JP2009231072A - Lithium secondary battery and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a lithium secondary battery which excels in charge and discharge cycle characteristics, and has high volume energy density, and to obtain its manufacturing method. <P>SOLUTION: The lithium secondary battery uses an electrode formed by depositing on a collector 20 a thin film 22 consisting of an active material storing or emitting lithium, wherein the ten-point average roughness Rz of the front surface 21 of the collector 20 on which the active material thin film 22 is formed is ≥1.5, and the maximum height Ry is <1.39 times of the ten-point average roughness Rz. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  In recent years, many mobile communication devices such as mobile phones and laptop computers and portable electronic devices have appeared, and lithium secondary batteries are mainly used as the power source. Lithium secondary batteries have a large energy density compared to other secondary batteries such as nickel cadmium batteries, but as the mobile communication devices and portable electronic devices become smaller and lighter, their energy density and cycle characteristics. Improvement is demanded.

In current general lithium secondary batteries, a carbon material typified by graphite is used as a negative electrode material. However, in the negative electrode material made of graphite, lithium can be inserted only up to the composition of LiC ₆ , and the theoretical capacity is 372 mAh / g, which is an obstacle to high capacity.

  A lithium secondary battery using aluminum, silicon, or tin alloyed with lithium as a negative electrode active material having a high energy density per weight and volume has been reported. Among these, silicon is particularly promising as a negative electrode material for a battery having a large capacity and high capacity, and various secondary batteries using this as a negative electrode have been proposed.

  However, this type of alloy negative electrode has a problem in that stress is generated between the negative electrode and the current collector due to a large volume change during charging and discharging, causing the active material thin film to fall off, wrinkle of the electrode, and deflection. .

  In order to solve this problem, a thin film such as a vapor deposition method or a sputtering method is used on a current collector whose surface is roughened as an electrode for a lithium secondary battery using silicon or the like as an electrode active material and exhibiting 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 by a forming method has been proposed (Patent Document 1). In such a lithium secondary battery electrode, the thin film on the current collector has a columnar shape, which relieves stress during expansion and contraction of the active material due to charge and discharge, and the active material thin film from the current collector Can be prevented from falling off.

However, there is a need for a lithium secondary battery that is further excellent in charge / discharge cycle characteristics and has a high volumetric energy density.
JP 2002-83594 A

  The objective of this invention is providing the lithium secondary battery which is excellent in charging / discharging cycling characteristics, and has a high volume energy density, and its manufacturing method.

  The present invention relates to a surface of a current collector on which an active material thin film is formed in a lithium secondary battery using an electrode formed by depositing a thin film made of an active material that occludes and releases lithium on the current collector. The ten-point average roughness Rz is 1.5 or more and the maximum height Ry is less than 1.39 times the ten-point average roughness Rz.

  According to the present invention, when the ten-point average roughness Rz of the surface of the current collector on which the active material thin film is formed is 1.5 or more, excellent charge / discharge cycle characteristics can be obtained. Further, according to the present invention, by making the maximum height Ry less than 1.39 times the ten-point average roughness Rz, it is possible to obtain further excellent charge / discharge cycle characteristics and increase the volume energy density. it can. The maximum height Ry is more preferably 1.30 times or less of the ten-point average roughness Rz.

  FIG. 3 is a schematic diagram for explaining the maximum height Ry. The maximum height Ry is defined in Japanese Industrial Standard (JIS B0601-1994). As shown in FIG. 3, the maximum height Ry is a distance between the maximum peak and the maximum valley at the reference length L.

  FIG. 4 is a schematic diagram for explaining the ten-point average roughness Rz. The ten-point average roughness Rz is defined in Japanese Industrial Standard (JIS B0601-1994). As shown in FIG. 4, the ten-point average roughness Rz is the elevation of the highest peak from the highest peak to the fifth peak of the extracted part corresponding to the reference length l, and the extracted part corresponding to the reference length l. From the elevation of the bottom valley from the lowest valley bottom to the fifth, it can be obtained by the following equation.

Rz = (| _Yp1 + _Yp2 + _Yp3 + _Yp4 + _Yp5 | + | _Yv1 + _Yv2 + _Yv3 + _Yv4 + _Yv5 |) / 5
Y _p1 , Y _p2 , Y _p3 , Y _p4 , Y _p5 : Altitudes of the extracted parts corresponding to the reference length l from the highest peak to the fifth peak Y _v1 , Y _v2 , Y _v3 , Y _v4 , Y _v5 : Elevation of the bottom from the lowest valley bottom to the fifth in the extracted portion corresponding to the reference length l

  FIG. 5 is a schematic cross-sectional view showing an electrode formed by depositing an active material thin film on a current collector having an uneven surface. As shown in FIG. 5, irregularities are formed on the surface 21 of the current collector 20. When the active material thin film 22 is deposited and formed on the surface 21 of the current collector 20 on which the unevenness is formed, the surface 23 of the active material thin film 22 corresponds to the unevenness of the surface 21 of the current collector 20. Unevenness is formed.

  In addition, a low density region 24 is formed in the thickness direction of the active material thin film 22 connecting the valley 23 a on the surface of the active material thin film 22 and the valley 21 a on the surface 21 of the current collector 20. As the active material thin film occludes and releases lithium by charging and discharging, the volume of the active material thin film 22 expands and contracts. Due to the expansion and contraction of the volume of the active material thin film 22, a cut is formed along the low density region 24, and the active material thin film 22 is separated by the cut and a columnar structure is formed. Thus, the active material thin film in the present invention is preferably separated into a columnar shape by the cuts formed in the thickness direction, and the bottom of the columnar portion is preferably in close contact with the current collector. By forming such a columnar structure, a change in volume of the active material thin film can be absorbed by the surrounding space portion, and stress due to expansion and contraction of the volume of the active material thin film can be relieved. For this reason, it is possible to prevent the active material thin film from falling off the current collector, and to obtain excellent charge / discharge cycle characteristics.

  According to the present invention, the 10-point average roughness Rz of the surface 21 of the current collector 20 shown in FIG. 5 is 1.5 or more, and the maximum height Ry is less than 1.39 times the 10-point average roughness Rz. Thus, even better charge / discharge cycle characteristics can be obtained.

  The maximum height Ry of the current collector surface in the present invention can be adjusted, for example, by subjecting the current collector to pressure treatment in the thickness direction. Such pressure treatment may be performed before the active material thin film is formed on the current collector, or may be performed after the active material thin film is formed. Therefore, in the present invention, when the current collector is pressure-treated in the thickness direction, the maximum height Ry is less than 1.39 times, preferably 1.30 times or less, of the ten-point average roughness Rz. It is preferable to adjust so that.

  In the present invention, the current collector is a current collector in which a roughened layer made of a material having a lower tensile strength than the metal foil is provided on the metal foil, and an active material thin film is formed on the roughened layer. Is preferably formed. The current collector provided with such a roughened layer is pressed in the thickness direction as described above, so that the roughened layer made of a material having a relatively low tensile strength can be pressed. It can be easily deformed, whereby the maximum height Ry can be easily adjusted. Examples of a method for forming such a roughened layer include a plating method and a vapor phase growth method. Examples of the plating method include an electrolytic plating method and an electroless plating method. Examples of the vapor phase growth method include a sputtering method, a CVD method, and a vapor deposition method.

  Examples of the surface roughening method by plating include a method in which a plating film mainly composed of copper such as copper or copper-zinc alloy is formed on a substrate made of copper foil or copper alloy foil.

  As a method of roughening by electrolytic plating, a roughening method by plating generally used for copper foil for printed circuits can be mentioned. Specifically, after forming granular copper by so-called "burn plating", "cover plating" is performed on this granular copper plating layer so as not to impair the uneven shape, and substantially An example is a roughening method in which a smooth plating layer is made into a volume so that granular copper is so-called bumpy copper.

  Examples of the current collector used in the present invention include a current collector made of copper foil or copper alloy foil. Although it will not specifically limit if it is an alloy containing copper as a copper alloy, For example, Cu-Ag type alloy, Cu-Te, Cu-Mg, Cu-Sn, Cu-Si, Cu-Mn, Cu -Be-Co, Cu-Ti, Cu-Ni-Si, Cu-Cr, Cu-Zr, Cu-Fe, Cu-Al, Cu-Zn, and Cu-Co-based alloys.

In addition, in order to prevent the mechanical strength from being lowered due to temperature changes when forming the active material thin film, the heat resistant copper can prevent the mechanical strength from being lowered due to temperature changes and ensure sufficient conductivity. It is preferable to use an alloy foil. Here, the heat resistant copper alloy is a copper alloy having a tensile strength of 300 MPa / cm ² or more after annealing at 200 ° C. for 1 hour. Examples of such heat resistant copper alloys include heat resistant copper alloys as shown in Table 1.

  In Table 1, “%” means “% by weight”.

  In addition, as described above, when a roughened layer is formed on a metal foil, a plating method or a vapor phase growth method is used on the above copper foil, copper alloy foil, or heat resistant copper alloy foil. A roughened layer can be formed by, for example. In the present invention, the metal foil includes a foil made of a single metal and a foil made of an alloy.

  Further, as a method for roughening the surface of the current collector, the surface may be roughened by etching or polishing directly on the metal foil.

  The active material thin film in the present invention is a thin film that occludes / releases lithium, and is preferably an active material that occludes lithium by alloying lithium. Examples of such an active material include silicon, germanium, tin, lead, zinc, magnesium, sodium, aluminum, potassium, and indium. Among these, silicon is preferably used because of its high theoretical capacity. Therefore, the active material thin film used in the present invention is preferably a thin film mainly composed of silicon. The thin film which has silicon as a main component here is a thin film which contains 50 atomic% or more of silicon.

  In the present invention, the active material thin film is preferably an amorphous thin film or a microcrystalline thin film. Therefore, an amorphous silicon thin film or a microcrystalline silicon thin film is particularly preferable.

  In the present invention, the active material thin film can be formed by a vapor deposition method, a sputtering method, a CVD method, or a thermal spraying method. Among these methods, it is preferable to form by vapor deposition.

  The electrode in the present invention is generally used as a negative electrode. However, for example, it can also be used as a positive electrode by combining with an electrode such as lithium metal.

  When the electrode in the present invention is used as a negative electrode, a positive electrode using a lithium-containing transition metal composite oxide such as lithium cobaltate generally used in lithium secondary batteries as a positive electrode can be used as the positive electrode. . Moreover, if it can use as a positive electrode active material of a lithium secondary battery, it can use without a restriction | limiting in particular.

  In addition, the nonaqueous electrolyte used in the present invention can be used without particular limitation as long as it can be used as a nonaqueous electrolyte for a lithium secondary battery.

  The production method of the present invention is a method capable of producing the lithium secondary battery of the present invention, and includes a step of preparing a current collector and a step of depositing and forming an active material thin film on the current collector It is characterized by comprising.

  According to the production method of the present invention, it is possible to efficiently produce a lithium secondary battery having excellent charge / discharge cycle characteristics and high volume energy density.

  The production method of the present invention preferably further includes a step of applying a pressure treatment in the thickness direction of the current collector before and / or after the formation of the active material thin film. By such a pressurizing step, the maximum height Ry can be adjusted as described above.

  In the production process of the present invention, the step of preparing the current collector may include the step of forming the roughened layer on the metal foil. As described above, since the roughened layer can be easily deformed by using the current collector provided with the roughened layer made of a material having a lower tensile strength than the metal foil, The ratio between the maximum height Ry and the ten-point average roughness Rz can be adjusted more easily.

  ADVANTAGE OF THE INVENTION According to this invention, it can be set as the lithium secondary battery which is excellent in charging / discharging cycling characteristics and has a high volume energy density.

  According to the production method of the present invention, a lithium secondary battery having excellent charge / discharge cycle characteristics and a high volumetric energy density can be produced efficiently.

  Hereinafter, the present invention will be described with reference to specific examples. However, the present invention is not limited to the following examples, and can be appropriately modified and implemented without departing from the scope of the present invention. .

  In the following examples and comparative examples, a negative electrode, a positive electrode, and a nonaqueous electrolyte were produced as follows, and a lithium secondary battery was produced using these. Moreover, the produced lithium secondary battery was subjected to a charge / discharge cycle test as follows.

(1) Production of negative electrode An amorphous silicon thin film was deposited on the current collector using the vapor deposition apparatus shown in FIG.

  An electron beam gun 5 and a crucible 3 are provided in the vacuum chamber 8 of the thin film forming apparatus shown in FIG. The crucible 3 is a crucible for melting the vapor deposition material 4. The current collector 1 is wound around the roller 6 and the roller 7, and along the outer peripheral surface of the support roller 2 positioned between the roller 6 and the roller 7, the roller 6 is switched to the roller 7, or the roller 7 is switched to the roller 7. Go to 6.

  In the region facing the crucible 3, a silicon thin film is formed on the current collector 1 by electron beam evaporation. In the electron beam evaporation, the electron beam C emitted from the electron beam gun 5 is applied to the evaporation material 4. As the vapor deposition material 4, single crystal silicon is used. As the crucible 3, a water-cooled copper crucible is used.

  First, the current collector 1 is wound around the roller 6, the current collector 1 is moved in the direction of arrow A, and the surface of the current collector 1 is opposed to the crucible 5 while being wound by the roller 7. A silicon thin film was deposited in the region to be used. Next, the current collector 1 wound around the roller 7 was moved in the direction opposite to the arrow A, and the silicon thin film was deposited again on the same region of the current collector 1 while being wound around the roller 6.

  Table 2 shows the conditions for forming the silicon thin film by the electron beam evaporation method. The feeding speed of the current collector 1 was 0.26 m / min, and a silicon thin film was deposited twice in an area of 15 m in the feeding direction of the current collector.

  As described above, a silicon thin film was deposited on one surface of the current collector. The current collector 1 on which the silicon thin film was deposited was wound around a roller 7 and taken out from the thin film forming apparatus while being in a roll state. In the current collector roll taken out from the thin film forming apparatus, a silicon thin film is formed only on the inner surface side of the roll.

  Next, after the roll taken out from the thin film forming apparatus was reversed using the roll reversing device, the inner surface side and the outer surface side of the base material were reversed, and this roll was attached to the roller 6 of the thin film forming apparatus. In the roll at this time, a silicon thin film is formed only on the roll outer surface side.

  Next, the silicon thin film was deposited on the surface on which the silicon thin film was not formed by the same procedure as described above.

  The cross section of the current collector on which the silicon thin film was deposited was observed with a scanning electron microscope (SEM). When the thickness of the silicon thin film was measured, a silicon thin film having a thickness of about 16 μm was deposited on both sides of the current collector. Accordingly, the deposition rate of the silicon thin film is about 2.1 μm · m / min.

  As described above, the electrode in which the silicon thin film was deposited on both surfaces of the current collector was cut into a strip shape, and a nickel lead was attached thereto to complete the negative electrode.

(2) Preparation of positive electrode 90 parts by weight of LiCoO ₂ powder and 5 parts by weight of artificial graphite powder as a conductive agent in a 5% by weight N-methylpyrrolidone solution containing 5 parts by weight of polytetrafluoroethylene as a binder It mixed and it was set as the positive mix slurry. This slurry was applied to an aluminum foil as a positive electrode current collector by a doctor blade method, dried and rolled. The electrode was cut into a strip shape, and an aluminum lead was attached to complete the positive electrode.

(3) Preparation of non-aqueous electrolyte LiPF ₆ was dissolved in a solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 3: 7, and a non-aqueous electrolyte was prepared.

(4) Production of Lithium Secondary Battery A cylindrical lithium secondary battery shown in FIG. 2 was produced. As shown in FIG. 2, a separator 3 is sandwiched between the positive electrode 1 and the negative electrode 2, and another separator 3 is further disposed outside the positive electrode 1, wound in a spiral shape in this state, and inserted into a battery can. . The negative electrode 2 is electrically connected to the negative electrode can 4 by a lead, and the positive electrode 1 is electrically connected to the positive electrode terminal 5 by a lead. A non-aqueous electrolyte is injected into the battery can.

(5) Charging / discharging cycle test The charging / discharging cycle test of the produced battery was performed on charging / discharging conditions shown in Table 3.

  The maximum discharge capacity in all cycles was taken as 100%, and the discharge capacity maintenance rate at the 50th cycle was taken as the capacity maintenance rate (%).

(Comparative experiment)
As Comparative Example 1, a negative electrode was produced as described above using a Corson alloy rolled foil having a thickness of 18 μm as a current collector, and a lithium secondary battery was produced as described above using this negative electrode.

  As Comparative Examples 2 to 5, copper was deposited as a roughened layer on both sides of a Corson alloy rolled foil having a thickness of 18 μm by a plating method. By changing the plating conditions, four types of roughened layers were formed. Using the alloy foil thus formed with the roughened layer as a current collector, a negative electrode was produced as described above, and a lithium secondary battery was produced using these negative electrodes.

  About each lithium secondary battery produced as mentioned above, the charging / discharging cycle test was done as mentioned above, and the capacity | capacitance maintenance factor was calculated | required.

  Table 4 shows the ten-point average roughness Rz, the maximum height Ry, the ratio of Ry / Rz of the current collectors used in Comparative Examples 1 to 5, and the measured capacity retention ratio.

  As shown in Table 4, in Comparative Examples 2 to 5, the ten-point average roughness Rz and the maximum height Ry are higher than those in Comparative Example 1 in which the roughened layer is not formed. In Comparative Examples 2 to 5, the ten-point average roughness Rz and the maximum height Ry are increased by increasing the current density under the plating conditions.

  As is clear from the results shown in Table 4, in Comparative Example 1 in which the roughened layer was not formed, the capacity retention rate was 0.0%, and good charge / discharge cycle characteristics were not obtained. . This is probably because the columnar structure was not formed in the silicon thin film, and the active material thin film was dropped from the current collector due to the volume change of the active material thin film due to charge / discharge.

  On the other hand, in Comparative Examples 2 to 5, better charge / discharge cycle characteristics are obtained as compared with Comparative Example 1. In particular, good charge / discharge cycle characteristics are obtained in Comparative Example 4 and Comparative Example 5 in which the ten-point average roughness Rz is 1.5 or more.

  Further, in Comparative Examples 2 to 5, the ten-point average roughness Rz is gradually increased, but the maximum height Ry is also gradually increased, so the ratio of Ry / Rz has not changed much. I understand that.

(Experiment 1)
In Comparative Example 6 and Examples 1 to 3 below, a negative electrode was produced using a current collector having a ten-point average roughness Rz and a maximum height Ry comparable to those in Comparative Example 4.

  In Examples 1 to 3, after a silicon thin film was deposited on the current collector, it was pressed through a rolling roll before being cut into a strip shape. In the order of Example 1, Example 2, and Example 3, pressure treatment was performed so that a stronger pressure was applied.

  In Comparative Example 6, a silicon thin film was deposited on the current collector, and then used as a negative electrode without being subjected to pressure treatment.

[Measurement of thickness with micrometer]
Electrode area 0.5 m ^2, thickness was measured with a micrometer. Table 5 shows the average value, the maximum value, the minimum value, and the dispersion value of the thickness.

[Measurement of Rz and Ry]
The cross section of each negative electrode was observed with an SEM, and Rz and Ry were determined from the obtained SEM images. In the JIS standard, the reference length 1 for Ry and Rz is determined to be 0.25 μm when Ry and Rz are in the range of 0.1 to 0.5 μm. When it is in the range of 5 to 10.0 μm, it is determined to be 0.8 μm. Therefore, in Examples 1 to 3 and Comparative Example 6, the reference length l is set to 0.8 μm.

  In addition, Rz and Ry of Comparative Examples 1 to 5 in the comparative experiment are also measured by SEM observation of the cross section of the negative electrode as described above. For Comparative Example 1, the reference length 1 is 0.25 μm, and for Comparative Examples 2 to 5, the reference length 1 is 0.8 μm.

(Measurement of tensile strength)
Tensile strength was measured for the Corson alloy foil used as the substrate of the current collector. Since the current collector is heated when depositing the silicon thin film, the Corson alloy foil was heat-treated at 200 ° C. for 1 hour in a vacuum atmosphere (1 Pa or less) in order to know the change in tensile strength after the heating. . The tensile strength before and after heat treatment was determined.

As a result, before the heat treatment was 828MPa / cm ^2, after the heat treatment was 863MPa / cm ^2.

  Moreover, in order to obtain | require the tensile strength of the roughening layer formed on the Corson alloy foil by the plating method, the tensile strength of the pure copper foil was measured. This pure copper foil was also heat-treated in the same manner as described above, and the tensile strength before and after the heat treatment was determined.

As a result, the strength before the heat treatment was 444 MPa / cm ² and the tensile strength after the heat treatment was 238 MPa / cm ² .

[Can insertion process]
When producing a lithium secondary battery, the yield in the can insertion process when inserting the wound body in which the negative electrode, the positive electrode, and the separator were spirally wound as described above into the battery can (negative electrode can) was determined. When inserting the wound body into the can, the ratio of the one that could be inserted without being caught in the can and the one that was caught in the can and part of the wound body was destroyed was determined and used as the yield. About each Example and the comparative example, 20 can insertion processes were performed, respectively, and the ratio with respect to the whole of what was able to insert without being caught in a can was shown in Table 5 as a yield. As the battery can, an aluminum can having an outer diameter of 14.0 mm, an inner diameter of 13.4 mm, a thickness of the can wall of 0.3 mm, and a height of 430 mm (including a positive electrode terminal) was used.

(Charge / discharge test)
In the same manner as described above, the batteries of Examples 1 to 3 and Comparative Example 6 were subjected to charge / discharge tests, and the capacity retention ratios are shown in Table 5.

  As is apparent from the results shown in Table 5, according to the present invention, in Examples 1 to 3, in which the ten-point average roughness Rz is 1.5 or more and Ry / Rz is less than 1.39, the high capacity The maintenance rate is obtained. In Examples 2 and 3 in which Ry / Rz is 1.30 or less, even better charge / discharge cycle characteristics are obtained.

  In addition, Examples 1 to 3 according to the present invention have higher yield in the can insertion process than Comparative Example 6, and according to the present invention, the yield can be increased, and the lithium secondary having a high volumetric energy density. It can be seen that the battery can be manufactured.

  Moreover, in Examples 1-3, the maximum height Ry is obtained by using a current collector provided with a roughened layer made of copper having a tensile strength lower than that of the corson alloy foil serving as a base, and subjecting this to pressure treatment. Is adjusted to be less than 1.39 times the ten-point average roughness Rz. Therefore, it can be seen that by using such a current collector, the maximum height Ry can be easily adjusted, and a lithium secondary battery having excellent charge / discharge cycle characteristics and high volume energy density can be produced.

The schematic diagram which shows the vapor deposition apparatus used in the Example of this invention. The disassembled perspective view which shows the cylindrical lithium secondary battery produced in the Example of this invention. The figure for demonstrating maximum height Ry. The figure for demonstrating ten-point average roughness Rz. The typical sectional view for explaining the structure of the electrode in the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Current collector 2 ... Support roller 3 ... Crucible 4 ... Vapor deposition material 5 ... Electron beam gun 6, 7 ... Roller 8 ... Vacuum chamber 11 ... Positive electrode 12 ... Negative electrode 13 ... Separator 14 ... Electrode can (negative electrode can)
DESCRIPTION OF SYMBOLS 15 ... Positive electrode terminal 20 ... Current collector 21 ... Current collector surface 21a ... Current collector surface trough 22 ... Active material thin film 23 ... Active material thin film surface 23a ... Active material thin film surface trough 24 ... Low density area

Claims (14)

In a lithium secondary battery using an electrode formed by depositing a thin film made of an active material that occludes and releases lithium on a current collector,
The 10-point average roughness Rz of the surface of the current collector on which the active material thin film is formed is 1.5 or more, and the maximum height Ry is less than 1.39 times the 10-point average roughness Rz. A lithium secondary battery characterized by that.   2. The lithium secondary battery according to claim 1, wherein the maximum height Ry is 1.30 times or less of the ten-point average roughness Rz.   The current collector is adjusted such that the maximum height Ry is less than 1.39 times the ten-point average roughness Rz by being subjected to pressure treatment in the thickness direction thereof. The lithium secondary battery according to 1 or 2.   The current collector is a current collector provided with a roughened layer made of a material having a lower tensile strength than the metal foil on the metal foil, and the active material thin film is formed on the roughened layer. The lithium secondary battery according to claim 1, wherein the lithium secondary battery is a lithium secondary battery.   The lithium secondary battery according to claim 4, wherein the roughened layer is formed by a plating method.   The lithium secondary battery according to claim 4, wherein the roughened layer contains copper as a main component.   The lithium secondary battery according to any one of claims 4 to 6, wherein the metal foil is a heat-resistant copper alloy foil.   The active material thin film is separated into a columnar shape by a cut formed in the thickness direction thereof, and the bottom of the columnar portion is in close contact with the current collector. The lithium secondary battery according to claim 1.   The lithium secondary battery according to claim 1, wherein the active material thin film is a thin film containing silicon as a main component.   The lithium secondary battery according to claim 1, wherein the active material thin film is formed on a current collector by a vapor deposition method.   The lithium secondary battery according to claim 1, wherein the electrode is a negative electrode. A method for producing the lithium secondary battery according to claim 1,
Preparing the current collector;
And a step of depositing and forming the active material thin film on the current collector.   The method of manufacturing a lithium secondary battery according to claim 12, further comprising a step of performing a pressure treatment in a thickness direction of the current collector before and / or after the formation of the active material thin film.   The method of manufacturing a lithium secondary battery according to claim 12 or 13, wherein the step of preparing the current collector includes a step of forming the roughened layer on the metal foil.

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