JP2003017069A - Electrode for lithium secondary battery and lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode for a lithium secondary battery suppressing generation of large wrinkles or deformation and enhancing energy density in the electrode for the lithium secondary battery in which an active material thin film storing lithium by alloying the lithium is stacked on a current collector. SOLUTION: The current collector 10 has deformed parts 11 in which the deforming amount h in the thickness direction is 5-20 μm, of 10 or more per cm<2> , and an open area ratio of 4% or less formed with the deformed parts 11.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electrode for a lithium secondary battery and a lithium secondary battery using the same.

[0002]

2. Description of the Related Art In recent years, lithium secondary batteries, which have been actively researched and developed, have a charging / discharging voltage depending on an electrode used.
Battery characteristics such as charge / discharge cycle life characteristics and storage characteristics are greatly affected. Therefore, the battery characteristics are improved by improving the active material used for the electrode.

When lithium metal is used as the negative electrode active material, a battery having a high energy density per weight and volume can be constructed, but there is a problem that lithium is deposited in dendrite form during charging and causes an internal short circuit. It was

On the other hand, a lithium secondary battery using aluminum, silicon, tin, or the like, which is electrochemically alloyed with lithium during charging, as an electrode has been reported (So.
lidState Ionics, 113-115, p57 (1998)). Of these, silicon is particularly promising as a negative electrode for a battery having a large theoretical capacity and a high capacity, and various secondary batteries using this as a negative electrode have been proposed (JP-A-10-255768).
Issue). However, in this type of alloy negative electrode, sufficient cycle characteristics have not been obtained because the alloy itself, which is an electrode active material, becomes fine powder due to charge and discharge and deteriorates current collecting characteristics.

[0005]

The applicant of the present invention uses a thin film forming method such as a CVD method or a sputtering method as an electrode for a lithium secondary battery which uses silicon or the like as an electrode active material and exhibits good charge / discharge cycle characteristics. An electrode for a lithium secondary battery in which a microcrystalline thin film or an amorphous thin film is formed on a current collector has been proposed (Japanese Patent Application No. 11-301646, etc.).

In such an electrode for a lithium secondary battery, the components of the current collector are diffused into the active material thin film, so that the adhesion between the current collector and the active material thin film is maintained and the charge / discharge cycle characteristics are improved. I know it will improve.

However, in such an electrode for a lithium secondary battery, since the adhesion between the active material thin film and the current collector is good, the active material expands and contracts due to charge and discharge, and accordingly the current collection occurs. When the body extends, deformation such as wrinkles may occur in the electrodes. In particular, when a metal foil having a high ductility such as a copper foil is used as the current collector, the degree of deformation of the electrode increases. When the electrode is deformed, the volume in the battery accommodating the electrode is increased, and the energy density per volume of the battery is reduced, which is a problem.

An object of the present invention is to provide an electrode for a lithium secondary battery which is less likely to be wrinkled or deformed due to charging and discharging, and a lithium secondary battery using the electrode.

[0009]

An electrode for a lithium secondary battery of the present invention is a lithium secondary battery formed by depositing an active material thin film that absorbs lithium by alloying with lithium on a current collector. The above-mentioned current collector is an electrode for use, which has 10 or more deformed portions per cm ² having a deformation amount of 5 to 20 μm in the thickness direction, and has an aperture ratio of 4% or less due to the deformed portions. It is characterized by being used as a body.

In the current collector of the present invention, the deformed portion whose deformation amount in the thickness direction is 5 to 20 μm is 1 per 1 cm ^2.
0 or more are formed. Since such deformed portions are formed so as to have the above distribution, when the stress generated by the expansion and contraction of the active material thin film during the charge / discharge reaction acts on the current collector, the deformed portions are collected in each deformed portion. This stress can be absorbed by the deformation of the electric body. Therefore, the deformation of the current collector is distributed to the respective deforming portions, and it is possible to prevent the current collector from being deformed by a large amount of deformation. Therefore, it is possible to prevent large wrinkles and deformation from occurring in the current collector due to the charge / discharge reaction.

As described above, the amount of deformation in the thickness direction of the deformed portion is 5 to 20 μm. The amount of deformation in the thickness direction is 5
When the thickness is less than μm, when stress acts on the current collector, the stress may not be absorbed due to the deformation of the deformed portion. Also,
When the amount of deformation in the thickness direction exceeds 20 μm, the deformation in the deformed portion becomes too large, and the energy density per volume when stored in the battery may decrease.

As described above, 10 or more, preferably 10 to 1000, deformed portions are formed per cm ² . When it is less than 10 per 1 cm ² , the number of deformed portions becomes too small, and when stress acts on the current collector, the stress cannot be absorbed as a small deformation in the deformed portion, resulting in large deformation in the deformed portion. May be If the number of deformed portions exceeds 1,000, it may be difficult to form the deformed portions, or the number of deformed portions may become too large, and the strength of the current collector may decrease.

In the present invention, the deformed portion may be formed with a notch or a hole. In such a case, a notch, a hole, or the like is formed so that the opening ratio of the deformed portion is 4% or less. That is, the notches, holes, etc. are formed such that the total area of the notches, holes, etc. is 4% or less of the total area of the current collector. Since the active material thin film is not deposited on the openings such as cuts or holes, the amount of the active material thin film deposited on the current collector can be secured by setting the opening ratio to 4% or less. It is possible to prevent the discharge capacity from decreasing.

The deformed portion having a notch can be formed by lath processing, for example. When forming the deformed portion by lathing, lathing is performed so that the aperture ratio is 4% or less, as described above.

Further, the deformed portion in the present invention may be a deformed portion in which a notch or the like is not formed, that is, the aperture ratio is 0%. Such a deformed portion can be formed by, for example, indentation processing. The indentation processing is processing performed by pressing a predetermined portion of the current collector to deform it.

In the present invention, the amount of deformation in the thickness direction at the deformed portion is the amount of deformation at the most deformed portion in the deformed portion, and the largest deformed portion at the surface of the current collector other than the deformed portion and the deformed portion. Is the distance in the thickness direction. In addition, the deformed portions are preferably formed so as to be uniformly dispersed on the current collector, and are preferably formed so as to have a certain regularity.

It is preferable that the current collector used in the present invention has a deformed portion formed on a current collector having irregularities formed on its surface. The surface roughness Ra of the current collector before forming the deformed portion is preferably 0.01 μm or more, more preferably 0.05 μm or more, and further preferably 0.1 μm or more. The upper limit of the surface roughness Ra of the current collector is not particularly limited, but it is generally 2 μm or less because those having a surface roughness Ra of more than 2 μm are difficult to obtain. Therefore, the surface roughness Ra of the current collector is 0.01 to 2 μm.
It is preferably m, and more preferably 0.05 to
It is 2 μm, and more preferably 0.1 to 2 μm.

The thickness of the current collector before forming the deformed portion is preferably 5 to 40 μm. If the thickness of the current collector is less than 5 μm, the strength of the current collector becomes weak, and the current collector may be broken during charge / discharge or assembly into a battery. Further, if the thickness of the current collector exceeds 40 μm, the workability in post-processing may be reduced, or the stress generated during charge / discharge may not be effectively dispersed.

In the present invention, the active material thin film deposited and formed on the current collector is not particularly limited as long as it is a thin film made of an active material that absorbs lithium by alloying with lithium. Examples of such an active material include silicon, germanium, tin, lead, zinc, magnesium, sodium, aluminum, potassium, indium and alloys thereof. Among these, an amorphous or microcrystalline thin film containing silicon as a main component is preferably used.

In the present invention, as a method for depositing an active material thin film, a method of moving and depositing atoms or ions from a gas phase or a liquid phase onto a substrate of a current collector is preferably used. Examples thereof include a CVD method, a sputtering method, a vapor deposition method, a thermal spraying method, and a plating method.

The current collector used in the present invention is preferably formed of a metal that does not alloy with lithium. Examples of such a material include copper, alloys containing copper, nickel, stainless steel and the like.

Further, in the present invention, it is preferable that the components of the current collector are diffused in the active material thin film. For example, when a silicon thin film is used as the active material thin film and a copper-containing current collector is used as the current collector, it is preferable that copper is diffused in the silicon thin film. Such diffusion of the current collector component can be promoted by heating. Therefore, the diffusion of the current collector component can be enhanced by raising the substrate temperature during thin film formation or by performing heat treatment after thin film formation.

When silicon or the like is used as the active material,
The component of the current collector preferably forms a solid solution in the thin film without forming an intermetallic compound with the thin film component. When the thin film component is silicon and the current collector component is copper, it is preferable that a solid solution of copper and silicon is formed without forming an intermetallic compound of silicon and copper in the thin film. Generally, if the current collector component is excessively diffused, an intermetallic compound is likely to be formed. Therefore, for example, when heat treatment is performed at a high temperature after forming a thin film, an intermetallic compound may be formed. Here, the intermetallic compound means a compound having a specific crystal structure in which metals are combined in a specific ratio.

By diffusing the current collector component in the active material thin film, the adhesion of the thin film to the current collector can be enhanced and the charge / discharge cycle characteristics can be improved. In the active material thin film of the present invention, it is preferable that a cut is formed in the thickness direction of the thin film by a charge / discharge reaction, and the thin film is separated into columnar shapes. By separating into a columnar shape, a void is formed around the columnar portion, and expansion / contraction of the volume of the active material thin film due to the charge / discharge reaction can be absorbed in this void portion, and the volume of the active material thin film can be absorbed. The stress due to expansion and contraction can be relieved. Therefore, peeling of the active material thin film from the current collector can be suppressed, and adhesion to the current collector can be maintained.

The charge / discharge when the active material thin film is separated into columns is performed slowly so that the thin film structure of the active material thin film does not change rapidly, the charge rate is lowered at the first time, or the charge rate is lowered. It is also possible to adopt a method of gradually increasing the value of.

Further, lithium may be previously occluded or added to the thin film of the present invention. Lithium
You may add when forming a thin film. That is, lithium may be added to the thin film by forming a thin film containing lithium. Further, after forming the thin film, lithium may be occluded or added to the thin film. Examples of a method of occluding or adding lithium to the thin film include a method of electrochemically occluding or adding lithium.

The thickness of the active material thin film of the present invention is not particularly limited, but may be, for example, 10 μm or less. Further, in order to obtain a high charge / discharge capacity, the thickness is preferably 1 μm or more.

The lithium secondary battery of the present invention is the above-mentioned present invention.
A negative electrode composed of the above electrodes, a positive electrode, and a non-aqueous electrolyte
It is characterized by that. For the lithium secondary battery of the present invention
The electrolyte solvent used is not particularly limited,
Ethylene carbonate, propylene carbonate, buty
Cyclic catalysts such as ren carbonate and vinylene carbonate
Carbonate, dimethyl carbonate, methyl ethyl carbonate
Carbonate such as carbonate and diethyl carbonate
A mixed solvent with a salt is exemplified. Also, the annular carbo
And 1,2-dimethoxyethane, 1,2-diethoxy
Ether solvents such as sietane and γ-butyrolacto
Mixed with chain esters such as amine, sulfolane, methyl acetate, etc.
A mixed solvent is also exemplified. The solute of the electrolyte is L
iPF₆, LiBF_Four, LiCF₃SO₃, LiN (CF ₃
SO₂)₂, LiN (C₂F_FiveSO₂)₂, LiN (CF₃S
O₂) (C_FourF₉SO₂), LiC (CF₃SO₂)₃, Li
C (C₂F_FiveSO₂)₃, LiAsF₆, LiClO_Four, Li
₂B_TenCl_Ten, Li₂B₁₂Cl₁₂Etc. and their mixtures
Is exemplified. As an electrolyte, polyethylene oxide
Sid, polyacrylonitrile, polyvinylidene fluoride
Gel polymer in which polymer electrolyte is impregnated with electrolyte
Electrolyte, LiI, Li₃An example is an inorganic solid electrolyte such as N
Shown. The electrolyte of the lithium secondary battery of the present invention is
And a Li compound as a solute that develops conductivity
The solvent to be dissolved / retained should be used when the battery is charged, discharged, or stored.
It can be used without restrictions unless it is disassembled with the voltage at hand.
Wear.

Examples of the positive electrode active material of the lithium secondary battery of the present invention include LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ and L.
iMnO ₂ , LiCo _0.5 Ni _0.5 O ₂ , LiNi _0.7 Co
Lithium-containing transition metal oxides such as _0.2 Mn _0.1 O ₂ ,
Examples include metal oxides that do not contain lithium, such as MnO ₂ . In addition to this, any substance that electrochemically inserts / desorbs lithium can be used without limitation.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to the following examples, but may be modified without departing from the scope of the invention. It can be implemented.

Example 1 [Production of Negative Electrode] As a current collector, electrolytic copper foil (thickness: 25 μm)
m) is subjected to lath processing to form notches and
The thing which formed the deformation part was used. FIG. 3 is an optical micrograph of the electrolytic copper foil subjected to this lath processing. As shown in FIG. 3, the length of the notch is about 500 μm, and the notch is formed at a repeating cycle of about 1000 μm in the direction perpendicular to the length direction of the notch (vertical direction in FIG. 3). 100 cuts (deformed portions) are formed per cm ² .

FIG. 1 is an enlarged sectional view showing an electrolytic copper foil subjected to lath processing. As shown in FIG. 1, a current collector 10
The notch 12 is formed in the groove, and the deformed portion 11 is formed by bending and deforming one side portion sandwiching the notch 12 in the thickness direction. The deformation amount h in the thickness direction of the deformed portion 11 is determined by the surface 10a of the region of the current collector 10 other than the deformed portion.
And the maximum deformation portion 11a of the deformation portion 11 in the thickness direction. The amount of deformation h of the current collector used here in the thickness direction is 14 μm. The deformation amount h is an average value of the entire current collector.

Surface roughness R of electrolytic copper foil before lath processing
When a was measured, the surface roughness Ra was 0.18 μm. Surface roughness Ra is a stylus type surface shape measuring instrument Dekt
Using akST (manufactured by Nippon Vacuum Technology Co., Ltd.), the measurement distance is 2.
The measurement was performed by setting it to 0 mm. The surface roughness Ra was calculated after the correction of the deflection. The correction values used for the deflection correction are low pass = 200 μm and high pass = 20 μm. The surface roughness Ra is a value calculated automatically.

The aperture ratio of the lathed electrolytic copper foil was about 3%. The aperture ratio is
It is a value converted by the area projected from the direction perpendicular to the current collector plane.

A silicon thin film was deposited by the RF sputtering method on the current collector made of the above-mentioned lathed electrolytic copper foil. Sputtering conditions are as follows: Sputtering gas (Ar gas) flow rate: 40 sccm, substrate temperature: room temperature (no heating), reaction pressure: 0.2 Pa (1.5 × 10 5)
^-3 Torr) and high frequency power: 2000 W.
The silicon thin film was deposited until its thickness was 6 μm.

Raman content of the obtained silicon thin film
When optical analysis was performed, it was 480 cm. ^-1Peaks in the vicinity are not detected
It was put out, but 520 cm^-1Is a nearby peak not detected?
It was. From this, the obtained silicon thin film is amorphous
It was confirmed that it was a recon thin film.

The electrolytic copper foil on which the amorphous silicon thin film was formed was cut out into a size of 2 cm × 2 cm to obtain an electrode a1.
FIG. 2 is an optical micrograph showing the electrode a1. As is clear from FIG. 2, even after the amorphous silicon thin film was formed, the appearance of the cut state and the aperture ratio in the electrolytic copper foil was hardly changed. The line AA 'shown in FIG. 2 indicates the sectional direction in the sectional view of FIG.

For comparison, an amorphous silicon thin film was formed in the same manner as the electrode a1 except that an electrolytic copper foil that had not been lathed was used as a current collector.
It was cut out to a size of cm to obtain an electrode b1.

Both the electrodes a1 and b1 are made of silicon.
The atomic density converted from the weight density and the film thickness is 4.0 × 10.^{twenty two}
cm^-3And the value of ordinary crystalline silicon is 5.0 × 10^{twenty two}
cm ^-3Was about 80%.

Further, as a comparison, 90 parts by weight of a commercially available single crystal silicon powder (particle diameter 10 μm) and 10 parts by weight of polytetrafluoroethylene as a binder were mixed,
This was pressed by a die having a diameter of 17 mm and pressure-molded to produce a pellet-shaped electrode c1.

[Preparation of Positive Electrode] Li ₂ CO ₃ as a starting material
And CoCO ₃ , the atomic ratio of Li: Co is 1: 1.
And weigh it so that
After press-molding with a m die, press in air 8
It was fired at 00 ° C. for 24 hours to obtain a fired body of LiCoO ₂ . This was ground in a mortar until the average particle size became 20 μm.

80 parts by weight of the obtained LiCoO ₂ powder,
10 parts by weight of acetylene black as a conductive agent and 10 parts by weight of polytetrafluoroethylene as a binder were mixed and pressed with a die having a diameter of 17 mm and pressure-molded to obtain a pellet-shaped positive electrode. It was made.

[Preparation of Electrolyte Solution] LiPF 6 was added to an equal volume mixed solvent of ethylene carbonate and diethyl carbonate.
₆ mol was dissolved in 1 mol / liter to prepare an electrolytic solution, which was used in the following battery preparation.

[Production of Battery] Using the above electrodes a1, b1 and c1 as a negative electrode and using the above positive electrode and an electrolytic solution,
A flat type lithium secondary battery was produced.

FIG. 5 is a sectional view showing the manufactured lithium secondary battery. As shown in FIG. 5, the lithium secondary battery includes a positive electrode 1, a negative electrode 2, a separator 3, a positive electrode can 4, a negative electrode can 5, a positive electrode current collector 6, a negative electrode current collector 7 and a polypropylene insulating packing 8. Become.

The positive electrode 1 and the negative electrode 2 face each other with the separator 3 in between. These are housed in a battery case formed by the positive electrode can 4 and the negative electrode can 5. The positive electrode 1 is connected to the positive electrode can 4 via the positive electrode current collector 6, and the negative electrode 2 is connected to the negative electrode can 5 via the negative electrode current collector 7 to provide a structure capable of charging and discharging as a secondary battery. Has become. A battery using the electrode a1 as a negative electrode was designated as a battery A1, a battery using the electrode b1 as a negative electrode was designated as a battery B1, and a battery using the electrode c1 as a negative electrode was designated as a battery C1.

[Measurement of Charge / Discharge Cycle Life Characteristics] The charge / discharge cycle life characteristics of the above batteries A1, B1 and C1 were evaluated. The battery was charged at 25 ° C. with a current value of 100 μA until the negative electrode capacity reached 2000 mAh / g and then discharged, and this was regarded as one cycle of charging / discharging.
The capacity retention rate at the 0th cycle was measured. In addition, 2000
For battery C1 that was not charged to mAh / g,
A cycle test was performed by discharging the battery after charging it to 4.2V.

Further, the thickness of the negative electrode before and after charge and discharge was measured with a micrometer to obtain the apparent thickness of the negative electrode before and after charge and discharge. Table 1 shows the apparent thickness of the negative electrode before and after charge and discharge and the capacity retention rate at the 50th cycle.

[0049]

[Table 1]

As is clear from the results shown in Table 1, the batteries A1 and B1 using the electrode formed by depositing the silicon thin film on the current collector as the negative electrode were the batteries C1 using the silicon powder as the negative electrode active material. Shows better charge / discharge cycle life characteristics. In addition, the battery A1 according to the present invention
Indicates that the increase in the thickness of the negative electrode after charging / discharging is smaller than that of the battery B1. This is because the deformation in the thickness direction of the current collector due to charging and discharging was dispersed by using the current collector in which the deformed portion was formed in a predetermined distribution, and the amount of deformation in the thickness direction was suppressed. Seem. Therefore, the electrode a1
By using, the energy density of the battery can be increased.

When the electrode a1 in the battery A1 after charging / discharging was observed with a scanning electron microscope, it was confirmed that a cut was formed in the thickness direction of the silicon thin film, and the silicon thin film was separated into columns by the cut. It was In addition, although the cut was formed in the thickness direction, it was hardly formed in the surface direction, and the bottom of the columnar portion was in close contact with the copper foil serving as the current collector.

SIMS is applied in the depth direction of the silicon thin film.
As a result of the analysis, copper (Cu) which is a component of the current collector is diffused in the silicon thin film in the vicinity of the current collector, and copper (C) which is a component of the current collector becomes closer to the surface of the silicon thin film.
It was confirmed that the concentration of u) had decreased. Further, since the concentration of copper (Cu) is continuously changing, a solid solution of silicon and copper is formed in the region where copper (Cu) is diffused, not an intermetallic compound of silicon and copper. It is thought that

Example 2 [Fabrication of Negative Electrode] As the current collector, the electrolytic copper foil used in Example 1 (before lath processing) was subjected to indentation processing. The indentation process was performed by pressing.
FIG. 4 is a cross-sectional view showing an electrolytic copper foil that has been indented. As shown in FIG. 4, the current collector 22 has deformed portions 21 and 22 formed by indentation processing. This deforming portion 21
No cuts or the like are formed in the lines 22 and 22. As shown in FIG. 4, the deformable portions 21 and 22 are formed so as to alternately project in opposite directions. The deformation amount h ₁ of the deforming portion 21 in the thickness direction is 7 μm, and the deformation amount h ₂ of the deforming portion 22 in the thickness direction is 7 μm.

Indentation-processed electrolytic copper foil, 1 cm
^The deformed portions are formed so that there are about 100 deformed portions per ² . In addition, since the notch or the like is not formed in the deformed portion, the aperture ratio is 0%.

This indented electrolytic copper foil was used as a current collector, and an amorphous silicon thin film having a thickness of about 6 μm was formed on the current collector by RF sputtering in the same manner as the electrode a1 of Example 1. To form an electrode a2.

[Production of Battery] The above-mentioned electrode a2 is used as a negative electrode.
A lithium secondary battery was produced in the same manner as in Example 1 except that the above was used to obtain a battery A2.

[Measurement of Charge / Discharge Cycle Life Characteristics] In the same manner as in Example 1, the capacity retention rate at the 50th cycle of the battery A2 was determined, and the results are shown in Table 2. Further, the apparent thickness of the negative electrode before and after charge / discharge was measured and is shown in Table 2. In addition, Table 2 also shows the result of the battery B1.

[0058]

[Table 2]

As is clear from the results shown in Table 2, the battery A2 using the electrode a2 also provided good charge / discharge cycle life characteristics, and compared with the battery B1, the thickness of the negative electrode before and after charging / discharging. The increase is getting smaller.
Therefore, the energy density of the battery can be increased by using the electrode a2.

In each of the above embodiments, the deformed portion is formed on the current collector before depositing the active material thin film, but the present invention is not limited to this, and the active material is formed on the current collector. After the thin film is deposited and formed, the current collector may be processed to form the deformed portion.

[0061]

According to the present invention, an electrode for a lithium secondary battery which is less likely to be wrinkled or deformed due to charging and discharging can be obtained. By using this electrode for a lithium secondary battery, a lithium secondary battery can be obtained. The energy density of can be increased.

[Brief description of drawings]

FIG. 1 is a sectional view showing the shape of a deformed portion of a current collector used in Example 1 of the present invention.

FIG. 2 is an optical micrograph showing a state after depositing a silicon thin film on a current collector having a deformed portion.

FIG. 3 is an optical micrograph showing a current collector having a deformed portion.

FIG. 4 is a cross-sectional view showing a deformed portion of a current collector used in Example 2 of the present invention.

FIG. 5 is a cross-sectional view showing a lithium secondary battery manufactured in an example of the present invention.

[Explanation of symbols]

10 ... deformation amount to the current collector 11 ... deformable portion 12 ... slit 20 ... collector 21 ... deformation part h, h _1, h ₂ ... thickness direction of the deformation portion

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hisaki Tarui             2-5-3 Keihan Hondori, Moriguchi City, Osaka Prefecture             Within Yo Denki Co., Ltd. F-term (reference) 5H017 AA03 AS02 AS10 BB06 CC03                       DD01 DD08 HH03                 5H029 AJ03 AJ11 AK02 AK03 AL11                       AL13 AM00 AM02 AM03 AM04                       AM05 AM07 AM12 AM16 BJ03                       CJ03 CJ25 DJ07 DJ14 EJ01                 5H050 AA08 BA17 CA05 CA08 CA09                       CB11 DA03 DA06 DA07 FA15                       FA19 FA20 GA24 HA04

Claims (10)

[Claims] 1. An electrode for a lithium secondary battery, which is formed by depositing an active material thin film that absorbs lithium by alloying with lithium on a current collector, the deformation amount in the thickness direction being 5 to 5. Deformation part of 20 μm is 1c
An electrode for a lithium secondary battery, characterized in that 10 or more electrodes are formed per m ² , and a current collector having an opening ratio of 4% or less by the deformed portion is used as the current collector. 2. The electrode for a lithium secondary battery according to claim 1, wherein a notch is formed in the deformed portion. 3. The electrode for a lithium secondary battery according to claim 2, wherein the deformed portion is formed by lath processing. 4. The electrode for a lithium secondary battery according to claim 1, wherein the deformed portion is formed by indentation processing. 5. The lithium secondary battery according to claim 1, wherein a surface roughness Ra of the current collector before forming the deformed portion is 0.01 μm or more. Electrodes. 6. The electrode for a lithium secondary battery according to claim 1, wherein the thickness of the current collector before forming the deformed portion is 5 to 40 μm. 7. The electrode for a lithium secondary battery according to claim 1, wherein the active material thin film is an amorphous or microcrystalline thin film containing silicon as a main component. 8. The component of the current collector is diffused in the active material thin film, according to any one of claims 1 to 7.
An electrode for a lithium secondary battery according to item. 9. The electrode for a lithium secondary battery according to claim 1, wherein the active material thin film is separated into columns by a cut formed in the thickness direction. 10. A lithium secondary battery comprising a negative electrode comprising the electrode according to any one of claims 1 to 9, a positive electrode, and a non-aqueous electrolyte.