WO2020012734A1

WO2020012734A1 - Lithium ion secondary battery

Info

Publication number: WO2020012734A1
Application number: PCT/JP2019/014775
Authority: WO
Inventors: 安田　剛規; 坂脇　彰
Original assignee: 昭和電工株式会社
Priority date: 2018-07-10
Filing date: 2019-04-03
Publication date: 2020-01-16
Also published as: JP2020009653A

Abstract

This lithium ion secondary battery 1 is configured by, laminated in this order: a substrate 10 that comprises stainless steel and that doubles as a positive electrode current collector layer; a ground layer 20 configured by LiNiO₂; a positive electrode layer 30 configured by a composite material positive electrode that contains LiNiO₂ and Li₃PO₄; a first solid electrolyte layer 41 configured by Li₃PO₄; a second solid electrolyte layer 42 configured by LiPON for which a portion of the oxygen in Li₃PO₄ is substituted with nitrogen; a holding layer 50 configured by Pt; a diffusion prevention layer 60 configured by CrTi; and a negative electrode current collector layer 70 configured by Pt. By doing this, in the lithium ion secondary battery that uses LiPON as a solid electrolyte, a decrease in the capacity retention rate is suppressed.

Description

Lithium ion secondary battery

The present invention relates to a lithium ion secondary battery.

携帯 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 with high energy density. As a secondary battery satisfying such requirements, a lithium ion secondary battery is known. A lithium ion secondary battery has a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and an electrolyte having lithium ion conductivity and disposed between the positive electrode and the negative electrode.

In a conventional lithium ion secondary battery, an organic electrolyte or the like has been used as an electrolyte. On the other hand, an all-solid-state and thin-film type lithium ion secondary battery in which a solid electrolyte made of an inorganic material (inorganic solid electrolyte) is used as an electrolyte and the negative electrode, the solid electrolyte, and the positive electrode are all formed of thin films has been proposed. (See Patent Document 1).
Patent Literature 1 describes that Li ₃ PO _4-x N _x (generally referred to as LiPON) obtained by adding nitrogen to lithium phosphate (Li ₃ PO ₄ ) is used as a solid electrolyte. I have.

JP 2013-73846 A

In general, the capacity of a lithium ion secondary battery gradually decreases over time after charging, even if it is not particularly used. Here, the ratio of the capacity of the lithium ion secondary battery at the time when a predetermined period has elapsed to the initial capacity after the completion of charging, expressed as a percentage, is referred to as a capacity retention rate.
When LiPON is used as the solid electrolyte, the capacity retention ratio tends to decrease, and the time until the lithium ion secondary battery does not function as a power source after charging is shortened even if not particularly used. there were.
An object of the present invention is to suppress a decrease in capacity retention in a lithium ion secondary battery using LiPON as a solid electrolyte.

The lithium ion secondary battery of the present invention includes a positive electrode layer containing a positive electrode active material, a first solid electrolyte layer containing Li ₃ PO ₄ , and a lithium ion secondary battery containing LiPON in which part of oxygen in Li ₃ PO ₄ is replaced with nitrogen. It has two solid electrolyte layers and a negative electrode layer containing a negative electrode active material in order.
In such a lithium ion secondary battery, the thickness of the first solid electrolyte layer may be smaller than the thickness of the second solid electrolyte layer.
Further, the first solid electrolyte layer and the second solid electrolyte layer may each have an amorphous structure.
Further, the positive electrode layer includes a LiNiO ₂ and _Li 3 PO _4, the ratio of LiNiO ₂ and _Li 3 PO ₄ in the positive electrode layer is, in molar ratio, 9: 1 to 3: 2 by weight It can be characterized.

From another viewpoint, the lithium ion secondary battery of the present invention includes a positive electrode layer containing a positive electrode active material and a solid layer containing lithium (Li), phosphate (PO ₄ ^3- ), and nitrogen (N). An electrolyte layer and a negative electrode layer containing a negative electrode active material are sequentially provided, and the solid electrolyte layer is such that the concentration of nitrogen on the side facing the positive electrode layer is lower than the concentration of nitrogen on the side facing the negative electrode layer. It is characterized by.
In such a lithium ion secondary battery, the solid electrolyte layer may be characterized in that the concentration of nitrogen on the side facing the positive electrode layer is 0%.

Further, when regarded from another aspect, a lithium ion secondary battery of the present invention includes a positive electrode collector layer made of a metal or an alloy, an underlayer that does not contain _Li 3 PO ₄ comprises LiNiO _2, LiNiO ₂ and Li ₃ and covering material the positive electrode layer containing PO _4, _Li 3 and the first solid electrolyte layer containing no LiNiO ₂ comprises PO _4, second solid electrolyte comprising a LiPON a portion of the oxygen was replaced with nitrogen in _Li 3 PO ₄ And a negative electrode layer containing a negative electrode active material.
In such a lithium ion secondary battery, the second solid electrolyte layer is formed of a platinum group element (Ru, Rh, Pd, Os, Ir, Pt), gold (Au), aluminum (Al), or an alloy thereof. A metal layer is formed, and the negative electrode layer is made of lithium alloyed with a metal forming the metal layer.

According to the present invention, in a lithium ion secondary battery using LiPON as a solid electrolyte, a decrease in capacity retention can be suppressed.

FIG. 2 is a diagram illustrating a cross-sectional configuration of a lithium ion secondary battery according to an embodiment. 4 is a flowchart illustrating a method for manufacturing a lithium ion secondary battery according to an embodiment. FIG. 3 is a diagram illustrating a cross-sectional configuration of a lithium ion secondary battery of a first comparative example. It is a figure showing the section composition of the lithium ion secondary battery of the 2nd comparative example. It is a figure showing the section composition of the lithium ion secondary battery of the 3rd comparative example.

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

[Configuration of lithium ion secondary battery]
FIG. 1 is a diagram showing a cross-sectional configuration of a lithium ion secondary battery 1 of the present embodiment. As described later, the lithium ion secondary battery 1 of the present embodiment has a structure in which a plurality of layers are stacked. After forming a basic structure by a so-called film forming process, the first charge / discharge operation is performed. Completes the structure.

The lithium ion secondary battery 1 shown in FIG. 1 includes a substrate 10, an underlayer 20 laminated on the substrate 10, a positive electrode layer 30 laminated on the underlayer 20, and a solid layer laminated on the positive electrode layer 30. And an electrolyte layer 40. Here, the solid electrolyte layer 40 covers the peripheral edges of both the base layer 20 and the positive electrode layer 30 and the ends thereof are directly laminated on the substrate 10, so that the solid electrolyte layer 40 covers the base layer 20 and the positive electrode layer 30 together with the substrate 10. I have. Further, the lithium ion secondary battery 1 has a holding layer 50 stacked on the solid electrolyte layer 40, a diffusion prevention layer 60 stacked on the holding layer 50, and a negative electrode collection layer stacked on the diffusion prevention layer 60. And an electric conductor layer 70.

Next, each component of the lithium ion secondary battery 1 will be described in more detail. (substrate)
The substrate 10 serves as a base for stacking the base layer 20 to the negative electrode current collector layer 70 by a film forming process.
The material forming the substrate 10 is not particularly limited, and various materials such as metal, glass, ceramics, and resin can be adopted.

Here, in the present embodiment, the substrate 10 is made of a metal plate having electron conductivity. Thus, in the present embodiment, the substrate 10 functions as a positive electrode current collector layer that collects electric power into the positive electrode layer 30 via the base layer 20. More specifically, in the present embodiment, a stainless steel foil (plate) having higher mechanical strength than copper, aluminum, or the like is used as the substrate 10. In addition, as the substrate 10, a metal foil plated with a conductive metal such as tin, copper, or chromium may be used.

The thickness of the substrate 10 can be, for example, not less than 20 μm and not more than 2000 μm. 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 the weight energy density decrease due to an increase in the thickness and weight of the battery.

The substrate 10 has a front surface 10a and a back surface 10b, and the base layer 20 to the negative electrode current collector layer 70 are stacked on the front surface 10a.
Here, the maximum height Rmax of the front surface 10a and the back surface 10b of the substrate 10 is about 300 nm to 500 nm.

(Underlayer)
The base layer 20 is a solid thin film, which enhances the adhesion between the substrate 10 and the positive electrode layer 30, and forms a metal material such as stainless steel forming the substrate 10 and Li ₃ PO ₄ (phosphoric acid) forming the positive electrode layer 30. (Lithium: described later in detail) is a barrier for suppressing direct contact.
The underlayer 20 is made of a metal or a metal compound, which has electron conductivity and is hardly corroded by Li ⁺ (lithium ion) or PO ₄ ^3- (phosphate ion) constituting Li ₃ PO _4. Can be used.

Here, in the present embodiment, the underlayer 20 is made of LiNiO ₂ (nickel phosphate). LiNiO ₂ is sometimes used as a positive electrode material of the lithium ion secondary battery 1.

The thickness of the underlayer 20 can be, for example, not less than 5 nm and not more than 50 μm. If the thickness of the underlayer 20 is less than 5 nm, the function as a barrier is reduced, which is not practical. On the other hand, when the thickness of the underlayer 20 exceeds 50 μm, the internal resistance of the battery increases, which is disadvantageous for high-speed charging and discharging.

In addition, as a method of manufacturing the underlayer 20, a known film forming technique such as various PVD (physical vapor deposition) or various CVD (chemical vapor deposition) may be used, but from the viewpoint of production efficiency, a sputtering method or a vacuum method is used. It is desirable to use an evaporation method.

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

Here, in the present embodiment, the positive electrode layer 30 is composed of a mixed positive electrode including a positive electrode active material and a solid electrolyte made of an inorganic material (inorganic solid electrolyte). More specifically, the positive electrode layer 30 of the present embodiment has a solid electrolyte region mainly containing an inorganic solid electrolyte and a positive electrode region mainly containing a positive electrode active material. In the positive electrode layer 30, the inorganic solid electrolyte forming the solid electrolyte region and the positive electrode active material forming the positive electrode region are mixed while maintaining each. As a result, in the positive electrode layer 30, one is a matrix (base material) and the other is a filler (particle). Here, in the positive electrode layer 30, it is desirable that the solid electrolyte region be a matrix and the positive electrode region be a filler.

In the present embodiment, the same LiNiO ₂ as the underlayer 20 is used as the positive electrode active material constituting the positive electrode layer 30. Li ₃ PO ₄ (lithium phosphate) is used as the inorganic solid electrolyte constituting the positive electrode layer 30. Here, the ratio between the positive electrode active material and the inorganic solid electrolyte in the positive electrode layer 30 may be appropriately selected. However, from the viewpoint of securing both capacity and conductivity, the molar ratio of the positive electrode active material to the inorganic solid electrolyte is from 9: 1 (90%: 10%) to 3: 2 (60%: 40%).

The thickness of the positive electrode layer 30 can be, for example, not less than 10 nm and not more than 40 μm. When 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, which is not practical. On the other hand, when the thickness of the positive electrode layer 30 exceeds 40 μm, it takes too much time to form the layer, and the productivity is reduced. 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.

Further, as a method of forming the positive electrode layer 30, a known film forming method such as various PVD or various CVD may be used, but it is preferable to use a sputtering method from the viewpoint of production efficiency.

(Solid electrolyte layer)
The solid electrolyte layer 40 is a solid thin film made of an inorganic material, and includes an inorganic solid electrolyte capable of moving lithium ions by an externally applied electric field.
Then, the solid electrolyte layer 40 of the present embodiment is stacked on the first solid electrolyte layer 41 and the first solid electrolyte layer 41 that are stacked on the positive electrode layer 30, and is an object to be stacked on the holding layer 50. A second solid electrolyte layer.

[First solid electrolyte layer]
The first solid electrolyte layer 41 of the present embodiment is made of the same Li ₃ PO ₄ as the inorganic solid electrolyte in the positive electrode layer 30.

厚 The thickness of the first solid electrolyte layer 41 can be, for example, 5 nm or more and 50 nm or less. When the thickness of the first solid electrolyte layer 41 is less than 5 nm, current leakage between the positive electrode layer 30 and the holding layer 50 easily occurs in the obtained lithium ion secondary battery 1. On the other hand, when the thickness of the first solid electrolyte layer 41 exceeds 50 nm, the internal resistance of the battery increases, which is disadvantageous for high-speed charging and discharging.

Further, as a method for manufacturing the first solid electrolyte layer 41, a known film forming method such as various PVD or various CVD may be used, but from the viewpoint of production efficiency, it is preferable to use a sputtering method.

[Second solid electrolyte layer]
The second solid electrolyte layer 42 of the present embodiment includes LiPON (Li ₃ PO _4-x N _x (0 <x) in which a part of oxygen in Li ₃ PO ₄ constituting the first solid electrolyte layer 41 is substituted with nitrogen. <1)).

厚 The thickness of the second solid electrolyte layer 42 can be, for example, 10 nm or more and 10 μm or less. If the thickness of the second solid electrolyte layer 42 is less than 10 nm, current leakage between the positive electrode layer 30 and the holding layer 50 tends to occur in the obtained lithium ion secondary battery 1. On the other hand, if the thickness of the second solid electrolyte layer 42 exceeds 10 μm, the internal resistance of the battery increases, which is disadvantageous for high-speed charging and discharging.

Further, as a method for manufacturing the second solid electrolyte layer 42, a known film forming method such as various PVD or various CVD may be used, but from the viewpoint of production efficiency, it is preferable to use a sputtering method.

[Relationship between first solid electrolyte layer and second solid electrolyte layer]
Thus, in the present embodiment, the first solid electrolyte layer 41 is made of Li ₃ PO ₄ and the second solid electrolyte layer 42 is made of LiPON. That is, both the first solid electrolyte layer 41 and the second solid electrolyte layer 42 contain lithium, phosphorus, and oxygen, respectively.
Here, the volume resistivity of Li ₃ PO ₄ forming the first solid electrolyte layer 41 is higher than that of LiPON forming the second solid electrolyte layer 42. Therefore, in the solid electrolyte layer 40 of the present embodiment, the side provided with the first solid electrolyte layer 41 in contact with the positive electrode layer 30 is closer to the side provided with the second solid electrolyte layer 42 in contact with the holding layer 50. Also, the resistance value per unit thickness is high.

Regarding the relationship between the thickness of the first solid electrolyte layer 41 and the thickness of the second solid electrolyte layer 42, whichever may be thicker or the same. However, from the viewpoint of suppressing an increase in the internal resistance of the battery, it is preferable that the thickness of the first solid electrolyte layer 41 be smaller than the thickness of the second solid electrolyte layer 42, in the order of two digits or more. More preferably, it is reduced.

(Holding layer)
The holding layer 50 as an example of a metal layer is a solid thin film and has a function of holding lithium ions during charging and abandoning lithium ions during discharging. Here, the point that the holding layer 50 of the present embodiment does not include the negative electrode active material itself and is configured to hold lithium functioning as the negative electrode active material therein is different from a general negative electrode layer. Is different.

The holding layer 50 of the present embodiment has a porous structure, and is constituted by a porous portion (not shown) in which a large number of holes are formed. The porousization of the holding layer 50, that is, the formation of the porous portion is performed in accordance with the first charge / discharge operation after the film formation, and the details thereof will be described later.

材料 As a material for forming the holding layer 50, a platinum group element (Ru, Rh, Pd, Os, Ir, Pt), gold (Au), or an alloy thereof can be used. Among these, it is desirable that the holding layer 50 be made of platinum or gold that is less likely to be oxidized. Further, the holding layer 50 of the present embodiment can be made of a polycrystal of the above-mentioned noble metal or an alloy thereof.

Here, in the present embodiment, the holding layer 50 is made of platinum.

The thickness of the holding layer 50 can be, for example, not less than 10 nm and not more than 40 μm. When the thickness of the holding layer 50 is less than 10 nm, the ability to hold lithium becomes insufficient. On the other hand, if the thickness of the holding layer 50 exceeds 40 μm, the internal resistance of the battery increases, which is disadvantageous for high-speed charging and discharging. 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.

Further, as a method of manufacturing the holding layer 50, a known film forming method such as various PVD or various CVD may be used, but from the viewpoint of production efficiency, it is preferable to use a sputtering method. As a method for manufacturing the porous holding layer 50, it is desirable to employ a method of performing charging and discharging, as described later.

(Diffusion prevention layer)
The diffusion prevention layer 60 is a solid thin film and is for suppressing the diffusion of lithium ions held in the holding layer 50 to the outside of the lithium ion secondary battery 1.
As the diffusion preventing layer 60, a material having an amorphous structure and made of a metal or an alloy can be used. The diffusion prevention layer 60 is preferably made of a metal or an alloy that does not form an intermetallic compound with lithium. Among them, from the viewpoint of corrosion resistance, chromium (Cr) alone or an alloy containing chromium is preferable. Is preferred. The diffusion preventing layer 60 may be formed by laminating a plurality of amorphous layers having different constituent materials (for example, a laminated structure of an amorphous chromium layer and an amorphous chromium titanium alloy layer). Further, the “amorphous structure” in the present embodiment includes not only a structure having an amorphous structure as a whole but also a structure in which microcrystals are precipitated in the amorphous structure. .

Here, in the present embodiment, the diffusion preventing layer 60 is made of an alloy of chromium and titanium (CrTi). Examples of the metal (alloy) that can be used for the diffusion preventing layer 60 include, in addition to CrTi, ZrCuAlNiPdP, CuZr, FeZr, TiZr, CoZrNb, NiNb, NiTiNb, NiP, CuP, NiPCu, NiTi, CrTi, AlTi, FeSiB. , AuSi, and the like.

The thickness of the diffusion preventing layer 60 can be, for example, 10 nm or more and 40 μm or less. When the thickness of the diffusion prevention layer 60 is less than 10 nm, it is difficult for the diffusion prevention layer 60 to block lithium that has passed through the holding layer 50 from the solid electrolyte layer 40 side. On the other hand, if the thickness of the diffusion prevention layer 60 exceeds 40 μm, the internal resistance of the battery increases, which is disadvantageous for high-speed charging and discharging.

Further, as a method of manufacturing the diffusion preventing layer 60, a known film forming method such as various PVD or various CVD may be used, but from the viewpoint of production efficiency, it is preferable to use a sputtering method. In particular, when the diffusion prevention layer 60 is made of the above-described chromium-titanium alloy, the chromium-titanium alloy tends to be amorphous when the sputtering method is employed.

(Negative electrode current collector layer)
The negative electrode current collector layer 70 is a solid thin film having electron conductivity, and has a function of collecting current to the holding layer 50. Here, the material constituting the negative electrode current collector layer 70 is not particularly limited as long as it has electron conductivity, and various metals and conductive materials including alloys of various metals may be used. it can. However, from the viewpoint of suppressing corrosion of the diffusion preventing layer 60, it is preferable to use a chemically stable material, for example, a platinum group element (Ru, Rh, Pd, Os, Ir, Pt) or gold. (Au) or an alloy thereof is preferable.

Here, in the present embodiment, negative electrode current collector layer 70 is made of the same platinum as holding layer 50. However, unlike the holding layer 50, the negative electrode current collector layer 70 does not have a porous structure.

厚 The thickness of the negative electrode current collector layer 70 can be, for example, not less than 5 nm and not more than 50 μm. If the thickness of the negative electrode current collector layer 70 is less than 5 nm, the corrosion resistance and the current collecting function will be reduced, which is not practical. On the other hand, if the thickness of the negative electrode current collector layer 70 exceeds 50 μm, the internal resistance of the battery increases, which is disadvantageous for high-speed charging and discharging.

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

[Method of manufacturing lithium ion secondary battery]
Next, a method for manufacturing the above-described lithium ion secondary battery 1 will be described.
FIG. 2 is a flowchart illustrating a method of manufacturing the lithium ion secondary battery according to the present embodiment.

First, the substrate 10 is mounted on a sputtering device (not shown), and an underlayer forming step of forming the underlayer 20 on the substrate 10 is performed (step 20). Next, a positive electrode layer forming step of forming the positive electrode layer 30 on the base layer 20 is performed by the above-mentioned sputtering apparatus (Step 30). Subsequently, a solid electrolyte layer forming step of forming the solid electrolyte layer 40 on the positive electrode layer 30 is performed by the sputtering device (step 40). Here, in the solid electrolyte layer forming step of Step 40, a first solid electrolyte layer forming step of forming the first solid electrolyte layer 41 on the positive electrode layer 30 is performed (Step 41), and the first solid electrolyte layer 41 is formed on the first solid electrolyte layer 41. A second solid electrolyte layer forming step of forming the second solid electrolyte layer 42 is performed (Step 42). Next, a holding layer forming step of forming the holding layer 50 on the second solid electrolyte layer 42 of the solid electrolyte layer 40 is performed by the sputtering device (step 50). Then, a diffusion prevention layer forming step of forming the diffusion prevention layer 60 on the holding layer 50 is performed by the above-mentioned sputtering apparatus (Step 60). Then, a negative electrode current collector layer forming step of forming the negative electrode current collector layer 70 on the diffusion preventing layer 60 is performed by the sputtering device (step 70). By performing these steps 20 to 70, the basic structure of the lithium ion secondary battery 1 is obtained. Then, the basic structure of the lithium ion secondary battery 1 is removed from the sputtering device.

(4) Next, an initial charging step of performing the first charging of the basic structure of the lithium ion secondary battery 1 removed from the sputtering apparatus is performed (Step 80). Then, an initial discharge step (an example of a discharge step) for performing a first discharge is performed on the charged basic structure of the lithium ion secondary battery 1 (step 90). By these initial charging and initial discharging, the holding layer 50 is made porous, that is, a porous portion and a large number of pores are formed, and the lithium ion secondary battery 1 shown in FIG. 1 is obtained.

[Operation of lithium ion secondary battery]
Now, the operation of the lithium ion secondary battery 1 of the present embodiment will be described in more detail by dividing the operation into a charging operation and a discharging operation.

(Charging operation)
When charging the lithium ion secondary battery 1 in a discharged state, a positive electrode of a DC power supply is connected to the substrate 10 functioning as a positive electrode current collector layer, and a negative electrode of the DC power supply is connected to the negative electrode current collector layer 70, respectively. You. Accordingly, a direct current, that is, a direct current from the substrate 10 to the lithium ion secondary battery 1 through the base layer 20, the positive electrode layer 30, the solid electrolyte layer 40, the holding layer 50, the diffusion prevention layer 60, and the negative electrode current collector layer 70, Charging current flows.

Then, lithium ions 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, the lithium ions move in the thickness direction of the lithium ion secondary battery 1 (upward in FIG. 1).

At this time, the lithium ions that have moved from the positive electrode layer 30 side to the holding layer 50 side are alloyed with the noble metal (platinum in this example) constituting the holding layer 50 (solid solution, formation of an intermetallic compound, or eutectic). I do.

(4) Part of the lithium ions that have entered the holding layer 50 passes through the holding layer 50 and reaches the boundary with the diffusion preventing layer 60. Here, the diffusion prevention layer 60 of the present embodiment is made of a metal or an alloy having an amorphous structure, and has a significantly smaller number of grain boundaries than the holding layer 50 having a polycrystalline structure. ing. For this reason, the lithium ions that have reached the boundary between the holding layer 50 and the diffusion prevention layer 60 are less likely to enter the diffusion prevention layer 60, and thus maintain the state held in the holding layer 50.

(4) Then, in a state where the charging operation has been completed, the lithium ions moved from the positive electrode layer 30 to the holding layer 50 are held by the holding layer 50. At this time, it is considered that the lithium ions that have moved to the holding layer 50 are held by the holding layer 50 by alloying with platinum or by precipitating metallic lithium in the platinum. Therefore, in this state, it can be said that a negative electrode layer made of lithium is formed inside the holding layer 50.

(Discharge operation)
When discharging (using) the charged lithium ion secondary battery 1, the positive electrode of the load is connected to the substrate 10, and the negative electrode of the load is connected to the negative electrode current collector layer 70. Accordingly, a direct current, that is, a direct current from the substrate 10 to the lithium ion secondary battery 1 through the base layer 20, the positive electrode layer 30, the solid electrolyte layer 40, the holding layer 50, the diffusion prevention layer 60, and the negative electrode current collector layer 70, A discharge current flows.

At this time, lithium ions constituting the negative electrode existing inside the holding layer 50 move along the thickness direction (downward in FIG. 1) to the positive electrode layer 30 via the solid electrolyte layer 40, and again 30.

(4) At this time, in the holding layer 50, the alloy of lithium and platinum is dealloyed (dissolution of metallic lithium when metallic lithium is precipitated) with the release of lithium. Then, as a result of dealloying in the holding layer 50, the holding layer 50 is made porous, and becomes a porous portion in which a large number of holes are formed. The porous portion obtained in this manner is substantially composed of a noble metal (platinum in this example). However, when the discharge is completed, the lithium does not disappear inside the holding layer 50, and a part of the lithium that does not move by the discharge operation remains.

[Others]
In the present embodiment, the solid electrolyte layer 40 has a two-layer structure of the first solid electrolyte layer 41 and the second solid electrolyte layer 42, but is not limited to this. For example, by gradually or stepwise inclining the distribution of nitrogen in the solid electrolyte layer 40, the side in contact with the positive electrode layer 30 is set as a layer having a low nitrogen concentration (a layer having a composition close to Li ₃ PO ₄ ) and held. The side in contact with the layer 50 may be a layer having a high nitrogen concentration (a layer having a composition of LiPON). In other words, there may not be a clear boundary between the first solid electrolyte layer 41 and the second solid electrolyte layer 42. In this case, the nitrogen concentration in the chamber may be gradually increased in the solid electrolyte forming step shown in step 40 of FIG. In this case, the concentration of nitrogen on the side of the solid electrolyte layer 40 that contacts the positive electrode layer 30 may not be 0%, but is preferably 0%.

In the present embodiment, the base layer 20, the positive electrode layer 30, the solid electrolyte layer 40, the holding layer 50, the diffusion preventing layer 60, and the negative electrode current collector layer 70 are stacked on the substrate 10 in this order, so that lithium The basic structure of the ion secondary battery 1 was formed. That is, a configuration is adopted in which the positive electrode layer 30 is arranged on the side closer to the substrate 10 and the holding layer 50 is arranged on the side farther from the substrate 10. However, the present invention is not limited to this, and a configuration in which the holding layer 50 is arranged on the side closer to the substrate 10 and the positive electrode layer 30 is arranged on the side farther from the substrate 10 may be adopted. However, in this case, the stacking order of each layer on the substrate 10 is opposite to that described above except for the base layer 20.

Further, in the present embodiment, the holding layer 50 is made of a noble metal, but the present invention is not limited to this. For example, an alloy of aluminum (Al) which forms an intermetallic compound with lithium, or an alloy of aluminum and a noble metal (a platinum group element (Ru, Rh, Pd, Os, Ir, Pt) or gold (Au) or an alloy thereof) is used. Thus, the holding layer 50 can be configured.

Hereinafter, the present invention will be described in more detail based on examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
The present inventor produced ten types (Examples and Comparative Examples) of lithium ion secondary batteries 1 and evaluated the structures and various electrical characteristics of each.

[Example]
First, in the example, the lithium ion secondary battery 1 having the structure shown in FIG. 1 described in the above embodiment was used. That is, in the example, the base layer 20, the positive electrode layer 30, the first solid electrolyte layer 41, the second solid electrolyte layer 42, the holding layer 50, the diffusion prevention layer 60, and the negative electrode current collector layer 70 are formed on the substrate 10 in this order. The lithium ion secondary battery 1 laminated by the above was used.

[Comparative Example]
On the other hand, in the comparative example, three types of lithium ion secondary batteries 1 having different structures of the solid electrolyte layer 40 from the above-described example were used. Hereinafter, these three types of lithium ion secondary batteries 1 will be described as first to third comparative examples, respectively.

(First comparative example)
FIG. 3 is a diagram showing a cross-sectional configuration of the lithium ion secondary battery 1 of the first comparative example. The lithium ion secondary battery 1 of the first comparative example also has a structure in which a plurality of layers are stacked as described in the embodiment, that is, similarly to the lithium ion secondary battery 1 of the example. The same applies to the point that after a basic structure is formed by a so-called film forming process, the structure is completed by an initial charge / discharge operation. The same applies to the lithium ion secondary batteries 1 of Example 2 and Example 3 described later.

The lithium ion secondary battery 1 of the first comparative example shown in FIG. 3 has a base layer 20, a positive electrode layer 30, and a solid electrolyte layer 40 on a substrate 10, similarly to the lithium ion secondary battery 1 of the embodiment shown in FIG. , A holding layer 50, a diffusion prevention layer 60 and a negative electrode current collector layer 70 are laminated in this order. However, the solid electrolyte layer 40 of the first comparative example includes only the second solid electrolyte layer 42 that is stacked on the positive electrode layer 30 and to be stacked with the holding layer 50, and includes the first solid electrolyte layer 41. Not in the embodiment. That is, the solid electrolyte layer 40 in the lithium ion secondary battery 1 of the first comparative example is the same as the embodiment in that the solid electrolyte layer 40 includes the second solid electrolyte layer 42, but does not include the first solid electrolyte layer 41. This is different from the embodiment. As a result, the first comparative example is different from the first comparative example in that the second solid electrolyte layer 42 is stacked on the positive electrode layer 30.

(Second comparative example)
FIG. 4 is a diagram showing a cross-sectional configuration of the lithium ion secondary battery 1 of the second comparative example.
The lithium ion secondary battery 1 of the second comparative example shown in FIG. 4 also has an underlayer 20, a positive electrode layer 30, and a solid electrolyte layer 40 on a substrate 10, similarly to the lithium ion secondary battery 1 of the embodiment shown in FIG. , A holding layer 50, a diffusion prevention layer 60 and a negative electrode current collector layer 70 are laminated in this order. However, the solid electrolyte layer 40 of the second comparative example is stacked on the second solid electrolyte layer 42 and the second solid electrolyte layer 42 that are stacked on the positive electrode layer 30, and is an object to be stacked on the holding layer 50. It differs from the embodiment in that it has a first solid electrolyte layer 41. That is, although the solid electrolyte layer 40 in the lithium ion secondary battery 1 of the second comparative example includes the first solid electrolyte layer 41 and the second solid electrolyte layer 42, the solid electrolyte layer 40 is the same as the embodiment, The difference from the embodiment is that the order is reversed. Further, as a result, in the second comparative example, the second solid electrolyte layer 42 is stacked on the positive electrode layer 30 and the holding layer 50 is stacked on the first solid electrolyte layer 41. different.

(Third comparative example)
FIG. 5 is a diagram showing a cross-sectional configuration of the lithium ion secondary battery 1 of the third comparative example.
The lithium ion secondary battery 1 of the third comparative example shown in FIG. 5 also has an underlayer 20, a positive electrode layer 30, and a solid electrolyte layer 40 on a substrate 10, similarly to the lithium ion secondary battery 1 of the embodiment shown in FIG. , A holding layer 50, a diffusion prevention layer 60 and a negative electrode current collector layer 70 are laminated in this order. However, the solid electrolyte layer 40 of the third comparative example includes a second solid electrolyte layer 42 stacked on the positive electrode layer 30, a first solid electrolyte layer 41 stacked on the second solid electrolyte layer 42, and a first solid electrolyte layer 41. The second embodiment is different from the first embodiment in that the second embodiment is provided with a second solid electrolyte layer 42 which is laminated on the solid electrolyte layer 41 and on which the holding layer 50 is laminated. That is, although the solid electrolyte layer 40 in the lithium ion secondary battery 1 of the third comparative example includes the first solid electrolyte layer 41 and the second solid electrolyte layer 42, the solid electrolyte layer 40 corresponds to the embodiment, This embodiment is different from the embodiment in that two solid electrolyte layers 42 are provided and one first solid electrolyte layer 41 is sandwiched between these two second solid electrolyte layers 42.

[Specific Configurations of Examples and Comparative Examples]
Next, a specific configuration of the lithium ion secondary battery 1 according to the example and the comparative example will be described.

[Configuration of Example]
Table 1 shows a configuration of the lithium ion secondary battery 1 according to the example. Table 1 shows the relationship between the name of each layer constituting the lithium ion secondary battery 1 and the material constituting each layer and its thickness. This is the same in Tables 2 to 4 described later. Here, as examples, three types of lithium ion secondary batteries 1 having different thicknesses of the first solid electrolyte layer 41 were prepared. Hereinafter, these are referred to as Examples 1 to 3, respectively.

Now, each of the first to third embodiments will be described.
(Example 1)
In Example 1, stainless steel (more specifically, SUS316L) was used as the substrate 10. The thickness of the substrate 10 was 0.1 mm.
In Example 1, the underlayer 20 made of LiNiO ₂ was formed by using the sputtering method. The thickness of the underlayer 20 was 200 nm.
In Example 1, the positive electrode layer 30 made of LiNiO ₂ and Li ₃ PO ₄ was formed by using the sputtering method. The thickness of the positive electrode layer 30 was 800 nm. The ratio (molar ratio) between LiNiO ₂ and Li ₃ PO ₄ in the positive electrode layer 30 was 73:27.
In Example 1, the first solid electrolyte layer 41 made of Li ₃ PO ₄ was formed by using the sputtering method. The thickness of the first solid electrolyte layer 41 was 11 nm.
In Example 1, the second solid electrolyte layer 42 made of LiPON was formed by using the sputtering method. The thickness of the second solid electrolyte layer 42 was 1980 nm.
In Example 1, the holding layer 50 made of Pt was formed by using the sputtering method. The thickness of the holding layer 50 was 30 nm.
In Example 1, the diffusion preventing layer 60 made of CrTi was formed by using the sputtering method. The thickness of the diffusion prevention layer 60 was 200 nm.
In Example 1, the negative electrode current collector layer 70 made of Pt was formed by using the sputtering method. The thickness of the negative electrode current collector layer 70 was 30 nm.
The basic structure of the lithium ion secondary battery 1 thus obtained was initially charged and discharged to obtain the lithium ion secondary battery 1. Note that the thickness of the holding layer 50 was increased from the initial value of 30 nm by performing the initial charge / discharge.

(Example 2)
In Example 2, the same structure as in Example 1 was adopted except that the thickness of the first solid electrolyte layer 41 was set to 22 nm.

(Example 3)
In Example 3, the same structure as in Example 1 was adopted except that the thickness of the first solid electrolyte layer 41 was set to 33 nm.

[Configuration of First Comparative Example]
Table 2 shows a configuration of the lithium ion secondary battery 1 according to the first comparative example. Here, one type of lithium ion secondary battery 1 was prepared as a first comparative example.

In the first comparative example, the same structure as in Example 1 was adopted except that the first solid electrolyte layer 41 was not provided, in other words, the thickness of the first solid electrolyte layer 41 was set to 0 nm.

[Configuration of Second Comparative Example]
Table 3 shows a configuration of the lithium ion secondary battery 1 according to the second comparative example. Here, three types of lithium ion secondary batteries 1 having different thicknesses of the first solid electrolyte layer 41 were prepared as a second comparative example. Hereinafter, these are referred to as a second comparative example (1) to a second comparative example (3), respectively.

Now, each of the second comparative example (1) to the second comparative example (3) will be described.
(Second comparative example (1))
In the second comparative example (1), the same structure as that of the first example was adopted except that the stacking order of the first solid electrolyte layer 41 and the second solid electrolyte layer 42 in the solid electrolyte layer 40 was reversed. That is, in the second comparative example (1), the thickness of the first solid electrolyte layer 41 was set to 11 nm, which is the same as that of the first embodiment.

(Second comparative example (2))
In the second comparative example (2), a structure similar to that of the second comparative example (1) was adopted, except that the thickness of the first solid electrolyte layer 41 was set to 22 nm, which is the same as that of the second embodiment.

(Second comparative example (3))
In the second comparative example (3), a structure similar to that of the second comparative example (1) was adopted, except that the thickness of the first solid electrolyte layer 41 was set to 33 nm, which is the same as that of the third embodiment.

[Configuration of Third Comparative Example]
Table 4 shows a configuration of the lithium ion secondary battery 1 according to the third comparative example. Here, as a third comparative example, three types of lithium ion secondary batteries 1 having different thicknesses of the first solid electrolyte layer 41 were prepared. Hereinafter, these are referred to as third comparative example (1) to third comparative example (3), respectively.

Now, each of the third comparative example (1) to the third comparative example (3) will be described.
(Third comparative example (1))
The third comparative example (1) has the same structure as that of the first embodiment except that the solid electrolyte layer 40 has a three-layer structure of a second solid electrolyte layer 42, a first solid electrolyte layer 41, and a second solid electrolyte layer 42. It was adopted.
In the third comparative example (1), one of the second solid electrolyte layers 42 stacked on the positive electrode layer 30 has a thickness of 1000 nm, and the other second solid electrolyte layer 42 to be stacked on the holding layer 50. Was also 1000 nm thick. That is, the total thickness (2000 nm) of the second solid electrolyte layer 42 was made substantially the same as the thickness (1980 nm) in Examples 1 to 3, the first comparative example, and the second comparative example.
In the third comparative example (1), the thickness of the first solid electrolyte layer 41 sandwiched between the two second solid electrolyte layers 42 was set to 11 nm, which is the same as in the first embodiment.

(Third comparative example (2))
In the third comparative example (2), a structure similar to that of the third comparative example (1) was employed, except that the thickness of the first solid electrolyte layer 41 was set to 22 nm, which is the same as that of the second embodiment.

(Third comparative example (3))
In the third comparative example (3), a structure similar to that of the third comparative example (1) was adopted, except that the thickness of the first solid electrolyte layer 41 was set to 33 nm, which is the same as that of the third embodiment.

[Evaluation of lithium ion secondary battery]
Here, the crystal structure of each part of the lithium ion secondary battery 1 and the electrical characteristics were used as a scale for evaluating each lithium ion secondary battery 1 of the example and the comparative example.

(Crystal structure)
First, the crystal structure will be described. The inventor measured the electron diffraction pattern of each of the lithium ion secondary batteries 1 of Examples and Comparative Examples, and found that the crystal structure (crystallized, amorphous) of each layer constituting the lithium ion secondary battery 1 was measured. Quality).

In the lithium ion secondary batteries 1 of Examples 1 to 3, the substrate 10, the holding layer 50, and the negative electrode current collector layer 70 were each crystallized. In contrast, the underlayer 20, the first solid electrolyte layer 41, the second solid electrolyte layer 42, and the diffusion prevention layer 60 were amorphous. In the positive electrode layer 30, a crystallized region and an amorphous region were mixed, and a crystallized region was scattered with respect to the amorphous region.
Further, each layer constituting the lithium ion secondary battery 1 of the first comparative example constitutes the lithium ion secondary battery 1 of the above-described Examples 1 to 3, except that the first solid electrolyte layer 41 does not exist. It had the same crystal structure as each layer.
Further, the lithium ion secondary batteries 1 of the second comparative example (1) to the second comparative example (3) and the third comparative example 1 to the third comparative example (3) also have the lithium ion secondary batteries 1 of the first to third examples. The crystal structure was the same as each layer constituting the ion secondary battery 1.

(Electrical characteristics)
Next, electrical characteristics will be described. The present inventor evaluated each of the lithium ion secondary batteries 1 of Examples and Comparative Examples with respect to discharge capacity, capacity retention ratio, and internal resistance. Table 5 shows the relationship between the thickness of the first solid electrolyte layer 41 and the respective electrical characteristics (discharge capacity, capacity retention ratio and internal resistance) of each of the examples and comparative examples.

Here, each of the discharge capacity, the capacity retention ratio, and the internal resistance will be described.
(Discharge capacity)
The discharge capacity represents the amount of electricity discharged from the lithium ion secondary battery 1 from the start of use (start of discharge) after the completion of charging to the end of use (end of discharge), and the discharge current (discharge current) It can be obtained by multiplying the time until the discharge end voltage is reached. In this case, the larger the value of the discharge capacity, the better. Here, the charge / discharge characteristics of each lithium ion secondary battery 1 of each of the examples and comparative examples were measured, and the discharge capacity was evaluated based on the results. As a device for measuring the charge and discharge characteristics, a charge and discharge device HJ1020mSD8 manufactured by Hokuto Denko KK was used. Here, the current during charging (charging current) and the current during discharging (discharge current) were 0.6 (mA) and 20 (mA), respectively. In Table 5, the former is described as “$ 0.6 mA” and the latter is described as “$ 20 mA”.

[Capacity maintenance rate]
The capacity retention ratio is a percentage of the capacity of the lithium ion secondary battery 1 at the time when a predetermined period has elapsed with respect to the initial capacity after the completion of charging. In this case, the higher the value of the capacity retention ratio, the better, and the value is 100% at the maximum. Here, the capacity retention rate after full charge and after 3 hours was measured. In Table 5, it was described as "$ 3 hours later".

(Internal resistance)
The internal resistance is an electric resistance existing inside the lithium ion secondary battery 1. In this case, the smaller the value of the internal resistance, the better. Here, the internal resistance when a discharge current of 20 (mA) was passed was measured. In Table 5, it is described as “$ 20 mA”.

[About the third comparative example (1)]
As shown in Table 5, in the lithium ion secondary battery 1 of the third comparative example (1), the internal short-circuit, that is, the short-circuit occurred, so that the discharge capacity could not be measured. Accordingly, the capacity retention ratio and the internal resistance could not be measured.

(Comparison of evaluation results)
Subsequently, with reference to Table 5, the evaluation results of each example and each comparative example are compared. Here, first, a comparison between the example and the first comparative example, a comparison between the example and the second comparative example, and a comparison between the example and the third comparative example are performed. After that, a comparison is made between the first embodiment, the second embodiment, and the third embodiment.

[Comparison between Example and First Comparative Example]
Now, an example and a first comparative example will be compared.
First, the example had a smaller discharge capacity value at 0.6 mA than the first comparative example.
Further, in the example, the value of the discharge capacity at 20 mA was larger than in the first comparative example.
Further, the example had a higher capacity retention ratio than the first comparative example.
In the example, the value of the internal resistance was smaller than in the first comparative example.

[Comparison between Example and Second Comparative Example]
Next, an example and a second comparative example will be compared.
First, the example had a smaller discharge capacity value at 0.6 mA than the second comparative example.
Further, in the example, the value of the discharge capacity at 20 mA was larger than that in the second comparative example.
Further, the example had a higher capacity retention ratio than the second comparative example.
In the example, the value of the internal resistance was smaller than in the second comparative example.

[Comparison between Example and Third Comparative Example]
Subsequently, the example and the third comparative example (except for the third comparative example (1)) will be compared.
First, in the example, the value of the discharge capacity at 0.6 mA was almost the same as the third comparative example.
Further, in the example, the value of the discharge capacity at 20 mA was larger than that of the third comparative example.
Further, the example had a higher capacity retention ratio than the third comparative example.
In the example, the value of the internal resistance was smaller than that in the third comparative example.

[Comparison of Example 1, Example 2, and Example 3]
This time, the first embodiment, the second embodiment, and the third embodiment are compared. Here, first, Example 1 and Example 2 are compared, and then Example 2 and Example 3 are compared.

[Comparison between Example 1 and Example 2]
Now, a comparison between the first embodiment and the second embodiment will be made.
First, in Example 2, the value of the discharge capacity at 0.6 mA was larger than that in Example 1 (about 107%).
Further, in Example 2, the value of the discharge capacity at 20 mA was smaller than that in Example 1 (about 93%).
Furthermore, Example 2 had a higher capacity retention ratio than Example 1 (about 101%).
In Example 2, the value of the internal resistance was larger than that in Example 1 (about 159%).

[Comparison between Example 2 and Example 3]
Next, a comparison between the second embodiment and the third embodiment will be made.
First, in Example 3, the value of the discharge capacity at 0.6 mA was smaller than that in Example 2 (about 99%).
Example 3 had a smaller discharge capacity value at 20 mA than Example 2 (about 94%).
Furthermore, Example 3 had a higher capacity retention ratio than Example 2 (about 101%).
In Example 3, the value of the internal resistance was larger than that in Example 2 (about 107%).

[Overall trends]
From the above, it can be said that the following trends are observed with respect to the discharge capacity, the capacity retention ratio, and the internal resistance.

First, with respect to the discharge capacity at 0.6 mA, although there is some magnitude relationship, in the example and all of the first to third comparative examples, the discharge capacity was on the order of 500 μAh (third example (1)). The same applies hereinafter).

放電 In addition, the discharge capacity at 20 mA was more than one order of magnitude larger than the first comparative example to the third comparative example and was on the order of 100 μA (actually 140 μA or more).

Furthermore, the capacity retention ratio of the example was higher than that of the first comparative example to the third comparative example, and exceeded 98%. In particular, in Example 3 in which the first solid electrolyte layer 41 was the thickest among Examples 1 to 3, the capacity retention ratio was 100%, which is the highest value. Further, among Examples 1 to 3, even in Example 1 in which the first solid electrolyte layer 41 was the thinnest, the capacity retention ratio was 98.6%, which was higher than that in the first comparative example (98%).

And, as for the internal resistance, the example was smaller than the first to third examples and less than 30Ω. In particular, in Example 1 of Examples 1 to 3, in which the first solid electrolyte layer 41 was the thinnest, the internal resistance was 17Ω, which was the lowest value.

As described above, the solid electrolyte layer 40 has a two-layer structure of the first solid electrolyte layer 41 made of Li ₃ PO ₄ and the second solid electrolyte layer 42 made of LiPON, and the first solid electrolyte layer 41 is provided on the positive electrode layer 30 side. It can be seen that by arranging the second solid electrolyte layers 42 on the holding layer 50 side, respectively, it is possible to suppress a decrease in the capacity retention ratio. It can also be seen that the adoption of such a structure can suppress an increase in internal resistance.

DESCRIPTION OF SYMBOLS 1 ... lithium ion secondary battery, 10 ... board | substrate, 10a ... front surface, 10b ... back surface, 20 ... base layer, 30 ... positive electrode layer, 40 ... solid electrolyte layer, 41 ... 1st solid electrolyte layer, 42 ... 2nd solid electrolyte Layer, 50: holding layer, 60: diffusion preventing layer, 70: negative electrode current collector layer

Claims

A positive electrode layer containing a positive electrode active material,
A first solid electrolyte layer containing Li 3 PO 4 ,
A second solid electrolyte layer containing LiPON in which part of oxygen in Li 3 PO 4 has been replaced with nitrogen,
A lithium ion secondary battery having, in order, a negative electrode layer containing a negative electrode active material.
The lithium ion secondary battery according to claim 1, wherein the thickness of the first solid electrolyte layer is smaller than the thickness of the second solid electrolyte layer.
The lithium ion secondary battery according to claim 1, wherein the first solid electrolyte layer and the second solid electrolyte layer each have an amorphous structure.
The positive electrode layer includes LiNiO 2 and Li 3 PO 4 ,
4. The lithium ion according to claim 1, wherein the molar ratio of LiNiO 2 to Li 3 PO 4 in the positive electrode layer is in the range of 9: 1 to 3: 2. Rechargeable battery.
A positive electrode layer containing a positive electrode active material,
A solid electrolyte layer containing lithium (Li), phosphate (PO 4 3- ) and nitrogen (N);
A negative electrode layer containing a negative electrode active material in order,
The solid electrolyte layer,
A lithium ion secondary battery, wherein the concentration of nitrogen on the side facing the positive electrode layer is lower than the concentration of nitrogen on the side facing the negative electrode layer.
6. The lithium ion secondary battery according to claim 5, wherein the solid electrolyte layer has a nitrogen concentration on the side facing the positive electrode layer of 0%. 7.
A positive electrode current collector layer made of a metal or an alloy,
An underlayer containing LiNiO 2 and no Li 3 PO 4 ;
A composite positive electrode layer containing LiNiO 2 and Li 3 PO 4 ;
A first solid electrolyte layer containing Li 3 PO 4 and not containing LiNiO 2 ;
A second solid electrolyte layer containing LiPON in which part of oxygen in Li 3 PO 4 has been replaced with nitrogen,
A lithium ion secondary battery having, in order, a negative electrode layer containing a negative electrode active material.
On the second solid electrolyte layer, a metal layer composed of a platinum group element (Ru, Rh, Pd, Os, Ir, Pt), gold (Au), aluminum (Al), or an alloy thereof is laminated. ,
The lithium ion secondary battery according to claim 7, wherein the negative electrode layer is made of lithium alloyed with a metal constituting the metal layer.