KR102275230B1 - Anode for a lithium secondary battery and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a negative electrode for a secondary battery, and more particularly. In the negative electrode for a lithium secondary battery comprising a current collector and a negative electrode active material layer formed on at least one surface of the current collector, a central portion of the negative electrode active material layer includes hard carbon, and an outer portion includes graphite By doing so, it relates to an anode for a secondary battery having excellent initial cycle efficiency and improved cycle life characteristics, and a lithium secondary battery including the same.

Description

Anode for a lithium secondary battery and a lithium secondary battery including the same {ANODE FOR A LITHIUM SECONDARY BATTERY AND LITHIUM SECONDARY BATTERY COMPRISING THE SAME}

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

BACKGROUND With the rapid development of the electronics, communication, and computer industries, portable electronic communication devices such as camcorders, mobile phones, and notebook PCs are admirably developing. Accordingly, the demand for lithium secondary batteries as a power source capable of driving them is increasing day by day. In particular, as an eco-friendly power source, R&D is being actively carried out in Japan, Europe and the United States as well as in Korea in relation to the application of electric vehicles, uninterruptible power supplies, power tools, and satellites.

Among the secondary batteries currently being applied, lithium secondary batteries developed in the early 1990s are anodes made of carbon materials that can intercalate and desorb lithium ions, anodes made of lithium-containing oxides, etc., and lithium salts dissolved in an appropriate amount in a mixed organic solvent. It is composed of a non-aqueous electrolyte.

However, as the application range of lithium secondary batteries expands, longer lifespan and high capacity are required, and deterioration occurs in the electrode due to overcharging, etc., so that the charge/discharge capacity is reduced, the performance of the battery is reduced, and the lifespan is shortened. .

Korean Patent Application Laid-Open No. 2014-0085822 discloses an anode active material including a core particle and a shell layer including silicon and carbon-based particles, but the initial discharge capacity is not large, so an alternative to the above problem cannot be presented.

Korea Patent Publication No. 2014-0085822

An object of the present invention is to provide an anode for a lithium secondary battery having excellent initial cycle efficiency and improved cycle life characteristics, and a method for manufacturing the same.

1. A negative electrode for a lithium secondary battery comprising a current collector and an anode active material layer formed on at least one surface of the current collector,

A central portion of the negative active material layer includes hard carbon, and an outer portion includes graphite (Graphite), a negative electrode for a lithium secondary battery.

2. The anode for a lithium secondary battery according to 1 above, wherein the outer area of the anode active material layer is 10 to 20% of the area of the anode active material layer.

3. The negative electrode for a lithium secondary battery according to 1 above, wherein the central shape of the negative active material layer is polygonal or circular.

4. The negative electrode for a lithium secondary battery according to 1 above, wherein the density of the outer portion of the negative active material layer is higher than that of the central portion.

5. The anode for a lithium secondary battery according to 1 above, wherein the density of the outer portion of the anode active material layer is greater than 1 to less than 1.5 times the density of the central portion.

6. The anode for a lithium secondary battery according to 1 above, wherein the density of the outer portion of the anode active material layer is 1.0 to 2.5 g/cm 3 .

7. The anode for a lithium secondary battery according to 1 above, wherein the central portion of the anode active material layer further comprises a silicon-based active material.

8. In a lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte,

The negative electrode is the negative electrode of any one of claims 1 to 7, a lithium secondary battery.

The negative electrode for a lithium secondary battery of the present invention can improve the cycle life characteristics of the secondary battery by preventing local deterioration of the central portion.

In addition, the negative electrode for a lithium secondary battery of the present invention is excellent in initial cycle efficiency.

1 is a diagram schematically showing a cross-section of a negative electrode for a lithium secondary battery according to an embodiment of the present invention.
2 is a view schematically illustrating an anode active material layer for a lithium secondary battery according to an embodiment of the present invention.
3 is a diagram schematically illustrating a method of manufacturing a negative electrode for a lithium secondary battery according to an embodiment of the present invention.

The present invention is an anode for a lithium secondary battery, in the anode for a lithium secondary battery comprising a current collector and an anode active material layer formed on at least one surface of the current collector, wherein the central portion of the anode active material layer includes hard carbon, , The outer part includes graphite, thereby preventing local deterioration of the central part of the anode, thereby improving the performance of the secondary battery, and relates to a secondary battery negative electrode having excellent initial cycle efficiency and cycle life characteristics.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. However, the following drawings attached to the present specification illustrate preferred embodiments of the present invention, and serve to further understand the technical spirit of the present invention together with the above-described contents of the present invention, so the present invention is described in such drawings It should not be construed as being limited only to the matters.

negative electrode for secondary battery

In a lithium secondary battery using a carbon-based active material as an anode active material, as the structure of the anode is deformed due to the insertion and desorption of lithium ions, the movement of lithium ions is not smooth, and accordingly, the solid electrolyte interface (SEI, solid Electrolyte interface) causes a decrease in battery performance, and the present inventor devised the present invention by focusing on the fact that such deterioration of the anode occurs especially in the center of the anode.

Accordingly, the negative electrode for a lithium secondary battery of the present invention has almost no volume change during insertion and desorption of lithium ions, and a negative active material containing hard carbon having excellent cycle life characteristics is applied to the center of the negative electrode active material layer. It is possible to prevent the local deterioration of the central portion of the battery negative electrode, thereby reducing the difference between the deterioration degree of the central portion and the outer portion of the negative electrode.

However, since hard carbon exhibits a rather low initial cycle efficiency, the anode for a lithium secondary battery of the present invention applies an anode active material including graphite having excellent initial cycle efficiency to the outer part of the anode active material layer, It is possible to prevent the deterioration of the initial cycle while maintaining excellent initial cycle efficiency.

Therefore, in the negative electrode for a lithium secondary battery of the present invention, a negative active material containing hard carbon having excellent cycle life characteristics is applied to the center of the negative electrode active material layer, and the negative electrode active material containing graphite having excellent initial cycle efficiency is used as the negative electrode By applying it to the outer portion of the active material layer, it is possible to not only have excellent cycle characteristics, but also to prevent local deterioration of the central portion of the negative electrode of the secondary battery, thereby reducing the difference in the degree of deterioration between the central and outer portions of the negative electrode.

<Anode active material layer>

1 schematically shows a cross-section of a negative electrode for a secondary battery according to an embodiment of the present invention, and FIG. 2 schematically shows a negative electrode active material layer of a negative electrode for a lithium secondary battery according to an embodiment of the present invention.

The negative electrode 100 for a lithium secondary battery of the present invention includes a current collector 10 and an anode active material layer 20 formed on at least one surface of the current collector.

In the negative electrode 100 for a lithium secondary battery of the present invention, the central portion 40 of the negative electrode active material layer 20 includes hard carbon, and the central portion is positioned in the longitudinal direction (direction perpendicular to the thickness direction) of the current collector. The outer portion 30 surrounding the boundary portion of the electrode includes graphite.

The area of the central portion 40 and the outer portion 30 of the negative electrode active material layer 20 is not particularly limited, and can be appropriately adjusted according to the type, use, and environment of the battery. For example, the area of the outer portion 30 of the anode active material layer 20 may be 10 to 20% of the area of the anode active material layer 20 , but is not limited thereto. In the above range, the effect of preventing local deterioration of the central portion may be best exhibited without reducing the capacity of the battery.

The shape of the central portion 40 of the negative electrode active material layer 20 of the negative electrode 100 for a lithium secondary battery of the present invention is not particularly limited, and may be polygonal or circular as shown in FIG. 2 . The polygon includes, for example, a triangle, a quadrangle, a hexagon, an octagon, and a decagon, and the quadrangle includes a rectangle, a rhombus, and the like.

In the negative electrode 100 for a lithium secondary battery of the present invention, as the graphite applied to the outer portion 30 of the negative electrode active material layer 20, known graphite that can be used as the negative electrode active material may be used without limitation. For example, artificial graphite and natural graphite may be used alone or in combination.

In the negative electrode 100 for a lithium secondary battery of the present invention, the negative active material applied to the central portion 40 of the negative electrode active material layer 20 may further include a silicon-based active material. Since the silicon-based active material forms a compound with lithium ions and reversibly occludes and desorbs lithium ions, and has a high capacity, the silicon-based active material is mixed with hard carbon and applied to the center of the anode active material layer of the present invention. It is possible to prevent local deterioration of the central part of the cathode while maintaining the

In the negative electrode 100 for a lithium secondary battery of the present invention, the silicon-based active material applied to the central portion 40 of the negative electrode active material layer 20 is not particularly limited, and a commonly used negative electrode active material may be used. As a specific example, the silicon-based active material may include, but is not limited to, a silicon oxide, a silicon alloy, a silicon-carbon composite, and the like. Each of these may be used alone or in combination.

The silicon oxide is, for example, SiOx (0<x<2); a composite material comprising a core of SiOx (0<x<2) and a carbon coating layer coating the surface of the core; or a combination thereof. The SiOx (0.5≤x≤1.5) may have a structure in which _{ultrafine particles of silicon are dispersed in silicon dioxide (SiO 2 ).}

The silicon alloy is, for example, an alloy represented by X-Si (X = Ni, Fe, Co, Cu, Mn, Zn, In, Ag, Ti, Ge, Bi, Sb, Cr, Al, Sn, Mg and at least one of Pb).

In another aspect of the present invention, in the negative active material layer 20 of the present invention, the density of the outer portion 30 may be higher than that of the central portion 40 .

In the present specification, the density of the anode active material layer refers to the density of the anode active material layer formed after the anode active material is applied to the current collector and compressed to a predetermined pressure, and the high-density anode active material layer is a negative electrode having more active material under the same volume. means the active material layer.

The density of the outer portion 30 of the negative electrode active material layer 20 may be greater than 1 to less than 1.5 times the density of the central portion 40 . The effect of preventing local deterioration of the negative electrode while maintaining the excellent capacity of the secondary battery in the above range can be further improved.

The density of the outer portion of the anode active material layer according to the present invention is not particularly limited, but may preferably be 1.0 to 2.5 g/cm 3 . When the density of the outer portion is within the above range, cycle life characteristics may be improved.

Accordingly, the negative electrode 100 for a lithium secondary battery including the negative electrode active material layer 20 of the present invention has excellent initial cycle efficiency as well as prevents local deterioration of the central portion, thereby improving the cycle life characteristics of the battery.

Hereinafter, embodiments of the method for manufacturing the negative electrode of the present invention will be described in more detail.

3 schematically shows a method of manufacturing a negative electrode for a lithium secondary battery according to an embodiment of the present invention.

As shown in (a) of FIG. 3 , a rectangular mask 50 is placed at the center of the negative electrode current collector to form a rectangular central portion, and graphite is placed on the outer portion 60 of the negative electrode active material layer. A slurry containing a first coating.

Then, as shown in FIG. 3 (b), a mask 70 in the form of a window frame in which the central 80 is perforated is placed on the current collector to cover the outer portion 60 coated with the primary, and hard carbon (Hard) Carbon) containing slurry is coated. In this way, a negative electrode for a lithium secondary battery may be formed in which the central portion 80 includes hard carbon and the outer portion 60 includes an anode active material layer including graphite.

3 illustrates a method of coating the negative electrode slurry from the outer portion of the negative electrode active material layer, but the coating order may be changed

In the present invention, the method of coating the negative active material on the negative electrode current collector is not particularly limited as long as it is a method commonly used in the art. For example, after preparing a slurry by mixing and stirring a solvent and, if necessary, a binder, a conductive material, a dispersing agent, a thickener, etc. with the negative electrode active material, it can be applied (coated) on the positive electrode current collector by spray coating, dipping, etc. and then dried and compressed to form a negative electrode.

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

The conductive material is a material for improving electronic conductivity, and at least one selected from the group consisting of a graphite-based conductive material, a carbon black-based conductive material, and a metal or metal compound-based conductive material may be used. Examples of the graphite-based conductive material include artificial graphite, natural graphite, and the like, and examples of the carbon black-based conductive material include acetylene black, ketjen black, denka black, thermal black, and channel black ( channel black), and the like, and examples of the metal-based or metal compound-based conductive material include perovskite materials such as tin, tin oxide, tin phosphate (SnPO ₄ ), titanium oxide, potassium titanate, LaSrCoO ₃ , and LaSrMnO _{3 .} have. However, it is not limited to the conductive materials listed above.

The thickener is not particularly limited as long as it can control the viscosity of the active material slurry, and for example, carboxymethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, etc. may be used.

<The current collector>

The current collector 10 according to the present invention is a negative electrode current collector.

The current collector made of a metallic material is a metal that has high conductivity and can be easily adhered to the slurry of the negative electrode, 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 carbon, nickel, titanium, or silver is surface treated on the surface of stainless steel, nickel, copper, titanium or alloys thereof, copper or stainless steel. , etc. may be used.

In addition, the shape of the current collector 10 is not particularly limited, and a commonly used shape may be used. For example, a planar current collector, a hollow current collector, a wire-type current collector, a wound wire-type current collector, a wound sheet-type current collector, a mesh-type current collector, or the like can be used.

lithium secondary battery

The present invention provides a lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte.

The lithium secondary battery of the present invention is manufactured with an electrode structure with a separator interposed between a positive electrode and a negative electrode, and then accommodated in a battery case, and an electrolyte is injected therein.

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 -y- z} Co _y M _z A _α

Li _x Ni _{1 -y- z} Co _y M _z O _{2 -α} X _α

Li _x Ni _{1 -y- z} Mn _y M _z A _α

Li _x Ni _{1 -y- z} 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

In addition, the solvent, binder, conductive material, dispersant, etc. added to the positive electrode active material may be those used in preparing the negative electrode slurry described above.

As the separator, a conventional porous polymer film conventionally used as a separator, 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 prepared with the above may 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., may be used, but is not limited thereto. . 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.

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, dimethylsulfuroxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, gamma-butyrolactone , any one selected from the group consisting of 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.

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.

Example and comparative example

Example One

<Anode>

The positive electrode active material was _{Li 1 .1 Ni 1/3 Co} 1/3 Mn 1/3 O using _2, using PVDF as Denka Black, a conductive material and a binder of 92: 5: positive electrode slurry composition of each weight ratio of 3 After manufacturing, it was coated, dried, and pressed on an aluminum substrate to prepare a positive electrode.

<Cathode>

93 wt% of natural graphite (d002 3.358Å) as an anode active material for the outer part, 5 wt% of a flake type conductive material KS6 as a conductive material, 1 wt% of SBR as a binder, and 1 wt% of CMC as a thickener A negative electrode slurry for the outer part was prepared . A rectangular mask was placed on a copper substrate, and the prepared outer anode slurry was coated with a loading weight of ^{8 mg/cm 2 and dried.}

A central negative electrode slurry was prepared by mixing 93 wt% of hard carbon as an anode active material in the center, 5 wt% of KS6 as a flake type conductive material as a conductive material, 1 wt% of SBR as a binder, and 1 wt% of CMC as a thickener. A mask in the form of a window frame was placed to cover the coated outer portion on the copper substrate coated with the outer portion, but the uncoated central portion was opened, and the prepared central negative electrode slurry was coated with a loading weight of ^{2 mg/cm 2 and dried.} After that, a press was performed to prepare a negative electrode.

The area of the outer part was 10% of the area of the copper substrate, the density of the center was 1.3 g/cm 3 , and the density of the outer part was 1.5 g/cm 3 .

<Secondary Battery>

A battery was constructed using the positive electrode, the negative electrode, a separator (polyethylene, thickness of 25 μm), and a non-aqueous electrolyte (a mixed solvent of EC/EMC/DEC (25/45/30 volume ratio)).

Example 2

A secondary battery was prepared in the same manner as in Example 1, except for those shown in Table 1 below.

comparative example One

93% by weight of natural graphite (d002 3.358Å) as the negative electrode slurry, 5% by weight of KS6 as a flake type conductive material as a conductive material, 1% by weight of SBR as a binder, and 1% by weight of CMC as a thickener were used, and the negative electrode slurry was loaded at a loading of 8 mg/cm2 A battery was prepared in the same manner as in Example 1, except that it was coated with a weight and described in Table 1 below.

comparative example 2

93% by weight of hard carbon as the negative electrode slurry, 5% by weight of KS6, a flake type conductive material, as a conductive material, 1% by weight of SBR as a binder, and 1% by weight of CMC as a thickener were used, and the negative electrode slurry was coated with a loading weight of 8mg/cm2 and the following A battery was prepared in the same manner as in Example 1, except for those described in Table 1.

division area of the outskirts
(%) core density
(g/㎤) Outer Density
(g/㎤) Example 1 10 1.3 1.5 Example 2 15 1.3 1.3 Comparative Example 1 100 1.3 1.3 Comparative Example 2 100 1.3 1.3

Experimental example

The lithium secondary batteries of Examples and Comparative Examples were evaluated, and the results are shown in Table 1.

After repeating charging (CC-CV 0.5C, 0.01V, 0.05C CUT-OFF) and discharging (CC 0.5C, 1.4V CUT-OFF) 100 times of the manufactured lithium secondary battery, the cycle life characteristics are the initial charge capacity It was evaluated as a 100-cycle capacity retention rate, which is a ratio of the discharge capacity of the comparison battery.

division 1 ^st charge capacity
(mAh/g) 1 ^st discharge capacity
(mAh/g) 1 ^st efficiency
(%) 100 ^st cycle capacity retention rate
(%) Example 1 37.6 37.07 98.6 99.7 Example 2 37.2 36.61 98.4 99.5 Comparative Example 1 37.6 37.0 98.4 96.3 Comparative Example 2 37.4 36.6 97.8 96.2

Referring to Table 2, the secondary battery of the example has better initial cycle efficiency than the secondary battery of the comparative example. It was confirmed that the 100-cycle capacity retention rate was 3.4% higher than that of the secondary battery of Comparative Example, indicating that the cycle life characteristics were remarkably improved.

100: negative electrode for lithium secondary battery
10: current collector
20: anode active material layer
30: outer part
40: central
50: square shape mask
60: outer part
70: mask in the form of a window frame
80: central

Claims (8)

In the negative electrode for a lithium secondary battery comprising a current collector and an anode active material layer formed on at least one surface of the current collector,
The anode active material layer includes a central portion containing hard carbon and an outer portion containing graphite, and the outer portion is disposed on the same layer of the central portion and in contact with a side surface of the central portion, a negative electrode for a lithium secondary battery .
The negative electrode for a lithium secondary battery according to claim 1, wherein an outer area of the negative active material layer is 10 to 20% of an area of the negative active material layer.
The negative electrode for a lithium secondary battery according to claim 1, wherein the central shape of the negative electrode active material layer is polygonal or circular.
The negative electrode for a lithium secondary battery according to claim 1, wherein a density of the outer portion of the negative active material layer is higher than that of the central portion.
The negative electrode for a lithium secondary battery according to claim 1, wherein the density of the outer portion of the negative electrode active material layer is greater than 1 time to less than 1.5 times the density of the center portion.
The negative electrode for a lithium secondary battery according to claim 1, wherein the density of the outer portion of the negative active material layer is 1.0 to 2.5 g/cm 3 .
The negative electrode for a lithium secondary battery according to claim 1, wherein the central portion of the negative electrode active material layer further comprises a silicon-based active material.
In a lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte,
The negative electrode is the negative electrode of any one of claims 1 to 7, a lithium secondary battery.

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