JP5238195B2 - Negative electrode for lithium ion secondary battery and lithium ion secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain diffusion of constituent elements of a collector into an active material layer. <P>SOLUTION: The anode for a lithium ion secondary battery contains a collector, an intermediate layer formed on the surface of the collector, and an active material layer formed at an extension of the intermediate layer. The collector contains metal capable of forming an alloy with silicon, the active material layer contains an active material containing silicon, and the intermediate layer contains silicon and oxygen. The intermediate layer restrains metal capable of forming an alloy with silicon from diffusing in the active material layer. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a lithium ion secondary battery, and more particularly to a negative electrode for a lithium ion secondary battery.

  In recent years, with the development of portable devices such as personal computers and mobile phones, the demand for batteries as power sources has increased. A battery used for the above applications is required to be used at room temperature, and at the same time, a high energy density and excellent cycle characteristics are required. Therefore, silicon (Si) or tin (Sn) alone, their oxides or alloys are promising as negative electrode active materials that can provide very high capacity.

  However, when these materials occlude lithium, the crystal structure changes and the volume increases. When the volume change of the active material during charging / discharging is large, poor contact between the active material and the current collector occurs. Therefore, the charge / discharge cycle life is shortened.

Therefore, Patent Document 1 proposes forming an amorphous silicon thin film on a copper foil by vapor deposition or sputtering. Here, it is stated that since copper diffuses into the silicon thin film, the bonding between the silicon thin film and the copper foil becomes strong, and even if the silicon expands, the current collecting property does not decrease.
However, since the diffusion coefficient of copper in silicon is large, copper may diffuse excessively into the silicon thin film. As a result, the copper foil becomes brittle, and further, the charge and discharge capacity is reduced by alloying silicon and copper.

Patent Document 2 proposes forming an intermediate layer made of Mo or W on the surface of the current collector. The intermediate layer prevents excessive diffusion of the constituent elements of the current collector into the active material layer.
Japanese Patent No. 3702224 JP 2002-373644 A

  Patent Document 1 proposes to control the temperature of the current collector to be less than 300 ° C. when forming the silicon thin film in order to prevent excessive diffusion of copper into the silicon thin film. However, it is difficult to suppress diffusion only by controlling the temperature below 300 ° C. because the diffusion coefficient of copper in silicon is large. Further, in the vapor deposition method or the sputtering method, when the film formation rate is increased to increase the production efficiency, the temperature of the copper foil increases. In order to control the temperature of the copper foil to less than 300 ° C., it is necessary to keep the film formation rate low, and the production efficiency is lowered.

  When a silicon thin film is formed on a copper foil, internal stress is accumulated in the silicon thin film, and the copper foil may bend. Such internal stress is relieved by heat-treating the formed silicon thin film together with the copper foil. However, copper may diffuse excessively into the silicon thin film due to the heat treatment.

  As a method for compensating for the irreversible capacity of the negative electrode, a method of depositing lithium on a silicon thin film is effective. However, when depositing lithium, the temperature of the copper foil increases, and copper may diffuse excessively into the silicon thin film.

  As described above, with the method of Patent Document 1, it is difficult to control the diffusion of copper into the silicon thin film. When the amount of copper diffusion changes, the charge / discharge capacity of the silicon thin film changes, making it difficult to obtain stable quality. Moreover, in the method of patent document 1, since the interface of copper foil and a silicon thin film becomes weak, a silicon thin film peels in the case of charging / discharging, and cycling characteristics fall.

  Patent Document 2 proposes forming an intermediate layer containing tungsten or molybdenum. However, tungsten or molybdenum does not act as an active material. When a material that does not act as an active material is used as the intermediate layer, the energy density of the negative electrode is reduced. Further, since tungsten and molybdenum are high melting point materials, it is difficult to increase the deposition rate. Therefore, enormous costs are required for forming the intermediate layer, such as device costs and operation costs.

The present invention includes a current collector, an intermediate layer formed on the surface of the current collector, and an active material layer formed as an extension of the intermediate layer. The current collector is a metal capable of forming an alloy with silicon. The active material layer includes an active material including silicon, the intermediate layer includes silicon and oxygen, and the intermediate layer prevents a metal capable of forming an alloy with silicon from diffusing into the active material layer. In the active material layer, the active material forms a plurality of columnar particles, and the columnar particles are grown with an inclination with respect to the normal direction of the surface of the current collector. It is related with the negative electrode for lithium ion secondary batteries containing the laminated body of a particle layer .

  By forming the intermediate layer between the current collector and the active material layer, the constituent elements of the current collector can be prevented from diffusing into the active material layer. The reason why the intermediate layer containing silicon and oxygen has an action of suppressing the diffusion of the constituent elements of the current collector has not been fully elucidated at present, but is presumed as follows.

  In the intermediate layer containing silicon and oxygen, the silicon and oxygen are bonded by a strong covalent bond. Therefore, in order for the constituent elements of the current collector to diffuse through the intermediate layer, the constituent elements of the current collector need to cut the bond between silicon and oxygen and bond to silicon. However, even a metal capable of forming an alloy with silicon (for example, copper or nickel), it is difficult to break the bond between silicon and oxygen and bond with silicon. Therefore, by interposing the intermediate layer containing silicon and oxygen between the current collector and the active material layer, diffusion of the constituent elements of the current collector into the active material layer is suppressed.

The negative electrode of the present invention, on a current collector comprising a metal capable of forming a divorced alloy, forming an intermediate layer containing silicon and oxygen suppressing diffusion of the metal, the intermediate layer, the active produced by the process of chromatic and forming the material layer. Here, the temperature of the current collector when forming at least one of the intermediate layer and the active material layer is 300 ° C to 700 ° C.

Upper SL Manufacturing method may include the step of depositing the lithium in the active material layer. In this case, the temperature of the current collector when depositing lithium is preferably 300 ° C to 700 ° C.

Upper SL Manufacturing method comprises a current collector and the intermediate layer and the active material layer may include a step of heat treatment (heating) at the same time. In this case, the temperature of the heat treatment (heating) is preferably 300 ° C to 700 ° C.

  According to the said method, the production efficiency of the negative electrode for lithium ion secondary batteries can be improved. For example, it is possible to increase the film formation rate and select manufacturing conditions for forming the active material layer in a short time. In addition, after the formation of the active material layer, a high-temperature and short-time condition can be selected as a heat treatment condition for removing moisture attached to the surface.

  By forming an intermediate layer between the current collector and the active material layer, diffusion of constituent elements of the current collector into the active material layer can be suppressed. Therefore, the current collector is not weakened and the bond between the active material layer and the current collector is maintained. As a result, a lithium ion secondary battery with good cycle characteristics can be provided.

  Similar to the active material layer, the intermediate layer includes silicon. That is, the intermediate layer can occlude and release lithium and also functions as an active material. Therefore, even when the intermediate layer is formed, the energy density of the negative electrode is not reduced, and a lithium ion secondary battery having a large capacity can be provided. Further, since the intermediate layer contains silicon like the active material layer, the manufacturing process can be simplified and the production efficiency can be improved. Therefore, the negative electrode can be manufactured at a low cost.

Hereinafter, description will be given with reference to the drawings. However, the present invention is not limited to the following contents.
FIG. 1 is a schematic cross-sectional view of an example of a stacked lithium ion secondary battery.
The battery 10 includes an electrode plate group including a positive electrode 11, a negative electrode 12, and a separator 13 interposed therebetween. The electrode group and the electrolyte having lithium ion conductivity are accommodated in the exterior case 14. The separator 13 is impregnated with an electrolyte having lithium ion conductivity. The positive electrode 11 includes a positive electrode current collector 11a and a positive electrode active material layer 11b supported on the positive electrode current collector 11a. The negative electrode 12 includes a negative electrode current collector 12a and a negative electrode intermediate material supported on the negative electrode current collector 12a. It consists of a layer (hereinafter referred to as an intermediate layer) 12b and a negative electrode active material layer 12c. One end of a positive electrode lead 15 and a negative electrode lead 16 is connected to the positive electrode current collector 11 a and the negative electrode current collector 12 a, respectively, and the other end is led out of the exterior case 14. The opening of the outer case 14 is sealed with a resin material 17.

  The positive electrode active material layer 11b releases lithium during charging, and occludes lithium released by the intermediate layer 12b and the negative electrode active material layer 12c during discharge. The intermediate layer 12b and the negative electrode active material layer 12c occlude lithium released by the positive electrode active material layer 11b during charging, and release lithium during discharge.

  FIG. 2 is a schematic cross-sectional view showing the structure of the negative electrode 12. An intermediate layer 12b is formed on the surface of a negative electrode current collector (hereinafter referred to as current collector) 12a, and a negative electrode active material layer (hereinafter referred to as active material layer) 12c is formed as an extension of the intermediate layer 12b.

  FIG. 3 is a schematic cross-sectional view showing the structure of the active material layer 12c. The intermediate layer 12 b and the active material layer 12 c include a plurality of columnar particles 30. The columnar particles 30 grow obliquely with respect to the normal direction D1 of the surface of the current collector 12a. The angle between the growth direction D2 of the columnar particles 30 and the normal direction D1 of the surface of the current collector 12a is θ (for example, 10 ° ≦ θ ≦ 80 °). The columnar particles 30 include lower columnar particles 31 and upper columnar particles 32. The lower columnar particles 31 constitute an intermediate layer 12b, and the upper columnar particles 32 constitute an active material layer 12c.

  Each of the lower columnar particles 31 and the upper columnar particles 32 may be a single crystal particle, a polycrystalline particle including a plurality of crystallites (crystal grains), or a crystallite having a crystallite size of 100 nm or less. However, it may be amorphous (amorphous). The growth directions of the lower columnar particles 31 and the upper columnar particles 32 may be the same or different.

  A plurality of columnar particles adjacent to each other may coalesce during growth. However, each columnar particle has a different starting point of growth. Therefore, the number of columnar particles may be considered to be the same as the number of growth starting points.

  Although FIG. 1 shows an example of a laminated lithium ion secondary battery, the negative electrode for a lithium ion secondary battery of the present invention is naturally applicable to a cylindrical battery or a square battery having a spiral electrode plate group. it can. In a stacked lithium ion secondary battery, a positive electrode having a positive electrode active material layer on both sides or one side and a negative electrode having a negative electrode active material layer on both sides or one side may be laminated in three or more layers. In that case, an electrode is arrange | positioned so that all the positive electrode active material layers may oppose a negative electrode active material layer, and all the negative electrode active material layers may oppose a positive electrode active material layer. The inclination direction of the columnar particles in each negative electrode active material layer may be the same or different. Columnar particles having different inclination directions may be formed in the same negative electrode. In the case of a negative electrode having negative electrode active material layers on both sides, the inclination directions of the columnar particles on both sides may be the same or different.

  The intermediate layer includes silicon and oxygen. Silicon and oxygen are bound by a strong covalent bond. Therefore, in order for the constituent elements of the current collector to diffuse through the intermediate layer, the constituent elements of the current collector need to cut the bond between silicon and oxygen and bond to silicon. However, even a metal capable of forming an alloy with silicon (for example, copper or nickel), it is difficult to break the bond between silicon and oxygen and bond with silicon. Therefore, by interposing an intermediate layer containing silicon and oxygen between the current collector and the active material layer, diffusion of copper and nickel, which are constituent elements of the current collector, into the active material layer is suppressed. .

The intermediate layer containing silicon and oxygen is made of, for example, silicon oxide or a mixture of silicon alone and silicon oxide. Here, both silicon simple substance and silicon oxide function as an active material. The composition of the intermediate layer may be uniform or non-uniform. The distribution state of silicon and oxygen in the intermediate layer is not particularly limited. The intermediate layer may be locally composed of silicon alone or SiO ₂ . The intermediate layer may contain elements other than silicon and oxygen, such as carbon (C) and nitrogen (N).

  The thickness of the intermediate layer is preferably 0.1 μm or more, or 1 μm or more, and preferably 10 μm or less. When the thickness of the intermediate layer is smaller than 0.1 μm, the diffusion of the constituent elements of the current collector into the active material layer may not be prevented. On the other hand, the thickness of the active material layer is preferably 0.1 μm to 100 μm, and in particular, the total thickness of the active material layer and the intermediate layer is preferably 100 μm or less, or 50 μm or less. When the total thickness is larger than 100 μm, the expansion stress of the active material layer during charging may become excessively large.

  The thickness of the active material layer, the thickness of the intermediate layer, or the total thickness of the active material layer and the intermediate layer is measured on the surface of the current collector, the surface of the intermediate layer, and the surface of the active material layer observed in the cross section of the negative electrode. It can be determined using the corresponding center line. That is, the thickness of the active material layer is the distance from the center line indicating the surface of the intermediate layer to the center line indicating the surface of the active material layer, and the thickness of the intermediate layer is intermediate from the center line indicating the surface of the current collector The total thickness of the active material layer and the intermediate layer is the distance from the center line indicating the surface of the current collector to the center line indicating the surface of the active material layer. .

  Here, the “center line” is a term used in the JIS standard that defines the surface roughness Ra, and means a straight line obtained from the average value of the roughness curves. Specifically, the negative electrode having the intermediate layer and the active material layer is filled with resin, the resin is cured, and the negative electrode filled with resin is polished so that a cross section perpendicular to the main flat surface of the current collector is obtained. To do. The polished cross section is observed with an SEM, and center lines indicating the surface of the current collector, the surface of the intermediate layer, and the surface of the active material layer are obtained.

  However, simply, using a general thickness measurement device, measure the thickness of the current collector, measure the thickness of the current collector after forming the intermediate layer, and if the difference between these is determined, The layer thickness can be calculated. Similarly, the thickness of the current collector is measured, and the thickness of the current collector (negative electrode) after forming the intermediate layer and the active material layer is measured. The total thickness can be calculated. It has been experimentally found that the calculation result in this case almost coincides with the thickness measured strictly using the center line.

The intermediate layer includes, for example, silicon oxide represented by SiO _x . The range of x value indicating the oxygen content is 0.1 ≦ x <2 or 0.1 ≦ x ≦ 1 from the viewpoint of suppressing the diffusion of the constituent elements of the current collector such as copper and nickel. Is preferred. However, according to the study by the present inventors, even if the oxygen contained in the intermediate layer is small (even if the x value is small), the diffusion of the constituent elements of the current collector into the active material layer is suppressed. Is done.

  A metal that can form an alloy with silicon, which is a constituent element of the current collector, may diffuse into the intermediate layer to form a mixed layer. The mixed layer includes a constituent element of the current collector, silicon, and oxygen. The thickness of the mixed layer is desirably 1 μm or less. When the thickness of the mixed layer is greater than 1 μm, the current collector may become weak. When the current collector is weakened, current collection may be reduced between the current collector and the intermediate layer or the active material layer, and cycle characteristics may be deteriorated. Further, since the constituent elements of the current collector form an alloy with silicon contained in the intermediate layer and the active material layer, the battery capacity may be reduced.

Here, the thickness of the mixed layer is obtained by plane analysis of the interface between the current collector and the intermediate layer in parallel with the main flat surface of the current collector. At this time, a section in which the ratio of the constituent elements of the current collector to the total elements present on the analysis surface is 10 mol% to 90 mol% is defined as a mixed layer. The surface analysis is performed by, for example, X-ray photoelectron spectroscopy (ESCA), Auger electron spectroscopy, secondary ion mass spectrometry, or the like. In surface analysis, elements contained in a region having a thickness of about several tens of nanometers can be quantified.
For example, when the current collector is a copper foil and the elements present (detected) on the analysis surface are Cu, Si, and O, the ratio of the constituent elements of the current collector (the element ratio of copper) is ( The number of moles of Cu / (number of moles of Cu + number of moles of Si + number of moles of O).

  Even when there is no mixed layer, the bonding force at the interface is sufficient and there is no particular problem. However, with the current analysis method described below, it is difficult to prove that there is no mixed layer between the current collector of a certain area and the intermediate layer.

  The thickness of the mixed layer is synonymous with the thickness of the section (diffusion width) in which the element ratio of the constituent elements of the current collector is 10 mol% to 90 mol%. The relationship between the distance in the depth direction in the intermediate layer and the element ratio can be determined by X-ray photoelectron spectroscopy, Auger electron spectroscopy, secondary ion mass spectrometry, or the like. Specifically, the surface analysis of the intermediate layer is performed in a direction parallel to the main flat surface of the current collector, and the operation of quantifying the element ratio and the operation of scraping the intermediate layer by sputtering of ions such as argon are repeated. In such a method, the mixed layer tends to be observed to be thick due to atomic level unevenness on the analysis surface and variations in the analysis surface of argon sputtering.

  The active material layer includes an active material containing silicon. The active material layer may contain oxygen, nitrogen, or titanium in addition to silicon. Examples of the active material containing silicon include silicon simple substance, silicon alloy, compound or silicon oxide containing silicon and oxygen, compound or silicon nitride containing silicon and nitrogen, compound or alloy containing silicon and titanium, and the like. It is done. These may constitute the active material layer alone, or a plurality of types may constitute the active material layer in any combination. Examples of the active material layer formed of a plurality of types of active materials include an active material layer containing silicon, oxygen, and nitrogen, and an active material layer containing a composite of a plurality of silicon oxides having different oxygen contents. . The active material layer may have the same composition as the intermediate layer.

  In a compound or alloy containing silicon and titanium, the molar ratio of Ti atom to Si atom: Ti / Si is preferably 0 <Ti / Si <2, particularly preferably 0.1 ≦ Ti / Si ≦ 1.0. . Such an active material is preferable in that it has a small irreversible capacity and a small volume change accompanying expansion and contraction. Titanium is inexpensive. If the Ti / Si value is too small, the stress during expansion is large, and the active material layer may be cracked or peeled off from the current collector. If the Ti / Si value is too large, the charge / discharge capacity is reduced, and the characteristics of high-capacity silicon cannot be fully utilized.

The compound or silicon oxide containing silicon and oxygen is represented by the general formula (1): SiO _x , and the x value indicating the oxygen content is 0 <x <2 or 0.01 ≦ x ≦ 1. It is desirable to have a composition. Such an active material is preferable in that it has a small irreversible capacity and a small volume change accompanying expansion and contraction. When the x value is too small, the stress during expansion is large, and the active material layer may be cracked or peeled off from the current collector. If the x value is too large, the charge / discharge capacity decreases, and the characteristics of high-capacity silicon may not be fully utilized. The intermediate layer includes silicon oxide represented by SiO _x1 (0.1 ≦ x1 <2), and the active material layer is silicon oxide represented by SiO _x2 (0.01 ≦ x2 ≦ 1). Is included, it is preferable that 1 <x1 / x2 ≦ 10 or 2 ≦ x1 / x2 ≦ 10 from the viewpoint of sufficiently preventing diffusion of the constituent elements of the current collector into the active material layer.

The compound or silicon nitride containing silicon and nitrogen is represented by the general formula (2): SiN _y , and the y value indicating the nitrogen content is 0 <y <4/3 or 0.01 ≦ y ≦ 1. It is desirable to have a composition that is Such an active material is preferable in that it has a small irreversible capacity and a small volume change accompanying expansion and contraction. Nitrogen is inexpensive. If the y value is too small, the stress during expansion is large, and the active material layer may be cracked or peeled off from the current collector. If the y value is too large, the charge / discharge capacity decreases, and the characteristics of high-capacity silicon may not be fully utilized.

  In the negative electrode for a lithium ion secondary battery of the present invention, each of the intermediate layer and the active material layer may be a homogeneous (uniform) film, or may be composed of a plurality of columnar particles. When the intermediate layer and the active material layer are formed of columnar particles, the sizes of the particles are easily aligned. When the size of the columnar particles is uniform, the reaction at the time of charging / discharging becomes uniform. On the other hand, if the intermediate layer and the active material layer are in the form of a uniform film, random cracks occur in the intermediate layer or the active material layer with charging. As a result, large and small columnar particles may be formed.

  The active material layer including a plurality of columnar particles can be obtained, for example, by providing irregularities on the surface of the current collector and depositing the active material on the surface. The columnar particles may be in contact with each other, but are preferably not in contact with each other. The columnar particles may be grown in parallel to the normal direction of the surface (main flat surface) of the current collector, or may be grown so as to be inclined with respect to the normal direction of the surface of the current collector. When the columnar particles are inclined with respect to the normal direction of the surface of the current collector, a space is easily formed between adjacent columnar particles, so that stress is easily relieved when the active material expands.

Columnar particles, that contain a stack of a plurality of grain layers grown inclined with respect to the direction normal to the surface of the current collector (grain layer). At this time, it is preferable that the plurality of grain layers are grown with inclination in different directions. Thereby, since a space can be formed around the columnar particles, stress is easily relieved during expansion of the active material, and contact between adjacent columnar particles can be suppressed. By laminating grain layers that are inclined in different directions, it is possible to form columnar particles that apparently grow substantially parallel to the normal direction of the surface of the current collector. The columnar particles grown in this way have less stress at the interface between the active material and the current collector that is generated when the active material expands. Therefore, even when the thickness of the active material layer is large, generation of wrinkles is suppressed.

The state in which the plurality of grain layers are grown in different directions will be described with reference to the drawings.
The columnar particles in FIG. 4 include a laminate of a plurality of particle layers inclined with respect to the normal direction of the surface of the current collector. The columnar particles 12c include particle layers 101 to 108 that are inclined with respect to the normal direction of the surface of the current collector. These grain layers are inclined in different directions. For example, the inclination direction d1 of the particle layer 101 in contact with the negative electrode intermediate layer 12b and the inclination direction of the particle layer 102 in contact with the particle layer 101 are d2 with respect to a plane perpendicular to the current collector 12a. Symmetry is preferred. Similarly, the relationship between adjacent particle layers is preferably symmetrical with respect to a plane perpendicular to the current collector 12a.

  Although the total thickness t of the active material layer and the intermediate layer depends on the diameter of the columnar particles, for example, when the active material contains lithium corresponding to irreversible capacity or does not contain lithium, for example, 0.2 μm ≦ It is preferable that t ≦ 100 μm or 1 μm ≦ t ≦ 50 μm. If the total thickness t of the active material layer and the intermediate layer is 0.1 μm or more, a certain level of energy density can be secured and the high capacity characteristics of the lithium ion secondary battery can be fully utilized. If the total thickness t of the active material layer and the intermediate layer is 100 μm or less, the proportion of each columnar particle shielded by other columnar particles can be kept low. Moreover, since the current collection resistance from the columnar particles can be suppressed to a low level, it is advantageous for high-rate charge / discharge.

  The current collector includes a metal capable of forming an alloy with silicon. The metal capable of forming an alloy with silicon is preferably copper or nickel. Copper or nickel is a metal that does not form an alloy with lithium and is advantageous in that it is inexpensive. The main flat surface of the current collector is flat when visually observed, but preferably has irregularities when viewed microscopically.

  The thickness of the current collector is preferably 1 μm to 50 μm, for example. When the thickness is less than 1 μm, the current collecting resistance increases, and the function as a current collector may be impaired. When the thickness is larger than 50 μm, the energy density of the electrode is lowered.

The current collector desirably has irregularities on the surface carrying the intermediate layer. Specifically, the surface carrying the intermediate layer of the current collector desirably has convex portions of 100,000 to 10 million pieces / cm ² per unit area. The greater the number of protrusions per unit area, the more advantageous is the increase in the number of columnar particles carried per unit area. However, the porosity P of the negative electrode tends to be small. The smaller the number of protrusions per unit area, the more advantageous is the reduction in the number of columnar particles carried per unit area. Therefore, it is desirable to control the number of convex portions per unit area of the current collector according to the desired porosity P of the negative electrode.

  The surface roughness (ten-point average height) Rz of the surface (main flat surface) carrying the intermediate layer of the current collector is preferably 0.1 to 100 μm. When the surface roughness Rz is small, it may be difficult to provide an interval between the columnar particles adjacent to each other. As the surface roughness Rz increases, the average thickness of the current collector increases. However, if Rz is 100 μm or less, the high capacity characteristics of the lithium ion secondary battery can be fully utilized. The surface roughness Rz can be measured by a method defined in Japanese Industrial Standard (JIS).

  As the above current collector, for example, an electrolytic copper foil, an electrolytic copper alloy foil, an electrolytic copper foil subjected to a roughening treatment, a rolled copper foil subjected to a roughening treatment, or the like can be preferably used. The roughening treatment refers to a treatment in which a copper foil is immersed in a solution and chemically etched to give unevenness, or a treatment in which copper particles are electrodeposited on the copper foil to give unevenness. In these methods, irregularities are randomly formed.

  The surface carrying the intermediate layer of the current collector (main flat surface) preferably has irregularities formed in a regular pattern. When the surface of the current collector has such irregularities, the intermediate layer or active material layer formed thereon is uniform. Therefore, the quality of the electrode is stabilized.

  As a method of forming irregularities on the surface of the current collector in a regular pattern, a method of performing etching or plating processing at a regular position using a resist on the current collector, and pressing a mold against the current collector There is a method of mechanically forming irregularities. Forming irregularities regularly is desirable in that the size of the columnar particles is homogenized. The columnar particles may be formed on either the concave portion or the convex portion of the current collector, but are preferably formed on the convex portion of the current collector from the viewpoint of forming a space between the columnar particles.

  When the constituent elements of the current collector are diffused into the intermediate layer to form a mixed layer, the mixed layer may include at least one element X selected from the group consisting of chromium, carbon, and hydrogen. However, the content of the element X in the mixed layer is preferably 10 mol% or less with respect to copper in the mixed layer. The surface of the current collector is generally coated with chromium or an oil / fat component as an antirust treatment. Even if these substances remain on the surface of the current collector, there is no particular problem with the formation of the active material layer. There is no problem in battery characteristics. Therefore, there is no problem even if the active material layer is formed without particularly removing chromium and oil and fat components. That is, there is no problem even if a rust-preventing component (element X) such as chromium, carbon, or hydrogen is present at the interface between the current collector and the intermediate layer. When the content of the element X is greater than 10 mol%, the efficiency of attaching the active material to the current collector may be reduced during the formation of the active material layer. Moreover, even if content of element X becomes larger than 10 mol%, it does not contribute to the improvement of a rust prevention effect. Therefore, the content of the element X is preferably 10 mol% or less with respect to copper in the mixed layer.

  The irreversible capacity of the active material layer may be compensated by depositing lithium on the active material layer and reacting the active material with lithium. A high-capacity electrode can be obtained by compensating the irreversible capacity.

The method for producing a negative electrode for a lithium ion secondary battery according to the present invention includes, for example, a step of forming an intermediate layer containing silicon and oxygen on a current collector containing a metal capable of forming an alloy with silicon, And forming an active material layer. When the composition of the intermediate layer and the composition of the active material layer are different, the boundary between the intermediate layer and the active material layer can be confirmed by analysis. When the composition of the intermediate layer and the composition of the active material layer are the same, it is difficult to clarify the boundary between the intermediate layer and the active material layer. However, the presence of an intermediate layer as a diffusion preventing layer that suppresses diffusion of the constituent elements of the current collector can be confirmed.
For example, in vacuum deposition using silicon as an evaporation source, an intermediate layer and an active material layer containing silicon and oxygen can be formed by flowing a small amount of oxygen into a vacuum chamber. By changing the relationship between the flow rate of oxygen and the deposition rate of silicon, the ratio of silicon to oxygen can be controlled. Similarly, in sputtering, an intermediate layer and an active material layer containing silicon and oxygen can be formed by flowing a small amount of oxygen into the vacuum chamber.

  In the intermediate layer containing silicon and oxygen, since the diffusion of the constituent elements of the current collector hardly occurs, the intermediate layer can be formed at a high temperature. For example, the temperature of the current collector when forming at least one of the intermediate layer and the active material layer can be set to 300 ° C to 700 ° C.

When the temperature of the current collector is less than 300 ° C., although the diffusion of the constituent elements of the current collector can be suppressed, the film formation rate cannot be increased, and thus the manufacturing cost may increase. When the temperature of the current collector exceeds 700 ° C., the current collector is likely to be deformed, and trouble may occur during continuous production.
In the present invention, for example, the film formation rate of the intermediate layer and the active material layer (the increase rate of the thickness of the intermediate layer and the active material layer) can be set to 10 nm to 700 nm or 100 nm to 600 nm per second.

Another manufacturing method of the negative electrode for lithium ion secondary batteries of this invention has the process of vapor-depositing lithium on an active material layer other than the said process.
In the present invention, when lithium is vapor-deposited on the active material layer to compensate for lithium corresponding to the irreversible capacity, lithium can be vapor-deposited at high speed. That is, the temperature of the current collector during vapor deposition can be set to 300 ° C to 700 ° C.

  Another manufacturing method of the negative electrode for lithium ion secondary batteries of this invention has the process of heat-processing a collector, an intermediate | middle layer, and an active material layer simultaneously other than the said process.

  When the intermediate layer and the active material layer are formed, after the film formation, or when lithium is deposited on the active material layer, internal stress may be generated in the active material layer, and the negative electrode may be bent. In this case, internal stress can be relieved by heat-processing a negative electrode at 300 to 700 degreeC. When the heating temperature is less than 300 ° C., the internal stress cannot be relaxed in a short time, so that the production efficiency may be reduced and the manufacturing cost may be increased. When the heating temperature exceeds 700 ° C., the current collector tends to be deformed, which may cause trouble during continuous production.

  The intermediate layer and the active material layer can be formed by various methods. The intermediate layer and the active material layer can be formed by, for example, a vapor deposition method, a sputtering method, a chemical vapor deposition method (CVD method), or the like. In particular, the intermediate layer and the active material layer are preferably formed by vapor deposition or sputtering. As the vapor deposition method, for example, a vacuum heating vapor deposition method, an ion beam vapor deposition method, an electron beam vapor deposition method, or the like can be arbitrarily selected. As the sputtering method, for example, an RF sputtering method can be arbitrarily selected.

Since this invention has the characteristics in the structure of a negative electrode, components other than the negative electrode of a lithium ion secondary battery are not specifically limited.
For the positive electrode active material layer, for example, lithium-containing transition metal oxides such as lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), and lithium manganate (LiMn ₂ O ₄ ) can be used. It is not limited to. As the constituent material of the positive electrode current collector, for example, aluminum, aluminum alloy, nickel, titanium, or the like can be used.

  A positive electrode active material layer may be comprised only with a positive electrode active material, and may be comprised with the positive mix which contains arbitrary components other than a positive electrode active material. Optional components can include a binder, a conductive agent, and the like. Similarly to the negative electrode active material layer, the positive electrode active material layer may be formed of columnar particles.

  As the electrolyte, various lithium ion conductive solid electrolytes and non-aqueous electrolytes can be used. The non-aqueous electrolyte is preferably a lithium salt dissolved in a non-aqueous solvent. The composition of the nonaqueous electrolyte is not particularly limited.

The separator and the outer case are not particularly limited, and materials used in various forms of lithium ion secondary batteries can be used without particular limitation.
EXAMPLES Next, although this invention is demonstrated concretely based on an Example, a following example does not limit this invention.

<< Reference Example 1 >>
A stacked lithium ion secondary battery as shown in FIG. 1 was produced.
(I) Production of positive electrode 10 g of lithium cobaltate (LiCoO ₂ ) powder having an average particle diameter of about 10 μm as a positive electrode active material, 0.3 g of acetylene black as a conductive agent, and polyvinylidene fluoride powder as a binder. 8 g and an appropriate amount of N-methyl-2-pyrrolidone (NMP) were sufficiently mixed to prepare a positive electrode mixture paste. The obtained paste was applied to one side of a positive electrode current collector 11a made of an aluminum foil having a thickness of 20 μm, dried and then rolled to form a positive electrode active material layer 11b. Thereafter, the positive electrode was cut into a predetermined shape. In the obtained positive electrode, the positive electrode active material layer carried on one side of the aluminum foil had a thickness of 70 μm and a size of 30 mm × 30 mm. A lead was connected to the back surface of the current collector without the positive electrode active material layer.

(Ii) Production of negative electrode <Formation of intermediate layer>
The negative electrode 12 was produced using the vapor deposition apparatus 40 (made by ULVAC, Inc.) provided with an electron beam (EB) heating means (not shown) as shown in FIG. The vapor deposition apparatus 40 includes a gas pipe (not shown) for introducing oxygen gas into the vacuum chamber 41 and a nozzle 43. The nozzle 43 was connected to a pipe 44 introduced into the vacuum chamber 41. The pipe 44 was connected to an oxygen cylinder via a mass flow controller. The oxygen cylinder was filled with oxygen gas having a purity of 99.7% (manufactured by Nippon Oxygen Co., Ltd.). Above the nozzle 43, a fixing base 42 for fixing the negative electrode current collector 12a was installed. A target 45 was installed vertically below the fixed base 42. As the target 45, a silicon simple substance (manufactured by Kojundo Chemical Laboratory Co., Ltd.) having a purity of 99.9999% was used.

  An electrolytic copper foil (manufactured by Furukawa Circuit Foil Co., Ltd., surface roughness Rz = 15 μm) having a thickness of 35 μm and cut to a size of 40 mm × 40 mm was fixed to the fixing base 42. The fixing base 42 was installed horizontally such that the angle α with the horizontal plane was 0 °.

The acceleration voltage of the electron beam applied to the silicon target 45 was -8 kV, and the emission was set to 500 mA. The oxygen flow rate was set to 80 sccm with a mass flow controller. After passing through the oxygen atmosphere, the vapor of silicon alone was deposited on the copper foil placed on the fixed base 42 to form the intermediate layer 12b made of a compound containing silicon and oxygen. The deposition time was set to 10 seconds. As a result of quantifying the amount of oxygen contained in the obtained intermediate layer by a combustion method, the composition of the compound containing silicon and oxygen was SiO _0.6 . The film thickness of the intermediate layer was 1 μm.

  Here, the combustion method is a method of quantifying the amount of oxygen contained in a sample by heating the sample with a graphite crucible and measuring the amount of generated CO gas by a non-dispersive infrared absorption method. The determination of oxygen by the combustion method can be performed using an oxygen analyzer (for example, MEGA-620W manufactured by Horiba, Ltd.).

<Formation of active material layer>
Subsequently, the copper foil on which the intermediate layer was formed was placed on the fixed base 42, and the negative electrode active material layer 12c was formed with an oxygen flow rate of 40 sccm and a vapor deposition time of 90 seconds. The thickness of the active material layer was 9 μm. The negative electrode having the intermediate layer and the active material layer thus obtained is defined as a negative electrode 1A.
In this example, after the formation of the intermediate layer, in order to quantify the amount of oxygen, the temperature of the current collector was lowered to room temperature, and the inside of the chamber was returned to normal pressure. As a result, the boundary between the intermediate layer and the active material layer was observed in cross-sectional observation or the like.

<Measurement>
Under the same conditions as above, the amount of oxygen contained in the negative electrode active material layer was quantified by a combustion method using a sample in which only the negative electrode active material layer 12c was formed on the copper foil. The composition was SiO _0.3 .

  The temperature of the current collector during film formation of the intermediate layer and the active material layer was measured with a radiation thermometer, and was found to be 320 ° C., respectively. Since the deposition rate was fast (100 nm / s), the temperature of the current collector naturally reached 320 ° C. without heating. Note that when the temperature of the current collector becomes too high, the current collector may be cooled. Examples of the cooling method include a method in which a copper tube and a fixing base of a current collector are brought into contact with each other, and a coolant is caused to flow in the copper tube. On the other hand, when heating a current collector, for example, a heater is attached to a fixed base and heated.

<Deposition of lithium>
Next, lithium metal was vapor-deposited on the active material layer of the negative electrode 1A using a resistance heating vapor deposition apparatus manufactured by ULVAC. A predetermined amount of lithium metal was loaded into a tantalum boat in the vapor deposition apparatus, and the active material layer of the negative electrode 1A was fixed facing the boat. The electric current value which flows through a boat was set to 50A, and vapor deposition was performed for 10 minutes. By depositing lithium metal by this operation, the intermediate layer and the negative electrode active material layer were supplemented with irreversible lithium stored in the first charge / discharge. Thereafter, the negative electrode 1A was cut into a size of 31 mm × 31 mm. A lead was connected to the back surface of the current collector without the negative electrode active material layer.
It was 350 degreeC as a result of measuring the temperature of the electrical power collector at the time of lithium vapor deposition with the radiation thermometer.

(Iii) Production of test battery The positive electrode active material layer 11b of the positive electrode 11 and the negative electrode active material layer 12c of the negative electrode 12 are opposed to each other through a separator 13 made of a polyethylene microporous film having a thickness of 20 μm manufactured by Asahi Kasei Corporation. A thin electrode group was constructed. This electrode group was inserted into an outer case 14 made of an aluminum laminate sheet together with a non-aqueous electrolyte. As the non-aqueous electrolyte, a solution obtained by dissolving LiPF ₆ at a concentration of 1 mol / L in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 1: 1 was used.

  After impregnating the non-aqueous electrolyte into the positive electrode 11, the negative electrode 12, and the separator 13, the positive electrode lead 15 and the negative electrode lead 16 were led out of the outer case 14. In this state, the end of the outer case 14 was welded while decompressing the inside of the outer case 14 to complete the test battery. The obtained test battery is referred to as battery 1A.

<< Comparative Example 1 >>
A negative electrode was produced in the following manner.
Vapor deposition was performed using the same copper foil and vapor deposition apparatus as in Reference Example 1.
The copper foil was fixed to the fixing base 42, the angle α formed by the fixing base and the horizontal plane was set to 0 °, and the copper foil was installed horizontally. The acceleration voltage of the electron beam applied to the silicon target 45 was -8 kV, and the emission was set to 500 mA. Without introducing oxygen into the vacuum chamber 41, an active material layer made of silicon was formed on the copper foil placed on the fixed base 42. The deposition time was set to 70 seconds. The negative electrode thus obtained is referred to as negative electrode 1B.

The temperature of the current collector during film formation of the active material layer was measured with a radiation thermometer and found to be 330 ° C.
As a result of quantifying the amount of oxygen contained in the obtained active material layer by a combustion method, the oxygen content was 1 mol% or less. The thickness of the active material layer was 7 μm. Lithium was not deposited on the active material layer of the negative electrode 1B.
A test battery 1B was produced in the same manner as in Reference Example 1 except that the negative electrode 1B was used.

[Analysis of negative electrode]
With respect to the intermediate layer and the active material layer of the negative electrode 1A and the active material layer of the negative electrode 1B, analysis in the depth direction was performed by X-ray photoelectron spectroscopy. Here, the relationship between the depth from the predetermined position of the active material layer or the intermediate layer and the element ratio of copper was obtained. Here, the element ratio of copper is the mol% of copper atoms with respect to all atoms detected on the analysis surface. Since the elements detected on the analysis surface are Cu, Si, and O, the element ratio of copper is the number of moles of Cu relative to the total number of moles of Cu, Si, and O, that is, Cu / (Cu + Si + O).

  However, negative electrode 1A ′ and negative electrode 1B ′ were prepared under the same conditions as the respective negative electrodes using rolled copper foil (surface roughness Rz = 0.7 μm or less) having high flatness, and analysis was performed using these. It was. In the following examples, although not specifically described, when performing analysis in the depth direction, a similar electrode is produced again using a current collector made of rolled copper foil, and this is used. Analysis was carried out.

FIG. 6A shows the analysis result of the negative electrode 1A ′, and FIG. 6B shows the analysis result of the negative electrode 1B ′. In FIG. 6A, the horizontal axis of the graph represents the depth from the predetermined position P of the intermediate layer toward the current collector, and the depth of 0 nm corresponds to the predetermined position P. 6B, the horizontal axis of the graph represents the depth of the active material layer from the predetermined position Q in the direction of the current collector, and the depth of 0 μm corresponds to the predetermined position Q.
The vertical axis represents the copper element ratio (Cu / Cu + Si + O). In the negative electrode 1A ′, the copper diffusion width is narrow and changes rapidly, whereas in the negative electrode 1B ′, the copper diffusion width is wide and changes slowly. From this result, it can be seen that in the negative electrode 1B ′ (negative electrode 1B), copper is widely diffused in the active material layer.

In such a measuring method, even when there is actually no diffusion region, the diffusion width as shown in FIG. 6 is measured due to minute unevenness of the current collector and device variations. Therefore, it is unclear whether this diffusion width actually represents the presence of a mixed layer formed by diffusing copper into the intermediate layer. However, relative evaluation is considered possible if the same current collector and the same measuring device are used. Here, the thickness of the mixed layer in which the element ratio of copper is 10 mol% to 90 mol% is defined as “diffusion width”.
In Examples and Comparative Examples, “diffusion width” was determined by X-ray photoelectron spectroscopy unless otherwise specified.
Table 1 summarizes the physical properties of each negative electrode.

[Evaluation method]
The batteries 1A and 1B were each housed in a constant temperature room at 20 ° C., and each battery was charged by a constant current constant voltage method. That is, charging is performed at a constant current of 1C rate (1C is a current value that can use up the entire battery capacity in one hour) until the battery voltage reaches 4.2V, and after reaching 4.2V, the current value becomes 0. The battery was charged at a constant voltage until it reached 05C. After charging, after resting for 20 minutes, discharging was performed at a constant current of 0.2 C until the battery voltage reached 2.5V. After the discharge, it was paused for 20 minutes.
The above charging / discharging was repeated 100 cycles.

The ratio of the discharge capacity at the 100th cycle to the discharge capacity at the beginning of the cycle was determined as a percentage value as a capacity retention rate. The battery 1A and the battery 1B after 100 cycles were disassembled, and the intermediate layer or active material layer of the negative electrode 1A and the negative electrode 1B was observed with a microscope. The results are shown in Table 2.
[Evaluation results]

  As shown in Table 2, the battery 1A was extremely excellent in cycle characteristics as compared with the battery 1B. As a result of disassembling the battery 1A after 100 cycles and observing the negative electrode 1A, the phenomenon that the intermediate layer and the active material layer peel from the copper foil was not observed. On the other hand, as a result of disassembling battery 1B after 100 cycles and observing negative electrode 1B, it was found that a part of the active material layer was peeled from the copper foil.

[Discussion]
In the case of battery 1A, the active material layer was formed at 300 ° C. or higher, but the intermediate layer suppressed the diffusion of copper, which is a constituent element of the current collector, and suppressed the weakening of the interface between the current collector and the intermediate layer. It is thought that it was done. Therefore, even after 100 cycles of charging / discharging, the intermediate layer and the active material layer are not peeled off from the current collector, and it is considered that the current collecting property can be secured and the cycle characteristics are improved. The diffusion width of copper was as very small as 50 nm, but the adhesion strength was sufficiently secured.

  In the battery 1B, since no intermediate layer was present, a large amount of copper diffused into the active material layer, and the copper diffusion width was 2.3 μm. As a result, it is considered that the interface between the current collector and the active material layer is weakened. Therefore, it is considered that when the active material layer expands in the charge / discharge cycle, the active material layer peels off due to stress, the current collection performance decreases, and the cycle characteristics deteriorate.

<< Reference Example 2 >>
The case where the intermediate layer made of Mo was formed was compared with the case where the intermediate layer containing silicon and oxygen was formed. In order to compare the capacity of the negative electrode, a test cell was prepared using lithium metal for the counter electrode.

(I) Production of counter electrode A lithium metal foil having a thickness of 0.3 mm was cut into a 32 mm square, and a lead was connected to the end.

(Ii) Production of Test Battery The negative electrode 1A of Reference Example 1 was used as the negative electrode. Lithium was not deposited on the active material layer.
A counter electrode made of lithium metal foil and the negative electrode active material layer 12c of the negative electrode 12 were opposed to each other through a separator 13 made of a polyethylene microporous film having a thickness of 20 μm manufactured by Asahi Kasei Co., Ltd., thereby forming a thin electrode plate group. This electrode group was inserted into an outer case 14 made of an aluminum laminate sheet together with a non-aqueous electrolyte. As the non-aqueous electrolyte, a solution obtained by dissolving LiPF ₆ at a concentration of 1 mol / L in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 1: 1 was used.

  After impregnating the counter electrode, the negative electrode 12 and the separator 13 with the nonaqueous electrolyte, the counter electrode lead and the negative electrode lead 16 were led out of the outer case 14. In this state, the end of the outer case 14 was welded while decompressing the inside of the outer case 14 to complete the test battery. The obtained test battery is referred to as battery 2A.

<< Comparative Example 2 >>
A negative electrode was produced in the following manner.
First, a molybdenum thin film as an intermediate layer was formed on the same copper foil as in Reference Example 1 using an RF magnetron sputtering apparatus.
As the target, molybdenum having a diameter of 4 inches and a thickness of 5 mm was used. Argon gas was introduced into the vacuum chamber at a flow rate of 100 sccm, and the pressure in the chamber was adjusted to 20 mTorr. The output of the high frequency power supply was set to 100 W, and sputtering was performed for 60 minutes. The resulting molybdenum thin film had a thickness of 1 μm.

Next, using the same vapor deposition apparatus as in Reference Example 1, an active material was deposited on the intermediate layer.
The copper foil having the molybdenum thin film was fixed to the fixing base 42, and the angle α formed by the fixing base and the horizontal plane was set to 0 °, and the copper foil was installed horizontally. The acceleration voltage of the electron beam applied to the silicon target 45 was -8 kV, and the emission was set to 500 mA. The negative electrode active material layer 12c was formed with an oxygen flow rate of 40 sccm and a vapor deposition time of 90 seconds. The negative electrode thus obtained is referred to as negative electrode 2B.
A test battery 2B was produced in the same manner as in Reference Example 2, except that the negative electrode 2B was used. Lithium was not deposited on the active material layer.
Table 3 summarizes the physical properties of the negative electrode 2B.

[Evaluation method]
Batteries 2A and 2B were each housed in a constant temperature room at 20 ° C. and charged at a constant current of 0.2C rate (1C is a current value that can use up the entire battery capacity in 1 hour) until the battery voltage reached 0V. . After resting for 20 minutes, discharging was performed at a constant current of 0.2 C until the battery voltage reached 1.5V. After the discharge, it was paused for 20 minutes.

The above charging / discharging was repeated 30 cycles.
The ratio of the discharge capacity at the 100th cycle to the discharge capacity at the beginning of the cycle was determined as a percentage value as a capacity retention rate. Battery 2A and battery 2B after 100 cycles were disassembled, and the intermediate layer or active material layer of negative electrode 2A and negative electrode 2B was observed with a microscope. The results are shown in Table 4.

  As Table 4 shows, the battery 2A had a larger discharge capacity than the battery 2B. In battery 2A, since the intermediate layer containing silicon and oxygen functions as an active material, the sum of the capacity of the intermediate layer and the capacity of the active material layer was obtained. The reason why the capacity of the battery 2B is small is that Mo in the intermediate layer does not form an alloy with lithium (the intermediate layer does not contribute to the capacity). The capacity retention rate results and the negative electrode overview were similar for these batteries.

<< Reference Example 3 >>
When the intermediate layer containing silicon and oxygen is represented by SiO _x , the range of the x value was examined.
When forming the intermediate layer, the following negative electrodes 3A to 3E were produced in the same manner as in Reference Example 1 except that the oxygen flow rate was changed and the deposition time was changed. Further, test batteries 3A to 3E were produced in the same manner as in Reference Example 1 except that the negative electrodes 3A to 3E were used. Note that the temperature of the current collector during film formation was 320 ° C. in all cases. Lithium was deposited on the active material layer in the same manner as in Reference Example 1.

<I> Negative electrode 3A
A negative electrode 3A was produced in the same manner as in Reference Example 1, except that in the formation of the intermediate layer, the oxygen flow rate was set to 5 sccm and the deposition time was set to 20 seconds. A test battery 3A was produced in the same manner as in Reference Example 1 using the negative electrode 3A.

<Ii> Negative electrode 3B
A negative electrode 3B was produced in the same manner as in Reference Example 1 except that the intermediate layer was deposited by setting the oxygen flow rate to 10 sccm. A test battery 3B was produced in the same manner as in Reference Example 1 using the negative electrode 3B.

<Iii> Negative electrode 3C
A negative electrode 3C was produced in the same manner as in Reference Example 1 except that the intermediate layer was deposited by setting the oxygen flow rate to 40 sccm. A test battery 3C was produced in the same manner as in Reference Example 1 using the negative electrode 3C.

<Iv> Negative electrode 3D
A negative electrode 3D was produced in the same manner as in Reference Example 1 except that the intermediate layer was deposited by setting the oxygen flow rate to 130 sccm. A test battery 3D was produced in the same manner as in Reference Example 1 using the negative electrode 3D.

<V> Negative electrode 3E
A negative electrode 3E was produced in the same manner as in Reference Example 1 except that the intermediate layer was deposited by setting the oxygen flow rate to 240 sccm. A test battery 3E was produced in the same manner as in Reference Example 1 using the negative electrode 3E.

<Vi> Negative electrode 3F
A negative electrode 3F was produced in the same manner as in Reference Example 1 except that SiO ₂ was used as a target and the oxygen flow rate was set to 100 sccm in the formation of the intermediate layer. A test battery 3F was produced in the same manner as in Reference Example 1 using the negative electrode 3F.
The physical properties of the negative electrodes 3A to 3F are summarized in Table 5.

  For the batteries 3A to 3F, the capacity retention rate was measured in the same manner as described above. The negative electrodes 3A to 3F after 100 cycles were observed in the same manner as described above. The results are shown in Table 6.

As shown in Table 6, the battery 3A in which the composition of the intermediate layer was SiO _0.05 was slightly inferior in cycle characteristics. Further, since the oxygen ratio in the intermediate layer was small, the diffusion width of copper was 1 μm or more. In battery 3A, since a relatively large amount of copper diffused, it is considered that the interface between copper and the intermediate layer was weakened. On the other hand, the batteries 3B to 3E exhibited good cycle characteristics, and no peeling of the active material layer was observed. In particular, in the batteries 3D to 3E in which the x value of the intermediate layer was larger than the x value of the active material layer, it was considered that peeling of the active material layer was effectively suppressed, and the cycle characteristics were good. Battery 3F was not charged or discharged at all. This is considered because SiO ₂ is an insulator.

<< Reference Example 4 >>
The temperature of the current collector when forming the intermediate layer and the active material layer was examined.
The intermediate layer and the active material layer were formed using the same vapor deposition apparatus as in Reference Example 1.
A heating unit and a cooling unit (not shown) for controlling the temperature are provided on the substrate of the fixed base 42 in FIG. 5, and the substrate temperature is changed from room temperature to 800 ° C. as in Reference Example 1. The following negative electrodes 4A to 4D were prepared. Further, test batteries 4A to 4D were produced in the same manner as in Reference Example 1 except that the negative electrodes 4A to 4D were used. Note that lithium was deposited on the active material layer in the same manner as in Reference Example 1.

<I> Negative electrode 4A
In forming the intermediate layer, the substrate temperature was set to 200 ° C., the electron beam emission was set to 100 mA, the deposition time was set to 200 seconds, and the oxygen flow rate was set to 4 sccm. Further, in the formation of the active material layer, the substrate temperature was set to 200 ° C., the electron beam emission was set to 100 mA, the deposition time was set to 30 minutes, and the oxygen flow rate was set to 2 sccm. A negative electrode 4A was produced in the same manner as in Reference Example 1 except for these conditions. A test battery 4A was produced in the same manner as in Reference Example 1 using the negative electrode 4A. Note that the substrate temperature can be considered to be the same as the temperature of the current collector. The same applies hereinafter.

<Ii> Negative electrode 4B
In forming the intermediate layer, the substrate temperature was set to 300 ° C., the electron beam emission was set to 250 mA, the deposition time was set to 10 seconds, and the oxygen flow rate was set to 8 sccm. Further, in forming the active material layer, the substrate temperature was set to 300 ° C., the electron beam emission was set to 250 mA, the deposition time was set to 15 minutes, and the oxygen flow rate was set to 4 sccm. A negative electrode 4B was produced in the same manner as in Reference Example 1 except for these conditions. A test battery 4B was produced in the same manner as in Reference Example 1 using the negative electrode 4B.

<Iii> Negative electrode 4C
In forming the intermediate layer, the substrate temperature was set to 700 ° C., the electron beam emission was set to 600 mA, the deposition time was set to 1.4 seconds, and the oxygen flow rate was set to 500 sccm. Further, in forming the active material layer, the substrate temperature was set to 700 ° C., the electron beam emission was set to 600 mA, the deposition time was set to 13 seconds, and the oxygen flow rate was set to 280 sccm. A negative electrode 4C was produced in the same manner as in Reference Example 1 except for these conditions. A test battery 4C was produced in the same manner as in Reference Example 1 using the negative electrode 4C.

<Iv> Negative electrode 4D
In forming the intermediate layer, the substrate temperature was set to 750 ° C., the electron beam emission was set to 650 mA, the deposition time was set to 1.3 seconds, and the oxygen flow rate was set to 530 sccm. Further, in forming the active material layer, the substrate temperature was set to 750 ° C., the electron beam emission was set to 650 mA, the deposition time was set to 12 seconds, and the oxygen flow rate was set to 320 sccm. A negative electrode 4D was produced in the same manner as in Reference Example 1 except for these conditions. A test battery 4D was produced in the same manner as in Reference Example 1 using the negative electrode 4D.
The physical properties of the negative electrodes 4A to 4D are summarized in Table 7.

  For the batteries 4A to 4D, the capacity retention rate was measured in the same manner as described above. The negative electrodes 4A to 4D after 100 cycles were observed in the same manner as described above. The results are shown in Table 8.

  As shown in Table 8, the battery 4D was slightly inferior in cycle characteristics as compared with the batteries 4A to 4C, and peeling was observed in a part of the active material layer. The diffusion width of copper was 1 μm or more. In the battery 4D, since a relatively large amount of copper diffused, the interface between the copper and the intermediate layer was weakened, and a part of the active material layer was peeled off, so that the conductivity was lowered. On the other hand, batteries 4A to 4C have good cycle characteristics.

  However, in the case of the battery 4A, in order to control the substrate temperature to 200 ° C., considering the cooling rate of the substrate, it is necessary to reduce the electron beam emission and decrease the film formation rate. Therefore, the film formation of the battery 4A required more than five times as long as the batteries 4B and 4C. Thus, productivity is lowered when the substrate temperature is low. In order to increase productivity, it is preferable to set the substrate temperature to 300 ° C. or higher. On the other hand, when the substrate temperature is higher than 700 ° C., the deposition rate is increased, but the diffusion of copper is slightly increased. Therefore, the substrate temperature at the time of forming the intermediate layer and the active material layer is appropriately 300 ° C. or higher and 700 ° C. or lower. In the case of this substrate temperature range, the deposition rate is 10 nm to 700 nm.

<< Reference Example 5 >>
When heat treatment was performed after the active material layer was formed, an appropriate temperature range for heat treatment was examined.
After the formation of the active material layer, negative electrodes 5A to 5E were fabricated in the same manner as in Reference Example 1 except that heat treatment was performed at various temperatures before lithium was deposited. Such heat treatment may be performed to remove moisture attached to the electrode plate or to remove residual stress generated between the current collector and the active material layer.
Further, when the irreversible capacity at the first charge / discharge is eliminated by evaporating lithium on the active material layer, the substrate temperature may increase due to the solidification heat of lithium or the radiant heat of the apparatus. That is, since the substrate temperature rises in the same manner as in the heat treatment, the suitable temperature range when depositing lithium greatly affects the manufacturing process.
The heat treatment after vapor deposition of lithium is performed in order to homogenize the reaction between lithium and the active material layer or to remove the residual stress of the active material layer that has slightly expanded.
In this reference example, heat treatment was performed before lithium deposition. However, when the substrate temperature is raised during lithium deposition or when heat treatment is performed after lithium deposition, copper diffusion is similarly performed. Can be prevented.

<I> Negative electrode 5A
A negative electrode 1A produced in the same manner as in Reference Example 1 was housed in a quartz pipe installed in a tubular furnace, and heat-treated at 200 ° C. for 10 minutes while flowing argon at a flow rate of 1000 sccm. The negative electrode thus obtained is referred to as negative electrode 5A. A test battery 5A was produced in the same manner as in Example 1 using the negative electrode 5A.

<Ii> Negative electrode 5B
A negative electrode 1A produced in the same manner as in Reference Example 1 was accommodated in a quartz pipe installed in a tubular furnace, and heat-treated at 300 ° C. for 10 minutes while flowing argon at a flow rate of 1000 sccm. The negative electrode thus obtained is referred to as negative electrode 5B. A test battery 5B was produced in the same manner as in Reference Example 1 using the negative electrode 5B.

<Iii> Negative electrode 5C
A negative electrode 1A produced in the same manner as in Reference Example 1 was accommodated in a quartz pipe installed in a tubular furnace, and heat-treated at 700 ° C. for 10 minutes while flowing argon at a flow rate of 1000 sccm. The negative electrode thus obtained is referred to as negative electrode 5C. A test battery 5C was produced in the same manner as in Reference Example 1 using the negative electrode 5C.

<Iv> Negative electrode 5D
A negative electrode 1A produced in the same manner as in Reference Example 1 was housed in a quartz pipe installed in a tubular furnace, and heat-treated at 800 ° C. for 10 minutes while flowing argon at a flow rate of 1000 sccm. The negative electrode thus obtained is referred to as negative electrode 5D. A test battery 5D was produced in the same manner as in Reference Example 1 using the negative electrode 5D.

  Negative electrodes 5A to 5D were placed on a flat surface, and the maximum curved height was measured using a height gauge. The maximum height obtained was defined as the amount of warpage. The amount of warpage is an index of internal stress. Table 9 summarizes the physical properties of the negative electrodes 5A to 5D.

  For the batteries 5A to 5D, the capacity retention rate was measured in the same manner as described above. The negative electrodes 4A to 4F after 100 cycles were observed in the same manner as described above. The results are shown in Table 10.

  As Table 10 shows, the battery 5D was slightly inferior in cycle characteristics as compared with the batteries 5A to 5C, and peeling was observed in a part of the active material layer. The diffusion width of copper was 1 μm or more. In the battery 5D, since a relatively large amount of copper diffused, the interface between the copper and the intermediate layer was weakened, and a part of the active material layer was peeled off. On the other hand, the batteries 5A to 5C exhibited good cycle characteristics.

  As Table 9 shows, the negative electrode 5A had a large amount of warpage. This is presumably because the heat treatment temperature is low and the residual stress is not removed. The amount of warpage of the negative electrode 5D is the largest value, which is considered to be caused by the fact that the heat treatment temperature is high, the copper substrate is softened and unnecessarily stretched. From the above results, the heat treatment temperature is suitably 300 ° C. or higher and 700 ° C. or lower.

<< Reference Example 6 >>
The thickness of the intermediate layer suitable for suppressing the diffusion of the constituent elements of the current collector was investigated.
The intermediate layer was formed by changing the electron beam emission, changing the oxygen flow rate, and changing the deposition time. As the active material layer, a layer made of silicon was formed so that copper was easily diffused. Except for these conditions, negative electrodes 6A to 6D were produced in the same manner as in Reference Example 1. Lithium was deposited on the active material layer in the same manner as in Reference Example 1.

<I> Negative electrode 6A
In forming the intermediate layer, the film was formed by setting the electron beam emission to 100 mA, the oxygen flow rate to 5 sccm, and the deposition time to 10 seconds. The active material layer was formed without introducing oxygen. The substrate (current collector) temperature during the formation of the intermediate layer and the active material layer was 200 ° C., respectively. Other conditions were the same as in Reference Example 1 to produce a negative electrode. The obtained negative electrode was accommodated in a quartz pipe installed in a tubular furnace, and heat-treated at 500 ° C. for 10 minutes while flowing argon at a flow rate of 1000 sccm. The negative electrode thus obtained is referred to as negative electrode 6A. A test battery 6A was produced in the same manner as in Reference Example 1 using the negative electrode 6A.

<Ii> Negative electrode 6B
In the formation of the intermediate layer, the film was formed with an electron beam emission of 100 mA, an oxygen flow rate of 5 sccm, and a deposition time of 20 seconds. The temperature of the current collector when forming the intermediate layer was 200 ° C. The active material layer was formed without introducing oxygen. Other conditions were the same as in Reference Example 1 to produce a negative electrode. The obtained negative electrode was accommodated in a quartz pipe installed in a tubular furnace, and heat-treated at 500 ° C. for 10 minutes while flowing argon at a flow rate of 1000 sccm. The negative electrode thus obtained is referred to as negative electrode 6B. A test battery 6B was produced in the same manner as in Reference Example 1 using the negative electrode 6B.

<Iii> Negative electrode 6C
In the formation of the intermediate layer, the film was formed with an electron beam emission of 100 mA, an oxygen flow rate of 5 sccm, and a deposition time of 100 seconds. The temperature of the current collector when forming the intermediate layer was 200 ° C. The active material layer was formed without introducing oxygen. Other conditions were the same as in Reference Example 1 to produce a negative electrode. The obtained negative electrode was accommodated in a quartz pipe installed in a tubular furnace, and heat-treated at 500 ° C. for 10 minutes while flowing argon at a flow rate of 1000 sccm. The negative electrode thus obtained is referred to as negative electrode 6C. A test battery 6C was produced in the same manner as in Reference Example 1 using the negative electrode 6C.
Table 11 summarizes the physical properties of the negative electrodes 6A to 6C.

  As Table 11 shows, the negative electrode 6A had a larger diffusion width than the negative electrodes 6B to 6C. This is presumably because the intermediate layer is somewhat thin and does not cover the entire surface of the current collector. The negative electrodes 6B to 6C had a diffusion width equivalent to that in Example 1. These results indicate that the thickness of the intermediate layer is preferably 100 nm or more. However, even if the thickness of the intermediate layer is less than 100 nm, the diffusion of copper is suppressed when the flatness of the surface of the current collector is high or when a dense intermediate layer is formed.

Example 7
Various active materials were examined. Lithium was deposited on the active material layer in the same manner as in Reference Example 1. <I> Negative electrode 7A
In the formation of the negative electrode active material, the target 45 was divided into two, one side using Si granular material manufactured by Kojundo Chemical Laboratory Co., Ltd. and the other using Ti granular material manufactured by Kojundo Chemical Laboratory. The flow rate of oxygen was set to 0 sccm, and the electron beam emission was set to 300 mA. The electron beam was alternately irradiated onto the Si granular material and the Ti granular material, and vapor deposition was performed for 7 minutes while being separately dissolved. Otherwise, the negative electrode 7A was produced in the same manner as in Reference Example 1. As a result of quantifying the obtained active material layer by fluorescent X-ray spectroscopy, the composition of the active material (alloy) was SiTi _0.2 . A test battery 7A was produced in the same manner as in Reference Example 1 using the negative electrode 7A. The substrate (current collector) temperature during the formation of the active material layer was 300 ° C.

<Ii> Negative electrode 7B
In the formation of the negative electrode active material, a silicon crystal manufactured by Kojundo Chemical Laboratory Co., Ltd. was used as the target 45, nitrogen was introduced into the chamber instead of oxygen, and the acceleration voltage of the electron beam irradiated onto the target 45 was − A negative electrode 7B was produced in the same manner as in Reference Example 1, except that the deposition was performed at 8 kV, the emission was set at 300 mA, and the deposition time was set at 7 minutes. The substrate (current collector) temperature during the formation of the active material layer was 300 ° C.
Nitrogen gas with a purity of 99.7% (manufactured by Nippon Oxygen Co., Ltd.) was used as the nitrogen gas, and the flow rate of nitrogen was set to 20 sccm. Further, an EB irradiation device was installed in the vicinity of the nozzle 43, and the acceleration voltage was set to −4 kV and the emission was set to 20 mA to convert the nitrogen gas into plasma.
As a result of quantifying the obtained active material layer by fluorescent X-ray spectroscopy, the composition of the active material (compound containing silicon and nitrogen) was SiN _0.2 .
A test battery 7B was produced in the same manner as in Reference Example 1 using the negative electrode 7B.
The physical properties of the negative electrodes 7A and 7B are summarized in Table 12.

  For the batteries 7A to 7B, the capacity retention rate was measured in the same manner as described above. The negative electrodes 7A to 7B after 100 cycles were observed in the same manner as described above. The results are shown in Table 13.

  As Table 13 shows, the batteries 7A to 7B exhibited good cycle characteristics. It is considered that the diffusion of copper was suppressed by the action of the intermediate layer, and the interface between the copper foil and the intermediate layer was not weakened. From the result of the battery 7A, it was found that the effect of the present invention can be obtained even when an alloy containing silicon and titanium is used as the active material. From the result of the battery 7B, it was found that the effect of the present invention can be obtained even when a compound containing silicon and nitrogen is used as the active material.

<< Reference Example 8 >>
An intermediate layer and an active material layer including a plurality of columnar particles were formed on the surface of the roughened copper foil. The columnar particles were inclined with respect to the normal direction of the surface of the current collector. Lithium was deposited on the active material layer in the same manner as in Reference Example 1.

<I> Negative electrode 8A
An electrolytic copper foil (manufactured by Furukawa Circuit Foil Co., Ltd.) having a thickness of 12 μm and a surface roughness Rz of 10 μm was cut into a size of 40 mm × 40 mm and used as a current collector. In the formation of the intermediate layer, the angle α formed by the fixing base 42 and the horizontal plane was set to 63 °, the oxygen flow rate was set to 30 sccm, and the deposition time was set to 30 seconds. In the formation of the active material layer, the angle α formed by the fixing base 42 and the horizontal plane was set to 63 °, the oxygen flow rate was set to 15 sccm, and the deposition time was set to 8 minutes. A negative electrode 8A was produced in the same manner as in Reference Example 1 except for these conditions. The substrate (current collector) temperature during the formation of the intermediate layer and the active material layer was 320 ° C., respectively.
A test battery 8A was produced in the same manner as in Reference Example 1 using the negative electrode 8A.
Table 14 summarizes the physical properties of the negative electrode 8A.

  In the negative electrode 8A, the intermediate layer and the active material layer are composed of columnar particles grown in an oblique direction. For the battery 8A, the capacity retention rate was measured in the same manner as described above. The negative electrode 8A after 100 cycles was observed in the same manner as described above. The results are shown in Table 15.

  As Table 15 shows, the battery 8A had good cycle characteristics. Thus, it has been found that the effects of the present invention can be obtained even when the intermediate layer and the active material layer are not uniform films but are composed of a plurality of columnar particles.

Example 1
For the negative electrode 1A, a more detailed analysis of the copper diffusion width and the copper diffusion region was performed.
Specifically, analysis by transmission electron microscope (TEM), X-ray microanalyzer (EPMA) and electron diffraction was performed on the interface between the intermediate layer of negative electrode 1A and the copper foil. A negative electrode 1A processed to a size of 10 μm × 10 μm × 0.1 μm was used as a sample for TEM observation. For TEM analysis and EPMA analysis, JEM-4000EX manufactured by JEOL Ltd. was used, and the acceleration voltage was set to 400 kV.

FIG. 7A is a TEM photograph observing the interface between the copper foil and the intermediate layer included in the negative electrode 1A. In FIG. 7A, the bright part is an intermediate layer and the dark part is a copper foil. It can be seen that the boundary between the bright part and the dark part is the interface, and the intermediate layer and the copper foil are clearly separated.
FIG. 7B shows the result of elemental analysis measured along the line shown in FIG. 7A. The copper diffusion width determined from the copper element ratio was about 10 nm.

FIG. 7C shows the result of electron beam diffraction analysis in the region surrounded by the circle shown in FIG. 7A. From the X-ray diffraction standard data (JCPDS), the spots in the figure agreed with the copper values. No diffraction spots other than these spots were observed, and no diffraction spots attributed to SiO _{0.6 as the} intermediate layer were observed. This is presumably because SiO _0.6 is amorphous.

  From the above measurement results, it was found that the copper diffusion width was 10 nm or less. Moreover, it is thought that the alloy of the element contained in an intermediate | middle layer and copper is not formed in the interface of copper and an intermediate | middle layer. In addition, since analysis in a micro area | region is possible in TEM rather than ESCA, the value of the copper diffusion width was different in ESCA analysis and TEM analysis. This is presumably because the copper diffusion width obtained by ESCA analysis includes an error due to argon sputtering and an error due to irregularities on the current collector surface.

<< Comparative Example 2 >>
The negative electrode 9A was produced in the following manner, and the diffusion width of copper and the detailed analysis of the region where copper was diffused were performed in the same manner as in Experimental Example 1.
On the same copper foil as in Reference Example 1, an Si thin film was formed as an intermediate layer using an RF magnetron sputtering apparatus. As a target, a silicon simple substance having a diameter of 4 inches and a thickness of 5 mm was used. Argon gas was introduced into the vacuum chamber at a flow rate of 100 sccm, and the pressure in the chamber was adjusted to 20 mTorr. The output of the high frequency power source was set to 100 W, and sputtering was performed for 3 minutes. The thickness of the obtained intermediate layer (Si thin film) was 50 nm. The substrate temperature was 150 ° C.

Using the same vapor deposition apparatus as in Reference Example 1, an active material was deposited on the intermediate layer.
The copper foil having the Si thin film was fixed to the fixing base 42, the angle α formed by the fixing base and the horizontal plane was set to 0 °, and the copper foil was installed horizontally. The acceleration voltage of the electron beam applied to the silicon target 45 was -8 kV, and the emission was set to 500 mA. The negative electrode active material layer 12c was formed with an oxygen flow rate of 40 sccm and a vapor deposition time of 90 seconds. The negative electrode thus obtained was designated as negative electrode 9A.

FIG. 8A is a TEM photograph observing the interface between the copper foil and the intermediate layer included in the negative electrode 9A. In FIG. 8A, the bright portion is an intermediate layer, and it has been found that an A layer and a B layer different from each other exist between the intermediate layer and the copper foil.
FIG. 8B shows the elemental analysis results measured along the line shown in FIG. 8A. From the result of measurement by EPMA shown in FIG. 8B, it was found that the A layer and the B layer were formed of copper and Si. The A layer is a layer in which copper is diffused into the intermediate layer (Si thin film), and the B layer is a layer in which the Si in the intermediate layer is diffused into the copper foil.

FIG. 8C shows the result of electron beam diffraction analysis performed in the region surrounded by the circle shown in FIG. 8A. From the standard data of X-ray diffraction (JCPDS), the three spots in the figure agreed with the value of Cu ₃ Si. Therefore, it was found that the A layer and the B layer are layers containing at least Cu ₃ Si. It was also found that copper was not diffused in SiO _0.3 .
From the above results, it was found that when the Si thin film and the copper foil are in contact, copper is easily diffused from the copper foil to the Si thin film, and Si is easily diffused from the Si thin film to the copper foil. It was also found that an alloy such as Cu ₃ Si exists in the layer formed by such diffusion.

Example 1
An active material layer having columnar particles including a plurality of columnar portions was studied. Lithium was deposited on the active material layer in the same manner as in Reference Example 1.
<I> Negative electrode 10A
A copper foil having an intermediate layer formed thereon was placed on the fixed base 42 as in Reference Example 8. The fixed base 42 was inclined so that the angle α with the horizontal plane was 60 °. The acceleration voltage of the electron beam applied to the silicon target 45 was -8 kV, and the emission was set to 500 mA. The oxygen flow rate was set at 80 sccm. In this state, vapor deposition was performed for 1 minute to form a first grain layer.
Next, the fixing base 42 is inclined so that the angle with the horizontal plane forms 120 ° (180 ° −α), and the oxygen flow rate is set to 67 sccm. Then, a second stage grain layer was formed. Thereafter, the angle α of the fixing base was alternately changed to 60 ° or 120 °, and the above operation was repeated to form a negative electrode active material layer including a laminate of eight-stage grain layers as shown in FIG.
A negative electrode 10A was produced in the same manner as in Reference Example 1 except that the active material layer was formed as described above. The thickness of the active material layer (total thickness of the particle layers) was 16 μm.

A test battery 10A was produced in the same manner as in Example 1 using the negative electrode 10A. As a result of quantifying the amount of oxygen contained in the obtained negative electrode active material layer by a combustion method, the composition of the compound containing silicon and oxygen was SiO _0.5 . Table 16 shows the physical properties of the negative electrode 10A.

  For the battery 10A, the capacity retention rate was measured in the same manner as described above. The negative electrode 10A after 100 cycles was observed in the same manner as described above. The results are shown in Table 17.

As described above, even when columnar particles including a laminate of a plurality of particle layers inclined in different directions were formed, generation of wrinkles was suppressed as in Reference Example 8, and excellent cycle characteristics were obtained. . It is considered that because the columnar particles include a plurality of particle layers, a space can be formed around the columnar particles, and stress due to expansion of the active material can be relieved. Moreover, since it was possible to suppress collision between adjacent columnar particles, it is considered that excellent cycle characteristics were obtained. Further, by using the above-described forming method, columnar particles apparently parallel to the normal direction of the current collector can be obtained. Such columnar particles can suppress the interface stress generated during expansion more than the inclined columnar particles. Therefore, it is considered that the generation of wrinkles was suppressed even when the active material layer was thick.

  The present invention can be applied to various forms of lithium ion secondary batteries, and is particularly useful in lithium ion secondary batteries that require high capacity and good cycle characteristics. The shape of the lithium ion secondary battery to which the present invention is applicable is not particularly limited, and may be any shape such as a coin shape, a button shape, a sheet shape, a cylindrical shape, a flat shape, and a square shape. The form of the electrode plate group composed of the positive electrode, the negative electrode, and the separator may be a wound type or a laminated type. The size of the battery may be small for a small portable device or large for an electric vehicle. The lithium ion secondary battery of the present invention can be used for a power source of, for example, a portable information terminal, a portable electronic device, a small electric power storage device for home use, a motorcycle, an electric vehicle, a hybrid electric vehicle, etc., but the application is not particularly limited. .

It is a longitudinal cross-sectional view of an example of a laminated type lithium ion secondary battery. It is a schematic sectional drawing which shows the structure of the negative electrode for lithium ion secondary batteries of this invention. It is a schematic sectional drawing which shows the structure of the active material layer of the negative electrode for lithium ion secondary batteries of this invention. It is a schematic sectional drawing of the columnar particle | grains containing the laminated body of the some columnar part inclined with respect to the normal line direction of the surface of an electrical power collector. It is the schematic of an example of the manufacturing apparatus of the negative electrode for lithium ion secondary batteries of this invention. It is the result of having analyzed the negative electrode for lithium ion secondary batteries which concerns on the Example of this invention by the X ray photoelectron spectroscopy. It is the result of having analyzed the negative electrode for lithium ion secondary batteries which concerns on the comparative example of this invention by the X-ray photoelectron spectroscopy. It is a TEM photograph of the interface of the copper foil which concerns on Example 1 of this invention, and an intermediate | middle layer. It is the elemental analysis result measured along the line in FIG. 7A. It is an electron beam diffraction image of the area | region enclosed with the circle | round | yen in FIG. 7A. It is a TEM photograph of the interface of the copper foil which concerns on the comparative example 2 of this invention, and an intermediate | middle layer. It is the elemental analysis result measured along the line in FIG. 8A. It is an electron beam diffraction image of the area | region enclosed with the circle | round | yen in FIG. 8A.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Battery 11 Positive electrode 11a Positive electrode collector 11b Positive electrode active material layer 12 Negative electrode 12a Negative electrode collector 12b Negative electrode intermediate layer 12c Negative electrode active material layer 13 Separator 14 Outer case 30 Columnar particle 31 Upper columnar particle 32 Lower columnar particle 40 Deposition apparatus 41 Chamber 42 Fixed base 43 Nozzle 44 Piping 45 Target 101-108 Columnar part

Claims (16)

A current collector, an intermediate layer formed on the surface of the current collector, and an active material layer formed as an extension of the intermediate layer,
The current collector includes a metal capable of forming an alloy with silicon,
The active material layer includes an active material containing silicon,
The intermediate layer includes silicon and oxygen,
The intermediate layer suppresses diffusion of a metal capable of forming an alloy with the silicon into the active material layer ,
In the active material layer, the active material forms a plurality of columnar particles,
The negative electrode for a lithium ion secondary battery , wherein the columnar particles include a laminate of a plurality of grain layers grown with an inclination with respect to the normal direction of the surface of the current collector . The negative electrode for a lithium ion secondary battery according to claim 1, wherein the intermediate layer contains SiO _x (0.1 ≦ x <2).   The negative electrode for a lithium ion secondary battery according to claim 1, wherein the active material layer further contains oxygen, nitrogen, or titanium.   The negative electrode for a lithium ion secondary battery according to any one of claims 1 to 3, wherein the metal capable of forming an alloy with silicon is copper or nickel.   The metal capable of forming an alloy with silicon diffuses into the intermediate layer to form a mixed layer, and the thickness of the mixed layer is 1 μm or less. Negative electrode for secondary battery. The columnar particles are inclined relative to the direction normal to the surface of the current collector, the negative electrode for a lithium ion secondary battery according to any one of claims 1-5. The plurality of grain layers are grown in different directions, the negative electrode for a lithium ion secondary battery of claim 1, wherein. The active thickness of the material layer is approximately 0.1-100 [mu] m, the negative electrode for a lithium ion secondary battery according to any one of claims 1-7. The thickness of the current collector is a 1 m to 50 m, a negative electrode for a lithium ion secondary battery according to any one of claims 1-8. The negative electrode for a lithium ion secondary battery according to any one of claims 1 to 9 , wherein a surface roughness Rz of the current collector carrying the intermediate layer is 0.1 µm to 100 µm. Wherein the current collector surface carrying the intermediate layer has irregularities formed in a regular pattern, the negative electrode for a lithium ion secondary battery according to any one of claims 1-10.   The mixed layer includes at least one element X selected from the group consisting of chromium, carbon, and hydrogen and copper, and the content of the element X is 10 mol% with respect to copper in the mixed layer. The negative electrode for a lithium ion secondary battery according to claim 5, wherein: The active material layer by depositing lithium on the active material and lithium were reacted, according to claim 1 to 12 negative electrode for a lithium ion secondary battery according to any one of. The intermediate layer is made of SiO. _x1 (0.1 ≦ x1 <2),
  The active material layer is made of SiO. _x2 (0.01 ≦ x2 ≦ 1),
The negative electrode for a lithium ion secondary battery according to claim 1, wherein 1 <x1 / x2 ≦ 10. The negative electrode for a lithium ion secondary battery according to claim 14, wherein 2 ≦ x1 / x2 ≦ 10.   A lithium ion secondary battery comprising a positive electrode, a negative electrode according to any one of claims 1 to 15, a separator disposed between the positive electrode and the negative electrode, and an electrolyte.