WO2020075352A1 - Lithium ion secondary cell, and method for manufacturing lithium ion secondary cell - Google Patents

Abstract

A lithium ion secondary cell 100 comprises: a battery unit 1 obtained by layering, on a substrate 10 that has electroconductivity and also serves as a positive electrode collector layer, a base layer 20, a positive electrode layer 30, a solid electrolyte layer 40, a holding layer 50, a diffusion prevention layer 60, and a negative electrode collector layer 70; and a coating part 2 that has insulating properties and coats the side part of the battery unit 1. The coating part 2 is configured so as not to cover the center part of the top surface of the negative electrode collector layer 70 positioned on the upper side of the battery unit 1, or the rear surface of the substrate 10 positioned on the lower side of the battery unit 1, and these sections are used for electrical connection with the outside.

Description

Lithium ion secondary battery, method of manufacturing lithium ion secondary battery

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

携 帯 With the spread of portable 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 laminated lithium-ion secondary battery has been proposed in which a solid electrolyte (inorganic solid electrolyte) made of an inorganic material is used as the electrolyte, and the positive electrode, the solid electrolyte, and the negative electrode are all thin films. (See Patent Document 1).
Further, in Patent Document 1, a positive electrode layer, a solid electrolyte layer, and a negative electrode layer are laminated on a substrate made of an insulating resin, and the positive electrode layer, the solid electrolyte layer, and the negative electrode layer formed on the substrate are described. It is described that an overall protective film made of an ultraviolet curable resin is formed so as to cover the entire laminated body including the same.

JP, 2010-182448, A

Here, when adopting a configuration having a thin film type battery portion formed on a substrate made of an insulating resin and an entire protective film formed so as to cover the entire battery portion formed on the substrate, For example, it is necessary to make holes in the entire protective film to provide positive and negative electrodes.
An object of the present invention is to simplify the structure of a thin film type lithium ion secondary battery including a solid electrolyte.

The lithium-ion secondary battery of the present invention includes a first current collector layer that is conductive and that collects current, a first polar layer that occludes and releases lithium ions with a first polarity, and a lithium-ion conductive layer. Solid electrolyte layer having an inorganic solid electrolyte exhibiting conductivity, a second polar layer that occludes and releases lithium ions with a second polarity opposite to the first polarity, and has conductivity and current collection. A second current collector layer to be performed, and a battery part that has an insulating property, and a part of the first current collector layer is exposed on one surface side of the battery part and the battery part of the battery part is exposed. On the other surface side, a part of the second current collector layer is exposed, and a coating part that covers the battery part so that the first polar layer, the solid electrolyte layer and the second polar layer are not exposed. Is equipped with.
In such a lithium ion secondary battery, the coating portion may be made of a synthetic resin material.
Further, the coating portion may be made of a photoresist material.
Further, the coating portion may be composed of a cyclized polymer of perfluorobutenyl vinyl ether.
The first current collector layer may be made of SUS316L.
The first current collector layer may be made of a metal material having a surface plated with Ni—P.
From another point of view, from another point of view, the method for manufacturing a lithium ion secondary battery according to the present invention includes a first current collector layer that has conductivity and that collects current. A first polar layer that occludes and releases lithium ions with a polarity, a solid electrolyte layer having an inorganic solid electrolyte exhibiting lithium ion conductivity, and a lithium ion with a second polarity opposite to the first polarity. It has an insulation property with respect to the upper surface of the second current collector layer in the battery part that includes, in order, the second polar layer that occludes and releases and the second current collector layer that has conductivity and collects current. A supplying step of supplying a liquid organic material in a ring shape; a coating step of rotating the battery section in which the liquid organic material is supplied in a ring shape to apply the liquid organic material to the battery section; Heater that heats the liquid organic material applied to the part And it has a door.
In such a method for manufacturing a lithium-ion secondary battery, the liquid organic material is a photoresist material, and the method further comprises an exposure step of exposing the heated liquid organic material over the entire area. You can
The liquid organic material may be a raw material of a cyclized polymer of perfluorobutenyl vinyl ether.

According to the present invention, the structure of a thin film type lithium ion secondary battery including a solid electrolyte can be simplified.

It is a perspective view showing the whole lithium ion secondary battery composition of an embodiment. It is a perspective view of the battery part which comprises a lithium ion secondary battery. (A) is a front view of a lithium ion secondary battery, (b) is a rear view thereof. FIG. 4 is a sectional view taken along line IV-IV of FIGS. (A), (b) is a figure showing an example of section composition of a substrate which constitutes a battery part. 4 is a flowchart for explaining a method of manufacturing a lithium ion secondary battery according to an embodiment. (A), (b) is a figure for explaining the outline of a base layer formation process. (A), (b) is a figure for demonstrating the outline of a positive electrode layer forming process. (A), (b) is a figure for explaining the outline of a solid electrolyte layer formation process. (A), (b) is a figure for demonstrating the outline of a holding layer formation process. (A), (b) is a figure for explaining the outline of a diffusion prevention layer forming process. (A), (b) is a figure for demonstrating the outline of a negative electrode electrical power collector layer forming process. (A), (b) is a figure for explaining the outline of a division process. (A), (b) is a figure which shows the structure of the battery part obtained through the division process. (A), (b) is a figure for explaining the outline of a supply process. (A), (b) is a figure for explaining the outline of a coating process. (A), (b) is a figure for demonstrating the outline of a heating process. (A), (b) is a figure for explaining the outline of an exposure process. (A)-(c) is a figure for demonstrating the outline of a battery-ized process. It is a figure which shows the initial charging / discharging characteristic of the lithium ion secondary battery of embodiment. It is a figure which shows the cycle charge / discharge characteristic of the lithium ion secondary battery of embodiment. It is a figure which shows the discharge capacity maintenance factor of the lithium ion secondary battery of embodiment.

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 perspective view showing the overall configuration of a lithium ion secondary battery 100 of this embodiment. In addition, FIG. 2 is a perspective view of the battery unit 1 that constitutes the lithium-ion secondary battery 100. Furthermore, FIG. 3A is a front view of the lithium ion secondary battery 100, and FIG. 3B is a rear view thereof. Furthermore, FIG. 4 is a IV-IV sectional view (longitudinal sectional view of the lithium-ion secondary battery 100) of FIGS. 3A and 3B.

The lithium-ion secondary battery 100 of the present embodiment includes a battery unit 1 that functions as a rechargeable battery that can be charged and discharged, that is, a secondary battery, and a coating unit 2 that has an insulating property and covers a main part of the battery unit 1. I have it.

(Battery part)
First, the configuration of the battery unit 1 will be described.
The battery unit 1 according to the present embodiment includes a substrate 10, a base layer 20 laminated on the substrate 10, a positive electrode layer 30 laminated on the base layer 20, and a solid electrolyte layer laminated on the positive electrode layer 30. 40 and 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 end portions thereof are directly laminated on the substrate 10, thereby covering the base layer 20 and the positive electrode layer 30 together with the substrate 10. There is. In addition, the lithium ion secondary battery 100 includes a holding layer 50 laminated on the solid electrolyte layer 40, a diffusion preventing layer 60 laminated on the holding layer 50, and a negative electrode collector laminated on the diffusion preventing layer 60. And an electric body layer 70.

〔substrate〕
The substrate 10 as an example of the first current collector layer serves as a base for laminating the base layer 20 to the negative electrode current collector layer 70 by a film forming process. 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. The details of the substrate 10 will be described later.

[Underlayer]
The underlayer 20 is a solid thin film, which enhances the adhesion between the substrate 10 and the positive electrode layer 30, as well as a material (particularly a metal material) forming the substrate 10 and a Li ₃ PO ₄ (phosphorus) forming the positive electrode layer 30. (A lithium oxide: described later in detail) is a barrier for suppressing direct contact.
As the base layer 20, which has electron conductivity, Li ₃ PO ₄ and Li ⁺ unlikely to occur corrosion by (Li-ion) or PO ₄ ^3- (phosphate ions) constituting, formed of a metal or metal compound such as 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 100.

The thickness of the underlayer 20 can be, for example, 5 nm or more and 50 μm or less. When the thickness of the underlayer 20 is less than 5 nm, the function as a barrier is lowered and it becomes impractical. On the other hand, if 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.

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

[Positive electrode layer]
The positive electrode layer 30 as an example of the first polar layer 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). Materials composed of various materials such as oxides, sulfides, and phosphorus oxides containing the above metals can be used. Further, the positive electrode layer 30 may be a composite positive electrode further containing a solid electrolyte.

In the present embodiment, the positive electrode layer 30 is composed of a composite 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. Then, 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 in a state of maintaining each. As a result, in the positive electrode layer 30, one is a matrix (base material) and the other is a filler (particles). 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.

Then, in the present embodiment, as the positive electrode active material forming the positive electrode layer 30, the same LiNiO ₂ as the underlayer 20 is used. 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%).

(4) 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 100 becomes too small, which is not practical. On the other hand, if 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 100 is large, the thickness of the positive electrode layer 30 may be greater than 40 μm.

Further, as a method for 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.
The solid electrolyte layer 40 of the present embodiment is made of the same Li ₃ PO ₄ as the inorganic solid electrolyte in the positive electrode layer 30. Further, the solid electrolyte layer 40 of the present embodiment contains Li ₃ PO ₄ , while LiPON (Li ₃ PO _4-x N _x (0 <x <) in which part of oxygen in Li ₃ PO ₄ is replaced by nitrogen. 1)) is not included.

厚 The thickness of the solid electrolyte layer 40 can be, for example, 400 nm or more and 800 nm or less. When the thickness of the solid electrolyte layer 40 is less than 400 nm, in the obtained lithium ion secondary battery 100, current leakage between the positive electrode layer 30 and the holding layer 50 is likely to occur. On the other hand, if the thickness of the solid electrolyte layer 40 exceeds 800 nm, the internal resistance of the battery increases, which is disadvantageous for high-speed charging and discharging. Further, the thickness of the solid electrolyte layer 40 is preferably, for example, not less than 600 nm and not more than 800 nm.

Here, as for the relationship between the thickness of the positive electrode layer 30 and the thickness of the solid electrolyte layer 40, 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 solid electrolyte layer 40 be smaller than the thickness of the positive electrode layer 30.

Further, as a method for manufacturing the solid electrolyte layer 40, 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.

[Holding layer]
The holding layer 50 as an example of the second polar layer is a solid thin film, and has a function of holding lithium ions during charging and releasing lithium ions during discharging. Here, the point that the holding layer 50 of the present embodiment does not itself include a negative electrode active material and is configured to hold lithium functioning as a 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 the first charge / discharge operation after the film formation, and the details 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), aluminum (Al), or an alloy thereof can be used. Among these, it is desirable that the holding layer 50 be made of platinum or gold, which is less likely to be oxidized. Further, the holding layer 50 of the present embodiment can be made of the above-mentioned noble metal and metal or a polycrystal of 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 100 is large, the thickness of the retaining layer 50 may exceed 40 μm.

Further, as a method for 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 by the holding layer 50 to the outside of the lithium ion secondary battery 100.
As the diffusion prevention layer 60, a layer made of metal or alloy having an amorphous structure 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 these, from the viewpoint of corrosion resistance, chromium (Cr) alone or an alloy containing chromium is preferred. Is preferred. The diffusion prevention 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). The metals (alloys) 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, AlTi, FeSiB, AuSi And the like.

The thickness of the diffusion preventing layer 60 can be, for example, not less than 10 nm and not more than 40 μm. When the thickness of the diffusion preventing layer 60 is less than 10 nm, it is difficult for the lithium that has passed through the holding layer 50 from the solid electrolyte layer 40 side to be blocked by the diffusion preventing layer 60. 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 for 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 preventing layer 60 is made of the above-described chromium titanium alloy, if the sputtering method is adopted, the chromium titanium alloy is likely to become amorphous.

[Negative electrode current collector layer]
The negative electrode current collector layer 70 as an example of the second polar layer is a solid thin film having electronic 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 the corrosion of the diffusion prevention 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, the negative electrode current collector layer 70 is made of the same platinum as the 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, and it will not be 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 of manufacturing the negative electrode current collector layer 70, 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.

(Structure of substrate)
Next, the substrate 10 used in the present embodiment will be described.
The substrate 10 of the present embodiment has a rectangular shape (square shape in this example), one surface being a front surface 10a and the other surface being a back surface 10b. The substrate 10 of this embodiment is made of a conductive material having electronic conductivity. As a result, the substrate 10 of the present embodiment functions as a positive electrode current collector layer that collects current to the positive electrode layer 30 via the underlayer 20.

The thickness of the substrate 10 can be, for example, not less than 20 μm and not more than 2000 μm. When the thickness of the substrate 10 is less than 20 μm, the strength of the lithium ion secondary battery 100 may be insufficient. On the other hand, if the thickness of the substrate 10 exceeds 2000 μm, the volume energy density and the weight energy density decrease due to the increase in the thickness and weight of the battery.

FIG. 5 is a diagram showing a cross-sectional configuration example of the substrate 10 that constitutes the lithium-ion secondary battery 100 of the embodiment. Hereinafter, the substrate 10 shown in FIG. 5A will be referred to as a first configuration example, and the substrate 10 shown in FIG. 5B will be referred to as a second configuration example.

[First Configuration Example]
In the first configuration example shown in FIG. 5A, the substrate 10 includes a base material 11 formed of a single-layer metal plate.
In the first configuration example, various metals, alloys thereof, or the like can be used as the metal material forming the base material 11. Here, in the first configuration example, it is desirable to use stainless steel as the substrate 11 from the viewpoint of suppressing corrosion caused by phosphoric acid, and particularly from the viewpoint of suppressing intergranular corrosion, It is desirable to use SUS316, more preferably SUS316L. When LiNiO ₂ is used as the underlayer 20 laminated on the substrate 10 as in the present embodiment, stainless steel whose coefficient of thermal expansion is close to that of LiNiO ₂ is used as the metal material forming the base material 11. Is preferred. Furthermore, when the substrate 10 is also used as the positive electrode current collector layer as in the present embodiment, as the metal material forming the base material 11, stainless steel that is resistant to corrosion even under a high voltage environment and is resistant to over-discharge. Is preferably used.
In the first configuration example, the base material 11 forming the substrate 10 is not limited to a single-layer metal plate, and may be formed of a laminate of a plurality of metal plates.

[Second Configuration Example]
In the second configuration example shown in FIG. 5B, the substrate 10 includes a base material 11 formed of a single-layer metal plate and a coating layer 12 that covers the entire surface of the base material 11.
In the second configuration example, as the metal material forming the base material 11, various metals, their alloys, metal compounds, and the like can be used. Here, in the second configuration example, it is desirable to use aluminum as the base material 11 from the viewpoint of suppressing corrosion caused by lithium.
Note that, in the second configuration example, the base material 11 is not limited to a single-layer metal plate, and may be formed of a laminate of a plurality of metal plates.

Further, in the second configuration example, as a material forming the coating layer 12, various metals, their alloys, metal compounds, or the like can be used. Here, when the substrate 10 in which the coating layer 12 is formed on the base material 11 is adopted, from the viewpoint of suppressing corrosion caused by lithium, CrTi, ZrCuAlNiPdP, CuZr, FeZr, TiZr, CoZrNb, NiNb, It is preferable to use NiTiNb, NiP, CuP, NiPCu, NiTi, AlTi, FeSiB, AuSi, or the like. Among these, from the viewpoint of providing a hard outer peripheral surface capable of mechanical polishing, for example, NiP (nickel-phosphorous, hereinafter referred to as “Ni-P”) formed by an electroless nickel plating method. May be used).
However, the method for forming the coating layer 12 is not limited to the plating method, and various film forming methods may be employed.

In the example shown in FIG. 5B, the substrate 10 is formed by covering the entire surface of the base material 11 with the coating layer 12, but the present invention is not limited to this. For example, when the battery structure is formed only on the surface 10a of the substrate 10 as in the present embodiment (see FIG. 4), the coating layer 12 is formed on at least the side of the substrate 11 that becomes the surface 10a. It should be provided.

[Maximum minimum height difference]
Next, the maximum and minimum height difference Rmm of the substrate 10 of the present embodiment will be described.
The maximum / minimum height difference Rmm is a measure for defining the smoothness of the laminated surface of the battery structure on the substrate 10 (the surface 10a of the substrate 10 in the present embodiment). The maximum-to-minimum height difference Rmm in the present embodiment is the height between the maximum height and the minimum height obtained by measuring irregularities in a range of 20 μm × 20 μm (square region) with an AFM (Atomic Force Microscope). Defined by the difference. Therefore, the definition of the maximum and minimum height difference Rmm is different from the maximum height Rz defined in, for example, JIS B0601.

Now, the definition of the maximum and minimum height difference Rmm will be described in more detail.
The maximum / minimum height difference Rmm in the present embodiment is obtained, for example, by using a Bruker D3100, which is an AFM device (atomic force microscope system), and after acquiring data in a region of 20 μm × 20 μm, a reference plane for each scan line. When creating, use a cubic expression as an approximation polynomial, prepare an image that has been converted (“smoothed”) into displacement from the reference plane (+ displacement and −displacement may exist), It can be obtained by the "maximum value-minimum value" of the direction (z displacement).

In the present embodiment, the maximum and minimum height difference Rmm of the surface 10a of the substrate 10 is set to 78 nm or less. Here, in the substrate 10 of the first configuration example shown in FIG. 5A, the maximum / minimum height difference Rmm of the base material 11 located on the front surface 10a side is set to 78 nm or less. In the substrate 10 of the second configuration example shown in FIG. 5B, the maximum / minimum height difference Rmm of the coating layer 12 located on the front surface 10a side is set to 78 nm or less.

[Arithmetic mean roughness]
Next, the arithmetic average roughness Ra of the substrate 10 according to the present embodiment will be described.
The arithmetic average roughness Ra is, for example, specified in JIS B 0601.
In the present embodiment, the arithmetic mean roughness Ra of the surface 10a of the substrate 10 is preferably 1.1 nm or less.

(Coating part)
Now, the configuration of the covering portion 2 will be described with reference to FIGS. 1 to 4.
The covering portion 2 of the present embodiment is a solid thin film, which protects the battery portion 1 and performs internal insulation and external insulation of the battery portion 1.

The coating portion 2 includes an upper surface of the negative electrode current collector layer 70, a side surface of the negative electrode current collector layer 70, a side surface of the diffusion prevention layer 60, a side surface of the holding layer 50, an upper surface (end side) and side surfaces of the solid electrolyte layer 40, Also, the side surface of the substrate 10 is covered. However, an opening 2a where the coating 2 does not exist is formed in substantially the center of the upper surface of the negative electrode current collector layer 70, and an exposed portion 71 from which the negative electrode current collector layer 70 is exposed is formed at this portion. It is provided. Further, the covering portion 2 does not cover the lower surface of the substrate 10, and the back surface 10b (see FIG. 5) of the substrate 10 is exposed at this portion. Thereby, in the lithium ion secondary battery 100 of the present embodiment, the exposed portion 71 of the negative electrode current collector layer 70 functions as a negative electrode used for electrical connection with the outside, and the back surface 10b of the substrate 10 is formed. , But functions as a positive electrode used for electrical connection to the outside.

As the covering part 2, various materials such as an organic material and an inorganic material can be used as long as they have insulation properties. However, since the battery unit 1 of the present embodiment has a structure that expands and contracts in the thickness direction with charging and discharging, as will be described later, the covering unit 2 is more flexible and expandable than an inorganic material. It is desirable to use an organic material (particularly a synthetic resin material), which is also expensive. In addition, the covering portion 2 has good adhesion to each layer exposed to the outside of the battery portion 1 (in this example, the substrate 10, the solid electrolyte layer 40, the holding layer 50, the diffusion preventing layer 60, and the negative electrode current collector layer 70). It is desirable to use high materials. Further, from the viewpoint of making it easier to observe the state of the battery unit 1 from the outside of the lithium-ion secondary battery 100, the covering unit 2 has a light-transmitting property with respect to light having a wavelength in the visible region. Is desirable.

And as an inorganic material that can be used as the covering portion 2, for example, silicon oxide (SiO ₂ ) can be cited. Further, as an organic material that can be used as the covering portion 2, a synthetic resin material can be cited, and it is particularly preferable to use various photoresist materials and various engineering plastic materials. Here, the photoresist material may be either a positive type or a negative type, but a positive type is preferable from the viewpoint of simplifying the manufacturing process of the covering portion 2. Further, the engineering plastic material may be either a thermoplastic resin or a thermosetting resin, but from the viewpoint of obtaining high toughness, the thermoplastic resin is desirable. Further, from the viewpoint of ensuring durability against chemicals and electrical insulation, it is preferable to use a fluororesin, and from the viewpoint of obtaining high translucency, it is preferable to use an amorphous fluororesin. More desirable. Examples of the amorphous fluororesin are those obtained by copolymerizing a fluoropolymer of a crystalline polymer to make it amorphous as a polymer alloy, and a perfluorodioxole copolymer (Teflon AF manufactured by DuPont). (Registered trademark)) and a cyclized polymer of perfluorobutenyl vinyl ether (trade name Cytop (registered trademark) manufactured by AGC Co.). Among these, it is preferable to use a cyclized polymer of perfluorobutenyl vinyl ether from the viewpoint of enhancing the adhesion to the battery unit 1.

The thickness of the covering portion 2 can be, for example, 100 nm or more and 2 mm or less. If the thickness of the covering portion 2 is less than 100 nm, there is a high possibility that pinholes and the like will be formed, and Li may be oxidized by exposure to the atmosphere, or insulation may not be ensured. On the other hand, when the thickness of the covering portion 2 exceeds 2 mm, it becomes difficult to reduce the thickness of the lithium-ion secondary battery 100 as a whole, and it takes too much time to form the layer, which lowers the productivity.

Further, as a method for producing the covering portion 2, for example, when an inorganic material is used, a known film forming method such as various PVD or various CVD, or a sol-gel method can be adopted. On the other hand, when an organic material is used, for example, a film forming method in which a liquid raw material is applied by dip coating, spin coating, a brush, or the like and then cured by heating or exposure can be adopted. In addition, when an organic material that has been molded into a solid and sheet shape is used as a raw material, a film forming method in which the raw material is subjected to perforation processing, etc., and then placed on an object and cured by heating is adopted. You can also Here, examples of the solid raw material include a thermosetting epoxy resin sheet (a product of Kyocera Co., Ltd., a melting sheet).

[Method of manufacturing lithium ion secondary battery]
Now, a method for manufacturing the above-described lithium-ion secondary battery 100 will be described.
FIG. 6 is a flowchart for explaining the method of manufacturing lithium-ion secondary battery 100 of the present embodiment.
The lithium-ion secondary battery 100 according to the present embodiment includes a battery part forming step (step 1) of forming the battery part 1, a covering part forming step of forming the covering part 2 on the battery part 1 (step 2), and a battery. It is manufactured through a battery forming step (step 3) of converting the basic structure of the lithium-ion secondary battery 100 in which the cover 2 is formed on the part 1 into a battery. Hereinafter, these three steps will be described in more detail and specifically.

(Battery part formation process)
First, the battery part forming step of step 1 will be described.

[Substrate preparation process]
In the battery part forming process of step 1, first, a substrate preparing process is performed to prepare the substrate 10 that has been surface-treated so that the maximum and minimum height difference Rmm of the surface 10a is 78 nm or less (step 11). Note that, here, the case where four (2 × 2) battery units 1 are formed using one substrate 10 is taken as an example, and the square substrate 10 is prepared.

Here, the substrate 10 according to the first configuration example shown in FIG. 5A is manufactured by the following procedure, for example. First, a metal plate is manufactured by a rolling method or the like, and the surface 10a side of the base material 11 obtained by cutting the metal plate is subjected to a general mechanical polishing treatment, and then further subjected to CMP (Chemical Mechanical Polishing). By performing a precision polishing process using a mechanical polishing method or the like, the substrate 10 in which the maximum and minimum height difference Rmm of the surface 10a is set to 78 nm or less is obtained.

The substrate 10 according to the second configuration example shown in FIG. 5B is manufactured by the following procedure, for example. First, a metal plate is manufactured by a rolling method or the like, and a coating layer 12 made of Ni—P is formed on the entire surface of a base material 11 obtained by cutting the metal plate by an electroless nickel plating method or the like. A laminate of the material 11 and the coating layer 12 is obtained. Then, after performing a general mechanical polishing process on the coating layer 12 positioned on the surface 10a side of the thus obtained laminated body, a polishing process using a CMP method or the like is performed, so that the surface 10a The substrate 10 having the maximum and minimum height difference Rmm set to 78 nm or less is obtained.

[Underlayer forming step]
Then, the substrate 10 is mounted on a sputtering device (not shown), and an underlayer forming step of forming the underlayer 20 on the surface 10a of the substrate 10 is executed (step 12).
FIG. 7 is a diagram for explaining the outline of the step 12 of forming the underlayer. Here, FIG. 7A shows a front view, and FIG. 7B shows a VIIB-VIIB sectional view of FIG. 7A.

In this example, the base layer 20 is formed in a matrix (2 × 2 = 4 places) on the surface 10 a of the substrate 10. At this time, each base layer 20 has a rectangular shape (square shape), and the area of each is set to a common size. Therefore, the area of each underlayer 20 is smaller than the area of the substrate 10 (less than 1/4 in this example). The surface 10a of the substrate 10 is exposed between two adjacent underlayers 20 by providing a gap between the underlayers 20 so that the underlayers 20 do not contact each other. In addition, in the following description, what laminated | stacked the base layer 20 on the board | substrate 10 is called a 1st laminated body.

[Positive electrode layer forming step]
Next, a positive electrode layer forming step of forming the positive electrode layer 30 on the underlayer 20 is executed by the above sputtering apparatus (step 13).
FIG. 8 is a diagram for explaining the outline of the positive electrode layer forming step of step 13. Here, FIG. 8A is a front view and FIG. 8B is a sectional view taken along line VIIIB-VIIIB of FIG. 8A.

In this example, the positive electrode layer 30 is formed on each base layer 20 in the first stacked body. More specifically, the positive electrode layers 30 are formed in a matrix (2 × 2 = 4 places) on the surface of the first stacked body on which the base layer 20 is formed. At this time, each positive electrode layer 30 has a rectangular shape (square shape), and the area of each positive electrode layer 30 is the same as the area of each base layer 20. Then, each positive electrode layer 30 overlaps with each base layer 20, and each positive electrode layer 30 is prevented from directly contacting the substrate 10. In addition, in the following description, what laminated | stacked the base layer 20 and the positive electrode layer 30 on the board | substrate 10 is called a 2nd laminated body.

[Solid electrolyte layer forming step]
Subsequently, a solid electrolyte layer forming step of forming the solid electrolyte layer 40 on the positive electrode layer 30 is executed by the above sputtering device (step 14).
FIG. 9 is a diagram for explaining the outline of the solid electrolyte layer forming step of step 14. Here, FIG. 9A shows a front view, and FIG. 9B shows a sectional view taken along line IXB-IXB of FIG. 9A.

In this example, the solid electrolyte layer 40 is formed on the surface of the second laminated body on which the positive electrode layer 30 is formed. At this time, the solid electrolyte layer 40 has a rectangular shape (square shape), and the area of the solid electrolyte layer 40 is the same as the area of the substrate 10. Then, the solid electrolyte layer 40 is formed so as to cover the surface and the side surface of the positive electrode layer 30, the side surface of the base layer 20, and the region of the surface 10 a of the substrate 10 that is not in contact with the base layer 20. However, the solid electrolyte layer 40 is formed so as not to contact the side surface of the substrate 10 or the back surface 10b. In addition, in the following description, what laminated | stacked the base layer 20-the solid electrolyte layer 40 on the board | substrate 10 is called a 3rd laminated body.

[Holding layer forming step]
Next, a holding layer forming step of forming the holding layer 50 on the solid electrolyte layer 40 is executed by the above-mentioned sputtering apparatus (step 15).
FIG. 10 is a diagram for explaining the outline of the holding layer forming step of step 15. Here, FIG. 10A shows a front view and FIG. 10B shows a sectional view taken along the line XB-XB of FIG. 10A.

In this example, the holding layer 50 is formed in a matrix (2 × 2 = 4 places) on the solid electrolyte layer 40 in the third stacked body. At this time, each holding layer 50 has a rectangular shape (square shape), and the area of each is set to a common size. However, the area of each holding layer 50 is made larger than the area of each of the base layer 20 and each of the positive electrode layers 30 described above. Then, each holding layer 50 is arranged so as to overlap each positive electrode layer 30 when viewed from above, and the entire outer peripheral edge of each holding layer 50 is located outside the entire outer peripheral edge of each positive electrode layer 30. There is. Further, by providing a gap between the holding layers 50 so that the holding layers 50 do not contact each other, the surface of the solid electrolyte layer 40 is exposed between the two adjacent holding layers 50. In addition, in the following description, what laminated | stacked the base layer 20-the holding layer 50 on the board | substrate 10 is called a 4th laminated body.

[Diffusion prevention layer forming step]
Then, the diffusion preventive layer forming step of forming the diffusion preventive layer 60 on the holding layer 50 is executed by the above sputtering apparatus (step 16).
FIG. 11 is a diagram for explaining the outline of the diffusion prevention layer forming step of step 16. Here, FIG. 11A shows a front view, and FIG. 11B shows a sectional view taken along the line XIB-XIB of FIG. 11A.

In this example, the diffusion prevention layer 60 is formed on each holding layer 50 in the fourth stacked body. More specifically, the diffusion prevention layer 60 is formed in a matrix (2 × 2 = 4 places) on the surface of the fourth stacked body on which the holding layer 50 is formed. At this time, each diffusion prevention layer 60 has a rectangular shape (square shape), and the area of each diffusion prevention layer 60 is the same as the area of each holding layer 50. Then, each diffusion preventing layer 60 overlaps with each holding layer 50 so that each diffusion preventing layer 60 does not come into direct contact with the solid electrolyte layer 40. In addition, in the following description, what laminated | stacked the base layer 20-the diffusion prevention layer 60 on the board | substrate 10 is called the 5th laminated body.

[Negative electrode current collector layer forming step]
Then, a negative electrode current collector layer forming step of forming the negative electrode current collector layer 70 on the diffusion prevention layer 60 is executed by the above sputtering apparatus (step 17).
FIG. 12 is a diagram for explaining the outline of the negative electrode current collector layer forming step of step 17. Here, FIG. 12A shows a front view, and FIG. 12B shows a sectional view taken along line XIIB-XIIB of FIG. 12A.

In this example, the negative electrode current collector layer 70 is formed on each diffusion prevention layer 60 in the fifth stacked body. More specifically, the negative electrode current collector layers 70 are formed in a matrix (2 × 2 = 4 places) on the surface of the fifth stacked body on which the diffusion prevention layer 60 is formed. . At this time, each negative electrode current collector layer 70 has a rectangular shape (square shape), and the area of each negative electrode current collector layer 70 is the same as the area of each diffusion prevention layer 60. Then, each negative electrode current collector layer 70 is made to overlap with each diffusion prevention layer 60 so that each negative electrode current collector layer 70 does not come into direct contact with each holding layer 50 or solid electrolyte layer 40. In addition, in the following description, what laminated | stacked the base layer 20-the negative electrode collector layer 70 on the board | substrate 10 is called the 6th laminated body.

The sixth laminated body obtained in this way has a structure in which four battery parts 1 are integrated. Then, this sixth laminated body is removed from the sputtering apparatus.

[Division process]
After that, the sixth laminated body removed from the sputtering apparatus is divided, and a dividing step for obtaining a plurality of (four) battery units 1 is executed (step 18).
FIG. 13 is a diagram for explaining the outline of the dividing process in step 18. Here, FIG. 13A shows a front view and FIG. 13B shows a sectional view taken along the line XIIIB-XIIIB of FIG. 13A.
In addition, FIG. 14 is a diagram showing a configuration of the battery unit 1 obtained through the division process of step 18. Here, FIG. 14A shows a front view, and FIG. 14B shows a sectional view taken along the line XIVB-XIVB of FIG. 14A.

In this example, the battery unit 1 is formed by cutting the sixth laminated body along a plurality (vertical x 1, lateral x 1) of the dividing lines D into individual pieces. More specifically, the sixth laminated body is divided into a plurality of layers (4) by dividing the sixth laminated body so as to include the independent underlayer 20, the positive electrode layer 30, the holding layer 50, the diffusion prevention layer 60, and the negative electrode current collector layer 70. Individual battery parts 1 are obtained. Note that examples of the method for cutting the sixth stacked body include a method using a dicing blade and a method using a laser.

(Coating part forming process)
Subsequently, the covering portion forming step of step 2 will be described.

[Supply process]
In the covering portion forming step of step 2, first, a supplying step of supplying a photoresist, which is a raw material of the covering portion 2, to the battery portion 1 is executed (step 21).
FIG. 15 is a diagram for explaining the outline of the supply process in step 21. Here, FIG. 15A shows a front view, and FIG. 15B shows a sectional view taken along the line XVB-XVB of FIG. 15A.

In this example, the battery unit 1 is mounted on a stage (not shown) of a spin coater so that the negative electrode current collector layer 70 side faces upward. Then, a liquid photoresist 200 (an example of a liquid organic material) is annularly supplied onto the negative electrode current collector layer 70 in the battery unit 1. At this time, the photoresist 200 can be supplied to the battery unit 1 by, for example, dropping. By thus supplying the photoresist 200 in a ring shape, the opening 2a surrounded by the photoresist 200 is formed in the negative electrode current collector layer 70, and this portion is the negative electrode current collector. It becomes the exposed portion 71 in the layer 70.

[Coating process]
Next, a coating process for coating the photoresist 200 supplied in this way on the battery unit 1 is executed (step 22).
FIG. 16 is a diagram for explaining the outline of the coating process in step 22. Here, FIG. 16A shows a front view, and FIG. 16B shows a cross-sectional view taken along the line XVIB-XVIB of FIG. 16A.

In this example, the stage of the spin coater equipped with the battery unit 1 to which the photoresist 200 is supplied is rotated, and the photoresist 200 is radially extended by the centrifugal force. At this time, the photoresist 200 reaches the upper surface of the solid electrolyte layer 40 from the upper surface of the negative electrode current collector layer 70 through each side surface of the negative electrode current collector layer 70, the diffusion prevention layer 60, and the holding layer 50, and , Reach each side surface of the solid electrolyte layer 40 and the substrate 10. That is, the photoresist 200 covers the upper surface and the side surface of the battery unit 1. However, the opening 2a formed by the photoresist 200 on the upper surface of the battery portion 1, that is, the central portion of the upper surface of the negative electrode current collector layer 70 is maintained as it is, and the exposed portion 71 is covered with the negative electrode current collector. Part of the upper surface of the electric body layer 70 is exposed. Further, the lower surface of the battery unit 1, that is, the lower surface of the substrate 10 is not covered with the photoresist 200 and is kept exposed.

[Heating process]
Then, the heating process of heating the photoresist 200 applied to the battery unit 1 in this way is executed (step 23).
FIG. 17 is a diagram for explaining the outline of the heating process of step 23. Here, FIG. 17A shows a front view and FIG. 17B shows a sectional view taken along the line XVIIB-XVIIB of FIG. 17A.

In this example, the battery unit 1 coated with the photoresist 200 is removed from the spin coater stage and mounted on a hot plate (not shown) so that the negative electrode current collector layer 70 side faces upward. Then, the hot plate is operated to heat (bak) the battery unit 1 coated with the photoresist 200. Then, with heating, the organic solvent contained in the photoresist 200 is volatilized, and the photoresist 200 adheres to the battery unit 1. The photoresist may be heated in an oven.

[Exposure process]
Next, an exposure process is performed to expose the photoresist 200 that is thus brought into close contact with the battery unit 1 (step 24).
FIG. 18 is a diagram for explaining the outline of the exposure process in step 24. Here, FIG. 18A shows a front view, and FIG. 18B shows a sectional view taken along the line XVIIIB-XVIIIB of FIG. 18A.

In this example, the photoresist 200 that is brought into close contact with the battery unit 1 is irradiated with light having a wavelength at which the photoresist 200 has sensitivity, over the entire area without particularly interposing a mask or the like. As a result, the photoresist 200 that is brought into close contact with the battery unit 1 is cured by exposure and becomes the solid coating unit 2. As a result, the basic structure of the lithium ion secondary battery 100 having the battery part 1 and the covering part 2 is obtained.

(Battery conversion process)
Finally, the battery conversion process in step 3 will be described.

[First charging process]
In the battery conversion process of step 3, first, the initial charging process is performed to charge the basic structure of the lithium-ion secondary battery 100 in which the battery part 1 is formed with the coating part 2 for the first time (step). 31).

[First discharge process]
Then, the initial discharging process for discharging the basic structure of the charged lithium-ion secondary battery 100 for the first time is performed (step 32). By the first charge and the first discharge, the holding layer 50 is made porous, that is, the porous portion and a large number of pores are formed, and the lithium ion secondary battery 100 shown in FIG. 1 is obtained.

[Making the holding layer porous]
Now, the above-described porous formation of the holding layer 50 will be described in more detail.
FIG. 19 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 its periphery. Here, FIG. 19A shows a state before the first charge (before step 31), and FIG. 19B shows a state after the first charge and before the first discharge (between step 31 and step 32). 19 (c) shows the state after the initial discharge (after step 32), respectively.

{Before first charge}
First, in the state of “before first charge” shown in FIG. 19A, the holding layer 50 is densified. The thickness of the holding layer 50 is the thickness of the holding layer t50, the thickness of the diffusion prevention layer 60 is the thickness of the diffusion prevention layer t60, and the thickness of the negative electrode current collector layer 70 is the thickness of the negative electrode current collector layer. It is t70.

{After initial charge and before initial discharge}
When the lithium-ion secondary battery 100 shown in FIG. 19A is charged (first charging), the substrate 10 (see FIG. 1) has the positive electrode of the DC power source, and the negative electrode current collector layer 70 has the DC power source of the DC power source. The negative electrodes are each connected. Then, as shown in FIG. 19B, lithium ions (Li ⁺ ) forming 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, during the charging operation, lithium ions move in the thickness direction of the lithium ion secondary battery 100 (upward in FIG. 19B).

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 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).

(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 the number of grain boundaries is significantly smaller than that of 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) In the state where the initial charging operation has been completed, the lithium ions that have 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.

Here, as shown in FIG. 19B, in the lithium ion secondary battery 100 after the initial charge and before the initial discharge, the holding layer thickness t50 is after the film formation and before the initial charge shown in FIG. 19A. Than the state of. That is, the volume of the holding layer 50 increases with the first charge. This is considered to be due to the fact that lithium and platinum are alloyed in the holding layer 50. On the other hand, the thickness t60 of the diffusion prevention layer does not substantially change before and after the first charge. That is, the volume of the diffusion prevention layer 60 is not substantially changed by the first charge. This is considered to be due to the fact that lithium hardly enters the diffusion preventing layer 60. This means that the thickness t70 of the negative electrode current collector layer does not substantially change before and after the first charge, that is, the volume of the negative electrode current collector layer 70 does not substantially change before and after the first charge (negative electrode current collector). It is considered that the platinum constituting the electric conductor layer 70 is not made porous and remains dense like the platinum constituting the holding layer 50).

{After first discharge}
When the lithium ion secondary battery 100 shown in FIG. 19B is discharged (first discharge), the substrate 10 (see FIG. 1) has the positive electrode of the load, and the negative electrode current collector layer 70 has the negative electrode of the load. The electrodes are each connected. Then, as shown in FIG. 19C, the lithium ions (Li ⁺ ) held in the holding layer 50 move to the positive electrode layer 30 via the solid electrolyte layer 40. That is, in the discharging operation, lithium ions move in the thickness direction of the lithium ion secondary battery 100 (downward in FIG. 19C) and are retained by the positive electrode layer 30. Along with this, DC current is supplied to the load.

At this time, in the holding layer 50, the alloy of lithium and platinum is dealloyed (dissolution of the 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 51 in which a large number of holes 52 are formed. The porous portion 51 obtained in this way is almost composed of metal (for example, platinum). However, in the state where the first discharge is completed, lithium does not completely disappear inside the holding layer 50, and some lithium which does not move by the discharge operation remains.

Here, as shown in FIG. 19C, in the lithium ion secondary battery 100 after the initial discharge, the holding layer thickness t50 is larger than that after the initial charge and before the initial discharge shown in FIG. 19B. Decrease. This is considered to be due to the fact that the alloy of lithium and platinum is dealloyed in the holding layer 50. This is supported by the fact that the shape of the holes 52 formed in the holding layer 50 by the first discharge is flattened so that the thickness direction is smaller than the plane direction. Further, as shown in FIG. 19C, in the lithium-ion secondary battery 100 after the initial discharge, the holding layer thickness t50 is larger than that after the film formation shown in FIG. 19A and before the initial charge. To do. This is considered to be due to the fact that the holding layer 50 is made porous by the first charging and the first discharging, that is, a large number of holes 52 are formed in the holding layer 50. On the other hand, the thickness t60 of the diffusion prevention layer and the thickness t70 of the negative electrode current collector layer are not substantially changed before and after the first discharge.

[Electrical characteristics of lithium-ion secondary battery]
Next, the electrical characteristics of the lithium ion secondary battery 100 of the present embodiment will be described.

(Configuration of lithium-ion secondary battery)
The specific configuration and manufacturing method of the lithium-ion secondary battery 100 subjected to the evaluation of the electrical characteristics are as shown below.

[Battery section configuration]
An Al substrate plated with NiP was used as the substrate 10. The size of the substrate 10 (when viewed from above: the same hereinafter) was 12 mm × 12 mm, and the thickness was 8 mm.
For the underlayer 20, lithium nickel oxide (LiNiO ₂ ) formed by a sputtering method was used. The size of the underlayer 20 was 8 mm × 8 mm, and the thickness was 200 nm.
For the positive electrode layer 30, lithium nickel oxide (LiNiO ₂ ) and lithium phosphate (Li ₃ PO ₄ ) formed by a sputtering method were used. The weight ratio of lithium nickel oxide (LiNiO ₂ ) to lithium phosphate (Li ₃ PO ₄ ) in the positive electrode layer 30 was LiNiO ₂ : Li ₃ PO ₄ = 80: 20. The size of the positive electrode layer 30 was 8 mm × 8 mm, and the thickness was 800 nm.
For the solid electrolyte layer 40, lithium phosphate (Li ₃ PO ₄ ) formed by a sputtering method was used. The size of the solid electrolyte layer 40 was 12 mm × 12 mm, and the thickness was 1000 nm.
For the holding layer 50, platinum (Pt) formed by the sputtering method was used. The holding layer 50 had a size of 10 mm × 10 mm and a thickness of 60 nm.
A CoZrNb alloy (more specifically, Co ₉₁ Zr ₅ Nb ₄ ) formed by a sputtering method was used for the diffusion prevention layer 60. The diffusion prevention layer 60 had a size of 10 mm × 10 mm and a thickness of 200 nm.
Platinum (Pt) formed by a sputtering method was used for the negative electrode current collector layer 70. The negative electrode current collector layer 70 had a size of 10 mm × 10 mm and a thickness of 60 nm.

[Structure of coating part]
For the coating portion 2, S1813G (manufactured by Rohm and Haas) known as a photoresist material was used. The thickness of the coating portion 2 was 1000 nm.

〔Production method〕
The lithium-ion secondary battery 100 was manufactured according to the manufacturing method shown in FIG. More specifically, each layer of the battery unit 1 was formed by using the sputtering method. The coating portion 2 was obtained by applying the photoresist 200 made of S1813G described above to the battery portion 1 by spin coating, and then performing heating (baking) and exposure.

(Electrical characteristics)
Now, the details of the electrical characteristics used for the evaluation will be described.
This time, "initial charge and discharge characteristics", "cycle charge and discharge characteristics" and "discharge capacity maintenance rate" were adopted as the criteria for evaluation of electrical characteristics. And as a measuring instrument of charge / discharge characteristics, charge / discharge device HJ1020mSD8 manufactured by Hokuto Denko Co., Ltd. was used.

[Initial charge / discharge characteristics]
The initial charge / discharge characteristics are charge / discharge characteristics when the basic structure of the lithium ion secondary battery 100 is repeatedly charged and discharged including initial charging and initial discharging three times (3 cycles). Here, Table 1 shows the evaluation conditions of the initial charge and discharge.

In the charge / discharge test, constant current (CC) charge / discharge was adopted as the charge / discharge method, and the set value of the charge current was set in the range of 0.08 mA (generally 1 C condition) to 2.7 mA. Further, the charging termination condition in charging was set to reach 4.3V. The rest time after charging was 10 minutes. The discharge termination condition in the discharge was set to 2.0V. The rest time after discharge was 10 minutes. The ambient temperature during charging-resting-discharging was 25 ° C.

Also, this time, the charging and discharging currents were set to 80 (μA), 400 (μA), 800 (μA), 1300 (μA) and 2700 (μA), respectively.

FIG. 20 is a diagram showing the initial charge / discharge characteristics of the lithium-ion secondary battery 100 of the present embodiment. 20, the horizontal axis represents the battery capacity (μAh) and the vertical axis represents the battery voltage (V). Further, in FIG. 20, the charging characteristic is shown in the upper right of the figure, and the discharging characteristic is shown in the lower right of the figure.

From FIG. 20, it can be seen that the lithium-ion secondary battery 100 of the present embodiment can be charged / discharged within a charge / discharge current range of 80 (μA) to 2700 (μA).

[Cycle charge / discharge characteristics]
The cycle charge / discharge characteristic is the charge / discharge characteristic when the basic structure of the lithium ion secondary battery 100 is repeatedly charged / discharged. Here, Table 2 shows the evaluation conditions of the cycle charge / discharge.

ㆍ Constant current (CC) charging was adopted as the charging method for the cycle charging of the cycle charge / discharge, and the charging voltage was 4.3 V and the charging current was 0.35 mA. Further, the termination condition of charging in cycle charging was 0.2 hours, and the ambient temperature during charging was 25 ° C. Further, the charging rest time in the cycle charging was 1 minute, and the ambient temperature during the charging rest was 25 ° C.

On the other hand, in the cycle discharge of the cycle charge / discharge, constant current (CC) discharge was adopted as the discharge method, and the discharge voltage was 2.0 V and the discharge current was 0.35 mA. The condition for ending the discharge in the cycle discharge was 0.2 hours, and the ambient temperature during the discharge was 25 ° C. Further, the discharge rest time in the cycle discharge was 1 minute, and the ambient temperature during the discharge rest was 25 ° C.

In this way, the charging / discharging conditions in the cycle charging / discharging are partially different from the charging / discharging conditions in the initial discharging described above. The number of times of charging / discharging in cycle charging was set to 1 time (1 cycle), 500 times (500 cycles) and 1000 times (1000 cycles).

FIG. 21 is a diagram showing the cycle charge / discharge characteristics of the lithium ion secondary battery 100 of the present embodiment. In FIG. 21, the horizontal axis represents the battery capacity (μAh), and the vertical axis represents the battery voltage (V). Further, in FIG. 21, the charging characteristic is shown in the upper right of the figure, and the discharging characteristic is shown in the lower right of the figure.

From FIG. 21, it is found that the lithium-ion secondary battery 100 of the present embodiment can maintain a substantially constant level in the range of 1 to 1000 times of charge / discharge cycles, in other words, the number of charge / discharge cycles. It can be seen that the deterioration of the charge / discharge performance due to the increase of is suppressed.

[Discharge capacity maintenance rate]
The discharge capacity retention ratio is the discharge capacity (n-th time) of the lithium-ion secondary battery 100 when the charge-discharge is performed n times with respect to the discharge capacity (first discharge capacity) when the first charge-discharge is executed. The discharge capacity) of the above is expressed as a percentage. That is, "nth discharge capacity / first discharge capacity" is expressed in percentage. In this case, the higher the discharge capacity retention rate, the better, and the maximum value is 100%.

Also, the discharge capacity retention rate was obtained based on the result of measuring the charge / discharge characteristics according to the evaluation conditions for the cycle charge / discharge characteristics (see Table 2) described above. Here, the number of charge / discharge cycles was 1300 (1300 cycles).

FIG. 22 is a diagram showing the capacity maintenance rate of the lithium-ion secondary battery 100 of the present embodiment. In FIG. 22, the horizontal axis represents the number of times charging and discharging are repeated (the number of cycles), and the vertical axis represents the discharge capacity retention rate (%).

It can be seen from FIG. 22 that the lithium-ion secondary battery 100 of the present embodiment has a lower discharge capacity maintenance rate as the number of charge / discharge cycles increases. However, even when the number of charge / discharge cycles is 1300, the discharge capacity maintenance ratio of the lithium-ion secondary battery 100 of the present embodiment can be secured at about 86%, which means that the charge / discharge cycle increases and decreases. It can be seen that the deterioration of discharge performance can be suppressed.

[Others]
In this embodiment, the underlayer 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 are laminated in this order on the surface 10 a of the substrate 10. Then, the battery unit 1 was configured. 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 configuration 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 the layers on the substrate 10 is opposite to that described above, and the substrate 10 functions as the negative electrode current collector layer 70.

In addition, in the present embodiment, the battery unit 1 includes the substrate 10, 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. The configuration of the battery unit 1 may be changed as appropriate.

Further, in the present embodiment, the case where the coating portion 2 is formed using the photoresist 200 as a raw material has been described as an example, but the present invention is not limited to this. For example, when the covering portion 2 is formed using the product name Cytop (registered trademark) manufactured by AGC Co. as a raw material, the exposure step of step 24 in the covering portion forming step of step 2 is unnecessary. Further, for example, when the covering portion 2 is formed by using a meltable sheet manufactured by Kyocera Co., Ltd. as a raw material, this sheet is subjected to perforation processing corresponding to the opening 2a, and then stacked on the battery portion 1, It suffices to perform heating. Therefore, in this case, the supply step of step 21, the coating step of step 22 and the exposure step of step 24 in the coating portion forming step of step 2 are unnecessary.

DESCRIPTION OF SYMBOLS 1 ... Battery part, 2 ... Covering part, 2a ... Opening part, 10 ... Substrate, 10a ... Front surface, 10b ... Back surface, 11 ... Base material, 12 ... Coating layer, 20 ... Underlayer, 30 ... Positive electrode layer, 40 ... Solid Electrolyte layer, 50 ... Retaining layer, 51 ... Porous part, 52 ... Hole, 60 ... Diffusion preventive layer, 70 ... Negative electrode current collector layer, 71 ... Exposed part, 100 ... Lithium ion secondary battery, 200 ... Photoresist

Claims (9)

1. A solid electrolyte having a first current collector layer having conductivity and collecting current, a first polar layer absorbing and releasing lithium ions with a first polarity, and an inorganic solid electrolyte exhibiting lithium ion conductivity. A layer, a second polar layer that occludes and releases lithium ions with a second polarity opposite to the first polarity, and a second current collector layer that is conductive and that collects current. Battery part that includes in order,
   A part of the first current collector layer having an insulating property is exposed on one surface side of the battery section and a part of the second current collector layer is exposed on the other surface side of the battery section. And a coating part that covers the battery part so that the first polar layer, the solid electrolyte layer, and the second polar layer are not exposed.
2. The lithium ion secondary battery according to claim 1, wherein the coating portion is made of a synthetic resin material.
3. The lithium ion secondary battery according to claim 2, wherein the coating portion is made of a photoresist material.
4. The lithium ion secondary battery according to claim 2, wherein the coating portion is made of a cyclized polymer of perfluorobutenyl vinyl ether.
5. The lithium-ion secondary battery according to any one of claims 1 to 4, wherein the first current collector layer is made of SUS316L.
6. 5. The lithium ion secondary battery according to claim 1, wherein the first current collector layer is made of a metal material having a surface plated with Ni—P.
7. A solid electrolyte having a first current collector layer having conductivity and collecting current, a first polar layer absorbing and releasing lithium ions with a first polarity, and an inorganic solid electrolyte exhibiting lithium ion conductivity. A layer, a second polar layer that occludes and releases lithium ions with a second polarity opposite to the first polarity, and a second current collector layer that is conductive and that collects current. A supplying step of annularly supplying a liquid organic material having an insulating property to the upper surface of the second current collector layer in the battery part including the order;
   Rotating the battery unit in which the liquid organic material is annularly supplied, a coating step of applying the liquid organic material to the battery unit,
   And a heating step of heating the liquid organic material applied to the battery portion.
8. The liquid organic material is a photoresist material,
   The method for manufacturing a lithium ion secondary battery according to claim 7, further comprising an exposure step of exposing the heated liquid organic material over the entire area.
9. The method for producing a lithium ion secondary battery according to claim 7, wherein the liquid organic material is a raw material of a cyclized polymer of perfluorobutenyl vinyl ether.

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