WO2019123951A1

WO2019123951A1 - Lithium-ion secondary cell

Info

Publication number: WO2019123951A1
Application number: PCT/JP2018/042840
Authority: WO
Inventors: 晴章内田; 坂脇　彰; 安田　剛規
Original assignee: 昭和電工株式会社
Priority date: 2017-12-22
Filing date: 2018-11-20
Publication date: 2019-06-27

Abstract

This lithium-ion secondary cell 1 is configured by stacking, in the stated order: a positive electrode layer 30 containing a positive electrode active material; a solid electrolyte layer 40 containing an inorganic solid electrolyte; a holding layer 50 configured from platinum (Pt) that has been made porous, the holding layer 50 holding lithium; a coating layer 60 configured from an amorphous metal or alloy; and a negative electrode collector layer 70 configured from platinum (Pt). This inhibits leakage of lithium in an all-solid lithium-ion secondary cell to the exterior.

Description

Lithium ion secondary battery

The present invention relates to a lithium ion secondary battery.

With the spread of mobile electronic devices such as mobile phones and notebook computers, there is a strong demand for the development of small and lightweight secondary batteries having high energy density. A lithium ion secondary battery is known as a secondary battery satisfying such a demand. The lithium ion secondary battery has a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and an electrolyte that exhibits lithium ion conductivity and is disposed between the positive electrode and the negative electrode.

In a conventional lithium ion secondary battery, an organic electrolytic solution or the like has been used as an electrolyte. On the other hand, while using a solid electrolyte (inorganic solid electrolyte) made of an inorganic material as the electrolyte, in order to suppress the diffusion of lithium to the negative electrode current collector provided on the negative electrode side, the negative electrode current collector It has been proposed to provide a block region containing an active material (see Patent Document 1).

JP, 2013-164971, A

However, even in the case of adopting a method of providing a block region containing a positive electrode active material in the negative electrode current collector, lithium that has passed through the block region sometimes leaks out of the lithium ion secondary battery .
An object of the present invention is to suppress the leakage of lithium to the outside in an all solid lithium ion secondary battery.

The lithium ion secondary battery of the present invention is not composed of a metal or alloy having a solid structure containing an inorganic solid electrolyte exhibiting lithium ion conductivity, a holding layer capable of holding lithium, and an amorphous structure. And an amorphous metal layer in order.
In such a lithium ion secondary battery, the amorphous metal layer may be characterized by containing chromium (Cr).
The amorphous metal layer may be made of an alloy of chromium (Cr) and titanium (Ti).
The amorphous metal layer may be characterized by being made of a metal or an alloy which does not form an intermetallic compound with lithium.
Further, the amorphous metal layer is characterized in that it is made of any of ZrCuAlNiPdP, CuZr, FeZr, TiZr, CoZrNb, NiNb, NiTiNb, NiP, CuP, NiPCu, NiTi, CrTi, AlTi, FeSiB, AuSi. can do.
The holding layer may be characterized by being made of a platinum group element (Ru, Rh, Pd, Os, Ir, Pt) having a porous structure, gold (Au), or an alloy thereof.
Further, the holding layer can be characterized by being made of titanium having a plurality of columnar crystals each extending in the thickness direction.
Further, the holding layer can be characterized by containing a negative electrode active material.
Further, the holding layer can be characterized by containing a positive electrode active material.
Further, a positive electrode layer containing a positive electrode active material is provided on the side opposite to the holding layer of the solid electrolyte layer, and the size of the plane of the holding layer is larger than the size of the plane of the positive electrode layer. can do.
In addition, it is characterized by further comprising a noble metal layer composed of a platinum group element (Ru, Rh, Pd, Os, Ir, Pt) or gold (Au) or an alloy thereof, and laminated on the amorphous metal layer. can do.

According to the present invention, it is possible to suppress the leakage of lithium in the all solid lithium ion secondary battery to the outside.

FIG. 1 is a view showing a cross-sectional configuration of a lithium ion secondary battery of Embodiment 1; 3 is a flowchart for illustrating a method of manufacturing the lithium ion secondary battery of Embodiment 1. FIG. 2 is a diagram showing a cross-sectional configuration of a lithium ion secondary battery after film formation and before initial charge according to Embodiment 1. (A) to (c) are diagrams for explaining the procedure for making the holding layer porous. (A) is a cross section STEM photograph of the lithium ion secondary battery after film formation and before the first charge, and (b) is a cross section STEM photograph of the lithium ion secondary battery after the first discharge. FIG. 5 is a diagram showing a cross-sectional configuration of a lithium ion secondary battery of a first modified example of the first embodiment. FIG. 7 is a diagram showing a cross-sectional configuration of a lithium ion secondary battery of a second modified example of the first embodiment. FIG. 16 is a diagram showing a cross-sectional configuration of a lithium ion secondary battery of a third modified example of the first embodiment. FIG. 18 is a diagram showing a cross-sectional configuration of a lithium ion secondary battery of a fourth modified example of the first embodiment. (A), (b) is a figure which shows the cross-sectional structure of the lithium ion secondary battery of Embodiment 2. FIG. FIG. 10 is a diagram showing a cross-sectional configuration of a lithium ion secondary battery of Embodiment 3. 7 is a cross-sectional STEM photograph of a lithium ion secondary battery of another configuration example according to Embodiment 1.

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. Note that the size, thickness, and the like of each part in the drawings referred to in the following description may differ from the actual dimensions.

Embodiment 1
[Configuration of lithium ion secondary battery]
FIG. 1 is a view showing a cross-sectional configuration of the lithium ion secondary battery 1 of the first embodiment. The lithium ion secondary battery 1 of the present embodiment has a structure in which a plurality of layers (films) are stacked, as described later, and after forming a basic structure by a so-called film formation process, The structure is completed by the charge and discharge operation. Here, FIG. 1 shows the state after the first discharge, that is, the structure of the lithium ion secondary battery 1 is completed.

The lithium ion secondary battery 1 shown in FIG. 1 includes a substrate 10, a positive electrode current collector layer 20 stacked on the substrate 10, a positive electrode layer 30 stacked on the positive electrode current collector layer 20, and a positive electrode layer 30. A solid electrolyte layer 40 laminated on the upper side, and a holding layer 50 laminated on the solid electrolyte layer 40 are provided. Here, the solid electrolyte layer 40 covers the peripheries of both the positive electrode current collector layer 20 and the positive electrode layer 30 and the end portions thereof are directly laminated on the substrate 10, whereby the positive electrode current collector layer 20 and the substrate 10 are obtained. The positive electrode layer 30 is covered. Further, the lithium ion secondary battery 1 is stacked on the holding layer 50 and directly stacked on the solid electrolyte layer 40 at the periphery of the holding layer 50, thereby covering the solid electrolyte layer 40 with the holding layer 50. A covering layer 60. Furthermore, the lithium ion secondary battery 1 is laminated on the covering layer 60 and directly laminated on the solid electrolyte layer 40 at the periphery of the covering layer 60, thereby covering the covering layer 60 with respect to the solid electrolyte layer 40. A negative electrode current collector layer 70 is provided.

Next, each component of the lithium ion secondary battery 1 will be described in more detail.
(substrate)
The substrate 10 is not particularly limited, and substrates made of various materials such as metal, glass, and ceramics can be used.
Here, in the present embodiment, the substrate 10 is formed of a metal plate having electron conductivity. More specifically, in the present embodiment, a stainless steel foil (plate) having a mechanical strength higher than that of copper, aluminum or the like is used as the substrate 10. Further, as the substrate 10, a metal foil plated with a conductive metal such as tin, copper, chromium or the like may be used.

The thickness of the substrate 10 can be, for example, 20 μm or more and 2000 μm or less. If the thickness of the substrate 10 is less than 20 μm, the strength of the lithium ion secondary battery 1 may be insufficient. On the other hand, when the thickness of the substrate 10 exceeds 2000 μm, the volume energy density and weight energy density decrease due to the increase in thickness and weight of the battery.

(Positive current collector layer)
The positive electrode current collector layer 20 is not particularly limited as long as it is a solid thin film and has electron conductivity, and for example, a conductive material containing various metals or an alloy of various metals is used. Can.

The thickness of the positive electrode current collector layer 20 can be, for example, 5 nm or more and 50 μm or less. If the thickness of the positive electrode current collector layer 20 is less than 5 nm, the current collection function is lowered and it is not practical. On the other hand, when the thickness of the positive electrode current collector layer 20 exceeds 50 μm, the internal resistance of the battery becomes high, which is disadvantageous for high-speed charge and discharge.

Also, as a method of manufacturing the positive electrode current collector layer 20, known film forming methods such as various PVD (physical vapor deposition) and various CVD (chemical vapor deposition) may be used, but from the viewpoint of production efficiency It is desirable to use a method or a vacuum evaporation method.

When the substrate 10 is made of a conductive material such as a metal plate, the positive electrode current collector layer 20 may not be provided between the substrate 10 and the positive electrode layer 30. On the other hand, in the case of using an insulating material as the substrate 10, the positive electrode current collector layer 20 may be provided between the substrate 10 and the positive electrode layer 30.

(Positive layer)
The positive electrode layer 30 is a solid thin film, and contains a positive electrode active material that desorbs lithium ions during charging and stores lithium ions during discharging. Here, as a positive electrode active material constituting the positive electrode layer 30, for example, one type selected from manganese (Mn), cobalt (Co), nickel (Ni), iron (Fe), molybdenum (Mo), vanadium (V) It is possible to use one composed of various materials such as oxides, sulfides or phosphorus oxides containing the above metals. Further, the positive electrode layer 30 may be a composite positive electrode containing a solid electrolyte.

The thickness of the positive electrode layer 30 can be, for example, 10 nm or more and 40 μm or less. If the thickness of the positive electrode layer 30 is less than 10 nm, the capacity of the obtained lithium ion secondary battery 1 becomes too small to be practical. On the other hand, when the thickness of the positive electrode layer 30 exceeds 40 μm, it takes too long to form the layer, and the productivity is lowered. However, when the battery capacity required for the lithium ion secondary battery 1 is large, the thickness of the positive electrode layer 30 may be more than 40 μm.

Furthermore, as a method of producing the positive electrode layer 30, known film forming methods such as various PVD and various CVD may be used, but from the viewpoint of production efficiency, it is desirable to use the sputtering method.

(Solid electrolyte layer)
The solid electrolyte layer 40 is a solid thin film, and includes a solid electrolyte (inorganic solid electrolyte) made of an inorganic material. Here, the inorganic solid electrolyte constituting the solid electrolyte layer 40 is not particularly limited as long as it exhibits lithium ion conductivity, and is made of various materials such as oxides, nitrides, and sulfides. Can be used.

The thickness of the solid electrolyte layer 40 can be, for example, 10 nm or more and 10 μm or less. When the thickness of the solid electrolyte layer 40 is less than 10 nm, a short circuit (leakage) is likely to occur between the positive electrode layer 30 and the holding layer 50 in the obtained lithium ion secondary battery 1. On the other hand, when the thickness of the solid electrolyte layer 40 exceeds 10 μm, the internal resistance of the battery becomes high, which is disadvantageous for high-speed charge and discharge.

Furthermore, as a method of manufacturing the solid electrolyte layer 40, known film forming methods such as various PVD and various CVD may be used, but from the viewpoint of production efficiency, it is preferable to use the sputtering method.

(Retention layer)
The holding layer 50 is a solid thin film and has a function of holding lithium ions.
And the holding | maintenance layer 50 shown in FIG. 1 is comprised by the porous part 51 in which the many void | hole 52 was formed. That is, the holding layer 50 of the present embodiment has a porous structure. The formation of the porous portion 51 of the holding layer 50 is performed along with the first charge / discharge operation after film formation, and the details thereof will be described later.

Here, the holding layer 50 (porous portion 51) can be made of a platinum group element (Ru, Rh, Pd, Os, Ir, Pt) or gold (Au) or an alloy of these. Among these, it is preferable that the holding layer 50 be made of platinum (Pt) or gold (Au) that is more resistant to oxidation. In addition, the holding layer 50 (porous portion 51) of the present embodiment can be formed of the above-described noble metal or a polycrystal of an alloy of these.

The thickness of the holding layer 50 can be, for example, 10 nm or more and 40 μm or less. If the thickness of the retention layer 50 is less than 10 nm, the ability to retain lithium will be insufficient. On the other hand, when the thickness of the holding layer 50 exceeds 40 μm, the internal resistance of the battery becomes high, which is disadvantageous for high-speed charge and discharge. However, when the battery capacity required for the lithium ion secondary battery 1 is large, the thickness of the holding layer 50 may be more than 40 μm.

Furthermore, as a method of manufacturing the holding layer 50, known film forming methods such as various PVD and various CVD may be used, but from the viewpoint of production efficiency, it is preferable to use the sputtering method. And as a manufacturing method of the holding layer 50 made porous, it is desirable to employ | adopt the method of performing charge and discharge which are mentioned later.

(Cover layer)
The covering layer 60 as an example of the amorphous metal layer is made of a metal or an alloy which is a solid thin film and has an amorphous structure. And among these, from the viewpoint of corrosion resistance, it is preferable that it is chromium (Cr) alone or an alloy containing chromium, and it is more preferable that it is an alloy of chromium and titanium (Ti). The covering layer 60 is preferably made of a metal or alloy which does not form an intermetallic compound with lithium (Li). The covering layer 60 can also be configured by laminating a plurality of amorphous layers different in constituent material (for example, a laminated structure of an amorphous chromium layer and an amorphous chromium titanium alloy layer). In the case where the covering layer 60 is formed of an alloy, the range of the composition ratio to become an amorphous structure depends on the conditions for forming the layer, and thus the range of the preferred composition ratio can not be defined. It may be selected in combination with

The “amorphous structure” in the present embodiment includes not only one having an amorphous structure as a whole but also one having microcrystals precipitated in the amorphous structure. .

The thickness of the covering layer 60 can be, for example, 10 nm or more and 40 μm or less. When the thickness of the covering layer 60 is less than 10 nm, it is difficult for the covering layer 60 to stop the lithium that has passed through the holding layer 50 from the solid electrolyte layer 40 side. On the other hand, when the thickness of the covering layer 60 exceeds 40 μm, the internal resistance of the battery becomes high, which is disadvantageous for high-speed charge and discharge.

Furthermore, as a method of manufacturing the covering layer 60, known film forming methods such as various PVD and various CVD may be used, but from the viewpoint of production efficiency, it is desirable to use the sputtering method. In particular, when the covering layer 60 is made of the above-described chromium titanium alloy, the chromium titanium alloy is likely to be amorphous if the sputtering method is employed.

Examples of metals (alloys) that can be used for the covering layer 60 include ZrCuAlNiPdP, CuZr, FeZr, TiZr, CoZrNb, NiNb, NiNb, NiTiNb, NiP, CuP, NiPCu, NiTi, CrTi, AlTi, FeSiB, and AuSi. be able to.

(Anode current collector layer)
The negative electrode current collector layer 70 as an example of the noble metal layer is not particularly limited as long as it is a solid thin film and has electron conductivity, and includes, for example, various metals and alloys of various metals. A conductive material can be used. However, from the viewpoint of suppressing the corrosion of the covering layer 60, it is preferable to use a chemically stable material, for example, platinum group elements (Ru, Rh, Pd, Os, Ir, Pt) or gold (Au) Or preferably composed of these alloys.

The thickness of the negative electrode current collector layer 70 can be, for example, 5 nm or more and 50 μm or less. If the thickness of the negative electrode current collector layer 70 is less than 5 nm, the corrosion resistance and the current collection function are reduced, which is not practical. On the other hand, when the thickness of the negative electrode current collector layer 70 exceeds 50 μm, the internal resistance of the battery becomes high, which is disadvantageous for high-speed charge and discharge.

Further, as a method of manufacturing the negative electrode current collector layer 70, known film forming methods such as various PVD and various CVD may be used, but from the viewpoint of production efficiency, it is desirable to use the sputtering method.

(Relationship between positive electrode layer and holding layer)
In the lithium ion secondary battery 1, the positive electrode layer 30 and the holding layer 50 face each other with the solid electrolyte layer 40 interposed therebetween. That is, the positive electrode layer 30 containing the positive electrode active material is positioned on the opposite side of the solid electrolyte layer 40 to the holding layer 50. When viewed from above in FIG. 1, the size of the plane of the holding layer 50 is larger than the size of the plane of the positive electrode layer 30. Further, when viewed from above in FIG. 1, the entire peripheral edge of the plane of the positive electrode layer 30 is located inside the entire peripheral edge of the plane of the holding layer 50. As a result, the lower surface (planar surface) of the holding layer 50 is opposed to the upper surface (planar surface) of the positive electrode layer 30 shown in FIG. 1 with the solid electrolyte layer 40 interposed therebetween.

[Method of manufacturing lithium ion secondary battery]
Next, a method of manufacturing the lithium ion secondary battery 1 described above will be described.
FIG. 2 is a flowchart for explaining the method of manufacturing the lithium ion secondary battery of the first embodiment.

First, the substrate 10 is mounted on a sputtering apparatus (not shown), and a positive electrode current collector layer forming step of forming the positive electrode current collector layer 20 on the substrate 10 is performed (step 20). Next, the positive electrode layer forming step of forming the positive electrode layer 30 on the positive electrode current collector layer 20 is performed by the sputtering apparatus (step 30). Next, a solid electrolyte layer forming step of forming the solid electrolyte layer 40 on the positive electrode layer 30 is executed by the sputtering apparatus (step 40). Next, a holding layer forming step of forming the holding layer 50 on the solid electrolyte layer 40 is performed by the sputtering apparatus (step 50). Then, in the sputtering apparatus, a covering layer forming step of forming a covering layer 60 on the solid electrolyte layer 40 and the holding layer 50 is performed (step 60). Then, the negative electrode current collector layer forming step of forming the negative electrode current collector layer 70 on the solid electrolyte layer 40 and the covering layer 60 is executed by the sputtering apparatus (step 70). By performing these steps 20 to 70, the lithium ion secondary battery 1 after film formation (and before the first charge) shown in FIG. 3 described later can be obtained. Then, the lithium ion secondary battery 1 is removed from the sputtering apparatus.

Subsequently, an initial charge step of performing the first charge on the lithium ion secondary battery 1 removed from the sputtering apparatus is performed (step 80). Then, an initial discharge step of performing a first discharge on the charged lithium ion secondary battery 1 is performed (step 90). By the first charge and the first discharge, the holding layer 50 is made porous, that is, the porous portion 51 and the plurality of pores 52 are formed, and the lithium ion secondary battery 1 shown in FIG. 1 is obtained. The details of making the holding layer 50 porous by the first charge and discharge operation will be described later.

[Configuration of lithium ion secondary battery after film formation and before initial charge]
FIG. 3 is a view showing a cross-sectional configuration of the lithium ion secondary battery 1 after film formation and before initial charge according to the first embodiment. FIG. 3 shows a state in which steps up to step 70 shown in FIG. 2 are completed. As described above, FIG. 1 shows a state in which step 90 (all steps) shown in FIG. 2 is completed.

The basic configuration of the lithium ion secondary battery 1 shown in FIG. 3 is the same as that shown in FIG. However, the lithium ion secondary battery 1 shown in FIG. 3 is different in that the holding layer 50 is not made porous and is more compact than that shown in FIG. 1. Further, the lithium ion secondary battery 1 shown in FIG. 3 is different in that the thickness of the holding layer 50 is thinner than that shown in FIG. 1.

[Porporation of Retaining Layer]
Now, the porous formation of the holding layer 50 described above will be described in more detail.
FIG. 4 is a view for explaining the procedure for making the holding layer 50 porous, and is an enlarged view of the holding layer 50 and the periphery thereof. Here, FIG. 4 (a) shows the state after film formation and before the first charge (after step 70), and FIG. 4 (b) shows the state after the first charge and before the first discharge (between step 80 and step 90). FIG. 4C shows the state after the first discharge (after step 90), respectively. Therefore, FIG. 4 (a) corresponds to FIG. 3, and FIG. 4 (c) corresponds to FIG.

(After film formation and before initial charge)
First, in the state of “after film formation and before initial charge” shown in FIG. 4A, the holding layer 50 is densified. The thickness of the holding layer 50 is a holding layer thickness t50, the thickness of the covering layer 60 is a covering layer thickness t60, and the thickness of the negative electrode current collector layer 70 is a negative electrode current collector layer thickness t70. It is.

(After first charge and before first discharge)
When the lithium ion secondary battery 1 shown in FIG. 4A is charged (first charge), the substrate 10 (see FIG. 1) has a positive electrode of a DC power supply, and the negative electrode collector layer 70 has a DC power supply. Negative electrodes are connected respectively. Then, as shown in FIG. 4B, lithium ions (Li ⁺ ) constituting the positive electrode active material in the positive electrode layer 30 move to the holding layer 50 via the solid electrolyte layer 40. That is, in the charging operation, lithium ions move in the thickness direction of the lithium ion secondary battery 1 (upward in FIG. 4B).

At this time, lithium ions moved from the positive electrode layer 30 side to the holding layer 50 side are alloyed with the noble metal constituting the holding layer 50. For example, when the holding layer 50 is made of platinum (Pt), in the holding layer 50, lithium and platinum are alloyed (solid solution, formation of an intermetallic compound or eutectic).

In addition, part of lithium ions that have entered the holding layer 50 pass through the holding layer 50 and reach the boundary with the covering layer 60. Here, the covering layer 60 of the present embodiment is made of a metal or an alloy having an amorphous structure, and the number of grain boundaries is significantly reduced as compared with the holding layer 50 having a polycrystalline structure. There is. For this reason, the lithium ions that have reached the boundary between the holding layer 50 and the covering layer 60 hardly enter the covering layer 60, and therefore, the state of being held in the holding layer 50 is maintained.

Then, the lithium ions transferred from the positive electrode layer 30 to the holding layer 50 are held by the holding layer 50 in the state where the initial charging operation is finished. At this time, it is considered that lithium ions transferred to the holding layer 50 are held in the holding layer 50 by alloying with platinum, precipitation of metal lithium in platinum, or the like.

Here, as shown in FIG. 4 (b), in the lithium ion secondary battery 1 after the first charge and before the first discharge, the holding layer thickness t50 is after the film formation shown in FIG. 4 (a) and before the first charge. Increase from the state of That is, the volume of the holding layer 50 is increased by the first charge. This is considered to be attributable to the alloying of lithium and platinum in the holding layer 50. On the other hand, the coating layer thickness t60 is substantially unchanged before and after the first charge. That is, the volume of the covering layer 60 is not substantially changed by the first charge. This is considered to be due to the fact that lithium does not easily enter the covering layer 60. And this means that the negative electrode current collector layer thickness t70 does not substantially change before and after the initial charge, that is, the volume of the negative electrode current collector layer 70 does not substantially change before and after the initial charge (negative electrode collection It is considered that the platinum that constitutes the collector layer 70 is supported by the fact that it is not made porous like the platinum that constitutes the holding layer 50 and remains compact.

(After the first discharge)
When the lithium ion secondary battery 1 shown in FIG. 4B is discharged (first discharge), the substrate 10 (see FIG. 1) has a positive electrode of the load and the negative electrode collector layer 70 of the negative electrode. The electrodes are connected respectively. Then, as shown in FIG. 4C, lithium ions (Li ⁺ ) held in the holding layer 50 move to the positive electrode layer 30 through the solid electrolyte layer 40. That is, in the discharge operation, lithium ions move in the thickness direction of the lithium ion secondary battery 1 (downward in FIG. 4C) and are held in the positive electrode layer 30. Along with this, a direct current is supplied to the load.

At this time, in the holding layer 50, the dealloying of the alloy of lithium and platinum (the dissolution of metal lithium when metal lithium is deposited) is performed as lithium is separated. And as a result of performing dealloying by the holding | maintenance layer 50, the holding | maintenance layer 50 is made porous and it becomes the porous part 51 in which the many void | hole 52 was formed. The porous portion 51 obtained in this manner is substantially composed of a noble metal (for example, platinum). However, in the state where the first discharge is finished, lithium does not necessarily disappear inside the holding layer 50, and some lithium which does not move due to the discharge operation remains.

Here, as shown in FIG. 4C, in the lithium ion secondary battery 1 after the first discharge, the holding layer thickness t50 is greater than the state after the first charge and before the first discharge shown in FIG. 4B. Decrease. This is considered to be due to the fact that the alloy of lithium and platinum is dealloyed in the retaining layer 50. This is supported by the fact that the shape of the holes 52 formed in the holding layer 50 by the initial discharge is flattened so that the thickness direction becomes smaller than the surface direction. Further, as shown in FIG. 4C, in the lithium ion secondary battery 1 after the first discharge, the holding layer thickness t50 is larger than the state after the film formation shown in FIG. 4A and before the first charge. Do. It is considered that this is caused by the fact that the holding layer 50 is made porous by the first charge and the first discharge, that is, a large number of pores 52 are formed in the holding layer 50. On the other hand, the coating layer thickness t60 and the negative electrode current collector layer thickness t70 are substantially the same before and after the first discharge.

[Configuration Example of Lithium Ion Secondary Battery]
FIG. 5 is a cross-sectional STEM (Scanning Transmission Electron Microscope) photograph of the lithium ion secondary battery 1 of the present embodiment, where (a) shows the state after film formation and before the first charge, and (b) shows the state after the first discharge. The state of each is shown. The STEM photograph was taken using a Hitachi High-Technologies Corporation HD-2300 ultrathin film evaluation apparatus. Here, FIG. 5 (a) corresponds to FIG. 4 (a) (and FIG. 3) described above, and FIG. 5 (b) corresponds to FIG. 4 (c) (and FIG. 1) described above.

The specific structure and manufacturing method of the lithium ion secondary battery 1 shown to Fig.5 (a) are as showing below.

Stainless steel (SUS304) was used for the substrate 10 (not shown in FIG. 5). The thickness of the substrate 10 was 30 μm.

For the positive electrode current collector layer 20 (not shown in FIG. 5), aluminum formed by sputtering was used. The thickness of the positive electrode current collector layer 20 was 100 nm.

For the positive electrode layer 30 (not shown in FIG. 5), lithium manganate (Li _1.5 Mn ₂ O ₄ ) formed by sputtering was used. The thickness of the positive electrode layer 30 was 1000 nm.

For the solid electrolyte layer 40, LiPON (a lithium phosphate (Li ₃ PO ₄ ) part of which oxygen was replaced with nitrogen) formed by sputtering was used. The thickness of the solid electrolyte layer 40 was 1000 nm.

For the holding layer 50, platinum (Pt) formed by sputtering was used. The thickness of the holding layer 50 was 410 nm (after film formation and before initial charge).

For the covering layer 60, a chromium titanium alloy (more specifically, Cr ₅₀ Ti ₅₀ ) formed by a sputtering method was used. The thickness of the covering layer 60 was 50 nm.

For the negative electrode current collector layer 70, platinum (Pt) formed by a sputtering method was used. The thickness of the negative electrode current collector layer 70 was 100 nm.

With respect to the lithium ion secondary battery 1 (see FIG. 3) after film formation and before the first charge thus obtained, the crystal structure was analyzed by electron beam diffraction, and it was as follows.

The substrate 10 made of SUS304, the positive electrode current collector layer 20 made of aluminum, the holding layer 50 made of platinum, and the negative electrode current collector layer 70 were each crystallized. On the other hand, the positive electrode layer 30 made of lithium manganate, the solid electrolyte layer 40 made of LiPON, and the coating layer 60 made of a chromium titanium alloy were respectively made amorphous. However, in each of the positive electrode layer 30, the solid electrolyte layer 40, and the covering layer 60, a ring was slightly observed by electron beam diffraction, and it was found that microcrystals were present in the amorphous structure.

An initial charge and an initial discharge were performed on the lithium ion secondary battery 1 obtained in this manner.
・ First charge condition Current 1C
End voltage 4.0 V or 2 hours, first discharge condition Current 1 C
End voltage 2.0V

Now, the STEM picture shown in FIG. 5 will be described.
First, FIG. 5A shows that the holding layer 50 is almost uniformly white, whereas FIG. 5B shows that a plurality of gray spots are present on the white background. Further, in FIG. 5B, the holding layer 50 is flattened on the side of the boundary with the covering layer 60 so that the thickness direction becomes smaller than the surface direction, and compared to other gray spots. It also shows that relatively large gray areas exist. Here, in FIG. 5 (b), it is considered that the white part corresponds to the porous part 51 and the gray part corresponds to the air holes 52. In addition, in FIG.5 (b), it turns out also compared with FIG.5 (a) that the holding | maintenance layer 50 is thicker. The thickness of the holding layer 50 shown in FIG. 5B was 610 nm (after the first discharge).

Further, in both FIG. 5A and FIG. 5B, it can be seen that the covering layer 60 and the negative electrode current collector layer 70 hardly change with respect to their respective shades. Furthermore, in both FIG. 5A and FIG. 5B, it can also be seen that the coating layer 60 and the negative electrode current collector layer 70 hardly change with respect to their respective thicknesses.

[Another Configuration Example of Lithium Ion Secondary Battery]
FIG. 12 is a cross-sectional STEM photograph of a lithium ion secondary battery 1 of another configuration example according to the present embodiment. Here, FIG. 12 shows the state after the first discharge. Similar to FIG. 5 described above, this STEM photograph was taken using an HD-2300 ultrathin film evaluation apparatus manufactured by Hitachi High-Technologies Corporation. FIG. 12 corresponds to FIG. 4 (c) (and FIG. 1) described above.

The specific configuration and manufacturing method of the lithium ion secondary battery 1 shown in FIG. 12 are as follows.

Stainless steel (SUS304) was used for the substrate 10 (not shown in FIG. 12). The thickness of the substrate 10 was 30 μm.

For the positive electrode current collector layer 20 (not shown in FIG. 12), aluminum formed by sputtering was used. The thickness of the positive electrode current collector layer 20 was 100 nm.

For the positive electrode layer 30 (not shown in FIG. 12), lithium manganate (Li _1.5 Mn ₂ O ₄ ) formed by sputtering was used. The thickness of the positive electrode layer 30 was 1000 nm.

For the solid electrolyte layer 40, lithium phosphate (Li ₃ PO ₄ ) formed by sputtering was used. The thickness of the solid electrolyte layer 40 was 1000 nm.

For the holding layer 50, platinum (Pt) formed by sputtering was used. The thickness of the holding layer 50 was 70 nm (after film formation and before initial charge).

For the covering layer 60, a CoZrNb alloy (more specifically, Co ₉₁ Zr ₅ Nb ₄ ) formed by a sputtering method was used. The thickness of the covering layer 60 was 200 nm.

For the negative electrode current collector layer 70, platinum (Pt) formed by a sputtering method was used. The thickness of the negative electrode current collector layer 70 was 70 nm.

The crystal structure of the lithium ion secondary battery 1 obtained as described above after film formation and before the first charge was analyzed by electron beam diffraction, and found to be as follows.

The substrate 10 made of SUS304, the positive electrode current collector layer 20 made of aluminum, the holding layer 50 made of platinum, and the negative electrode current collector layer 70 were each crystallized. On the other hand, the positive electrode layer 30 made of lithium manganate, the solid electrolyte layer 40 made of lithium phosphate (Li ₃ PO ₄ ), and the coating layer 60 made of a CoZrNb alloy were amorphized, respectively. However, in each of the positive electrode layer 30, the solid electrolyte layer 40, and the covering layer 60, a ring was slightly observed by electron beam diffraction, and it was found that microcrystals were present in the amorphous structure.

An initial charge and an initial discharge were performed on the lithium ion secondary battery 1 obtained in this manner. The initial charge condition and the initial discharge condition are the same as those described above with reference to FIG.

In FIG. 12, similarly to FIG. 5 (b) described above, the holding layer 50 is flattened on the side of the boundary with the covering layer 60 so that the thickness direction becomes smaller than the surface direction, and It can be seen that relatively large gray areas exist as compared to gray spots. Here, in FIG. 12, as in FIG. 5 (b), it is considered that the white area corresponds to the porous portion 51, and the gray area corresponds to the air holes 52. The thickness of the holding layer 50 shown in FIG. 12 was 105 nm (after the first discharge).

Also in this case, the coating layer 60 and the negative electrode current collector layer 70 hardly changed with respect to their respective shades and thicknesses before and after the first charge and discharge.

[Summary of Embodiment 1]
As described above, in the lithium ion secondary battery 1 of the present embodiment, the metal or alloy having an amorphous structure in the holding layer 50 disposed to face the positive electrode layer 30 with the solid electrolyte layer 40 interposed therebetween. The coating layer 60 was laminated. Thereby, as compared with, for example, the case where the covering layer 60 having a polycrystalline structure is laminated on the holding layer 50, the covering layer 60 of lithium transferred from the positive electrode layer 30 to the holding layer 50 along with the charging operation Leaks to the outside can be suppressed.

Moreover, in the present embodiment, the holding layer 50 made of porous platinum is provided on the solid electrolyte layer 40. Thereby, as compared with the case where the negative electrode layer made of, for example, silicon (Si) or the like is provided on solid electrolyte layer 40, peeling within lithium ion secondary battery 1 accompanying expansion due to charge and contraction due to discharge. Can be suppressed.

Furthermore, in the present embodiment, the negative electrode current collector layer 70 made of platinum is provided on the covering layer 60. Thereby, the corrosion (deterioration) due to oxidation or the like of the metal or alloy constituting the covering layer 60 is suppressed as compared to the case where the negative electrode current collector layer 70 made of other than noble metal is provided on the covering layer 60 be able to.

Furthermore, in the lithium ion secondary battery 1 of the present embodiment, the size of the flat surface of the positive electrode layer 30 and the holding layer 50 disposed with the solid electrolyte layer 40 therebetween is positive electrode layer 30 <holding layer 50. Thereby, movement in the lateral direction (surface direction) when lithium ions move from the positive electrode layer 30 to the holding layer 50 side is suppressed. As a result, leakage of lithium ions from the side of the lithium ion secondary battery 1 to the outside can be suppressed.

Although not described in detail here, platinum (Pt) is used when the holding layer 50 is formed of platinum group elements (Ru, Rh, Pd, Os, Ir, Pt) or gold (Au) or their alloys. The holding layer 50 can be made porous by charging and discharging, as in the case where the holding layer 50 is constituted alone, and lithium can be held in the holding layer 50.

[Modification of Embodiment 1]
In lithium ion secondary battery 1 of the first embodiment, substrate 10 and solid electrolyte layer 40 are used to cover positive electrode current collector layer 20 and positive electrode layer 30, and solid electrolyte layer 40 and covering layer 60. And although the structure which covers the holding layer 50 using the negative electrode collector layer 70 was employ | adopted, it is not restricted to this.

(First modification)
FIG. 6 is a diagram showing a cross-sectional configuration of a lithium ion secondary battery 1 of a first modified example of the first embodiment. Here, FIG. 6 shows a state after the first discharge, that is, a state in which the structure of the lithium ion secondary battery 1 is completed (corresponding to FIG. 1 of the first embodiment).

In this first modification, the planar size of the positive electrode current collector layer 20 and the positive electrode layer 30 when viewed from the upper side of FIG. 6 is substantially the same as the planar size of the solid electrolyte layer 40. This is different from the first embodiment. However, also in the first modification, after manufacturing lithium ion secondary battery 1 including dense holding layer 50 in the same procedure as in Embodiment 1 (see FIG. 2), charging for the first time after film formation is performed. By performing the discharge operation, the lithium ion secondary battery 1 (see FIG. 6) in which the holding layer 50 is made porous can be obtained.

(Second modification)
FIG. 7 is a diagram showing a cross-sectional configuration of a lithium ion secondary battery 1 according to a second modification of the first embodiment. Here, FIG. 7 shows a state after the first discharge, that is, a state in which the structure of the lithium ion secondary battery 1 is completed (corresponding to FIG. 1 of the first embodiment).

In the second modification, the size of the plane of the covering layer 60 when viewed from above in FIG. 7 is the same as the size of the plane of the holding layer 50, and when viewed from above in FIG. The second embodiment differs from the first embodiment in that the size of the negative electrode current collector layer 70 is the same as the size of the flat surface of the covering layer 60. However, also in the second modification, after manufacturing lithium ion secondary battery 1 including dense holding layer 50 in the same procedure as in Embodiment 1 (see FIG. 2), charging for the first time after film formation is performed. By performing the discharge operation, it is possible to obtain the lithium ion secondary battery 1 (see FIG. 7) in which the holding layer 50 is made porous.

(Third modification)
FIG. 8 is a diagram showing a cross-sectional configuration of a lithium ion secondary battery 1 of a third modification of the first embodiment. Here, FIG. 8 shows a state after the first discharge, that is, a state in which the structure of the lithium ion secondary battery 1 is completed (corresponding to FIG. 1 of the first embodiment).

In the third modification, the size of the plane of the covering layer 60 when viewed from above in FIG. 8 is the same as the size of the plane of the holding layer 50, and when viewed from above in FIG. This embodiment differs from the first modification in that the size of the negative electrode current collector layer 70 is the same as the size of the flat surface of the covering layer 60. However, also in the third modification, after manufacturing lithium ion secondary battery 1 including dense holding layer 50 in the same procedure as in Embodiment 1 (see FIG. 2), charging for the first time after film formation is performed. By performing the discharge operation, the lithium ion secondary battery 1 (see FIG. 8) in which the holding layer 50 is made porous can be obtained.

(The 4th modification)
FIG. 9 is a diagram showing a cross-sectional configuration of a lithium ion secondary battery 1 of a fourth modification of the first embodiment. Here, FIG. 9 shows a state (corresponding to FIG. 1 of the first embodiment) after the first discharge, that is, the structure of the lithium ion secondary battery 1 is completed.

In the fourth modification, the size of the plane of the holding layer 50 when viewed from above in FIG. 9 is the same as the size of the plane of the solid electrolyte layer 40, Is different. However, also in the fourth modification, after manufacturing lithium ion secondary battery 1 including dense holding layer 50 in the same procedure as in Embodiment 1 (see FIG. 2), charging for the first time after film formation is performed. By performing the discharge operation, it is possible to obtain a lithium ion secondary battery 1 (see FIG. 9) in which the holding layer 50 is made porous.

Second Embodiment
In the first embodiment, the holding layer 50 is made of a noble metal having a porous structure. On the other hand, in the present embodiment, the holding layer 50 is made of titanium (Ti) having a plurality of columnar crystals each extending in the thickness direction. In the present embodiment, the same components as those in Embodiment 1 are assigned the same reference numerals and detailed explanations thereof will be omitted.

[Configuration of lithium ion secondary battery]
FIG. 10 is a diagram showing a cross-sectional configuration of lithium ion secondary battery 1 of the second embodiment. As in the first embodiment, the lithium ion secondary battery 1 of the present embodiment has a structure in which a plurality of layers (films) are stacked, and after a basic structure is formed by a so-called film formation process, The structure is completed by the first (first) charging operation. Here, FIG. 10A shows the state after film formation and before the first charge, and FIG. 10B shows the state after the first charge.

(Configuration of lithium ion secondary battery after film formation)
As shown in FIG. 10A, the lithium ion secondary battery 1 after film formation and before the first charge is the substrate 10, the positive electrode current collector layer 20, and the positive electrode layer 30 as in the first embodiment. The solid electrolyte layer 40, the holding layer 50, the covering layer 60, and the negative electrode current collector layer 70 are stacked in this order.

(Configuration of lithium ion secondary battery after initial charge)
As shown in FIG. 10 (b), the basic configuration of the lithium ion secondary battery 1 after the initial charge is substantially the same as the lithium ion secondary battery 1 after the film formation shown in FIG. 10 (a) and before the initial charge. However, the difference is that the negative electrode 80 is formed inside the holding layer 50.

Next, although each component of the lithium ion secondary battery 1 will be described in more detail, since it has the same configuration as that of the first embodiment except for the holding layer 50 and the negative electrode 80, the holding layer 50 and A description of the negative electrode 80 will be made.

(Retention layer)
The holding layer 50 of the present embodiment is a solid thin film, and has a structure in which a plurality of columnar crystals each made of titanium metal (Ti) and extending in the thickness direction are arranged side by side. The columnar crystals of titanium constituting the holding layer 50 are usually composed of hexagonal columnar crystals.

The thickness of the holding layer 50 can be, for example, 10 nm or more and 40 μm or less. If the thickness of the retention layer 50 is less than 10 nm, the ability to retain lithium will be insufficient. On the other hand, when the thickness of the holding layer 50 exceeds 40 μm, the internal resistance of the battery becomes high, which is disadvantageous for high-speed charge and discharge.

Furthermore, as a method for manufacturing the holding layer 50, known film forming methods such as various PVD and various CVD may be used, but from the viewpoint of efficiently forming an aggregate of columnar crystals of titanium, the sputtering method is used. It is desirable to use

(Negative electrode)
The negative electrode 80 contains a negative electrode active material that stores lithium ions at the time of charge and releases lithium ions at the time of discharge. However, as described above, the negative electrode 80 of the present embodiment is formed inside the holding layer 50 by the charging operation. More specifically, in the holding layer 50, the lithium ion is held at the boundary between adjacent columnar crystals, that is, the so-called crystal grain boundary, whereby the negative electrode 80 is formed. Here, in the present embodiment, metal lithium itself functions as a negative electrode active material.

Moreover, as a manufacturing method of the negative electrode 80, it is desirable to adopt a method of forming (depositing) the negative electrode 80 by charging.

[Method of manufacturing lithium ion secondary battery]
Next, a method of manufacturing the lithium ion secondary battery 1 shown in FIG. 10 will be described. In the present embodiment, as described above, after the basic structure of lithium ion secondary battery 1 shown in FIG. 10A is formed by the so-called film formation process, the first (first) charging operation is performed. The lithium ion secondary battery 1 shown in FIG. 10 (b) is obtained.

First, the substrate 10 is mounted on a sputtering apparatus (not shown), and the positive electrode current collector layer 20, the positive electrode layer 30, the solid electrolyte layer 40, the holding layer 50, the covering layer 60 and the negative electrode current collector layer 70 are formed on the substrate 10. The layers are formed (stacked) in this order. Thus, the lithium ion secondary battery 1 after film formation and before the first charge shown in FIG. 10A is obtained. Then, the lithium ion secondary battery 1 is removed from the sputtering apparatus.

Subsequently, the lithium ion secondary battery 1 after film formation and before the first charge shown in FIG. 10A is charged for the first time. As a result, in the lithium ion secondary battery 1 shown in FIG. 10A, lithium is precipitated at the crystal grain boundaries present inside the holding layer 50. That is, the negative electrode 80 made of lithium is formed inside the holding layer 50, and the lithium ion secondary battery 1 after the initial charge shown in FIG. 10 (b) is obtained. The details of the charge and discharge operation of the lithium ion secondary battery 1 will be described later.

[Operation of lithium ion secondary battery]
When charging the lithium ion secondary battery 1 in a discharged state, the substrate 10 is connected to the positive electrode of the DC power supply, and the negative electrode current collector layer 70 is connected to the negative electrode of the DC power supply. Then, lithium ions constituting the positive electrode active material in the positive electrode layer 30 move to the holding layer 50 through the solid electrolyte layer 40. That is, in the charging operation, lithium ions move in the thickness direction (upward direction in FIG. 10) of the lithium ion secondary battery 1.

At this time, the lithium ions moved from the positive electrode layer 30 side to the holding layer 50 side reach the boundary between the solid electrolyte layer 40 and the holding layer 50. Here, the holding layer 50 is made of metallic titanium and has a plurality of columnar crystals each extending in the thickness direction, and the plurality of columnar crystals are arranged side by side. As a result, the lithium ions reaching the boundary between the solid electrolyte layer 40 and the retention layer 50 enter the grain boundaries of the adjacent columnar crystals and move further along the thickness direction, and are retained in the retention layer 50. .

In addition, part of lithium ions that have entered the holding layer 50 penetrate the holding layer 50 and reach the boundary with the covering layer 60. Here, the covering layer 60 is made of an amorphized metal or alloy in which the number of grain boundaries is smaller than that of titanium metal (aggregation of columnar crystals) constituting the holding layer 50. For this reason, the lithium ions that have reached the boundary between the holding layer 50 and the covering layer 60 hardly enter the covering layer 60, and therefore, the state of being held in the holding layer 50 is maintained.

Then, in the state where the charging operation is completed, the lithium ions moved from the positive electrode layer 30 to the holding layer 50 side are held at the grain boundaries existing between the columnar crystals in the holding layer 50 to constitute the negative electrode 80.

When discharging (using) the lithium ion secondary battery 1 in a charged state, the substrate 10 is connected to the positive electrode of the load, and the negative electrode current collector layer 70 is connected to the negative electrode of the load. Then, lithium ions contained in the negative electrode 80 present inside the holding layer 50 move along the thickness direction (downward direction in FIG. 10) to the positive electrode layer 30 via the solid electrolyte layer 40, and the positive electrode layer 30 constitute a positive electrode active material. Along with this, a direct current is supplied to the load.

Then, in the state where the discharge operation is completed, the negative electrode 80 does not necessarily disappear inside the holding layer 50, and remains by part of lithium which is not moved by the discharge operation.

[Summary of Embodiment 2]
As described above, in the lithium ion secondary battery 1 of the present embodiment, the metal or alloy having an amorphous structure in the holding layer 50 disposed to face the positive electrode layer 30 with the solid electrolyte layer 40 interposed therebetween. The coating layer 60 was laminated. Thereby, as compared with, for example, the case where the covering layer 60 having a polycrystalline structure is laminated on the holding layer 50, the covering layer 60 of lithium transferred from the positive electrode layer 30 to the holding layer 50 along with the charging operation Leaks to the outside can be suppressed.

Further, in the present embodiment, the holding layer 50 formed by arranging columnar crystals made of titanium is provided on the solid electrolyte layer 40. Thereby, as compared with the case where the negative electrode layer made of, for example, silicon (Si) or the like is provided on solid electrolyte layer 40, peeling within lithium ion secondary battery 1 accompanying expansion due to charge and contraction due to discharge. Can be suppressed.

Embodiment 3
In the first and second embodiments, between the solid electrolyte layer 40 and the covering layer 60, the holding layer 50 having the function of holding metallic lithium functioning as the negative electrode and not functioning itself as the negative electrode is provided. On the other hand, in the present embodiment, a layer functioning as a negative electrode is provided between the solid electrolyte layer 40 and the covering layer 60. In the present embodiment, the same components as those in Embodiments 1 and 2 are assigned the same reference numerals and detailed explanations thereof will be omitted.

[Configuration of lithium ion secondary battery]
FIG. 11 is a diagram showing a cross-sectional configuration of lithium ion secondary battery 1 of the third embodiment. The lithium ion secondary battery 1 according to the present embodiment has a structure in which a plurality of layers (films) are stacked as in the first and second embodiments, but unlike the first and second embodiments, The structure is completed by the film forming process.

The lithium ion secondary battery 1 of the present embodiment includes the substrate 10, the positive electrode current collector layer 20, the positive electrode layer 30, the solid electrolyte layer 40, the negative electrode layer 90, the covering layer 60, and the negative electrode current collector. The

layers

70 and 70 are stacked in this order. That is, in the lithium ion secondary battery 1 of the present embodiment, the negative electrode layer 90 is provided at the position of the holding layer 50 of the other embodiments.

Next, although each component of the lithium ion secondary battery 1 will be described in more detail, since it has the same configuration as that of the first and second embodiments except for the negative electrode layer 90, the explanation regarding the negative electrode layer 90 is here. I do.

(Anode layer)
The negative electrode layer 90 (an example of a holding layer) is a solid thin film, and contains a negative electrode active material that occludes lithium ions during charge and releases lithium ions during discharge. And, the negative electrode layer 90 of the present embodiment is made of amorphous silicon (Si) to which a dopant is added. Note that in this embodiment, silicon functions as a negative electrode active material which occludes and releases lithium ions. However, the negative electrode layer 90 may be made of materials other than silicon, and the dopant is not essential.

Here, the dopant to be added to the silicon forming the negative electrode layer 90 is not particularly limited as long as it enhances the conductivity of silicon, and one or two or more elements composed of various elements are used. be able to. However, among various elements, zinc (Zn), cadmium (Cd), boron (B), aluminum (Al), gallium (Ga), indium (In) which makes the anode layer 90 p-type by functioning as an acceptor. Nitrogen (N), Phosphorus (P), Arsenic (As), Sulfur (S), Selenium (Se), Tellurium (Te), which converts the anode layer 90 into n-type by functioning as a donor, thallium (Tl), or a donor. It is desirable to use Among these, it is preferable to use boron (B).

The thickness of the negative electrode layer 90 can be, for example, 10 nm or more and 20 μm or less. If the thickness of the negative electrode layer 90 is less than 10 nm, the capacity of the obtained lithium ion secondary battery 1 becomes too small to be practical. On the other hand, when the thickness of the negative electrode layer 90 exceeds 20 μm, the internal resistance of the battery becomes high, which is disadvantageous for high-speed charge and discharge. However, when the battery capacity required for the lithium ion secondary battery 1 is large, the thickness of the negative electrode layer 90 may be more than 20 μm.

Furthermore, as a method of manufacturing the negative electrode layer 90, known film forming methods such as various PVD and various CVD may be used, but from the viewpoint of production efficiency, it is desirable to use the sputtering method.

[Method of manufacturing lithium ion secondary battery]
Next, a method of manufacturing the lithium ion secondary battery 1 shown in FIG. 11 will be described.
First, the substrate 10 is mounted on a sputtering apparatus (not shown), and the positive electrode current collector layer 20, the positive electrode layer 30, the solid electrolyte layer 40, the negative electrode layer 90, the covering layer 60 and the negative electrode current collector layer 70 are formed on the substrate 10. The layers are formed (stacked) in this order. Thus, the lithium ion secondary battery 1 shown in FIG. 11 is obtained. Then, the lithium ion secondary battery 1 is removed from the sputtering apparatus.

[Operation of lithium ion secondary battery]
When charging the lithium ion secondary battery 1 in a discharged state, the substrate 10 is connected to the positive electrode of the DC power supply, and the negative electrode current collector layer 70 is connected to the negative electrode of the DC power supply. Then, lithium ions constituting the positive electrode active material in the positive electrode layer 30 move to the negative electrode layer 90 through the solid electrolyte layer 40. That is, in the charging operation, lithium ions move in the thickness direction (upward direction in FIG. 11) of the lithium ion secondary battery 1.

At this time, the lithium ions moved from the positive electrode layer 30 side to the negative electrode layer 90 side reach the boundary between the solid electrolyte layer 40 and the negative electrode layer 90. Here, the negative electrode layer 90 is made of silicon formed by adding boron as a dopant. As a result, lithium ions that have reached the boundary between the solid electrolyte layer 40 and the negative electrode layer 90 are held by the negative electrode layer 90.

In addition, part of lithium ions that have entered into the negative electrode layer 90 pierce through the negative electrode layer 90 and reach the boundary with the covering layer 60. Here, the covering layer 60 is made of a metal or an alloy in which the number of grain boundaries is reduced by amorphizing. Therefore, the lithium ions that have reached the boundary between the negative electrode layer 90 and the covering layer 60 are unlikely to enter the covering layer 60, and therefore, the state held in the negative electrode layer 90 is maintained.

When discharging (using) the lithium ion secondary battery 1 in a charged state, the substrate 10 is connected to the positive electrode of the load, and the negative electrode current collector layer 70 is connected to the negative electrode of the load. Then, lithium ions present inside the negative electrode layer 90 move along the thickness direction (downward direction in FIG. 11) to the positive electrode layer 30 through the solid electrolyte layer 40, and the positive electrode active material is Configure. Along with this, a direct current is supplied to the load.

[Summary of Embodiment 3]
As described above, in the lithium ion secondary battery 1 of the present embodiment, a metal or alloy having an amorphous structure in the negative electrode layer 90 disposed opposite to the positive electrode layer 30 with the solid electrolyte layer 40 interposed therebetween. The coating layer 60 was laminated. Thereby, as compared with, for example, the case where the covering layer 60 having a polycrystalline structure is laminated on the negative electrode layer 90, the covering layer 60 of lithium transferred from the positive electrode layer 30 to the negative electrode layer 90 during the charging operation Leaks to the outside can be suppressed.

Further, in the present embodiment, the negative electrode layer 90 made of silicon containing boron is provided. Thereby, compared with the case where the negative electrode layer 90 made of, for example, carbon (C) or the like is provided on the solid electrolyte layer 40, the capacity of the lithium ion secondary battery 1 at the same thickness (volume) is obtained. It can be enlarged.

<Others>
Although in the first to third embodiments, the covering layer 60 is provided on the holding layer 50 (or the negative electrode layer 90), the present invention is not limited to this, and a layer equivalent to the covering layer 60 on the positive electrode layer 30 side. (Amorphous metal layer (amorphous alloy layer) for suppressing diffusion of lithium) may be provided. In this case, the positive electrode layer 30 is an example of the holding layer. In addition, providing an amorphous metal layer (amorphous alloy layer) between the positive electrode collector layer 20 and the positive electrode layer 30 is mentioned as one method for realizing this. In addition, as another method for achieving this, the positive electrode current collector layer 20 itself may be formed of an amorphous metal layer (amorphous alloy layer).

In addition, a layer corresponding to the covering layer 60 may be provided on each of the positive electrode layer 30 side and the holding layer 50 (or negative electrode layer 90) side.

DESCRIPTION OF SYMBOLS 1 lithium ion secondary battery, 10 ... board | substrate, 20 ... positive electrode collector layer, 30 ... positive electrode layer, 40 ... solid electrolyte layer, 50 ... holding layer, 51 ... porous part, 52 ... hole, 60 ... coating Layers 70: negative electrode current collector layer 80: negative electrode 90: negative electrode layer

Claims

A solid electrolyte layer comprising an inorganic solid electrolyte exhibiting lithium ion conductivity;
A retention layer capable of retaining lithium,
A lithium ion secondary battery having an amorphous metal layer composed of a metal or an alloy and having an amorphous structure in order.
The lithium ion secondary battery according to claim 1, wherein the amorphous metal layer contains chromium (Cr).
3. The lithium ion secondary battery according to claim 2, wherein the amorphous metal layer is made of an alloy of chromium (Cr) and titanium (Ti).
The lithium ion secondary battery according to claim 1, wherein the amorphous metal layer is composed of a metal or an alloy which does not form an intermetallic compound with lithium.
The amorphous metal layer is made of any of ZrCuAlNiPdP, CuZr, FeZr, TiZr, CoZrNb, NiNb, NiTiNb, NiP, CuP, NiPCu, NiTi, CrTi, AlTi, FeSiB, AuSi. Item 6. The lithium ion secondary battery according to item 1.
The said holding | maintenance layer is comprised by the platinum group element (Ru, Rh, Pd, Os, Ir, Pt) or gold (Au) which has a porous structure, or these alloys. The lithium ion secondary battery according to any one of the above.
The lithium ion secondary battery according to any one of claims 1 to 5, wherein the holding layer is made of titanium having a plurality of columnar crystals each extending in a thickness direction.
The lithium ion secondary battery according to any one of claims 1 to 5, wherein the holding layer contains a negative electrode active material.
The lithium ion secondary battery according to any one of claims 1 to 5, wherein the holding layer contains a positive electrode active material.
It has a positive electrode layer containing a positive electrode active material on the opposite side to the said holding layer of the said solid electrolyte layer,
10. The lithium ion secondary battery according to claim 1, wherein a size of a plane of the holding layer is larger than a size of a plane of the positive electrode layer.
A platinum group element (Ru, Rh, Pd, Os, Ir, Pt) or gold (Au) or an alloy thereof, further comprising a noble metal layer laminated on the amorphous metal layer. 11. A lithium ion secondary battery according to any one of items 1 to 10.