Negative electrode active material, negative electrode and secondary battery containing the same

Abstract

The present invention relates to a negative electrode active material comprising: artificial graphite particles; and sulfur (S) distributed within the artificial graphite particles, wherein the sulfur content of the negative electrode active material is 15 ppm to 40 ppm. A negative electrode and a secondary battery comprising the negative electrode active material can exhibit improved output and capacity characteristics, as well as improved initial efficiency.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority from Korean Patent Application No. 10-2020-0120878, filed on September 18, 2020, the disclosure of which is incorporated herein by reference. Technical Field

[0004] The present invention relates to a negative electrode active material, and a negative electrode and a secondary battery comprising the negative electrode active material. Background Art

[0005] As energy prices rise due to the depletion of fossil fuels and concerns about environmental pollution grow, eco-friendly alternative energy sources are becoming an indispensable factor in future life.

[0006] In particular, as technology development and demand for mobile devices increase, demand for secondary batteries as eco-friendly alternative energy sources has significantly increased.

[0007] In addition, recently, as concerns about environmental problems have grown, a large amount of research has been conducted on electric vehicles (EVs) and hybrid electric vehicles (HEVs) that can replace vehicles using fossil fuels such as gasoline vehicles and diesel vehicles, which are one of the main causes of air pollution. Lithium secondary batteries with high energy density, high discharge voltage and high output stability have been mainly studied and used as power sources for these electric vehicles (EVs) and hybrid electric vehicles (HEVs).

[0008] In secondary batteries, lithium metal is typically used as the anode, but as battery short circuits and the accompanying risk of explosion due to dendrite formation have become problems, the use of carbon-based active materials that can reversibly intercalate and deintercalate lithium ions while maintaining structural and electrical properties has emerged.

[0009] Various types of carbon-based active materials have been used, including artificial graphite, natural graphite, and hard carbon. Graphite-based active materials are the most widely used due to their excellent reversibility, ensuring the longevity of lithium secondary batteries. Because graphite-based active materials have a low discharge voltage of -0.2V relative to lithium, batteries using graphite-based active materials can exhibit a high discharge voltage of 3.6V, offering numerous advantages in terms of the energy density of lithium batteries.

[0010] Among graphite-based active materials, natural graphite has the advantages of high output and high capacity, but there are concerns that expansion problems may occur due to a high degree of orientation, and there is a problem of poor high-temperature characteristics due to relatively more functional groups on its surface compared to artificial graphite.

[0011] In contrast, artificial graphite has the advantages of having a better expansion suppression effect than natural graphite and excellent high-temperature properties, but is known to be inferior in output properties. In this regard, research is underway to improve the output properties of artificial graphite.

[0012] To improve the output characteristics of artificial graphite, research has been conducted on reducing the particle size of artificial graphite or coating it with amorphous carbon, etc. However, reducing the particle size of artificial graphite can lead to reduced grinding yield and capacity. Furthermore, coating artificial graphite with amorphous carbon is undesirable because it increases the specific surface area, leading to a decrease in initial efficiency and deterioration in storage performance.

[0013] Therefore, there is an urgent need to develop a negative electrode active material that can improve the capacity, initial efficiency, and output characteristics of artificial graphite.

[0014] Japanese Patent No. 4403327 discloses graphite powder for a negative electrode of a lithium ion secondary battery, but does not provide an alternative solution to the above-mentioned problems.

[0015] [Prior art literature]

[0016] [Patent Document]

[0017] Japanese Patent No. 4403327 Summary of the Invention

[0018] Technical issues

[0019] One aspect of the present invention provides a negative electrode active material in which output characteristics and capacity characteristics are simultaneously improved and which has high initial efficiency.

[0020] Another aspect of the present invention provides a negative electrode comprising the negative electrode active material.

[0021] Another aspect of the present invention provides a secondary battery including the negative electrode.

[0022] Technical Solution

[0023] According to one aspect of the present invention, there is provided a negative electrode active material comprising artificial graphite particles; and sulfur (S) distributed in the artificial graphite particles, wherein the sulfur content is 15 ppm to 40 ppm.

[0024] According to another aspect of the present invention, there is provided a negative electrode comprising a negative electrode current collector; and a negative electrode active material layer disposed on the negative electrode current collector, wherein the negative electrode active material layer comprises the above-mentioned negative electrode active material.

[0025] According to another aspect of the present invention, there is provided a secondary battery including the above-mentioned negative electrode; a positive electrode opposite to the negative electrode; a separator disposed between the negative electrode and the positive electrode; and an electrolyte.

[0026] Beneficial effects

[0027] The negative electrode active material of the present invention is characterized in that it contains artificial graphite particles and sulfur distributed within the artificial graphite particles, wherein the content of the sulfur in the negative electrode active material is within a specific range. Because the sulfur distributed within the above-mentioned amount range in the negative electrode active material serves to randomize the crystal structure of the artificial graphite, a stable lithium ion diffusion path can be ensured to improve the output characteristics of the negative electrode active material. Furthermore, because the sulfur does not excessively increase the specific surface area of ​​the negative electrode active material, the initial efficiency and the capacity of the negative electrode active material can be improved. Therefore, the negative electrode and secondary battery containing the negative electrode active material of the present invention can exhibit excellent performance in terms of output characteristics, capacity characteristics, and initial efficiency. DETAILED DESCRIPTION

[0028] It should be understood that the words or terms used in the specification and claims should not be interpreted as the meanings defined in commonly used dictionaries, but it should also be understood that, based on the principle that the inventor can appropriately define the meanings of the words or terms to best explain the invention, the words or terms should be interpreted as having meanings consistent with their meanings in the context of the relevant technologies and technical concepts of the present invention.

[0029] The terms used herein are for the purpose of describing particular exemplary embodiments only and are not intended to be limiting of the present invention.In this specification, unless otherwise indicated, terms in the singular may include plural forms.

[0030] It should also be understood that the terms “comprises,” “includes,” or “has,” when used in this specification, specify the presence of stated features, numbers, steps, elements, or a combination thereof, but do not preclude the presence or addition of one or more other features, numbers, steps, elements, or a combination thereof.

[0031] In this specification, the expression "average particle size (D 50 The average particle size (D) can be defined as the particle size at which the cumulative volume is 50% in the particle size distribution curve of the particles. The average particle size (D) can be measured, for example, using a laser diffraction method. 50 Laser diffraction can typically measure particle sizes from submicrometers to several millimeters, and can obtain results with high reproducibility and high resolution.

[0032] Hereinafter, the present invention will be described in detail.

[0033] negative electrode active material

[0034] The present invention relates to a negative electrode active material, in particular to a negative electrode active material for a lithium secondary battery.

[0035] Specifically, the negative active material according to the present invention includes artificial graphite particles; and sulfur (S) distributed in the artificial graphite particles, wherein the content of the sulfur is 15 ppm to 40 ppm.

[0036] Conventionally, artificial graphite is known to have a lower degree of expansion and excellent storage characteristics compared to natural graphite, but has poor output characteristics. In order to improve the output characteristics of artificial graphite, research is underway to reduce the particle size of artificial graphite or increase the amount of carbon coating. However, these methods are not ideal because they involve problems such as a decrease in the capacity of artificial graphite or a decrease in initial efficiency.

[0037] The raw materials for artificial graphite (coke, etc.) contain impurities such as sulfur (S) and nitrogen (N), most of which are removed during the graphitization of the raw materials. While removing these impurities has the advantage of improving initial efficiency and capacity, there is a problem of deteriorating the output characteristics of artificial graphite due to the overdevelopment of its crystal structure.

[0038] To address this issue, the negative electrode active material of the present invention is characterized in that it includes artificial graphite particles and sulfur distributed within the artificial graphite particles, wherein the content of the sulfur in the negative electrode active material is within the above-mentioned range. Because the sulfur distributed within the above-mentioned amount range in the negative electrode active material serves to randomize the crystal structure of the artificial graphite, a stable lithium ion diffusion path can be ensured to improve the output characteristics of the negative electrode active material. Furthermore, because the sulfur does not excessively increase the specific surface area of ​​the negative electrode active material, the initial efficiency can be improved and the capacity of the negative electrode active material can be improved. Therefore, the negative electrode and secondary battery containing the negative electrode active material of the present invention can exhibit excellent performance in terms of output characteristics, capacity characteristics, and initial efficiency.

[0039] The negative electrode active material includes artificial graphite particles.

[0040] The advantages of these artificial graphite particles are that they expand less than natural graphite and have excellent storage characteristics. Furthermore, as will be described later, because the negative electrode active material according to the present invention contains an ideal level of elemental sulfur in the artificial graphite particles, it is possible to improve output characteristics to an excellent level without reducing initial efficiency and capacity.

[0041] The artificial graphite particles may be in the form of secondary particles formed by combining multiple primary artificial graphite particles. Specifically, the artificial graphite particles may be a combination of multiple primary artificial graphite particles. When the artificial graphite particles are in the form of secondary particles, since spaces are formed between the primary artificial graphite particles, the output characteristics of the artificial graphite particles can be further improved by ensuring these spaces.

[0042] For the artificial graphite particles in the form of secondary particles, the secondary particles can be a combination of multiple artificial graphite primary particles. Specifically, in the artificial graphite particles in the form of secondary particles, the artificial graphite primary particles are not combined with each other by van der Waals forces, but multiple artificial graphite primary particles can be combined or aggregated using a resin adhesive such as asphalt to form secondary particles.

[0043] The artificial graphite primary particles can be formed by pulverizing a carbon precursor. The carbon precursor can be at least one selected from the group consisting of coal-based heavy oil, fiber-based heavy oil, tar, pitch, and coke. Because the artificial graphite primary particles formed from the powdered carbon precursor can have improved cohesion, they can be formed to have high hardness.

[0044] The artificial graphite particles in the form of secondary particles can be formed by adding a powdered carbon precursor to a reactor; operating the reactor to combine the powder by centrifugal force to form secondary particles formed by combining primary particles; and graphitizing the powder at a temperature of 2,500°C to 3,500°C, for example, 2,700°C to 3,200°C. During the graphitization process, the primary and secondary particles can be graphitized simultaneously. During the powder combining process, a resin binder such as asphalt can be added to the reactor, and heat treatment can be performed at a temperature of approximately 400°C to 800°C.

[0045] In the case where the artificial graphite particles are in the form of secondary particles, the average particle size (D 50 ) can be in the range of 5 μm to 15 μm, for example, 8.7 μm to 12.0 μm. When the average particle size (D 50 ) is within the above range, it is ideal because both output characteristics and capacity characteristics can be improved at the same time.

[0046] The negative electrode active material includes sulfur (S) distributed in the artificial graphite particles. The sulfur content in the negative electrode active material is 15 ppm to 40 ppm.

[0047] Typically, the sulfur is treated as an impurity and can be removed during the graphitization and iron removal process during the preparation of artificial graphite. For example, during the preparation of artificial graphite, the impurity removal process is performed by heat treating the raw materials (coke, etc.) at a high temperature of 1,000°C to 1,500°C before grinding. However, in the case of the negative electrode active material of the present invention, the sulfur can be distributed in the artificial graphite particles in a desired amount to randomize the crystal structure of the artificial graphite particles, thereby increasing the lithium ion diffusion path of the artificial graphite particles to improve output characteristics. In particular, the raw materials (coke, etc.) used during the preparation of artificial graphite particles have a mosaic phase rather than a fibrous phase due to the inclusion of sulfur, resulting in a random crystal structure, which can reduce the lithium ion diffusion resistance. In the case where the negative electrode active material contains excessive sulfur, the electrolyte side reaction is aggravated and the initial efficiency is reduced due to the increase in the specific surface area of ​​the negative electrode active material, and the degree of graphitization may be reduced and the capacity may be reduced due to the excessive increase in the ratio of the isotropic mosaic phase. However, since the negative electrode active material of the present invention does not contain excessive sulfur, the capacity and initial efficiency can be improved.

[0048] If the sulfur content in the negative electrode active material is less than 15 ppm, the crystal structure of the artificial graphite particles may not be randomized, resulting in a decrease in the diffusion rate of lithium ions and deterioration in output characteristics. If the sulfur content in the negative electrode active material exceeds 40 ppm, the excess sulfur increases the specific surface area of ​​the artificial graphite, potentially leading to excessive side reactions with the electrolyte and a decrease in initial efficiency. Furthermore, the excess isotropic mosaic phase in the artificial graphite particles decreases the degree of graphitization and reduces the capacity of the negative electrode active material, making this undesirable.

[0049] The sulfur content in the negative electrode active material is preferably 18 ppm to 30 ppm, more preferably 19.0 ppm to 25.5 ppm, and most preferably 20.0 ppm to 22.5 ppm. When the sulfur content is within the above range, the output characteristics, capacity characteristics, and initial efficiency of the negative electrode active material can be improved simultaneously.

[0050] The sulfur may be distributed on the surface and / or inside the artificial graphite particles. More specifically, the sulfur may be distributed in the crystal structure of the artificial graphite particles.

[0051] The amount of sulfur according to the present invention can be achieved by controlling the heat treatment conditions of the graphitization and iron removal steps during the production of artificial graphite particles, omitting the calcination step typically performed during the production of artificial graphite, or controlling the calcination conditions. Specifically, the amount of sulfur according to the present invention can be achieved by omitting the calcination step typically performed before grinding the artificial graphite raw material (coke, etc.) during the production of artificial graphite particles, or by performing the calcination step at a low temperature of 500°C or lower, preferably 300°C or lower.

[0052] The amount of sulfur can be measured by an inductively coupled plasma (ICP) analysis method.

[0053] The interplanar spacing d002 measured by X-ray diffraction (XRD) analysis of artificial graphite particles can be in the range of 0.3354nm to 0.3370nm, preferably 0.3357nm to 0.3360nm, and more preferably greater than 0.3357nm to less than 0.3360nm. When the spacing d002 is within the above range, the capacity of the negative electrode active material can be ensured, and therefore it is ideal.

[0054] Furthermore, the crystallite size, as measured by the full width at half maximum of the peak of the (002) plane in the X-ray diffraction spectrum of the artificial graphite particles, can be in the range of 60 nm or more, preferably 60 nm to 200 nm, and more preferably 60 nm to 120 nm. When the crystallite size is within the above range, a negative electrode active material having guaranteed lifespan characteristics and output characteristics can be realized.

[0055] After performing XRD analysis on the negative electrode active material using an X-ray diffraction (XRD) analyzer and obtaining the half-maximum width and angle (θ) of the (002) peak of the artificial graphite particles through XRD analysis, the crystallite size can be obtained by substituting the half-maximum width and angle (θ) into the Scherrer formula.

[0056] [Scherrer formula]

[0057] Crystallite size (nm) = K × λ / FWHM × Cosθ

[0058] In the above formula, K is the Scherrer constant, λ is the wavelength of the light source, FWHM is the full width at half maximum of the (002) peak of the artificial graphite particles during XRD analysis, and Cosθ is the cosine value of the angle θ corresponding to the (002) peak of the artificial graphite particles.

[0059] The negative electrode active material may further include a carbon coating disposed on the artificial graphite particles. The carbon coating may help improve the structural stability of the artificial graphite particles and prevent side reactions between the negative electrode active material and the electrolyte.

[0060] The carbon coating layer may be present in an amount of 0.1 to 5% by weight, for example, 1 to 4% by weight, in the negative electrode active material. The presence of the carbon coating layer can improve the structural stability of the negative electrode active material. However, excessive formation of the carbon coating layer may increase the specific surface area of ​​the negative electrode during compression, leading to a decrease in initial efficiency and degradation of high-temperature storage performance. Therefore, forming the carbon coating layer within the above range is ideal.

[0061] The carbon coating layer may include amorphous carbon. For example, the carbon coating layer may be formed by applying at least one carbon coating layer precursor selected from the group consisting of coal-based heavy oil, fiber-based heavy oil, tar, pitch, and coke to the artificial graphite particles and then heat-treating the carbon coating layer precursor. To promote uniform formation of the carbon coating layer, the heat treatment process for forming the carbon coating layer may be performed at a temperature of 1,000°C to 1,500°C.

[0062] The average particle size of the negative electrode active material (D 50 ) can be 10 μm to 25 μm, preferably 12 μm to 20 μm, and more preferably 16 μm to 19 μm. In particular, when the negative electrode active material includes artificial graphite particles in the form of secondary particles and the average particle size is within the above range, it can be evaluated that the secondary particles are smoothly assembled, and because the orientation index of the negative electrode is reduced to an appropriate level, excellent output characteristics can be achieved, expansion can be prevented, and processability in the preparation of the negative electrode can be improved.

[0063] The Brunauer-Emmett-Teller (BET) specific surface area of ​​the negative electrode active material may be 0.3 m 2 / g to 2.5m 2 / g, for example 0.5m 2 / g to 1.1m 2 When the BET specific surface area is within the above range, it is ideal in terms of being able to further improve initial efficiency by preventing a side reaction with an electrolyte.

[0064] The true density of the negative electrode active material may be 2.2 g / cc to 2.3 g / cc, preferably 2.22 g / cc to 2.26 g / cc, and more preferably 2.23 g / cc to 2.25 g / cc. When the true density is within the above range, the negative electrode active material is evaluated to have an ideal level of graphitization and can ensure discharge capacity, and is therefore ideal.

[0065] The true density is defined as the density of the particles themselves excluding the gaps between the particles. After measuring the true volume of the particles using a gas pycnometer, the true density can be calculated by dividing the particle mass by the true volume.

[0066] negative electrode

[0067] Furthermore, the present invention provides a negative electrode comprising the negative electrode active material, and more particularly, a negative electrode for a lithium secondary battery.

[0068] The negative electrode comprises a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector. The negative electrode active material layer comprises the negative electrode active material.

[0069] As the negative electrode current collector, any negative electrode current collector commonly used in the art can be used without limitation. For example, there is no particular limitation on the negative electrode current collector as long as it has high conductivity and does not cause adverse chemical changes in the lithium secondary battery. For example, the negative electrode current collector can include at least one selected from copper, stainless steel, aluminum, nickel, titanium, calcined carbon, and aluminum-cadmium alloy, preferably copper.

[0070] The negative electrode current collector may have fine surface irregularities to improve bonding strength with the negative electrode active material, and may be used in various shapes such as a film, sheet, foil, mesh, porous body, foam body, non-woven fabric body, and the like.

[0071] The thickness of the negative electrode current collector may generally be 3 μm to 500 μm.

[0072] The negative electrode active material layer is stacked on the negative electrode current collector and includes the negative electrode active material.

[0073] The negative electrode active material may be contained in the negative electrode active material layer in an amount of 80 wt % to 99 wt %, for example, 93 wt % to 98 wt %.

[0074] In addition to the negative electrode active material, the negative electrode active material layer may further include a binder, a conductive agent, and / or a thickener.

[0075] The binder is a component that facilitates adhesion between the active material and / or the current collector, wherein the content of the binder in the negative electrode active material layer may generally be 1 wt % to 30 wt %, for example, 1 wt % to 10 wt %.

[0076] The binder may include at least one selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR) and fluororubber, preferably at least one selected from polyvinylidene fluoride and styrene-butadiene rubber.

[0077] As the thickener, any thickener used for conventional lithium secondary batteries can be used, and an example thereof is carboxymethyl cellulose (CMC).

[0078] The conductive agent is a component for further improving the conductivity of the negative electrode active material, wherein the content of the conductive agent in the negative electrode active material layer may be 1 wt % to 30 wt %, for example, 1 wt % to 10 wt %.

[0079] Any conductive agent can be used without particular limitation, as long as it has conductivity and does not cause adverse chemical changes in the battery. For example, conductive materials such as graphite, such as natural graphite or artificial graphite; carbon black, such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers, such as carbon fibers or metal fibers; fluorocarbons; metal powders, such as aluminum powder and nickel powder; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides, such as titanium oxide; or polyphenylene derivatives can be used. Specific examples of commercial conductive agents include acetylene black products (Chevron Chemical Company, Danka Black (Danka Singapore Pte. Ltd.), or Gulf Oil Company), Ketjen black, ethylene carbonate (EC) products (Armak Company), Vulcan XC-72 (Cabot Corporation), and Super P (Temeco Graphite and Carbon Company).

[0080] The negative electrode active material layer may be prepared by mixing the negative electrode active material and at least one selected from the binder, the conductive agent, and the thickener in a solvent to prepare a negative electrode slurry, coating the negative electrode collector with the negative electrode slurry, and rolling and drying the coated negative electrode collector.

[0081] The solvent may include water or an organic solvent such as N-methyl-2-pyrrolidone (NMP), and may be used in an amount such that a desired viscosity is obtained when the negative electrode active material and, optionally, the binder and the conductive agent are included. For example, the solvent may be included in an amount such that the concentration of the solid component containing the negative electrode active material and, optionally, at least one selected from the binder, the thickener, and the conductive agent is in the range of 50% to 95% by weight, for example, 70% to 90% by weight.

[0082] The area ratio I(004) / I(110) (orientation index) of the negative electrode during X-ray diffraction analysis may be in the range of 8 to 14, for example, 11.5 to 12.5. When the area ratio I(004) / I(110) is within the above range, the active material particles can be arranged to minimize the lithium ion diffusion path, thereby achieving an excellent effect of reducing lithium ion diffusion resistance. The orientation index can be achieved by using the above-mentioned negative electrode active material in the negative electrode.

[0083] secondary batteries

[0084] Furthermore, the present invention provides a secondary battery comprising the negative electrode, more particularly a lithium secondary battery.

[0085] The secondary battery may include the above-described negative electrode, a positive electrode opposite to the negative electrode, a separator disposed between the negative electrode and the positive electrode, and an electrolyte.

[0086] The positive electrode may include a positive electrode current collector; and a positive electrode active material layer disposed on the positive electrode current collector.

[0087] As the positive electrode current collector, any positive electrode current collector commonly used in the art can be used without limitation. For example, the positive electrode current collector is not particularly limited as long as it has high conductivity and does not cause adverse chemical changes in the secondary battery. For example, the positive electrode current collector may comprise at least one selected from copper, stainless steel, aluminum, nickel, titanium, calcined carbon, and an aluminum-cadmium alloy, preferably aluminum.

[0088] The positive electrode current collector may have fine surface irregularities to improve bonding strength with the positive electrode active material, and may be used in various shapes such as a film, sheet, foil, mesh, porous body, foam body, non-woven fabric body, and the like.

[0089] The thickness of the positive electrode current collector may generally be 3 μm to 500 μm.

[0090] The positive electrode active material layer may include a positive electrode active material.

[0091] The positive electrode active material is a compound capable of reversibly inserting and extracting lithium, wherein specifically, the positive electrode active material may include a lithium composite metal oxide containing lithium and at least one metal such as cobalt, manganese, nickel or aluminum. More specifically, the lithium composite metal oxide may include lithium manganese oxides (such as LiMnO2, LiMn2O4, etc.), lithium cobalt oxides (such as LiCoO2, etc.), lithium nickel oxides (such as LiNiO2, etc.), lithium nickel manganese ... manganese manganese oxides (such as LiMnO2, LiMn2O4, etc.), lithium cobalt oxides (such as LiCoO2, etc.), lithium nickel manganese oxides (such as LiNiO2, etc.), lithium nickel manganese oxides (such as LiNiO2, etc.), lithium nickel manganese oxides (such as LiNiO2, etc.), lithium nickel manganese oxides (such as LiNiO2, etc.), lithium nickel manganese oxides (such as LiNiO2, etc.), lithium nickel manganese oxides (such as LiNiO2, etc.), lithium nickel manganese oxides (such as LiNiO2, etc.), lithium manganese manganese oxides (such as LiMnO2, Li 1-Y Mn Y O2 (where 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 (where 0 < Y1 < 1), etc., lithium manganese cobalt oxides (e.g., LiCo 1-Y2 Mn Y2 O2 (where 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) oxides (e.g., Li(Ni p2 Co q2 Mn r3 M S2 )O2 (where M is selected from the group consisting of aluminum (Al), iron (Fe), vanadium (V), chromium (Cr), titanium (Ti), tantalum (Ta), magnesium (Mg), and molybdenum (Mo), p2, q2, r3, and s2 are atomic fractions of respective independent elements, where 0 < p2 < 1, 0 < q2 < 1, 0 < r3 < 1, 0 < S2 < 1, p2 + q2 + r3 + S2 = 1), etc.), and may contain any one or a mixture of two or more of them. Among these materials, in terms of improving the capacity characteristics and stability of the battery, the lithium composite metal oxide may contain LiCoO2, LiMnO2, LiNiO2, lithium nickel manganese cobalt oxides (e.g., 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), or lithium nickel cobalt aluminum oxides (e.g., LiNi 0.8 Co 0.15 Al 0.05O2, etc.), considering the significant improvement brought about by controlling the types and content ratios of the elements constituting the lithium composite metal oxide, the lithium composite metal oxide may include 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 )O2, and any one of them or a mixture of two or more thereof can be used.

[0092] The positive electrode active material may be contained in an amount of 80 wt % to 99 wt % in the positive electrode active material layer.

[0093] The positive electrode active material layer may further include at least one selected from a binder and a conductive agent in addition to the positive electrode active material.

[0094] The binder is a component that helps the bonding between the active material and the conductive agent and the bonding with the current collector, wherein the amount of the binder added is generally 1% to 30% by weight based on the total weight of the positive electrode material mixture. Examples of the binder can be at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber and fluororubber.

[0095] The binder may be contained in the positive electrode active material layer in a content of 1 wt % to 30 wt %.

[0096] Any conductive agent can be used without particular limitation, as long as it has conductivity and does not cause adverse chemical changes in the battery. For example, conductive materials such as graphite, carbon materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black can be used; conductive fibers such as carbon fibers or metal fibers; fluorocarbons; metal powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides such as titanium oxide; and polyphenylene derivatives can be used. Specific examples of commercial conductive agents include acetylene black products (Chevron Chemical Company, Danka Black (Danka Singapore Pte. Ltd.), or Gulf Oil Company), Ketjen black, ethylene carbonate (EC) products (Armak Company), Vulcan XC-72 (Cabot Corporation), and Super P (Temeco Graphite and Carbon Company).

[0097] The conductive agent may be added to the positive electrode active material layer in an amount of 1 wt % to 30 wt %.

[0098] The separator separates the negative electrode from the positive electrode and provides a lithium ion movement path, wherein as the separator, any separator can be used without particular limitation, as long as it is commonly used in secondary batteries, in particular, a separator having high moisture retention capacity for electrolytes and low resistance to the transfer of electrolyte ions can be used. Specifically, a porous polymer film can be used, for example, a porous polymer film prepared by polyolefin polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers and ethylene / methacrylate copolymers, or a laminated structure thereof of two or more layers. In addition, a typical porous non-woven fabric can be used, for example, a non-woven fabric formed by high melting point glass fiber or polyethylene terephthalate fiber. In addition, a coated separator comprising a ceramic component or a polymer component can be used to ensure heat resistance or mechanical strength, and a separator with a single layer or multilayer structure can be selectively used.

[0099] In addition, the electrolyte used in the present invention may include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel polymer electrolyte, a solid inorganic electrolyte or a molten inorganic electrolyte that can be used to manufacture a lithium secondary battery, but the present invention is not limited thereto.

[0100] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0101] As the organic solvent, any organic solvent can be used without particular limitation, as long as it can be used as a medium through which ions participating in the electrochemical reaction of the battery can move. Specifically, as the organic solvent, ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone and ε-caprolactone can be used; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; or carbonate solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC) and propylene carbonate (PC); alcohol solvents such as ethanol and isopropanol; nitriles such as R-CN (wherein R is a linear, branched or cyclic C2-C20 hydrocarbon group, and may contain a double bond aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes. Among these solvents, carbonate solvents can be preferably used, for example, a mixture of a cyclic carbonate (for example, ethylene carbonate or propylene carbonate) with high ionic conductivity and high dielectric constant and a low-viscosity straight-chain carbonate compound (for example, ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate) can be more preferably used, the mixture can improve the charge / discharge performance of the battery. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of about 1:1 to about 1:9, the electrolyte can achieve excellent performance.

[0102] The lithium salt can be used without particular limitation, as long as it is a compound that can provide the lithium ions used in the lithium secondary battery. Specifically, as the lithium salt, LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI or LiB(C2O4)2 can be used. The lithium salt can be used in a concentration range of 0.1M to 2.0M. When the concentration of the lithium salt is within the above range, since the electrolyte can have appropriate conductivity and viscosity, excellent electrolyte performance can be obtained and lithium ions can be effectively moved.

[0103] As described above, because the lithium secondary battery according to the present invention consistently exhibits excellent discharge capacity, output characteristics, and lifespan characteristics, the lithium secondary battery is suitable for portable devices such as mobile phones, notebook computers, and digital cameras, as well as electric vehicles such as hybrid electric vehicles (HEVs). In particular, it can be preferably used as a component battery of a medium-to-large battery module. Therefore, the present invention also provides a medium-to-large battery module including the above-described secondary battery as a unit cell.

[0104] The medium and large-sized battery module can be preferably used for power sources requiring high output and large capacity, such as electric vehicles, hybrid electric vehicles, and power storage systems.

[0105] The following will describe in detail embodiments of the present invention in a manner that one skilled in the art can easily implement the present invention. However, the present invention can be embodied in many different forms and should not be construed as limited to the embodiments described herein.

[0106] Example

[0107] 1. Preparation of negative electrode active materials

[0108] Example 1: Preparation of negative electrode active material

[0109] The average particle size (D 50 ) of 10 μm. No separate calcination process was performed during the grinding of needle coke. The powder and petroleum-based pitch were mixed in a weight ratio of 92:8, and heat-treated at 550° C. for 10 hours in an inert gas (N2) atmosphere using a vertical granulator to prepare secondary particles (average particle size (D)) in which a plurality of primary particles were aggregated or combined. 50 ): 15.5μm).

[0110] Next, artificial graphite particles in the form of secondary particles were prepared by graphitizing the secondary particles by performing a heat treatment at 3,000° C. for 20 hours or more in an inert gas atmosphere.

[0111] The artificial graphite particles in the form of secondary particles and petroleum-based pitch were mixed and heat-treated in a roller kiln at 1,300° C. to form an amorphous carbon coating on the secondary particles.

[0112] The sulfur content of the negative electrode active material prepared in this way was 23.1 ppm, and the average particle size (D 50 ) is 15.5 μm, the true density is 2.24 g / cc, and the BET specific surface area is 0.8 m 2 / g, and the amount of the amorphous carbon coating in the negative electrode active material is 3 wt %.

[0113] In addition, d002 measured by XRD of the artificial graphite particles included in the negative electrode active material was 0.3358 nm, and the crystallite size determined by the full width at half maximum of the peak of the (002) plane was 75 nm.

[0114] * d002 of the artificial graphite particles is obtained by the Bragg equation using the Bragg 2θ angle at the peak of the (002) plane appearing in the X-ray diffraction spectrum after XRD analysis of the negative electrode active material.

[0115] *The crystallite size measured by the full width at half maximum of the peak of the (002) plane of the artificial graphite particles is obtained by using the full width at half maximum of the peak of the (002) plane in the X-ray diffraction spectrum according to the Scherrer equation. The detailed conditions are as follows.

[0116] 1) Type and wavelength of light source: The wavelength of X-rays generated by Cu Kα was used, and the wavelength (λ) of the light source was 0.15406 nm.

[0117] 2) Sample preparation method: 0.3 g of negative electrode active material was placed in a cylindrical holder with a diameter of 2.5 cm and a height of 2.5 mm, and flattened with a glass slide so that the sample height in the holder was constant to prepare the sample for XRD analysis.

[0118] 3) XRD analyzer settings: Scan time set to 1 hour and 15 minutes, measurement range set to the region of 10° to 90° 2θ, and step time and step size set to scan at a rate (2θ) of 0.02° / s. In this case, to measure the peak of the (002) plane of the artificial graphite particles, the peak in the region of 26.3° to 26.5° 2θ was measured.

[0119] Thereafter, the crystallite size of the artificial graphite particles was calculated using the following Scherrer formula.

[0120] [Scherrer formula]

[0121] Crystallite size (nm) = K × λ / FWHM × Cosθ

[0122] In the above formula, K is the Scherrer constant, λ is the wavelength of the light source, FWHM is the full width at half maximum of the (002) peak of the artificial graphite particles during XRD analysis, and Cosθ is the cosine value of the angle θ corresponding to the (002) peak of the artificial graphite particles.

[0123] Example 2: Preparation of negative electrode active material

[0124] The average particle size (D) was obtained by heat treating the needle coke up to 200°C at a heating rate of 10°C / min and grinding the needle coke using an impact mill. 50 ) of 9 μm. The powder and petroleum asphalt were mixed in a weight ratio of 90:10, and heat-treated at 600° C. for 8 hours in an inert gas (N2) atmosphere using a vertical granulator to prepare secondary particles (average particle size (D 50 ): 13.5μm).

[0125] Next, artificial graphite particles in the form of secondary particles were prepared by graphitizing the secondary particles by performing a heat treatment at 3,000° C. for 20 hours or more in an inert gas atmosphere.

[0126] The artificial graphite particles in the form of secondary particles and petroleum-based pitch were mixed and heat-treated in a roller kiln at 1,250° C. to form an amorphous carbon coating on the secondary particles.

[0127] The sulfur content of the negative electrode active material prepared in this way was 26.2 ppm, and the average particle size (D 50 ) is 13.5 μm, the true density is 2.24 g / cc, and the BET specific surface area is 1.0 m 2 / g, and the amount of the amorphous carbon coating in the negative electrode active material is 3 wt %.

[0128] In addition, d002 measured by XRD of the artificial graphite particles included in the negative electrode active material was 0.3359 nm, and the crystallite size determined by the full width at half maximum of the peak of the (002) plane was 64 nm.

[0129] Example 3: Preparation of negative electrode active material

[0130] The average particle size (D) was obtained by grinding petroleum coke using an impact mill. 50 ) of 11 μm. No separate calcination process was performed during the grinding of this general coke. Secondary particles (average particle size (D)) in which a plurality of primary particles were aggregated were prepared by heat-treating the powder at 600° C. for 10 hours in an inert gas (N2) atmosphere using a vertical granulator. 50 ): 18.1μm).

[0131] Next, artificial graphite particles in the form of secondary particles were prepared by graphitizing the secondary particles by performing a heat treatment at 3,000° C. for 20 hours or more in an inert gas atmosphere.

[0132] The artificial graphite particles in the form of secondary particles and petroleum-based pitch were mixed and heat-treated in a roller kiln at 1,300° C. to form an amorphous carbon coating on the secondary particles.

[0133] The sulfur content of the negative electrode active material prepared in this way was 22.2 ppm, the average particle size (D 50 ) is 18.1 μm, the true density is 2.23 g / cc, and the BET specific surface area is 0.7 m 2 / g, and the amount of the amorphous carbon coating in the negative electrode active material is 3 wt %.

[0134] In addition, d002 measured by XRD of the artificial graphite particles included in the negative electrode active material was 0.3358 nm, and the crystallite size determined by the full width at half maximum of the peak of the (002) plane was 69 nm.

[0135] Example 4: Preparation of negative electrode active material

[0136] The negative electrode active material was prepared in the same manner as in Example 3, except that the average particle size (D 50 ) is a powder of 10 μm.

[0137] The sulfur content of the negative electrode active material prepared in this way was 29.4 ppm, and the average particle size (D 50 ) is 19.4 μm, the true density is 2.24 g / cc, and the BET specific surface area is 0.6 m 2 / g, and the amount of the amorphous carbon coating in the negative electrode active material is 3 wt %.

[0138] In addition, d002 measured by XRD of the artificial graphite particles included in the negative electrode active material was 0.3359 nm, and the crystallite size determined by the full width at half maximum of the peak of the (002) plane was 66 nm.

[0139] Comparative Example 1: Preparation of negative electrode active material

[0140] The average particle size (D) was obtained by heat treating needle coke up to 1,000°C at a heating rate of 25°C / min and grinding the needle coke using an impact mill. 50 ) of 10 μm. The powder and petroleum asphalt were mixed in a weight ratio of 87:13, and heat-treated at 550° C. for 10 hours in an inert gas (N2) atmosphere using a vertical granulator to prepare secondary particles (average particle size (D 50 ): 22.8μm).

[0141] Next, artificial graphite particles in the form of secondary particles were prepared by graphitizing the secondary particles by performing a heat treatment at 3,000° C. for 20 hours or more in an inert gas atmosphere.

[0142] The artificial graphite particles in the form of secondary particles and petroleum-based pitch were mixed and heat-treated in a roller kiln at 1,300° C. to form an amorphous carbon coating on the secondary particles.

[0143] The sulfur content of the negative electrode active material prepared in this way was 9.4 ppm, and the average particle size (D 50 ) is 22.8 μm, the true density is 2.24 g / cc, and the BET specific surface area is 0.7 m 2 / g, and the amount of the amorphous carbon coating in the negative electrode active material is 3 wt %.

[0144] In addition, d002 measured by XRD of the artificial graphite particles included in the negative electrode active material was 0.3358 nm, and the crystallite size determined by the full width at half maximum of the peak of the (002) plane was 71 nm.

[0145] Comparative Example 2: Preparation of negative electrode active material

[0146] A negative electrode active material was prepared in the same manner as in Comparative Example 1, except that the average particle size (D 50 ) is a powder of 8.5 μm.

[0147] The sulfur content of the negative electrode active material prepared in this way was 8.3 ppm, and the average particle size (D 50 ) is 17.9 μm, the true density is 2.25 g / cc, and the BET specific surface area is 0.8 m 2 / g, and the amount of the amorphous carbon coating in the negative electrode active material is 3 wt %.

[0148] In addition, d002 measured by XRD of the artificial graphite particles included in the negative electrode active material was 0.3358 nm, and the crystallite size determined by the full width at half maximum of the peak of the (002) plane was 78 nm.

[0149] Comparative Example 3: Preparation of negative electrode active material

[0150] A negative electrode active material was prepared in the same manner as in Comparative Example 1, except that the average particle size (D 50 ) is a powder of 9.5 μm, and the mixing weight ratio of the artificial graphite particles in the form of secondary particles to the petroleum-based pitch is adjusted so that the amount of the amorphous carbon coating in the negative electrode active material is 4 weight%.

[0151] The sulfur content of the negative electrode active material prepared in this way was 10.2 ppm, and the average particle size (D 50 ) is 19.7 μm, the true density is 2.25 g / cc, and the BET specific surface area is 0.6 m 2 / g, and the amount of the amorphous carbon coating in the negative electrode active material is 4 wt%.

[0152] In addition, d002 measured by XRD of the artificial graphite particles included in the negative electrode active material was 0.3358 nm, and the crystallite size determined by the full width at half maximum of the peak of the (002) plane was 81 nm.

[0153] Comparative Example 4: Preparation of negative electrode active material

[0154] The average particle size (D) was obtained by grinding petroleum coke using an impact mill. 50 ) was a powder of 14.6 μm. Next, heat treatment was performed at 2,400° C. in an inert gas (N 2 ) atmosphere to prepare a negative electrode active material (soft carbon) of Comparative Example 4.

[0155] The sulfur content of the negative electrode active material prepared in this way was 74.0 ppm, and the average particle size (D 50 ) is 14.6 μm, the true density is 2.12 g / cc, and the BET specific surface area is 1.9 m 2 / g.

[0156] In addition, d002 measured by XRD of the soft carbon particles included in the negative electrode active material was 0.348 nm.

[0157] Comparative Example 5: Preparation of negative electrode active material

[0158] The negative electrode active material was prepared in the same manner as in Example 1, except that the average particle size (D 50 ) was a powder of 9.0 μm, and no amorphous carbon coating was formed on the artificial graphite in the form of secondary particles.

[0159] The sulfur content of the negative electrode active material prepared in this way was 52.0 ppm, and the average particle size (D 50 ) is 15.2 μm, the true density is 2.20 g / cc, the d002 measured by XRD is 0.3380 nm, and the BET specific surface area is 1.2 m 2 / g.

[0160] In addition, d002 measured by XRD of the artificial graphite particles included in the negative electrode active material was 0.3380 nm, and the crystallite size determined by the full width at half maximum of the peak of the (002) plane was 20 nm.

[0161] 2. Preparation of negative electrode

[0162] The negative electrode active material prepared in Example 1, carbon black as a conductive agent, styrene-butadiene rubber as a binder, and carboxymethyl cellulose as a thickener were mixed in a weight ratio of 95.3:1.0:1.2:2.5, and water was added to prepare a negative electrode slurry.

[0163] The negative electrode slurry was coated on a copper negative electrode collector (thickness: 15 μm), vacuum dried at about 130° C. for 8 hours, and rolled to form a negative electrode active material layer (thickness: 84 μm) to prepare the negative electrode of Example 1. In this case, the negative electrode was prepared so that the negative electrode loading was 3.6 mAh / cm 2 .

[0164] Negative electrodes of Examples 2 to 4 and Comparative Examples 1 to 5 were prepared in the same manner as in Example 1, except that the negative electrode active materials prepared in Examples 2 to 4 and Comparative Examples 1 to 5 were used, respectively.

[0165] The orientation index of each negative electrode of Examples and Comparative Examples was obtained, that is, the area ratio I(004) / I(110) obtained by measuring the (004) plane and the (110) plane by XRD and integrating the measured XRD peaks.

[0166] [Table 1]

[0167]

[0168] Experimental example

[0169] <Preparation of Secondary Battery>

[0170] By using Li[Ni 0.6 Mn 0.2 Co 0.2 ]O2, carbon black as a conductive agent, and PVdF as a binder were mixed in a weight ratio of 94:4:2 and N-methylpyrrolidone was added as a solvent to prepare a positive electrode slurry. The positive electrode slurry was coated on aluminum foil, vacuum dried at about 130°C for 8 hours, and rolled to form a positive electrode. In this case, the positive electrode was made so that the positive electrode load was 3.34 mAh / cm 2 .

[0171] After a polyethylene separator was disposed between each of the negative electrodes prepared in Examples 1 to 4 and Comparative Examples 1 to 5 and the positive electrode, an electrolyte was injected to prepare secondary batteries of Examples and Comparative Examples.

[0172] Experimental Example 1: Output Characteristics Evaluation

[0173] The output performance of the secondary batteries of Examples and Comparative Examples prepared above was evaluated.

[0174] Specifically, each secondary battery was discharged at 2.5C and 25°C with the negative electrode at a state of charge (SOC) of 50% to measure voltage change, and resistance was calculated using the formula "resistance = voltage / current". The results are shown in Table 2 below.

[0175] Experimental Example 2: Discharge Capacity and Initial Efficiency Evaluation

[0176] The charge capacity and discharge capacity of the secondary batteries of Examples and Comparative Examples prepared above were measured, and the initial efficiency was calculated by the following formula, and the results are presented in Table 2. The charge and discharge conditions were as follows.

[0177] Charging conditions: CCCV (constant current constant voltage) mode, 0.1C charge, 5mV and 1 / 200C cutoff

[0178] Discharge conditions: CC mode, 0.1C discharge, 1.5V cut-off

[0179] Initial efficiency = (discharge capacity in the first cycle / charge capacity) × 100

[0180] [Table 2]

[0181] Resistance (mOhm) Discharge capacity (mAh / g) Initial efficiency (%) Example 1 1814 352 93.0 Example 2 1826 350 92.5 Example 3 1781 351 93.0 Example 4 1820 350 93.0 Comparative Example 1 1900 350 93.0 Comparative Example 2 1883 352 92.7 Comparative Example 3 1915 353 92.8 Comparative Example 4 1625 242 81.6 Comparative Example 5 1730 329 90.5

[0182] Referring to Table 2, it can be confirmed that the output characteristics, initial discharge capacity, and initial efficiency of the negative electrodes and secondary batteries including the negative electrode active materials of Examples 1 to 4 can be improved simultaneously.

[0183] In the negative electrode active materials of Comparative Examples 1 to 3, since the sulfur content therein was too small, the crystal structure of the artificial graphite particles may not be randomized, and thus the output characteristics were extremely poor.

[0184] In the case of the negative electrode active materials of Comparative Examples 4 and 5, since the sulfur content therein was too large, it was confirmed that the initial efficiency was reduced and the capacity was reduced.

Claims

1. A negative electrode active material, comprising: artificial graphite particles; and sulfur distributed in the artificial graphite particles, The content of sulfur in the negative electrode active material is 15 ppm to 40 ppm. 2 . The negative electrode active material according to claim 1 , wherein the artificial graphite particles are in the form of secondary particles in which a plurality of artificial graphite primary particles are combined.

3. The negative electrode active material according to claim 1, wherein the average particle size D of the artificial graphite primary particles is 50 5μm to 15μm. 4 . The negative electrode active material according to claim 1 , wherein the sulfur is distributed in a crystal structure of the artificial graphite particles. 5 . The negative electrode active material according to claim 1 , further comprising a carbon coating layer disposed on the artificial graphite particles. 6 . The negative electrode active material according to claim 5 , wherein the carbon coating layer has a content of 0.1 wt % to 5 wt % in the negative electrode active material. The negative electrode active material according to claim 5 , wherein the carbon coating layer comprises amorphous carbon.

8. The negative electrode active material according to claim 1, wherein the BET specific surface area of ​​the negative electrode active material is 0.3 m 2 / g to 2.5m 2 / g range.

9. The negative electrode active material according to claim 1, wherein the average particle size D of the negative electrode active material is 50 In the range of 10μm to 25μm. 10 . The negative active material according to claim 1 , wherein a true density of the negative active material is in a range of 2.2 g / cc to 2.3 g / cc. 11 . The negative electrode active material according to claim 1 , wherein a lattice spacing d002 measured by X-ray diffraction analysis of the artificial graphite particles is in the range of 0.3354 nm to 0.3370 nm. 12 . The negative electrode active material according to claim 1 , wherein a crystallite size measured by the full width at half maximum of a peak of a (002) plane in an X-ray diffraction spectrum of the artificial graphite particles is in the range of 60 nm to 200 nm.

13. A negative electrode, comprising: a negative electrode current collector; and a negative electrode active material layer disposed on the negative electrode current collector, The negative electrode active material layer comprises the negative electrode active material according to claim 1 . 14 . The negative electrode according to claim 13 , wherein an area ratio I(004) / I(110) during X-ray diffraction analysis of the negative electrode is in the range of 8 to 14.

15. A secondary battery, comprising: The negative electrode according to claim 13; a positive electrode opposite to the negative electrode; a separator disposed between the negative electrode and the positive electrode; and an electrolyte.

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