Negative electrode and lithium secondary battery comprising same
The negative electrode with an amorphous carbon-coated artificial graphite and controlled milling process addresses the energy density and lithium precipitation issues in lithium secondary batteries, achieving improved energy density and rapid charging.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- LG ENERGY SOLUTION LTD
- Filing Date
- 2025-12-17
- Publication Date
- 2026-07-02
Abstract
Description
Negative electrode and lithium secondary battery including the same
[0001] The present application claims the benefit of priority based on Korean Patent Application No. 10-2024-0194794 filed December 23, 2024 and Korean Patent Application No. 10-2025-0199515 filed December 15, 2025, the entire contents of which are incorporated herein.
[0002] The present invention relates to a negative electrode and a lithium secondary battery including the same.
[0003] With growing interest in environmental issues, extensive research is being conducted on electric vehicles that can replace fossil fuel-powered vehicles, such as gasoline and diesel cars, which are a major cause of air pollution. Lithium-ion batteries, which exhibit high energy density, high discharge voltage, and output stability, are primarily used as the power source for electric vehicles.
[0004] Generally, a lithium secondary battery comprises a positive electrode, a negative electrode, a separator, and an electrolyte, and the positive electrode or negative electrode is manufactured by mixing a positive active material or a negative active material with a binder, etc., dispersing it in a solvent to prepare a slurry, applying the slurry to the surface of an electrode current collector, and drying it to form an electrode active material layer.
[0005] Meanwhile, as the above-mentioned negative electrode active material, a carbon-based active material capable of reversible lithium ion intercalation and extraction while maintaining structural and electrical properties may be used. Various forms of carbon-based materials, such as artificial graphite, natural graphite, and hard carbon, have been applied as the above-mentioned carbon-based active material; among these, graphite-based active materials are the most widely used because they can guarantee the lifespan characteristics of lithium secondary batteries due to their excellent reversibility.
[0006] Among these, synthetic graphite has the advantage of having a uniform particle size and structure and excellent conductivity compared to natural graphite; however, due to its low tap density, it has limitations in achieving high energy density.
[0007] The present invention aims to provide a negative electrode that increases the energy density of a lithium secondary battery and has the effect of mitigating the problem of lithium precipitation during high-speed charging, and a lithium secondary battery including the same.
[0008] [1] The present invention is a cathode comprising a cathode current collector and a cathode composite layer provided on the cathode current collector,
[0009] The above cathode composite layer comprises a cathode active material comprising artificial graphite particles; and an amorphous carbon coating layer provided on the artificial graphite particles, and
[0010] The above-mentioned negative electrode active material comprises 30 mg to 170 mg of nitrogen element and 600 mg to 1,000 mg of oxygen element per 1 kg of the above-mentioned negative electrode active material, and
[0011] The above-mentioned cathode has an orientation index according to Formula 1 below of 5 to 20.
[0012] [Equation 1]
[0013] OI=A(004) / A(110)
[0014] In the above Equation 1,
[0015] OI is the orientation index of the cathode, and
[0016] A(004) is the peak area of the (004) plane appearing in the XRD spectrum of the above cathode, and
[0017] A (110) is the peak area of the (110) plane appearing in the XRD spectrum of the above cathode.
[0018] [2] The present invention provides a cathode according to [1], wherein the cathode active material further comprises 200 mg to 600 mg of hydrogen element per 1 kg of the cathode active material.
[0019] [3] The present invention provides a cathode in which the tap density of the cathode active material in [1] or [2] is 0.97 g / cc or higher.
[0020] [4] The present invention provides a cathode in which, in at least one of [1] to [3], the artificial graphite particles are in the form of secondary particles assembled from two or more primary particles.
[0021] [5] The present invention, in at least one of [1] to [4], wherein the BET specific surface area of the negative electrode active material is 0.7 m 2 / g to 1.6m 2 Provides a cathode of / g.
[0022] [6] The present invention provides a cathode in which, in at least one of [1] to [5], the D / G ratio, which is the ratio of the D band intensity to the G band peak intensity in the Raman spectrum of the cathode active material, is 0.60 or higher.
[0023] [7] The present invention, in at least one of [1] to [6], wherein the half-width of the G band in the Raman spectrum of the cathode active material is 20 cm -1 up to 40cm -1 Provides phosphorus, a cathode.
[0024] [8] The present invention is, in at least one of [1] to [7], the D of the negative electrode active material 50 This provides a cathode having a size of 10㎛ to 20㎛.
[0025] [9] The present invention provides a cathode having a tolerance index of 10 to 20 in at least one of [1] to [8].
[0026]
[0010] The present invention provides a lithium secondary battery comprising a cathode according to at least one of [1] to [9]; a positive electrode; a separator interposed between the cathode and the positive electrode; and an electrolyte.
[0027] The cathode according to the present invention comprises a cathode active material having excellent tap density, specific surface area, particle size, and coating uniformity, and accordingly, the orientation of the cathode is optimized, thereby having the effect of improving the energy density and rapid charging performance of a lithium secondary battery.
[0028] Hereinafter, the present invention will be described in more detail to aid in understanding the invention.
[0029]
[0030] In the present invention, the “orientation index (OI)” is a value representing the degree of orientation of the cathode, which is the ratio of the (004) plane peak area to the (110) plane peak area appearing in the XRD spectrum of the cathode. The peak area can be measured in the following manner.
[0031] A specimen is prepared by cutting the cathode to be measured to the size of the sample holder, and then securely attached to a glass plate using double-sided tape so that it does not lift. Next, the specimen is fixed to a PMMA holder in an XRD measuring instrument (Bruker D8 Endeavor) using modeling clay. X-ray diffraction analysis is performed using a Bruker D8 Endeavor (light source: Cu Kα, λ=1.54Å) equipped with a LynxEye XE-T position sensitive detector, under conditions of a step size of 0.016° and a total scan time of approximately 16 minutes, for the FDS 0.5°, 2θ=53°~56° ((004) plane) and 2θ=76°~79° ((110) plane) regions. The measured data is fitted to a single peak using an analytical function to measure the (110) plane peak area and the (004) plane peak area.
[0032] In the present invention, the “BET specific surface area” is calculated through the BET (Brunauer-Emmett-Teller) multi-point method from the nitrogen adsorption isotherm under a 77K liquid nitrogen atmosphere obtained using a nitrogen adsorption analyzer (e.g., MicrotracBEL, BELSORP-MAX).
[0033] In the present invention, “tap density” can be measured using a method commonly used in the industry to measure the degree of filling of a sample per unit volume. For example, it may be the density (sample weight / volume) calculated by applying a constant force to a measuring container containing a sample in accordance with the measuring instruments and methods specified in ASTM B527 and the change in volume. Specifically, it can be measured by using a GEOPYC 1360 tap density meter from Micromeritics and vibrating it until a horizontal force of 108 N is applied.
[0034] In the present invention, “D 50 "This refers to the particle size corresponding to 50% of the volume cumulative amount in the volume cumulative particle size distribution of the corresponding particle powder, and can be measured using the laser diffraction method. For example, after dispersing the cathode active material powder in a dispersion medium, it can be introduced into a commercially available laser diffraction particle size measuring device (e.g., Malvern, Mastersizer 3000), irradiated with ultrasound of approximately 28 kHz at an output of 60 W, and then obtained a volume cumulative particle size distribution graph, and the particle size at the point where the volume cumulative amount is 50% in the obtained volume cumulative particle size distribution graph can be measured.
[0035] In the present invention, the “Raman spectrum” can be obtained by Raman spectroscopic analysis using a laser of wavelength 514.5 nm using a Raman spectrometer (e.g., Jasco NRS-2000). Here, the D / G ratio is 1,360 ± 50 cm⁻¹. -11,580±50cm for the maximum peak intensity of the D band at -1 It refers to the ratio of the maximum peak intensity of the G band at. The Full Width at Half-Maximum (FWHM) of the G band refers to the width at half the maximum intensity of the G band in the Raman spectrum.
[0036]
[0037] As a negative electrode active material, artificial graphite offers excellent purity and uniformity, enabling stable performance. It also has the advantage of fast charging and discharging speeds due to numerous lithium ion pathways, making it suitable for high-speed charging. However, it has limitations in that it is relatively susceptible to surface delamination, as the layered structure formed by high-temperature heat treatment can lead to interlayer separation, and reactivity with the electrolyte can increase due to microscopic defects or non-uniform structures generated during the manufacturing process.
[0038] To compensate for these limitations and simultaneously improve charging and output characteristics, a technology for forming a carbon coating layer on artificial graphite particles has been proposed; however, during the process of forming the carbon coating layer, the particles may aggregate due to the coating material, leading to another problem where tap density decreases. Tap density is a factor that significantly affects the processability of slurry and electrode fabrication.
[0039] Therefore, to prevent this problem, the inventors sought to improve tap density by additionally performing a milling process after coating to detach aggregated particles. Since the detached particles are mostly those loosely and weakly attached to the particle surface with random orientation, the degree of orientation increases as the milling intensity increases.
[0040] However, if the milling process is excessive, the degree of orientation increases excessively, which hinders the diffusion of lithium ions and may reduce the charging speed, and damage to the carbon coating layer may also lead to performance degradation due to reduced coating uniformity.
[0041] Accordingly, the present invention aims to provide a negative electrode active material in which such a milling process is appropriately performed to optimize tap density, specific surface area, particle size, and coating uniformity, and thereby provide a negative electrode in which the orientation of the negative electrode is also optimized to improve the energy density and rapid charging performance of the cell.
[0042]
[0043] The present invention will be described in detail below.
[0044]
[0045] <Cathode>
[0046] The present invention relates to a negative electrode, specifically a negative electrode for a lithium secondary battery.
[0047] The above cathode comprises a cathode current collector; and a cathode composite layer provided on the cathode current collector and comprising a cathode active material.
[0048] The orientation index of the above cathode according to Formula 1 below is 5 to 20.
[0049] [Equation 1]
[0050] OI=A(004) / A(110)
[0051] In the above Equation 1,
[0052] OI is the orientation index of the cathode, and
[0053] A(004) is the peak area of the (004) plane appearing in the XRD spectrum of the above cathode, and
[0054] A (110) is the peak area of the (110) plane appearing in the XRD spectrum of the above cathode.
[0055] The orientation index of the cathode according to Formula 1 may be 18 or less, 15 or less, or 13 or less. Additionally, the orientation index of the cathode according to Formula 1 may be 7 or more, 9 or more, 10 or more, or 12 or more. The above numerical ranges may be combined without limitation. Specifically, the orientation index of the cathode according to Formula 1 may be 10 to 20, preferably 10 to 18, more preferably 10 to 15, and even more preferably 12 to 15.
[0056] When the orientation index according to Equation 1 is within the above range, it has the effect of increasing the charge / discharge speed and preventing lithium precipitation. Specifically, if the orientation index exceeds 20, the diffusion path of lithium ions becomes longer, which may cause a problem where the charge / discharge speed decreases and the possibility of lithium precipitation increases. However, considering that it is practically difficult to implement a cathode with an orientation index of less than 5, and that if the orientation index decreases excessively, the movement path of lithium ions may be formed irregularly, the stress distribution inside the cathode may become uneven, and the adhesion between the cathode composite layer and the current collector may decrease, it is desirable that the orientation index be within the above range.
[0057] The above cathode can be manufactured by forming a cathode composite layer by applying, drying, and rolling a cathode slurry, prepared by dispersing a cathode active material in a solvent, onto a cathode current collector. The solvent may be water or an organic solvent such as NMP (N-methyl-2-pyrrolidone), and specifically, it may be water.
[0058] The loading amount of the above cathode is 3.0 mAh / cm² 2 Up to 4.5mAh / cm 2 , specifically 3.0mAh / cm² 2 Up to 4.0mAh / cm² 2 It could be.
[0059] Below, each component forming the above-mentioned cathode is described in detail.
[0060]
[0061] 1) Cathode current collector
[0062] The above-mentioned negative current collector can be any negative current collector commonly used in the field without limitation, and is not particularly limited as long as it has high conductivity without causing chemical changes in the lithium secondary battery, for example. For example, the above-mentioned negative current collector may include at least one selected from copper, stainless steel, aluminum, nickel, titanium, calcined carbon, and aluminum-cadmium alloy, preferably copper.
[0063] The above-mentioned negative current collector may have fine irregularities formed on its surface to strengthen the bonding force of the negative active material, and may be in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.
[0064] The above-mentioned negative current collector may be copper foil.
[0065] The thickness of the above-mentioned cathode current collector may be 3㎛ to 100㎛, specifically 5㎛ to 50㎛, and more specifically 10㎛ to 20㎛.
[0066]
[0067] 2) Cathode composite layer
[0068] The above cathode composite layer may be provided on at least one surface of the cathode current collector, specifically on one surface or both surfaces.
[0069] The above-mentioned cathode composite layer comprises a cathode active material comprising artificial graphite particles; and an amorphous carbon coating layer provided on the artificial graphite particles.
[0070] The above cathode composite layer may further include a binder, a conductive material, a thickener, or a combination thereof.
[0071] Each component forming the above-mentioned cathode composite layer is described in detail.
[0072]
[0073] (a) Cathode active material
[0074] The above-described negative electrode active material comprises artificial graphite particles; and an amorphous carbon coating layer provided on the artificial graphite particles, wherein the negative electrode active material comprises 30 mg to 170 mg of nitrogen and 600 mg to 1,000 mg of oxygen per 1 kg of the negative electrode active material.
[0075] As previously explained, during the milling process after coating, when external force is applied, nitrogen and oxygen present in the atmosphere are adsorbed or doped onto the surface of the graphite or carbon coating layer, thereby increasing the content of nitrogen and oxygen elements in the artificial graphite particles. Therefore, the content of nitrogen and oxygen elements can be used as an indicator to verify whether the milling process was performed properly. In other words, a cathode active material with a nitrogen and oxygen content within the aforementioned range has been manufactured through a milling process of an appropriate level in terms of tap density, specific surface area, and particle size without compromising coating uniformity.
[0076] Specifically, the content of the nitrogen element may be 40 mg or more, 50 mg or more, 60 mg or more, or 70 mg or more per 1 kg of the cathode active material, in which case, an improvement in rapid charging performance can be expected by creating localized electrochemical active sites due to nitrogen element doping. However, an excessively high nitrogen content implies that defects have occurred in the graphite or carbon coating layer and a large amount of nitrogen has been adsorbed or doped into the corresponding area; therefore, to prevent a decrease in initial efficiency and an increase in resistance due to an increase in the specific surface area and defect sites, the content of the nitrogen element may be 160 mg or less, 150 mg or less, or 100 mg or less per 1 kg of the cathode active material. The above numerical ranges may be combined without limitation. For example, the content of the nitrogen element may be 40 mg to 160 mg, preferably 50 mg to 160 mg, and more preferably 50 mg to 160 mg per 1 kg of the cathode active material.
[0077] In addition, the oxygen element content per 1 kg of the above-mentioned cathode active material may be 620 mg or more, or 630 mg or more, and may be 950 mg or less, 900 mg or less, or 800 mg or less. When the oxygen element content is within the above range, the reduction in initial efficiency due to side reactions can be minimized while achieving the aforementioned nitrogen element content.
[0078] Meanwhile, the above-mentioned appropriate level of milling process may mean milling artificial graphite particles with an amorphous carbon coating layer formed thereon at a speed of 10 Hz to 30 Hz. This refers to an additional milling process distinct from the milling performed during the process of manufacturing artificial graphite particles in the form of secondary particles, that is, the milling performed before the formation of the carbon coating layer. Since defects generated during the milling performed before the formation of the carbon coating layer are recovered during the graphitization process, they do not significantly affect the nitrogen element content.
[0079] As mentioned above, since the aggregation between particles caused by the formation of the carbon coating layer can reduce tap density and lower the degree of orientation due to random orientation, in the present invention, when manufacturing a cathode active material, a step of milling artificial graphite particles at the above speed is performed after forming the carbon coating layer.
[0080] The above milling may be mechanical milling, such as impact milling, pin milling, hammer milling, etc., or ball milling. Specifically, the above mechanical milling may be impact milling, and more specifically, pin milling.
[0081] The above pin milling can be performed using a rotary device including a pin-shaped disk, and the above hammer milling can be performed using a rotary device including a hammer-shaped disk.
[0082] The above milling speed refers to the speed at which the disk rotates. If the milling speed is less than 10 Hz, the effect of improving tap density is negligible, and if it exceeds 30 Hz, the specific surface area increases excessively, which may reduce initial efficiency and discharge capacity, and the charging characteristics may deteriorate due to damage to the carbon coating layer and increased orientation.
[0083]
[0084] The above-mentioned cathode active material may further include 200 mg to 600 mg of hydrogen element per 1 kg of the above-mentioned cathode active material. Specifically, the content of hydrogen element per 1 kg of the above-mentioned cathode active material may be 250 mg or more, 300 mg or more, or 310 mg or more, and may be 550 mg or less, 500 mg or less, or 400 mg or less. When the content of hydrogen element is within the above range, the reduction in initial efficiency due to side reactions can be minimized while achieving the aforementioned content of nitrogen element.
[0085] The tap density of the above-mentioned cathode active material may be 0.97 g / cc or higher, preferably 0.99 g / cc or higher, and more preferably 1.00 g / cc or higher. This implies that inter-particle aggregation caused by carbon coating is adequately resolved by milling, and has the effect of increasing processability during slurry and electrode manufacturing. Specifically, if the tap density is low, the viscosity of the slurry increases, making mixing difficult, or problems such as filter clogging during the slurry transfer process due to shear thickening may occur. If the amount of solvent in the slurry is increased to resolve these problems, the concentration of the cathode active material decreases. In other words, since the amount of slurry required to obtain the same cathode loading increases and the drying time during the process also increases, it is very important to achieve a tap density above a certain level.
[0086] However, since excessively high tap density can excessively block the movement path of lithium ions within the electrode, the tap density of the negative electrode active material may be 1.15 g / cc or less, preferably 1.10 g / cc or less, and more preferably 1.08 g / cc or less.
[0087] The above artificial graphite is manufactured by heat-treating amorphous carbon at a high temperature (e.g., 2,500°C to 3,200°C), and is distinguished from natural graphite in that it is artificially synthesized graphite.
[0088] The artificial graphite may be in the form of primary particles or secondary particles assembled from two or more primary particles. More specifically, the artificial graphite may be in the form of secondary particles assembled from two or more primary particles.
[0089] When the artificial graphite is in the form of secondary particles, voids may be formed within the artificial graphite, and the voids may be empty spaces formed between primary particles, may be amorphous, or may exist in two or more places.
[0090] The artificial graphite particles described above may be manufactured by mixing a carbon precursor and a binder material, performing mechanical milling (or shaping) and aggregation processes to produce an intermediate in the form of secondary particles, and heat-treating the intermediate at a temperature of 3,000°C or higher to graphitize it, but is not limited thereto. At this time, the carbon precursor may be coal-based heavy oil, petroleum-based heavy oil, tar, pitch, coke, etc., and specifically, may be at least one selected from the group consisting of needle coke, mosaic coke, and coal tar pitch.
[0091] The BET specific surface area of the above cathode active material is 0.7 m² 2 / g to 1.6m 2 / g, preferably 0.7m 2 / g to 1.4m 2 / g, more preferably 0.8m 2 / g to 1.1m 2 It can be / g. This also implies that inter-particle aggregation caused by the carbon coating has been adequately resolved by milling. While a larger BET specific surface area increases the pathways for lithium ion movement and improves charging and output characteristics, excessively large BETs may degrade lifespan characteristics due to reduced initial efficiency and increased side reactions; therefore, it is desirable for the BET specific surface area to be within the above range.
[0092] The D / G ratio, which is the ratio of the D band intensity to the G band peak intensity in the Raman spectrum of the above-mentioned cathode active material, may be 0.60 or higher, preferably 0.63 or higher, more preferably 0.64 or higher, and 0.80 or lower, preferably 0.75 or lower, more preferably 0.70 or lower.
[0093] The full width at half maximum of the G band in the Raman spectrum of the above cathode active material is 20 cm⁻¹ -1 up to 40cm -1 , preferably 22cm -1 to 38cm -1 , more preferably 25cm -1 to 35cm-1 It could be.
[0094] D of the above negative electrode active material 50 The µm can be 10 to 20 µm, preferably 12 to 19 µm, and more preferably 14 to 18 µm. This also implies that inter-particle aggregation caused by the carbon coating has been adequately resolved by milling, and D 50 As this value increases, the orientation index decreases, which can improve filling characteristics; however, if it is excessively large, the tap density may decrease, so it is desirable to be within the above range.
[0095] The above amorphous carbon coating layer may be provided on all or part of the surface of the artificial graphite particles.
[0096] The above amorphous carbon coating layer can be formed by mixing a carbon coating layer precursor with the above artificial graphite particles and then heat treating it.
[0097] The carbon coating layer precursor may include at least one selected from polymer resin and pitch. Specifically, the polymer resin may include at least one selected from the group consisting of sucrose, phenol resin, naphthalene resin, polyvinyl alcohol resin, furfuryl alcohol resin, polyacrylonitrile resin, polyamide resin, furan resin, cellulose resin, styrene resin, polyimide resin, epoxy resin, vinyl chloride resin, and polyvinyl chloride. The pitch may include at least one selected from the group consisting of coal-based pitch, petroleum-based pitch, and mesophase pitch.
[0098] The heat treatment for forming the carbon coating layer can be performed at 1,000°C to 1,500°C, preferably 1,100°C to 1,300°C, and in this case, the uniformity of the carbon coating layer can be increased.
[0099] The content of the amorphous carbon coating layer may be 1% to 5% by weight, preferably 2% to 4% by weight, based on the total weight of the cathode active material. Although the amorphous carbon coating layer can contribute to improving the structural stability of artificial graphite particles, excessive formation of the carbon coating layer may lead to a decrease in initial efficiency and a decline in high-temperature storage performance due to an increase in the specific surface area during cathode rolling; therefore, it is desirable to form the carbon coating layer with a content within the range described above.
[0100] Meanwhile, the content of the above-mentioned cathode active material may be 80% to 99% by weight, preferably 90% to 98% by weight, and more preferably 95% to 97% by weight, based on the total weight of the above-mentioned cathode composite layer.
[0101]
[0102] (b) Binder, conductive agent and thickener
[0103] The above binder is a component that assists in the bonding between the active material and / or the current collector, and may be included in the above cathode composite layer in an amount of 0.5% to 10% by weight, preferably 1% to 5% by weight.
[0104] The binder may be one or more selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, and fluororubber, preferably styrene-butadiene rubber.
[0105] The above conductive material is a component for further improving the conductivity of the cathode active material, and may be included in the cathode composite layer in an amount of 0.1% to 10% by weight, preferably 0.5% to 5% by weight.
[0106] The above conductive material is not particularly limited as long as it possesses conductivity without causing chemical changes in the battery, and may be one or more selected from the group consisting of, for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fibers or metal fibers; metal powders such as carbon fluoride, aluminum, or 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.
[0107] The above-mentioned thickener may be one or more selected from the group consisting of methylcellulose, ethylcellulose, hydroxyethylcellulose, benzylcellulose, tritylcellulose, cyanoethylcellulose, carboxymethylcellulose (CMC), carboxyethylcellulose, aminoethylcellulose, nitrocellulose, cellulose ether, and carboxymethylcellulose sodium salt (CMCNa), and preferably may be carboxymethylcellulose.
[0108] The content of the thickener may be 0.1% to 3% by weight, preferably 0.5% to 2% by weight, based on the total weight of the cathode composite layer. When the content of the thickener is within the above range, the viscosity of the cathode slurry is appropriately formed during the preparation of the cathode composite layer, and accordingly, a cathode composite layer with a uniform shape and a uniformly distributed cathode active material and binder can be prepared.
[0109]
[0110] Lithium secondary battery
[0111] The above lithium secondary battery may include the aforementioned negative electrode; a positive electrode; a separator interposed between the negative electrode and the positive electrode; and an electrolyte.
[0112] The above anode can be opposite to the above cathode.
[0113] The above positive electrode may include a positive electrode current collector; and a positive electrode active material layer provided on the positive electrode current collector.
[0114] The above positive current collector can be any positive current collector commonly used in the field without limitation, and is not particularly limited as long as it has high conductivity without causing chemical changes in the secondary battery, for example. For example, the above positive current collector may include at least one selected from copper, stainless steel, aluminum, nickel, titanium, calcined carbon, and aluminum-cadmium alloy, preferably aluminum.
[0115] The above positive current collector may have fine irregularities formed on its surface to strengthen the bonding force of the positive active material, and may be in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.
[0116] The above positive current collector can generally have a thickness of 3㎛ to 500㎛.
[0117] The above positive active material layer may include a positive active material.
[0118] The above-mentioned cathode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may include a lithium composite metal oxide comprising lithium and one or more metals such as cobalt, manganese, nickel, or aluminum. More specifically, the lithium composite metal oxide is a lithium-manganese-based oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt-based oxide (e.g., LiCoO2, etc.), a lithium-nickel-based oxide (e.g., LiNiO2, etc.), or a lithium-nickel-manganese-based oxide (e.g., LiNi 1-Y MnY O2(here, 0 <Y<1), LiMn 2-Z Ni Z O4 (where 0 < Z < 2), etc.), lithium-nickel-cobalt oxides (e.g., LiNi 1-Y1 Co Y1 O2(here, 0 <Y1<1) 등), 리튬-망간-코발트계 산화물(예를 들면, LiCo 1-Y2 Mn Y2 O2(here, 0 <Y2<1), LiMn 2-Z1 Co Z1 O4 (where 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt oxides (e.g., Li(Ni p Co q Mn r1 )O2(where, 0<p<1, 0<q<1, 0<r1<1, p+q+r1=1) or Li(Ni p1 Co q1 Mn r2 )O4 (where 0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2), etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r3 M S2 Examples include )O2 (wherein M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r3, and s2 are each atomic fractions of independent elements, such that 0 < p2 < 1, 0 < q2 < 1, 0 < r3 < 1, 0 < s2 < 1, p2 + q2 + r3 + s2 = 1), etc.), and any one or more of these compounds may be included. Among these, the lithium composite metal oxides are LiCoO2, LiMnO2, LiNiO2, and lithium nickel manganese cobalt oxide (for example, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2)O2, or Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), or lithium nickel-cobalt-aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 It may be )O2, etc., and considering the significant improvement effect resulting from controlling the type and content ratio of constituent elements forming the lithium composite metal oxide, the lithium composite metal oxide is Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2 or Li(Ni 0.8 Mn 0.1 Co 0.1 It may be O2, etc., and any one of these or a mixture of two or more may be used.
[0119] The above positive active material may be included in the above positive active material layer in an amount of 80% to 99% by weight.
[0120] The above positive active material layer may further include at least one type selected from the group consisting of a binder and a conductive material together with the above positive active material.
[0121] The above binder is a component that assists in the bonding of the active material and the conductive material, and in the bonding to the current collector, and is typically added in an amount of 1 to 30 weight percent based on the total weight of the anode composite. Examples of such binders may include at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene ter polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, and fluororubber.
[0122] The above binder may be included in the above positive active material layer in an amount of 1% to 30% by weight.
[0123] The above conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fibers or metal fibers; metal powders such as carbon fluoride, aluminum, or 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 may be used.
[0124] The above conductive material may be added to the above positive active material layer in an amount of 1% to 30% by weight.
[0125] The above separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. It can be used without special limitations as long as it is a separator typically used in lithium secondary batteries, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte wettability. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and it may optionally be used in a single-layer or multi-layer structure.
[0126] In addition, the electrolytes used in the present invention may include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which are usable when manufacturing lithium secondary batteries, but are not limited to these.
[0127] Specifically, the electrolyte may include an organic solvent and a lithium salt.
[0128] The above organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, gamma-butyrolactone, ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; aromatic hydrocarbon elemental solvents such as benzene and fluorobenzene; carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; and nitriles such as R-CN (where R is a hydrocarbon elemental group with a straight, branched, or ring structure having C2 to C20, and may include a double aromatic ring or ether bond). Amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, carbonate-based solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant to improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred. In this case, using a mixture of the cyclic carbonate and the chain carbonate in a volume ratio of about 1:1 to about 1:9 can result in excellent electrolyte performance.
[0129] The above lithium salt can be used without special restrictions as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO2, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. It is preferable to use the lithium salt within the range of 0.1M to 2.0M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and allow lithium ions to move effectively.
[0130] As described above, the lithium secondary battery according to the present invention stably exhibits excellent discharge capacity, rapid charging characteristics, and capacity retention rate, making it useful in fields such as portable devices like mobile phones, laptop computers, and digital cameras, as well as electric vehicles like hybrid electric vehicles (HEVs), and particularly suitable for use as a constituent battery of a medium-to-large battery module. Accordingly, the present invention also provides a medium-to-large battery module comprising such a lithium secondary battery as a unit battery.
[0131] These medium-to-large battery modules can be advantageously applied to power sources requiring high output and large capacity, such as electric vehicles, hybrid electric vehicles, and power storage devices.
[0132]
[0133] The present invention will be explained in more detail below through specific embodiments.
[0134] <Examples and Comparative Examples: Preparation of Cathodes>
[0135] Comparative Example 1.
[0136] (1) Preparation of cathode active material
[0137] A carbon precursor in the form of primary particles was prepared by crushing coke raw materials, classifying them by airflow, and mechanically milling. The carbon precursor and pitch were mixed and introduced into an assembly facility containing blades, and then mechanically milled at 600°C simultaneously with mixing to prepare an intermediate in the form of secondary particles. Artificial graphite particles in the form of secondary particles were prepared by graphitizing the intermediate by heat-treating it in a graphitization furnace at 3,000°C for 2 hours, and these were used as a negative electrode active material.
[0138]
[0139] (2) Preparation of the cathode
[0140] A cathode slurry was prepared by adding the above-mentioned cathode active material, acetylene black as a conductive material, styrene-butadiene rubber as a binder, and CMC as a thickener to water as a solvent in a weight ratio of 95.6:1.0:1.1:2.3. The above cathode slurry was loaded onto a copper current collector with a loading amount of 3.6 mAh / cm² 2 The cathode was manufactured by coating it to the extent that it was dried at 130°C and rolling it.
[0141]
[0142] Comparative Example 2.
[0143] (1) Preparation of cathode active material
[0144] A negative electrode active material was prepared by mixing pitch with artificial graphite particles prepared by the same method as Comparative Example 1 above, and then heat-treating at 1,200°C to form an amorphous carbon coating layer on the surface of the artificial graphite particles. At this time, the content of the amorphous carbon coating layer was 3% by weight based on the total weight of the negative electrode active material.
[0145]
[0146] (2) Preparation of the cathode
[0147] A cathode was manufactured in the same manner as Comparative Example 1, except that the cathode active material manufactured in this way was used.
[0148]
[0149] Comparative Example 3.
[0150] (1) Preparation of cathode active material
[0151] After mixing pitch with artificial graphite particles prepared by the same method as Comparative Example 1 above, an amorphous carbon coating layer was formed on the surface of the artificial graphite particles by heat treatment at 1,200°C. A negative electrode active material was prepared by pin milling the artificial graphite particles with the amorphous carbon coating layer formed thereon at room temperature at a speed of 40 Hz for 60 minutes.
[0152]
[0153] (2) Preparation of the cathode
[0154] A cathode was manufactured in the same manner as Comparative Example 1, except that the cathode active material manufactured in this way was used.
[0155]
[0156] Comparative Example 4.
[0157] (1) Preparation of cathode active material
[0158] After mixing pitch with artificial graphite particles prepared by the same method as Comparative Example 1 above, an amorphous carbon coating layer was formed on the surface of the artificial graphite particles by heat treatment at 1,200°C. A negative electrode active material was prepared by pin milling the artificial graphite particles with the amorphous carbon coating layer formed thereon at a speed of 30 Hz for 60 minutes in a nitrogen atmosphere at room temperature.
[0159]
[0160] (2) Preparation of the cathode
[0161] A cathode was manufactured in the same manner as Comparative Example 1, except that the cathode active material manufactured in this way was used.
[0162]
[0163] Comparative Example 5.
[0164] (1) Preparation of cathode active material
[0165] After mixing pitch with artificial graphite particles prepared by the same method as Comparative Example 1 above, an amorphous carbon coating layer was formed on the surface of the artificial graphite particles by heat treatment at 1,200°C. A negative electrode active material was prepared by pin milling the artificial graphite particles with the amorphous carbon coating layer formed thereon at a speed of 40 Hz for 60 minutes in an oxygen atmosphere at room temperature.
[0166]
[0167] (2) Preparation of the cathode
[0168] A cathode was manufactured in the same manner as Comparative Example 1, except that the cathode active material manufactured in this way was used.
[0169]
[0170] Comparative Example 6.
[0171] (1) Preparation of cathode active material
[0172] After mixing pitch with artificial graphite particles prepared by the same method as Comparative Example 1 above, an amorphous carbon coating layer was formed on the surface of the artificial graphite particles by heat treatment at 1,200°C. A negative electrode active material was prepared by pin milling the artificial graphite particles with the amorphous carbon coating layer formed thereon at a speed of 20 Hz for 60 minutes in a nitrogen atmosphere at room temperature.
[0173]
[0174] (2) Preparation of the cathode
[0175] A cathode was manufactured in the same manner as Comparative Example 1, except that the cathode active material manufactured in this way was used.
[0176]
[0177] Example 1.
[0178] (1) Preparation of cathode active material
[0179] A negative electrode active material was prepared in the same manner as Comparative Example 3 above, except that the milling speed was changed to 10 Hz.
[0180]
[0181] (2) Preparation of the cathode
[0182] A cathode was manufactured in the same manner as Comparative Example 1, except that the cathode active material manufactured in this way was used.
[0183]
[0184] Example 2.
[0185] (1) Preparation of cathode active material
[0186] A negative electrode active material was prepared in the same manner as Comparative Example 3 above, except that the milling speed was changed to 20 Hz.
[0187]
[0188] (2) Preparation of the cathode
[0189] A cathode was manufactured in the same manner as Comparative Example 1, except that the cathode active material manufactured in this way was used.
[0190]
[0191] <Experimental Example: Evaluation of Physical Properties and Performance>
[0192] Experimental Example 1. Measurement of physical properties of the cathode active material
[0193] (1) Analysis of N, O, and H content
[0194] 0.1 g of each cathode active material powder prepared in the above examples and comparative examples was placed in a crucible and fed into an ONH analyzer (LECO Korea’s NOH836 Analyzer) to measure the content of nitrogen, oxygen, and hydrogen elements. At this time, three samples were prepared for each example and comparative example, and the measurement test was performed three times, and the average values were listed in Table 1 below.
[0195]
[0196] (2) BET specific surface area
[0197] 3g of each cathode active material powder prepared in the above examples and comparative examples was placed in BELSORP-MAX (MicrotracBEL corp.) and a nitrogen adsorption isotherm was obtained under a 77K liquid nitrogen atmosphere, and the BET specific surface area was calculated using this and listed in Table 1 below.
[0198]
[0199] (3) Tap density
[0200] The tap density of the negative electrode active material was measured using a GEOPYC 1360 tap density meter from Micromeritics. Specifically, 10g of the negative electrode active material powder prepared in the above examples and comparative examples was taken and filled into a container with a diameter of 19mm, and then the tap density was measured by vibrating until a horizontal force of 108N was applied, and the results are listed in Table 1 below.
[0201]
[0202] (4) Raman spectrum
[0203] For each cathode active material prepared in the above examples and comparative examples, a Raman spectrum was obtained by irradiating the sample with an Ar-ion laser of 514.5 nm wavelength using a Raman spectroscopic analysis instrument (NRS-2000B, Jasco), and the D / G ratio and the full width at half maximum of the G band were confirmed and listed in Table 1 below.
[0204]
[0205] (5) D 50
[0206] After dispersing 0.1 g of each cathode active material powder prepared in the above examples and comparative examples in a dispersion medium, the powder was introduced into a laser diffraction particle size measuring device (Malvern, Mastersizer 3000) and irradiated with ultrasound of approximately 28 kHz at an output of 60 W to measure the D of each cathode active material 50 ...was measured. The measurement results are shown in Table 1 below.
[0207]
[0208] Experimental Example 2. Measurement of the cathode orientation index
[0209] Each cathode prepared in the above examples and comparative examples was cut to the size of a sample holder to create a specimen, which was then securely attached to a glass plate using double-sided tape so as not to lift. Afterward, the specimen was fixed in a PMMA holder within an XRD measuring instrument (Bruker D8 Endeavor) using modeling clay, and X-ray diffraction analysis was performed using a Bruker D8 Endeavor (light source: Cu Kα, λ=1.54Å) equipped with a LynxEye XE-T position sensitive detector, under conditions of a step size of 0.016° and a total scan time of approximately 16 minutes for the FDS 0.5°, 2θ=53°~56° region ((004) plane) and 2θ=76°~79° region ((110) plane). The measured data was fitted to a single peak using an analytical function to measure the (110) plane peak area A(004) and the (004) plane peak area A(110). Based on this, the orientation index (OI) according to the above Equation 1 was measured and listed in Table 1 below.
[0210] Content of each element (mg per 1kg of cathode active material) BET specific surface area (m² 2 / g)Tap density (g / cc)D / G ratio Half-width (G band, cm) -1 )D 50 (㎛)OINOH Comparative Example 1 Not detected 55028011.120.2319.81524 Comparative Example 2 Not detected 6103000.60.950.6224.2188 Comparative Example 3 1809105201.91.080.7634.11522 Comparative Example 4 1906703501.21.060.6828.01620 Comparative Example 5 1001,1304102.01.080.7232.71520 Comparative Example 6 1405903200.81.040.6323.11713 Example 1 606403200.81.010.64251710 Example 2807003700.91.050.6525.61713
[0211]
[0212] Experimental Example 3. Evaluation of Slurry Processability
[0213] Using the cathode active materials of Examples 1 and 2 and Comparative Example 2 prepared above, a slurry was prepared with a weight ratio of 95.6 : 1 : 1.1 : 2.3 for the cathode active material, carbon black conductive material, CMC, and SBR, and the solid content during the kneading step was measured and the results are listed in Table 2 below. Kneading is the step in the mixing and dispersion process for preparing the electrode slurry where the greatest torque is applied; it is a step in which particles are dispersed by shear force and the surface of each particle is stabilized. At this time, it is important to appropriately set the solid content in the slurry.
[0214] Specifically, in this experiment, the solid content was measured at the point where the torque applied during the kneading stage was 30% to 50% of the maximum torque value.
[0215] Comparative Example 2 Example 1 Example 2 Solid content (%) at the kneading step 606264
[0216] Through the results of Table 2 above, it can be confirmed that Examples 1 and 2 can contain more solids compared to Comparative Example 2. The solid content in the finally prepared cathode slurry is also proportional to the solid content during the kneading step. That is, since the slurries of Examples 1 and 2 can contain more solids, it can be confirmed that a cathode with the same loading amount as Comparative Example 2 can be provided with a smaller amount. Using a smaller amount of slurry can also shorten the drying period, which can contribute to improving processability.
[0217] Through these results, it can be seen that the cathode active material of Comparative Example 2, which has a nitrogen content of less than 30 mg, had a low tap density because the aggregation between particles caused by the carbon coating was not properly resolved by milling, and consequently, the slurry viscosity was high, resulting in a decrease in solid content.
[0218]
[0219] Experimental Example 4. Cell Performance Evaluation
[0220] (1) Manufacturing of batteries
[0221] As a counter electrode for the cathode of Example 1 above, lithium metal was prepared.
[0222] An electrode assembly was manufactured by interposing a porous polyethylene separator between the above-mentioned cathode and the above-mentioned lithium metal counter electrode, and the electrode assembly was placed inside a battery case, and then a non-aqueous electrolyte was injected into the case and sealed to manufacture the coin half cell of Example 1.
[0223] As the above-mentioned non-aqueous electrolyte, LiPF6 was dissolved at a concentration of 1.0 M in an organic solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 20:80.
[0224] Coin half cells of Example 2 and Comparative Examples 1, 3 to 5 were prepared in the same manner as Example 1, except that the cathodes of Example 2 and Comparative Examples 1, 3 to 5 were used instead of the cathode prepared in Example 1.
[0225]
[0226] (2) Initial efficiency evaluation
[0227] The coin half cells of Examples 1 to 2 and Comparative Examples 3 to 5 prepared above were charged at 25°C in CC / CV mode at 0.1C (0.005V, 0.005C cut-off) and discharged in CC mode at 0.1C (1.5V cut-off) to check the initial discharge capacity and initial efficiency. The results are listed in Table 3 below.
[0228] Comparative Example 3 Comparative Example 4 Comparative Example 5 Example 1 Example 2 Initial Discharge Capacity (mAh / g) 346 347 346 351 351 Initial Efficiency (%) 91.8 92.3 91.5 93.2 93.0
[0229] Table 3 shows that the cells of Examples 1 and 2 have higher initial capacity and efficiency compared to the cells of Comparative Examples 3 to 5. This result indicates that the cathode containing a cathode active material with a nitrogen content of more than 170 mg per kg of cathode active material and an orientation index of more than 20 (Comparative Example 3); the cathode containing a cathode active material with a nitrogen content of more than 170 mg even if the orientation index is 5 to 20 (Comparative Example 4); and the cathode containing a cathode active material with an oxygen content of more than 1,000 mg even if the orientation index is 5 to 20 (Comparative Example 5) are at a disadvantage in terms of rapid charging performance of the cell compared to the cathode according to one embodiment of the present invention.
[0230]
[0231] (2) Rapid charging performance evaluation
[0232] The coin half-cells of Examples 1 to 2 and Comparative Examples 1, 3 to 5 prepared above were charged at 25°C in a CC mode at 3.0°C to obtain a charging profile according to SOC, and the charging profile was first differentiated, and the inflection point appearing in dQ / dV was determined as the point at which lithium precipitation occurs. The SOC at which lithium precipitation occurs is listed in Table 4 below.
[0233] Comparative Example 1 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Example 1 Example 2 Lithium Precipitation SOC (%) 20 25 27 26 28 33 33
[0234] Table 4 shows that the cells of Examples 1 and 2 have a higher SOC at which lithium precipitation occurs during rapid charging compared to the cells of Comparative Examples 1 and 3 to 5. This result indicates that the anodes containing a negative electrode active material with a nitrogen content of less than 30 mg or more than 170 mg per kg of negative electrode active material and an orientation index exceeding 20 (Comparative Examples 1, 3); the anode containing a negative electrode active material with a nitrogen content exceeding 170 mg even if the orientation index is 5 to 20 (Comparative Example 4); and the anode containing a negative electrode active material with an oxygen content of less than 600 mg or more than 1,000 mg even if the orientation index is 5 to 20 (Comparative Examples 5, 6) are disadvantageous in terms of rapid charging performance of the cell compared to the anode according to one embodiment of the present invention.
Claims
1. A cathode comprising a cathode current collector and a cathode composite layer provided on the cathode current collector, The above cathode composite layer comprises a cathode active material comprising artificial graphite particles; and an amorphous carbon coating layer provided on the artificial graphite particles, and The above-mentioned negative electrode active material comprises 30 mg to 170 mg of nitrogen element and 600 mg to 1,000 mg of oxygen element per 1 kg of the above-mentioned negative electrode active material, and A cathode having an orientation index according to Formula 1 below of the above cathode of 5 to 20: [Equation 1] OI=A(004) / A(110) In the above Equation 1, OI is the orientation index of the cathode, and A(004) is the peak area of the (004) plane appearing in the XRD spectrum of the above cathode, and A (110) is the peak area of the (110) plane appearing in the XRD spectrum of the above cathode.
2. In Claim 1, The cathode, wherein the above cathode active material further comprises 200 mg to 600 mg of hydrogen element per 1 kg of the above cathode active material.
3. In Claim 1, A cathode having a tap density of 0.97 g / cc or higher of the above-mentioned cathode active material.
4. In Claim 1, The above artificial graphite particles are a cathode in the form of secondary particles assembled from two or more primary particles.
5. In Claim 1, The BET specific surface area of the above cathode active material is 0.7 m 2 / g to 1.6m 2 / g, cathode.
6. In Claim 1, A cathode having a D / G ratio of 0.60 or higher, which is the ratio of the D band intensity to the G band peak intensity in the Raman spectrum of the above cathode active material.
7. In Claim 1, The half-width of the G band in the Raman spectrum of the above cathode active material is 20 cm -1 up to 40cm -1 Phosphorus, cathode.
8. In Claim 1, D of the above negative electrode active material 50 A cathode having a size of 10㎛ to 20㎛.
9. In Claim 1, A cathode having an orientation index of 10 to 20.
10. A lithium secondary battery comprising a cathode according to claim 1; a positive electrode; a separator interposed between the cathode and the positive electrode; and an electrolyte.