KR102672237B1 - Anode for lithium secondary battery and methode of manufacturing the same - Google Patents

Abstract

Exemplary embodiments of the present invention include artificial graphite arranged in a direction perpendicular to the current collector plate by a magnetic field, and a negative electrode active material layer coated on the current collector. When applied, the negative electrode for lithium secondary batteries can improve battery output characteristics such as charge/discharge output and rapid charging without deteriorating lifespan and high-temperature storage characteristics.

Description

Anode for lithium secondary battery and method of manufacturing same {ANODE FOR LITHIUM SECONDARY BATTERY AND METHODE OF MANUFACTURING THE SAME}

The present invention relates to a negative electrode for a lithium secondary battery and a method of manufacturing the same.

Secondary batteries are batteries that can be repeatedly charged and discharged, and with the development of the information and communication and display industries, they are widely used as a power source for portable electronic communication devices such as camcorders, mobile phones, and laptop PCs. Additionally, recently, battery packs including secondary batteries have been developed and applied as a power source for eco-friendly vehicles such as hybrid vehicles.

Examples of secondary batteries include lithium secondary batteries, nickel-cadmium batteries, and nickel-hydrogen batteries. Among these, lithium secondary batteries have high operating voltage and energy density per unit weight, and are advantageous for charging speed and weight reduction. In this regard, active research and development is underway.

A lithium secondary battery may include an electrode assembly including a positive electrode, a negative electrode, and a separator, and an electrolyte impregnating the electrode assembly. The lithium secondary battery may further include an exterior material, for example in the form of a pouch, that accommodates the electrode assembly and the electrolyte.

For example, a lithium secondary battery may include a negative electrode made of a carbon material capable of storing and releasing lithium ions, a positive electrode made of a lithium-containing oxide, and a non-aqueous electrolyte solution in which an appropriate amount of lithium salt is dissolved in a mixed organic solvent.

Meanwhile, amorphous carbon or crystalline carbon is used as the negative electrode active material used in the negative electrode, and among these, crystalline carbon is mainly used because of its high capacity. Such crystalline carbon includes natural graphite and artificial graphite.

In the case of artificial graphite, it is advantageous for structural stability and lifetime stability, but the plate-shaped particles are randomly arranged in a horizontal direction with the substrate, increasing the movement distance of lithium ions, which tends to be disadvantageous for the charging and discharging performance of the battery.

For example, Korea Patent Publication No. 10-2005-0004930 discloses technology regarding a negative electrode active material containing artificial graphite, but there may be limitations in improving discharge capacity or output.

Korean Patent Publication No. 10-2005-0004930

The purpose of the present invention is to provide a negative electrode for lithium secondary batteries that has excellent charge and discharge performance without deterioration in capacity and lifespan characteristics when applied to batteries.

Additionally, the present invention aims to provide a lithium secondary battery including the negative electrode for the lithium secondary battery and a method for manufacturing the same.

A negative electrode for a lithium secondary battery according to exemplary embodiments of the present invention includes a current collector and a negative electrode active material layer including artificial graphite coated on the current collector and arranged in a direction perpendicular to the plane of the current collector by a magnetic field, The colorimetric value of the negative electrode active material layer may be 50 to 70.

In some embodiments, the magnetic field may be arranged so that the magnetic field lines penetrate the anode active material layer in a vertical direction.

In some embodiments, the artificial graphite may have an orientation value expressed in Equation 1 below of 0.05 to 0.5.

[Equation 1]

(In Equation 1 above, Ah is the orientation arrangement value, R ₀ is the ratio of the ellipsoid axis, and when R ₀ is 1, there is no orientation arrangement, and θ is the ratio of the current collector and the artificial graphite measured by X-ray diffraction analysis. is the angle (radians) formed, M is the multiplicity factor and n is the number of trials.

A method of manufacturing a negative electrode for a lithium secondary battery according to exemplary embodiments of the present invention includes a process of producing a negative electrode slurry containing artificial graphite particles, and a process of forming a current collector containing the negative electrode slurry by applying the negative electrode slurry onto a current collector. , and a process of introducing the current collector containing the negative electrode slurry into a magnetic field to orient the (002) plane of the artificial graphite particles perpendicular to the current collector.

In some embodiments, a colorimeter value measured before introducing a magnetic field to the current collector containing the negative electrode slurry may be 56.5 or less.

In some embodiments, the colorimeter value measured after the orientation process may be 50 or more.

In some embodiments, a pressurizing process may be further included after the orientation process.

Lithium secondary batteries according to exemplary embodiments of the present invention may include a negative electrode for a lithium secondary battery, a positive electrode, and a separator interposed between the negative electrode and the positive electrode of the lithium secondary battery.

The anode for a lithium secondary battery according to the present invention improves battery output characteristics such as charge/discharge output and fast charging characteristics when applied to a battery.

In addition, the anode for a lithium secondary battery according to the present invention has excellent battery life and high-temperature storage characteristics when applied to a battery.

1 is a schematic cross-sectional view showing the structure of an exemplary negative electrode for a lithium secondary battery.
Figure 2 is a scanning electron microscope (SEM) photograph of a negative electrode for a lithium secondary battery that has undergone an orientation process of the negative electrode active material.
Figure 3 is a scanning electron microscope (SEM) photograph of a negative electrode for a lithium secondary battery without performing an orientation process of the negative electrode active material.

Exemplary embodiments of the present invention provide a negative electrode for a lithium secondary battery including a current collector and a negative electrode active material layer including artificial graphite coated on the current collector and aligned in a direction perpendicular to the plane of the current collector by a magnetic field. . When applied to a battery, the negative electrode for a lithium secondary battery can improve battery output characteristics such as charge/discharge output and fast charging characteristics without deteriorating lifespan and high-temperature storage characteristics.

Hereinafter, specific embodiments of the present invention will be described. However, this is only an example and the present invention is not limited thereto.

<Cathode>

When natural graphite is used as a negative electrode active material, problems may occur in the electrode process, such as causing filter clogging during the mixing process or reducing slurry dispersibility. However, artificial graphite has fewer such problems and has a longer lifespan and higher temperature than natural graphite. Excellent storage characteristics.

In general, artificial graphite, which is used as an active material for negative electrodes for lithium-ion secondary batteries, has a layer structure with a plurality of layers, and charging and discharging can be performed as lithium ions are inserted and desorbed between the plurality of layers. Insertion and desorption of lithium ions may occur mainly in the direction of the graphite layer, which may limit output characteristics.

If the (002) plane or layer plane of the graphite particle is oriented in a direction parallel to the plane of the current collector, the movement path of lithium ions that are inserted and desorbed in the direction perpendicular to the plane of the current collector may be long. Therefore, during charging and discharging, the diffusion of lithium ions in the negative electrode mixture layer may be reduced, and the charging and discharging speed and capacity may be reduced.

1 is a schematic plan view showing the structure of an exemplary negative electrode for a lithium secondary battery. For example, the red line shown in Figure 1 represents the movement path through which lithium ions can be inserted and desorbed. Referring to FIG. 1, when the (002) plane of the graphite particle is oriented in a direction perpendicular to the current collector plane, the path through which lithium ions are inserted and desorbed may be shortened.

Accordingly, the present invention orients the (002) plane of the graphite particles in a direction perpendicular to the current collector plane, and introduces a colorimetric value as a means of measuring the degree of orientation of the graphite inside the negative electrode.

The negative electrode for a lithium secondary battery according to embodiments of the present invention may include a negative electrode active material layer including artificial graphite arranged in a direction perpendicular to the current collector plane by a magnetic field. In this case, the colorimetric value of the negative electrode active material layer may be 50 to 70. Preferably, the colorimeter value may be 50 to 65. If the colorimeter value is 50 or less, the surface structure of the graphite material may have an irregular shape and may cause deformation of the cathode during repeated charging and discharging. When the colorimeter value is 65 or more, the artificial graphite having a plate-like structure may have an orientation lying horizontally in the direction of the current collector plane, and as a result, insertion and desorption of lithium ions are hindered when applying the negative electrode to a battery. Charging and discharging efficiency may decrease.

The measured colorimetric value may be 50 to 65.

By being above this, when applied to a battery, output characteristics can be excellent without deterioration in lifespan and high-temperature storage characteristics.

The artificial graphite can be used without particular limitations as long as it has a shape capable of inserting and desorbing lithium ions. However, in terms of improving the function of the anode active material for lithium secondary batteries, the aspect ratio may typically be 20 or more. . Therefore, the (002) plane of the oval-shaped artificial graphite particle can be oriented in a direction perpendicular to the plane of the current collector by the manufacturing process of the present invention described later.

In exemplary embodiments, the magnetic field may be applied by disposing the negative active material layer between a pair of magnetic field generating means. For example, if a cathode slurry with an irregular orientation for each artificial graphite particle is placed in the direction of the magnetic field lines in a magnetic field, the orientation distribution of the artificial graphite appears according to the direction distribution of the magnetic field lines, so the orientation direction of the artificial graphite can be controlled.

The negative electrode for a lithium secondary battery of the present invention is prepared by mixing and stirring the above-described artificial graphite with a solvent, a binder, a conductive material, a dispersant, etc. as necessary to prepare a slurry, and then applying (coating) the slurry to a current collector of a metal material and compressing it. It can be manufactured.

Non-aqueous solvents can typically be used as solvents. Non-aqueous solvents include, for example, N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc. , but is not limited to this.

As a binder, those used in the art can be used without particular limitation, for example, vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), Organic binders such as polyacrylonitrile and polymethylmethacrylate, or aqueous binders such as styrene-butadiene rubber (SBR) can be used together with a thickener such as carboxymethyl cellulose (CMC).

The content of the binder can be set to the amount necessary to form the electrode and is not particularly limited, but may be 3% by weight or less of the total weight of the negative electrode active material and binder in order to improve the resistance characteristics within the electrode. Meanwhile, the lower limit of the binder content is not particularly limited, but can be sufficient to maintain the function of the electrode. For example, it may be 0.5% by weight or 1% by weight of the total weight of the negative electrode active material and binder.

As a conductive material, a typical conductive carbon material can be used without any restrictions.

The current collector made of a metal material is a metal that has high conductivity and to which the slurry of the positive or negative electrode active material can easily adhere, and any metal that is non-reactive within the voltage range of the battery can be used. Copper or a copper alloy can be used as the negative electrode current collector, but is not limited to this, and is not limited to stainless steel, nickel, copper, titanium or alloys thereof, or surface treatment of carbon, nickel, titanium, or silver on the surface of copper or stainless steel. etc. may also be used.

In exemplary embodiments, the negative electrode for a lithium secondary battery includes a process of manufacturing the negative electrode slurry, a process of applying the negative electrode slurry on a current collector to form a current collector containing the negative electrode slurry, and applying the current collector containing the negative electrode slurry to a magnetic field. It may include a process of orienting the (002) plane of the artificial graphite particle perpendicularly to the current collector.

For example, the magnetic field may be applied by disposing the anode active material layer between a pair of magnetic field generating means. For example, the magnetic field may be arranged so that the magnetic field lines penetrate the anode active material layer in a vertical direction. Therefore, high current characteristics can be improved while maintaining the battery capacity of the lithium secondary battery.

In some embodiments, the magnetic fields may be parallel and uniform. In this case, the arrangement direction of the artificial graphite particles can be prevented from being disturbed due to the changing direction distribution of the magnetic force lines, and the (002) plane of the artificial graphite can be uniformly oriented in the direction perpendicular to the current collector.

The magnetic field generating means is not limited as long as it can generate a magnetic field, but electromagnets and superconducting magnets are preferably used.

The speed at which the current collector containing the negative electrode slurry passes through the magnetic field is not limited, but may be, for example, 0.1 m/min to 50 m/min. The slower the passing speed, the longer the cathode slurry stays in the magnetic field, and the alignment effect of the artificial graphite may increase.

In exemplary embodiments, a drying process may be further included after the aligning process, and a pressurizing process may be further included after the drying process.

The drying process can fix the oriented artificial graphite particles. For example, various drying methods such as natural drying, heat drying, reduced pressure drying, and blow drying can be used and can be performed in several steps.

The negative active material layer may be formed on the current collector through the drying process. In exemplary embodiments, a colorimeter value of the current collector containing the negative electrode slurry before introducing a magnetic field may be 56.5 or less. Therefore, through the aligning process and the drying process, it can be confirmed that the artificial graphite particles arranged along the normal direction of the current collector appear darker than before being arranged, and it can be confirmed that the colorimetric value decreases after self-orientation. there is.

The term 'colorimetric value' used in the present invention may refer to the L value representing brightness in color coordinates such as L*a*b*. The L value is displayed from 0 to 100, and the closer it is to 0, the whiter it is, and the closer it is to 100, the blacker it is. According to the negative electrode manufacturing process described later, the value of the color difference meter may increase as the artificial graphite is oriented perpendicular to the current collector surface by a magnetic field.

There is no limitation to the equipment for measuring the colorimeter, but for example, equipment such as a spectrophotometer, colorimeter, color reader, and colorimeter can be used. For example, the colorimeter can be measured using a Chroma meter CR-410 KONIKA MINOLTA meter.

In the present invention, the measured colorimeter value may be 50 or more. Meanwhile, as the artificial graphite arranged in a vertical direction on the current collector by a magnetic field is pressed by a pressurizing process, the colorimetric value measured after the coating may decrease.

As described above, according to embodiments of the present invention, the current collector containing the negative electrode slurry can be introduced into a magnetic field to orient the (002) plane of the artificial graphite particle perpendicular to the current collector.

The more randomly the orientation of each primary particle of artificial graphite is distributed, the more disadvantageous it may be for lithium ions to enter and exit the artificial graphite. In this embodiment, the particles are oriented in a direction perpendicular to the current collector plate to form a battery. When applied, the output characteristics of the battery can be further improved.

The orientation of the artificial graphite particles may be determined according to XRD analysis (X-ray diffraction). Specifically, the irradiated The orientation of graphite particles can be determined.

According to exemplary embodiments, the artificial graphite may have an orientation array value of 0.05 to 0.5, expressed in Equation 1 below.

[Equation 1]

(In Equation 1 above, Ah is the orientation arrangement value, R ₀ is the ratio of the ellipsoid axis, and when R ₀ is 1, there is no orientation arrangement, and θ is the ratio of the current collector and the artificial graphite measured by X-ray diffraction analysis. is the angle in radians, M is the multiplicity factor and n is the number of trials).

The closer the orientation array value is to 0, the closer the (002) plane of the artificial graphite is to the current collector. The closer the orientation array value is to 1, the closer the (002) plane of the artificial graphite is to the current collector. This means that the current collector is oriented horizontally. The orientation arrangement can be measured, for example, by using The orientation array value can be calculated according to Equation 1 described above.

When the orientation value of the artificial graphite is 0.05 or less, it is difficult for lithium ions to be intercalated in the plane of the graphite layer, which may result in low lithium ion storage capacity. When the orientation value of the artificial graphite is greater than 0.5, the surface area is large and the edge surface may be exposed due to the irregular structure, so destruction may occur due to electrolyte penetration or decomposition reaction.

In the XRD analysis method (X-ray diffraction), XRD measurement conditions known in the art can be used without any restrictions, for example

X-ray: Cu K alpha

K-Alpha1 wave length: 1.540598 Å

Generator voltage: 40kV

Tube current: 30mA

Scan Range: 10~80

Scan Step Size: 0.026

Ni filter, Solar slit (0.04rad, 2ea), Diffracted antiscatter slit 7.5mm

Divergence slit: 1/4˚

Antiscatter slit: 1/2˚

Time per step: 100s

It may be the same XRD measurement conditions.

According to one embodiment of the present invention, the electrode density of the negative electrode active material layer may be, for example, 1.45 g/cm ³ or more, and the upper limit is not particularly limited. When the electrode density of the cathode satisfies the above range, output, lifespan, and high-temperature storage characteristics can be improved when manufacturing the electrode.

<Anode>

The positive electrode active material according to the present invention and the positive electrode containing the same may be used without particular limitation as long as they are commonly used in the art.

The positive electrode can be manufactured by coating the positive electrode active material on the positive electrode current collector.

Aluminum or aluminum alloy can be used as the positive electrode current collector, but is not limited to this, and is not limited to stainless steel, nickel, aluminum, titanium or alloys thereof, or surface treatment of aluminum or stainless steel with carbon, nickel, titanium, or silver. etc. may also be used.

The positive electrode active material is not particularly limited, and commonly used positive electrode active materials can be used. For a specific example, at least one type selected from cobalt, manganese, nickel and at least one type of complex oxide of lithium are preferable, and representative examples include the lithium-containing compounds described below.

Li _x Mn _1-y M _y A ₂

Li _x Mn _1-y M _y O _{2- z}

Li _x Mn ₂ O _{4- z}

Li _x Mn _2-y M _{y M'z} A ₄

Li _x Co _1-y M _y A ₂

Li _x Co _1-y M _y O _{2- z}

Li _x Ni _1-y M _y A ₂

Li _x Ni _1-y M _y O _{2- z}

Li _x Ni _1-y Co _y O _{2- z}

Li _x Ni _1-yz Co _y M _z A _α

Li _x Ni _1-yz Co _y M _z O _{2- α}

Li _x Ni _1-yz Mn _y M _z A _α

Li _x Ni _1-yz Mn _y M _z O _2-α

In the formula, 0.9≤x≤1.1, 0≤y≤0.5, 0≤z≤0.5, 0≤α≤2, M and M' are the same or different, Mg, Al, Co, K, Na, Ca, A is selected from the group consisting of Si, Ti, Sn, V, Ge, Ga, B, As, Zr, Mn, Cr, Fe, Sr, V and rare earth elements, and A is selected from the group consisting of O, F, S and P. and X is selected from the group consisting of F, S and P.

In the present invention, the method of coating the positive electrode active material on the positive electrode current collector is not particularly limited as long as it is a method commonly used in the art, and the method of coating the negative electrode slurry on the carbon nanotube sheet described above can be used.

Specifically, the positive electrode according to the present invention is prepared by mixing and stirring the positive electrode active material with a solvent and, if necessary, a binder, a conductive material, a dispersant, etc. to prepare a slurry, which is then applied (coated) to a current collector of a metal material, compressed, and then dried. It can be manufactured.

Non-aqueous solvents can typically be used as solvents. Non-aqueous solvents include, for example, N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc. , but is not limited to this.

As a binder, those used in the art can be used without particular limitation, for example, vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), Organic binders such as polyacrylonitrile and polymethylmethacrylate, or aqueous binders such as styrene-butadiene rubber (SBR) can be used together with a thickener such as carboxymethyl cellulose (CMC).

As a conductive material, a typical conductive carbon material can be used without any restrictions.

<Separator>

Separators include typical porous polymer films conventionally used as separators, such as polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylate copolymer. The porous polymer film produced can be used alone or by laminating them, or a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, etc., can be used, but is not limited thereto. . Methods for applying the separator to a battery include lamination, stacking, and folding of the separator and electrode, in addition to the general winding method.

<Non-aqueous electrolyte>

The non-aqueous electrolyte solution may include lithium salt as an electrolyte and an organic solvent.

Lithium salts commonly used in electrolytes for lithium secondary batteries can be used without limitation, and can be expressed ^as Li ⁺

The anions of this lithium salt are not particularly limited, but include F ^- , Cl ^- , Br ^- , 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 ^- , Examples include SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- .

Organic solvents commonly used in electrolytes for lithium secondary batteries can be used without limitation, and representative examples include propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl. Carbonate (dimethyl carbonate, DMC), ethylmethyl carbonate (EMC), methylpropyl carbonate, dipropyl carbonate, fluoroethylene carbonate (FEC), dimethyl sulfuroxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, Any one selected from the group consisting of sulfolane, gamma-butyrolactone, propylene sulfite, and tetrahydrofuran, or a mixture of two or more of these, may be used.

The above-mentioned non-aqueous electrolyte solution is manufactured into a lithium secondary battery by injecting it into an electrode structure consisting of a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode.

<Lithium secondary battery>

The lithium secondary battery of the present invention includes a negative electrode containing the above-described negative electrode active material, a positive electrode, and a separator interposed between the positive electrode and the negative electrode.

The lithium secondary battery of the present invention is manufactured with an electrode structure in which a separator is interposed between the positive electrode and the negative electrode according to the present invention, and then stored in a battery case and injected into the electrolyte solution.

The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be cylindrical, prismatic, pouch-shaped, or coin-shaped using a can.

Hereinafter, preferred embodiments are presented to aid understanding of the present invention, but these examples are only illustrative of the present invention and do not limit the scope of the appended claims, and are examples within the scope and technical idea of the present invention. It is obvious to those skilled in the art that various changes and modifications are possible, and it is natural that such changes and modifications fall within the scope of the appended patent claims.

Examples and Comparative Examples

Example 1

<Cathode>

After preparing artificial graphite particles as a negative electrode active material, the negative electrode active material, styrene butadiene rubber (SBR), and carboxymethylcellulose (CMC) as a thickener were mixed in a mass ratio of 97.8:1.2:1.0 and then dispersed in deionized distilled water to form the negative electrode. A slurry was prepared and applied to one side of the Cu-foil current collector.

The current collector on which the negative electrode slurry was applied was moved at a speed of 4 m/min by placing a magnetic field so that it penetrated the negative electrode active material layer in the vertical direction, and an orientation process of the negative electrode active material by the magnetic field was performed. Figure 2 is a scanning electron microscope (SEM) photograph of a negative electrode for a lithium secondary battery that has undergone an orientation process of the negative electrode active material.

After the orientation process, drying and pressurization were performed to form a negative electrode active material layer with a size of 10 cm × 10 cm × 50 μm, thereby producing a negative electrode with an electrode density of 1.50 ± 0.05 g/cm ³ .

<Anode>

Li _1.0 Ni _0.6 Co _0.2 Mn _0.2 O ₂ as the positive electrode active material, Denka Black as the conductive material, PVDF as the binder, and N-Methyl pyrrolidone as the solvent, 46: 2.5: 1.5: After preparing the positive electrode slurry with each mass ratio composition of 50, the positive electrode was manufactured by coating, drying, and pressing it on an aluminum substrate.

<battery>

The manufactured positive and negative electrodes are notched and laminated to appropriate sizes, and a battery is constructed by interposing a separator (polyethylene, 25㎛ thick) between the positive and negative electrode plates, and the tab portion of the positive electrode and the negative electrode are welded, respectively. did. The welded anode/separator/cathode combination was placed in a pouch, and the part with the tab was included in the sealing area to seal three sides excluding the electrolyte injection surface. Electrolyte was injected into the remaining part, the remaining side was sealed, and then impregnated for more than 12 hours. The electrolyte was prepared by preparing a 1M LiPF ₆ solution with a mixed solvent of ethylene carbonate (EC)/ethylmethyl carbonate (EMC)/diethylene carbonate (DEC) (25/45/30; volume ratio), and then adding 1 wt of vinylene carbonate (VC). %, 0.5 wt% of 1,3-propenesultone (PRS) and 0.5 wt% of lithium bis(oxalato)borate (LiBOB) were added.

Afterwards, pre-charging was performed for 36 minutes with a current (2.5A) equivalent to 0.25C. After degassing for 1 hour and aging for more than 24 hours, chemical charging and discharging was performed (charge conditions CC-CV 0.2C 4.2V 0.05C CUT-OFF, discharge conditions CC 0.2C 2.5V CUT-OFF). After that, standard charging and discharging was performed (charging conditions CC-CV 0.5 C 4.2V 0.05C CUT-OFF, discharging conditions CC 0.5C 2.5V CUT-OFF).

Example 2

A lithium secondary battery was manufactured in the same manner, except that the moving speed of the current collector on which the negative electrode slurry was applied in the orientation process was changed to 8 m/min.

Example 3

A lithium secondary battery was manufactured in the same manner, except that the moving speed of the current collector on which the negative electrode slurry was applied in the orientation process was changed to 12 m/min.

Comparative Example 1

A lithium secondary battery was manufactured in the same manner, except that the orientation process was not performed. Figure 3 is a scanning electron microscope (SEM) photograph of a negative electrode for a lithium secondary battery without performing an orientation process of the negative electrode active material.

For Examples 1 to 3 and Comparative Example 1, the color difference meter after the current collector orientation process and the color difference meter after the pressurization process are shown in Table 1 below. However, the value of the colorimeter after the alignment process in Comparative Example 1 represents the colorimeter in the state in which the slurry was applied to the current collector without performing the alignment process.

Colorimeter after orientation process Colorimeter after pressurization process Example 1 59.67 50.98 Example 2 59.02 50.8 Example 3 58.57 51.43 Comparative Example 1 57.64 49.86

Experiment example

Fast charging characteristics experiments were performed on lithium secondary batteries manufactured according to Examples and Comparative Examples.

<Fast charging characteristics>

After manufacturing a cell with a large capacity of 10 Ah or more using the cathode manufactured according to the examples and comparative examples and all the same anode, the cell was manufactured at a constant temperature ( Rapid charging evaluation was conducted in a chamber maintained at 25°C.

<Measurement of azimuth array value>

The (002) peak intensity of the cathode manufactured according to the Examples and Comparative Examples was measured in XRD analysis, and the orientation value was measured according to Equation 1 above.

Specifically, the orientation alignment values were measured according to the following experimental conditions.

XRD(X-Ray Diffractometer)

Maker: PANalytical

Anode material: Cu

K-Alpha1 wavelength: 1.540598 Å

Generator voltage: 40kV

Tube current: 30mA

Scan Range: 10~80˚

Scan Step Size: 0.026˚

Divergence slit: 1/4˚

Antiscatter slit: 1/2˚

Time per step: 100s

Fast charge time (minutes) azimuth arrangement Example 1 25.9 0.41 Example 2 27.8 0.43 Example 3 29.9 0.49 Comparative Example 1 34.5 0.67

Referring to Table 2, it can be seen that the examples including the process of orienting the artificial graphite by a magnetic field showed a shortened rapid charging time compared to the comparative examples.

In addition, the longer the magnetic field application time in the orientation process, the more uniformly the artificial graphite particles are oriented, so it can be seen that the colorimetric value of the negative electrode active material layer appears larger, and when the value is 50 or more, the output characteristics of the lithium secondary battery This improvement appears to be occurring.

100: Artificial graphite 200: Current collector

Claims (8)

house collector; and
A negative electrode active material layer is coated on the current collector and includes artificial graphite whose long axis is aligned perpendicular to the plane of the current collector by a magnetic field,
The artificial graphite has an oval shape,
A negative electrode for a lithium secondary battery, wherein the colorimeter value of the negative electrode active material layer is 50 to 65 and the orientation value expressed by the following equation 1 is 0.05 to 0.5:
[Equation 1]

(In Equation 1 above, Ah is the orientation arrangement value, R ₀ is the ratio of the ellipsoid axis, and when R ₀ is 1, there is no orientation arrangement, and θ is the ratio of the current collector and the artificial graphite measured by X-ray diffraction analysis. is the angle in radians, M is the multiplicity factor, and n is the number of trials).
The anode for a lithium secondary battery according to claim 1, wherein the magnetic field lines penetrate the anode active material layer in a vertical direction.
delete A process for producing a cathode slurry containing artificial graphite particles having an oval shape;
A process of forming a current collector containing the negative electrode slurry by applying the negative electrode slurry onto a current collector;
A process of introducing the current collector containing the negative electrode slurry into a magnetic field to orient the long axis of the artificial graphite particles perpendicular to the current collector; and
A process of forming a negative electrode active material layer by pressurizing the current collector containing the negative electrode slurry,
A method of producing a negative electrode for a lithium secondary battery, wherein the colorimeter value of the negative electrode active material layer is 50 to 65 and the orientation value expressed by the following equation 1 is 0.05 to 0.5:
[Equation 1]

(In Equation 1 above, Ah is the orientation arrangement value, R ₀ is the ratio of the ellipsoid axis, and when R ₀ is 1, there is no orientation arrangement, and θ is the ratio of the current collector and the artificial graphite measured by X-ray diffraction analysis. is the angle in radians, M is the multiplicity factor, and n is the number of trials).
The method of claim 4, wherein the colorimeter value measured before introduction of the magnetic field of the current collector containing the negative electrode slurry is 56.5 or less.
The method of claim 4, wherein the colorimeter value measured after the orientation process is 50 or more.
delete Negative electrode for lithium secondary battery;
anode; and
It includes a separator interposed between the negative electrode and the positive electrode for the lithium secondary battery,
The negative electrode for the lithium secondary battery is
A negative electrode active material layer comprising a current collector and artificial graphite coated on the current collector and having a long axis aligned perpendicular to the plane of the current collector by a magnetic field, wherein the artificial graphite has an oval shape,
A lithium secondary battery in which the colorimetric value of the negative electrode active material layer is 50 to 65 and the orientation value expressed by the following equation 1 is 0.05 to 0.5:
[Equation 1]

(In Equation 1 above, Ah is the orientation arrangement value, R ₀ is the ratio of the ellipsoid axis, and when R ₀ is 1, there is no orientation arrangement, and θ is the ratio of the current collector and the artificial graphite measured by X-ray diffraction analysis. is the angle in radians, M is the multiplicity factor, and n is the number of trials).