KR102209653B1 - Anode with improved swelling phenomenon and Lithium secondary battery comprising the anode - Google Patents

Abstract

In the present invention, the negative electrode active material is composed of fine-grained artificial graphite particles having a D50 average particle diameter in the range of 5 μm to 10 μm and granulated artificial graphite particles having a D50 average particle diameter of 15 μm to 25 μm, The fine artificial graphite particles are included in an amount of 5 to 70 parts by weight based on 100 parts by weight of the fine artificial graphite particles and the granulated artificial graphite particles, and the negative electrode has a (004)/(110) orientation in the range of 15 to 25 A negative electrode is provided, which achieves a high energy density of the electrode and solves the swelling phenomenon of the electrode thickness.

Description

Anode with improved swelling phenomenon and Lithium secondary battery comprising the anode}

The present invention relates to a negative electrode with improved swelling and a lithium secondary battery including the same.

In the mobile battery market, lithium secondary battery cells with an energy density of 700 Wh/L are being developed, and the energy density is aiming for a road map that increases by 30 to 50 Wh/L every year. For this, the cathode is required to have a higher density per volume of 1.6 g/cc or more. However, in the case of densifying the negative electrode as described above in the current technology, a swelling phenomenon occurs in which the electrode thickness increases, and as a result, the energy density of the battery decreases.

Meanwhile, various types of carbon-based materials including artificial graphite, natural graphite, or hard carbon capable of intercalating/deintercalating lithium have been applied as negative active materials of lithium secondary batteries. Graphite has a low discharge voltage of 0.2V compared to lithium, and a battery using graphite as a negative active material exhibits a high discharge voltage of 3.6V, providing an advantage in terms of energy density of a lithium secondary battery. In addition, the excellent reversibility guarantees a long life of a rechargeable lithium battery, which is the most widely used.

Among them, artificial graphite has the advantage of high charging/discharging efficiency and excellent life characteristics. Artificial graphite has a shape such as a plate shape, a spherical shape, a fibrous shape, and a block shape, and the surface layer of the particles is in a state close to an amorphous state that is not graphitized. The surface layer of the particles close to the amorphous material exhibits little electrostatic repulsion between particles peculiar to the graphite layered structure, and thus lacks slip properties. Therefore, there is a problem in that the orientation is not well performed because the rolling is not performed well and the change in shape is small. In addition, there is a disadvantage in that the cost is not only expensive, but also the dispersibility in the aqueous slurry is very low, and thus it is difficult in terms of processability, and the capacity is low, making it difficult to obtain a desired level of physical properties of the battery.

On the other hand, natural graphite has high utility as a negative electrode active material because it is inexpensive and exhibits electrochemical properties similar to artificial graphite. However, since natural graphite has a plate shape, the surface area is large and the edges are exposed as it is, and when applied as a negative electrode active material, penetration of the electrolyte or decomposition reaction occurs. Because of this, the edge portion is peeled off or destroyed, causing a large irreversible reaction, and when it is manufactured as an electrode plate, the graphite active material is flatly pressed and oriented on the current collector, so impregnation of the electrolyte solution is not easy, and thus charging/discharging characteristics may deteriorate.

Accordingly, in the present invention, the advantage of artificial graphite is solved and the capacity problem is solved to use it as a negative electrode active material, and an energy density is increased to provide a negative electrode.

In addition, in the present invention, it is intended to provide a negative electrode having no or minimal electrode swelling problem during charging.

In addition, the present invention provides a lithium secondary battery having an increased capacity including the negative electrode.

According to an aspect of the present invention, in the negative electrode for a lithium secondary battery, the negative electrode active material constituting the negative electrode comprises fine artificial graphite particles having a D50 average particle diameter in the range of 5 µm to 10 µm and a D50 of 15 µm to 25 µm. It is made of granulated artificial graphite particles having an average particle diameter, and the fine artificial graphite particles are included in an amount of 5 to 70% by weight based on the total weight of the fine artificial graphite particles and the granulated artificial graphite particles, and the negative electrode is There is provided a negative electrode for a lithium secondary battery, characterized in that it has a (004) / (110) orientation in the range of 15 to 25.

The fine artificial graphite particles may have a (004)/(110) orientation in the range of 3 to 20, and the granulated artificial graphite particles may have a (004)/(110) orientation in the range of 5 to 20.

Both the granulated artificial graphite particles and the fine artificial graphite particles may have a plate shape.

The negative electrode for a lithium secondary battery may contain fine artificial graphite particles having an average diameter of 3 to 5 µm D50 as a conductive material.

According to another aspect of the present invention, there is provided a lithium secondary battery including the negative electrode described above.

The negative electrode active material according to an embodiment of the present invention includes both granulated artificial graphite and fine artificial graphite having different average particle diameters in a specific composition ratio, thereby providing a negative electrode with satisfactory energy density and improved swelling phenomenon. do.

In addition, a lithium secondary battery having an increased capacity including the negative active material is provided.

The following drawings attached to the present specification illustrate preferred embodiments of the present invention, and serve to further understand the technical idea of the present invention together with the content of the above-described invention, so the present invention is limited to the matters described in such drawings. It is limited and should not be interpreted.
1 is a SEM photograph of granulated artificial graphite particles.
2 is a SEM photograph of a mixture obtained by mixing granulated artificial graphite particles and fine artificial graphite particles at a weight ratio of 40:60 according to an embodiment of the present invention.
3 is a diagram schematically showing an embodiment in which granulated artificial graphite particles and fine artificial graphite particles are mixed according to an embodiment of the present invention.
4 is a graph showing the particle size distribution of an active material of the negative electrode in Example 1-1 and Comparative Example 1-1.
5 is a graph showing the (004)/(110) orientation of the negative electrodes of Example 1-1 and Comparative Example 1-1.

Hereinafter, the present invention will be described in more detail to aid understanding of the present invention.

The terms or words used in the specification and claims should not be construed as being limited to their usual or dictionary meanings, and the inventor may appropriately define the concept of terms in order to describe his own invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

The negative electrode active material according to an embodiment of the present invention is fine-grained artificial graphite particles having a D50 average particle diameter in the range of 5 μm to 10 μm, and granulated artificial graphite particles having a D50 average particle diameter of 15 μm to 25 μm. And the fine artificial graphite particles are included in an amount of 5 to 70% by weight based on the total weight of the fine artificial graphite particles and the granulated artificial graphite particles, and the negative electrode has a (004)/(110) orientation in the range of 15 to 25 It characterized in that it has. In the present specification, the (004)/(110) orientation of the negative electrode refers to a value measured when the negative active material has a density of 1.68 g/cc by applying only a minimum packing pressure after loading the negative active material in a particle state.

More specifically, the fine artificial graphite particles are in an amount of 5% to 70% by weight, preferably 10% to 70% by weight, more preferably 20% to 70% by weight based on the total weight of the artificial graphite particles Can be included as When the amount of the fine artificial graphite particles is less than 5% by weight, there is no or insignificant effect of improving the swelling phenomenon, and when it exceeds 70% by weight, the specific surface area of the negative electrode active material increases, thereby increasing side reactions and increasing energy density. It doesn't make sense.

The fine artificial graphite particles may have a low (004)/(110) orientation. Preferably, the degree of orientation may be in the range of 3 to 20, more preferably in the range of 5 to 20 at a compressive density of 1.40 g/cc to 1.85 g/cc. If the orientation degree (I ₀₀₄ /I ₁₁₀ ) is larger than the above range, the electrode swelling phenomenon becomes severe during battery charging, it is difficult to increase the battery capacity per unit volume of the electrode, and the active material is removed due to expansion and contraction during the cycle test. Due to this, the cycle characteristics are liable to deteriorate. On the other hand, when the orientation degree (I ₀₀₄ /I ₁₁₀ ) is smaller than the above range, it becomes difficult to increase the packing density of the electrode after pressing. In the specification of the present application, the degree of orientation (I ₀₀₄ /I ₁₁₀ ) is an index indicating the degree of orientation of the hexagonal network of graphite crystals in the thickness direction of the electrode. The larger the degree of orientation (I ₀₀₄ /I ₁₁₀ ), the more the directions of the hexagonal surface of the graphite crystals of the particles are not aligned. This degree of orientation can be determined using JCPDS (ASTM) data as standard data by X-ray diffraction or the like as an index. More specifically, the area ratio ((004)/(110) obtained by integrating the peak intensities of the (110) and (004) planes after measuring the (110) and (004) planes of the negative active material included in the negative electrode by XRD )), and more specifically, XRD measurement conditions are as follows.

-Target: Cu (Kα-ray) graphite monochromator

-Slit: diverging slit = 1 degree, receiving slit = 0.1 mm, scattering slit = 1 degree

-Measurement area and step angle/measurement time:

(110) plane: 76.5 degrees <2θ <78.5 degrees, 0.01 degrees / 3 seconds

(004) plane: 53.5 degrees <2θ <56.0 degrees, 0.01 degrees / 3 seconds,

In the above, 2θ represents the diffraction angle.

The XRD measurement is an example, and other measurement methods may also be used.

The fine artificial graphite particles may have a value of d(002) in the range of 0.3354 to 0.3360 by X-ray diffraction analysis. If d(002) is too large, the crystallinity is insufficient, the charge/discharge capacity is lowered, and the strength of the graphite particles is too high. Therefore, when pressing the active material layer applied to the current collector to a predetermined bulk density, high pressure It can be difficult to densify because of the need.

In addition, it is preferable that the fine artificial graphite particles have a crystal thickness of L _c (002) in the range of 50 to 100 nm by X-ray diffraction analysis. If L _c (002) is less than 50 nm, the crystallinity as graphite is insufficient, the charge/discharge capacity decreases, and the strength of the graphite particles is too high, so that the active material layer applied to the current collector is pressed to a predetermined bulk density. There is a fear that high pressure is required during molding, making it difficult to increase the density. In addition, when L _c (002) is greater than 100 nm, electrode swelling may become severe.

In addition, the average particle diameter (D50) of the granulated artificial graphite particles may be 15 µm to 25 µm, preferably 17 µm to 23 µm. If the average particle diameter of the granulated artificial graphite particles is less than 15 μm, the difference in size from the fine artificial graphite particles may be small, so that the effect of improving the conductivity by mixing of dissimilar particles may be insignificant. When the average particle diameter of the granulated artificial graphite particles exceeds 25 μm, There may be a problem of deterioration of rate characteristics and a problem of deterioration of tap density due to an excessive particle size of.

In the present invention, the average particle diameter of the particles can be defined as the particle diameter based on 50% of the particle diameter distribution. The average particle diameter (D50) of the particles according to an embodiment of the present invention may be measured using, for example, a laser diffraction method. In general, the laser diffraction method can measure a particle diameter of about several mm from a submicron region, and high reproducibility and high resolution results can be obtained.

The granulated artificial graphite particles may have a value of d(002) in the range of 0.3354 to 0.3360 by X-ray diffraction analysis. If d(002) is too large, the crystallinity is insufficient, the charge/discharge capacity is lowered, and the strength of the graphite particles is too high. Therefore, when pressing the active material layer applied to the current collector to a predetermined bulk density, high pressure There is a fear that it becomes difficult to increase the density due to the need.

In addition, it is preferable that the granulated artificial graphite particles have a crystal thickness of L _c (002) in the range of 50 to 100 nm by X-ray diffraction analysis. If L _c (002) is less than 50 nm, the crystallinity as graphite is insufficient, the charge/discharge capacity decreases, and the strength of the graphite particles is too high, so that the active material layer applied to the current collector is pressed to a predetermined bulk density. There is a fear that high pressure is required during molding, making it difficult to increase the density.

The fine artificial graphite particles and the granulated artificial graphite particles are mixed to form an active material, and thus may have a (004)/(110) orientation in the range of 15 to 25. In this case, as shown in FIG. 3, the active material may constitute an active material in a manner in which the granulated artificial graphite particles 100 and the fine artificial graphite particles 200 are mixed. Accordingly, it is possible to maximize the loading amount per unit area while improving electrode swelling during charging.

On the other hand, the negative electrode using only fine artificial graphite particles having a D50 average diameter of 5 to 10 μm as an active material has a negative orientation degree in the range of 10 to 20 after loading and packing at a density of 1.68 g/cc, and 15 to 25 μm as an active material In the negative electrode using only granulated artificial graphite particles having an average diameter of D50, after loading and packing at a density of 1.68 g/cc, the negative electrode orientation degree ranged from 25 to 30, and as a result, the negative electrode orientation degree was different from the present invention. It acts as a factor in which swelling occurs remarkably. In FIG. 5, the (004)/(110) orientation degree of the active material according to an embodiment of the present invention and the (004)/(100) orientation degree of the granulated artificial graphite particles are compared.

According to an embodiment of the present invention, when the fine artificial graphite particles and the granulated artificial graphite particles have the above-described average particle diameter, the fine artificial graphite particles may be uniformly distributed between the granulated artificial graphite particles. Accordingly, the loading of the active material per unit area of the electrode can be increased, and the contact between the active materials is improved during the charging and discharging process, so that a short circuit problem due to volume expansion can be solved.

The granulated artificial graphite particles and fine artificial graphite particles may each independently be amorphous, scale-shaped, square, plate-shaped, spherical, fibrous, point-shaped, or a mixture thereof. Specifically, the shape of the fine artificial graphite particles may be, for example, a spherical shape, a square shape, a scale shape, a plate shape, a point shape, or a mixture thereof, and more preferably a spherical shape, a point shape, a scale shape, or a mixture thereof. have. In addition, the shape of the granulated artificial graphite particles may be, for example, amorphous, scale, plate, fibrous, spherical, or a mixture thereof, and more preferably spherical, scale, plate, or a mixture thereof. I can.

In addition to the granulated artificial graphite particles and fine artificial graphite particles, an aspect of using negative active materials such as natural graphite and silicon together was also examined, but negative active materials such as natural graphite and silicon have too much swelling compared to artificial graphite. It is large, and even if small particles are used, no significant effect of reducing swelling occurs. In addition, since low crystalline carbon has a low capacity and does not have excellent rollability, it may not conform to the purpose of the present invention to reduce swelling for high energy density.

Meanwhile, the method of manufacturing the negative active material according to an embodiment of the present invention may include mixing granulated artificial graphite particles and fine artificial graphite particles. In the method of manufacturing the negative active material of the present invention, the mixing method for preparing the negative active material may be mixed by simple mixing or mechanical milling using a conventional method known in the art. For example, a carbon composite may be formed by simply mixing using a mortar or by mechanically applying a compressive stress by rotating at a rotation speed of 100 to 1000 rpm using a blade or a ball mill. On the other hand, since the tap density is increased by the use of fine artificial graphite particles, there is an effect of increasing the adhesive force due to an increase in contact points between active materials.

In addition, the present invention provides a negative electrode including the negative active material.

Further, the present invention provides a lithium secondary battery comprising a positive electrode, the negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte in which a lithium salt is dissolved.

The negative electrode active material prepared above may be prepared by a method commonly used in the art. For example, a slurry may be prepared by mixing and stirring a binder and a solvent, and a conductive material and a dispersant as necessary in the negative electrode active material according to an embodiment of the present invention, and then coating it on a current collector and compressing it to prepare a negative electrode. .

As the binder, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidenefluoride, polyacrylonitrile, polymethylmethacrylate, Polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), Various kinds of binder polymers such as sulfonated EPDM, styrene butadiene rubber (SBR), fluorine rubber, polyacrylic acid and polymers in which hydrogens thereof are substituted with Li, Na or Ca, or various copolymers can be used. have. As the solvent, N-methylpyrrolidone, acetone, water, and the like may be used.

The conductive material is not particularly limited as long as it has conductivity without causing chemical changes to the battery, and examples thereof include graphite such as natural graphite or artificial graphite; Carbon blacks such as carbon black, acetylene black, Ketjen black, channel black, Parnes black, lamp black, and thermal black; Conductive fibers such as carbon fibers and metal fibers; Conductive tubes such as carbon nanotubes; Metal powders such as fluorocarbon, aluminum, and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

In particular, in the present invention, since fine artificial graphite particles having a diameter of 5 to 10 μm are mixed and used, the tap density is increased and the contact point is increased. Accordingly, when fine artificial graphite particles having a diameter of 3 to 5 µm are used together, the fine artificial graphite particles having an average diameter of 3 to 5 µm D50 can act as a conductive material and have an effect of improving high-temperature storage performance. Will have.

The dispersant may be an aqueous dispersant or an organic dispersant such as N-methyl-2-pyrrolidone, or an organic solvent.

As in the above-described negative electrode manufacturing, a slurry is prepared by mixing a positive electrode active material, a conductive material, a binder, and a solvent, and then directly coated on a metal current collector, or cast on a separate support, and a positive electrode active material film separated from the support A positive electrode can be manufactured by laminating the current collector.

The positive electrode active material is lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), Li[Ni _x Co _y Mn _z M _v ]O ₂ (wherein M is selected from the group consisting of Al, Ga, and In. Any one or two or more of these elements; 0.3≦x<1.0, 0≦y, z≦0.5, 0≦v≦0.1, x+y+z+v=1), Li(Li _a M _{ba- b 'M' b ') O} 2 - c a c ( wherein, 0≤a≤0.2, 0.6≤b≤1, 0≤b'≤0.2, 0≤c≤0.2 and; M is Mn and, Ni, It includes at least one selected from the group consisting of Co, Fe, Cr, V, Cu, Zn, and Ti; M'is at least one selected from the group consisting of Al, Mg, and B, and A is P, F , S and N are at least one selected from the group consisting of.), etc. layered compounds or compounds substituted with one or more transition metals; Formula _{Li 1 + y Mn 2 - y} O 4 ( where, y is 0 - 0.33), LiMnO _3, the lithium manganese oxide such as LiMn ₂ O _3, LiMnO _2; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ , and Cu ₂ V ₂ O ₇ ; Formula _{LiNi 1 - y M y O 2} ( where, the M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, y = 0.01 - 0.3 Im) Ni site type lithium nickel oxide which is represented by; Formula _{LiMn 2 - y M y O 2} ( where, M = Co, Ni, Fe , Cr, and Zn, or Ta, y = 0.01 - 0.1 Im) or Li ₂ Mn ₃ MO ₈ (where, M = Fe, Co, A lithium manganese composite oxide represented by Ni, Cu, or Zn); LiMn ₂ O _{4 in} which part of Li in the formula is substituted with alkaline earth metal ions; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ and the like may be mentioned, but the present invention is not limited thereto.

The separator is a conventional porous polymer film used as a conventional separator, for example, a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene/butene copolymer, an ethylene/hexene copolymer, and an ethylene/methacrylate copolymer. The prepared porous polymer film can be used alone or by stacking them, and a conventional porous non-woven fabric, for example, a non-woven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, etc., coating ceramic on at least one side of the polymer separator substrate It can be used, but is not limited thereto.

In the electrolytic solution for use in one embodiment of the present invention, a lithium salt which can be included in the electrolyte may be used without limitation, if the ones commonly used in the secondary battery, the electrolytic solution, for example, as the lithium salt, the anion is F ^{-, _{Cl -, I -, NO 3}} -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF 4 -, (CF 3) 3 PF 3 -, (CF 3 ^{_{) 4 PF 2 -, (CF}} 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2) 2 N -, (FSO 2) _{^{2 N -, CF 3 CF 2}} (CF 3) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C -, (CF 3 SO 2) 3 C -, CF 3 (CF 2) _{^{7 SO 3 -, CF 3 CO}} 2 -, CH 3 CO 2 -, SCN - may be used one selected from the group consisting of ^- and _{(CF 3 CF 2 SO 2)} 2 N.

In the electrolytic solution used in an embodiment of the present invention, organic solvents included in the electrolytic solution may be used without limitation, as long as they are commonly used, and typically propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethylmethyl Carbonate, methylpropyl carbonate, dipropyl carbonate, fluoro-ethylene carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, gamma-butyrolactone, propylene Sulfite, tetrahydrofuran, methyl formate, methyl acetate, ethyl acetate, isopropyl acetate, isoamyl acetate, methyl propionate ( methyl propionate), ethyl propionate, propyl propionate, butyl propionate, methyl butylate and ethyl butylate Any one selected or a mixture of two or more of them may be used.

In particular, among the carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are highly viscous organic solvents and can be preferably used because they dissociate lithium salts in the electrolyte well due to their high dielectric constant. These cyclic carbonates include dimethyl carbonate and diethyl When a low viscosity, low dielectric constant linear carbonate such as carbonate is mixed and used in an appropriate ratio, an electrolyte solution having a high electrical conductivity can be prepared, and thus it can be more preferably used.

Optionally, the electrolytic solution stored according to the present invention may further include an additive such as an overcharge preventing agent included in a conventional electrolytic solution.

A separator is disposed between the positive electrode and the negative electrode to form an electrode assembly, and the electrode assembly is placed in a cylindrical battery case, a prismatic battery case, or an aluminum pouch, and then an electrolyte is injected to complete a secondary battery. Alternatively, a lithium secondary battery is completed by laminating the electrode assembly, impregnating it in an electrolyte solution, and sealing the obtained resultant in a battery case.

The lithium secondary battery according to the present invention can be used not only for a battery cell used as a power source for a small device, but also can be preferably used as a unit cell for a medium or large battery module including a plurality of battery cells. Preferred examples of the medium and large-sized devices include, but are not limited to, electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

Hereinafter, examples will be described in detail to illustrate the present invention in detail. However, the embodiments according to the present invention may be modified in various forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. Embodiments of the present invention are provided to more completely describe the present invention to those of ordinary skill in the art.

<Production of negative electrode active material>

Comparative example 1-1

A negative active material was prepared from granulated artificial graphite particles (a) having an average particle diameter (D50) of 21 µm.

Example 1-1

A negative electrode with graphite particles (c) obtained by mixing granulated artificial graphite particles (a) having an average particle diameter (D50) of 21 µm and fine graphite particles (b) having an average particle diameter (D50) of 5 to 10 µm at a weight ratio of 40:60 An active material was prepared.

<Manufacture of coin-type half battery>

Comparative example 1-2

The negative electrode active material prepared in Comparative Example 1-1, acetylene black as a conductive material, and styrene-butadiene rubber as a binder polymer were used, mixed at a weight ratio of 95:1:4, and mixed with distilled water as a solvent to prepare a slurry. . The prepared slurry was coated on one surface of a copper current collector to a thickness of 100 μm, dried and rolled, and then punched to a predetermined size to prepare a negative electrode. A non-aqueous electrolyte was prepared by adding 10% by weight of vinylene carbonate based on the weight of the electrolyte to an organic solvent prepared by mixing ethylene carbonate and diethyl carbonate at a weight ratio of 30:70 and a mixed solvent containing 1.0 M LiPF ₆ I did. A lithium metal foil was used as a counter electrode, and a polyolefin separator was interposed between both electrodes and the electrolyte was injected to prepare a coin-type half battery.

Example 1-2

A coin-type half-cell was manufactured in the same manner as in Comparative Example 1-2, except that the active material prepared in Example 1-1 was used.

Evaluation example

The particle size distribution of the active materials of Comparative Example 1-1 and Example 1-1 was calculated by counting the unit of fixel (channel) appearing on the two-dimensional screen, which is shown in FIG. 4 and Table 1 below. In FIG. 4,'Chan' on the Y-axis means a channel.

Particle size distribution D _min D ₁₀ D ₅₀ D ₉₀ Comparative Example 1-1 4.2 11.1 21.0 37.0 Example 1-1 2.5 6.3 15.6 32.4

A half coin cell battery was prepared and cycled under conditions of charging (CCCV, 0.1 C, 1/200 C Cut) and discharging (CC, 0.1 C, 1.5 V). After the fifth charge, as soon as the coin cell was disassembled, the thickness of the full negative electrode was measured, and the results are shown in Table 2 below.

Swelling comparison Comparative Example 1-2 Example 1-2 Capacity loading (mAh/cm ² ) 3.7 3.62 Rolling density A/V.D. 1.68 1.65 Thickness of electrode before charging (㎛) 86 Thickness at full charge after 5 cycles (㎛) 113 (standard deviation 0.1) Swelling degree (%) 41.4 (standard deviation 0.2) 32.4 (standard deviation 4.0)

Although the above description has been made with reference to the drawings according to the embodiments of the present invention, a person of ordinary skill in the field to which the present invention belongs will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

Claims (5)

In the negative electrode for a lithium secondary battery,
The negative electrode active material constituting the negative electrode consists only of fine-grained artificial graphite particles having a D50 average particle diameter in the range of 5 µm to 10 µm and granulated artificial graphite particles having a D50 average particle diameter of 15 µm to 25 µm. ,
The fine artificial graphite particles are included in an amount of 5 to 70% by weight based on the total weight of the fine artificial graphite particles and the granulated artificial graphite particles,
The negative electrode has a (004)/(110) orientation in the range of 15 to 25 at a compressive density of 1.65 g/cc,
The negative electrode for a lithium secondary battery, characterized in that both the granulated artificial graphite particles and the fine artificial graphite particles have a plate shape.
The method of claim 1,
The fine artificial graphite particles have a (004)/(110) orientation in the range of 3 to 20 at a compressive density of 1.65 g/cc, and the granulated artificial graphite particles have a (004) in the range of 5 to 20 at a compression density of 1.65 g/cc. )/(110) A negative electrode for a lithium secondary battery, characterized in that it has an orientation degree.
delete The method of claim 1,
A negative electrode for a lithium secondary battery, characterized in that the fine artificial graphite particles having an average diameter of 3 to 5 μm D50 are included as a conductive material.
A lithium secondary battery comprising the negative electrode according to any one of claims 1, 2 and 4.

Images