Negative active material and rechargeable lithium battery including same

Abstract

The present invention relates to negative active material and a rechargeable lithium battery including same, the negative active material comprising: secondary particles, each of which is a spheroidized aggregate of a plurality of primary particles; tertiary natural graphite particles, each of which is an aggregate of the secondary particles; artificial graphite on the surfaces of the primary and secondary particles; and Nb2O5.

Description

Negative active material and lithium secondary battery containing the same

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

[0002] The recent rapid proliferation of battery-powered electronic devices, such as mobile phones, laptops, and electric vehicles, has led to a rapid increase in demand for compact, lightweight, and relatively high-capacity secondary batteries. In particular, lithium secondary batteries are attracting attention as power sources for portable devices due to their lightweight design and high energy density. Accordingly, active research and development is underway to improve the performance of lithium secondary batteries.

[0003] A lithium secondary battery is a battery that includes a positive electrode and a negative electrode that contain active materials capable of intercalating and deintercalating lithium ions, and an electrolyte, and produces electrical energy through oxidation and reduction reactions when lithium ions are intercalated / deintercalated from the positive electrode and the negative electrode.

[0004] One embodiment provides a negative electrode active material exhibiting improved excellent rapid charging characteristics.

[0005] Another embodiment provides a lithium secondary battery comprising the negative active material.

[0006] One embodiment provides a negative electrode active material comprising secondary particles assembled and spheroidized from a plurality of primary particles, tertiary particles of natural graphite assembled from the secondary particles, and artificial graphite positioned on the surfaces of the primary particles and the surfaces of the secondary particles, and including Nb2O5.

[0007] Another embodiment provides a lithium secondary battery comprising a negative electrode including the negative active material; a positive electrode; and an electrolyte.

[0008] The negative active material according to one embodiment may exhibit rapid charging characteristics.

[0009] Figure 1 is a schematic diagram showing the structure of a negative electrode active material according to one embodiment.

[0010] Figure 1a is a drawing showing tertiary particle natural graphite among the structures of the negative active material shown in Figure 1.

[0011] Figure 2 is a schematic diagram showing the structure of a negative active material according to another embodiment.

[0012] Figure 3 is a drawing schematically showing the structure of a conventional negative electrode active material.

[0013] Figure 3 is a drawing showing products in each process during the manufacturing process of a negative active material according to one embodiment.

[0014] Figure 4 is a schematic diagram showing a lithium secondary battery according to an embodiment.

[0015] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention. The present invention is defined solely by the scope of the claims set forth below.

[0016] Unless otherwise specified herein, when a part such as a layer, film, region, or plate is said to be “on top of” another part, this includes not only cases where it is “directly on top of” the other part, but also cases where there are other parts in between.

[0017] Unless otherwise specified herein, the singular may also include the plural. Furthermore, unless otherwise specified, "A or B" may mean "including A, including B, or including A and B."

[0018] Unless otherwise defined herein, the particle size may be the average particle size. In addition, the particle size refers to the average particle size (D50), which means the diameter of particles with a cumulative volume of 50% by volume in a particle size distribution. The average particle size (D50) can be measured by a method well known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope (TEM) photograph or a scanning electron microscope (SEM) photograph. Alternatively, the average particle size (D50) value can be obtained by measuring with a measuring device that utilizes dynamic light-scattering, performing data analysis to count the number of particles for each particle size range, and calculating from the counted number. Alternatively, the average particle size (D50) value can be obtained by measuring with a laser diffraction method. When measuring by laser diffraction, more specifically, after the particles to be measured are dispersed in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasonic waves of approximately 28 kHz at an output of 60 W, and the average particle size (D50) based on 50% of the particle size distribution in the measuring device can be calculated.

[0019] According to one embodiment, a negative active material includes secondary particles assembled and spheroidized from a plurality of primary particles, tertiary particle natural graphite assembled from the secondary particles, and artificial graphite positioned on the surfaces of the primary particles and the surfaces of the secondary particles, and includes Nb2O5. In one embodiment, Nb2O5 may be positioned on the tertiary particle natural graphite.

[0020] Fig. 1 is a schematic diagram of the structure of such a negative electrode active material. In Fig. 1, the right side is an enlarged view of the secondary particles (5) corresponding to the dotted lines. The negative electrode active material (1) according to one embodiment includes secondary particles (5) in which a plurality of primary particles (3) are assembled and formed into spherical shapes, and tertiary particle natural graphite in which the secondary particles (5) are assembled. In addition, it includes Nb2O5 (15) positioned on the tertiary particle natural graphite. In addition, it includes artificial graphite (9) positioned on the surfaces of the primary particles (3) and the secondary particles (5).

[0021] In addition, Fig. 1a more clearly shows the tertiary particle natural graphite in Fig. 1.

[0022] According to one embodiment, the negative active material may further include an amorphous carbon coating layer surrounding the tertiary particle natural graphite. When the negative active material further includes an amorphous carbon coating layer, as shown in FIG. 2, Nb2O5(15) may be positioned on the amorphous carbon coating layer (11).

[0023] Crystalline carbon used as an anode active material, especially natural graphite, has a higher capacity than artificial graphite, and can realize an ideal capacity close to the theoretical capacity. However, natural graphite is composed of large particles with a particle size of 40 ㎛ to 120 ㎛, and is generally used as an anode active material by spheroidizing them. Fig. 3 shows the structure of a typical natural graphite anode active material (20), which includes flake natural graphite (23) and an amorphous carbon coating layer (27) located on the surface of the flake natural graphite particles. Since such an anode active material has limited sites for insertion / de-insertion during charge / discharge, its charge / discharge characteristics, especially high-rate charge / discharge characteristics, are not suitable.

[0024] According to one embodiment, a negative electrode active material includes secondary particles formed by assembling and spherizing primary particles of natural graphite into small particles, and tertiary particle natural graphite formed by re-assembling the secondary particles, and artificial graphite positioned on the surfaces of the primary particles and the surfaces of the secondary particles, thereby increasing lithium ion insertion / de-insertion sites and facilitating the movement of lithium ions. In addition, the negative electrode active material according to one embodiment includes Nb2O5, which is a structurally stable material that absorbs and desorbs lithium ions like a pseudo-capacitor and does not cause volume expansion during charge and discharge, in the tertiary particles, thereby enabling rapid attachment and detachment of lithium ions during charge and discharge. The negative electrode active material according to one embodiment can exhibit improved rapid charge and discharge characteristics. In addition, in one embodiment, Nb2O5 can be positioned on the tertiary particle natural graphite.

[0025] In one embodiment, the natural graphite may be flaky natural graphite, in which case lithium intercalation may occur more actively. According to another embodiment, the flaky natural graphite may be small-grained flaky natural graphite. When the natural graphite is small-grained flaky natural graphite, the sites where lithium ions can be inserted and deintercalated within the same area further increase, and the path through which lithium ions can move becomes shorter, making it more suitable for rapid charge / discharge.

[0026] In addition, since the negative active material according to one embodiment is formed by spheroidizing and bending small primary particles, lithium can be inserted into the bent portions of the negative active material, particularly the flaky natural graphite, in addition to both ends. In this way, since the negative active material according to one embodiment has an increased number of lithium insertion sites, it can exhibit an improved charging rate, particularly an improved high-rate charging rate.

[0027] In one embodiment, the content of Nb2O5 may be 1 wt% to 15 wt%, 2 wt% to 12 wt%, or 2 wt% to 10 wt%, based on 100 wt% of the total weight of the negative active material. When the content of Nb2O5 is within the above range, the rapid charging performance can be further improved while maintaining a uniform state, thereby exhibiting excellent battery chemical properties.

[0028] In one embodiment, the Nb2O5 may have an orthorhombic structure. Nb2O5 having such an orthorhombic structure may be referred to as T-Nb2O5. Nb2O5 having an orthorhombic structure may have a lattice spacing of the (001) plane of 0.390 nm to 0.399 nm.

[0029] Nb2O5 with an orthorhombic structure may be more suitable than Nb2O5 with a pseudohexagonal or monoclinic structure. When Nb2O5 with an orthorhombic structure is used, it can provide a path through which lithium ions can move more quickly, thereby reducing volume expansion during charge and discharge and improving rate characteristics.

[0030] According to an embodiment of the present invention, when analyzing the X-ray diffraction peaks of the negative active material having such a configuration (JCPDS card no. 30-0873), it may have peaks appearing at 2θ=22.7° ±0.2°, 28.5° ±0.2°, 36.7° ±0.2°, 46.2° ±0.2°, 50.9° ±0.2°, and 55.1° ±0.2°. 2θ=22.7° ±0.2°, 28.5° ±0.2°, 36.7° ±0.2°, 46.2° ±0.2°, 50.9° ±0.2°, and 55.1° ±0.2° represent the (001) plane, the (180) plane, the (181) plane, the (002) plane, the (380) plane, and the (381) plane, respectively. The above X-ray diffraction peak analysis can be performed using CuKα rays.

[0031] The primary particles may have a particle size of 4 μm to 8 μm. The particle size of the primary particles may be, for example, 5 μm to 8 μm, 6 μm to 8 μm, or 6 μm to 7 μm.

[0032] The secondary particles may have a particle size of 5 μm to 10 μm. The particle size of the secondary particles may be, for example, 6 μm to 10 μm, 6 μm to 8 μm, or 7 μm to 8 μm.

[0033] The above tertiary particles may have a particle size of 9 μm to 15 μm. For example, they may be 9.2 μm to 15 μm or 9.5 μm to 15 μm.

[0034] When the particle size of the primary particles is 4 µm to 8 µm, manufacturing is easier, cycle life characteristics can be further improved, and application to lithium secondary batteries can be easier. In addition, when the particle size of the secondary particles is 5 µm to 10 µm, tertiary particles can be manufactured better, and application to lithium secondary batteries can be easier. In addition, when the particle size of the tertiary particles is 9 µm to 15 µm, better initial efficiency can be exhibited, and excellent negative electrode charge / discharge characteristics can be exhibited, making application to lithium secondary batteries more appropriate.

[0035] In the negative active material according to one embodiment, the thickness of the amorphous carbon coating layer may be 5 nm to 50 nm, for example, 10 nm to 50 nm or 20 nm to 50 nm. When the thickness of the amorphous carbon coating layer falls within the above range, side reactions with the electrolyte can be more effectively suppressed, and charge / discharge rate characteristics can be improved.

[0036] The particle size of the negative electrode active material having primary particles, secondary particles, and tertiary particles having such particle sizes and an amorphous carbon coating layer having the above thickness may be 9.05 μm to 16 μm. The particle size of the negative electrode active material may be, for example, 9.05 μm to 16 μm, 9.2 μm to 15.5 μm, or 9.5 μm to 15 μm. When the particle size of the negative electrode active material is within the above range, the insertion of lithium ions is facilitated, so that the charge rate characteristics can be improved, and excellent cycle life characteristics can be exhibited due to the improvement in initial efficiency and negative electrode processability.

[0037] In one embodiment, the secondary particles are formed by assembling primary particles, and the number of primary particles is not particularly limited as long as it can form secondary particles. For example, 2 to 30, 2 to 20, 2 to 10, or 2 to 4 primary particles may be assembled to form secondary particles. In addition, the tertiary particles are formed by assembling secondary particles, and the number of secondary particles is also not particularly limited as long as it can form tertiary particles. For example, 2 to 20, 2 to 10, or 2 to 4 secondary particles may be assembled to form tertiary particles.

[0038] In one embodiment, the content of the artificial graphite may be 6 wt% to 16.5 wt%, 6 wt% to 15 wt%, or 10 wt% to 14.5 wt%, based on 100 wt% of the total weight of the negative active material. In one embodiment, since the artificial graphite is located on the surface of the primary particles and the surface of the secondary particles, when the content of the artificial graphite is within the above range, the interior of the negative active material may be more dense. Since the negative active material according to one embodiment includes secondary particles in which primary particles are assembled and spheroidized and tertiary particles in which the secondary particles are assembled, the artificial graphite is filled in the space that can be formed between the particles, and in particular, since it is filled with the above content, the space can be more sufficiently filled, and as a result, the interior of the final negative active material may have a dense form.

[0039] In one embodiment, the content of natural graphite may be 74 wt% to 89 wt%, 80 wt% to 88.5 wt%, or 80.5 wt% to 88 wt% based on 100 wt% of the total negative active material.

[0040] In this way, the negative active material according to one embodiment can have the characteristics of high capacity, good pressing properties, and excellent pellet density due to the use of natural graphite, an improved high rate charging rate due to increased lithium insertion sites including spherical secondary particles assembled from small primary particles, and also the high charging rate characteristics of artificial graphite. In addition, an effect of improved charge / discharge rate characteristics can also be obtained due to the inclusion of an amorphous carbon coating layer.

[0041] The amorphous carbon may be any one selected from soft carbon, hard carbon, mesophase pitch carbide, calcined coke, and mixtures thereof. In one embodiment, the content of the amorphous carbon may be 1 wt% to 5 wt% based on 100 wt% of the total negative active material.

[0042] The above negative active material may have a tap density of 0.8 g / cc to 1.1 g / cc, for example, 0.9 g / cc to 1.1 g / cc. When the tap density of the negative active material falls within the above range, the internal pore volume of the negative active material and side reactions with the electrolyte are reduced, and thus the life characteristics may be improved. In one embodiment, the tap density has a conversion factor of 0.2907 cm 3 The pressure of 108 N can be applied three times using a GeoPyc 1360 Pycnometer from Micromeritics, which has a chamber with a diameter of 19.1 mm and a pressure of 108 N, and the average value can be obtained.

[0043] According to one embodiment, the negative active material may have a Hg cumulative pore volume of 0.01 mL / g to 0.07 mL / g, 0.03 mL / g to 0.07 mL / g, or 0.04 mL / g to 0.07 mL / g. When the Hg cumulative pore volume is within the above range, it means that the pores, i.e., empty spaces, are small within the negative active material. The pores measured in the above pore volume may have a particle size of 0.01 μm to 1 μm.

[0044] If the mercury accumulation pore volume falls within the above range, the amorphous carbon content within the negative electrode active material is appropriate, thereby achieving superior negative electrode active material efficiency. Furthermore, if the mercury accumulation pore volume falls within the above range, the interior of the negative electrode active material can maintain a density sufficient to allow for good electrolyte impregnation without excessive surface area reacting with the electrolyte, thereby exhibiting appropriate life characteristics without excessive side reactions.

[0045] In one embodiment, the mercury cumulative pore volume can be obtained by adding mercury to a negative active material, applying a pressure of 0.1 psi to 60,000 psi to force the mercury into the negative active material, and then measuring the change in the volume of the mercury according to the pressure change. The pressure change can be performed by controlling the pressure to increase from 0.1 psi to 0.2 psi to a pressure of 50,000 psi to 60,000 psi.

[0046] The above negative active material can be manufactured by the following method.

[0047] A grinding and particle reduction process is performed to grind natural graphite raw materials with a particle size of 80㎛ or more into primary particles. The natural graphite raw materials can be ground into primary particles by applying an airflow grinding method. The airflow grinding is performed by grinding the natural graphite raw materials at room temperature at a pressure of 5 to 20 kg / cm. 2 It can be implemented by crushing with the air current of the condition.

[0048] The above natural graphite raw material may be natural graphite in flake form.

[0049] The above-mentioned grinding and particle size reduction process can be performed so that the particle size of the primary particles is 4 µm to 8 µm, for example, 4 µm to 7 µm, 4 µm to 6 µm, or 5 µm to 7 µm.

[0050] The above primary particles are subjected to a spheroidization and assembly process using a spheroidization device to form secondary particles. The spheroidization and assembly process can be performed so that the particle size of the secondary particles becomes 5 µm to 10 µm, for example, 6 µm to 10 µm, 6 µm to 8 µm, or 7 µm to 8 µm.

[0051] Next, the secondary particles and the first amorphous carbon precursor are mixed to produce a mixed product. This process can further densify the interior of the secondary particles.

[0052] A second amorphous carbon precursor is added to the obtained mixed product and granulated to produce tertiary particles. The granulation process can be performed using conventional granulation equipment, but is not limited thereto.

[0053] The first and second amorphous carbon precursors may be the same or different, and may be any one selected from phenol resin, furan resin, epoxy resin, polyacrylonitrile, polyamide resin, polyimide resin, polyamideimide resin, synthetic pitch, petroleum pitch, coal pitch, tar, and combinations thereof.

[0054] The first and second amorphous carbon precursors are converted into crystalline carbon, i.e., artificial graphite, in a subsequent heat treatment process, and thus the mixing ratio of the secondary particles and the first and second amorphous carbon precursors can be adjusted so that the content of artificial graphite in the final product is 10 wt% to 15 wt% with respect to 100 wt% of the total negative active material.

[0055] According to the above process, the first and second amorphous carbon precursors can be inserted into the secondary particles and positioned on the surface of the primary particles, and can also be positioned on the surface of the secondary particles.

[0056] The obtained tertiary particles are subjected to a first heat treatment. This first heat treatment can be performed at a high temperature suitable for graphitizing the first and second amorphous carbon precursors, for example, at 2,800°C to 3,000°C. The first heat treatment process can be performed for 1 hour to 5 hours, for example, 1 hour to 4 hours, or 1 hour to 3 hours. Through this process, the first and second amorphous carbon precursors can be converted into artificial graphite. Accordingly, the first and second amorphous carbon precursors located on the surfaces of the primary particles and the secondary particles are converted into artificial graphite, so that the artificial graphite can be located.

[0057] The obtained primary heat treatment product is added to a niobium precursor solution. The niobium precursor solution can be prepared by adding a niobium precursor to a solvent. The niobium precursor may be NbCl5, niobium oxalate, or a combination thereof, and the solvent may be ethanol, methanol, dimethylformamide, or a combination thereof. The solid content of the niobium precursor solution may be 0.01 wt% to 1 wt%, 0.01 wt% to 0.5 wt%, or 0.02 wt% to 0.2 wt%. The mixing ratio of the primary heat treatment product and the niobium precursor solution is adjusted so that the content of Nb2O5 in the final negative electrode active material is 1 wt% to 15 wt%.

[0058] The obtained mixture is stirred. This stirring process can be performed at a temperature range of 100°C to 150°C, 110°C to 140°C, or 110°C to 130°C for 10 to 20 hours, or 10 to 15 hours.

[0059] Next, the stirred product is heat-treated to produce a negative electrode active material. In this heat-treatment process, the niobium precursor is converted to Nb2O5 and located on the surface of the tertiary particle. The heat-treatment process can be performed at 500°C to 1200°C, 600°C to 1000°C, or 700°C to 900°C for 1 hour to 10 hours, 1 hour to 8 hours, or 1 hour to 6 hours.

[0060] After the above stirring and heat treatment, a further cleaning process can be performed. This cleaning process can be performed using alcohol such as methanol, ethanol, or propanol.

[0061] Before adding the obtained first heat-treated product to the niobium precursor solution, a process of coating the obtained first heat-treated product with a third amorphous carbon precursor may be further performed. The third amorphous carbon precursor may be a phenol resin, a furan resin, an epoxy resin, a polyacrylonitrile, a polyamide resin, a polyimide resin, a polyamideimide resin, a synthetic pitch, a petroleum pitch, a coal pitch, tar, or a combination thereof. The third amorphous carbon precursor and the first and / or second amorphous carbon precursors may be the same or different.

[0062] In the above coating process, the amount of the third amorphous carbon precursor used can be appropriately adjusted so that the thickness of the amorphous carbon coating layer in the final product, the negative active material, is 5 nm to 50 nm, and there is no need for special limitation.

[0063] The above-mentioned coating product is subjected to a second heat treatment. The second heat treatment process can be carried out at 800°C to 2,000°C, for example, 800°C to 1,800°C, 800°C to 1,600°C, 800°C to 1,400°C, or 1,200°C to 1,300°C. The second heat treatment process can be carried out for 1 hour to 5 hours, 1 hour to 4 hours, or 1 hour to 3 hours.

[0064] Another embodiment provides a lithium secondary battery comprising a cathode, a cathode, and a non-aqueous electrolyte.

[0065] The above negative electrode includes a negative electrode active material layer including a negative electrode active material, a binder and optionally a conductive material according to one embodiment, and a current collector supporting the negative electrode active material layer.

[0066] In the above negative electrode active material layer, the content of the negative electrode active material may be 95 wt% to 99 wt% with respect to 100 wt% of the entire negative electrode active material layer.

[0067] The content of the above binder may be 1 wt% to 5 wt% with respect to 100 wt% of the entire binder negative electrode active material layer.

[0068] When the negative electrode active material layer further includes a conductive material, the content of the negative electrode active material may be 90 wt% to 99 wt% with respect to 100 wt% of the entire negative electrode active material layer, and the contents of the binder and the conductive material may each be 1 wt% to 5 wt% with respect to 100 wt% of the entire negative electrode active material layer.

[0069] The above binder serves to adhere the negative active material particles well to each other and also to adhere the negative active material well to the current collector. The binder may be a non-aqueous binder, an aqueous binder, or a combination thereof.

[0070] The non-aqueous binder may include ethylene propylene copolymer, polyacrylonitrile, polystyrene, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0071] The above-mentioned water-based binder may be styrene-butadiene rubber (SBR), acrylated styrene-butadiene rubber (ABR), acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluoroelastomer, a polymer containing ethylene oxide, polyvinylpyrrolidone, polypropylene, polyepichlorohydrin, polyphosphazene, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, or a combination thereof.

[0072] The negative electrode binder may include a cellulose-based compound. In addition, the negative electrode binder may include both a cellulose-based compound and the aqueous binder. The cellulose-based compound may be a mixture of one or more of carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or an alkali metal salt thereof. The alkali metal may be Na, K, or Li. In addition to being a binder, the cellulose-based compound may also function as a thickener that provides viscosity. Accordingly, the cellulose-based compound may be appropriately used within the binder content, and the content thereof is not necessarily limited, but may be 0.1 to 3 parts by weight based on 100 parts by weight of the negative electrode active material.

[0073] The conductive material is used to provide conductivity to the electrode, and any material that does not cause chemical changes and is electronically conductive can be used in the battery. Examples of the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fiber; metal-based materials such as metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or conductive materials containing mixtures thereof.

[0074] The current collector may be selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0075] The above positive electrode includes a current collector and a positive electrode active material layer formed on the current collector.

[0076] As the positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound) can be used. Specifically, at least one compound oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof can be used. A more specific example is a compound represented by any one of the following chemical formulas. Li a A 1-b X b D2(0.90≤a≤1.8, 0≤b≤0.5); Li a A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a E 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a E 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Ni 1-b-c Co b X c D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α≤2); Li a Ni 1-b-c Co b X c O 2-α T α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni 1-b-c Co b X c O 2-α T2(0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni 1-b-c Mn b X c Dα (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α≤2); Li a Ni 1-b-c Mr b X c O 2-α T α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni 1-b-c Mr b X c O 2-α T2(0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni b HAVE BEEN c G d O2(0.90 ≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0.001≤d≤0.1); Li a Ni b Co c L 1 d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1); Li a Ni b Co c Al d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1); Li a Ni b Co c Mr d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0.001≤e≤0.1); Li a NiG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mr 1-b G b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li aMn2G b O4(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5); QO2; QS2; LiQS2; V2O5; LiV2O5; LiZO2; LiNiVO4; Li (3-f) J2(PO4)3(0≤f≤2); Li (3-f) Fe2(PO4)3(0≤f≤2); Li a FePO4(0.90≤a≤1.8)

[0077] In the chemical formula, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; T is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; Z is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof; L 1 is Mn, Al or a combination thereof.

[0078] This compound may have a coating layer on its surface, or a compound having the above compound and a coating layer may be mixed and used. This coating layer may include at least one coating element compound selected from the group consisting of an oxide of the coating element, a hydroxide of the coating element, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, and a hydroxycarbonate of the coating element. The compounds forming these coating layers may be amorphous or crystalline. The coating elements included in the coating layer may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The coating layer forming process may use any coating method as long as it can coat the compound with these elements by a method that does not adversely affect the physical properties of the positive electrode active material (for example, spray coating, dipping, etc.), and since this is well understood by those working in the relevant field, a detailed description thereof will be omitted.

[0079] In the above positive electrode, the content of the positive electrode active material may be 90 wt% to 98 wt% with respect to the total weight of the positive electrode active material layer.

[0080] In one embodiment, the positive electrode active material layer may further include a binder and a conductive material. In this case, the content of the binder and the conductive material may be 1 wt% to 5 wt%, respectively, based on the total weight of the positive electrode active material layer.

[0081] The above binder serves to adhere the positive electrode active material particles well to each other and also to adhere the positive electrode active material well to the current collector. Representative examples of the binder include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0082] The conductive material is used to provide conductivity to the electrode, and any material that does not cause chemical changes and is electronically conductive can be used in the battery. Examples of the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fiber; metal-based materials such as metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or conductive materials containing mixtures thereof.

[0083] Al may be used as the above current collector, but is not limited thereto.

[0084] The above electrolyte comprises a non-aqueous organic solvent and a lithium salt.

[0085] The above non-aqueous organic solvent acts as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0086] As the above non-aqueous organic solvent, a carbonate-based, ester-based, ether-based, ketone-based, alcohol-based, or aprotic solvent can be used.

[0087] Examples of the carbonate solvent that can be used include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. Examples of the ester solvent that can be used include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methylpropionate, ethylpropionate, decanolide, mevalonolactone, caprolactone, etc. Examples of the ether solvent that can be used include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, etc. In addition, cyclohexanone and the like can be used as the ketone solvent. In addition, ethyl alcohol, isopropyl alcohol and the like can be used as the alcohol solvent. As the aprotic solvent, nitriles such as R-CN (R is a hydrocarbon group having a linear, branched, or cyclic structure with 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, and the like can be used.

[0088] The above organic solvents can be used alone or in combination of one or more, and when using one or more in combination, the mixing ratio can be appropriately adjusted depending on the desired battery performance, which is widely understood by those working in the relevant field.

[0089] Additionally, in the case of the above carbonate solvent, it is recommended to use a mixture of cyclic carbonate and chain carbonate. In this case, the performance of the electrolyte may be excellent when the cyclic carbonate and chain carbonate are mixed and used in a volume ratio of 1:1 to 1:9.

[0090] The above organic solvent may further include an aromatic hydrocarbon-based organic solvent in addition to the above carbonate-based solvent. In this case, the carbonate-based solvent and the aromatic hydrocarbon-based organic solvent may be mixed in a volume ratio of 1:1 to 30:1.

[0091] As the above aromatic hydrocarbon organic solvent, an aromatic hydrocarbon compound of the following chemical formula 1 can be used.

[0092] [Chemical Formula 1]

[0093]

[0094] (In the above chemical formula 1, R1 to R6 are the same or different and are selected from the group consisting of hydrogen, halogen, an alkyl group having 1 to 10 carbon atoms, a haloalkyl group, and combinations thereof.)

[0095] Specific examples of the above aromatic hydrocarbon organic solvents include benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, iodobenzene, 1,2-diiodobenzene, 1,3-diiodobenzene, 1,4-diiodobenzene, 1,2,3-triiodobenzene, 1,2,4-triiodobenzene, toluene, fluorotoluene, 2,3-difluorotoluene, 2,4-difluorotoluene, 2,5-difluorotoluene, 2,3,4-trifluorotoluene, 2,3,5-trifluorotoluene, chlorotoluene, 2,3-dichlorotoluene, 2,4-dichlorotoluene, 2,5-dichlorotoluene, 2,3,4-trichlorotoluene, 2,3,5-trichlorotoluene, iodotoluene, 2,3-diiodotoluene, 2,4-diiodotoluene, 2,5-diiodotoluene, 2,3,4-triiodotoluene, 2,3,5-triiodotoluene, xylene, and combinations thereof.

[0096] The above electrolyte may further include vinylethyl carbonate, vinylene carbonate or an ethylene carbonate compound of the following chemical formula 2 as a life-promoting additive to improve battery life.

[0097] [Chemical Formula 2]

[0098]

[0099] (In the above chemical formula 2, R7 and R8 are the same or different from each other and are selected from the group consisting of hydrogen, a halogen group, a cyano group (CN), a nitro group (NO2) and a fluorinated alkyl group having 1 to 5 carbon atoms, and at least one of R7 and R8 is selected from the group consisting of a halogen group, a cyano group (CN), a nitro group (NO2) and a fluorinated alkyl group having 1 to 5 carbon atoms, provided that both R7 and R8 are not hydrogen.)

[0100] Representative examples of the above ethylene carbonate compounds include difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, and fluoroethylene carbonate. When such life-prolonging additives are further used, the amount used can be appropriately adjusted.

[0101] The above lithium salt is a substance that is dissolved in an organic solvent and acts as a source of lithium ions in the battery, enabling the basic operation of a lithium secondary battery and promoting the movement of lithium ions between the positive and negative electrodes. Representative examples of such lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiN(SO2C2F5)2, Li(CF3SO2)2N, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide: LiFSI), LiC4F9SO3, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (wherein, x and y are natural numbers, for example, integers from 1 to 20), lithium difluoro(bisoxolato) phosphate, LiCl, LiI, LiB(C2O4)2 (lithium bis(oxalato) borate: LiBOB) and lithium difluoro(oxalato)borate (LiDFOB) are included as a supporting electrolyte salt. It is preferable to use the concentration of the lithium salt within the range of 0.1 M to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0102] Depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators may include polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films comprising two or more layers thereof. Furthermore, mixed multilayer films such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may also be used.

[0103] Fig. 4 illustrates an exploded perspective view of a lithium secondary battery according to one embodiment of the present invention. While the lithium secondary battery according to one embodiment is described as having a square shape, the present invention is not limited thereto and can be applied to various types of batteries, such as cylindrical and pouch-shaped.

[0104] Referring to FIG. 4, a lithium secondary battery (100) according to one embodiment may include an electrode assembly (40) wound with a separator (30) interposed between a positive electrode (10) and a negative electrode (20), and a case (50) in which the electrode assembly (40) is housed. The positive electrode (10), the negative electrode (20), and the separator (30) may be impregnated with an electrolyte (not shown).

[0105] Hereinafter, examples and comparative examples of the present invention will be described. However, the following examples are merely examples of the present invention, and the present invention is not limited to the following examples.

[0106] (Example 1)

[0107] Small primary particles were produced by air-pulverizing natural graphite raw materials having particle diameters of 80 μm to 120 μm. The small primary particles were spheroidized and granulated using spheroidizing equipment to produce secondary particles. The secondary particles were mixed with pitch carbon (a first amorphous carbon precursor) to produce a mixed product.

[0108] Next, pitch carbon (second amorphous carbon precursor) was added to the above mixed product and granulated to produce tertiary particles.

[0109] The manufactured tertiary particles were first heat-treated at 2,800°C for 2 hours. During this heat treatment process, all of the pitch carbons were graphitized and existed as artificial graphite on the surfaces of the primary and secondary particles.

[0110] NbCl5 solution (solvent: ethanol, solid content: 0.02 wt%) was added to the obtained primary heat treatment product, and stirred at 120°C for 20 hours.

[0111] The stirred product was washed several times with ethanol and dried.

[0112] Next, the dried product was heat-treated at 800°C for 3 hours and washed with ethanol to produce a negative electrode active material.

[0113] The manufactured negative active material includes secondary particles assembled and spheroidized from primary particles, tertiary particles of natural graphite assembled from these secondary particles, artificial graphite located on the surfaces of the primary particles and the surfaces of the secondary particles, and Nb2O5 is included in the tertiary particles.

[0114] In the above manufacturing process, the amount of the secondary particles and the pitch carbons used was adjusted so that the content of the natural graphite in the manufactured negative electrode active material was 88 wt% and the content of the artificial graphite was 10 wt% with respect to the total 100 wt% of the final negative electrode active material. In addition, the amount of the NbCl5 solution used was adjusted so that the content of the Nb2O5 in the final negative electrode active material was 2 wt%.

[0115] The average particle diameter (D50) of the manufactured primary particles, the average particle diameter (D50) of the secondary particles, the average particle diameter (D50) of the tertiary particles, the average particle diameter (D50) of the negative electrode active material, and the tap density are shown in Table 1 below.

[0116] A slurry of the negative active material was prepared by mixing 97.5 wt% of the above negative active material, 1.5 wt% of styrene butadiene rubber binder, and 1 wt% of carboxymethyl cellulose thickener in a water solvent.

[0117] A negative electrode including a current collector and a negative electrode active material layer formed on the current collector was manufactured by a conventional method of coating, drying, and rolling the above negative electrode active material slurry on a Cu foil current collector.

[0118] A coin-type half-cell was manufactured using the above-mentioned cathode, lithium metal counter electrode, and electrolyte. The electrolyte used was ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (volume ratio 20:10:70) containing 1.5 M LiPF6 dissolved therein.

[0119] (Example 2)

[0120] Except that the amounts of the secondary particles and the pitch carbons were adjusted so that the content of the natural graphite in the manufactured negative active material was 81 wt% and the content of the artificial graphite was 9 wt% with respect to 100 wt% of the total negative active material, and the amount of the NbCl5 solution was adjusted so that the content of the Nb2O5 in the final negative active material was 10 wt%, the negative active material was manufactured in the same manner as in Example 1. Using the negative active material, a negative electrode and a half-battery were manufactured in the same manner as in Example 1.

[0121] (Example 3)

[0122] Except that the amounts of the secondary particles and the pitch carbons were adjusted so that the content of the natural graphite was 85.5 wt% and the content of the artificial graphite was 9.5 wt% with respect to 100 wt% of the total weight of the negative electrode active material, and the amount of the NbCl5 solution was adjusted so that the content of the Nb2O5 in the final negative electrode active material was 5 wt%, the negative electrode active material was manufactured in the same manner as in Example 1. Using the negative electrode active material, a negative electrode and a half-battery were manufactured in the same manner as in Example 1.

[0123] (Example 4)

[0124] The first heat-treated product obtained through the first heat treatment in Example 1 was additionally coated with pitch carbon, and then subjected to a second heat treatment at 1,200°C for 2 hours.

[0125] NbCl5 solution (solvent: ethanol, solid content: 0.02 wt%) was added to the secondary heat treatment product and stirred at 120°C for 20 hours.

[0126] The stirred product was washed several times with ethanol and dried.

[0127] Next, the dried product was heat-treated at 800°C for 3 hours and washed with ethanol to produce a negative electrode active material.

[0128] The manufactured negative active material includes secondary particles assembled and spheroidized from primary particles, tertiary particle natural graphite assembled from these secondary particles, artificial graphite positioned on the surfaces of the primary particles and the surfaces of the secondary particles, and an amorphous carbon coating layer (soft carbon coating layer) surrounding the surfaces of the tertiary particles and Nb2O5.

[0129] In the above manufacturing process, the amounts of the secondary particles and the pitch carbons used were adjusted so that, in the manufactured negative electrode active material, the content of the natural graphite was 85 wt%, the content of the artificial graphite was 10 wt%, and the content of the amorphous carbon coating layer was 3 wt% with respect to the total 100 wt% of the negative electrode active material. In addition, the amount of the NbCl5 solution used was adjusted so that the content of Nb2O5 was 2 wt% in the final negative electrode active material.

[0130] The average particle diameter (D50) of the manufactured primary particles, the average particle diameter (D50) of the secondary particles, the average particle diameter (D50) of the tertiary particles, the average particle diameter (D50) of the negative electrode active material, and the tap density are shown in Table 1 below.

[0131] Using the above negative active material, a negative electrode and a half-cell were manufactured in the same manner as in Example 1.

[0132] (Example 5)

[0133] Except that the amounts of the secondary particles and the pitch carbons were adjusted so that the content of the natural graphite was 78 wt% and the content of the artificial graphite was 9 wt% with respect to 100 wt% of the total weight of the negative electrode active material, and the amount of the NbCl5 solution was adjusted so that the content of the Nb2O5 in the final negative electrode active material was 10 wt%, the negative electrode active material was manufactured in the same manner as in Example 2. Using the negative electrode active material, the negative electrode and half-cell were manufactured in the same manner as in Example 1.

[0134] (Comparative Example 1)

[0135] A flake-shaped natural graphite raw material with a particle size of 11 ㎛ and a NbCl5 solution (solvent: ethanol, solid content: 0.02 wt%) were added and stirred at 120°C for 20 hours.

[0136] The stirred product was washed several times with ethanol and dried.

[0137] Next, the dried product was heat-treated at 800°C for 3 hours and washed with ethanol to produce a negative electrode active material.

[0138]

[0139] *The manufactured negative electrode active material included a natural graphite core and Nb2O5 positioned on the surface of the graphite core. The amount of NbCl5 solution used was adjusted so that the Nb2O5 content in the final negative electrode active material was 2 wt%.

[0140] Since the negative active material of Comparative Example 1 above is not in the form of secondary particles assembled from primary particles, only the average particle diameter of the negative active material is shown in Table 1 below.

[0141] Average particle diameter of primary particles (D50, ㎛)Average particle diameter of secondary particles (D50, ㎛)Average particle diameter of tertiary particles (D50, ㎛)Average particle diameter of negative electrode active material (D50, ㎛)Example 156.510.510.5Example 256.510.511Example 356.510.510.7Example 456.510.510.6Example 556.510.511.2Comparative example 1---11

[0142] Natural graphite content (weight%) Artificial graphite content (weight%) Amorphous carbon coating layer content (weight%) Nb2O5 content (weight%) Example 18810-2 Example 2819-10 Example 385.59.5-5 Example 4851032 Example 5789310 Comparative example 193-52

[0143] Experimental Example 1) Evaluation of X-ray diffraction analysis

[0144] X-ray diffraction analysis using CuKα rays was performed on the negative electrode active materials manufactured according to Examples 1 to 5 and Comparative Example 1.

[0145] X-ray diffraction analysis was performed using an X'Pert (PANalytical) XRD device, and the monochrometer device was removed to improve peak intensity resolution. The measurement conditions were 2θ = 20° to 80°, scan speed (° / s) = 0.06436, and step size 0.026° / step.

[0146] The results of X-ray diffraction analysis (JCPDS card no. 30-0873) are shown in Table 3 below. In Table 3, if all peaks appear at 2θ=22.7°±0.2°, 28.5°±0.2°, 36.7°±0.2°, 46.2°±0.2°, 50.9°±0.2°, and 55.1°±0.2°, they are marked as O, and if even one of them does not appear, they are marked as X. 2θ = 22.7°±0.2°, 28.5°±0.2°, 36.7°±0.2°, 46.2°±0.2°, 50.9°±0.2°, 55.1°±0.2° represent the (001) plane, (180) plane, (181) plane, (002) plane, (380) plane, and (381) plane, respectively.

[0147] Experimental Example 2) Evaluation of charging rate characteristics

[0148] The half-cells manufactured according to the above Examples 1 to 5 and Comparative Example 1 were charged and discharged once at 0.2 C and once at 2 C.

[0149] For the 0.2C charging capacity, the ratio of the 2C charging capacity was calculated, and the results are shown in Table 3 below as charging rate characteristics.

[0150] Experimental Example 3) Evaluation of Direct Current Internal Resistance (DC-IR)

[0151] The half-cells manufactured according to Examples 1 to 5 and Comparative Example 1 were charged at 25°C with a constant current / constant voltage of 0.2C, 0.01V, and 0.01C cut-off conditions, rested for 10 minutes, discharged at a constant current of 0.2C, 1.5V cut-off conditions, and rested for 10 minutes. One charge / discharge cycle was performed under the charge / discharge conditions, and the voltage drop (V) that occurred while flowing a current of 8C for 10 seconds at SOC50 (a state in which the battery is charged to 50% of its total charge capacity when the battery is 100% charged, which means a state in which the discharge is 50%) was measured. The resistance value was obtained from the measured voltage and the applied current (8C), and the result was expressed as the direct current internal resistance (DC-IR). The results are shown in Table 3 below.

[0152] Experimental Example 4) Life Characteristics Evaluation

[0153] The half-cells manufactured according to Examples 1 to 5 and Comparative Example 1 were subjected to 300 charge-discharge cycles at 1C at 25°C. The ratio of the 300-cycle discharge capacity to the 1-cycle discharge capacity was determined. The results are presented as life characteristics in Table 3 below.

[0154] XRD results Capacity (mAh / g) Charge rate (%) DC-IR (Ω) Life characteristics (%) Example 1 35 8 50% 6.39 2.1 Example 2 34 5 55% 69 1.4 Example 3 35 360% 6.19 3.4 Example 4 35 6 51% 6.29 2.5 Example 5 34 35 6% 5.99 1.8 Comparative example 1 35 6 28% 8.19 1.0

[0155] As shown in Table 3 above, Examples 1 to 5 and Comparative Example 1 all showed similar X-ray diffraction analysis results. From these results, it can be seen that all Nb2O5 included in the negative electrode active material corresponds to T-Nb2O5. In addition, the lattice spacing of the (001) plane of Nb2O5 included in the negative electrode active material was measured and found to be 0.39 nm.

[0156] As shown in Table 3 above, the batteries of Examples 1 to 5 using the negative active material in which Nb2O5 is positioned on the surface of the assembled carbon-based material, particularly the tertiary particle, exhibited high capacity, charge rate, and life characteristics, and low resistance.

[0157] On the other hand, in the case of Comparative Example 1, the charging rate was very low and the resistance was very high.

[0158] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the patent claims, the detailed description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

Claims

1. Secondary particles assembled and spheroidized from a plurality of primary particles, and tertiary particles of natural graphite assembled from these secondary particles; and Contains artificial graphite located on the surface of the primary particles and the surface of the secondary particles, Nb2O5 A negative active material comprising:

2. In paragraph 1, A negative electrode active material having a content of Nb2O5 of 1 to 15 wt% based on 100 wt% of the total negative electrode active material.

3. In paragraph 1, A negative electrode active material having a content of Nb2O5 of 5 to 10 wt% based on 100 wt% of the total negative electrode active material.

4. In paragraph 1, The above Nb2O5 is a negative electrode active material having an orthorhombic structure.

5. In paragraph 1, The above Nb2O5 is a negative electrode active material having a lattice spacing of 0.35 nm to 0.45 nm on the (001) plane.

6. In paragraph 1, A negative electrode active material having peaks appearing at 2θ = 22.7°±0.2°, 28.5°±0.2°, 36.7°±0.2°, 46.2°±0.2°, 50.9°±0.2°, and 55.1°±0.2° when analyzing X-ray diffraction peaks of the above negative electrode active material.

7. In paragraph 1, The above Nb2O5 is a negative active material located on the tertiary particle natural graphite.

8. In paragraph 1, A negative electrode active material further comprising an amorphous carbon coating layer surrounding the above-mentioned tertiary particle natural graphite.

9. In paragraph 1, The above Nb2O5 is a negative electrode active material positioned on the amorphous carbon coating layer.

10. In paragraph 1, A negative electrode active material wherein the coating layer has a thickness of 5 nm to 50 nm.

11. In paragraph 1, The above natural graphite is a negative electrode active material in the form of natural graphite flakes.

12. In paragraph 1, A negative electrode active material having a content of the artificial graphite of 6 to 16.5 wt% based on 100 wt% of the total negative electrode active material.

13. In paragraph 1, A negative electrode active material having a content of the natural graphite of 74 to 89 wt% based on 100 wt% of the total negative electrode active material.

14. In paragraph 1, A negative electrode active material wherein the above primary particles have a particle size of 4 ㎛ to 8 ㎛.

15. In paragraph 1, A negative electrode active material wherein the secondary particles have a particle size of 5 μm to 10 μm.

16. In paragraph 1, A negative electrode active material wherein the above tertiary particles have a particle size of 9 ㎛ to 15 ㎛.

17. In paragraph 1, The above negative active material has a tap density of 0.8 g / cc to 1.1 g / cc.

18. In paragraph 1, The above negative active material has a mercury cumulative pore volume of 0.01 mL / g to 0.07 mL / g.

19. In paragraph 1, The above amorphous carbon is a negative active material that is soft carbon, hard carbon, mesophase pitch carbide, calcined coke or a combination thereof.

20. A negative electrode comprising the negative active material of any one of claims 1 to 19; Bipolar; and Containing electrolytes Lithium secondary battery.

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