) spectrum can be generated through a Fourier transform. Spectral decomposition can be performed on the obtained 1D spectrum using Bruker Topspin 4.1.

[0050] In this specification, the intensity of a peak means a value obtained by deconvolving a 13C-NMR spectrum by peak, fitting it with a 'Gaussan / Lorentzian' model, and then integrating the area under the resulting Gaussian function graph.

[0051] In this specification, the expression "a peak is located between X ppm and Y ppm" means that the peak of the peak exists within the range between X ppm and Y ppm. Therefore, when calculating the intensity of a peak, rather than simply calculating the area between X ppm and Y ppm, the entire area of ​​the peak within that range is taken into consideration for the calculation.

[0052] Peak deconvolution (waveform analysis) of the spectrum obtained from 1D 13C CPMG MAS NMR measurements was performed using DMFIT (64bit, release#20190125) NMR software, and the detailed waveform analysis conditions are as follows.

[0053] -. After importing the obtained spectrum into the DMFIT program, select ‘Gaussian / Lorentzian’ as the fitting model for waveform analysis.

[0054] -. The parameters used for analysis consist of peak amplitude, peak position, peak half-maximum width, and Gaussian / Lorentzian fraction (xG / (1-x)L), and fitting was performed after setting appropriate initial values ​​(xG / (1-x)L = fixed to 0.5).

[0055] -. In order to obtain accurate peak intensities, the intensity of the spinning sideband dependent on each peak was introduced into the fitting.

[0056] -. The fitting conditions used were nParVar = 15, Step = 1, Thresh = 0.001, and fitting was performed repeatedly until an appropriate convergence value was reached.

[0057] -. For waveform analysis, three or more main peaks and three spinning sidebands dependent on them were applied to obtain the intensity of each peak.

[0058] The above spinning sideband refers to a peak derived from peak A, peak B, and peak C as the sample rotates due to a magnetic field. To minimize the spinning sideband, MAS (Magic Angle Spinning) can be used, and when spinning sidebands are generated even with MAS (Magic Angle Spinning), when calculating the intensity of the peak, the sum of the area of ​​the main peak and the area of ​​the spinning sideband peak derived from the main peak can be used to calculate the intensity of each peak.

[0059] In one embodiment of the present specification, the peak of a spinning sideband derived from each peak means a peak located at a distance of the MAS rate (12.5 kHz) from the center of the main peak.

[0060] A silicon carbon composite according to one embodiment of the present invention is characterized in that it has peak A present in the range of 130 ppm to 150 ppm, peak B present in the range of 110 ppm to 130 ppm, and peak C present in the range of 15 ppm to 40 ppm when analyzed by 13C-NMR, and satisfies the following equation 1.

[0061] [Formula 1]

[0062] 0.3≤ Peak C intensity / (Peak A intensity + Peak B intensity) ≤2.1

[0063] The above peak A intensity is the sum of the areas of peaks of peak A and spinning side bands derived from peak A,

[0064] The above peak B intensity is the sum of the areas of peaks of peak B and spinning side bands derived from peak B,

[0065] The above peak C intensity is the sum of the areas of peaks of peak C and spinning side bands derived from peak C.

[0066] Although the absence of peak C offers the advantage of high capacity and efficiency, if the ratio is less than 0.3, the absence of silicon carbide may degrade the aqueous processability of the slurry. Furthermore, if the ratio of peak C is greater than 2.1, a large amount of silicon carbide that does not contribute to capacity efficiency is formed, resulting in poor initial performance.

[0067] The above peak A is present in the range of 135 ppm to 145 ppm, for example, at 140 ppm, the above peak B is present in the range of 120 ppm to 125 ppm, for example, at 122 ppm, and the above peak C may be present in the range of 25 ppm to 27 ppm, for example, at 26 ppm. Peak A is a peak derived from a carbon of a fully substituted linear sp2 structure, and peak B is a peak derived from an unsubstituted or partially substituted sp 2 Peaks originating from carbon in the structure, peak C is sp 3 It means a peak including a bond and a silicon carbide bond. According to one embodiment, the silicon carbon composite is a composite of Si and C, wherein Si and C (e.g., graphite) are present respectively. In the present specification, the silicon carbon composite may be expressed as Si / C. The silicon carbon composite may be composed of Si and C that are not bonded to each other, but may include additional components as needed. For example, the silicon carbon composite may or may not include silicon carbide, expressed as SiC. When the silicon carbon composite includes silicon carbide, the content thereof is 3 wt% or less. The silicon carbon composite may exist in a crystalline, amorphous, or mixed state thereof. According to one example, C in the silicon carbon composite may exist in an amorphous state.

[0068] According to one embodiment, the silicon carbon composite may be a porous carbon particle and a particle having silicon provided on at least a portion of the interior and surface of the porous carbon particle; or a porous silicon particle and a particle having carbon provided on at least a portion of the interior and surface of the porous silicon particle.

[0069] According to one embodiment, the silicon-carbon composite is a particle having porous carbon particles and silicon provided on at least a portion of the interior and surface of the porous carbon particles. The silicon can be formed by depositing silicon on the porous carbon particles using silane gas. If necessary, a carbon layer can be further formed on the surface of the silicon-carbon composite. By the carbon layer, the conductivity is provided, and the initial efficiency, life characteristics, and battery capacity characteristics of the secondary battery can be improved. The total weight of the carbon layer can be comprised in an amount of 5 wt% to 40 wt% based on a total of 100 wt% of the silicon-carbon composite particles. The carbon layer can include at least one of amorphous carbon and crystalline carbon.

[0070] According to one embodiment, the silicon-carbon composite may be a porous silicon particle and a particle having carbon provided on at least a portion of the interior and surface of the porous silicon particle. This may be formed by etching silicon oxide to form a porous silicon-based particle, such as a Si matrix, and then coating carbon. The description of the carbon layer described above may be applied to the carbon.

[0071] In one embodiment of the present specification, in order to satisfy the above peak ratio in a silicon carbon composite material by depositing silicon on porous carbon, at least one of a method of lowering the silicon deposition temperature and a method of lowering the coating temperature in a carbon coating process after manufacturing the silicon carbon composite can be performed.

[0072] Specifically, a step of placing carbon powder into a tubular furnace, flowing nitrogen gas to create an inert atmosphere, gradually increasing the temperature to heat at a temperature of 300°C to 500°C, and then gradually increasing the temperature again to heat at a temperature of 800°C to 1000°C can be performed.

[0073] Afterwards, the obtained powder is mixed with an acid solvent and centrifuged to obtain a precipitate. The obtained powder is neutralized in an alkaline solvent and then dried to obtain a porous carbon structure. At this time, the temperature at which the carbon particles are heated in the alkaline solvent may be 700°C to 900°C.

[0074] The above porous carbon structure can be placed in a horizontal furnace and SiH4 / He gas can be flowed at 600°C to 800°C to obtain a silicon carbon composite.

[0075] The method may further include a step of placing the silicon carbon composite obtained through the above process into an electric furnace, heat-treating it, and then flowing hydrocarbon gas at 600°C to 800°C to form a carbon layer.

[0076] In one embodiment of the present specification, in the case of a method of complexing carbon into porous silicon, the method may be performed by at least one of a method of lowering the carbon complexing temperature and a method of lowering the heat treatment temperature of the porous silicon raw material prior to carbon complexing in order to satisfy the above peak ratio.

[0077] Specifically, silicon powder is placed in a horizontal tube, argon gas is flowed to create an inert atmosphere, and the temperature is gradually increased to induce disproportionation. At this time, the heat treatment temperature may be 750°C to 1200°C, and specifically, 800°C to 1100°C.

[0078] After this, the heat-treated SiO x After removing it from the tube, a step of immersing it in an HF aqueous solution and stirring it to remove the SiO2 phase can be performed.

[0079] After drying the porous silicon obtained above, a carbon layer can be formed by chemical vapor deposition (CVD) using a hydrocarbon gas at 550°C to 850°C. The hydrocarbon gas can be at least one hydrocarbon gas selected from the group consisting of methane, ethane, propane, and acetylene.

[0080] If the above deposition / coating temperature is lower than the above range, silicon carbide is not formed, resulting in poor aqueous slurry processability.

[0081] According to one embodiment, the silicon carbon composite may be represented as SiOxCy (x is 0 to 0.5, y is 1.0 to 3.0). Specifically, x may be 0 to 0.3, or 0.05 to 0.3, and y may be 1.3 to 2.8, or 1.5 to 2.7.

[0082] If the ratio of x exceeds the above range, the ratio of silicon oxide in the silicon carbon composite increases, which may lead to an increase in irreversible lithium phases and a decrease in capacity and efficiency. In addition, if the ratio of y satisfies the above range, a high-capacity, long-life secondary battery can be obtained by achieving appropriate electrical conductivity and silicon ratio.

[0083] According to one embodiment, the silicon carbon composite has a surface area of ​​0.5 to 10 m when measured by the BET method. 2 / g, and the pore volume can be 0.005 to 0.03 cm 3 / g, and the pore size by the BET method may be 10 to 20 nm. The silicon carbon composite has a pore volume of 0.005 to 0.03 cm as measured by the mercury penetration method. 3 / g could be.

[0084] According to one embodiment, the silicon carbon composite is D 90 The particle size can be 5 to 15 ㎛, D 50 The particle size can be 1 to 10 ㎛, D min This 1 to 3 μm, D max may be 17 to 23 ㎛. In this specification, the average particle diameter (D 50 ) can be defined as the particle size corresponding to 50% of the volume accumulation in the particle size distribution curve. The average particle size (D 50 ) can be measured, for example, using a laser diffraction method. The laser diffraction method can generally measure particle diameters from the submicron range to several mm, and can obtain results with high reproducibility and high resolution.

[0085] One embodiment provides a negative electrode active material comprising a silicon carbon composite according to the above-described embodiments.

[0086] One embodiment provides a negative electrode composition comprising a negative electrode active material, a binder, and a conductive material according to the above-described embodiment.

[0087] According to one embodiment, the silicon carbon composite may be included in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the negative electrode active material, for example, in an amount of 1 to 10 parts by weight.

[0088] According to one embodiment, the negative electrode active material may further include a carbon-based active material. The carbon-based active material may be included in an amount of 90 parts by weight or more and 99.9 parts by weight or less, for example, 90 parts by weight to 99 parts by weight, based on 100 parts by weight of the total negative electrode active material included in the negative electrode composition. The carbon-based active material may include at least one of natural graphite and artificial graphite. When the carbon-based active material includes both natural graphite and artificial graphite, the weight ratio of the artificial graphite and the natural graphite may be 1:9 to 9:1, for example, 3:7 to 7:3. For example, based on 100 parts by weight of the carbon-based active material, the natural graphite may be 10 to 70 parts by weight; and the artificial graphite may be 30 to 90 parts by weight.

[0089] The above natural graphite refers to graphite that occurs naturally, and examples thereof include scaled graphite, scaly graphite, or soil graphite. The above natural graphite has the advantages of being abundant, low in price, having high theoretical capacity and compaction density, and being capable of realizing high output.

[0090] In one example, the natural graphite may be spheroidized natural graphite, and may have a spheroidization degree of 0.9 or more. In one example, the natural graphite is spheroidized natural graphite and may have a tap density of 0.9 g / cc or more.

[0091] In this specification, the degree of sphericity may be a value obtained by dividing the circumference of a circle having the same area as the projected image when the particle is projected by the perimeter of the projected image. The degree of sphericity may be obtained from an SEM image, or alternatively, may be measured using a particle shape analyzer, such as a Malvern sysmex FPIA3000. In addition, the crystal size can be confirmed through XRD analysis.

[0092] According to one embodiment of the present invention, the cathode composition further includes a binder and a conductive material, and the binder may be an aqueous binder.

[0093] The above binder may include at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluoroelastomer, polyacrylic acid, and materials in which hydrogens of these are substituted with Li, Na, Ca, etc., and may also include various copolymers thereof.

[0094] The conductive material is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, paneth black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0095] According to one embodiment, the aqueous binder may be included in an amount of 1 to 5 wt%, for example, about 3 to 4 wt%, based on the solid content of the negative electrode composition, and the conductive material may be included in an amount of 0.1 to 2 wt%, for example, about 1 wt%, based on the solid content of the negative electrode composition.

[0096] One embodiment of the present invention provides a cathode comprising a cathode composition according to the above-described embodiments.

[0097] Specifically, the negative electrode may include a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The negative electrode active material layer includes the negative electrode composition according to the embodiment described above.

[0098] The above negative electrode active material layer can be formed by applying a negative electrode slurry containing the above-described negative electrode composition to at least one surface of a negative electrode current collector, drying, and rolling.

[0099] The negative current collector may be any conductive material that does not cause chemical changes in the battery, and is not particularly limited thereto. For example, the current collector may be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like. Specifically, a transition metal that readily absorbs carbon, such as copper or nickel, may be used as the current collector. The current collector may have a thickness of 6 μm to 20 μm, but the thickness of the current collector is not limited thereto.

[0100] The above-described cathode slurry may include a solvent for forming the cathode slurry. Specifically, the solvent for forming the cathode slurry may include at least one selected from the group consisting of distilled water, ethanol, methanol, and isopropyl alcohol, specifically distilled water, in order to facilitate dispersion of the components.

[0101] One embodiment of the present invention provides a lithium secondary battery including a negative electrode, a positive electrode, and a separator according to the above-described embodiment.

[0102] The above positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and including the positive electrode active material.

[0103] In the above positive electrode, the positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector may typically have a thickness of 3 to 500 ㎛, and fine unevenness may be formed on the surface of the current collector to increase the adhesive strength of the positive electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0104] The above positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; or a compound having the chemical formula Li 1+c1 Mn 2-c1 Lithium manganese oxides such as O4(0≤c1≤0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; chemical formula LiNi 1-c2 M c2 Ni-site type lithium nickel oxide represented by O2 (wherein, M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and satisfies 0.01≤c2≤0.3); chemical formula LiMn 2-c3 M c3Lithium manganese composite oxide represented by O2 (wherein M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 0.01≤c3≤0.1) or Li2Mn3MO8 (wherein M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); LiMn2O4, etc., in which a part of Li in the chemical formula is replaced with an alkaline earth metal ion, but is not limited thereto. The positive electrode may be Li-metal.

[0105] The above-described positive electrode active material layer may include a positive electrode conductive material and a positive electrode binder together with the positive electrode active material described above.

[0106] At this time, the positive electrode conductive material is used to provide conductivity to the electrode, and in the battery to be constructed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. Specific examples include 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, summer black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like, and one of these may be used alone or a mixture of two or more may be used.

[0107] In addition, the positive electrode binder plays a role in improving the adhesion between positive electrode active material particles and the adhesiveness between the positive electrode active material and the positive electrode current collector. Specific examples thereof include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof.

[0108] The separator separates the negative and positive electrodes and provides a passage for lithium ions to move. Any separator commonly used in secondary batteries can be used without any particular restrictions, and in particular, one that has low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, can be used. In addition, a conventional porous non-woven fabric, for example, a non-woven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. can also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength can be used, and can optionally be used in a single-layer or multi-layer structure.

[0109] The above lithium secondary battery may additionally include an electrolyte. Examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0110] Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0111] As the above non-aqueous organic solvent, for example, an aprotic organic solvent such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxolan, formamide, dimethylformamide, dioxolan, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxy methane, dioxolan derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyrropionate, ethyl propionate, etc. can be used.

[0112] In particular, among the above carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are high-viscosity organic solvents with high dielectric constants and thus can be preferably used because they easily dissociate lithium salts. In addition, when low-viscosity, low-dielectric constant linear carbonates such as dimethyl carbonate and diethyl carbonate are mixed and used in an appropriate ratio with these cyclic carbonates, an electrolyte with high electrical conductivity can be produced, so that they can be used even more preferably.

[0113] The metal salt may be a lithium salt, and the lithium salt is a substance that is easily dissolved in the non-aqueous electrolyte, for example, the anion of the lithium salt is F - , Cl - , 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 - One or more selected from the group consisting of can be used.

[0114] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery.

[0115] According to another embodiment of the present invention, a battery module including the secondary battery as a unit cell and a battery pack including the same are provided. The battery module and the battery pack include the secondary battery having high capacity, high rate characteristics, and cycle characteristics, and thus can be used as a power source for medium- to large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

[0116] Hereinafter, examples will be provided to specifically explain the present specification. However, the embodiments described herein may be modified in various ways, and the scope of the present application is not limited to the embodiments described below. The embodiments of the present application are provided to more fully explain the present specification to those of ordinary skill in the art.

[0117]

[0118] <Example 1>

[0119] (1) Preparation of silicon carbon composite 1

[0120] D 50 This 6μm SiO x(0 <x≤1)를 수평식 튜브 (horizontal tube)에 넣은 후, 1500sccm의 속도로 아르곤(Ar) 가스를 1시간동안 흘러줘서 비활성 분위기를 만들어주었다. 그리고 150sccm의 속도로 아르곤 가스를 흘러주었고, 10℃ / min의 속도로 온도를 1000℃까지 증가시킨 후 6시간 동안 유지하여 불균등 반응 (disproportionation)을 유도하였다. 상기 열처리된 SiOx (0<x≤1)를 튜브에서 꺼낸 후, 20 중량비의 HF 수용액에 침지시킨 후, 상온에서 1시간동안 교반하여 SiO2상을 제거하였다. 상기 얻어진 다공성 실리콘은 600℃진공 오븐에 12시간 동안 건조하였다. 이후, 상기 건조된 다공성 실리콘은 CVD 장비를 이용하여 600℃에서 1:9 부피비로 혼합된 아르곤 / 아세틸렌 혼합 가스를 100sccm 속도로 3시간 흘러주어 최종 실리콘 카본 복합체를 제조하였다.

[0121] The ratio of elements in the silicon carbon composite measured by the carbon sulfur analyzer (CS Analyzer) and the oxygen nitrogen hydrogen analyzer (ONH Analyzer) is SiO 0.05 C 2.08 It was.

[0122] (2) Manufacturing of cathode

[0123] An anode slurry was prepared by adding and mixing an appropriate amount of distilled water to a negative electrode active material comprising the above-mentioned silicon carbon composite, natural graphite, and artificial graphite in a weight ratio of 10:15:75; a conductive material comprising carbon black and SWCNT; and a binder comprising carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR) in a weight ratio of 95.3:1:3.6 so that the total solid content was approximately 46 wt%.

[0124] The above cathode slurry was applied to a Cu metal thin film with a thickness of 20 μm and dried at a circulating air temperature of 60°C. Then, after rolling, it was dried in a vacuum oven at 130°C for about a day, and then 1.4875 cm 2 The cathode was manufactured by punching out a circular shape.

[0125] (3) Manufacturing of secondary batteries

[0126] 1.7671cm 2 A Li metal film formed by porous polyethylene was used as the anode. A porous polyethylene separator was placed between the anode and the cathode, and a Li coin half-cell was manufactured by injecting an electrolyte containing 1 M LiPF6 dissolved in a mixed solution of EMC (methyl ethyl carbonate) and EC (ethylene carbonate) at a mixing ratio of 7:3 with additives.

[0127]

[0128] <Example 2>

[0129] (1) Preparation of silicon carbon composite 2

[0130] When the reaction is unequal, the temperature is 900 o A silicon carbon composite was prepared in the same manner as in Example 1, except that a disproportionation reaction was induced in C.

[0131] The ratio of elements in the silicon carbon composite measured by the carbon sulfur analyzer (CS Analyzer) and the oxygen nitrogen hydrogen analyzer (ONH Analyzer) is SiO 0.05 C 2.08 It was.

[0132] (2) Manufacturing of cathode and secondary batteries

[0133] It was manufactured in the same manner as Example 1 except that silicon carbon composite 2 was used.

[0134]

[0135] <Example 3>

[0136] (1) Preparation of silicon carbon composite 3

[0137] CVD carbon coating temperature 800 o It was manufactured in the same manner as Example 1, except that it was carried out in C.

[0138] The ratio of elements in the silicon carbon composite measured by the carbon sulfur analyzer (CS Analyzer) and the oxygen nitrogen hydrogen analyzer (ONH Analyzer) is SiO 0.05 C 2.22 It was.

[0139] (2) Manufacturing of cathode and secondary batteries

[0140] It was manufactured in the same manner as Example 1 except that silicon carbon composite 3 was used.

[0141]

[0142] <Example 4>

[0143] (1) Preparation of silicon carbon composite 4

[0144] Cellulose powder was placed in a tubular furnace, heated to 400°C at a rate of 4°C / min, and heated for 2 hours under a nitrogen atmosphere. Thereafter, the furnace was heated to 900°C at a rate of 4°C / min, and heated for 2 hours under a nitrogen atmosphere. The powder was mixed with sulfuric acid and nitric acid in a volume ratio of 3:1, stirred at 60°C for 2 hours, and then centrifuged to obtain a precipitate. The obtained powder was washed five times with a solvent mixed with ethanol and distilled water in a volume ratio of 1:3, and dried at 120°C for 12 hours. The carbon particles were placed in a KOH solvent, heated at 800°C in a nitrogen atmosphere for 2 hours, to obtain a porous carbon structure. The porous carbon structure was washed three times with distilled water, and then dried at 120°C for more than 12 hours. The porous carbon structure was placed in a horizontal furnace, and SiH4 / He=95 / 5 gas was flowed at a flow rate of 50 ml / min at 700°C for 1 hour to produce a silicon carbon composite. The silicon carbon composite was then placed in the furnace and heat-treated at 800°C for 2 hours. Thereafter, the heat-treated silicon carbon composite was placed in the furnace, and acetylene was flowed at 700°C to react for 3 hours to produce a silicon carbon composite negative electrode active material including a carbon layer on the surface.

[0145] The ratio of elements in the silicon carbon composite measured by the carbon sulfur analyzer (CS Analyzer) and the oxygen nitrogen hydrogen analyzer (ONH Analyzer) is SiO 0.03 C 2.15 It was.

[0146]

[0147] (2) Manufacturing of cathode and secondary batteries

[0148] It was manufactured in the same manner as Example 1 except that silicon carbon composite 4 was used.

[0149]

[0150] <Example 5>

[0151] (1) Preparation of silicon carbon composite 5

[0152] 550 o It was manufactured in the same manner as Example 4, except that a surface carbon layer was formed with acetylene gas in C.

[0153] The ratio of elements in the silicon carbon composite measured by the carbon sulfur analyzer (CS Analyzer) and the oxygen nitrogen hydrogen analyzer (ONH Analyzer) is SiO 0.04 C 2.38 It was.

[0154]

[0155] (2) Manufacturing of cathode and secondary batteries

[0156] It was manufactured in the same manner as Example 1 except that silicon carbon composite 5 was used.

[0157]

[0158] <Comparative Example 1>

[0159] (1) Preparation of silicon carbon composite 6

[0160] When the reaction is disproportionate, the temperature is 700 o A silicon carbon composite was prepared in the same manner as in Example 1, except that a disproportionation reaction was induced in C.

[0161] (2) Manufacturing of cathode and secondary batteries

[0162] It was manufactured in the same manner as Example 1, except that silicon carbon composite 6 was used.

[0163]

[0164] Comparative Example 2

[0165] (1) Preparation of silicon carbon composite 7

[0166] A silicon carbon composite was manufactured using SiH4 / He=95 / 5 gas at 600°C, and the same method as in Example 4 was used, except that no surface carbon coating layer was formed.

[0167] (2) Manufacturing of cathode and secondary batteries

[0168] It was manufactured in the same manner as Example 1, except that silicon carbon composite 7 was used.

[0169]

[0170] <Comparative Example 3>

[0171] (1) Preparation of silicon carbon composite 8

[0172] A crosslinkable composition was prepared by mixing 775 g of DVB570 (manufactured by Shinil Chemical Co., Ltd., mainly composed of 57.0 mass% divinylbenzene and 38.9 mass% vinylethylbenzene, with a divinylbenzene content of about 60 mass%), 531 g of methylhydrogenpolysiloxane (content of silicon-bonded hydrogen atoms = 1.58 mass% of trimethylsiloxy groups blocked at both ends of the molecular chain) having a viscosity of 20 mPa s (an amount such that the silicon-bonded hydrogen atoms in the copolymer are about 1 mol per 1 mol of vinyl groups in the DVB570) and 10 ppm of a 1,3-divinyltetramethyldisiloxane complex platinum catalyst as platinum metal. Thereafter, a cured product was prepared by curing the composition at 120°C in air.

[0173] 969 g of the above-mentioned cured product was placed in an alumina boat of the SSA-S grade, and the boat was placed in a decompression furnace. The decompression furnace was then maintained at a reduced pressure for 10 minutes, and then returned to normal pressure in high-purity nitrogen (99.99%). This operation was repeated once in total. Thereafter, while supplying high-purity nitrogen at a flow rate of 2 L / min, the temperature was increased at a rate of 2°C / min, and the furnace was fired at 600°C for 2 hours. 591 g of the obtained fired product was placed in an alumina boat of the SSA-S grade, and the boat was placed in a muffle furnace. The furnace was then maintained at a reduced pressure for 60 minutes, and then returned to normal pressure in high-purity nitrogen (99.99%). This operation was repeated once in total. Thereafter, while supplying high-purity argon at a flow rate of 100 mL / min, the temperature was increased at a rate of 5°C / min and the sintering was performed at 1000°C for 1 hour to obtain a sintered product. The obtained sintered product was pulverized with an airflow pulverizer and then classified using a precision air classifier to obtain a silicon carbon composite.

[0174] The ratio of elements in the silicon carbon composite measured by the carbon sulfur analyzer (CS Analyzer) and the oxygen nitrogen hydrogen analyzer (ONH Analyzer) is SiO 1.53 C 1.46 It was.

[0175] (2) Manufacturing of cathode and secondary batteries

[0176] It was manufactured in the same manner as Example 1 except that silicon carbon composite 8 was used.

[0177]

[0178] Comparative Example 4

[0179] (1) Preparation of silicon carbon composite 9

[0180] After crushing low-crystalline silicon (Pure Si) into small pieces, the crushed crystalline silicon was placed in an electric furnace and reacted at 400°C in an oxygen atmosphere for 2 hours. Separately prepared pitch-based carbon was crushed, and then the silicon and pitch were mixed at 60°C for 3 hours, and then transferred to a reactor and heat-treated at 600°C. The silicon-carbon composite that went through the heat treatment process was transferred to a crusher and crushed to have a D50 of about 12 μm. Afterwards, the crushed Si / C negative electrode active material was placed in an electric furnace and acetylene was flowed in at 950°C to react for 3 hours to form a carbon coating layer on the surface. The Si / C active material with the carbon coating layer was placed in a crusher to ultimately manufacture a Si / C negative electrode active material with a D50 of 6 μm.

[0181] The ratio of elements in the silicon carbon composite measured by the carbon sulfur analyzer (CS Analyzer) and the oxygen nitrogen hydrogen analyzer (ONH Analyzer) is SiO 1.1 C 5.6 It was.

[0182] (2) Manufacturing of cathode and secondary batteries

[0183] It was manufactured in the same manner as Example 1 except that silicon carbon composite 9 was used.

[0184]

[0185] Comparative Example 5

[0186] (1) Preparation of silicon carbon composite 10

[0187] The dried porous silicon was manufactured in the same manner as in Example 1, except that a mixed argon / acetylene gas in a volume ratio of 1:9 was flowed at a rate of 100 sccm for 3 hours at 300°C.

[0188] (2) Manufacturing of cathode and secondary batteries

[0189] It was manufactured in the same manner as Example 1 except that silicon carbon composite 10 was used.

[0190]

[0191] The results of 13C-NMR analysis of the negative electrode active materials manufactured in the above examples and comparative examples are shown in Figures 1 to 10 and Table 1 below.

[0192] Specifically, as shown in Fig. 11, the 13C-NMR spectrum of each negative electrode material was analyzed for waveforms through Gaussian / Lorentzian fitting, and the area under the graph of peak A, peak B, and peak C obtained through waveform analysis and the area under the spinning sideband peak derived from each peak were integrated to calculate the peak C intensity / (peak B intensity + peak A intensity).

[0193] Peak APeak BPeak C RatioPosition (ppm)Intensity (based on B peak intensity)Position (ppm)IntensityPosition (ppm)Intensity (based on B peak intensity)Peak C / Peak (A+B)Example 11350.811201262.31.28Example 21350.81201262.41.31Example 31350.651201262.61.60Example 41350.671201263.42.02Example 51350.411201260.880.62Comparative Example 11350.731221263.82.22Comparative Example 2-01221-00Comparative Example 31350.101181-00 Comparison Example 41350.081221-00 Comparison Example 51370.891241270.180.095

[0194] The discharge capacity, initial efficiency, capacity retention rate, and slurry viscosity change rate of the above examples and comparative examples were measured and are listed in Table 2 below.

[0195] <Discharge capacity, initial efficiency, capacity retention rate>

[0196] The 1st and 2nd cycles were charged and discharged at 0.1C, and from the 3rd to the 299th cycles, the charging and discharging was performed at 0.5C. The 300th cycle was terminated in a charged state (with lithium in the negative electrode).

[0197] Charging conditions: CC (constant current) / CV (constant voltage) (5mV / 0.005C current cut-off)

[0198] Discharge conditions: CC (constant current) condition 1.5 V

[0199] Based on the results of a single charge / discharge cycle, the discharge capacity (mAh / g) and initial efficiency (%) were derived. Specifically, the initial efficiency (%) was derived using the following calculation.

[0200] Initial efficiency (%) = (1-time discharge capacity / 1-time charge capacity) × 100

[0201] The capacity retention rate was derived by the following calculations.

[0202] Capacity retention rate (%) = (299 discharge capacity / 1 discharge capacity) × 100

[0203]

[0204] <Slurry viscosity change rate>

[0205] To measure the rate of change in slurry viscosity, a slurry was prepared by mixing graphite: the silicon carbon composite: carbon black: CMC: PAA in a weight ratio of 77: 20: 1: 1: 1. The shear viscosity of the prepared slurry was measured at a shear rate of 1 Hz, and the change over time was measured and compared.

[0206] The rate of change (%) of shear viscosity was derived using the following formula.

[0207] Change rate of shear viscosity (%) = ((shear viscosity of slurry after 2 days - viscosity of slurry immediately after mixing) / viscosity of slurry immediately after mixing) × 100

[0208]

[0209] <Pouch volume change rate>

[0210] Graphite: The silicon carbon composite: carbon black: CMC: PAA were mixed in a weight ratio of 77: 20: 1: 1: 1 to prepare a slurry, 20 g of the prepared slurry was placed in a pouch, sealed, and stored at 40°C for 2 days. The volume was measured and the rate of change was compared.

[0211]

[0212] Total discharge capacity (mAh / g) Initial efficiency (%) Capacity retention (%) Slurry viscosity change (%, after 2 days) Pouch volume change (%, @40℃, after 2 days) Example 150 49 1.38 9.0-0.30.0 Example 250 29 1.08 8.9-0.10.0 Example 350 49 0.98 8.1-0.20.0 Example 450 49 1.18 8.5-1.40.1 Example 550 39 1.38 8.3-2.10.7 Comparative Example 1450 88.98 3.6-0.70.3 Comparative Example 250 388.08 4.7-51.734.1 Comparative Example 344 888.18 0.9-5.82.3 Comparative Example 447688.580.2-4.94.4 Comparative example 548287.481.8-10.17.5

[0213] As shown in Table 2 above, Examples 1 to 5, in which the ratio of the intensity of the peak C to the sum of the intensities of peak A and peak B (peak C intensity / (peak B intensity + peak A intensity)) satisfies the range of 0.3 to 2.1, exhibited high capacity and efficiency, and it was confirmed that there was little change in the slurry viscosity change rate and pouch volume change rate.

[0214] Comparative Example 1 corresponds to a case where the ratio of the intensity of the peak C to the sum of the intensities of peak A and peak B (peak C intensity / (peak B intensity + peak A intensity)) exceeds 2.1, and although silicon carbide is excessively formed, there is no significant difference from Examples 1 to 5 in terms of aqueous processability, but it can be confirmed that the effect is inferior to Examples 1 to 5 in terms of capacity efficiency and cycle capacity.

[0215] Comparative Example 2 corresponds to a case where the ratio of the intensity of the peak C to the sum of the intensities of peak A and peak B (peak C intensity / (peak B intensity + peak A intensity)) is less than 0.3, and it can be confirmed that the slurry viscosity change rate and pouch volume change rate are higher than those of Examples 1 to 5. This means that silicon carbide is not formed, resulting in poor aqueous slurry processability.

[0216] For comparative examples 3 and 4, the element content ratios are SiO 1.53 C 1.46 and SiO 1.1 C 5.6 Since the silicon-carbon composite of the present invention did not satisfy the appropriate elemental content ratio of silicon and oxygen, the sp2 bond of carbon was not properly formed, and as a result, the A peak was very small and the C peak did not appear in the 13C-NMR results. As a result, it was inferior in terms of capacity, capacity retention rate, and aqueous processability compared to Examples 1 to 5.

[0217] In Comparative Example 5, the temperature was lowered during the carbon coating process, which prevented proper formation of silicon carbide on the surface of the silicon-carbon composite, resulting in a significant decrease in the intensity of the C peak. Consequently, it can be confirmed that the aqueous slurry processability is inferior to that of Examples 1 to 5.

Claims

A silicon carbon composite having peak A present in the range of 130 ppm to 150 ppm when analyzed by 1.13C-NMR; peak B present in the range of 110 ppm to 130 ppm; and peak C present in the range of 15 ppm to 40 ppm, and satisfying the following formula 1: [Formula 1] 0.3≤ Peak C intensity / (Peak A intensity + Peak B intensity) ≤2.1 The above peak A intensity is the sum of the areas of peaks of peak A and spinning side bands derived from peak A, The above peak B intensity is the sum of the areas of peaks of peak B and the spinning side bands derived from peak B, The above peak C intensity is the sum of the areas of peaks of peak C and the spinning side bands derived from peak C.

2. A silicon carbon composite according to claim 1, wherein peak A exists within a range of 135 ppm to 145 ppm, peak B exists within a range of 120 ppm to 125 ppm, and peak C exists within a range of 23 ppm to 27 ppm.

3. In claim 1, the silicon-carbon composite is a silicon-carbon composite having porous carbon particles and silicon provided on at least a portion of the interior and surface of the porous carbon particles; or porous silicon particles and carbon provided on at least a portion of the interior and surface of the porous silicon particles.

4. In claim 1, the silicon carbon composite is a silicon carbon composite represented by SiOxCy (x is 0 to 0.5, y is 1.0 to 3.0).

5. A negative active material comprising a silicon carbon composite according to any one of claims 1 to 4.

6. A negative electrode composition comprising a negative electrode active material according to claim 5; a binder; and a conductive material.

7. A negative electrode composition according to claim 6, wherein the negative electrode active material further includes a carbon-based active material.

8. A negative electrode composition according to claim 7, wherein the silicon carbon composite is contained in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the negative electrode active material.

9. An anode composition according to claim 7, wherein the carbon-based active material comprises at least one of artificial graphite and natural graphite.

10. A cathode comprising a cathode composition according to claim 6.

11. A lithium secondary battery comprising a negative electrode, a positive electrode, and a separator according to claim 10.

12. A battery module including a lithium secondary battery according to claim 11.

13. A battery pack comprising a lithium secondary battery according to claim 11.

14. A battery pack comprising a battery module according to claim 12.

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