KR20240109577A - Negative active material for rechargeable lithium battery and rechargeable lithium battery including same - Google Patents

Abstract

It relates to a negative electrode active material for a lithium secondary battery and a lithium secondary battery containing the same, wherein the negative electrode active material includes an assembly of secondary particles assembled and sphericalized from a plurality of primary particles, tertiary particles containing graphite, and the above 3 It includes an amorphous carbon coating layer surrounding natural graphite, and the primary particles and the secondary particles are natural graphite.

Description

Negative active material for lithium secondary battery and lithium secondary battery containing same {NEGATIVE ACTIVE MATERIAL FOR RECHARGEABLE LITHIUM BATTERY AND RECHARGEABLE LITHIUM BATTERY INCLUDING SAME}

It relates to a negative electrode active material for lithium secondary batteries and a lithium secondary battery containing the same.

Recently, with the rapid spread of electronic devices that use batteries, such as mobile phones, laptop computers, and electric vehicles, the demand for small, lightweight, and relatively high capacity secondary batteries is rapidly increasing. In particular, lithium secondary batteries are attracting attention as a driving power source for portable devices because they are lightweight and have high energy density. Accordingly, research and development to improve the performance of lithium secondary batteries is actively underway.

A lithium secondary battery is a battery that contains a positive electrode and a negative electrode containing an active material capable of intercalation and deintercalation of lithium ions, and an electrolyte solution, and is oxidized and reduced when lithium ions are intercalated/deintercalated from the positive electrode and negative electrode. Electrical energy is produced by reaction.

Transition metal compounds such as lithium cobalt oxide, lithium nickel oxide, and lithium manganese oxide are mainly used as positive electrode active materials for lithium secondary batteries. As anode active materials, natural graphite, artificial graphite, carbon-based active materials such as amorphous carbon, and silicon-based active materials such as Si are used.

Among these, artificial graphite can satisfy high output and long lifespan, but as demand for secondary batteries increases, the demand for natural graphite with excellent price and capacity is continuously increasing. However, in the case of natural graphite, since it is manufactured by spheroidizing flaky graphite with large particles, there is a problem in that the required high output characteristics cannot be satisfied due to the slow insertion and desorption rates of lithium ions due to its relatively large crystallinity compared to artificial graphite.

One embodiment is to provide a negative electrode active material for a lithium secondary battery that exhibits improved high-output characteristics.

Another embodiment provides a lithium secondary battery including the negative electrode active material.

One embodiment includes an assembly of secondary particles obtained by assembling and sphericalizing a plurality of primary particles and tertiary particles including graphite; and an amorphous carbon coating layer surrounding the tertiary particle natural graphite, wherein the primary particle and the secondary particle are natural graphite.

Another embodiment includes a negative electrode including the negative electrode active material; anode; and a lithium secondary battery including an electrolyte.

The anode active material according to one embodiment may exhibit excellent cycle life characteristics and high rate characteristics.

1 is a diagram schematically showing the structure of a negative electrode active material for a lithium secondary battery according to an embodiment.
FIG. 1A is a diagram showing tertiary particles in the structure of the negative electrode active material shown in FIG. 1.
Figure 2 is a diagram schematically showing the structure of a conventional negative electrode active material.
Figure 3 is a diagram showing products in each process during the manufacturing process of a negative active material according to one embodiment.
Figure 4 is a diagram schematically showing a lithium secondary battery in one embodiment.
Figure 5 is an SEM photograph of the negative electrode active material prepared according to Example 1.
Figure 6 is an SEM photograph of the negative electrode active material prepared according to Comparative Example 1.
Figure 7 is an SEM photograph of the negative electrode active material prepared according to Comparative Example 2.
Figure 8 is an SEM photograph of the negative electrode active material prepared according to Comparative Example 4.

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, and the present invention is not limited thereby, and the present invention is only defined by the scope of the claims described below.

Unless otherwise specified herein, when a part such as a layer, membrane, region, plate, etc. is said to be “on” another part, this refers not only to the case where it is “directly above” the other part, but also to the case where there is another part in between. Includes.

Unless otherwise specified in this specification, the singular may also include the plural. In addition, unless otherwise specified, “A or B” may mean “including A, including B, or including A and B.”

Unless otherwise defined herein, the particle size may be an average particle size. In addition, particle size refers to the average particle size (D50), which refers to the diameter of particles with a cumulative volume of 50% by volume in the particle size distribution. The average particle size (D50) can be measured by methods well known to those skilled in the art, for example, using a particle size analyzer, a transmission electron microscope photograph, or a scanning electron microscope. It can also be measured with a photo (Electron Microscope). Another method is to measure using a measuring device using dynamic light-scattering, perform data analysis, count the number of particles for each particle size range, and then calculate from this the average particle diameter ( D50) value can be obtained. Alternatively, it can be measured using a laser diffraction method. When measuring by laser diffraction, more specifically, the particles to be measured are dispersed in a dispersion medium, then introduced into a commercially available laser diffraction particle size measurement device (for example, Microtrac MT 3000) and subjected to ultrasonic waves at about 28 kHz. After irradiation with an output of 60 W, the average particle size (D50) based on 50% of the particle size distribution in the measuring device can be calculated.

According to one embodiment, a negative electrode active material for a lithium secondary battery includes an assembly of secondary particles obtained by assembling and sphericalizing a plurality of primary particles, and tertiary particles including graphite; and an amorphous carbon coating layer surrounding the tertiary particles. In one embodiment, the primary and secondary particles are natural graphite.

Figure 1 is a diagram schematically showing the structure of this negative electrode active material. In Figure 1, the right side shows an enlarged view of the secondary particle 5 corresponding to the dotted line. The negative active material 1 according to one embodiment is a tertiary particle including secondary particles 5 formed by assembling and sphericalizing a plurality of primary particles 3, and an assembly of the secondary particles 5. Includes. In addition, it includes an amorphous carbon coating layer 11 surrounding the tertiary particles. The tertiary particles further include graphite, and the graphite includes artificial graphite. For example, it includes artificial graphite (9) located on the surface of the primary particles (3) and the secondary particles (5).

Additionally, FIG. 1A shows the tertiary particle 7 in FIG. 1 more clearly.

Crystalline carbon, especially natural graphite, used as a negative electrode active material has a higher capacity than artificial graphite, making it possible to realize an ideal capacity close to the theoretical capacity. However, natural graphite consists of large particles with a particle size of 40㎛ to 120㎛, and is generally used as a negative electrode active material by spheroidizing process. Figure 2 shows the structure of a typical natural graphite negative electrode active material 20, which includes flaky natural graphite 23 and an amorphous carbon coating layer 27 located on the surface of the flaky natural graphite particles. Since these negative electrode active materials have limited sites where they can be inserted/discharged during charge/discharge, charge/discharge characteristics, especially high-rate charge/discharge characteristics, are not appropriate.

The anode active material according to one embodiment includes secondary particles obtained by assembling and sphericalizing primary particles obtained by atomizing natural graphite, and tertiary particles containing graphite and an assembly obtained by reassembling the secondary particles. The primary particles and the secondary particles are natural graphite. Additionally, the graphite may be artificial graphite, and the graphite may be artificial graphite located on the surfaces of the primary particles and the surfaces of the secondary particles. This negative electrode active material can increase the insertion/extraction site of lithium ions, thereby facilitating the movement of lithium ions. Accordingly, the negative active material according to one embodiment may exhibit improved rapid charge/discharge characteristics.

In one embodiment, the natural graphite may be flaky natural graphite, and in this 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-scale natural graphite, the number of sites where lithium ions can insert and desorb within the same area increases, and the path through which lithium ions can move becomes shorter, making it more suitable for rapid charging and discharging.

In addition, since the negative electrode active material according to one embodiment is formed by sphericalizing and bending atomized primary particles, lithium can be inserted into the bent portions of the negative electrode active material, especially flaky natural graphite, in addition to both ends. As such, the negative electrode active material according to one embodiment has an increased lithium insertion site, and thus can exhibit an improved charging rate, particularly an improved high rate charging rate.

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

The secondary particles may have a particle size of 5㎛ to 10㎛. 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.

The tertiary particles may have a particle size of 9㎛ to 15㎛. For example, it may be 9.2 μm to 15 μm or 9.5 μm to 15 μm.

When the particle size of the primary particles is 4㎛ to 8㎛, 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㎛ to 10㎛, tertiary particles can be better manufactured and can be more easily applied to lithium secondary batteries. In addition, when the particle size of the tertiary particles is 9㎛ to 15㎛, it can exhibit better initial efficiency and excellent charge/discharge characteristics of the negative electrode, making it more suitable for application to lithium secondary batteries.

In the anode 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. The thickness of the amorphous carbon coating layer can be measured using an SEM or TEM image of the cross section of the anode active material, but is not limited to this, and can be measured by any method that can measure the thickness of the amorphous carbon coating layer in the field. there is. Additionally, the thickness may be an average thickness.

The particle size of the anode 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 ㎛ to 16 ㎛. 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, lithium ions can be easily inserted, thereby improving charging rate characteristics, and excellent cycle life characteristics can be exhibited due to improved initial efficiency and negative electrode processability.

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 is sufficient to form secondary particles, for example, 2 to 30, 2 From 20 to 20, 2 to 10, or 2 to 4 primary particles may come together to form secondary particles. In addition, tertiary particles are formed by assembling secondary particles, and there is no particular limitation as long as the number of secondary particles is sufficient to form tertiary particles, for example, 2 to 20, 2 to 10 or 2 to 4 secondary particles may come together to form tertiary particles.

In one embodiment, the content of graphite may be 9% by weight to 16.5% by weight, 9% by weight to 15% by weight, or 10% by weight to 14.5% by weight based on 100% by weight of the total negative electrode active material. there is. In one embodiment, graphite, for example, artificial graphite, is located on the surface of the primary particles and the surface of the secondary particles, so when the content of graphite is within the above range, the interior of the negative electrode active material is more dense. It can be. The negative active material according to one embodiment includes secondary particles in which the primary particles are assembled and spherical, and tertiary particles in which the secondary particles are assembled, so graphite, for example, can be formed in the space that can be formed between the particles. For example, since artificial graphite is filled, especially at the above content, the space can be more sufficiently filled, and as a result, the interior of the final anode active material can have a dense shape.

In one embodiment, the content of natural graphite may be 78.5% by weight to 89% by weight, 80% by weight to 88.5% by weight, or 80.5% by weight to 88% by weight based on 100% by weight of the total negative electrode active material. there is.

The anode active material according to one embodiment may have an orientation index (O.I.) of 40 to 70, an orientation index of 45 to 70, and an orientation index of 50 to 60. If the orientation index of the anode active material is within the above range, it means that the anode active material is poorly oriented similar to artificial graphite. Accordingly, the anode active material according to one embodiment may exhibit an excellent charging rate similar to artificial graphite.

In one embodiment, the orientation index can be obtained by performing X-ray diffraction analysis using CuKα rays, for example, the peak intensity of the (002) plane relative to the peak intensity of the (110) plane. It can be obtained by the peak intensity ratio (I ₀₀₂ /I ₁₁₀ ).

As such, the negative electrode active material according to one embodiment has the characteristics of high capacity, good pressing properties, and excellent pellet density due to the use of natural graphite, and includes spherical secondary particles assembled from small primary particles, thereby enabling increased lithium insertion. It can have both an improved high charging rate depending on the site and the high charging rate characteristics of artificial graphite. In addition, the effect of improving charge/discharge rate characteristics can also be obtained by including the amorphous carbon coating layer.

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% to 5% by weight based on 100% by weight of the total negative electrode active material.

The anode 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 electrode active material falls within the above range, the internal pore volume of the negative electrode active material and side reactions with the electrolyte solution are reduced, and thus the lifespan characteristics can be improved. In one embodiment, the tap density has a conversion factor of 0.2907 cm ³ /mm, and a process of applying a pressure of 108 N is performed using a Micromeritics GeoPyc 1360 Pycnometer inserted into a chamber with a diameter of 19.1 mm. It can be obtained by performing the test several times and calculating the average value.

The negative electrode active material according to one embodiment may have a mercury cumulative pore volume (Hg Cumulative Pore volume) of 0.01 mL/g to 0.07 mL/g, 0.03 mL/g to 0.07 mL/g, and 0.04 mL/g to 0.04 mL/g. It may be 0.07mL/g. If the accumulated mercury pore volume is within the above range, it means that the pores, or empty space, inside the negative electrode active material are small. The pores measured in the pore volume may have a particle size of 0.01㎛ to 1㎛.

If the accumulated mercury pore volume is within the above range, the content of amorphous carbon within the negative electrode active material is appropriate, so better negative electrode active material efficiency can be obtained. In addition, when the accumulated mercury pore volume is within the above range, the area inside the negative electrode active material that reacts with the electrolyte solution is not excessive, and the electrolyte solution can maintain a density sufficient to be well impregnated, thereby maintaining an appropriate level without excessive side reactions. Lifespan characteristics can be expressed.

In one embodiment, the accumulated mercury pore volume is determined by adding mercury to the negative electrode active material, applying a pressure of 0.1 psi to 60,000 psi, causing the mercury to be injected into the negative electrode active material, and then measuring the change in volume of mercury according to the pressure change. You can get it. The pressure change can be performed by increasing the pressure from 0.1 psi to 0.2 psi to 50,000 psi to 60,000 psi.

The negative electrode active material can be manufactured by the following method. Hereinafter, in order to clearly explain the products obtained in each process, they will be described with reference to FIG. 3, which classifies the materials shown in FIGS. 1 and 1A.

A pulverization granulation process is performed in which natural graphite raw material with a particle diameter of 80㎛ or more is pulverized into primary particles (3 in FIG. 3). The natural graphite raw material can be pulverized into primary particles by applying an air current pulverization method. Air current pulverization can be performed by pulverizing the natural graphite with an air current under the condition of 5 to 20 kg/cm ² at room temperature.

The natural graphite raw material may be flaky natural graphite.

The grinding and granulating process may be carried out so that the particle size of the primary particles is 4㎛ to 8㎛, for example, 4㎛ to 7㎛, 4㎛ to 6㎛, or 5㎛ to 7㎛.

The primary particles are subjected to a spheronization and assembly process using a spheronization equipment to form secondary particles (5 in FIG. 3). The spheronization and assembly process may be performed so that the particle size of the secondary particles is 5㎛ to 10㎛, for example, 6㎛ to 10㎛, 6㎛ to 8㎛, or 7㎛ to 8㎛.

Next, the secondary particles and the first amorphous carbon precursor are mixed to prepare a mixed product. According to this process, the interior of the secondary particles can become more dense.

A second amorphous carbon precursor is added to the obtained mixed product and granulated to produce tertiary particles (7 in FIG. 3). The granulation process can be performed using conventional granulation equipment, but is not limited thereto.

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

The first and second amorphous carbon precursors are converted to crystalline carbon, that is, artificial graphite, in a subsequent heat treatment process. Accordingly, the mixing ratio of the secondary particles and the first and second amorphous carbon precursors is that of artificial graphite in the final product. The content can be adjusted to be 10% by weight to 15% by weight based on 100% by weight of the total negative electrode active material.

According to the above process, the first and second amorphous carbon precursors may be inserted into the secondary particle and located on the surface of the primary particle, and may also be located on the surface of the secondary particle.

The obtained tertiary particles are subjected to primary heat treatment. This primary heat treatment may be performed at a high temperature appropriate for graphitization of the first and second amorphous carbon precursors, for example, at 2,800°C to 3,000°C. The first heat treatment process may be performed for 1 hour to 5 hours, for example, 1 hour to 4 hours, or 1 hour to 3 hours. According to this process, the first and second amorphous carbon precursors may be converted into graphite, for example, artificial graphite. Accordingly, the first and second amorphous carbon precursors located on the surface of the primary particle and the surface of the secondary particle are converted into graphite, for example, artificial graphite, and the artificial graphite may be located.

The obtained first heat treatment product is coated with a third amorphous carbon precursor. The third amorphous carbon precursor is phenol resin, furan resin, epoxy resin, polyacrylonitrile, polyamide resin, polyimide resin, polyamide-imide resin, synthetic pitch, petroleum pitch, coal-based pitch, tar, and combinations thereof. It can be any one selected. The third amorphous carbon precursor and the first and/or second amorphous carbon precursor may be the same or different.

In the 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 electrode active material, is 5 nm to 50 nm, and there is no need to specifically limit it.

The coating product is subjected to secondary heat treatment. The secondary heat treatment process may be performed 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 secondary heat treatment process may be performed for 1 hour to 5 hours, 1 hour to 4 hours, or 1 hour to 3 hours.

Another embodiment provides a lithium secondary battery including a negative electrode, a positive electrode, and a non-aqueous electrolyte.

The 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.

In the negative electrode active material layer, the content of the negative electrode active material may be 95% by weight to 99% by weight based on 100% by weight of the total negative electrode active material layer.

The content of the binder may be 1% to 5% by weight based on 100% by weight of the total binder negative electrode active material layer.

When the negative electrode active material layer further includes a conductive material, the content of the negative electrode active material may be 90% by weight to 99% by weight based on 100% by weight of the total negative electrode active material layer, and the content of the binder and the conductive material may be It may be 1% to 5% by weight, respectively, based on the total 100% by weight.

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

The non-aqueous binders include ethylene propylene copolymer, polyacrylonitrile, polystyrene, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, Polyethylene, polypropylene, polyamidoimide, polyimide, or combinations thereof may be mentioned.

The water-based binders include styrene-butadiene rubber (SBR), acrylated styrene-butadiene rubber (ABR), acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluorine rubber, polymers containing ethylene oxide, and polyvinyl. Pyrrolidone, polypropylene, polyepichlorohydrin, polyphosphazene, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, poly It may be vinyl alcohol or a combination thereof.

When an aqueous binder is used as the negative electrode binder, a cellulose-based compound capable of imparting viscosity may be further included as a thickener. As this cellulose-based compound, one or more types of carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or alkali metal salts thereof can be used. Na, K, or Li can be used as the alkali metal. The amount of the thickener used may be 0.1 to 3 parts by weight based on 100 parts by weight of the negative electrode active material.

The conductive material is used to provide conductivity to the electrode, and in the battery being constructed, any electronically conductive material can be used as long as it does not cause chemical change. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fiber; Metallic substances such as metal powders such as copper, nickel, aluminum, and silver, or metal fibers; Conductive polymers such as polyphenylene derivatives; Alternatively, a conductive material containing a mixture thereof may be used.

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. .

The positive electrode includes a current collector and a positive electrode active material layer formed on the current collector.

As the positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound) can be used. Specifically, one or more types of complex oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof can be used. As a more specific example, a compound represented by any of the following chemical formulas can be used. Li _a A _1-b X _b D ₂ (0.90≤a≤1.8, 0≤b≤0.5); _{Li a} A _{1 - b Li a} E _{1 - b Li a} E _{2 - b} Li _a Ni _{1- bc Co b} Li _a Ni _{1 - bc Co b} Li _a Ni _{1 - bc Co b} Li _a Ni _{1- bc Mn b} Li _a Ni _{1 - bc Mn b} Li _a Ni _{1 - bc Mn b} Li _a Ni _b E _c G _d O ₂ (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 O ₂ (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 O ₂ (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 Mn _d G _e O ₂ (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 O ₂ (0.90≤a≤1.8, 0.001≤b≤0.1); Li _a CoG _b O ₂ (0.90≤a≤1.8, 0.001≤b≤0.1); Li _a Mn _1-b G _b O ₂ (0.90≤a≤1.8, 0.001≤b≤0.1); Li _a Mn ₂ G _b O ₄ (0.90≤a≤1.8, 0.001≤b≤0.1); Li _a Mn _1-g G _g PO ₄ (0.90≤a≤1.8, 0≤g≤0.5); QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiZO ₂ ; LiNiVO ₄ ; Li _(3-f) J ₂ (PO ₄ ) ₃ (0≤f≤2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0≤f≤2); Li _a FePO ₄ (0.90≤a≤1.8)

In the above formula, A is selected from the group consisting of Ni, Co, Mn, and combinations thereof; X is selected from the group consisting of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, and combinations thereof; D is selected from the group consisting of O, F, S, P, and combinations thereof; E is selected from the group consisting of Co, Mn, and combinations thereof; T is selected from the group consisting of F, S, P, and combinations thereof; G is selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof; Q is selected from the group consisting of Ti, Mo, Mn, and combinations thereof; Z is selected from the group consisting of Cr, V, Fe, Sc, Y, and combinations thereof; J is selected from the group consisting of V, Cr, Mn, Co, Ni, Cu, and combinations thereof; L ¹ is selected from the group consisting of Mn, Al, and combinations thereof.

Of course, a compound having a coating layer on the surface can be used, or a mixture of the above compound and a compound having a coating layer can be used. This coating layer may include at least one coating element compound selected from the group consisting of oxides of coating elements, hydroxides of coating elements, oxyhydroxides of coating elements, oxycarbonates of coating elements and hydroxycarbonates of coating elements. You can. The compounds that make up these coating layers may be amorphous or crystalline. 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. For the coating layer formation process, any coating method may be used as long as the above compounds can be coated with these elements in a manner that does not adversely affect the physical properties of the positive electrode active material (e.g., spray coating, dipping method, etc.). Since this is well-understood by people working in the field, detailed explanation will be omitted.

In the positive electrode, the content of the positive electrode active material may be 90% by weight to 98% by weight based on the total weight of the positive electrode active material layer.

In one embodiment, the positive electrode active material layer may further include a binder and a conductive material. At this time, the content of the binder and the conductive material may be 1% to 5% by weight, respectively, based on the total weight of the positive electrode active material layer.

The binder serves to adhere the positive electrode active material particles to each other and also to adhere the positive electrode active material to the current collector. Representative examples of binders include polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, and polyvinylpyrroli. Money, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc. can be used, but are not limited to these. .

The conductive material is used to provide conductivity to the electrode, and in the battery being constructed, any electronically conductive material can be used as long as it does not cause chemical change. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fiber; Metallic substances such as metal powders such as copper, nickel, aluminum, and silver, or metal fibers; Conductive polymers such as polyphenylene derivatives; or a conductive material containing a mixture thereof.

Al may be used as the current collector, but is not limited thereto.

The electrolyte solution includes a non-aqueous organic solvent and lithium salt.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

The non-aqueous organic solvent may be carbonate-based, ester-based, ether-based, ketone-based, alcohol-based, or aprotic solvent.

The carbonate-based solvents include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), and ethylene carbonate ( EC), propylene carbonate (PC), butylene carbonate (BC), etc. can be used. The ester solvents include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, and caprolactone. etc. may be used. As the ether-based solvent, dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, etc. may be used. Additionally, cyclohexanone, etc. may be used as the ketone-based solvent. In addition, the alcohol-based solvent may be ethyl alcohol, isopropyl alcohol, etc., and the aprotic solvent may be R-CN (R is a straight-chain, branched, or ring-shaped hydrocarbon group having 2 to 20 carbon atoms, Nitriles such as (may contain a double bond aromatic ring or ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, sulfolanes, etc. may be used.

The organic solvents can be used alone or in a mixture of one or more, and when using a mixture of more than one, the mixing ratio can be appropriately adjusted according to the desired battery performance, which can be widely understood by those working in the field. there is.

In addition, in the case of the carbonate-based solvent, it is better to use a mixture of cyclic carbonate and chain carbonate. In this case, mixing cyclic carbonate and chain carbonate in a volume ratio of 1:1 to 1:9 may result in superior electrolyte performance.

The organic solvent may further include an aromatic hydrocarbon-based organic solvent in addition to the carbonate-based solvent. At this time, the carbonate-based solvent and the aromatic hydrocarbon-based organic solvent may be mixed at a volume ratio of 1:1 to 30:1.

As the aromatic hydrocarbon-based organic solvent, an aromatic hydrocarbon-based compound of the following formula (1) may be used.

[Formula 1]

(In Formula 1, R ₁ to R ₆ are the same or different from each other 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.)

Specific examples of the aromatic hydrocarbon-based organic solvent include benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, and 1,2,3-tri. Fluorobenzene, 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-trifluor Rotoluene, 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.

In order to improve battery life, the electrolyte may further include vinylethyl carbonate, vinylene carbonate, or an ethylene carbonate-based compound of the following formula (2) as a life-enhancing additive.

[Formula 2]

(In Formula 2, R ₇ and R ₈ 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 (NO ₂ ), and a fluorinated alkyl group having 1 to 5 carbon atoms; , at least one of R ₇ and R ₈ is selected from the group consisting of a halogen group, a cyano group (CN), a nitro group (NO ₂ ), and a fluorinated alkyl group having 1 to 5 carbon atoms, provided that both R ₇ and R ₈ are Not hydrogen.)

Representative examples of the ethylene carbonate-based compounds include difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, or fluoroethylene carbonate. You can. When using more of these life-enhancing additives, the amount used can be adjusted appropriately.

The lithium salt is a substance that is dissolved in an organic solvent and serves 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 anode and the cathode. Representative examples of such lithium salts include LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiN(SO ₂ C ₂ F ₅ ) ₂ , Li(CF ₃ SO ₂ ) ₂ N, LiN(SO ₃ C ₂ F ₅ ) ₂ , Li(FSO ₂ ) ₂ N (lithium bis(fluorosulfonyl)imide: LiFSI), LiC ₄ F ₉ SO ₃ , LiClO ₄ , LiAlO ₂ , LiAlCl ₄ , LiPO ₂ F ₂ , LiN( _{C ​ ​ ​ ​ ​} difluoro(bisoxolato) phosphate), LiCl, LiI, LiB(C ₂ O ₄ ) ₂ (with lithium bis(oxalato) borate (LiBOB) and lithium difluoro(oxalato)borate (LiDFOB) If the concentration of the lithium salt is within the range of 0.1M to 2.0M, the electrolyte is suitable. Because it has good conductivity and viscosity, it can exhibit excellent electrolyte performance and allows lithium ions to move effectively.

Depending on the type of lithium secondary battery, a separator may exist between the positive and negative electrodes. Such separators may be polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof, such as a polyethylene/polypropylene two-layer separator, a polyethylene/polypropylene/polyethylene three-layer separator, or a polypropylene/polyethylene/poly layer. Of course, a mixed multilayer film such as a propylene three-layer separator can be used.

Figure 4 shows an exploded perspective view of a lithium secondary battery according to an embodiment of the present invention. Although the lithium secondary battery according to one embodiment is described as an example of a prismatic shape, the present invention is not limited thereto and can be applied to batteries of various shapes, such as cylindrical and pouch types.

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

Hereinafter, examples and comparative examples of the present invention will be described. However, the following example is only an example of the present invention, and the present invention is not limited to the following example.

(Example 1)

Small primary particles were prepared by pulverizing flaky natural graphite raw material with a particle diameter of 80㎛ to 120㎛. The small primary particles were subjected to a spheronization and assembly process using a spheronization equipment to produce secondary particles. A mixed product was prepared by mixing the secondary particles and the first pitch carbon.

Subsequently, the second pitch carbon was added to the mixed product and granulated to prepare tertiary particles.

The prepared tertiary particles were first heat treated at 2,800°C for 2 hours. In this heat treatment process, the first and second pitch carbons were graphitized and existed as artificial graphite on the surfaces of the primary particles and the secondary particles.

The obtained heat-treated product was coated with third pitch carbon and heat-treated at 1,200°C for 2 hours to prepare a negative electrode active material.

The manufactured negative electrode active material includes secondary particles in which primary particles are assembled and spherical, natural graphite as tertiary particles in which the secondary particles are assembled, artificial graphite located on the surface of the primary particles and the surface of the secondary particles. And, it included a soft carbon coating layer surrounding the surface of the tertiary particle.

In the manufacturing process, the amount of the tertiary particles, the first pitch carbon, the second pitch carbon, and the third pitch carbon used is such that, in the manufactured negative electrode active material, the content of the natural graphite is 100% by weight of the total negative electrode active material. It was adjusted to 87% by weight, the content of the artificial graphite was 10% by weight, and the content of the soft carbon coating layer was 3% by weight.

The average particle diameter (D50) of the manufactured primary particles, average particle diameter (D50) and tertiary particles (D50), average particle diameter (D50) and tap density of the anode active material are shown in Table 1 below. .

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

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 negative electrode active material slurry on a Cu foil current collector.

The cathode. A coin-type half cell was manufactured using a lithium metal counter electrode and electrolyte. The electrolyte used was ethylene carbonate, ethylmethyl carbonate, and dimethyl carbonate (20:10:70 volume ratio) in which 1.5M LiPF ₆ was dissolved.

(Examples 2 to 6)

The 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), and tap density were changed as shown in Table 1 below. In addition, the amounts of the tertiary particles, the first pitch carbon, and the second pitch carbon, the content of natural graphite, the content of artificial graphite, and the content of the soft carbon coating layer in the manufactured negative electrode active material are shown in Table 2. A negative electrode and a half cell were manufactured in the same manner as in Example 1, except that the content was adjusted to obtain a negative electrode.

(Comparative Example 1)

Small primary particles were prepared by pulverizing flaky natural graphite raw material with a particle diameter of 80㎛ to 120㎛. The small primary particles were subjected to a spheronization and assembly process using a spheronization equipment to produce secondary particles.

Pitch carbon was added to the secondary particles and heat treated at 1,200°C for 2 hours to prepare a negative electrode active material with a soft carbon coating layer formed on the surface of the secondary particles.

The amount of the secondary particles and the pitch carbon used is such that, in the manufactured negative electrode active material, the content of secondary particle natural graphite is 93% by weight and the content of the soft carbon coating layer is 7% by weight based on 100% by weight of the total negative electrode active material. Adjusted.

The average particle diameter (D50) of the produced primary particles, the average particle diameter (D50) of the secondary particles, and the average particle diameter (D50) and tap density of the anode active material are shown in Table 1 below.

Using the negative electrode active material, a negative electrode and a half battery were manufactured in the same manner as in Example 1.

(Comparative Example 2)

A flaky natural graphite raw material with a particle diameter of 80㎛ to 120㎛ was spheronized using a spheronizing equipment, and subjected to secondary heat treatment at 1,200°C for 2 hours to prepare a negative electrode active material.

The average particle diameter (D50) and tap density of the manufactured active materials are shown in Table 1 below.

Using the negative electrode active material, a negative electrode and a half battery were manufactured in the same manner as in Example 1.

(Comparative Example 3)

A negative electrode and a half cell were manufactured in the same manner as Comparative Example 2, except that the average particle diameter (D50) and tap density of the negative electrode active material were changed as shown in Table 1 below.

(Comparative Example 4)

Petroleum coke was pulverized into small primary particles. These small primary particles were subjected to an assembly process to produce secondary particles.

The secondary particles were heat treated at 3,000°C for 2 hours to produce artificial graphite.

A negative electrode active material was manufactured in the same manner as Comparative Example 2, except that the artificial graphite was used.

The average particle diameter (D50) and tap density of the prepared primary particles, secondary particles, and negative electrode active materials are shown in Table 1 below.

Using the negative electrode active material, a negative electrode and a half battery were manufactured in the same manner as in Example 1.

(Comparative Examples 5 and 6)

A negative electrode and a half cell were manufactured in the same manner as in Comparative Example 4, except that the average particle diameter (D50) and tap density of the primary particles, secondary particles, and negative electrode active material were changed as shown in Table 1 below.

(Comparative Example 7)

A negative electrode active material was prepared in the same manner as in Comparative Example 2, except that a mixture of natural flaky graphite and artificial graphite (50:50 weight ratio) was used instead of natural flaky graphite.

The average particle diameter (D50) and tap density of the manufactured active materials are shown in Table 1 below.

Using the negative electrode active material, a negative electrode and a half battery were manufactured in the same manner as in Example 1.

Experimental Example 1) Pellet density measurement

1 g of the negative electrode active material prepared according to Examples 1 to 6 and Comparative Examples 1 to 7 was placed in a mold and held for 30 seconds under a 2 ton pressure (press force) to prepare pellets, and the pellet density of the produced pellets was calculated. ) was measured, and the results are shown in Table 1 below.

Since the negative electrode active materials of Comparative Examples 2, 3, and 7 were not in the form of secondary particles in which primary particles were assembled, only the average particle diameter of the negative electrode active materials is shown in Table 1 below.

Average particle size of primary particles
(D50, ㎛) Average particle diameter of secondary particles
(D50, ㎛) Average particle size of tertiary particles
(D50, ㎛) Average particle size of negative electrode active material
(D50, ㎛) Pellet density
(g/cc) tap density
(g/cc) Example 1 4.9 6.1 10.4 10.5 1.66 1.04 Example 2 5.0 6.5 11.2 11.4 1.66 1.07 Example 3 5.7 6.8 11.4 11.5 1.63 1.11 Example 4 6.0 7.5 13.2 13.3 1.62 1.10 Example 5 6.8 9.0 14.8 15 1.60 1.12 Example 6 4.2 6.0 9.6 9.7 1.68 1.04 Comparative Example 1 14.5 15.9 16 1.78 1.20 Comparative Example 2 - - - 11 1.63 1.10 Comparative Example 3 - - - 17 1.77 1.14 Comparative Example 4 10.1 12.7 13 1.54 1.03 Comparative Example 5 11.4 13.3 13.5 1.48 1.04 Comparative Example 6 9.8 10.9 11 1.50 1.01 Comparative Example 7 - - - 13 1.60 1.09

Natural graphite content
(weight%) Artificial graphite content
(weight%) Soft carbon coating layer content
(weight%) Example 1 87 10 3 Example 2 85.5 11.5 3 Example 3 83.5 13.5 3 Example 4 83 14 3 Example 5 83.5 14.5 2 Example 6 85 11 4

Experimental Example 2) SEM measurement

SEM images of the negative electrode active materials prepared according to Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 4 are shown in FIGS. 5 to 8, respectively. In Figures 5 and 6, (a) is a SEM photograph at 3,000 magnification, and (b) is an SEM photograph at 1,000 magnification. As shown in Figure 5, the negative electrode active material manufactured according to Example 1 clearly shows an assembled form of particles measuring about 6㎛, showing a similar form to the artificial graphite of Comparative Example 4 shown in Figure 8. . On the other hand, as shown in FIG. 6, the assembly form of the negative electrode active material of Comparative Example 1 is not clear, and it can be seen that it has a similar form to the natural graphite of Comparative Example 2 shown in FIG. 7.

Experimental Example 3) X-ray diffraction analysis evaluation

X-ray diffraction analysis using CuKα rays was performed on the negative electrode active materials prepared according to Examples 1 to 6 and Comparative Examples 1 to 7.

X-ray diffraction analysis was performed using X'Pert (PANalytical) XRD equipment and removing the monochromator equipment to improve peak intensity resolution. At this time, the measurement conditions were 2θ = 20° to 80°, scan speed (°/s) = 0.06436, and step size was 0.026°/step.

From these results, the interplanar distance (d002) of the diffraction peak of the (002) plane, the I (002) peak intensity value, and the I (110) peak intensity value were obtained. In addition, the orientation index of I(002)/I(110) was obtained, and the results are shown in Table 3 below as O.I. In addition, the interplanar distance (d002) is shown in Table 3 below.

Experimental Example 3) Evaluation of mercury cumulative pore volume

The cumulative pore volume of mercury in the negative electrodes prepared according to Examples 1 to 6 and Comparative Examples 1 to 7 was calculated by adding mercury to the negative electrode active material and applying a pressure of 0.1 psi to cause mercury to be injected into the negative electrode active material. Then, the pressure was increased to 60,000 psi, and at this time, the change in mercury volume was measured, and the results are shown in the mercury pore volume in Table 3 below. The pores measured in the pore volume had a particle size of 0.01㎛ to 1㎛.

Experimental Example 4) Capacity evaluation

The half-cells manufactured according to Examples 1 to 6 and Comparative Examples 1 to 7 were charged at 0.2C, and the charging capacity was measured. The results are shown in Table 3 below.

Experimental Example 5) Evaluation of charging rate characteristics

The half-cells manufactured according to Examples 1 to 6 and Comparative Examples 1 to 7 were charged and discharged once at 0.2C and once at 2C.

The ratio of 2C charging capacity to 0.2C charging capacity was calculated, and the results are shown in Table 3 below as charging rate characteristics.

Experimental Example 6) Direct current internal resistance (DC-IR) evaluation

The half-cells manufactured according to Examples 1 to 6 and Comparative Examples 1 to 7 were charged at 25°C at constant current/constant voltage under 0.2C, 0.01V, 0.01C cut-off conditions, rested for 10 minutes, and then charged at constant current. Discharge at 0.2C, 1.5V cut-off conditions, charging and discharging once with 10-minute rest, SOC50 (when the total battery charge capacity is set to 100%, charge to reach 50% charge capacity) The voltage drop (V) that occurs while flowing a current at 8C for 10 seconds was measured in a state of discharging (which means 50% discharge when viewed in a discharging state). The resistance value was obtained from the measured voltage and the applied current (8C), and the result was expressed as direct current internal resistance (DC-IR). The results are shown in Table 3 below.

The average particle diameter (D50) of the negative electrode active material is also shown in Table 3 below.

Average particle diameter of anode active material (D50, ㎛) O.I. Mercury pore volume (mL/g) d002
(Å) Volume
(mAh/g) charge rate
(%) DC-IR
(Ω) Example 1 10.5 52 0.065 3.356 361 48.0 6.3 Example 2 11.4 54 0.066 3.356 358 47.5 6.4 Example 3 11.5 55 0.052 3.357 357 47.5 6.4 Example 4 13.3 61 0.041 3.358 356 46.4 6.6 Example 5 15 62 0.051 3.356 358 45.2 6.9 Example 6 9.7 52 0.062 3.356 357 47.7 6.3 Comparative Example 1 16 60 0.079 3.358 355 40 7.8 Comparative Example 2 11 94 0.081 3.355 356 35 7.8 Comparative Example 3 17 150 0.097 3.354 359 24 8.2 Comparative Example 4 13 53 0.014 3.360 346 44.1 7.1 Comparative Example 5 13.5 72 0.022 3.359 346 44.6 7.0 Comparative Example 6 11 70 0.016 3.361 343 45 6.9 Comparative Example 7 13 79 0.050 3.357 345 37.1 7.2

As shown in Table 3, the high-rate charging characteristics of the batteries containing the negative electrode active materials of Examples 1 to 6 were superior to those of Comparative Examples 1 to 7, and the DC-IR resistance was lower than that of Comparative Examples 1 to 5 and 7. You can. In the case of Comparative Example 6, the DC-IR resistance is the same as Example 5, but the charging rate is somewhat low and the capacity is very low, so it is not appropriate.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and can be implemented with various modifications within the scope of the claims, the detailed description of the invention, and the accompanying drawings, and this can also be done with various modifications. It is natural that it falls within the scope of the invention.

Claims (16)

Tertiary particles including graphite and an assembly of secondary particles obtained by assembling and sphericalizing a plurality of primary particles; and

It includes an amorphous carbon coating layer surrounding the tertiary particles,
The primary particle and the secondary particle are natural graphite, a negative electrode active material for a lithium secondary battery. According to paragraph 1,
The graphite is an anode active material for a lithium secondary battery, which is artificial graphite. According to paragraph 1,
The graphite is a negative electrode active material for a lithium secondary battery, which is located on the surface of the primary particles and the surface of the secondary particles. According to paragraph 1,
The natural graphite is a negative electrode active material for a lithium secondary battery, which is flaky natural graphite. According to paragraph 1,
A negative electrode active material for a lithium secondary battery wherein the content of graphite is 9% to 16.5% by weight based on 100% by weight of the total negative electrode active material. According to paragraph 1,
A negative electrode active material for a lithium secondary battery in which the content of natural graphite is 78.5% by weight to 89% by weight based on 100% by weight of the total negative electrode active material. According to paragraph 1,
The primary particle is a negative electrode active material for a lithium secondary battery having a particle diameter of 4㎛ to 8㎛. According to paragraph 1,
The secondary particle is a negative electrode active material for a lithium secondary battery having a particle diameter of 5㎛ to 10㎛. According to paragraph 1,
The tertiary particles are a negative electrode active material for a lithium secondary battery having a particle diameter of 9㎛ to 15㎛. According to paragraph 1,
The negative electrode active material is a negative electrode active material for a lithium secondary battery having a particle diameter of 9.05㎛ to 16㎛. According to paragraph 1,
The coating layer is a negative electrode active material for a lithium secondary battery having a thickness of 5 nm to 50 nm. According to paragraph 1,
The negative electrode active material is a negative electrode active material for a lithium secondary battery having a tap density of 0.8 g/cc to 1.1 g/c. According to paragraph 1,
The negative electrode active material is a negative electrode active material for a lithium secondary battery having an orientation index of 40 to 70. According to paragraph 1,
The negative electrode active material is a negative electrode active material for a lithium secondary battery having a mercury cumulative pore volume of 0.01 mL/g to 0.07 mL/g. According to paragraph 1,
The amorphous carbon is any one selected from soft carbon, hard carbon, mesophase pitch carbide, calcined coke, and mixtures thereof. A negative electrode containing the negative electrode active material of any one of claims 1 to 15;
anode; and
containing electrolytes
Lithium secondary battery.