WO2001029912A1

WO2001029912A1 - Electrode for lithium cell and lithium secondary cell

Info

Publication number: WO2001029912A1
Application number: PCT/JP2000/007298
Authority: WO
Inventors: Hiroaki Ikeda; Masahisa Fujimoto; Shin Fujitani; Masaki Shima; Hiromasa Yagi; Hisaki Tarui; Hiroshi Kurokawa; Kenji Asaoka; Shigeki Matsuta; Yoichi Domoto; Ryuji Ohshita; Yoshio Kato; Hiroshi Nakajima; Yasuyuki Kusumoto; Toshikazu Yoshida
Original assignee: Sanyo Electric Co., Ltd.
Priority date: 1999-10-22
Filing date: 2000-10-20
Publication date: 2001-04-26
Also published as: AU7951200A; JP3733065B2

Abstract

An electrode for a lithium cell containing an active material absorbing/desorbing lithium, characterized in that the active material is noncrystalline silicon or microcrystalline silicon.

Description

Description Electrode for lithium battery and lithium secondary battery Technical field

The present invention relates to a novel electrode for a lithium battery, and a lithium battery and a lithium secondary battery using the same. Background art

In recent years, lithium secondary batteries, which are being actively researched and developed, greatly affect battery characteristics such as charge / discharge voltage, charge / discharge cycle life characteristics, and storage characteristics depending on the electrodes used. For this reason, the battery characteristics are being improved by improving the electrode active material.

When lithium metal is used as the negative electrode active material, a battery having a high energy density per weight and per volume can be formed.However, there is a problem that lithium is deposited in a dendrite shape during charging and causes an internal short circuit. Was o

On the other hand, lithium secondary batteries using aluminum, silicon, tin, etc., which electrochemically alloy with lithium during charging, have been reported (Sol id State Ionics, 113-115, p57 (1998)). Among these, silicon is particularly promising as a battery negative electrode having a large theoretical capacity and a high capacity, and various secondary batteries using this as a negative electrode have been proposed (Japanese Patent Application Laid-Open No. 10-25557). No. 68). However, this type of alloy negative electrode has not been able to provide a positive cycle characteristic because the alloy itself, which is the electrode active material, is pulverized by charging and discharging and the current collecting characteristics deteriorate. Disclosure of the invention

An object of the present invention is to provide a novel electrode for a lithium battery, and a lithium battery and a lithium secondary battery using the same.

A first aspect according to the present invention is an electrode for a lithium battery including an active material for inserting and extracting lithium, wherein the amorphous silicon is used as the active material.

In general, silicon is roughly classified into amorphous silicon, microcrystalline silicon, polycrystalline silicon, and single crystal silicon according to the difference in crystallinity. “Amorphous silicon” in the present invention means amorphous silicon and microcrystalline silicon, excluding polycrystalline silicon and single crystal silicon. Amorphous silicon is ^{one in which} a peak near 520 cm- ¹ corresponding to a crystalline region is not substantially detected in Raman spectroscopy described later. Microcrystalline silicon, in Raman spectroscopic analysis, qualitative and peak of 5 2 0 cm one near ¹ corresponding to the crystal region, both peaks 4 8 0 cm- ¹ near corresponding to the amorphous region real Is detected. Therefore, microcrystalline silicon is substantially composed of a crystalline region and an amorphous region. For polycrystalline silicon and single-crystal silicon, a peak near 480 cm- ¹ corresponding to an amorphous region is not substantially detected in Raman spectroscopy.

As described above, “amorphous silicon” in the present invention includes amorphous silicon and microcrystalline silicon. Therefore, in the first aspect according to the present invention, amorphous silicon or microcrystalline silicon is used as the active material.

Amorphous silicon or microcrystalline silicon may contain hydrogen. In this case, the hydrogen concentration in the amorphous silicon or microcrystalline silicon is, for example, 0.01 atomic% or more. Hydrogen concentration can be measured by secondary ion mass spectrometry (SIMS). The size of the crystal region in the microcrystalline silicon in the first aspect is, for example, 0.5 nm or more as a crystal grain size calculated from the X-ray diffraction spectrum and the Scherrer equation.

The method for calculating the crystal grain size from the X-ray diffraction spectrum and the Scherrer equation is described in the Thin Film Handbook (1st edition, edited by the Japan Society for the Promotion of Science, Thin Film Committee 131, published by Ohm Co., Ltd.). It is described on page 375.

The crystal grain size calculated from the above-mentioned X-ray diffraction spectrum and the formula of Scherr er does not always match the crystal grain size observed with, for example, a scanning electron microscope. Further, the crystal region may extend in a specific direction, for example, a thickness direction. In this case, for example, the length in the thickness direction may be about 10 / m.

In the first aspect, 4 8 0 cm- ¹ near the peak intensity ratio of (4 8 0 cm- ¹ near to the peak intensity of 5 2 0 c ^Tn-1 near that put in Raman spectroscopic analysis of microcrystalline silicon Z520cm- ¹ ) is, for example, not less than 0.05.

Incidentally, 4 8 0 cm- ¹ near the peak corresponding to the amorphous region is known to be shifted about 1 0 cm one ^1. It is also known that the peak near 520 cm- ¹ corresponding to the crystal region shifts by about 5 cm- ¹ . Incidentally, 4 8 0 cm- ¹ near the peak, a broad peak der Runode sometimes spread peak hem to 5 2 0 cm one near ^1. In this case, the peak intensity ratio is calculated without subtracting the spread portion of the peak and using the height of the peak near 520 cm- ¹ as the peak intensity. In the first aspect, the amorphous silicon and the microcrystalline silicon are preferably silicon thin films. In particular, a silicon thin film deposited on a substrate by supplying a silicon material from a gas phase is preferable. A silicon thin film formed by introducing hydrogen gas together with silicon material. You may.

As the silicon material, a raw material gas containing silicon atoms or a raw material powder containing silicon atoms can be used.

Examples of the method for forming the silicon thin film include a CVD method, a sputtering method, a thermal spraying method, and a vacuum evaporation method. In the first aspect, it is particularly preferable that a current collector is used as a substrate and a silicon thin film is formed on the current collector. When forming the silicon thin film on the current collector, an intermediate layer may be formed on the current collector, and the silicon thin film may be formed on the intermediate layer.

The current collector material includes at least one selected from copper, nickel, stainless steel, molybdenum, tungsten, and tantalum. The surface roughness Ra of the current collector is preferably at least 0.1 μm, more preferably 0.01 to 1 μπι, and still more preferably 0.05 to 0.5 μm. It is. The surface roughness Ra is specified in Japanese Industrial Standards (JIS B0601-19994), and can be measured by, for example, a surface roughness meter.

The surface roughness Ra of the current collector preferably has a relationship of Ra≤t with respect to the thickness t of the active material thin film. It is preferable that the surface roughness Ra of the current collector and the average distance S between the local peaks have a relationship of 100 Ra≥S. The average distance S between the local peaks is defined in the three industrial standards (JIS B 060 1-19-1994), and can be measured by, for example, a surface roughness meter. The shape of the projections of the irregularities on the current collector surface is not particularly limited, but is preferably, for example, a cone.

A second aspect according to the present invention is a lithium battery electrode in which a thin film made of an active material that stores and releases lithium is provided on a current collector, and the thin film is formed into a columnar shape by a cut formed in the thickness direction. Separated and the pillar It is characterized in that the bottom of the shape portion is in close contact with the current collector.

The silicon thin film in the first aspect is preferably a thin film according to the second aspect. That is, it is preferable that the silicon thin film is separated into columns by the cuts formed in the thickness direction, and that the bottom of the columnar portion is in close contact with the current collector.

The active material thin film in the second aspect is separated into columns by cuts formed in the thickness direction. For this reason, a gap is formed around the columnar portion, and the gap reduces the expansion and contraction of the thin film due to the charge / discharge cycle, and generates a stress that causes the active material thin film to separate from the current collector. Can be suppressed. Therefore, the state of close contact with the current collector at the bottom of the columnar portion can be favorably maintained.

In the second aspect, in the thickness direction of the thin film, it is preferable that at least a portion of 1 Z 2 or more of the thickness of the thin film is separated into a column by a cut.

Further, when the surface of the thin film has irregularities and a cut having the valley of the irregularity as an end is formed in the thin film, the columnar portion forms at least one convex portion on the surface of the thin film. A cut may be formed to include the cut. In this case, a cut may be formed so as to include a plurality of convex portions.

In the second aspect, the cut formed in the thin film may be formed by charge and discharge after the first time. In such a case, for example, irregularities are formed on the surface of the thin film before charging / discharging, and the first charging / discharging forms a cut having a concave / convex valley on the surface of the thin film as an end. May be separated into columns.

The unevenness on the surface of the thin film may be formed corresponding to the unevenness on the surface of the current collector as an underlayer. That is, by using a current collector having irregularities on the surface and forming a thin film thereon, irregularities can be imparted to the surface of the thin film. You.

The surface roughness Ra of the current collector is preferably at least 0.01 μm, more preferably 0.01 to l / xm, and still more preferably 0.05 to 0.5 μm. m. The surface roughness Ra is defined in Japanese Industrial Standards (JISB 0601-1994), and can be measured by, for example, a surface roughness meter.

The surface roughness Ra of the current collector preferably has a relationship of Ra≤t with respect to the thickness t of the active material thin film. Further, it is preferable that the surface roughness Ra of the current collector and the average interval S between the local peaks have a relationship of 100 Ra≥S. The average distance S between local peaks is specified in Japanese Industrial Standards (JIS B 0601-1994), and can be measured by, for example, a surface roughness meter. The shape of the projections of the irregularities on the current collector surface is not particularly limited, but is preferably, for example, a cone.

Further, the upper part of the columnar part is preferably rounded in order to avoid concentration of current in the charge / discharge reaction.

In the second aspect, the cut in the thickness direction formed in the thin film made of the active material may be formed by charge / discharge after the first time, or may be formed before charge / discharge. As a method of forming such a break in a thin film before charging / discharging, a method of absorbing lithium or the like into a thin film of an electrode and then releasing the thin film before assembling the battery, for example, after expanding the volume of the thin film. It can be formed by shrinking. Alternatively, a thin film separated into a pillar shape by a cut may be formed by forming a thin film in a pillar shape using a resist film or the like patterned by photolithography. The active material thin film in the second aspect can be formed, for example, from a material that forms a compound or a solid solution with lithium. Such materials include elements of the Periodic Table III, III, IVB and VB, At least one material selected from oxides and sulfides of transition metal elements having four, five, and six periods of the periodic table can be given.

In the second aspect, the elements of the Periodic Table I, II, IVB, and VB that form a compound or solid solution with lithium include carbon, aluminum, silicon, phosphorus, and zinc. , Gallium, germanium, arsenic, cadmium, indium, tin, antimony, mercury, thallium, lead, and bismuth. The transition metal elements of the Periodic Table at 4, 5, and 6 periods are, specifically, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, and zirconium. These include ruconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, lanthanide elements, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, and mercury.

Among the above elements, at least one element selected from carbon, silicon, germanium, tin, lead, aluminum, indium, zinc, cadmium, bismuth, and mercury is preferable, and silicon is more preferable. And germanium or germanium.

“Amorphous silicon” in the second aspect also means amorphous silicon and microcrystalline silicon, excluding polycrystalline silicon and single crystal silicon, as described above.

In the second aspect, the silicon thin film used as the active material thin film is preferably a microcrystalline silicon thin film or an amorphous silicon thin film.

In addition, as a preferable active material thin film used in the second aspect, a germanium thin film and a silicon germanium alloy thin film other than the above silicon thin film are exemplified. As the germanium thin film, a microcrystalline germanium thin film and an amorphous germanium thin film are preferably used. Silicon gel As the mannium alloy thin film, a microcrystalline silicon germanium alloy thin film and an amorphous silicon germanium thin film are preferably used. The microcrystal and amorphous of the germanium thin film and the silicon germanium alloy thin film can be determined in the same manner as the above-mentioned silicon thin film. Good results have been obtained for silicon and germanium, as described in the examples below. Since silicon and germanium are dissolved at an arbitrary ratio, a similar effect can be expected for a silicon germanium alloy.

In the second aspect, the method for forming the active material thin film on the current collector is not particularly limited, and examples thereof include a CVD method, a sputtering method, a vapor deposition method, a thermal spray method, and a plating method. No. Among these thin film forming methods, a CVD method, a sputtering method, and a vapor deposition method are particularly preferably used.

The current collector used in the second aspect is not particularly limited as long as the active material thin film can be formed thereon with good adhesion. Specific examples of the current collector include at least one selected from copper, nickel, stainless steel, molybdenum, tandatin, and tantalum.

The current collector is preferably a thin one, and is preferably a metal foil. The current collector is preferably formed of a material that does not alloy with lithium, and a particularly preferable material is copper. The current collector is preferably a copper foil, and is preferably a copper foil having a roughened surface. An example of such a copper foil is an electrolytic copper foil. For example, an electrolytic copper foil is made by immersing a metal drum in an electrolytic solution in which copper ions are dissolved, and rotating it to apply an electric current to deposit copper on the surface of the drum and peel it off. The resulting copper foil. One or both sides of the electrolytic copper foil may be subjected to a roughening treatment or a surface treatment.

In addition, copper is deposited on the surface of the rolled copper foil by electrolytic method to roughen the surface. Copper foil may be used.

Alternatively, an intermediate layer may be formed on the current collector, and an active material thin film may be formed on the intermediate layer. In this case, the intermediate layer preferably contains a component which is easily diffused into the active material thin film, and for example, a copper layer is preferable. For example, a current collector formed by forming a copper layer on a nickel foil having a roughened surface (such as an electrolytic nickel foil) may be used. Alternatively, a nickel foil may be used in which copper is deposited on the nickel foil by an electrolytic method, and the copper foil is roughened.

The cut formed in the active material thin film in the second aspect may be formed along a low-density region formed in the active material thin film in advance so as to extend in the thickness direction. Such a low-density region is formed, for example, so as to extend upward from a valley of unevenness on the surface of the current collector.

In the second aspect, it is preferable that the components of the current collector diffuse into the active material thin film. The diffusion of the current collector component into the thin film can enhance the adhesion between the current collector and the active material thin film. In addition, when an element such as copper that does not alloy with lithium is diffused as a current collector component, alloying with lithium is suppressed in the diffusion region, so that the thin film expands and contracts due to the charge / discharge reaction. Therefore, it is possible to suppress the occurrence of stress that may cause the active material thin film to separate from the current collector.

Further, it is preferable that the concentration of the current collector component diffused into the thin film is high in the vicinity of the current collector, and gradually decreases as approaching the thin film surface. By having such a concentration gradient of the current collector component, the expansion and contraction of the thin film due to the charge / discharge reaction is suppressed more strongly in the vicinity of the current collector, so that the stress causing the separation of the active material thin film is reduced. It is easy to suppress generation near the current collector. In addition, since the concentration of the current collector component decreases as approaching the thin film surface, a high charge / discharge capacity can be maintained.

In addition, the diffused current collector component becomes intermetallic with the thin film component in the thin film. It is preferable to form a solid solution without forming a compound. Here, the intermetallic compound refers to a compound having a specific crystal structure in which metals are combined at a specific ratio. By forming a solid solution instead of an intermetallic compound in the thin film, the thin film component and the current collector component improve the adhesion between the thin film and the current collector, and obtain a higher charge / discharge capacity. Can be.

The active material thin film in the second aspect may be doped with impurities. Examples of such impurities include phosphorus, aluminum, arsenic, antimony, boron, gallium, indium, oxygen, nitrogen, and other elements of the Periodic Table Group IV, IVB, VB, and VIB. be able to.

Further, the active material thin film in the second aspect may be formed by laminating a plurality of layers. Each of the stacked layers may have a different composition, crystallinity, impurity concentration, and the like. Further, the thin film may have a tilted structure in the thickness direction. For example, an inclined structure in which thickness, crystallinity, impurity concentration, and the like are changed in the thickness direction can be used.

The thickness of the active material thin film of the second aspect is not particularly limited, but may be, for example, 20 μm or less. In order to obtain a high charge / discharge capacity, the thickness is preferably 1 μm or more.

In the second aspect, an intermediate layer may be provided between the current collector and the thin film in order to improve the adhesion between the current collector and the thin film. As such a material for the intermediate layer, a material that forms an alloy with the current collector material and the active material is preferably used.

The active material thin film in the second aspect is preferably an active material thin film that absorbs lithium by forming an alloy with lithium.

Further, the active material thin film in the second aspect may have lithium stored or added in advance. Lithium may be added when forming the active material thin film. That is, forming an active material thin film containing lithium

0 Accordingly, lithium may be added to the active material thin film. Further, after the active material thin film is formed, lithium may be inserted or added to the active material thin film. As a method of inserting or absorbing lithium into the active material thin film, a method of electrochemically inserting or extracting lithium is used.

According to an embodiment of the third aspect of the present invention, there is provided an electrode for a lithium secondary battery in which an active material thin film that expands and contracts due to insertion and extraction of lithium is formed on a current collector, and is defined by the following equation. The current collector has a tensile strength of 3.82 N / mm or more.

Tensile strength of current collector (NZmm) = Tensile strength per cross-sectional area of current collector material (N / mm ² ) X Thickness of current collector (mm)

Here, the tensile strength per cross-sectional area of the current collector material can be measured, for example, by a method specified by Japanese Industrial Standards (JIS).

In the above embodiment, the current collector preferably has a tensile strength of 7.44 N / mm or more.

According to another embodiment of the third aspect of the present invention, there is provided an electrode for a lithium secondary battery in which an active material thin film that expands and contracts due to insertion and extraction of lithium is formed on a current collector. The current collector has a tensile strength of 1.12 N / mm or more per 1 μπι in thickness.

The tensile strength of the current collector per 1 // m of the thickness of the active material thin film can be obtained by the following equation.

(Tensile strength of current collector per 1 μm thickness of active material thin film) = (Tensile strength of current collector) ÷ (Thickness of active material thin film: μ τη)

Note that the tensile strength of the current collector is a value defined in the first aspect described above. In the above embodiment, the tensile strength of the current collector per 1 // m of the thickness of the active material thin film is preferably 2.18 NZmm or more, and more preferably, 4.25 N / mm That is all. According to still another embodiment of the third aspect of the present invention, there is provided a lithium secondary electrode in which an active material thin film that expands and contracts due to insertion and extraction of lithium is formed on a current collector, and the thickness of the current collector varies with respect to the thickness of the current collector. It is characterized in that the ratio of the thickness of the active material thin film (thickness of the active material thin film / "thickness of the current collector") is 0.19 or less. The thickness ratio is preferably 0.098 or less, more preferably 0.05 or less.

According to the third aspect of the present invention, it is possible to suppress generation of wrinkles in the electrode due to charging and discharging.

In the third aspect, the surface roughness Ra of the current collector is preferably at least 0.1 μμηι, more preferably 0.01 to 1 μm, and still more preferably 0.1 μm. It is 0.5 to 0.5 μm. The surface roughness Ra of the current collector is preferably about the same as the surface roughness Ra of the electrolytic copper foil described later. Therefore, the surface roughness Ra of the current collector is preferably at least 0.1 m, more preferably 0.1 to 1 m. The surface roughness Ra is specified in Japanese Industrial Standards (JISB 0601-1994) and can be measured, for example, by a surface roughness meter.

In the third aspect, the surface roughness Ra of the current collector preferably has a relationship of Ra ≦ t with respect to the thickness t of the active material. Further, it is preferable that the average surface roughness Ra of the current collector and the average interval S between the local peaks have a relationship of 100 RaS. The average distance S between the local peaks is specified in Japanese Industrial Standards (JIS B 0601-1994) and can be measured, for example, with a surface roughness meter.

The shape of the projections of the irregularities on the current collector surface is not particularly limited, but is preferably, for example, a cone.

In the third aspect, the current collector component is diffused in the active material thin film.

Two Is preferred. By diffusing the current collector component into the active material thin film, the adhesion between the active material thin film and the current collector is further increased, and peeling of the active material thin film from the current collector can be more effectively prevented. Therefore, the charge / discharge cycle characteristics can be further improved.

When a thin film made of an active material that alloys with lithium is used as the active material thin film, and a current collector made of a material that does not alloy with lithium is used as the current collector, the diffusion of the current collector component causes absorption and release of lithium. The accompanying expansion and contraction of the thin film portion near the current collector can be relatively reduced. Therefore, the state of adhesion between the thin film and the current collector can be more favorably maintained.

Preferably, the concentration of the current collector component in the thin film is high near the current collector and decreases as approaching the surface of the thin film. By having such a concentration gradient, the expansion and contraction of the thin film is suppressed near the current collector, the close contact between the thin film and the current collector is maintained, and the amount of the active material is relatively reduced near the surface of the thin film. Therefore, a high charge / discharge capacity can be maintained.

The diffused current collector component preferably forms a solid solution in the thin film without forming an intermetallic compound with the thin film component. Here, the intermetallic compound refers to a compound having a specific crystal structure in which metals are combined at a specific ratio. When the thin film component and the current collector component form a solid solution instead of an intermetallic compound in the thin film, the adhesion between the thin film and the current collector becomes better, and a higher charge / discharge capacity can be obtained. it can.

In the third aspect, the thickness of the region where the current collector component is diffused is not particularly limited, but is preferably 1 μm or more.

The current collector used in the third aspect is not particularly limited as long as the current collector satisfies the conditions of the third aspect. Specific examples of the current collector include at least one selected from copper, nickel, stainless steel, molybdenum, tungsten, and tantalum.

Three The current collector is preferably a thin one, and is preferably a metal foil. The current collector is preferably formed of a material that does not alloy with lithium, and a particularly preferable material is copper. The current collector is preferably a copper foil, and is preferably a copper foil having a roughened surface. An example of such a copper foil is an electrolytic copper foil. For example, an electrolytic copper foil is made by immersing a metal drum in an electrolytic solution in which copper ions are dissolved, and rotating it to apply an electric current to deposit copper on the surface of the drum and peel it off. The resulting copper foil. One or both sides of the electrolytic copper foil may be subjected to a roughening treatment or a surface treatment.

Further, the copper foil may be a copper foil whose surface is roughened by depositing copper on the surface of a rolled copper foil by an electrolytic method.

The active material thin film in the third aspect can be formed, for example, from a material that forms a compound or a solid solution with lithium. Examples of such materials include Group Β, Π Ι, Group IVB, and Group VB elements of the periodic table, and oxides and transition metal elements of the periodic table having four, five, and six periods. At least one material selected from sulfides can be mentioned.

In the third aspect, the elements of Group IIB, Group III, Group IVB and Group VB which form a compound or solid solution with lithium include carbon, aluminum, silicon, phosphorus, sublimation, gallium, Germanium, arsenic, cadmium, indium, tin, antimony, mercury, thallium, lead, and

Four Bismuth. The transition metal elements of the Periodic Table at 4, 5, and 6 periods are, specifically, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, and zirconium. These include ruconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, lanthanide elements, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, and mercury.

Among the above elements, at least one selected from the group consisting of carbon, silicon, germanium, tin, lead, aluminum, indium, zinc, cadmium, bismuth, and mercury is preferable, and silicon and / or silicon is more preferable. Germanium.

“Amorphous silicon” in the third aspect also means amorphous silicon and microcrystalline silicon, excluding polycrystalline silicon and single crystal silicon, as described above. ·

In the third aspect, the silicon thin film used as the active material thin film is preferably a microcrystalline silicon thin film or an amorphous silicon thin film.

In addition, as a preferable active material thin film used in the third aspect, a germanium thin film and a silicon germanium alloy thin film other than the above silicon thin film are exemplified. As the germanium thin film, a microcrystalline germanium thin film and an amorphous germanium thin film are preferably used. As the silicon germanium alloy thin film, a microcrystalline silicon germanium alloy thin film and an amorphous silicon germanium thin film are preferably used. The microcrystal and amorphous of the germanium thin film and the silicon germanium alloy thin film can be determined in the same manner as the above silicon thin film. Silicon and germanium provide good results, as described in the examples below.Since silicon and germanium dissolve at an arbitrary ratio, silicon germanium

Five Similar effects can be expected for a nickel alloy.

In the third aspect, the thin film is preferably separated into columns by cuts formed in the thickness direction, and the bottom of the columnar portion is preferably in close contact with the current collector. In addition, it is preferable that at least a portion having a thickness of 1 Z 2 or more in the thickness direction of the thin film is separated into a column by a cut.

The cut is preferably formed by expansion and contraction of the thin film. Such expansion and contraction of the thin film is given by, for example, a charge and discharge reaction of the thin film. Therefore, the cut may be formed by a charge / discharge reaction after assembling the battery, or may be formed by a charge / discharge reaction before assembling the battery. As a method of forming such a break in the thin film before charging / discharging, the volume of the thin film is expanded before the battery is assembled by, for example, absorbing and releasing lithium or the like in the thin film of the electrode. It can be formed by shrinking. Alternatively, a thin film formed into a column shape using a resist film or the like patterned by a photolithography method may be used as a thin film separated into a column shape by a cut.

When the unevenness is formed on the surface of the thin film, the cut may be formed in the thickness direction from the valley of the unevenness on the surface of the thin film toward the current collector. Further, the irregularities on the surface of the thin film may be formed corresponding to the irregularities on the surface of the current collector. That is, by using a current collector having irregularities on the surface and forming a thin film thereon, irregularities can be imparted to the surface of the thin film.

The shape of the thin film above the columnar portion is not particularly limited, but is preferably a rounded shape.

Further, the cut may be formed in the thickness direction along a low-density region previously formed in the thin film. Such a low-density region extends, for example, in a mesh pattern in the plane direction and extends in the thickness direction toward the current collector.

6 You.

In the third aspect, the method for forming the active material thin film on the current collector is not particularly limited, and examples thereof include a CVD method, a sputtering method, a vapor deposition method, a thermal spray method, and a plating method. No. Among these thin film forming methods, the CVD method, the sputtering method, and the vapor deposition method are particularly preferably used.

The active material thin film in the third aspect may be doped with impurities. Examples of such impurities include phosphorus, aluminum, arsenic, antimony, boron, gallium, indium, oxygen, nitrogen, and other elements of the Periodic Table Group IV, IVB, VB, and VIB. be able to.

Further, the active material thin film in the third aspect may be formed by laminating a plurality of layers. Each of the stacked layers may have a different composition, crystallinity, impurity concentration, and the like. Further, the thin film may have a tilted structure in the thickness direction. For example, an inclined structure in which the composition, crystallinity, impurity concentration, and the like are changed in the thickness direction can be used.

The active material thin film in the third aspect is preferably an active material thin film that absorbs lithium by forming an alloy with lithium.

Further, the active material thin film in the third aspect may contain or add lithium in advance. Lithium may be added when forming the active material thin film. That is, lithium may be added to the active material thin film by forming an active material thin film containing lithium. Further, after the active material thin film is formed, lithium may be inserted or added to the active material thin film. As a method of inserting or absorbing lithium into the active material thin film, a method of electrochemically inserting or extracting lithium is used.

Further, the thickness of the active material thin film of the third aspect is preferably 1 μm or more in order to obtain a high charge / discharge capacity.

7 In the third aspect, as described above, an intermediate layer may be provided between the current collector and the thin film in order to improve the adhesion between the current collector and the thin film. As a material for such an intermediate layer, a substance that forms an alloy with the current collector material and the active material is preferably used.

A fourth aspect of the present invention is an electrode for a lithium battery in which an active material thin film made of an active material that absorbs and releases lithium is provided on a current collector through an intermediate layer, and the intermediate layer is formed of an active material thin film. It is characterized by being formed from a material to be alloyed.

By using an intermediate layer formed of a material alloying with the active material thin film as the intermediate layer, the adhesion of the active material thin film to the current collector can be improved. Therefore, detachment of the thin film from the current collector when the thin film expands and contracts due to the charge / discharge reaction can be prevented, and good charge / discharge cycle characteristics can be obtained.

In one of the preferred embodiments according to the fourth aspect, a foil made of a metal or alloy having higher mechanical strength than the material of the intermediate layer is used as the current collector.

In the fourth aspect, since the active material thin film expands and contracts due to insertion and extraction of lithium, stress is generated in the current collector due to the charge / discharge reaction. Such stress causes irreversible, that is, wrinkles due to plastic deformation in the current collector. The formation of wrinkles results in an increase in the volume of the battery and an uneven reaction at the electrodes, resulting in a decrease in energy density. In order to suppress the occurrence of such wrinkles, it is preferable to use a material having high mechanical strength, that is, a material having high tensile strength and tensile elastic modulus as the current collector. However, when such a material is used as a current collector and an active material thin film is formed directly on the current collector, the adhesion between the active material thin film and the current collector becomes insufficient, and a good charge / discharge cycle cannot be obtained. There are cases. In such a case, as above

8 By providing an intermediate layer made of a material that alloys with the active material thin film between the current collector and the thin film, it is possible to prevent the thin film from being detached during the charge / discharge reaction, It is possible to suppress the occurrence of wrinkles. Therefore, by using a foil made of a metal or alloy having higher mechanical strength than the material of the intermediate layer as a current collector, it is possible to reduce wrinkles in the current collector while maintaining good charge / discharge cycle characteristics. Can be suppressed. Further, in the fourth aspect, it is preferable that irregularities are formed on the surface of the intermediate layer. Due to the formation of irregularities on the surface of the intermediate layer, the contact area at the interface between the intermediate layer and the active material thin film increases, and the adhesion between the active material thin film and the intermediate layer, that is, the active material thin film and the current collector Can improve the adhesiveness of the fabric.

The irregularities on the surface of the intermediate layer can be formed, for example, by using a current collector having irregularities on the surface. In this case, irregularities corresponding to the irregularities on the surface of the current collector are formed on the surface of the intermediate layer.

In the above case, the surface roughness Ra of the current collector is preferably from 0.001 to 1 μηι, and more preferably from 0.01 to 1 μm. The surface roughness Ra is defined in Japanese Industrial Standards (JIS B0601-11994), and can be measured by, for example, a surface roughness meter.

In the fourth aspect, the surface roughness Ra of the current collector preferably has a relationship of Ra ≦ t with respect to the thickness t of the active material. Further, it is preferable that the surface roughness Ra of the current collector and the average distance S between the local peaks have a relationship of 100 Ra≥S. The average distance S between the local peaks is specified in Japanese Industrial Standards (JISB 0601-1994), and can be measured by, for example, a surface roughness meter.

9 The active material thin film in the fourth aspect can be formed, for example, from a material that forms a compound or a solid solution with lithium. Examples of such materials include Group Β, Ι Π, Group IVB, and Group VB elements of the periodic table, and oxides and transition metal elements of the periodic table having four, five, and six periods. At least one material selected from sulfides can be mentioned.

In the fourth aspect, the elements of the Periodic Table I, II, IVB, and VB that form a compound or solid solution with lithium include carbon, aluminum, silicon, phosphorus, Examples include zinc, gallium, germanium, arsenic, cadmium, zinc, tin, antimony, mercury, thallium, lead, and bismuth. The transition metal elements of the Periodic Table at 4, 5, and 6 periods are specifically scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, and zirconium. , Niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, lanthanide elements, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, and mercury.

Among the above elements, at least one selected from carbon, silicon, germanium, tin, lead, aluminum, indium, zinc, cadmium, bismuth, and mercury is preferable, and silicon and Z are more preferable. Or it is germanium.

“Amorphous silicon” in the fourth aspect also refers to amorphous silicon and microcrystalline silicon, excluding polycrystalline silicon and single crystal silicon, as described above.

In the fourth aspect, the silicon thin film used as the active material thin film is preferably a microcrystalline silicon thin film or an amorphous silicon thin film.

Further, preferred active material thin films used in the fourth aspect include the above-mentioned active material thin films. In addition to the silicon thin film described above, a germanium thin film and a silicon germanium alloy thin film may be used. As the germanium thin film, a microcrystalline germanium thin film and an amorphous germanium thin film are preferably used. As the silicon germanium alloy thin film, a microcrystalline silicon germanium alloy thin film and an amorphous silicon germanium thin film are preferably used. The microcrystal and amorphous of the germanium thin film and the silicon germanium alloy thin film can be determined in the same manner as the above-mentioned silicon thin film. Good results have been obtained for silicon and germanium, as described in the examples below. Silicon and germanium dissolve at an arbitrary ratio, so the same effect can be expected for silicon germanium alloy.

When a silicon thin film, a germanium thin film, or a silicon germanium alloy thin film is used as the active material thin film, copper is an example of a material alloyed with these. Therefore, when using these thin films, it is preferable to use a copper layer as the intermediate layer. The tensile strength of copper is 22.7 N / mm ² (21.7 kgf / mm ² , “Revision 2 Metal Data Book” published by Maruzen Co., Ltd.). As the metal or alloy having high tensile strength than such tensile strength of copper, nickel (tensile strength = 3 1 5. 6 N / mm 2 = 3 2. 2 kgf / mm 2, "second revised edition Metal Data Book ”published by Maruzen Co., Ltd.). Therefore, when a copper layer is formed as the intermediate layer, it is preferable to use a nickel foil as the current collector. Examples of other current collector materials include various copper alloys such as tin bronze (phosphor bronze), silicon bronze, and aluminum bronze, nickel alloys, iron and iron alloys, and stainless steel. Further, other current collector materials include molybdenum, tungsten, and tantalum.

In the fourth aspect, the material of the intermediate layer is a material that alloys with the active material thin film, but the components of the intermediate layer are preferably diffused into the active material thin film.

Two Les ,. The diffusion of the component of the intermediate layer into the active material thin film further enhances the adhesion between the active material thin film and the intermediate layer, and effectively prevents the active material thin film from peeling from the current collector. Therefore, the charge / discharge cycle characteristics can be further improved.

When a thin film made of an active material that alloys with lithium is used as the active material thin film, and an intermediate layer made of a material that does not alloy with lithium is formed on the current collector as the intermediate layer, the diffusion of the components of the intermediate layer causes diffusion of lithium. The expansion and contraction of the thin film near the intermediate layer due to occlusion and release can be relatively reduced. Therefore, the state of adhesion between the thin film and the intermediate layer can be kept even better.

It is preferable that the concentration of the component of the intermediate layer in the active material thin film is high near the intermediate layer and decreases as approaching the active material thin film surface. By having such a concentration gradient, the expansion and contraction of the thin film is suppressed near the intermediate layer, the state of adhesion between the thin film and the intermediate layer is maintained, and the amount of the active material is relatively large near the surface of the thin film. Therefore, a high charge / discharge capacity can be maintained.

The diffused component of the intermediate layer preferably forms a solid solution in the thin film without forming an intermetallic compound with the thin film component. Here, the intermetallic compound refers to a compound having a specific crystal structure in which metals are combined at a specific ratio. When the thin film component and the intermediate layer component form a solid solution instead of an intermetallic compound in the thin film, the state of adhesion between the thin film and the intermediate layer becomes better, and a higher charge / discharge capacity can be obtained.

The current collector is preferably a thin one, and is preferably a metal foil. The current collector is preferably formed of a material that does not alloy with lithium. As described above, when a copper layer is formed as the intermediate layer, it is preferable to use a nickel foil as the current collector. When a nickel foil is used as the current collector, an electrolytic nickel foil can be used as the nickel foil having the irregularities formed on its surface.

For example, an electrolytic nickel foil is prepared by immersing a metal drum in an electrolytic solution in which nickel ions have been dissolved, and applying an electric current while rotating the metal to deposit nickel on the surface of the drum. It is a nickel foil obtained by One or both surfaces of the electrolytic nickel foil may be subjected to a roughening treatment or a surface treatment.

Alternatively, a nickel foil may be used in which copper is deposited on the surface of a rolled Eckel foil by an electrolytic method and the surface is covered with a copper layer having a roughened surface.

In the fourth aspect, it is preferable that the active material thin film is separated into a column by a cut formed in the thickness direction, and that the bottom of the columnar portion is tightly adhered to the current collector. In addition, it is preferable that at least a half or more of the thickness in the thickness direction of the active material thin film is separated into columns by cuts.

The cut is preferably formed by expansion and contraction of the active material thin film. Such expansion and contraction of the active material thin film is given by, for example, a charge / discharge reaction of the active material thin film. Therefore, the cut may be formed by a charge / discharge reaction after assembling the battery, or may be formed by a charge / discharge reaction before assembling the battery. As a method of forming such cuts in the active material thin film before charging / discharging, for example, before assembling the battery, the active material thin film of the electrode is made to absorb lithium or the like and then released, and the like. It can be formed by expanding and contracting the volume. Alternatively, the active material thin film may be formed into a pillar shape by using a resist film or the like patterned by a photolithography method, so that the active material thin film is separated into a pillar shape by a cut.

If irregularities are formed on the surface of the active material thin film, It may be formed in the thickness direction from the valleys of the surface irregularities toward the current collector. The irregularities on the surface of the active material thin film may be formed corresponding to the irregularities on the surface of the intermediate layer. That is, by forming an intermediate layer having irregularities on the surface and forming an active material thin film thereon, irregularities can be imparted to the surface of the active material thin film.

The shape above the columnar portion of the active material thin film is not particularly limited, but is preferably a rounded shape. .

Further, the cut may be formed in a thickness direction along a low-density region previously formed in the active material thin film. Such a low-density region is, for example, continuous in a mesh direction in the plane direction and extends in the thickness direction toward the current collector.

In the fourth aspect, the method for forming the active material thin film on the intermediate layer is not particularly limited, and examples thereof include a CVD method, a sputtering method, a vapor deposition method, a thermal spray method, and a plating method. No. Among these thin film forming methods, the CVD method, the sputtering method, and the vapor deposition method are particularly preferably used.

The active material thin film in the fourth aspect may be doped with impurities. Examples of such impurities include phosphorus, aluminum, arsenic, antimony, boron, gallium, indium, oxygen, nitrogen, and other elements of the Periodic Table Group IV, IVB, VB, and VIB. be able to.

Further, the active material thin film in the fourth aspect may be formed by laminating a plurality of layers. Each of the stacked layers may have a different composition, crystallinity, impurity concentration, and the like. Further, the thin film may have a tilted structure in the thickness direction. For example, a gradient structure in which the composition, crystallinity, impurity concentration, and the like are changed in the thickness direction can be used.

In the fourth aspect, the active material thin film forms an alloy with lithium. It is preferable that the active material thin film absorbs lithium more.

Further, the active material thin film in the fourth aspect may have lithium stored or added in advance. Lithium may be added when forming the active material thin film. That is, lithium may be added to the active material thin film by forming an active material thin film containing lithium. Further, after the active material thin film is formed, lithium may be inserted or added to the active material thin film. As a method of inserting or absorbing lithium into the active material thin film, a method of electrochemically inserting or extracting lithium is used.

Further, the thickness of the active material thin film of the fourth aspect is preferably 1 / X m or more in order to obtain a high charge / discharge capacity.

In the fourth aspect, the method for forming the intermediate layer on the current collector is not particularly limited, and examples thereof include a CVD method, a sputtering method, a vapor deposition method, a thermal spray method, and an electrolytic method (plating method). Is mentioned.

In the fourth aspect, the thickness of the intermediate layer is not particularly limited as long as it can improve the adhesion to the active material thin film, but is generally in the range of 0.01 to 10 / Xm. A thickness of the order is preferred.

The material of the intermediate layer is preferably a material that is familiar to the material of the current collector, and is preferably a material that forms an alloy with the current collector material. According to a fifth aspect of the present invention, there is provided a lithium secondary battery electrode comprising: a plate-shaped current collector; and an active material thin film that absorbs and desorbs lithium formed on both surfaces of the current collector. It is characterized by having.

In the fifth aspect, the active material thin film that stores and releases lithium is not particularly limited as long as it is a thin film that can be formed by being deposited on a current collector and that can store and release lithium. , But not limited to, elements of the Periodic Table II, III, IVB and VB, and Periodic Table 4, Period 5, and Period 6 that form compounds or solid solutions with lithium. Periodic At least one material selected from oxides and sulfides of transition metal elements is included. Among these, at least one selected from carbon, silicon, germanium, tin, lead, aluminum, indium, zinc, cadmium, bismuth, and mercury is preferable. From the viewpoint of obtaining a high electrode capacity, a silicon thin film, a germanium thin film, and a silicon germanium alloy thin film are particularly preferable.

Among the silicon thin films, a microcrystalline silicon thin film or an amorphous silicon thin film is particularly preferable. In a microcrystalline silicon thin film, in Raman spectroscopy, both the peak near 520 cm- ¹ corresponding to the crystalline region and the peak near 480 cm- ¹ corresponding to the amorphous region were substantially observed. It is a silicon thin film to be detected. Amorphous silicon thin film, a peak of 5 2 0 cm one near ¹ corresponding to the crystal region is not substantially detected, the peak of 4 8 0 cm- ¹ near corresponding to the amorphous region are substantially This is a silicon thin film to be detected. .

As the germanium thin film, an amorphous germanium thin film or a microcrystalline germanium thin film is preferable. As the silicon germanium alloy thin film, an amorphous silicon germanium alloy thin film or a microcrystalline silicon germanium alloy thin film is preferable.

In the fifth aspect, examples of a method of forming an active material thin film include a method of agglomerating and depositing a thin film from a gas phase, such as a CVD method, a sputtering method, an evaporation method, and a thermal spraying method, and a plating method.

The active material thin film is preferably formed on both surfaces of the current collector so that the amount of discharge / charge / discharge reaction with the lithium of each active material thin film is substantially the same per unit area. Therefore, it is preferable that each active material thin film is formed so that the thickness of each active material thin film is substantially the same on both surfaces of the current collector.

As the current collector in the fifth aspect, for example, a metal foil can be used. Wear. The metal foil is preferably a metal foil made of a metal that can be alloyed with the active material thin film from the viewpoint of enhancing the adhesion to the active material thin film. When a silicon thin film and a germanium thin film are formed as an active material thin film, the current collector is particularly preferably a copper foil. Further, as the copper foil, an electrolytic copper foil which is a copper foil having a large surface roughness Ra is preferable. Examples of such an electrolytic copper foil include an electrolytic copper foil in which a copper foil such as a rolled copper foil is immersed in an electrolytic solution, and copper is deposited on both surfaces of the copper foil by an electrolytic method to roughen both surfaces. .

Alternatively, an intermediate layer may be formed on both surfaces of the current collector, and an active material thin film may be formed on the intermediate layer. In this case, the intermediate layer is preferably formed from a material that alloys with the active material thin film. By forming such an intermediate layer, the components of the intermediate layer can be diffused into the active material thin film.

Further, the current collector for forming the intermediate layer is preferably a foil made of a metal or an alloy having higher mechanical strength than the material of the intermediate layer. For example, when a copper layer is formed as an intermediate layer, it is preferable to use a nickel foil as a current collector. For example, a copper layer may be formed on a nickel foil having a roughened surface (such as an electrolytic nickel foil). Alternatively, copper may be deposited on the nickel foil by an electrolytic method, and the nickel foil roughened by this may be used.

In the fifth aspect, it is preferable that both surfaces of the current collector on which the active material thin film is formed have substantially the same surface roughness Ra as each other.

In the fifth aspect, the surface roughness Ra of both surfaces of the current collector is preferably at least 0.01 μm, and more preferably 0.01 to l / m. preferable. Further, the surface roughness Ra of the current collector is preferably about the same as the surface roughness Ra of the electrolytic copper foil described later. Therefore, the surface roughness Ra of the current collector is preferably 0.1 μm or more, more preferably 0.1 μm. 1 to 1 μηι. Further, it is preferable that the average roughness S between the surface roughness Ra and the local peak has a relationship of 100 Ra≥S.

The surface roughness Ra and the average distance S between local peaks are specified in Japanese Industrial Standards (JIS B0601-1994), and can be measured by, for example, a surface roughness meter.

In a lithium secondary battery electrode according to a preferred embodiment according to the fifth aspect, the active material thin film is separated into columns by cuts formed in the thickness direction thereof, and the bottom of the columnar portion has a current collector. It is characterized by close contact.

Since a gap is formed around the columnar part, even if the active material expands and contracts repeatedly due to charge and discharge reactions, such expansion and contraction can be absorbed by the gap formed around the columnar part. Can be. Therefore, the charge / discharge reaction can be repeated without the active material thin film being detached and separated from the current collector.

In the thickness direction of the active material thin film, it is preferable that at least a partial force of 1Z2 or more in thickness is separated into a column by the cut.

Further, the cut is preferably formed by expansion and contraction of the active material thin film.

Further, the cut may be formed by a charge / discharge reaction after assembling the battery, or may be formed by a charge / discharge reaction before assembling the battery. In the fifth aspect, it is preferable that irregularities are formed on the surface of the active material thin film. In addition, it is preferable that the cut is formed in the thickness direction from the valley of the unevenness on the surface of the thin film toward the current collector.

The irregularities on the thin film surface are preferably formed corresponding to the irregularities on the current collector surface. In addition, it is preferable that the projections of the unevenness on the current collector surface have a cone shape. Further, it is preferable that the upper part of the columnar portion of the active material thin film has a rounded shape.

In another preferred embodiment according to the fifth aspect, in the active material thin film before the cut is formed, a low-density region which extends in a mesh direction in the plane direction and extends in the thickness direction toward the current collector is provided in the active material thin film. Are formed, and the cuts are formed in the thickness direction along the low density region. In the fifth aspect, it is preferable that the current collector component is diffused in the active material thin film. By diffusing the current collector component into the active material thin film, the adhesion between the active material thin film and the current collector is further increased, and peeling of the active material thin film from the current collector can be more effectively prevented. Therefore, the charge / discharge cycle characteristics can be further improved.

The diffused current collector component preferably forms a solid solution in the thin film without forming an intermetallic compound with the thin film component. Here, the intermetallic compound refers to a compound having a specific crystal structure in which metals are combined at a specific ratio. By forming a solid solution instead of an intermetallic compound in the thin film, the thin film component and the current collector component improve the adhesion between the thin film and the current collector. And a higher charge / discharge capacity can be obtained.

In the fifth aspect, the thickness of the region where the current collector component is diffused is not particularly limited, but is preferably 1 μm or more.

Further, as described above, when the intermediate layer is formed on the current collector and the active material thin film is formed on the intermediate layer, it is preferable that the components of the intermediate layer are diffused in the active material thin film. . It is preferable that the concentration of such an intermediate layer component is high in the vicinity of the intermediate layer in the active material thin film and decreases as approaching the active material thin film surface. Further, it is preferable that the diffused intermediate layer component forms a solid solution in the thin film without forming an intermetallic compound with the thin film component. By forming a solid solution instead of an intermetallic compound, the state of adhesion between the thin film and the intermediate layer becomes better, and a higher charge / discharge capacity can be obtained.

The current collector used in the fifth aspect is not particularly limited as long as the current collector satisfies the conditions of the fifth aspect. Specific examples of the current collector include at least one selected from copper, nickel, stainless steel, molybdenum, tungsten, and tantalum.

The active material thin film in the fifth aspect may be doped with impurities. Examples of such impurities include phosphorus, aluminum, arsenic, antimony, boron, gallium, indium, oxygen, nitrogen, and other elements of the Periodic Table Group IV, IVB, VB, and VIB. be able to.

Further, the active material thin film in the fifth aspect may be formed by stacking a plurality of layers. Each of the stacked layers may have a different composition, crystallinity, impurity concentration, and the like. Further, the thin film may have a tilted structure in the thickness direction. For example, a gradient structure in which the composition, crystallinity, impurity concentration, and the like are changed in the thickness direction can be used.

The active material thin film in the fifth aspect forms an alloy with lithium. It is more preferable that the active material thin film absorbs lithium.

Further, the active material thin film in the fifth aspect may have lithium inserted or stored in advance. Lithium may be added when forming the active material thin film. That is, lithium may be added to the active material thin film by forming an active material thin film containing lithium. Further, after the active material thin film is formed, lithium may be inserted or added to the active material thin film. Examples of a method of inserting or absorbing lithium into the active material thin film include a method of electrochemically inserting or extracting lithium.

Further, the thickness of the active material thin film of the fifth aspect is preferably at least 1 μm in order to obtain a high charge / discharge capacity.

A lithium secondary battery according to a fifth aspect is characterized by using the electrode for a lithium secondary battery according to the fifth aspect.

The electrode for a lithium secondary battery according to the fifth aspect described above may be used as a negative electrode or a positive electrode in the lithium secondary battery according to the fifth aspect. Since the standard potential for is low, it is preferable to use it as a negative electrode.

In the lithium secondary battery of the fifth aspect, the electrode structure based on the combination of the positive electrode and the negative electrode is not particularly limited, and various electrode structures can be adopted.

For example, a stack-type electrode structure in which a negative electrode composed of a lithium secondary battery electrode according to the fifth aspect and a positive electrode having a positive electrode active material layer provided on both sides of a current collector are alternately stacked via a separator is described. You may have.

Further, a separator is interposed between the negative electrode comprising the electrode for a lithium secondary battery according to the fifth aspect and a positive electrode having a positive electrode active material layer provided on both sides of a current collector, and an electrode obtained by spirally winding these. It may have a structure. As a lithium secondary battery having such an electrode structure, a cylindrical lithium secondary battery is used.

Three Batteries and prismatic lithium secondary batteries are known.

Further, a sandwiched electrode structure in which the other electrode is inserted into one electrode bent in a U-shape may be used.

As one of the lithium secondary batteries having the sandwiched electrode structure, a positive electrode in which a pair of positive electrode active material layers are provided inside a current collector bent into a U-shape so as to face each other; A negative electrode active material layer is provided on both surfaces, a negative electrode inserted inside the u-shaped positive electrode, and a separator disposed between the positive electrode active material layer of the positive electrode and the negative electrode active material layer of the negative electrode And wherein the negative electrode is the electrode for a lithium secondary battery according to the fifth aspect.

In addition, as another lithium secondary battery having the sandwiched electrode structure, a negative electrode in which a pair of negative electrode active material layers are provided inside a negative electrode bent in a u-shape, A positive electrode active material layer provided thereon, a positive electrode inserted inside the u-shaped negative electrode, and a separator disposed between the positive electrode active material layer of the positive electrode and the negative electrode active material layer of the negative electrode A lithium secondary battery is characterized in that the negative electrode active material layer of the negative electrode is an active material thin film such as a silicon thin film or a germanium thin film according to the first to fourth aspects of the present invention. .

In the lithium secondary battery according to the fifth aspect, two current collectors each having an active material layer provided on one surface are bonded to each other on the back surface as current collectors having active material layers provided on both surfaces. A thing may be used.

The current collector for a lithium secondary battery electrode according to the fifth aspect is characterized in that both surfaces have a surface formed by depositing an active material thin film for absorbing and releasing lithium.

As described above, the current collector of the fifth aspect preferably has substantially the same surface roughness Ra on both surfaces, and the surface roughness Ra on both surfaces is respectively equal to each other. It is preferably at least 0.01 m, more preferably 0.01 to l / xm.

The current collector of the fifth aspect is preferably a metal foil. When the active material thin film is a silicon thin film or the like, it is preferably a copper foil. The copper foil is preferably an electrolytic copper foil having a large surface roughness Ra. Examples of such an electrolytic copper foil include a copper foil roughened by depositing copper on both surfaces of the copper foil by an electrolytic method.

Hereinafter, the first to fifth aspects of the present invention will be described as “the present invention”. A lithium battery according to the present invention includes a negative electrode including the above-described electrode of the present invention, a positive electrode, and an electrolyte.

In the present invention, the term “lithium battery” includes a lithium primary battery and a lithium secondary battery. Therefore, the electrode of the present invention can be used for lithium primary batteries and lithium secondary batteries.

The lithium secondary battery of the present invention is characterized by comprising a negative electrode comprising the electrode of the present invention, a positive electrode, and a non-aqueous electrolyte.

The solvent for the electrolyte used in the lithium secondary battery of the present invention is not particularly limited, but cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate, and dimethyl carbonate, methylethyl carbonate, and getyl carbonate And a mixed solvent with a chain force of one. Further, a mixed solvent of the cyclic carbonate and an ether solvent such as 1,2 dimethoxetane or 1,2-diexoxetane, or a chain ester such as perbutylolactone, sulfolane, methyl acetate, or the like is also exemplified. The solutes of the electrolyte include L i PF ₆ , L i BF ₄ , L i CF ₃ S〇 ₃ , L i N (CF ₃ S 0 ₂ ) ₂ , L i N (C ₂ F ₅ S0 ₂ ) ₂ , L i N (CF ₃ S 0 ₂ ) (C ₄ F ₉ S 0 ₂ ), L i C (CF ₃ S 0 ₂ ) ₃ , L i C (C ₂ F ₅ S 0 ₂ ) L i A s _Fe , L i C l 〇 ₄ , _{_{_{L i 2 B 10 C 1 10}}} , L i 2 B 12 C 1 12 and the like and mixtures thereof are exemplified. Furthermore as an electrolyte, polyethylene O dimethylsulfoxide, Poriakurironi tolyl, or gel-like polymer one electrolyte electrolytic solution impregnated into polymer one electrolyte such as polyvinylidene mold two alkylidene, L i I, an inorganic solid electrolyte exemplified such as L i ₃ N Is done. The electrolyte of the lithium secondary battery of the present invention can be used as long as the L1 compound as a solvent that exhibits ionic conductivity and the solvent that dissolves and retains the L1 compound are not decomposed at the time of charging, discharging, or storing the battery. It can be used without any restrictions.

As the positive electrode active material of the lithium secondary battery of the present _{invention, L i C o 0 2,} L i N i 0 2, L i Mn 2 0 4, L i Mn 0 2, L i C o 0 5 N i 0 _{_{5 0 2, L i N i}} 0. 7 C o 0. 2 Mn 0. 1 0 2 lithium-containing transition metal oxides such as or a metal oxide not containing lithium such as Mn 0 ₂ is illustrated . In addition, any other substance capable of electrochemically inserting and removing lithium can be used without limitation.

The electrode of the present invention includes a non-aqueous electrolyte battery and a non-aqueous electrolyte using an electrode active material that absorbs and releases an alkaline metal such as sodium and potassium and an alkaline earth metal such as magnesium and calcium other than lithium. It is considered that it can also be used as an electrode for an electrolyte secondary battery. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic cross-sectional view showing a lithium secondary battery produced in an example of the present invention.

FIG. 2 is a scanning electron micrograph (2,000-fold magnification) showing a state of an electrode according to an embodiment of the present invention before charge and discharge.

FIG. 3 is a scanning electron micrograph (magnification: 5000) showing a state of an electrode according to an embodiment of the present invention before charge and discharge. FIG. 4 is a scanning electron micrograph (magnification: 500 times) showing the state of the electrode of one example according to the present invention after charging and discharging.

FIG. 5 is a scanning electron micrograph (magnification: 2500 times) showing the state of the electrode of one example according to the present invention after charging and discharging.

FIG. 6 is a scanning electron micrograph (magnification: 1000 times) showing a state in which the silicon thin film of the electrode of one embodiment according to the present invention is viewed from above.

FIG. 7 is a scanning electron micrograph (magnification: 500,000) showing a state in which the silicon thin film of the electrode of one embodiment according to the present invention is viewed from above.

FIG. 8 is a scanning electron microscope photograph (magnification: 1000) showing a state in which the silicon thin film of the electrode of one embodiment according to the present invention is viewed from a slightly oblique direction. FIG. 9 is a scanning electron micrograph (magnification: 500,000) showing a state in which the silicon thin film of the electrode of one embodiment according to the present invention is viewed from a slightly oblique direction. FIG. 10 is a schematic cross-sectional view showing a state in which a cut is formed in a silicon thin film and the silicon thin film is separated into columns in one embodiment of the present invention.

FIG. 11 is a transmission electron micrograph (magnification: 1/2500) showing a cross section of the silicon thin film of the electrode a3 according to the present invention.

FIG. 12 is a transmission electron micrograph (magnification: 250,000) showing a cross section of the silicon thin film of the electrode a6 according to the present invention.

FIG. 13 is a diagram schematically showing the electron micrograph shown in FIG. FIG. 14 is a diagram schematically showing the electron micrograph shown in FIG. FIG. 15 is a scanning electron micrograph (magnification: 10000) showing a state in which the surface of the silicon thin film of the electrode a3 according to the present invention is viewed from above.

FIG. 16 is a scanning electron micrograph (magnification: 10000) showing the surface of the silicon thin film of electrode a6 according to the present invention as viewed from above.

FIG. 17 is a diagram showing the concentration distribution of constituent elements in the depth direction of the silicon thin film of the electrode a6 according to the present invention. FIG. 18 is a schematic diagram showing a configuration of an apparatus for forming a thin film by a vacuum evaporation method in an embodiment of the present invention.

FIG. 19 is a scanning electron micrograph (magnification: 20000) showing the state before charge / discharge of electrode a7 according to the present invention.

FIG. 20 is a scanning electron micrograph (magnification: 1000 ×) showing the state before charge / discharge of electrode a7 according to the present invention.

FIG. 21 is a scanning electron micrograph (magnification: 20000) showing the state before charge / discharge of electrode a8 according to the present invention.

FIG. 22 is a scanning electron micrograph (100,000 magnification) showing a state before charging / discharging of electrode a8 according to the present invention.

FIG. 23 is a scanning electron micrograph (magnification: 500 times) showing the state after charge / discharge of electrode a7 according to the present invention.

FIG. 24 is a scanning electron micrograph (magnification: 2500 times) showing the state after charge / discharge of electrode a7 according to the present invention.

FIG. 25 is a scanning electron micrograph (magnification: 500 times) showing the state after charge / discharge of electrode a8 according to the present invention.

FIG. 26 is a scanning electron micrograph (magnification: 2500 times) showing the state after charge / discharge of electrode a8 according to the present invention.

FIG. 27 is a scanning electron micrograph (magnification: 1000 times) of the state of the germanium thin film after charging and discharging of the electrode a7 according to the present invention as viewed from above. FIG. 28 is a scanning electron micrograph (magnification: 500,000) of the state of the germanium thin film after charging and discharging of the electrode a7 according to the present invention, as viewed from above. FIG. 29 is a scanning electron micrograph (magnification: 1000) of the state of the germanium thin film after charging and discharging of the electrode a7 according to the present invention, viewed from a slightly oblique direction.

FIG. 30 shows the state of the germanium thin film after charging and discharging of the electrode a7 according to the present invention. 5 is a scanning electron micrograph (magnification: 500,000) of the state viewed from a slightly oblique direction.

FIG. 31 is a scanning electron micrograph (magnification: 1000 times) of the state of the germanium thin film after charging and discharging of the electrode a8 according to the present invention, as viewed from above. FIG. 32 is a scanning electron micrograph (magnification: 500,000) of the state of the germanium thin film after charging and discharging of the electrode a8 according to the present invention, as viewed from above. FIG. 33 is a scanning electron micrograph (magnification: 1000) of the state of the germanium thin film after charging and discharging of the electrode a8 according to the present invention, viewed from a slightly oblique direction.

FIG. 34 is a scanning electron micrograph (magnification: 500,000) of the state of the germanium thin film after charging / discharging of electrode a8 according to the present invention, viewed from a slightly oblique direction.

FIG. 35 is a scanning electron micrograph (magnification: 1000 times) of the state of the germanium thin film before charging and discharging of the electrode a7 according to the present invention, as viewed from above. FIG. 36 is a scanning electron micrograph (magnification: 1000 times) of the state of the germanium thin film before charging / discharging of the electrode a8 according to the present invention as viewed from above. FIG. 37 is a diagram showing the concentration distribution of constituent elements in the depth direction of the germanium thin film of the electrode a7 according to the present invention.

FIG. 38 is a diagram showing the concentration distribution of constituent elements in the depth direction of the germanium thin film of the electrode a8 according to the present invention.

FIG. 39 is a scanning electron micrograph (magnification: 20000) showing a cross section of electrode a11 before charge / discharge according to the present invention.

FIG. 40 is a scanning electron micrograph (magnification: 10000) showing a cross section of electrode a11 before charge / discharge according to the present invention.

FIG. 41 is a scanning electron micrograph (magnification: 10000) of the silicon thin film of the electrode all before charge and discharge according to the present invention as viewed from above. FIG. 42 is a scanning electron micrograph (magnification: 1000) of the silicon thin film of the electrode a11 after charging and discharging according to the present invention as viewed from above.

Figure 43 is a transmission electron micrograph (magnification: 500,000) showing the vicinity of the interface between the copper foil and the silicon thin film.

Figure 44 is a transmission electron micrograph (magnification: 1,000,000 times) showing the vicinity of the interface between the copper foil and the silicon thin film.

FIG. 45 is a diagram showing a copper and hydrogen concentration distribution in the depth direction of the mixed layer in the electrode c1.

FIG. 46 is a diagram showing a copper and hydrogen concentration distribution in the depth direction of the mixed layer in the electrode c3.

FIG. 47 is a perspective view showing a lithium secondary battery manufactured in another example of the present invention.

FIG. 48 is a schematic sectional view showing a lithium secondary battery produced in another example of the present invention.

FIG. 49 is a diagram showing the relationship between the thickness of the copper foil used for the electrode and the charge / discharge cycle characteristics.

FIG. 50 is a diagram showing the state of the negative electrode surface after charging and discharging.

FIG. 51 is a diagram showing a state of the negative electrode surface after charging and discharging.

FIG. 52 is a diagram showing a state of the negative electrode back surface after charging and discharging.

FIG. 53 is a diagram showing the state of the negative electrode back surface after charging and discharging.

FIG. 54 is a diagram showing the relationship between the thickness of the silicon thin film used for the electrode and the charge / discharge cycle characteristics.

FIG. 55 is a diagram showing the state of the back surface of the negative electrode after charging and discharging.

FIG. 56 is a plan view showing the negative electrode manufactured in the example of the fifth aspect of the present invention.

FIG. 57 shows a positive electrode produced in an example of the fifth aspect of the present invention. It is a top view.

FIG. 58 is a side view showing the negative electrode manufactured in the example of the fifth aspect of the present invention.

FIG. 59 is a plan view showing the lithium secondary battery manufactured in the example of the fifth aspect of the present invention.

FIG. 60 is a schematic sectional view showing a lithium secondary battery produced in an example of the fifth aspect of the present invention.

FIG. 61 is a partially cutaway perspective view showing an electrode structure in a stacked lithium secondary battery according to the fifth aspect of the present invention.

FIG. 62 is a perspective view showing a fifth local stacked lithium secondary battery of the present invention in which the electrode shown in FIG. 61 is housed in an outer package.

FIG. 63 is a schematic cross-sectional view showing an example of a laminate type lithium secondary battery according to the fifth aspect of the present invention.

FIG. 64 is a schematic sectional view showing an example of a coin-type lithium secondary battery according to the fifth aspect of the present invention.

FIG. 65 is a plan view showing an example of a coin-type lithium secondary battery according to the fifth aspect of the present invention.

FIG. 66 is an exploded perspective view showing an example of a cylindrical lithium secondary battery according to the fifth aspect of the present invention.

FIG. 67 is an exploded perspective view showing an example of the prismatic lithium secondary battery according to the fifth aspect of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited to the following Examples at all, and can be implemented with appropriate modifications within the scope of the gist of the present invention. It is something. (Experiment 1)

(Preparation of negative electrode)

The rolled copper foil (thickness 1 8 / X m) used as a substrate, using a silane (S i H ₄₎ as a raw material gas, using hydrogen gas as a carrier gas, microcrystalline silicon on top of the copper foil by CVD A thin film was formed. Specifically, a copper foil as a substrate was placed on a heater in the reaction chamber, and the pressure in the reaction chamber was evacuated to 1 Pa or less by a vacuum exhaust device. Thereafter, silane (SiH ₄ ) as a source gas and hydrogen (H ₂ ) gas as a carrier gas were introduced from a source gas introduction port, and the substrate was heated to 180 ° C. with a heater. The degree of vacuum was adjusted to a reaction pressure by a vacuum exhaust device, a high frequency was excited by a high frequency power supply, and the high frequency was introduced from an electrode to induce a glow discharge. Table 1 shows detailed thin film formation conditions. The unit of flow rate sccm in Table 1 is the volume flow rate (cm ³ / min) per minute at 0 ° C and 1 atm (10 1.33 kPa). Standard Cubic Centimeters Per Minute Is an abbreviation for

The microcrystalline silicon thin film was deposited under the above conditions until the thickness became about 10 μm. When this was observed with an electron microscope (magnification: 2 million), it was confirmed that the amorphous region was arranged around the crystal region composed of minute crystal grains, and that the region was amorphous. Next, the obtained sample was punched out to have a diameter of 17 mm to obtain an electrode a1. The same electrode a1 was heat-treated at 400 ° C. for 3 hours to obtain an electrode a2.

For comparison, 90 parts by weight of a commercially available single crystal silicon powder (particle diameter: 10 // m) and 10 parts by weight of polytetrachloroethylene as a binder were mixed. It was pressed with a mold having a diameter of 17 mm and pressed to obtain a pellet-shaped electrode b1.

(Preparation of positive electrode)

As a starting material, using L i ₂ CO _s and _{C o C0 3, L i:} C atomic ratio o 1: were weighed to be 1 were mixed in a mortar, gold which diameter 1 7 mm After pressing with a mold and pressing, the mixture was fired in air at 800 ° 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.

The obtained L i C o 0 ₂ powder 80 weight parts of acetylene black 1 0 parts by weight as the conductive material, the polytetramethylene full O b ethylene as a binder were mixed so that 1 0 part by weight, It was pressed in a 17 mm diameter mold and pressed to form a pellet-shaped positive electrode.

(Preparation of electrolyte solution)

In equal volume mixed solvent of ethylene carbonate and Jefferies chill carbonate, L i PF ₆ dissolved 1 mole liter to prepare an electrolyte solution, using the same in the production of the following cell.

(Production of battery)

Using the above electrodes a1, a2 and b1 as a negative electrode, the above positive electrode and electrolytic

Four Using the solution, a flat lithium secondary battery was manufactured.

Figure 1 is a schematic cross-sectional view of the fabricated lithium secondary battery.The positive electrode 1, the negative electrode 2, the separator 3, the positive electrode can 4, the negative electrode can 5, the positive electrode current collector 6, the negative electrode current collector 7, and the polypropylene Insulation packing consists of 8.

The positive electrode 1 and the negative electrode 2 face each other via the separator 3. 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 a positive electrode can 4 via a positive electrode current collector 6, and the negative electrode 2 is connected to a negative electrode can 5 via a negative electrode current collector 7, which allows charging and discharging as a secondary battery. It has a structure.

A battery using electrode a1 as a negative electrode was referred to as battery A1, a battery using electrode a2 as a negative electrode was referred to as battery A2, and a battery using electrode b1 as a negative electrode was referred to as battery B1.

(Measurement of charge / discharge cycle life characteristics)

At 25 ° C, the battery was charged at a current value of 100 A at a current value of 100 A until the anode capacity reached 2000 mAh / g, and then discharged.This was defined as one cycle of charge and discharge. Was measured. A cycle test was performed on the B1 battery that was not charged to 200 OmAhZg by charging it to 4.2 V and then discharging. Table 2 shows the results. Table A 2, the anode active material of each battery, the hydrogen concentration obtained by SIMS measurement, 4 8 0 cm ¹ near / "5 2 0 c m- ¹ peak intensity in the vicinity of ratio by Raman spectroscopy, and X-ray The diffraction spectrum and the crystal grain size calculated by the Scherrer's equation are also shown together.The crystal grain size of the battery B1 is assumed to be almost the same as the powder size. It shows the particle size. Table 2

As is clear from the results shown in Table 2, the batteries A1 and A2 according to the present invention show a significantly higher capacity retention ratio than the comparative battery B1.

As described above, by using the microcrystalline silicon thin film as the negative electrode active material, the charge / discharge cycle characteristics of the lithium secondary battery have been significantly improved. Since the expansion and shrinkage of lithium in the microcrystalline silicon thin film during absorption and desorption are alleviated, it is possible to suppress the pulverization of the negative electrode active material and suppress the deterioration of the current collection characteristics. .

(Experiment 2)

A microcrystalline silicon thin film (about 10 / zm thick) was formed on the electrolytic copper foil in the same manner as in Battery A1 of Experiment 1 except that an electrolytic copper foil (thickness: 18 μππ) was used as the current collector as the substrate. ) Was formed to produce electrode a3, and using this, battery A3 was produced.

The rolled copper foil used in Experiment 1 was polished with emery paper # 400 or # 120 for 1 minute to produce copper foil, and these copper foils were used as current collectors as substrates. In the same manner as for Battery A1 in Experiment 1 above, a microcrystalline silicon thin film (approximately 10 / m thick) was formed on a copper foil to produce electrodes. Electrode a 4 and emery paper # 1 2 The electrode a5 was polished with 0. Using these, batteries A4 and A5 were produced in the same manner as in Experiment 1 described above.

A charge-discharge cycle test was performed on these batteries A3 to A5 and the batteries A1 and B1 produced in Experiment 1 above under the same charge-discharge cycle conditions as in Experiment 1 above. The capacity retention was determined. Table 3 shows the results. Table 3 shows the surface roughness Ra and the average of the local peaks of the copper foil as the current collector of the batteries A1 and B1 and the copper foil as the current collector of the batteries A3 to A5. The interval S is also shown.

The surface roughness Ra of the copper foil and the average distance S between the local peaks were measured using a stylus type surface profiler D ektak ST (manufactured by Nippon Vacuum Engineering Co., Ltd.) with the measurement distance set to 2.0 mm. did. The calculation of the surface roughness Ra was performed after correcting the deflection. The correction values used for the deflection correction are low-pass = 200 / m and high-pass = 20 μm. The surface roughness Ra is a value automatically calculated, and the average interval S between local peaks is a value read from a chart. Table 3

As is evident from the results shown in Table 3, copper foil with a large surface roughness Ra Batteries A3 to A5, which used the current collector as a current collector, showed that the capacity retention rate at the 10th cycle was improved compared to battery A1, which used copper foil with a small surface roughness Ra. Understand. This is because the use of a copper foil with a large surface roughness Ra as the current collector improves the adhesion between the current collector and the active material, and expands the active material when occluding and releasing lithium. This is probably because the effect of the structural change of the active material due to shrinkage can be reduced.

(Experiment 3)

A further charge-discharge cycle test was performed on battery A1 prepared in Experiment 1 above and battery A3 prepared in Experiment 2 above under the same charge-discharge cycle conditions as in Experiment 1 above, and the capacity was maintained at the 30th cycle. The rate was determined. Table 4 shows the results. Table 4

As is clear from the results shown in Table 4, even at the 30th cycle, the battery A1 and the battery A3 show a good capacity retention rate. In particular, battery A3 using a copper foil having a large surface roughness Ra as a current collector shows a good capacity retention rate.

Therefore, the state of the silicon thin film of the electrode a3 used for the battery A3 was observed with an electron microscope. First, the electrode a3 before being incorporated into the battery, that is, before charging and discharging, was observed with a scanning electron microscope. Figures 2 and 3 are 3 is a scanning electron micrograph (secondary electron image) showing electrode a3 before charge and discharge. The magnification of FIG. 2 is 2000 times, and the magnification of FIG. 3 is 5000 times. The sample used was one in which the electrodes were embedded in resin and sliced. The layer observed at the upper end and the lower end in FIG. 2 and the layer observed at the upper end in FIG. 3 are the layers of the embedding resin.

In FIGS. 2 and 3, the slightly bright portion indicates a copper foil portion, and a silicon thin film (about 10 / m thick) is formed on the copper foil as a slightly dark portion. As shown in FIGS. 2 and 3, irregularities are formed on the surface of the copper foil, and particularly, the convex portions have a cone shape. The surface of the silicon thin film provided thereon also has irregularities similar to those of the copper foil. Therefore, it is considered that the irregularities on the surface of the silicon thin film are formed by the irregularities on the surface of the copper foil.

Next, the electrode a3 taken out of the battery A3 after the 30th cycle was embedded in a resin in the same manner and observed with a scanning electron microscope. The electrode a3 was taken out after discharging. Therefore, the observed electrode a3 is in a state after discharge.

4 and 5 are scanning electron microscope photographs (secondary electron images) showing the electrode a3 after the discharge. The magnification in FIG. 4 is 500 ×, and the magnification in FIG. 5 is 2500 ×.

As shown in FIGS. 4 and 5, it can be seen that a cut is formed in the silicon thin film in the thickness direction, and the cut separates the silicon thin film into a column shape. Although the cut is formed in the thickness direction, it is hardly formed in the surface direction, and it can be seen that the bottom of the columnar portion is in close contact with the copper foil as the current collector. In addition, the upper part of the columnar part has a rounded shape, and it can be seen that a cut is formed from the uneven valley on the surface of the silicon thin film before charging and discharging. Further, the surface of the silicon thin film of the electrode a3 after charging and discharging was observed with a scanning electron microscope. FIGS. 6 and 7 are scanning electron micrographs (secondary electron images) of the surface of the silicon thin film observed from above. The magnification of FIG. 6 is 100 ×, and the magnification of FIG. It is twice. 8 and 9 are scanning electron micrographs (secondary electron images) of the surface of the silicon thin film observed from a slightly oblique direction. The magnification of FIG. 8 is 100 ×, and the magnification of FIG. It is 0 times. As shown in FIGS. 6 to 9, a cut is formed around the columnar portion of the silicon thin film, and a gap is provided between the columnar portion and the adjacent columnar portion. Therefore, even when the silicon thin film absorbs lithium during charging and the columnar portion expands and its volume increases, the gap formed around the columnar portion can absorb this volume increase. I think that the. In addition, during discharge, the columnar portion of the silicon thin film releases lithium and contracts, so that the volume is reduced again and a gap is likely to be formed around the columnar portion. It is thought that such a columnar structure of the silicon thin film can alleviate the expansion and contraction of the active material during charging and discharging.

In addition, cuts are formed in the silicon thin film, and the silicon thin film is separated into columns, thereby greatly increasing the contact area with the electrolyte. In addition, since the columnar portions are formed with approximately the same size, it is considered that the charge / discharge reaction involving the occlusion and release of lithium is efficiently performed in the active material thin film. Also, as shown in FIGS. 4 and 5, each columnar portion of the silicon thin film is in close contact with the current collector, so that the active material is electrically connected to the current collector in a good condition. It seems that the charge / discharge reaction can be performed efficiently. Further, as shown in FIGS. 6 to 9, the upper part of the columnar portion has a rounded shape. Therefore, the electrode structure is such that current concentration hardly occurs and lithium metal precipitation reaction does not easily occur.

Figure 10 shows that a cut is formed in the silicon thin film formed on the copper foil, FIG. 4 is a schematic cross-sectional view showing a step of separating the wafer into a shape.

As shown in FIG. 10 (a), irregularities are formed on the surface 10 a of the copper foil 10. Such irregularities become larger as the copper foil has a larger value of the surface roughness Ra.

FIG. 10 (b) shows a state in which the amorphous silicon thin film 11 is deposited on the surface 10a of the copper foil 10 on which the irregularities are formed. The surface 11 a of the silicon thin film 11 is affected by the unevenness of the surface 10 a of the copper foil 10 and has the same unevenness as the unevenness of the surface 10 a of the copper foil 10. Before charging and discharging, the silicon thin film 11 is a continuous thin film as shown in FIG. 10 (b). When charging is performed in such a state, lithium is absorbed in the silicon thin film 11 and the volume of the silicon thin film 11 expands. The expansion of the silicon thin film 11 at this time is a force s which is considered to occur in both the surface direction and the thickness direction of the thin film, and details thereof are not clear. Next, during the discharge reaction, a silicon thin film

Lithium is released from 11 and the volume shrinks. At this time, tensile stress occurs in the silicon thin film 11. Such stress is probably concentrated at the valleys 1 1b of the irregularities on the surface 11 a of the silicon thin film 11, and therefore, as shown in FIG. 10 (c), the starting point at the valleys 1 1 b It is considered that a cut 12 is formed in the thickness direction. It is considered that the stress is released by the cuts 12 thus formed, and the silicon thin film 11 is shrunk without the silicon thin film 11 peeling off from the copper foil 10.

As described above, the silicon thin film separated into a columnar shape in the subsequent charge / discharge cycle reduces the expansion and contraction of the active material due to the gap formed around the columnar portion, as described above. It seems that the charge / discharge cycle can be repeated without the active material peeling off from the current collector.

Furthermore, in order to study the mechanism by which a break is formed in the silicon thin film, a microcrystalline silicon thin film with a thickness of about 10 μm was formed on the electrolytic copper foil. The formed electrode a3 was observed with a transmission electron microscope. FIG. 11 is a transmission electron micrograph (magnification: 1250 ×) showing a cross section of electrode a3 before charging and discharging. The observed sample was obtained by embedding the electrode in a resin and slicing it.

FIG. 13 is a diagram schematically showing the transmission electron microscope photograph shown in FIG. In the transmission electron micrograph shown in FIG. 11, a silicon thin film 11 is formed on the surface 10 a of the electrolytic copper foil 10 as shown in FIG. In the transmission electron micrograph, the silicon thin film 11 is shown as a portion brighter than the copper foil 10. Observing the silicon thin film 11 shown in FIG. 11, the surface 11 a of the silicon thin film 11 1 and the valley 11 b of the unevenness of the surface 10 a of the copper foil 10 1 10 b A brighter part is observed in the region connecting b. In FIG. 13, the bright portions are indicated by dashed lines as A, B and C. Particularly in the region indicated by A, a bright portion is more clearly observed. These regions are considered to be regions having a low density in the silicon thin film 11, that is, low-density regions. In order to observe this low-density region in more detail, an electrode a6 in which a microcrystalline silicon thin film having a thickness of about 2 m was formed on an electrolytic copper foil under the same conditions as the electrode a3.

FIG. 12 is a transmission electron microscope photograph when the electrode a6 was observed with a transmission electron microscope in the same manner as described above. In FIG. 12, the magnification is 25000 times. FIG. 14 is a diagram schematically showing the transmission electron micrograph shown in FIG. As is clear from FIG. 12, also in the electrode a 6, the valleys 1 1 b of the surface 11 a of the silicon thin film 11 1 and the valleys 1 1 b of the surface 10 a of the copper foil 10 1 A low-density region is observed in the region D connecting 0b.When the photograph of FIG. 12 is observed in more detail, fine streaks extending in the direction indicated by the arrow in FIG. 14 are observed in the silicon thin film 11. You. This line is It is thought that it is probably formed with the growth of the silicon thin film. Therefore, it is considered that the silicon thin film 11 grows in a direction substantially perpendicular to the surface 10a of the copper foil 10. Then, the layer of silicon thin film growing in such a direction collides with the layer deposited and grown on the inclined surface of the adjacent copper foil surface in the area D, and as a result, the low density It is thought that a region will be formed. It is thought that such collision of the silicon thin film layers will continue until the formation of the thin film is completed, and the low density region will continue to be formed up to the surface of the silicon thin film.

FIG. 15 is a scanning electron micrograph (secondary electron image) of the surface of the electrode a3 observed from above. The electrode a3 shown in FIG. 15 is in a state before charge and discharge. The magnification in FIG. 15 is 1000 times. In Fig. 15, the bright part is the convex part of the silicon thin film surface, and the surrounding dark part is the valley part of the silicon thin film surface. As shown in Fig. 15, the valleys on the surface of the silicon thin film are connected in a network. Therefore, it can be seen that the low-density region in the silicon thin film is formed in a network in the plane direction. Such a network-like low-density region further extends in the thickness direction toward the current collector, as shown in FIGS. 11 and 13. The fact that the dark part in FIG. 15 is not a cut (void) is apparent from the fact that no cut (void) is observed in the thickness direction in the scanning electron microscope photographs shown in FIGS.

FIG. 16 is a scanning electron micrograph (secondary electron image) of the surface of the electrode a6 before charging / discharging, observed from above, with a magnification of 1000 times. As is evident from Fig. 16, the valleys are also connected in a mesh pattern in the electrode a6, and thus the low-density region is connected in a mesh pattern in the plane direction. FIG. 4 is a diagram showing a concentration distribution of constituent elements in a depth direction of a silicon thin film. The concentration distribution of the constituent elements is ₂ + using a sputtering source, the horizontal axis in. FIG. 1 7 was performed by measuring the concentration of a copper element ⁽⁶³ C u one and silicon elements (S i ² +) is the depth from the silicon thin film surface (Zm), and the vertical axis indicates the strength (count) of each constituent element.

As is clear from Fig. 17, near the current collector, copper (Cu), which is a component of the current collector, diffuses into the silicon thin film, and the component of the current collector becomes closer to the surface of the silicon thin film. It can be seen that the concentration of certain copper (Cu) has decreased. In addition, since the concentration of copper (Cu) is continuously changing, in the region where copper (Cu) is diffused, a solid solution of silicon and copper is used instead of an intermetallic compound of silicon and copper. It can be seen that is formed.

In view of the above, the mechanism by which a break in the thickness direction is formed in the silicon thin film due to expansion and contraction of the silicon thin film due to charge and discharge is considered as follows. That is, as described with reference to FIG. 10, the stress generated by the expansion and contraction of the volume of the silicon thin film concentrates on the valley of the unevenness on the surface of the silicon thin film, and also flows from the valley toward the current collector below. A low-density region previously exists, and since the low-density region is a portion having low mechanical strength, it is considered that a cut (void) is formed along the low-density region.

Furthermore, as shown in Fig. 17, the copper element, which is a component of the current collector, is diffused in the silicon thin film, and the concentration of copper is high near the current collector, and as it approaches the surface of the silicon thin film, It has a concentration gradient in which the concentration of copper is small. Therefore, the concentration of copper that does not react with lithium increases near the current collector, and the concentration of silicon that reacts with lithium decreases. For this reason, it is thought that the absorption and release of lithium are small near the current collector, and the expansion and contraction of the silicon thin film are relatively small. For this reason, the stress generated in the silicon thin film near the current collector is reduced, and the silicon thin film near the current collector is reduced.

Five It is unlikely that breaks (voids) that would separate or detach from the current collector would occur, and the bottom of the columnar portion of the silicon thin film would be able to maintain close contact with the current collector.

The silicon thin film separated into columns by the cuts formed as described above is firmly adhered to the current collector even in the charge / discharge cycle, and is filled by the gaps formed around the columnar portions. It is thought that excellent charge / discharge cycle characteristics can be obtained because the expansion and contraction of the thin film due to the discharge cycle are alleviated.

(Experiment 4)

[Preparation of electrode a 7]

The same electrolytic copper foil as that used for the electrode a3 was used as the current collector as the substrate, and an amorphous germanium thin film (about 2 / zm thick) was formed on this by RF sputtering. Electrode a7 was produced.

The thin film forming conditions were as follows: target: germanium, sputtering gas (Ar), flow rate: 100 sccm, substrate temperature: room temperature (no heating), reaction pressure: 0.1 Pa, and high-frequency power: 200 W.

When the obtained germanium thin film was analyzed by Raman spectroscopy, a peak near 274 cm- ¹ was detected, but a peak near 300 cm- ¹ was not detected. From this, it was confirmed that the obtained germanium thin film was an amorphous germanium thin film.

[Preparation of electrode a 8]

Using the same electrolytic copper foil as the current collector of the electrode a7, an amorphous germanium thin film (about 2 μηι) was formed thereon by vapor deposition to produce an electrode a8.

Specifically, a germanium thin film was formed on the substrate using the apparatus having the configuration shown in FIG. Referring to FIG. 18, the ECR plasma source 81 has a A plasma generation chamber 82 is provided, and a microwave power 85 and an Ar gas 86 are supplied to the plasma generation chamber 82. When microwave power 85 is supplied to the plasma generation chamber 82, Ar plasma is generated. The Ar plasma 83 is drawn out of the plasma generation chamber 82 and irradiated on the substrate 80. An electron beam (EB) gun 84 is provided below the substrate 80, and a germanium thin film can be deposited on the substrate 80 by the electron beam from the electron beam gun 84.

Before depositing a germanium thin film on the electrolytic copper foil as a substrate, Ar plasma was irradiated on the substrate to perform pretreatment. The vacuum degree in the reaction chamber to about 0. 0 5 P a and (about ^{5 X 1 0- 4 T orr)} , A r gas flow rate was between 4 0 sccm, A microphone port wave power supplies as 2 0 0 W r Plasma was irradiated on the substrate. When irradiating Ar plasma, a bias voltage of −100 V was applied to the substrate. Pretreatment was performed by irradiating Ar plasma for 15 minutes. Next, a germanium thin film was deposited on the substrate by an electron beam gun at a deposition rate of 1 nm / sec (10 AZ seconds). The substrate temperature was room temperature (no heating).

When the obtained germanium thin film was subjected to Raman spectroscopic analysis, it was confirmed that it was an amorphous germanium thin film, similarly to the electrode a7.

[Preparation of electrode b2]

Using germanium powder with an average particle diameter of 10 μm, germanium powder is 80 parts by weight, acetylene black as a conductive material is 10 parts by weight, and polytetrafluoroethylene as a binder is 10 parts by weight. Then, the mixture was pressed with a mold having a diameter of 17 mm and pressed to form a pellet-shaped electrode b2.

(Production of battery)

The above-mentioned electrodes a7, a8 and b2 were used as negative electrodes, and other In the same manner as in the above, a lithium secondary battery was produced. A battery using the electrode a7 as a negative electrode was referred to as a battery A7, a battery using the electrode a8 as a negative electrode was referred to as a battery A8, and a battery using the electrode b2 as a negative electrode was referred to as a battery B2.

(Evaluation of charge / discharge cycle characteristics)

For each of the above batteries, charge the battery at 0.1 mA with a current of 0.1 mA until the charging voltage reaches 4.2 V, then discharge it until the charging voltage reaches 2.7 V, and cycle this for one cycle. , And the capacity retention ratio at the 10th cycle was measured. Table 5 shows the measurement results. Table 5

As is evident from Table 5, the batteries A7 and 8 using the electrode of the present invention in which the germanium thin film was formed on the current collector as the negative electrode were compared with the battery B2 using the germanium powder as the negative electrode material. It shows a very good capacity retention rate.

[Observation by electron microscope]

FIGS. 19 and 20 are scanning electron micrographs (backscattered electron images) showing a cross section of the electrode a7 before charge and discharge. The magnification of FIG. 19 is 2000 ×, and the magnification of FIG. 20 is 1000 ×.

For the sample, the electrode was embedded in resin and sliced. The layer observed at the upper end and the lower end in FIG. 19 and the layer observed at the upper end in FIG. 20 are the layers of the embedding resin.

In FIGS. 19 and 20, the bright portions are the copper foil and the germanium thin film, the thin layer on the surface of the bright portion is the germanium thin film, and the copper foil is below. Irregularities are formed on the surface of the copper foil, and irregularities similar to those of the copper foil are also formed on the surface of the germanium thin film provided thereon. Therefore, it is considered that the irregularities on the germanium thin film surface were formed by the irregularities on the copper foil surface.

In FIG. 20, a dark portion extending in the thickness direction of the thin film is observed in the region of the germanium thin film on the valley at the left end of the copper foil. This portion is a low-density region in the germanium thin film, that is, Probably a low density region.

FIGS. 21 and 22 are scanning electron micrographs (backscattered electron images) showing the cross section of the electrode a8 before charging and discharging. The magnification in FIG. 21 is 2000 times, and the magnification in FIG. 22 is 1000 times. The sample is embedded in the resin similarly to the electrode a7 shown in FIGS. 19 and 20.

In FIGS. 21 and 22, the bright part indicates the copper foil part, and a germanium thin film (about 2 / m thick) is formed on the copper foil as a slightly dark part. Similarly to the electrode a7, the electrode a8 has the same irregularities as the copper foil on the surface of the germanium thin film.

FIGS. 23 and 24 are scanning electron microscope photographs (backscattered electron images) showing the cross section of the electrode a7 taken out of the battery A7 after 10 cycles. FIGS. 25 and 26 are scanning electron microscope photographs (backscattered electron images) showing the cross section of the electrode a8 taken out of the battery A8 after 10 cycles. In each case, the electrodes were embedded in resin and sliced. The magnification of FIGS. 23 and 25 is 500 times, and the magnification of FIGS. 24 and 26 is double. The rate is 2500 times.

23 to 26, the white part observed on the surface of the germanium thin film is gold coated on the surface of the germanium thin film when embedded in the embedding resin. The reason for coating with gold in this way is to prevent the reaction between the germanium thin film and the resin and to clarify the boundary between the resin and the germanium thin film.

As is clear from FIGS. 23 to 26, in the case of a germanium thin film, as in the case of a silicon thin film, a break is formed in the thickness direction of the thin film by charging and discharging, and the cut forms the thin film into a columnar shape. You can see that they are separated. Also, there is not much difference in contrast between the copper foil and the germanium thin film, which are current collectors, so the boundaries are easy to understand. It can be seen that a germanium thin film is present, and that the germanium thin film is in close contact with the current collector.

Unlike the silicon thin film, the germanium thin film also shows a cut in the lateral direction, but such a cut may have occurred when the germanium thin film was polished for cross-sectional observation.

Also, in the case of a germanium thin film, the width of the gap (void) between the columnar portions is larger than that of the silicon thin film. This is because the height of the columnar part after charging and discharging is about 6 μπι, which is about three times higher than the film thickness of 2 μm before charging and discharging. However, when contracted by electric discharge, it contracts mainly in the horizontal direction, that is, in the plane direction, and the shrinkage rate in the thickness direction is small, so the width of the gap between the columnar parts (gap) seems to be large. .

FIGS. 27 and 28 are scanning electron micrographs (secondary electron images) of the surface of the germanium thin film of the electrode a7 after charging / discharging, observed from above. The magnification of FIG. The magnification in FIG. 28 is 0 ×, and the magnification in FIG. Fig. 29 Fig. 30 is a scanning electron micrograph (secondary electron image) of the surface of the germanium thin film of the electrode a7 after charging and discharging, observed from a slightly oblique direction. The magnification in FIG. 30 is 5000 times.

FIGS. 31 and 32 are scanning electron micrographs (secondary electron images) of the surface of the germanium thin film of the electrode a8 after charging / discharging, observed from above. The magnification of FIG. The magnification in FIG. 32 is 5000 times. Figures 33 and 34 are scanning electron micrographs (secondary electron images) of the surface of the germanium thin film of electrode a8 after charging and discharging, observed from a slightly oblique direction. The magnification of Figure 33 is 1 The magnification is 0000, and the magnification in FIG. 34 is 50,000.

As shown in FIGS. 27 to 34, cuts (voids) are formed around the columnar portions of the germanium thin film, and gaps are provided between adjacent columnar portions. Therefore, it is considered that the expansion and contraction of the active material during charging and discharging can be reduced as in the case of the silicon thin film described above.

Figure 35 is a scanning electron micrograph (secondary electron image) of the surface of the germanium thin film of electrode a7 before charging and discharging, observed from above. Figure 36 is a scanning electron micrograph (secondary electron image) of the surface of the germanium thin film of electrode a8 before charging and discharging, observed from above. The magnification in FIGS. 35 and 36 is 1000 times.

As shown in FIGS. 35 and 36, irregularities are formed on the surface of the germanium thin film along the convexity of the underlying electrolytic copper foil. The valleys of the germanium thin film are connected in a network. Notches (voids) are formed along the thickness direction of such valleys, and columnar portions of the germanium thin film are formed.

Analysis of concentration distribution in the depth direction by CSIMS)

FIG. 37 is a diagram showing the concentration distribution of constituent elements in the depth direction of the electrode a7 before being incorporated in the battery, that is, before charging and discharging. Figure 38 also shows FIG. 9 is a view showing a concentration distribution of constituent elements in a depth direction of an electrode a8 before discharge. The concentration distribution of the constituent elements was determined by using secondary ion mass spectrometry (SIMS) to determine the concentrations of copper ( ⁶³ Cu-) and germanium ( ⁷³ Ge-) using 0 ₂ + as the sputtering source. From the depth direction. The horizontal axis indicates the depth (μπι) from the surface of the germanium thin film, and the vertical axis indicates the intensity (count number) of each constituent element.

As is clear from Figs. 37 and 38, near the current collector, copper (Cu), a component of the current collector, diffused into the germanium thin film, and the current was collected as it approached the surface of the germanium thin film. It can be seen that copper (Cu), a body component, has been reduced.

As described above, in the germanium thin film, the copper element which is a component of the current collector is diffused, and the copper concentration is high near the current collector, and the copper concentration decreases as approaching the germanium thin film surface. It has a concentration gradient. Therefore, near the current collector, the concentration of copper that does not react with lithium increases, and the concentration of germanium that reacts with lithium decreases. Therefore, it is considered that the absorption and release of lithium are small near the current collector, and the expansion and contraction of the germanium thin film are relatively small. For this reason, the stress generated in the germanium thin film near the current collector is reduced, and in the vicinity of the current collector, cuts (voids) that cause the germanium thin film to peel or detach from the current collector are not easily generated. It is considered that the bottom of the columnar portion of the germanium thin film can maintain close contact with the current collector.

As described above, the columnar-separated germanium thin film is firmly adhered to the current collector even in the charge / discharge cycle, and the gap formed around the columnar part causes the charge / discharge cycle It is thought that since the stress generated by the expansion and contraction of the thin film is relieved, excellent charge / discharge cycle characteristics can be obtained. (Experiment 5)

[Preparation of electrode a 9]

An electrolytic copper foil (18 / m thick) was used as a current collector as a substrate, and a silicon thin film was formed on the electrolytic copper foil by RF sputtering. Conditions spa Ttaringu a sputtering gas (A r) flow rate: 1 00 sccm, board temperature: room temperature (no heating), reaction pressure: 0. l P a (1. 0 X 1 0- 3 T orr), high frequency Power: 200 W conditions. The silicon thin film was deposited until its thickness was about 2 μm.

The resulting silicon thin film was subjected to Raman spectroscopic analysis, 4 80 cm ^_1 peak in the vicinity were detected, 520 cm- ¹ near the peak was not detected. This indicates that the obtained silicon thin film is an amorphous silicon 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 produce an electrode a9.

The surface roughness Ra of the electrolytic copper foil used and the average distance S between the local peaks were set to 2.Omm using a stylus type surface shape measuring device Dektat ³ ST (manufactured by Nippon Vacuum Engineering Co., Ltd.). Measured. The surface roughness Ra was 0.188 / m, and the average distance S between the local peaks was 11 μπι.

[Preparation of electrode a10]

The same as the electrode a1 in the above experiment 1 except that the same current collector as the substrate was used as the electrodeposited copper foil used in the production of the electrode a9, and the thickness of the silicon thin film was about 2 / im. Under the conditions, a silicon thin film was formed on an electrolytic copper foil, and an electrode a10 was produced in the same manner as the electrode a9.

The resulting silicon thin film was subjected to Raman spectroscopic analysis, a peak of 4 80 cm- ¹ near both 5 20 cm- ¹ near the peak is detected. Therefore, the obtained silicon thin film is a microcrystalline silicon thin film. (Preparation of comparative electrode b3)

The rolled copper foil used in Experiment 1 above was used as a current collector as a substrate, and an amorphous silicon thin film (about 2 m thick) was formed by RF sputtering in the same manner as in the preparation of electrode a9.

Next, the obtained amorphous silicon thin film was subjected to an annealing treatment at 65 ° C. for 1 hour. When Raman spectroscopy was performed on the silicon thin film after the ayur treatment, the peak near 480 cm- ¹ disappeared, and only the peak near 520 cm- ¹ was detected. Therefore, it was confirmed that a polycrystalline silicon thin film was formed by the annealing treatment.

Using the polycrystalline silicon thin film formed on the rolled copper foil, an electrode b3 was produced in the same manner as the electrode a9.

For the rolled copper foil, the surface roughness Ra and the average distance S between the local peaks were measured in the same manner as above.The surface roughness Ra was 0.037 / m, and the average distance between the local peaks. S was 14 μm.

(Measurement of charge / discharge characteristics)

A test cell was prepared using the electrode a9, electrode a10, and electrode b3 obtained above as a working electrode, and using lithium as a counter electrode and a reference electrode. The same electrolyte as that prepared in Experiment 1 was used as the electrolyte. In a unipolar test cell, the reduction of the working electrode is charged and the oxidation is discharge.

Each of the above test cells was charged at a constant current of 0.5 mA at 25 ° C until the potential with respect to the reference electrode reached 0 V, and then discharged until the potential reached 2 V . This was defined as one cycle of charge and discharge, and the discharge capacity and charge and discharge efficiency at the first and fifth cycles were measured. Table 6 shows the results. Table 6

As is clear from the results shown in Table 6, according to the present invention, the electrode a9 using an amorphous silicon thin film as an electrode active material and the electrode a10 using a microcrystalline silicon thin film as an electrode active material were polycrystalline silicon. Compared to the comparative electrode b3 using a thin film as the electrode active material, it shows a higher discharge capacity and a good charge / discharge efficiency even at the fifth cycle.

(Experiment 6)

Examples 1-7 and Comparative Examples 1-2>

(Preparation of current collector)

Samples 1 to 4 shown in Table 7 were used as current collectors serving as substrates. Sample 1 is the same as the piezoelectric copper foil used as the current collector in electrode b3. Samples 2 to 4 use a rolled copper foil surface

6 The surface is polished and roughened with 100, # 400, and # 100, then washed with pure water and dried. Table 7

Using the above copper foil as a substrate, a silicon thin film was deposited on the substrate under the conditions shown in Tables 8 to 10 using an RF argon sputtering apparatus. For Comparative Example 2, heat treatment (annealing) was performed after the formation of the thin film. In Examples 1 to 7 and Comparative Example 1, pretreatment was performed on the substrate before forming the thin film. The pretreatment was performed by generating ECR argon plasma using a separately provided plasma source and irradiating the substrate with microwave power of 200 W and argon gas partial pressure of 0.06 Pa for 10 minutes. .

Raman spectroscopy was performed on the silicon thin film to identify its crystallinity. The results are shown in Tables 8 to 10.

(Measurement of charge / discharge characteristics)

The silicon thin films formed on the copper foils of Examples 1 to 7 and Comparative Examples 1 and 2 were cut into a size of 2 cm × 2 cm, and test cells were produced in the same manner as in Experiment 5 described above. For each test cell, a charge / discharge test was performed in the same manner as in Experiment 5, and the discharge capacity and charge / discharge efficiency at the first cycle, fifth cycle, and 20th cycle were measured. The results are shown in Tables 8 to 10. Table 8 Example 1 Example 2 Example 3 Example 4 Substrate Type of substrate Substrate 2 Sample 3 Sample 3 Sample 4

Appearance R a 0.10.18 1 0.18 only 18 m 18 / m / 8 μ τη Thin film silicon 2 ^ τη 2 μ τη 2 μ ηι

Sputtering gas Sputtering gas Sparging gas Argon Argon Argon Argon

A r ^ iM lOOsccra lOOsccm lOOsccm lOOsccm Evening target 99.999¾ 99.999X 99.999¾

Si nanocrystal Si single crystal Si decrystallized sputtering atmosphere 0.10Pa 0.10Pa 0.10Pa 0.10Pa

Ma

Sputtering power 200W 200W 2001 200W Substrate i¾ 20 ° C 20 ° C 20 ° C 200 ° C Pretreatment Yes Yes Yes Yes Sputter time 2¾ 2 hours 2 hours 2 hours Summary None None None None Processing time

Crystallinity identification Raman dSOcnr ¹ Yes Yes Yes Yes

Raman 520 cm ¹ None None None None Crystalline amorphous Amorphous Amorphous Amorphous Amorphous

1st cycle ¾¾® capacity (mAh / g) 3980 3978 3975 <ί980

碰 conversion rate (¾) 100 100 100 100

5th cycle Volume (raAh / g) 3990 3981 3980 3990

100 100 100 100

20th cycle ¾¾ Capacity (mAh / g) 3990 3980 3981 3990

Rate (¾) 100 100 100 100 Table 9

Table 10

Dislike 1 t 瞧 2 Substrate Type of board Sample 3 Sample 1.

丽さ R a 0. 18 0. 037 ■ ^ ν Ι μ ν Thin film type 件リ μ ηχ 2 β χη

A r WM lOOsccm lOOsccm Turquet 99.999Λ 99.999¾

Si-crystallized Si-crystallized sputter atmosphere ffi ^ 0.10Pa 0. lOPa Sputter ¾Λ 2001 200 * Substrate-450 ° C 20 ° C Pretreatment Yes No Sputter time 2 hours 2 hours s ^ fr mm No 650 ° C

Processing time-1 hour Crystallinity identification Raman 480cnf 'No No Raman 520cm- ¹ Yes Yes Crystalline Polycrystalline Polycrystalline

1st cycle «C« capacity (inAh / g) 1250 1978

Rate (¾) 81 83

5th cycle amount (mAh / g) 900 731

% 75 75

(20th cycle OnAh / g) 700 350

Male «¾ rate (¾) 69 59 As is clear from the results shown in Tables 8 to 10, in Examples 1 to 7 in which the amorphous silicon thin film was used as the electrode active material according to the present invention, the polycrystalline silicon thin film was used as the electrode active material. Compared to Comparative Examples 1 and 2, a higher discharge capacity was obtained, and good charge / discharge cycle characteristics were obtained.

(Experiment 7)

An amorphous silicon thin film (about 3 μππι thick) was deposited on the electrolytic copper foil (18 μm thick, surface roughness Ra = 0.18 μm, average spacing S = 6 m) by RF sputtering. ) Was formed to produce an electrode a11. The conditions for forming the thin film were as follows: target: single-crystal silicon, sputtering gas (Ar) flow rate: 100 sccm, substrate temperature: room temperature (no heating), reaction pressure: 0.1 Pa, high-frequency power: It was set to 200 W.

When the obtained silicon thin film was analyzed by Raman spectroscopy, a peak near 480 cm- ¹ was detected, but a peak near 520 cm- ¹ was not detected. This indicates that the obtained silicon thin film is an amorphous silicon thin film.

Using the obtained electrode a11, a battery A11 was produced in the same manner as in Experiment 1 above, and a charge-discharge cycle test was performed under the same charge-discharge cycle conditions as in Experiment 1 above. The capacity retention was determined. Table 11 shows the results. Table 11 also shows the results for Battery A1 and Battery A3.

Battery 30th cycle capacity retention rate

A 19 1%

A 39 1%

A 1 1 9 7% As is clear from the results shown in Table 11, the battery A1.1 using the amorphous silicon thin film formed by the sputtering method as the active material was the same as the battery A1 using the microcrystalline silicon thin film as the active material. Similar to A3, it shows a good capacity retention rate.

The state of the silicon thin film of the electrode a11 was observed with an electron microscope. First, a cross section of the electrode a11 before charge and discharge was observed with a scanning electron microscope. FIG. 39 and FIG. 40 are scanning electron micrographs (secondary electron images) showing the cross section of the electrode a11 before charging and discharging, respectively. The magnification of FIG. 39 is 2000 ×, and the magnification of FIG. 40 is 1000 ×. As in the samples shown in FIGS. 2 and 3, electrodes were embedded in resin and sliced.

In FIG. 39 and FIG. 40, the slightly bright portion indicates the portion of the electrolytic copper foil, and the silicon thin film (thickness of about 3 // m) is shown as a slightly dark portion on the copper foil. As shown in FIGS. 39 and 40, irregularities are formed on the surface of the electrolytic copper foil, and the convex portions have a cone shape. Irregularities similar to those of the copper foil are also formed on the surface of the silicon thin film provided thereon, and the convex portions have a cone shape.

. Therefore, the irregularities on the surface of the silicon thin film are formed by the irregularities on the surface of the copper foil.

Fig. 41 is a scanning electron microscope photograph (secondary electron image) showing the surface of the silicon thin film of the electrode a11, and the magnification is 1000 times. As shown in FIG. 41, a large number of projections are formed on the surface of the silicon thin film. As shown in FIGS. 39 and 40, the projections are formed corresponding to the projections on the copper foil surface.

Fig. 42 is a scanning electron micrograph (2) showing the surface of the silicon thin film of the electrode a11 taken out of the battery A11 after 30 cycles of the charge / discharge test. Secondary electron image). The magnification of the photograph shown in FIG. 42 is 1000 times. As shown in FIG. 42, cuts (gaps) are formed in the silicon thin film in the thickness direction, and the cuts (gaps) separate the silicon thin film into columns. In the silicon thin film shown in Figs. 6 to 9, the notch is formed so that the columnar portion includes one protrusion on the surface of the thin film, whereas in the silicon thin film shown in Fig. 42, the columnar portion is formed on the surface of the thin film. It can be seen that the cut is formed so as to include a plurality of protrusions. Also, the width of the cut (gap) is larger than that of the silicon thin film shown in FIGS.

Battery A11 shows a similar good capacity retention as battery A3. Therefore, as shown in FIG. 42, even when the columnar portion is formed so as to include a plurality of convex portions on the thin film surface, the active material is formed by the gap formed around the columnar portion. It is thought that the charge / discharge cycle can be repeated without the active material peeling off from the current collector because the stress caused by the expansion and contraction of the material is reduced.

(Experiment 8)

Under the same thin film formation conditions as those used for preparing electrode a1 in Experiment 1, a microcrystalline silicon thin film with a film thickness of about 2 // m was formed on rolled copper foil and electrolytic copper foil (thickness: 18 m). did. Next, the obtained sample was punched out to have a diameter of 17 mm, and the electrode formed on the rolled copper foil was designated as electrode c1, and the electrode formed on the electrolytic copper foil was designated as electrode c3. The same electrode c1 and electrode c3 were heat-treated at 400 ° C. for 3 hours in the same manner as electrode a2 in Experiment 1 to obtain electrode c2 and electrode c4, respectively.

Lithium secondary batteries were produced in the same manner as in Experiment 1 except that the above-mentioned electrodes cl to c4 were used as the negative electrodes, and batteries C1 to C4 were obtained. The charge / discharge cycle life characteristics of these batteries were measured in the same manner as in Experiment 1 above. In addition, as in Experiment 1, the hydrogen content and The peak intensity ratio (480 cm ^-1 /520 cm- ¹ ) and the crystal grain size in the diffraction spectroscopy were measured, and the results are shown in Table 12. Table 1 2

As is evident from the results shown in Table 12, remarkably high capacity retention rates were obtained also in batteries C1 to C4 in which the thickness of the microcrystalline silicon thin film was about 2 // m.

Next, the electrode c1 in which the microcrystalline silicon thin film was formed on the rolled copper foil was sliced in the thickness direction to obtain a microscope observation sample, which was observed with a transmission electron microscope.

FIGS. 43 and 44 are transmission electron micrographs showing the vicinity of the interface between the copper foil and the silicon thin film at the electrode c1, FIG. 43 is a magnification of 500,000, and FIG. It is 100,000 times. In each photograph, the lower part is the copper foil side, and the upper part is the silicon thin film side.

In Fig. 43 and Fig. 44, the lower bright part is considered to be the copper foil part, but it gradually becomes higher near the interface between the copper foil and the silicon thin film. This part (about 30 nm to 100 nm) is It is considered to be a part of a mixed layer in which copper and silicon are particularly mixed. In this mixed layer, it is considered that silicon (Si) and copper (Cu) are alloyed. In addition, as shown in FIGS. 43 and 44, a particulate portion is observed near the interface between the portion considered to be the mixed layer and the copper foil, and copper (Cu) is observed in the particulate portion. Concavities and convexities due to the diffusion of ()) into silicon (S i) are observed at the interface.

Next, in order to measure the concentration distribution of the constituent elements in the depth direction of the mixed layer, the concentrations of copper element ( ⁶³ Cu +) and hydrogen element Η ^) were measured by SIMS using 0 ₂ + as the sputtering source. did. Figure 45 shows the concentration distribution of each constituent element in the depth direction of the mixed layer, the horizontal axis shows the depth (/ m), and the vertical axis shows the atomic density (pieces Zcm ³ ). ing.

As shown in Fig. 45, in the mixed layer, the copper (Cu) concentration increases as the depth increases, that is, as it approaches the copper foil. Here, assuming that a layer containing 1% or more of the current collector material (atomic density of ^{102 Q} / cm ³ ) or more in the silicon thin film is a mixed layer, a layer having a depth of about 1.9 zm It can be seen that the mixed layer exists up to about 7 μm.

Next, for the electrode c3 in which a microcrystalline silicon thin film having a thickness of about 2 / xm was formed on the electrolytic copper foil, the concentration of each constituent element in the depth direction of the mixed layer was determined by SIMS in the same manner as described above. It was measured. Figure 46 shows this result. As shown in FIG. 4 6, in the electrode c 3, the atomic density of the already copper Te surface smell of the silicon thin film (Cu) has a 1 0 ²⁰ ZCM ³ or more, copper (C u) is a silicon thin film It can be seen that the silicon thin film has diffused to the surface and the entire silicon thin film has become a mixed layer. Battery C3 using this electrode c3 exhibited good charge / discharge cycle characteristics, indicating that the cell C3 still functions as an electrode active material even when the entire silicon thin film becomes a mixed layer.

As is clear from Figs. 45 and 46, copper in the silicon thin film The concentration of (Cu) is continuously changing. Therefore, it can be seen that in the silicon thin film, the copper element does not form an intermetallic compound with silicon but forms a solid solution with silicon.

As described above, it was confirmed that a mixed layer in which copper of the copper foil and silicon of the silicon thin film were mixed was formed at the interface between the copper foil and the silicon thin film. Due to the presence of such a mixed layer, the adhesion of the silicon thin film to the copper foil is enhanced, and even if the silicon thin film expands and contracts due to charge and discharge, the silicon thin film does not peel off from the copper foil serving as a current collector, and is excellent. It is thought that excellent charge / discharge cycle characteristics can be obtained.

(Experiment A)

In the lithium battery electrode of the present invention, since the active material thin film expands and contracts due to insertion and extraction of lithium, stress is generated in the current collector by the charge and discharge reaction. Such stress causes irreversible, that is, wrinkles due to plastic deformation in the electrode current collector. The formation of the wrinkles results in an increase in the volume of the battery and inhomogeneity of the reaction at the electrodes, resulting in a decrease in energy density. Therefore, the thickness of the electrolytic copper foil, which is the negative electrode current collector, was changed, and the relationship between the tensile strength of the negative electrode current collector and wrinkles generated on the electrodes was examined below.

(Preparation of negative electrode)

As the electrolytic copper foil, four kinds of electrolytic copper foils having a thickness of 12 // m, 18 / im, 35 / zm, and 70 µm were used. The thickness of the electrolytic copper foil as the negative electrode current collector was measured using a micrometer. The tensile strength (N mm) of these current collectors can be determined by (tensile strength per sectional area of current collector material: N / mm ² ) X (thickness of current collector: mm). The tensile strength of copper per cross-sectional area is calculated as 212.7 N / mm ² (21.7 kgf / mm ² , “Revision 2 Metal Datapuck” published by Maruzen Co., Ltd.) c

7 A silicon thin film was formed on each of the above electrolytic copper foils by RF sputtering in an Ar atmosphere. The conditions for forming the thin film were as follows: target: single-crystal silicon, high-frequency power: 350 W, Ar gas flow rate: 100 sccm, pressure inside the chamber: 0.1 Pa, substrate temperature: room temperature (no heating) . As a result of Raman spectroscopic analysis, the silicon thin film formed under the above-mentioned thin film forming conditions was found to be an amorphous silicon thin film. The thickness of each of the silicon thin films was 3.4 / xm. To measure the thickness of the silicon thin film, place the silicon substrate together with the electrolytic copper foil that forms the silicon thin film in the chamber and measure the thickness of the silicon thin film formed on the silicon substrate with a surface roughness meter. Determined by Specifically, the edge of the silicon thin film was probed with a surface roughness meter, and the height of the step at the edge of the silicon thin film was measured.

The silicon thin film was limitedly formed in a 2.5 cm × 2.5 cm area on the copper foil using a mask. The negative electrode tab was mounted on the copper foil on which the silicon thin film was not formed, and the negative electrode was completed.

(Preparation of positive electrode)

A positive electrode was prepared by using L i C o 0 ₂ powder obtained in preparation of the positive electrode of Experiment 1. Specifically, L i C o 0 ₂ powder 9 0 parts by weight, and the artificial graphite powder 5 parts by weight as the conductive material, as a binder polytetramethylene full O b ethylene of 5% by weight, including 5 parts by weight It was mixed with an aqueous solution of 1 ^ 1 monomethylpyrrolidone to make a positive electrode mixture slurry. The slurry was applied on a 2 cm × 2 cm area of an aluminum foil (18 × m) serving as a positive electrode current collector by a doctor blade method, and then dried to form a positive electrode active material layer. The amount of slurry applied was adjusted so that the positive electrode capacity was 15.5.75 mAh. A positive electrode tab was mounted on the area of the aluminum foil where the positive electrode active material layer was not applied, and the positive electrode was completed. (Preparation of electrolyte solution)

Equal volume mixed solvent of ethylene carbonate and dimethyl carbonate,

L a i PF ₆ 1 mole Z l dissolved to an electrolytic solution is prepared, using the same in the production of the following cell.

(Production of battery)

FIG. 47 is a perspective view showing the manufactured lithium secondary battery. FIG. 48 is a schematic sectional view showing the manufactured lithium secondary battery. As shown in FIG. 48, a positive electrode and a negative electrode are inserted in an outer package 40 made of an aluminum laminated film. On the negative electrode current collector 31, a silicon thin film 32 as a negative electrode active material is provided, and on the positive electrode current collector 33, a positive electrode active material layer 34 is provided. The silicon thin film 32 and the positive electrode active material layer 34 are arranged so as to face each other via a separator 35. The electrolytic solution 36 described above is injected into the exterior body 40. The end of the exterior body 40 is sealed by welding to form a sealing part 40a. The negative electrode tab 37 attached to the negative electrode current collector 31 is taken out through the sealing portion 40a. Although not shown in FIG. 48, the positive electrode tab 38 attached to the positive electrode current collector 33 is also drawn outside through the sealing portion 40a.

[Charge / discharge cycle test]

A charge / discharge cycle test was performed on the lithium secondary battery manufactured as described above. The charge and discharge conditions are as follows: charge at a charge current of 9 mA until the end-of-charge capacity reaches 9 mAh, and then discharge at a discharge current of 9 mA until the discharge end voltage reaches 2.75 V. For each battery, the charge / discharge efficiency up to the 10th cycle was determined for each battery. In addition, three samples (1C-11, 1C-12, and 1C-3) of each battery using copper foils having different thicknesses were prepared and measured. The results are shown in FIG. As shown in Fig. 49, there is no particular effect on the charge-discharge cycle characteristics due to the difference in the thickness of the copper foil, and good charge-discharge cycle characteristics were obtained using any thickness of copper foil. I have.

Further, after 10 cycles, the negative electrode was taken out of each battery, and the state of the negative electrode was observed. FIGS. 50 and 51 show the state of the negative electrode surface on which the silicon thin film is formed, and FIGS. 52 and 53 show the state of the negative electrode back surface on which the silicon thin film is not formed. In FIGS. 50 to 53, “12”, “18”, “35”, and “70” indicate the thickness of the copper foil, respectively.

As is clear from FIG. 52 and FIG. 53, after the charge / discharge reaction, many wrinkles are observed in the electrode using the copper foil having a thickness of 12 μm. On the other hand, wrinkles were slightly observed in the electrode using the copper foil with a thickness of 18 μm, and almost wrinkles were observed in the electrode using the copper foil with a thickness of 35 μm and 70 μtn. Not. Table 13 summarizes these results. The evaluation in Table 13 is based on the following criteria.

X: Many wrinkles are observed.

〇: Some wrinkles are observed.

A: Almost no wrinkles are observed. Table 13

Current collector thickness (| Β) 1 2 1 8 35 70 Current collector tension 2. 552 3.828 7.4 3 14. 886

(N / mm)

Thickness of active material thin film 0.28 0.1 9 0.1 0 0.0 9 Z current collector thickness

Evaluation X ◎ ◎ ◎ As is clear from Table 13, when the current collector has a tensile strength of 3.82 NZmm or more, the wrinkles generated on the electrode rapidly decrease, and when the tensile strength of 7.44 N / mm or more, the wrinkles are formed. It turns out that it is hardly recognized. Also, when the ratio of the thickness of the silicon thin film to the thickness of the current collector is 0.19 or less, the wrinkles generated on the electrode are sharply reduced, and when it is 0.10 or less, wrinkles are hardly recognized. . This is thought to be because when the current collector has a certain tensile strength or more, the stress due to expansion and contraction of the active material thin film is relaxed by elastic deformation of the current collector.

(Experiment

Next, the thickness of the silicon thin film formed on the electrodeposited copper foil, which is the negative electrode current collector, was changed to determine the tensile strength of the negative electrode current collector per 1 m thickness of the silicon thin film and the wrinkles generated on the electrodes. The relationship was discussed.

(Preparation of negative electrode)

As the negative electrode current collector, an electrolytic copper foil having a thickness of 18 μm was used. The thickness of the electrolytic copper foil was measured using a micrometer as in Experiment A. In addition, the tensile strength (NZmm) of the current collector was determined in the same manner as in Experiment A. An amorphous silicon thin film was formed on the above electrolytic copper foil under the same thin film forming conditions as in Experiment A. Three types of silicon thin films having a thickness of 0.9 / zm, 1.8 / zm, and 3.6 μm were formed. The thickness of the silicon thin film was determined in the same manner as in Experiment A.

As in Experiment A, the negative electrode tab was mounted on the copper foil to complete the negative electrode.

(Production of battery)

A positive electrode and an electrolyte were prepared in the same manner as in Experiment A, and a lithium secondary battery was formed in the same manner as in Experiment A.

[Charge / discharge cycle test] A charge / discharge cycle test was performed under the same conditions as in Experiment A for each of the lithium secondary batteries using the negative electrodes having different thicknesses of silicon thin films manufactured as described above. The charge / discharge efficiency of each battery up to the 30th cycle was determined. For each battery using negative electrodes with different silicon thin film thickness, three samples were prepared and measured. The results are shown in FIG. “0.9 m”, “1.8 / xm”, and “3.6 m” in FIG. 54 all indicate the thickness of the silicon thin film, and the charge / discharge efficiency in each cycle was 3 samples. Is the average value.

As is evident from Fig. 54, there is no particular effect on the charge-discharge cycle characteristics due to the difference in the thickness of the silicon thin film, and good charge-discharge cycle characteristics can be obtained using any thickness of silicon thin film. ing.

Further, after 10 cycles of charging and discharging, that is, after 40 cycles, the electrode was taken out of each battery and the state of the negative electrode was observed. FIG. 55 shows the state of the back surface of the negative electrode, that is, the state of the surface on which the silicon thin film is not formed. In FIG. 55, “0.9”, “1.8”, and “3.6” indicate the thickness of the silicon thin film, respectively.

As is clear from Fig. 55, after the charge / discharge reaction, a large number of wrinkles are observed on the electrode formed with the 3.6 µm-thick silicon thin film. On the other hand, some wrinkles were observed in the electrode formed with a 1.8 / Zm-thick silicon thin film, and almost no wrinkle was observed in the electrode formed with a 0.9-μm-thick silicon thin film. I have not been observed. Table 14 summarizes these results. The evaluations in Table 14 are performed based on the same criteria as the evaluations in Table 13. Table 14

In addition to the results shown in Table 13 of Experiment A, Table 15 shows the results sorted in the order of the tensile strength of the current collector per silicon thin film l // m. Table 15

As is evident from Table 15, when the tensile strength of the current collector of the silicon thin film (1) exceeds 1.1 NZmm or more, wrinkles generated on the electrode rapidly occur. It turns out that it decreases. Also, from the results shown in Table 15, when the tensile strength of the negative electrode current collector per 1 μm of the silicon thin film thickness is 2.18 N / mm or more, wrinkles that occur further decrease and almost wrinkles are observed. You can see that it is no longer possible. Further, when comparing “35” shown in FIG. 53 with “0.9” shown in FIG. 55 in more detail, both of the evaluations are “◎”, but “0.9” shown in FIG. Is less wrinkled. From this, it is understood that when the tensile strength of the negative electrode current collector per 1 μm of the thickness of the silicon thin film is 4.25 NZm or more, wrinkles that occur are further reduced. Similarly to the above, from the viewpoint of the ratio of the thickness of the silicon thin film to the thickness of the current collector, when this ratio is 0.19 or less, the wrinkles that occur rapidly decrease, and the ratio is 0.098 or less. It can be seen that the wrinkles are further reduced as the value becomes, and the wrinkles are further reduced as the value becomes less than 0.05.

From the above, when the tensile strength of the negative electrode current collector per 1 μm thickness of the active material thin film exceeds a certain value, the stress due to expansion and contraction of the active material thin film is almost alleviated by the elastic deformation of the current collector. Therefore, it is thought that wrinkles are less likely to occur. Similarly, when the ratio of the thickness of the active material thin film to the thickness of the negative electrode current collector falls below a certain value, the stress due to the expansion and contraction of the active material thin film is almost alleviated by the elastic deformation of the current collector. It is thought that the occurrence of the occurrence is reduced.

Hereinafter, an example according to the fifth aspect of the present invention will be described.

(Example A)

(Preparation of negative electrode)

A negative electrode 20 as shown in FIGS. 56 and 58 was produced. FIG. 56 is a plan view, and FIG. 58 is a side view. As shown in FIG. 58, a microcrystalline silicon thin film 22 a is formed on the negative surface 21 a of the electrolytic copper foil 21, and a microcrystalline silicon thin film 22 is formed on the other surface 21 b. Formed b. The electrolytic copper foil 21 is a copper foil in which a rolled copper foil is immersed in an electrolytic solution, and copper is deposited on both surfaces thereof by an electrolytic method to roughen both surfaces. The size of the electrolytic copper foil 21 is 20 mm × 30 mm, and the size of the region where the microcrystalline silicon thin films 22 a and 22 b are formed is 20 mm × 20 mm. The thickness of the electrolytic copper foil 21 is 18 μm, and the thickness of each of the microcrystalline silicon thin films 22a and 22b is about 5 μm. The surface roughness Ra of the surfaces 21 a and 21 b of the electrolytic copper foil 21 is 0.20 / zm, and the average distance S between the local peaks is 10 μm.

The microcrystalline silicon thin films 22a and 22b were formed by a plasma CVD method. Using silane (S i H ₄₎ gas as a raw material gas, using a hydrogen gas as a carrier gas. Thin film formation condition, S i H ₄ flow rate: 1 0 sccm, H ₂ gas flow rate: 200 sccm, substrate temperature: 1 80 ° C, the reaction pressure 4 0 P a, high frequency power: was 5 5 5W.

As shown in FIGS. 56 and 58, a nickel tab 23 is attached on the surface 21 a of the electrolytic copper foil 21 on which the microcrystalline silicon thin films 22 a and 22 b are not formed, and the negative electrode is attached. completed.

(Preparation of positive electrode)

A positive electrode 25 as shown in FIG. 57 was produced. As shown in FIG. 5 7, aluminum as a current collector - over © arm foil 26, dried after application of the L i C o 0 ₂ mixture slurry, the cathode active material layer 27 a and 27 b Formed. As the aluminum foil 26, a foil having a size of 20 mm × 60 mm was used. The formation areas of the positive electrode active material layers 27a and 27b were each set to 20 mm × 20 mm. The positive electrode mixture slurry was prepared as follows.

As a starting material, using L i ₂ C0 ₃ and C o C0 _3, L i: the atomic ratio of C o is 1: 1 so as to be枰量mixed in a mortar, which diameter 1 7 mm After pressing with a mold and press forming, 24 hours at 800 ° C in air And the firing time to obtain a sintered body of L i C o 0 _2. This was ground in a mortar until it reached an average particle size of 20 // m.

The obtained L i C o 0 ₂ powder 9 0 parts by weight, and the artificial graphite powder 5 parts by weight as the conductive material, a polytetramethylene full O b ethylene as a binder of 5 wt% comprising 5 parts by weight 1 ^ This was mixed with an aqueous solution of monomethylpyrrolidone to prepare a positive electrode mixture slurry.

An aluminum tab 28 was attached to the back of the aluminum foil 26 as shown in FIG. 57 to complete the positive electrode.

(Preparation of electrolyte solution)

In equal volume mixed solvent of ethylene carbonate and Jechiruka one Boneto, the L i PF _e was dissolved 1 mole Z l to prepare an electrolytic solution, using the same in the production of the following cell.

(Production of battery)

FIG. 59 is a plan view showing the manufactured lithium secondary battery. FIG. 60 is a sectional view taken along line AA in FIG. As shown in FIG. 60, the battery is assembled by disposing the negative electrode 20 and the positive electrode 25 in an envelope-shaped container 30 made of an aluminum laminate film. The positive electrode 25 is bent such that the positive electrode active material layers 27a and 27b are inside, and the negative electrode 20 is inserted inside the positive electrode 25. The microcrystalline silicon thin film 22a of the negative electrode 20 is opposed to the positive electrode active material layer 27a via a separator 29a, and the microcrystalline silicon thin film 22b is connected to the positive electrode via a separator 29b. It faces the active material layer 27b. In such a state, after the positive electrode 25 and the negative electrode 20 are introduced into the container 30, a vacuum heating treatment is performed at 105 for 2 hours, and then the above-mentioned electrolytic solution is transferred to the container 30. After the injection, the container was sealed with a sealing portion 31 shown in FIG. 59 to produce a lithium secondary battery.

(Comparative Example a) (Preparation of negative electrode)

A negative electrode was produced in the same manner as in the production of the negative electrode of Example A, except that the microcrystalline silicon thin film 22a was formed only on one surface 21a of the electrolytic copper foil 21.

(Preparation of positive electrode)

A positive electrode was prepared in the same manner as in the preparation of the positive electrode of Example A, except that only the positive electrode active material layer 2a was formed as a positive electrode active material layer on the aluminum foil 26 shown in FIG.

(Production of battery)

In the same manner as in Example A, the positive electrode 25 was bent into two with the positive electrode active material layer 27a inside, and the negative electrode 20 was inserted between them. Between the microcrystalline silicon thin film 22 a and the positive electrode active material layer 27 a via a separator 29 a, the surface of the electrolytic copper foil 21 where the microcrystalline silicon thin film 2 2 b is not provided, A separator 29b is interposed between the surface of the aluminum foil 26 on which the positive electrode active material layer 27b is not provided, and the others are the same as in Example A above. Was prepared.

(Charge / discharge cycle test)

The lithium secondary batteries of Example A and Comparative Example a were subjected to a charge / discharge vital test. The charge and discharge conditions were as follows: at 25 ° C, the battery was charged to 4.2 V at a charge / discharge current density of 0.2 mAZcm ² and then discharged to 2.75 V, which was defined as one cycle of charge and discharge. The capacity retention of the 15th cycle was measured for each battery. The discharge capacity in the first cycle was 25 mAh for the battery of Example A, and 12 mAh for the battery of Comparative Example a.

The results are shown in Table 16.

8 Table 16

As is clear from the results shown in Table 16, the battery of Example A shows a higher capacity retention ratio than the battery of Comparative Example a. This is because by forming microcrystalline silicon thin films on both sides of the negative electrode current collector, the strain caused by the charge / discharge reaction of the negative electrode current collector is reduced, and peeling of the active material thin film from the negative electrode current collector is suppressed. It seems to have been done.

(Example B)

As a lithium secondary battery according to the present invention, a lithium secondary battery in which a positive electrode and a negative electrode were combined to form a stack structure as shown in FIG. 61 was produced.

(Preparation of negative electrode)

In the same manner as in Example A, a microcrystalline silicon thin film having a thickness of about 5 / zm was formed on both surfaces of the electrolytic copper foil having both surfaces roughened used in Example A, and used as a negative electrode.

(Preparation of positive electrode)

Including L i C o 0 ₂ powder 8 5 parts by weight of the obtained analogously to Example A, artificial graphite powder 1 0 parts by weight as the conductive material, a polytetramethylene full O b ethylene 5 parts by weight of a binder 5 weight. /. An N-methylpyrrolidone aqueous solution was prepared, and this was used as a positive electrode mixture slurry. This was applied on both sides of a 20-μm-thick aluminum foil and then dried to obtain a positive electrode having a positive electrode active material layer formed on both sides.

(Production of battery) The negative electrode 41 obtained by forming a microcrystalline silicon thin film on both surfaces and the positive electrode 42 having a positive electrode active material layer formed on both surfaces, as shown in FIG. 3 were alternately stacked to form a stacked electrode structure. A negative electrode tab 41 a is provided at an upper end of the negative electrode 41, and a positive electrode tab 42 a is provided at an upper end of the positive electrode 42. Eight negative and positive electrodes 41 and 42 were used, and eight combinations of positive and negative electrodes were stacked.

After inserting the above-mentioned stacked electrode group into an exterior body 44 made of an aluminum laminate as shown in FIG. 62, an electrolytic solution was injected into the exterior body 44. And sealed. The negative electrode tab 41 a and the positive electrode tab 42 a were arranged so as to protrude out of the exterior body 44, and were sealed.

As the electrolytic solution is injected into the outer package 4 in 4, ethylene carbonate Natick bets and Jefferies the chill carbonate 4: 6 mixed solvent used was a L i PF ₆ dissolved 1 mol Bruno liter.

(Comparative Example b)

A negative electrode using natural graphite as an active material was produced. Specifically, to prepare a 5 wt ^_0/0 N- Mechirupirori Don aqueous solution containing Porite trough Ruo ii ethylene 5 parts by weight of a natural black lead powder 9 5 parts by weight binder, and Fukyokugozaisu Larry did. This was applied on both sides of a rolled copper foil having a thickness of 18 m, and then dried to obtain a negative electrode.

A lithium secondary battery shown in FIGS. 61 and 62 was produced in the same manner as in Example B except that the negative electrode obtained as described above was used.

Table 17 shows the discharge capacity, average discharge voltage, energy density per volume, and energy density per weight of the lithium secondary batteries of Example B and Comparative Example b. The initial discharge capacity of the positive electrode active material used in Example B was 15 OmAhZg, and the initial discharge capacity of the negative electrode active material used in Example B was 3200. mAhZg, and the initial discharge capacity of the negative electrode active material used in Comparative Example b was set at 370 mAh / g.

7

As shown in Table 17, the energy density per unit volume of Example B using the electrode for a lithium secondary battery according to the present invention as the negative electrode was lower than that of Comparative Example b using the conventional negative electrode of graphite. It can be seen that the energy density per unit weight is increased.

(Example C)

A coin-type lithium secondary battery shown in FIG. 63 was produced. The negative electrode is formed by forming microcrystalline silicon thin films 52a and 52b on both surfaces of the negative electrode current collector 51, respectively. As the negative electrode current collector 51, the electrolytic copper foil having the roughened surfaces on both sides used in Example B was used. Also, the microcrystalline silicon thin films 52 a and 52 b are formed in the same manner as in Example B.

The positive electrode is configured by providing positive electrode active material layers 55 a and 55 b inside a positive electrode current collector 54 bent into a U-shape. As the positive electrode current collector 54, the same aluminum foil as the aluminum foil used in Example B was used. Further, the positive electrode active material layers 55a and 55b are formed in the same manner as the positive electrode active material layer in Example B. As shown in FIG. 63, the negative electrode is inserted inside the positive electrode current collector 54 bent into a U-shape. Separators 56 a and 56 b are arranged between the silicon thin films 52 a and 52 b as the negative electrode active material layers of the negative electrode and the positive electrode active material layers 55 a and 55 b of the positive electrode, respectively. ing.

Negative electrode current collector 51 is connected to negative electrode tab 53, and negative electrode tab 53 is connected to negative electrode can 58. An insulating sheet 57 is provided between the positive electrode current collector 54 on the negative electrode can 58 side and the negative electrode can 58, and the negative electrode can 58 and the positive electrode current collector are provided by the insulating sheet 57. The body 54 is electrically insulated. The positive electrode current collector 54 is provided so as to be in contact with the positive electrode can 59, whereby the positive electrode current collector 54 and the positive electrode can 59 are electrically connected. An insulating packing 60 is provided between the negative electrode can 58 and the positive electrode can 59, thereby providing electrical insulation and sealing the inside of the battery can. The same electrolytic solution as in Example B was sealed in the battery can.

(Comparative Example c)

A coin-type lithium secondary battery was produced in the same manner as in Example C, except that a negative electrode having a negative electrode active material layer using the same natural graphite as the active material as in Comparative Example b was used as the negative electrode.

Table 18 shows the discharge capacity, average discharge voltage, energy density per volume, and energy density per weight of the coin-type lithium secondary batteries of Example C and Comparative Example c.

8

As shown in Table 18, the lithium secondary battery of Example C in which the electrode for a lithium secondary battery according to the present invention was used for the negative electrode had a higher energy per unit volume and weight than the lithium secondary battery of Comparative Example c. Excellent in density.

(Example D)

A laminate type lithium secondary battery shown in FIG. 64 was produced. In FIG. 64, the negative electrode 61 is formed by forming a microcrystalline silicon thin film having a thickness of 5 // m on both sides of the electrolytic copper foil, similarly to the negative electrode shown in FIG. Similarly to the positive electrode shown in FIG. 63, the positive electrode 62 is configured by providing a pair of positive electrode active material layers inside an aluminum foil serving as a positive electrode current collector bent in a U-shape. The negative electrode 61 is inserted inside the U-shaped positive electrode 62 to form a set of batteries 65. A negative electrode tab 63 is taken out of the negative electrode 61, and a positive electrode tab 64 is taken out of the positive electrode 62. This set of batteries 65 is stacked in four stages and inserted into an exterior body 66 made of aluminum laminate. Although FIG. 64 shows a state in which one set of batteries 65 is stacked in three layers, in practice, four cells are stacked as described above. The same electrolytic solution as in Example B is injected into the exterior body 66.

Fig. 65 is a plan view of the laminated lithium secondary battery shown in Fig. 64. FIG. As shown in FIG. 65, the outer body 66 is welded on three sides to form a welded portion 67.

You. The negative electrode tab 63 and the positive electrode tab 64 are drawn out of the exterior body 66.

(Comparative Example d)

As in Comparative Example b, a laminated lithium secondary battery was produced in the same manner as in Example D except that a negative electrode using graphite was used as the negative electrode.

Table 19 shows the discharge capacity, average discharge voltage, energy density per volume, and energy density per weight of the lithium secondary batteries of Example D and Comparative Example d. Table 19

As is evident from Table 19, the lithium secondary battery of Example D using the electrode for a lithium secondary battery according to the present invention as the negative electrode has a smaller weight per unit volume and weight than the lithium secondary battery of Comparative Example d. Excellent in energy density.

(Example E)

A cylindrical lithium secondary battery shown in FIG. 66 was produced. A separator 73 is sandwiched between the positive electrode 71 and the negative electrode 72, and another separator is provided outside the positive electrode 71. A separator 73 is arranged, and in this state, it is spirally wound and inserted into the battery can. As the positive electrode 71 and the negative electrode 72, similarly to Example B, those having a positive electrode active material layer formed on both sides of an aluminum foil and those having microcrystalline silicon thin films formed on both sides of an electrolytic copper foil were used. . The same electrolytic solution as in Example B was injected into the battery can.

The negative electrode 72 is electrically connected to the negative electrode can 74 by a lead, and the positive electrode 71 is electrically connected to the positive terminal 75 by a lead.

(Comparative Example e)

A cylindrical lithium secondary battery was produced in the same manner as in Example E, except that the negative electrode used was the same as Comparative Example b using graphite as an active material.

Table 20 shows the discharge capacity, average discharge voltage, energy density per volume, and energy density per weight of the lithium secondary batteries of Example E and Comparative Example e. Table 20

As is clear from Table 20, the lithium secondary battery of Example E using the electrode for a lithium secondary battery according to the present invention as a negative electrode has a smaller weight per unit volume and weight than the lithium secondary battery of Comparative Example e. Excellent in energy density. (Example F)

A prismatic lithium secondary battery shown in FIG. 67 was produced. As in the case of the cylindrical lithium secondary battery shown in FIG. 66, separators 73 are arranged between the positive electrode 71 and the negative electrode 72 and outside the positive electrode 71, respectively, and after being wound in a spiral shape. It is flattened and stored in the negative electrode can 74. As in the case of Example B, a negative electrode 72 having a microcrystalline silicon thin film formed on both surfaces of an electrolytic copper foil was used. The negative electrode 72 is electrically connected to the negative electrode can 74 by a lead, and the positive electrode 71 is electrically connected to the positive electrode terminal 75 by a lead. The same electrolytic solution as in Example B was injected into the battery can.

(Comparative example f)

A prismatic lithium secondary battery was fabricated in the same manner as in Example F, except that the negative electrode used was the same as Comparative Example b using graphite as an active material.

Table 21 shows the discharge capacity, average discharge voltage, energy density per volume, and energy density per weight of Example F and Comparative Example f. Table 2

As is clear from Table 21, the lithium secondary battery of Example F using the electrode for a lithium secondary battery according to the present invention as a negative electrode has a smaller weight per unit volume and weight than the lithium secondary battery of Comparative Example f. In energy density Are better. Industrial applicability

According to the first aspect and and second aspects of the present invention, according to the third aspect of the _c the present invention which can charge and discharge capacity is high and the excellent lithium secondary battery charge-discharge cycle characteristics For example, an electrode for a lithium secondary battery having a high charge / discharge capacity and excellent charge / discharge cycle characteristics, and an electrode for a lithium secondary battery capable of suppressing wrinkling of the electrode due to charge / discharge. Can be

According to the fourth aspect of the present invention, after forming an intermediate layer made of a material that can be alloyed with the active material thin film on the current collector, the active material thin film is formed on the intermediate layer. It is possible to prevent the active material thin film from being detached from the current collector, improve the current collection characteristics, and obtain a good charge / discharge cycle.

According to the fifth aspect of the present invention, in an electrode for a lithium secondary battery, distortion of a current collector caused by a charge / discharge reaction can be reduced, and further, the charge / discharge cycle characteristics of a lithium secondary battery can be improved. Can be.

Claims

The scope of the claims

1. An electrode for a lithium battery, comprising an active material for inserting and extracting lithium, wherein amorphous silicon is used as the active material.

2. An electrode for a lithium battery, comprising an active material that absorbs and releases lithium, wherein microcrystalline silicon is used as the active material.

3. The electrode for a lithium battery according to claim 1, wherein the amorphous silicon or the microcrystalline silicon contains hydrogen.

4. The size of a crystal region in the microcrystalline silicon is 0.5 nm or more as a crystal grain size calculated from an X-ray diffraction pattern and a Scherrer equation. Item 4. An electrode for a lithium battery according to item 2 or 3.

5. The peak intensity ratio near 480 cm- ¹ to the peak intensity near 520 cm- ¹ in the Raman spectroscopic analysis of the microcrystalline silicon (Z5020 cm- ¹ near 480 cm- ¹⁾ The electrode for a lithium battery according to any one of claims 2 to 4, wherein (near) is 0.05 or more.

6. An electrode for a lithium battery including an active material that absorbs and releases lithium, wherein amorphous silicon containing hydrogen is used as the active material.

7. An electrode for a lithium battery including an active material that absorbs and releases lithium, wherein microcrystalline silicon containing hydrogen is used as the active material.

8. The electrode for a lithium battery according to any one of claims 3, 6, or 7, wherein the hydrogen concentration is 0.001 atomic% or more.

9

9. The electrode for a lithium battery according to any one of claims 1 to 8, wherein the amorphous or microcrystalline silicon is a silicon thin film.

10. The lithium battery electrode according to claim 9, wherein the silicon thin film is a silicon thin film deposited on a substrate by supplying a silicon material from a gas phase.

11. The lithium battery electrode according to claim 10, wherein hydrogen gas is introduced together with the silicon material.

1 2. A lithium battery electrode including an active material that absorbs and releases lithium, wherein a silicon thin film formed by supplying hydrogen gas together with a silicon material from a gas phase is used as the active material. Electrode for lithium batteries.

13. The lithium battery electrode according to any one of claims 10 to 12, wherein the silicon material is a raw material gas containing silicon atoms or a raw material powder containing silicon atoms.

14. The electrode for a lithium battery according to any one of claims 10 to 13, wherein the method of forming the silicon thin film is a CVD method, a sputtering method, a thermal spraying method, or a vacuum evaporation method.

1 5. An electrode for a lithium battery including an active material that absorbs and releases lithium, wherein a silicon thin film made of amorphous silicon containing hydrogen is used as the active material.

1 6. An electrode for a lithium battery including an active material that absorbs and releases lithium, wherein a silicon thin film made of microcrystalline silicon containing hydrogen is used as the active material.

17. The electrode for a lithium battery according to any one of claims 9 to 16, wherein the silicon thin film is provided on a current collector.

1 8. The silicon thin film is provided on the current collector through an intermediate layer. An electrode for a lithium battery according to claim 17.

19. The lithium battery electrode according to claim 17 or 18, wherein the current collector is at least one selected from copper, nickel, stainless steel, molybdenum, tungsten, and tantalum.

20. It is required that lithium is added to the amorphous silicon or microcrystalline silicon according to any one of claims 1 to 8 or the silicon thin film according to any one of claims 9 to 19 in advance. Features for lithium batteries

21. The collector according to any one of claims 10 to 14 and 17 to 20, wherein the surface roughness Ra of the current collector or the substrate is 0.01 to lm. Electrode for lithium batteries.

22. The electrode for a lithium battery according to claim 21, wherein the current collector is a copper foil.

23. The lithium battery electrode according to claim 22, wherein the copper foil is an electrolytic copper foil.

24. The method according to claim 2, wherein a surface roughness Ra of the current collector or the substrate has a relationship of Ra≤t with respect to a thickness t of the active material. Item 2. An electrode for a lithium battery according to item 1.

25. The method according to any one of claims 21 to 24, wherein the surface roughness Ra of the current collector or the substrate and the average distance S between local peaks have a relationship of 100 RaS. Or the electrode for a lithium battery according to item 1.

26. The electrode for a lithium battery according to any one of claims 17 to 25,

An electrode for a lithium battery, wherein the silicon thin film is separated into columns by cuts formed in the thickness direction thereof, and the bottom of the columnar portion is in close contact with the current collector.

27. The electrode for a lithium battery according to claim 26, wherein at least 12 or more parts of the thickness in the thickness direction of the silicon thin film are separated into columns by the cuts.

28. The electrode for a lithium battery according to claim 26, wherein the cut is formed by charge and discharge after the first time.

29. Before charging / discharging, irregularities are formed on the surface of the silicon thin film, and the first charge / discharge forms a discontinuity in the thin film with a valley of the irregularity on the surface as an end. 29. The electrode for a lithium battery according to claim 28, wherein the thin film is separated into columns.

30. The electrode for a lithium battery according to claim 29, wherein the irregularities on the surface of the silicon thin film correspond to irregularities on the surface of the current collector serving as an underlayer.

31. The lithium battery electrode according to claim 30, wherein the projections of the unevenness on the surface of the current collector have a cone shape.

32. The electrode for a lithium battery according to any one of claims 26 to 31, wherein an upper portion of the columnar portion has a rounded shape.

33. The electrode for a lithium battery according to claim 26, 27, or 32, wherein the cut is formed in advance before charging and discharging.

34. The lithium battery electrode according to claim 26, wherein the cut is formed along a low-density region extending in a thickness direction of the silicon thin film. An electrode for a lithium battery, comprising:

35. The electrode for a lithium battery according to claim 34, wherein the low-density region extends upward from a valley of unevenness on the surface of the current collector.

36. The electrode c for a lithium battery according to any one of claims 17 to 35, wherein the component of the current collector is diffused in the silicon thin film.

37. An electrode for a lithium battery in which a thin film made of an active material that absorbs and releases lithium is provided on a current collector.

An electrode for a lithium battery, wherein the thin film is separated into columns by cuts formed in the thickness direction thereof, and a bottom of the columnar portion is in close contact with the current collector.

38. The lithium battery electrode according to claim 37, wherein at least a half or more of the thickness in the thickness direction of the thin film is separated into columns by the cuts.

39. The electrode for a lithium battery according to claim 37, wherein the cut is formed by charge and discharge after the first time.

40. Unevenness is formed on the surface of the thin film before charging and discharging, and a notch is formed in the thin film by the first and subsequent charging and discharging, with a valley of the unevenness on the surface being an end. 30. The electrode for a lithium battery according to claim 39, wherein the thin film is separated into a column shape by the method.

41. The electrode for a lithium battery according to claim 40, wherein the unevenness on the surface of the thin film corresponds to the unevenness on the surface of the current collector serving as an underlayer.

42. The electrode for a lithium battery according to claim 41, wherein the projections of the unevenness on the surface of the current collector have a cone shape.

43. The electrode for a lithium battery according to any one of claims 37 to 42, wherein an upper portion of the columnar portion has a rounded shape.

44. The electrode for a lithium battery according to claim 37, wherein the cut is formed before charging and discharging.

4 5. The Periodic Table 元素, Π Ι, and IVB and VB elements of the periodic table in which the thin film forms a compound or solid solution with lithium, and the transition of the periodic table in the fourth, fifth, and sixth periods 37. A material comprising at least one material selected from oxides and sulfides of metal elements. 47. The electrode for a lithium battery according to any one of items 44 to 44.

46. The element according to claim 4, wherein the element is at least one selected from carbon, silicon, germanium, tin, lead, aluminum, indium, zinc, cadmium, bismuth, and mercury. 5. The electrode for a lithium battery according to 5.

47. The electrode for a lithium battery according to claim 45, wherein the element is silicon.

48. The electrode for a lithium battery according to claim 45, wherein the element is germanium.

49. The electrode for a lithium battery according to any one of claims 37 to 48, wherein the thin film is an amorphous thin film.

50. The electrode for a lithium battery according to any one of claims 37 to 48, wherein the thin film is an amorphous thin film.

51. The electrode for a lithium battery according to any one of claims 37 to 44, wherein the thin film is an amorphous silicon thin film.

52. The electrode for a lithium battery according to any one of claims 37 to 44, wherein the thin film is a microcrystalline silicon thin film.

53. The electrode for a lithium battery according to any one of claims 37 to 44, wherein the thin film is an amorphous silicon thin film.

54. The electrode for a lithium battery according to any one of claims 37 to 44, wherein the thin film is an amorphous germanium thin film.

55. The electrode for a lithium battery according to any one of claims 37 to 44, wherein the thin film is an amorphous germanium thin film.

56. The current collector according to any one of claims 37 to 55, wherein the current collector is at least one selected from copper, nickel, stainless steel, molybdenum, tantalum, and tantalum. Electrode for lithium battery.

57. The electrode for a lithium battery according to any one of claims 37 to 56, wherein the current collector has a surface roughness Ra of 0.01 to 1 zm.

58. The electrode for a lithium battery according to any one of claims 37 to 57, wherein the current collector is a copper foil.

59. The electrode for a lithium battery according to claim 58, wherein the copper foil is an electrolytic copper foil.

60. The lithium battery electrode according to any one of claims 37 to 59, wherein the cut is formed along a low-density region extending in a thickness direction of the thin film. Characteristic electrode for lithium battery.

61. The lithium battery electrode according to claim 60, wherein the low-density region extends upward from an uneven valley on the surface of the current collector.

62. The electrode for a lithium battery according to any one of claims 37 to 61, wherein a component of the current collector is diffused in the thin film.

63. A lithium battery comprising: a negative electrode comprising the electrode according to any one of claims 1 to 62; a positive electrode; and an electrolyte.

64. A lithium secondary battery comprising a negative electrode comprising the electrode according to any one of claims 1 to 62; a positive electrode; and a non-aqueous electrolyte.

65. A negative electrode provided with a pair of negative electrode active material layers facing each other inside a current collector bent in a U-shape,

A positive electrode active material layer provided on both surfaces of the current collector, a positive electrode inserted inside the U-shaped negative electrode,

A separator disposed between the positive electrode active material layer of the positive electrode and the negative electrode active material layer of the negative electrode,

A lithium secondary battery, wherein the negative electrode is the electrode according to any one of claims 1 to 62.

66. The lithium secondary battery according to claim 64 or 65, wherein the positive electrode contains an oxide capable of occluding and releasing lithium as an active material.

67. The lithium secondary battery according to claim 64, wherein the positive electrode contains a lithium-containing oxide as an active material.

68. An electrode material layer composed of a thin film, and a current collector closely adhered to the electrode material layer,

An electrode for a secondary battery, wherein a low-density region is formed in the thin film so as to extend in a mesh direction in a plane direction and extends in a thickness direction toward the current collector.

69. The electrode for a secondary battery according to claim 68, wherein a component of the current collector is diffused in the thin film.

70. The secondary battery electrode according to claim 68, wherein the thin film is a thin film formed on the current collector by a thin film forming method.

71. The electrode for a secondary battery according to claim 70, wherein the thin film forming method is a CVD method, a sputtering method, a vapor deposition method, a thermal spraying method, or a plating method.

72. The current collector according to any one of claims 68 to 71, wherein the current collector has irregularities on its surface, and the low-density region is formed based on a valley of the irregularities. Or the electrode for a secondary battery according to item 1.

73. The electrode for a secondary battery according to claim 72, wherein the projections of the unevenness on the surface of the current collector have a cone shape.

74. The secondary battery electrode according to any one of claims 68 to 73, wherein irregularities corresponding to irregularities on the surface of the current collector are formed on the surface of the thin film.

75. Due to expansion and contraction of the thin film, a cut is formed in the thickness direction along the low-density region, whereby the thin film is separated into columns. The electrode for a secondary battery according to any one of claims 68 to 74, characterized in that:

76. The secondary battery electrode according to claim 75, wherein the expansion and contraction of the thin film is given by charge and discharge.

77. The electrode for a secondary battery according to any one of claims 68 to 76, wherein the thin film is a silicon thin film.

78. The electrode for a secondary battery according to claim 77, wherein the silicon thin film is an amorphous silicon thin film or a microcrystalline silicon thin film.

79. The electrode for a secondary battery according to any one of claims 68 to 76, wherein the thin film is a germanium thin film.

80. The electrode for a secondary battery according to claim 79, wherein the germanium thin film is an amorphous germanium thin film or a microcrystalline germanium thin film.

81. The electrode for a secondary battery according to any one of claims 68 to 80, wherein the current collector is a copper foil.

82. The electrode for a secondary battery according to claim 81, wherein the copper foil is an electrolytic copper foil.

83. A secondary battery using the electrode according to any one of claims 68 to 82.

84. The secondary battery according to claim 83, wherein the electrode is a positive electrode and ^/ or a negative electrode of the secondary battery.

85. The secondary battery according to claim 83, wherein the secondary battery is a non-aqueous electrolyte secondary battery.

86. The secondary battery according to claim 85, wherein the nonaqueous electrolyte secondary battery is a lithium secondary battery.

8 7. Lithium containing an active material consisting of a material that absorbs and releases lithium An electrode for a battery, wherein the active material is substantially composed of a crystalline region and an amorphous region made of the same or different material as the crystalline region.

88. The electrode for a lithium battery according to claim 87, wherein the amorphous region is arranged around the crystalline region.

89. The electrode for a lithium battery according to claim 87 or 88, wherein the crystal region is composed of minute crystal grains.

90. The periodic table, in which the crystalline region and Z or the amorphous region form a compound or a solid solution with lithium, Group 、, Ι Π, IVB and VB group elements, and periodic table The semiconductor device according to any one of claims 87 to 89, characterized in that it is composed of at least one material selected from oxides and sulfides of transition metal elements having four, five and six periods. The electrode for a lithium battery as described in the above.

91. The element according to claim 90, wherein the element is at least one selected from carbon, silicon, germanium, tin, lead, aluminum, indium, zinc, cadmium, bismuth, and mercury. An electrode for a lithium battery according to claim 1.

92. The electrode for a lithium battery according to claim 90, wherein the element is silicon.

93. The electrode for a lithium battery according to any one of claims 87 to 92, wherein the amorphous region contains hydrogen.

94. The electrode for a lithium battery according to any one of claims 87 to 93, wherein the active material is a thin film formed on a substrate.

95. The electrode for a lithium battery according to claim 94, wherein the thin film is formed on a substrate via an intermediate layer.

96. The claim 94, wherein the substrate is a current collector.

0 0 6. The electrode for a lithium battery according to 5.

97. The lithium battery electrode according to claim 96, wherein the current collector is at least one selected from copper, nickel, stainless steel, molybdenum, tungsten, tantalum, and carbon.

98. The lithium battery according to any one of claims 94 to 97, wherein the surface roughness Ra of the current collector or the substrate is 0.01 to 1 μπι. electrode.

99. The electrode for a lithium battery according to claim 98, wherein the current collector is a copper foil.

100. The electrode for a lithium battery according to claim 99, wherein the copper foil is an electrolytic copper foil.

10 1. The method according to any one of claims 98 to 100, wherein the surface roughness Ra of the current collector or the substrate has a relationship of R at with the thickness t of the active material. Item 8. An electrode for a lithium battery according to item 1.

10. 98. The method according to claim 98, wherein the surface roughness Ra of the current collector or the substrate and the average distance S between the local peaks have a relationship of 100 Ra≥S. The electrode for a lithium battery according to any one of the above.

103. The electrode for a lithium battery according to any one of claims 102 to 103,

An electrode for a lithium battery, wherein the active material thin film is separated into columns by cuts formed in the thickness direction thereof, and a bottom of the columnar portion is in close contact with the current collector.

104. The electrode for a lithium battery according to claim 103, wherein at least 12 or more parts of the thickness in the thickness direction of the thin film are separated into columns by the cuts.

1 0 5. The cut is formed by charge and discharge after the first time.

0 The electrode for a lithium battery according to claim 103, wherein the electrode is a lithium battery.

106. Unevenness is formed on the surface of the active material thin film before charge and discharge, and a break is formed on the surface of the thin film by charge and discharge after the first time, the cut having a valley of the unevenness on the surface as an end. The electrode for a lithium battery according to claim 105, wherein said thin film is separated in a columnar shape by a column.

107. The electrode for a lithium battery according to claim 106, wherein the unevenness on the surface of the active material thin film corresponds to the unevenness on the surface of the current collector serving as an underlayer.

108. The electrode for a lithium battery according to claim 107, wherein the projections of the unevenness on the surface of the current collector have a cone shape.

109. The lithium battery according to any one of claims 103 to 108, wherein an upper portion of the columnar portion has a rounded shape.

110. The electrode for a lithium battery according to claim 103, 104, or 109, wherein the cut is formed in advance before charging and discharging.

111. The lithium battery electrode according to any one of claims 103 to 110, wherein the cut is formed along a low-density region extending in a thickness direction of the active material thin film. Electrode for a lithium battery.

11. The lithium battery electrode according to claim 11, wherein the low-density region extends upward from a valley of unevenness on the surface of the current collector.

11. The electrode for a lithium battery according to claim 11, wherein a component of the current collector is diffused in the active material thin film.

1 1 4. A lithium battery comprising: a negative electrode comprising the electrode according to any one of claims 87 to 113; a positive electrode; and an electrolyte.

0 2

1 1 5. A lithium secondary battery comprising a negative electrode comprising the electrode according to any one of claims 87 to 113, a positive electrode, and a nonaqueous electrolyte.

1 16. The lithium secondary battery according to claim 115, wherein the positive electrode contains an oxide capable of occluding and releasing lithium as an active material.

1 17. The lithium secondary battery according to claim 115, wherein the positive electrode contains a lithium-containing oxide as an active material.

1 1 8. An electrode active material for lithium batteries that absorbs and releases lithium, and is composed of amorphous silicon.

1 1 9. An electrode active material for lithium batteries that absorbs and releases lithium, and is made of microcrystalline silicon.

120. The electrode active material for a lithium battery according to claim 118, wherein the amorphous silicon or the microcrystalline silicon contains hydrogen.

1 2 1. The size of a crystal region in the microcrystalline silicon is 0.5 nm or more as a crystal grain size calculated from an X-ray diffraction spectrum and a Scherrer equation. Item 110. The electrode active material for a lithium battery according to Item 119 or 120.

1 2 2. The 5 20 cm in the Raman spectroscopic analysis of the microcrystalline silicon - ¹ 480 cm- ¹ near the peak intensity ratio of to the peak intensity in the vicinity (48 0 cm- ¹ near Z520 cm- ¹ near) is 0.05 The electrode active material for a lithium battery according to any one of claims 119 to 121, characterized in that:

1 23. An electrode active material for lithium batteries that occludes and releases lithium, characterized by being composed of amorphous silicon containing hydrogen.

0 3 Electrode active material for aluminum batteries.

1 24. An electrode active material for lithium batteries, which is an electrode active material for lithium batteries that occludes and releases lithium, and is composed of microcrystalline silicon containing hydrogen.

1 2 5. The electrode active material for a lithium battery according to any one of claims 120, 123 and 124, wherein the hydrogen concentration is 0.001 atomic% or more.

1 26. Electrode active material for lithium batteries using a silicon thin film made of amorphous silicon.

1 2 7. Electrode active material for lithium batteries using a silicon thin film made of amorphous silicon containing hydrogen.

1 28. Electrode active material for lithium batteries using a silicon thin film made of microcrystalline silicon.

1 2 9. Electrode active material for lithium batteries using a silicon thin film made of microcrystalline silicon containing hydrogen.

130. The amorphous silicon or microcrystalline silicon according to any one of claims 118 to 125 or the silicon thin film according to any one of claims 126 to 129 as lithium in advance. An electrode active material for a lithium battery, comprising:

1 3 1. An electrode active material for a lithium battery made of a material that absorbs and desorbs lithium. An electrode active material for a lithium battery, comprising:

13. An electrode active material for a lithium battery according to claim 13, wherein the amorphous region is disposed around the crystalline region.

1 3 3. It is noted that the crystal region is composed of small crystal grains.

0 4 33. The electrode active material for a lithium battery according to claim 13 or 13.

1 3 4. The elements of Group IV, IV, IVB and VB of the Periodic Table in which the crystalline region and Z or the amorphous region form a compound or solid solution with lithium, 35.A method according to claim 13, wherein the material is composed of at least one material selected from oxides and sulfides of transition metal elements having five and six periods. Electrode active material for lithium batteries.

1 3 5. The element is characterized in that the element is at least one selected from carbon, silicon, germanium, tin, lead, aluminum, indium, zinc, cadmium, bismuth, and mercury. The electrode active material for a lithium battery according to claim 134.

1 36. The electrode active material for a lithium battery according to claim 134, wherein the element is silicon.

13. The electrode active material for a lithium battery according to any one of claims 13 to 13, wherein the amorphous region contains hydrogen.

13. A method according to claim 13, wherein the active material is a thin film formed on a substrate. The electrode active material for a lithium battery according to any one of items 1 to 13.

1 3 9. The electrode for a lithium battery according to any one of claims 17 to 62, 68 to 82, and 96 to:

An electrode for a lithium battery, wherein the current collector has a tensile strength of 3.82 N / mm or more.

Here, the tensile strength of the current collector is a value obtained by the following equation. Tensile strength of current collector (NZmm) = Tensile strength per cross-sectional area of current collector material (N / mm ² ) X Thickness of current collector (mm)

1 40. Any of claims 17-62, 68-82, and 96-113

0 5 In the electrode for a lithium battery according to claim 1,

An electrode for a lithium battery, wherein the current collector has a tensile strength of 7.44 NZmm or more.

Here, the tensile strength of the current collector is a value obtained by the following equation. Tensile strength of current collector (N / mm) = Tensile strength per cross-sectional area of current collector material (N / mm ² ) X Thickness of current collector (mm)

141. The lithium battery according to claim 139 or 140, wherein a ratio of a thickness of the silicon thin film or the active material to a thickness of the current collector is 0.19 or less. electrode.

140. The lithium battery according to claim 139, wherein a ratio of a thickness of the silicon thin film or the active material to a thickness of the current collector is 0.10 or less. Electrodes.

1 4 3. The electrode for a lithium battery according to any one of claims 17 to 62, 68 to 82, and 96 to:

An electrode for a lithium battery, wherein the tensile strength of the current collector per 1 μm thickness of the silicon thin film or the active material is 1.12 N / mm or more.

144. A lithium battery electrode according to any one of claims 1 to 62, 68 to 82, and 96 to:

An electrode for a lithium battery, wherein the tensile strength of the current collector per 1 jum of the thickness of the silicon thin film or the active material is 2.18 N / mm or more.

Here, the tensile strength of the current collector is a value obtained by the following equation.

0 6 Tensile strength of current collector (NZmm) = Tensile strength per cross-sectional area of current collector material (N / mm ² ) X Thickness of current collector (mm)

1 4 5. The electrode for a lithium battery according to any one of claims 17 to 62, 68 to 82, and 96 to:

An electrode for a lithium battery, wherein the tensile strength of the current collector per 1 / zm of the thickness of the silicon thin film or the active material is 4.25 NZmm or more.

Here, the tensile strength of the current collector is a value obtained by the following equation. Tensile strength of current collector (NZmtn) = Tensile strength per cross-sectional area of current collector material (NZmm ² ) X Thickness of current collector (mm)

1 4 6. The electrode for a lithium battery according to any one of claims 17 to 62, 68 to 82, and 96 to:

An electrode for a lithium battery, wherein a ratio of a thickness of the silicon thin film or the active material to a thickness of the current collector is 0.19 or less.

1 4 7. The electrode for a lithium battery according to any one of claims 17 to 62, 68 to 82, and 96:

An electrode for a lithium battery, wherein a ratio of a thickness of the silicon thin film or the active material to a thickness of the current collector is 0.098 or less.

1 4 8. The electrode for a lithium battery according to any one of claims 17 to 62, 68 to 82, and 96 to 110:

An electrode for a lithium battery, wherein a ratio of a thickness of the silicon thin film or the active material to a thickness of the current collector is 0.05 or less.

1 4 9. In a lithium secondary battery that includes a negative electrode in which an active material thin film that expands and contracts by absorbing and releasing lithium on a negative electrode current collector, a positive electrode, and a nonaqueous electrolyte,

The negative electrode current collector has a tensile strength of at least 3.82 NZmm.

0 7 Lithium secondary battery.

150. The lithium secondary battery according to claim 149, wherein the negative electrode current collector has a tensile strength of 7.44 NZmm or more.

150. The lithium secondary battery according to claim 149 or 150, wherein a ratio of a thickness of the active material thin film to a thickness of the current collector is 0.19 or less.

150. The lithium secondary battery according to claim 149 or 150, wherein a ratio of a thickness of the active material thin film to a thickness of the current collector is 0.10 or less.

1 5 3. In a lithium secondary battery that includes a negative electrode in which an active material thin film that expands and contracts by absorbing and releasing lithium on a negative electrode current collector, a positive electrode, and a nonaqueous electrolyte,

An electrode for a lithium battery, wherein the tensile strength of the negative electrode current collector per 1 μm of the thickness of the active material thin film is 1.12 NZmm or more.

1 54. In a lithium secondary battery that includes a negative electrode in which an active material thin film that expands and contracts by absorbing and releasing lithium on a negative electrode current collector, a positive electrode, and a nonaqueous electrolyte,

An electrode for a lithium battery, wherein the negative electrode current collector has a tensile strength of 2.18 NZmm or more per 1 μm thickness of the active material thin film.

0 8 Tensile strength of current collector (N / mm) = Tensile strength per cross-sectional area of current collector material (N / mm ² ) X Thickness of current collector (mm)

1 5 5. In a lithium secondary battery that includes a negative electrode in which an active material thin film that expands and contracts by absorbing and releasing lithium on a negative electrode current collector, a positive electrode, and a nonaqueous electrolyte,

An electrode for a lithium battery, wherein the negative electrode current collector has a tensile strength of 4.25 N mm or more per 1 μm thickness of the active material thin film.

1 5 6. In a lithium secondary battery comprising a negative electrode with an active material thin film that expands and contracts by absorbing and releasing lithium on a negative electrode current collector, a positive electrode, and a non-aqueous electrolyte,

An electrode for a lithium battery, wherein a ratio of a thickness of the active material thin film to a thickness of the negative electrode current collector is 0.19 or less.

1 5 7. In a lithium secondary battery comprising a negative electrode with an active material thin film that expands and contracts by absorbing and releasing lithium on a negative electrode current collector, a positive electrode, and a non-aqueous electrolyte,

An electrode for a lithium battery, wherein a ratio of a thickness of the active material thin film to a thickness of the negative electrode current collector is 0.098 or less.

1 5 8. In a lithium secondary battery that includes a negative electrode with an active material thin film that expands and contracts by absorbing and releasing lithium on a negative electrode current collector, a positive electrode, and a nonaqueous electrolyte,

An electrode for a lithium battery, wherein a ratio of a thickness of the active material thin film to a thickness of the negative electrode current collector is 0.05 or less.

1 5 9. The surface roughness Ra of the negative electrode current collector is 0.01 to 1 μιη

0 9 158. The lithium secondary battery according to any one of claims 149 to 158.

160. The lithium secondary battery according to any one of claims 149 to 159, wherein the negative electrode current collector is a copper foil.

160. The lithium secondary battery according to claim 160, wherein the copper foil is an electrolytic copper foil.

162. The lithium secondary battery according to any one of claims 149 to 161, wherein the active material thin film is a thin film containing silicon or germanium.

16 3. The lithium secondary battery according to claim 16, wherein the active material thin film is a silicon thin film, a germanium thin film, or a silicon germanium alloy thin film.

164. The lithium secondary battery according to claim 163, wherein said silicon thin film is a microcrystalline silicon thin film or an amorphous silicon thin film.

1 6 5. The electrode for a lithium battery according to any one of claims 17 to 62, 68 to 82, and 96 to:

A lithium battery, wherein a silicon thin film or an active material thin film is provided on a current collector via an intermediate layer, and the intermediate layer is formed of a material alloying with the silicon thin film or the active material thin film. Electrodes.

166. The electrode for a lithium battery according to claim 165, wherein the current collector is a foil made of a metal or an alloy having higher mechanical strength than the material of the intermediate layer.

1 6 7. An unevenness is formed on the surface of the current collector, and the unevenness is formed on the surface of the intermediate layer corresponding to the unevenness on the surface of the current collector. 65. The electrode for a lithium battery according to 65 or 166.

0

1 6 8. The method according to claim 1, wherein the surface roughness Ra of the current collector surface is 0.001 to 1 μιη or 0.01 to 1 μm. The electrode for a lithium battery according to any one of the above items.

169. The electrode for a lithium battery according to any one of claims 165 to 168, wherein the active material thin film is a germanium thin film or a silicon germanium alloy thin film.

170. The electrode for a lithium battery according to any one of claims 16 to 169, wherein the current collector is a nickel foil.

170. The electrode for a lithium battery according to any one of claims 165 to 170, wherein the intermediate layer is a copper layer.

1 7 2. In a lithium secondary battery including a negative electrode in which an active material thin film that absorbs and releases lithium is formed on a negative electrode current collector, a positive electrode, and a nonaqueous electrolyte,

A lithium secondary battery comprising: an intermediate layer made of a material alloying with the active material thin film provided on the negative electrode current collector; and the active material thin film formed on the intermediate layer.

173. The lithium secondary battery according to claim 172, wherein the active material thin film is a thin film formed by a CVD method, a sputtering method, a vacuum evaporation method, or a thermal spraying method.

174. The active material thin film is a silicon thin film, a germanium thin film, or a silicon germanium alloy thin film.

2. The lithium secondary battery according to 2 or 173.

175. The lithium secondary battery according to claim 174, wherein the silicon thin film is a microcrystalline silicon thin film or an amorphous silicon thin film.

1 7 6. The method according to claim 1, wherein the intermediate layer is a copper layer. 17. The lithium secondary battery according to any one of 1 75.

17. The method according to claim 17, wherein the current collector is a foil made of a metal or an alloy having higher mechanical strength than the material of the intermediate layer. Lithium secondary battery.

178. An unevenness is formed on a surface of the current collector, and an unevenness is formed on a surface of the intermediate layer corresponding to the unevenness on the surface of the current collector. ~: The lithium secondary battery according to any one of 177.

1 7 9. The surface roughness Ra of the current collector surface is 0.001 to l / zm or 0.01 to 1 // m. 78. The lithium secondary battery according to any one of the items 1 to 78.

180. The lithium secondary battery according to any one of claims 172-179, wherein the current collector is a nickel foil.

1 8 1. An electrode for a lithium secondary battery comprising a plate-shaped current collector and an active material thin film that absorbs and releases lithium, which is formed by being deposited on both surfaces of the current collector.

18. The electrode for a lithium secondary battery according to claim 18, wherein the current collector is a metal foil.

18. The electrode for a lithium secondary battery according to claim 18, wherein the metal foil is a copper foil.

184. The electrode for a lithium secondary battery according to claim 183, wherein the copper foil is an electrolytic copper foil.

185. The lithium secondary battery according to any one of claims 181-184, wherein both surfaces of the current collector have substantially the same surface roughness Ra. Electrodes for secondary batteries.

1 8 6. The surface roughness Ra of both surfaces of the current collector is 0.01 ~

Two The electrode for a lithium secondary battery according to claim 18, wherein the electrode has a thickness of 1 μm.

187. The electrode for a lithium secondary battery according to any one of claims 181-186, wherein the active material thin film is a silicon thin film or a germanium thin film.

188. The electrode for a lithium secondary battery according to claim 187, wherein the silicon thin film is a microcrystalline silicon thin film or an amorphous silicon thin film.

189. The electrode for a lithium secondary battery according to claim 187, wherein the germanium thin film is an amorphous germanium thin film.

190. The active material thin film is separated into columns by cuts formed in the thickness direction thereof, and the bottom of the columnar portion is in close contact with the current collector. Item 18. The electrode for a lithium secondary battery according to any one of Items 181-189.

190. The lithium secondary battery according to claim 190, wherein at least 12 or more portions of the thickness in the thickness direction of the active material thin film are separated into columns by the cuts. Electrodes.

190. The electrode for a lithium secondary battery according to claim 190, wherein the cut is formed by expansion and contraction of the active material thin film.

193. The electrode for a lithium secondary battery according to any one of claims 190 to 192, wherein the cut is formed by a charge / discharge reaction after assembling the battery.

194. The electrode for a lithium secondary battery according to any one of claims 190 to 192, wherein the cut is formed by a charge / discharge reaction before assembling the battery.

Three

1 9 5. Irregularities are formed on the surface of the active material thin film, and the cuts are formed in the thickness direction from the valleys of the irregularities on the thin film surface toward the current collector. The electrode for a lithium secondary battery according to any one of claims 190 to 194.

196. The electrode for a lithium secondary battery according to claim 195, wherein the unevenness on the surface of the thin film is formed corresponding to the unevenness on the surface of the current collector.

197. The electrode for a lithium secondary battery according to claim 196, wherein the projections of the unevenness on the surface of the current collector have a cone shape.

199 8. The electrode for a lithium secondary battery according to any one of claims 190 to 197, wherein an upper portion of the columnar portion has a rounded shape.

1 9 9. The active material thin film before the cut is formed is formed with a low-density region extending in a thickness direction toward the current collector in a network direction in the plane direction. 199. The electrode for a lithium secondary battery according to any one of claims 190 to 198, wherein the cut is formed in the thickness direction along the region.

200. A lithium secondary battery using the electrode for a lithium secondary battery according to any one of claims 181-199.

20 1. A current collector for a lithium secondary battery electrode, having a surface formed by depositing an active material thin film for absorbing and releasing lithium on both surfaces.

20. The current collector for a lithium secondary battery electrode according to claim 20, wherein said both surfaces have substantially the same surface roughness Ra.

20. The current collector for a lithium secondary battery electrode according to claim 20, wherein the surface roughness Ra of the both surfaces is 0.01 to l // m, respectively.

Four

204. The current collector for a lithium secondary battery electrode according to any one of claims 201 to 203, wherein the current collector is a metal foil.

205. The current collector for a lithium secondary battery electrode according to claim 204, which is a copper foil.

206. The current collector for a lithium secondary battery electrode according to claim 205, which is an electrolytic copper foil.

207. The current collector for a lithium secondary battery electrode according to claim 206, wherein the current collector is an electrolytic copper foil obtained by depositing copper on both surfaces of a copper foil by an electrolytic method.

208. A negative electrode comprising the electrode for a lithium secondary battery according to any one of claims 181-199, and a positive electrode provided with a positive electrode active material on both sides of a current collector, A lithium secondary battery having an electrode structure alternately stacked with a separator interposed therebetween.

209. Between the negative electrode comprising the electrode for a lithium secondary battery according to any one of claims 18 1 to 199, and a positive electrode having a positive electrode active material provided on both surfaces of a current collector. A lithium secondary battery having an electrode structure in which a separator is interposed and spirally wound around the separator.

210. A positive electrode provided with a pair of positive electrode active material layers facing each other inside a current collector bent in a U-shape,

A negative electrode active material layer is provided on both surfaces of the current collector, and a negative electrode inserted inside the U-shaped positive electrode;

10. A lithium secondary battery, wherein the negative electrode is the electrode for a lithium secondary battery according to any one of claims 18 to 199.

Five