KR102436898B1 - 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 plane by a magnetic field, and a negative electrode active material layer coated on the current collector. When the negative electrode for a lithium secondary battery is applied, it is possible to improve the output characteristics of the battery such as charge/discharge output and rapid charging without deterioration of lifespan and high-temperature storage characteristics.

Description

Anode for lithium secondary battery and manufacturing method thereof

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

A secondary battery is a battery that can be repeatedly charged and discharged, and is widely applied as a power source for portable electronic communication devices such as camcorders, mobile phones, and notebook PCs with the development of information communication and display industries. Also, recently, a battery pack including a secondary battery has been developed and applied as a power source for an eco-friendly vehicle such as a hybrid vehicle.

Examples of the secondary battery include a lithium secondary battery, a nickel-cadmium battery, a nickel-hydrogen battery, and the like, and among them, the lithium secondary battery has high operating voltage and energy density per unit weight, and is advantageous for charging speed and weight reduction. In this regard, R&D is actively underway.

A lithium secondary battery may include an electrode assembly including a positive electrode, a negative electrode, and a separator (separator), and an electrolyte impregnating the electrode assembly. The lithium secondary battery may further include, for example, a pouch-type casing accommodating the electrode assembly and the electrolyte.

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

On the other hand, amorphous carbon or crystalline carbon is used as a negative electrode active material used for the negative electrode, and among them, crystalline carbon is mainly used because of its high capacity. Examples of such crystalline carbon include natural graphite, artificial graphite, and the like.

Artificial graphite is advantageous for structural stability and lifespan stability, but plate-shaped particles are randomly arranged in the horizontal direction with the substrate to increase the movement distance of lithium ions, which tends to be disadvantageous for charging and discharging performance of the battery.

For example, Korean Patent Application Laid-Open No. 10-2005-0004930 discloses a technology related to an anode active material including artificial graphite, but there may be limitations in improving discharge capacity or output.

Korean Patent Publication No. 10-2005-0004930

An object of the present invention is to provide a negative electrode for a lithium secondary battery having excellent charge/discharge performance without deterioration of capacity and lifespan characteristics when applied to a battery.

Another object of the present invention is to provide a lithium secondary battery including the negative electrode for a 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 an anode active material layer coated on the current collector and comprising artificial graphite arranged in a direction perpendicular to the plane of the current collector by a magnetic field, The color difference value of the anode active material layer may be 50 to 70.

In some embodiments, the magnetic field may be disposed such that the magnetic force line vertically penetrates the anode active material layer.

In some embodiments, the artificial graphite may have an azimuth arrangement value of 0.05 to 0.5 or less expressed by Equation 1 below.

[Equation 1]

(In Equation 1, Ah is the azimuth arrangement value, R ₀ is the ratio of the axis of the ellipsoid, and there is no orientation arrangement when the R ₀ value is 1, and θ is the current collector and the artificial graphite measured by X-ray diffraction analysis. It is the radian formed, where 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 step of preparing a negative electrode slurry including artificial graphite particles, a step of applying the negative electrode slurry on a current collector to form a current collector including a negative electrode slurry , and introducing the current collector including 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 introduction of the magnetic field of the current collector including the negative electrode slurry may be 56.5 or less.

In some embodiments, a colorimeter value measured after the orienting process may be greater than or equal to 50.

In some embodiments, the method may further include a pressing process after the orienting process.

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

When the negative electrode for a lithium secondary battery according to the present invention is applied to a battery, the output characteristics of the battery such as charge/discharge output and rapid charge characteristics are improved.

In addition, the negative electrode 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.
2 is a scanning electron microscope (SEM) photograph of a negative electrode for a lithium secondary battery that has been subjected to an alignment process of the negative electrode active material.
3 is a scanning electron microscope (SEM) photograph of a negative electrode for a lithium secondary battery in which an alignment process of the negative electrode active material is not performed.

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

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

<Cathode>

When natural graphite is used as an anode active material, problems may occur in the electrode process, such as clogging the filter or reducing slurry dispersibility during the mixing process. It has excellent storage properties.

In general, artificial graphite used for an active material of a negative electrode for a lithium ion secondary battery includes a layer structure having a plurality of layers, and charging and discharging may be performed while lithium ions are inserted and desorbed between the plurality of layers, in this case Lithium ions may be inserted and desorbed mainly in the direction of the graphite layer, so there may be limitations in output characteristics.

When the (002) plane or the layer plane of the graphite particles is oriented in a direction parallel to the surface of the current collector, the movement path of lithium ions inserted and desorbed in a direction perpendicular to the surface of the current collector may be lengthened. Therefore, during charging and discharging, diffusion of lithium ions in the negative electrode mixture layer may be reduced, and charging/discharging speed and capacity may decrease.

1 is a schematic plan view showing the structure of an exemplary negative electrode for a lithium secondary battery. For example, a red line shown in FIG. 1 indicates a migration path through which lithium ions can be inserted and desorbed. Referring to FIG. 1 , when the (002) plane of the graphite particles 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, in the present invention, the (002) plane of the graphite particles is oriented in a direction perpendicular to the current collector plane, and a color difference value is introduced as a means of measuring the orientation degree 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 active material layer including artificial graphite arranged in a direction perpendicular to the current collector plane by a magnetic field. In this case, the color difference value of the anode active material layer may be 50 to 70. Preferably, the color difference value may be 50 to 65. When the color difference value is 50 or less, the surface structure of the graphite material may exhibit an irregular shape and may cause deformation of the negative electrode during repeated charging and discharging. When the color difference value is 65 or more, artificial graphite having a plate-like structure may have an orientation lying in a horizontal direction in the plane direction of the current collector, and thus intercalation and deintercalation of lithium ions is prevented. Charging/discharging efficiency may decrease.

The measured colorimeter value may be 50 to 65.

As above, when applied to a battery, the output characteristics may be excellent without deterioration of the lifespan and high-temperature storage characteristics.

The artificial graphite may be used without particular limitation as long as it has a shape capable of intercalating and deintercalating lithium ions, but in terms of improving the function of the anode active material for a lithium secondary battery, an aspect ratio may be 20 or more. . Accordingly, the (002) plane of the elliptical artificial graphite particle may be oriented in a direction perpendicular to the plane of the current collector by the manufacturing process of the present invention, which will be described later.

In example embodiments, the magnetic field may be applied by disposing the anode active material layer between a pair of magnetic field generating means. For example, if a negative electrode slurry in an irregularly oriented state for each artificial graphite particle is disposed in the direction of magnetic force lines in a magnetic field, the alignment distribution of the artificial graphite appears according to the direction distribution of the magnetic lines of force, so the alignment 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 dispersing material, etc., if necessary, and then applying (coating) it to a current collector of a metal material and compressing it. can be manufactured.

As the solvent, a non-aqueous solvent may be generally used. As the non-aqueous solvent, for example, N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc. may be used. , but is not limited thereto.

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

The content of the binder may be set to an amount necessary to form the electrode and is not particularly limited, but may be 3 wt % or less of the total weight of the negative electrode active material and the binder in order to improve resistance properties in the electrode. On the other hand, the lower limit of the binder content is not particularly limited, but may be sufficient as long as it can maintain the function of the electrode, for example, 0.5% by weight or 1% by weight of the total weight of the negative electrode active material and the binder.

As the conductive material, a conventional conductive carbon material may be used without particular limitation.

The current collector made of a metal material has high conductivity and is a metal to which the slurry of the positive or negative electrode active material can easily adhere, and any metal that has no reactivity in the voltage range of the battery may be used. Copper or a copper alloy may be used as the negative electrode current collector, but is not limited thereto, and is made by surface-treating carbon, nickel, titanium, or silver on the surface of stainless steel, nickel, copper, titanium or alloys thereof, copper or stainless steel. etc. may be used.

In exemplary embodiments, the negative electrode for a lithium secondary battery includes a process for preparing the negative electrode slurry, a process for forming a current collector including the negative electrode slurry by applying the negative electrode slurry on a current collector, and a magnetic field for the current collector including the negative electrode slurry and aligning the (002) plane of the artificial graphite particles perpendicular 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 such that the magnetic force line penetrates the anode active material layer in a vertical direction. Therefore, it is possible to improve the large current characteristics while maintaining the battery capacity of the lithium secondary battery.

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

The magnetic field generating means is not limited as long as it is a means capable of generating a magnetic field, but preferably an electromagnet, a superconducting magnet, or the like may be used.

The speed at which the current collector including 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 negative electrode slurry stays in the magnetic field, and the alignment effect of the artificial graphite may increase.

In exemplary embodiments, the method may further include a drying step after the orienting step, and a pressing step after the drying step.

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

The negative active material layer may be formed on the current collector by the drying process. In example embodiments, the color difference value of the current collector including the negative electrode slurry before the magnetic field is introduced may be 56.5 or less. Therefore, through the orienting 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 they are arranged, and it can be confirmed that the color difference value decreases after self-alignment. have.

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

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

In the present invention, the measured colorimeter value may be 50 or more. On the other hand, the artificial graphite arranged in the vertical direction to the current collector by the magnetic field is pressed by the pressing process, and may decrease compared to the color difference meter value measured after the coating.

As described above, according to embodiments of the present invention, the (002) plane of the artificial graphite particles may be oriented perpendicularly to the current collector by introducing the current collector including the negative electrode slurry into a magnetic field.

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

The orientation of the artificial graphite particles may be determined according to X-ray diffraction. Specifically, the X-ray of a specific irradiated wavelength (λ) may represent diffraction peaks having different intensities at a specific incident angle (θ) or diffraction angle (2θ), among them, by analyzing the peak of the (002) plane The orientation of graphite particles can be determined.

According to exemplary embodiments, the artificial graphite may have an azimuth arrangement value of 0.05 to 0.5 expressed by Equation 1 below.

[Equation 1]

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

As the azimuth alignment value is closer to 0, it means that the (002) plane of the artificial graphite is vertically aligned with the current collector, and as the azimuth alignment value is closer to 1, the (002) plane of the artificial graphite is the (002) plane of the artificial graphite. It means that the current collector is oriented in the horizontal direction. The orientation arrangement may be measured, for example, by XRD analysis (X-ray diffraction), and by analyzing the intensity of the (002) plane peak of the graphite particles, the artificial graphite and the current collector angle may be measured, The azimuth arrangement value may be calculated according to Equation 1 described above.

When the azimuthal arrangement value of the artificial graphite is 0.05 or less, lithium ions are difficult to intercalate in the plane of the graphite layer, and thus, a low lithium ion storage capacity may be exhibited. When the azimuthal arrangement value of the artificial graphite is 0.5 or more, the surface area is large due to the irregular structure and the edge surface may be exposed as it is, so that destruction by the penetration of the electrolyte or the decomposition reaction may occur.

In XRD analysis (X-ray diffraction), XRD measurement conditions known in the art may be used without particular limitation, for example,

X-ray: Cu K alpha

K-Alpha1 wavelengt: 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 an XRD measurement condition such as

According to an embodiment of the present invention, the electrode density of the negative 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 negative electrode satisfies the above range, output, lifespan, and high temperature storage characteristics may be improved during electrode manufacturing.

<Anode>

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

The positive electrode may be prepared by coating the positive electrode active material on the positive electrode current collector.

As the positive electrode current collector, aluminum or an aluminum alloy may be used, but is not limited thereto, and carbon, nickel, titanium, and silver are surface-treated on the surface of stainless steel, nickel, aluminum, titanium or alloys thereof, aluminum or stainless steel. etc. may be used.

The positive electrode active material is not particularly limited, and a commonly used positive electrode active material may be used. As a specific example, at least one selected from cobalt, manganese, and nickel and at least one of lithium composite oxides are preferable, and as a representative example thereof, the lithium-containing compound described below may be preferably used.

Li _x Mn _1-y M _y A ₂

Li _x Mn _1-y M _y O _2-z X _z

Li _x Mn ₂ O _4-z X _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 X _z

Li _x Ni _1-y M _y A ₂

Li _x Ni _1-y M _y O _2-z X _z

Li _x Ni _1-y Co _y O _2-z X _z

Li _x Ni _1-yz Co _y M _z A _α

Li _x Ni _1-yz Co _y M _z O _2-α X _α

Li _x Ni _1-yz Mn _y M _z A _α

Li _x Ni _1-yz Mn _y M _z O _2-α X

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, Si, Ti, Sn, V, Ge, Ga, B, As, Zr, Mn, Cr, Fe, Sr, V and selected from the group consisting of rare earth elements, A is selected from the group consisting of O, F, S and P selected, 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 above-described method of coating the negative electrode slurry on the carbon nanotube sheet may be used.

Specifically, in the positive electrode according to the present invention, a slurry is prepared by mixing and stirring a solvent, a binder, a conductive material, a dispersing material, etc., with a positive electrode active material, if necessary, and then applying (coating) it to a current collector of a metal material, compressing it, and drying it can be manufactured.

As the solvent, a non-aqueous solvent may be generally used. As the non-aqueous solvent, for example, N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc. may be used. , but is not limited thereto.

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

As the conductive material, a conventional conductive carbon material may be used without particular limitation.

<Separator>

As the separator, conventional porous polymer films conventionally used as separators, for example, polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylate copolymer The porous polymer film produced by . As a method of applying the separator to a battery, in addition to the general method of winding, lamination, stacking, and folding of the separator and the electrode are possible.

<Non-aqueous electrolyte>

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

As the lithium salt, those commonly used in electrolytes for lithium secondary batteries may be used without limitation, and may be expressed as Li ⁺ X ⁻ .

The anion of the lithium salt is not particularly limited, but 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 ^- , SCN ⁻ and (CF ₃ CF ₂ SO ₂ ) ₂ N ⁻ and the like can be exemplified.

As the organic solvent, those commonly used in electrolytes for lithium secondary batteries may be used without limitation, representatively propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (dimethyl carbonate, DMC), ethylmethyl carbonate (EMC), methylpropyl carbonate, dipropyl carbonate, fluoroethylene carbonate (FEC), dimethylsulfuroxide, 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 thereof may be used.

The above-described non-aqueous electrolyte is injected into an electrode structure including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode to prepare a lithium secondary battery.

<Lithium secondary battery>

The lithium secondary battery of the present invention includes a negative electrode including the above-described negative 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 by using an electrode structure with a separator interposed between the positive electrode and the negative electrode according to the present invention, then accommodated in a battery case, and by injecting an electrolyte thereto.

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

Hereinafter, preferred embodiments are presented to help the understanding of the present invention, but these examples are merely illustrative of the present invention and do not limit the appended claims, and are within the scope and spirit 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 variations and modifications fall within the scope of the appended 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 carboxymethyl cellulose (CMC) as a thickener were mixed in a mass ratio of 97.8:1.2:1.0 and dispersed in distilled water from which ions were removed to disperse the negative electrode. A slurry was prepared and the slurry was applied to one side of a Cu-foil current collector.

A magnetic field was disposed so that the current collector coated with the negative electrode slurry vertically penetrated the negative electrode active material layer and moved at a speed of 4 m/min, and an orientation process of the negative active material by the magnetic field was performed. 2 is a scanning electron microscope (SEM) photograph of a negative electrode for a lithium secondary battery that has been subjected to an alignment process of the negative electrode active material.

An anode having an electrode density of 1.50±0.05 g/cm ³ was prepared by drying and pressing after the orientation process to form a negative active material layer having a size of 10 cm×10 cm×50 μm.

<Anode>

46: 2.5: 1.5: using Li _1.0 Ni _0.6 Co _0.2 Mn _0.2 O ₂ as a cathode active material, Denka Black as a conductive material, PVDF as a binder, and N-methyl pyrrolidone as a solvent After preparing a positive electrode slurry with each mass ratio composition of 50, it was coated, dried, and pressed on an aluminum substrate to prepare a positive electrode.

<Battery>

The prepared positive electrode and negative electrode are each stacked by notching to an appropriate size, and a separator (polyethylene, thickness 25㎛) is interposed between the positive electrode plate and the negative electrode plate to construct a battery, and the tab part of the positive electrode and the tab part of the negative electrode are welded, respectively. did The welded anode/separator/cathode combination was placed in the pouch, and the tab portion was included in the sealing area to seal three sides except for the electrolyte injection side. After injecting the electrolyte into the other part and sealing the remaining one side, it was impregnated for more than 12 hours. The electrolyte is a mixed solvent of ethylene carbonate (EC) / ethylmethyl carbonate (EMC) / diethylene carbonate (DEC) (25/45/30; volume ratio) to prepare a 1M LiPF ₆ solution, then vinylene carbonate (VC) 1wt %, 0.5 wt% of 1,3-propensultone (PRS) and 0.5 wt% of lithium bis(oxalato)borate (LiBOB) were used.

Thereafter, pre-charging was performed for 36 minutes at a current (2.5A) corresponding to 0.25C. After 1 hour of degasing and aging for more than 24 hours, chemical charge and discharge were performed (charge condition CC-CV 0.2C 4.2V 0.05C CUT-OFF, discharge condition CC 0.2C 2.5V CUT-OFF). After that, standard charging and discharging was performed (charge condition CC-CV 0.5 C 4.2V 0.05C CUT-OFF, discharge condition CC 0.5C 2.5V CUT-OFF).

Example 2

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

Example 3

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

Comparative Example 1

A lithium secondary battery was manufactured in the same manner except that the alignment process was not performed. 3 is a scanning electron microscope (SEM) photograph of a negative electrode for a lithium secondary battery in which an alignment process of the negative electrode active material is not performed.

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

Colorimeter after orientation process Colorimeter after pressing 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

Experimental example

A fast charging characteristic test was performed on lithium secondary batteries prepared according to Examples and Comparative Examples.

<Quick Charge Characteristics>

After manufacturing a cell having a large capacity of 10Ah or more using the negative electrode manufactured according to the Examples and Comparative Examples and the same positive electrode, the constant temperature ( 25° C.), a rapid charge evaluation was performed in a chamber maintained.

<Measure azimuth array value>

The (002) peak intensity of the negative electrode prepared according to Examples and Comparative Examples was measured in XRD analysis, and the azimuth arrangement value was measured according to Equation 1 above.

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

XRD (X-Ray Diffractometer) X’Pert PRO

Maker: PANalytical

Anode material: Cu

K-Alpha1 wavelength: 1.540598

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

Quick Charge Time (min) bearing 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 the magnetic field exhibit a shorter fast charging time compared to the comparative examples.

In addition, it can be seen that the artificial graphite particles are more uniformly oriented as the magnetic field is longer applied in the orientation process, so that the color difference value of the anode active material layer is large, and when the value is 50 or more, the output characteristics of the lithium secondary battery It has been shown that this is improving.

100: artificial graphite 200: current collector

Claims (10)

current collector; and
and a negative active material layer coated on the current collector and comprising artificial graphite with a (002) plane arranged in a vertical direction on the plane of the current collector by a magnetic field,
1.45 g/cm ³ The color difference value of the anode active material layer measured at an electrode density of 50 to 70 is, a negative electrode for a lithium secondary battery.
The negative electrode for a lithium secondary battery according to claim 1, wherein the magnetic field has a magnetic force line passing through the negative active material layer in a vertical direction.
The negative electrode for a lithium secondary battery according to claim 1, wherein the artificial graphite has an azimuth arrangement value of 0.05 to 0.5 represented by Equation 1 below:
[Equation 1]

(In Equation 1, Ah is an azimuth arrangement value, R ₀ is the ratio of the ellipsoid axis, and there is no orientation arrangement when the R ₀ value is 1, and θ is the current collector and the artificial graphite measured by X-ray diffraction analysis. It is the radian formed, where M is the multiplicity factor and n is the number of trials).
A process of preparing a negative electrode slurry containing artificial graphite particles;
forming a current collector including the negative electrode slurry by applying the negative electrode slurry on the current collector;
introducing the current collector including the negative electrode slurry into a magnetic field to orient the (002) plane of the artificial graphite particles perpendicular to the current collector; and
and pressing the current collector including the negative electrode slurry to form a negative electrode active material layer on the current collector,
After the pressing step, the color difference value of the anode active material layer measured at an electrode density of 1.45 g/cm ³ or more is 50 to 70, a method of manufacturing a negative electrode for a lithium secondary battery.
The method according to claim 4, wherein the color difference value measured before the introduction of the magnetic field of the current collector including the negative electrode slurry is 56.5 or less, the manufacturing method of the negative electrode for a lithium secondary battery.
The method for manufacturing a negative electrode for a lithium secondary battery according to claim 4, wherein the color difference value measured after the orienting process is 50 or more.
delete anode for lithium secondary batteries;
anode; and
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 current collector and a negative active material layer coated on the current collector and comprising artificial graphite with a (002) plane arranged in a vertical direction on the plane of the current collector by a magnetic field, wherein at an electrode density of 1.45 g/cm ³ or more The measured color difference value of the negative active material layer is 50 to 70, a lithium secondary battery.
The negative electrode for a lithium secondary battery according to claim 1, wherein the color difference value of the negative electrode active material layer is a value measured at an electrode density of 1.45 g/cm ³ to 1.55 g/cm ³ .
The negative electrode for a lithium secondary battery according to claim 1, wherein the color difference value of the negative active material layer is a value measured under the condition that the negative active material layer has a thickness of 50 μm.

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