JP2015153588A - Glass electrolyte and all-solid lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass electrolyte capable of enhancing charging/discharging characteristics of a battery and easily forming a sheet from slurry.SOLUTION: The glass electrolyte contains on the basis of oxide 39.8 to 65 mol% of LiO components, 30 to 60 mol% of POcomponents, 0 to 10 mol% of AlOcomponents, and a total of 0.2 to 10 mol% of one or more kinds of components selected from YOcomponents, ScOcomponents, ZrOcomponents, CeOcomponents, and SmOcomponents.

Description

  The present invention relates to a glass electrolyte, and more particularly to a glass electrolyte that is preferably used as a solid electrolyte contained in an electrolyte layer and an electrode layer of an all-solid lithium ion secondary battery.

  An all-solid lithium ion secondary battery that uses an inorganic solid electrolyte and does not use organic substances as an electrode is expected to be a safe battery because there is no risk of leakage of the electrolyte or generation of gas from the organic electrolyte. This all-solid-state lithium ion secondary battery is unlikely to cause side reactions other than the battery reaction as compared with the liquid battery, and therefore can be expected to have a longer life than the liquid battery.

  As an example of the all-solid-state lithium ion secondary battery, a positive electrode layer and a negative electrode layer are laminated on both sides of the electrolyte layer, respectively, and these are subjected to pressure molding or sintering. A solid electrolyte is used for these electrolyte layer, positive electrode layer, and negative electrode layer in order to conduct lithium ions.

  Here, Patent Document 1 discloses a lithium ion conductive amorphous glass as a solid electrolyte having a thickness of 10 nm or more and less than 2 μm.

  Patent Document 2 discloses a lithium ion secondary battery in which an amorphous solid electrolyte and a solid electrolyte containing a crystal phase are used in combination.

Japanese Patent Laid-Open No. 2007-123081 JP 2012-209256 A

The all solid lithium ion secondary battery is manufactured as follows, for example.
First, a positive electrode slurry, a negative electrode slurry, and an electrolyte slurry are prepared. These slurries contain solid electrolyte powder.
Next, after applying these slurries to a substrate using a coating machine, drying and removing the solvent, a positive electrode sheet, a negative electrode sheet, and an electrolyte sheet are produced. Then, an all solid lithium ion secondary battery is manufactured by laminating these sheets and bonding the layers while densifying the layers by firing, pressure molding, or the like.

Here, the solid electrolyte is required to have high lithium ion conductivity. A crystalline solid electrolyte having a crystal having high lithium ion conductivity, such as a ceramic electrolyte or a glass ceramic electrolyte, has high lithium ion conductivity. Therefore, it is preferable to use a crystalline solid electrolyte as the slurry.
However, the crystalline solid electrolyte is difficult to form a good interface with the electrode active material powder during firing or pressure forming. If the electrode active material powder and the solid electrolyte powder cannot form a good interface contact, the lithium ion conduction is impaired and the internal resistance of the battery increases. The same applies to the interface contact between the crystalline solid electrolyte powders in the electrolyte layer.
Therefore, in order to improve the interface contact between the electrode active material powder and the crystalline solid electrolyte powder, or the interface contact between the crystalline solid electrolyte powders, An amorphous glass electrolyte powder that is easily softened is also included separately (see Patent Document 2). Although the glass electrolyte generally has lower lithium ion conductivity than the crystalline solid electrolyte, it penetrates to fill the gap between the crystalline electrolyte powder and the electrode active material powder during firing or pressure molding, The interface contact can be made good, thereby making it possible to reduce the internal resistance of the battery.

  Here, when producing a slurry using the crystalline solid electrolyte powder and the glass electrolyte powder, since the crystalline solid electrolyte powder and the glass electrolyte powder have hydrophilicity, they are dispersed in the slurry. It is necessary to use a polar solvent. In particular, a solvent having a high dielectric constant is preferably used in order to easily disperse these in the slurry and easily form a sheet.

  On the other hand, the conventional glass electrolyte as described above has low resistance to solvents having a high dielectric constant such as water, so that the glass electrolyte itself and specific components contained in the glass electrolyte are eluted into the solvent. When the ion conductivity is lost or the glass component eluted in the solvent when the slurry applied to the substrate is dried is precipitated in a crystalline state, the ion conductivity is impaired. Since the lithium ion conductivity is lowered, there is a problem in that the discharge capacity of the produced all solid lithium ion secondary battery is lowered.

  In addition, there has been a demand for improving the lithium ion conductivity of the glass electrolyte.

  The present invention has been made in view of the above-mentioned problems, and the object of the present invention is to provide a glass electrolyte that can further improve the charge / discharge characteristics of a battery and can easily form a sheet from a slurry. Is to provide.

The present inventors include one or more selected from the group consisting of Y ₂ O ₃ component, Sc ₂ O ₃ component, ZrO ₂ component, CeO ₂ component and Sm ₂ O ₃ component in the glass electrolyte. The inventors have found that the resistance to polar solvents can be increased while the ion conductivity is increased, and the present invention has been completed.

(1) On the oxide basis,
Li ₂ O component from 39.8 to 65 mol%,
P ₂ O ₅ component 30-60 mol%,
Al ₂ O ₃ component 0 to 10 mol% and one or more selected from Y ₂ O ₃ component, Sc ₂ O ₃ component, ZrO ₂ component, CeO ₂ component and Sm ₂ O ₃ component in total 0.2 -10 mol%
Contains glass electrolyte.

(2) The glass electrolyte according to (1), which contains a total of 0.1 to 5 mol% of at least one selected from a ZrO ₂ component and a CeO ₂ component on an oxide basis.

(3) The glass electrolyte according to (1) or (2), which contains 1 to 10 mol% of an Al ₂ O ₃ component based on oxide.

  (4) An all solid lithium ion secondary battery comprising the glass electrolyte according to any one of (1) to (3) in any one of a positive electrode layer, a negative electrode layer, and an electrolyte layer.

_{(5) Li 1 + x +} 2y + z M 2-x-2y A x B z Si z P 3-x O 12 ( wherein, 0 ≦ x ≦ 0.7,0 ≦ y ≦ 0.4,0 ≦ Z ≦ 0.5 M is at least one selected from Zr, Ti, and Ge, A is at least one selected from Al, Y, and Sc, and B is selected from Ca and Mg. An all-solid-state lithium ion secondary battery in which the crystalline solid electrolyte (which is a seed or more) and the glass electrolyte according to any one of (1) to (3) are included in any of the positive electrode layer, the negative electrode layer, and the electrolyte layer .

(6) A crystalline solid electrolyte represented by the general formula Li ₇ La ₃ Zr ₂ O ₁₂ [LLZ] and the glass electrolyte according to any one of (1) to (3) are a positive electrode layer, a negative electrode layer, and an electrolyte. All-solid-state lithium ion secondary battery contained in one of the layers.

According to the present invention, a glass electrolyte capable of achieving both resistance to polar solvents and dispersibility in polar solvents can be obtained, so that the charge / discharge characteristics of the battery can be further improved, and a sheet is formed from the slurry. An easy glass electrolyte can be provided.
In addition, according to the present invention, the glass electrolyte itself has a desired low softening point and improves the contact between the crystalline solid electrolytes and the contact between the crystalline solid electrolyte and the electrode active material. Since the lithium ion conductivity is also improved, a glass electrolyte capable of further improving the charge / discharge characteristics of the battery can be provided in these aspects.

It is a figure which shows the relationship between the weight loss rate of the glass electrolyte of each Example and a comparative example, and the discharge capacity of the all-solid-state lithium ion secondary battery using the composite electrolyte containing a glass electrolyte and a ceramic electrolyte. It is a figure which shows the relationship between the weight loss rate of the glass electrolyte of each Example and a comparative example, and the logarithm of the ionic conductivity of the solid electrolyte substrate which consists of composite electrolytes. It is a schematic diagram of the opening part formed in sheet | seat AG produced in an Example.

Glass electrolyte of the present invention, on an oxide basis, from 39.8 to 65 _mol% of Li ₂ O _component, 30 to 60 mol% of P 2 _{O 5} component, 0-10 mol% of _Al 2 _{O 3} ingredient and A total of 0.2 to 10 mol% of at least one selected from the group consisting of Y ₂ O ₃ component, Sc ₂ O ₃ component, ZrO ₂ component, CeO ₂ component and Sm ₂ O ₃ component is contained. By including at least one of Y ₂ O ₃ component, Sc ₂ O ₃ component, ZrO ₂ component, CeO ₂ component and Sm ₂ O ₃ component in a predetermined content range in the glass electrolyte, the polarity of the glass electrolyte Resistance to solvents is improved. At the same time, the lithium ion conductivity in the glass electrolyte (hereinafter, also simply referred to as “ion conductivity”) can be enhanced to further enhance the charge / discharge characteristics of the all-solid-state lithium ion secondary battery. Can provide.

  Hereinafter, embodiments of the glass electrolyte of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and may be implemented with appropriate modifications within the scope of the object of the present invention. be able to. In addition, although description may be abbreviate | omitted suitably about the location where description overlaps, the meaning of invention is not limited.

  Unless otherwise specified, the content of each component contained in the glass electrolyte of the present invention is expressed in mol% based on the oxide. Here, the “oxide standard” means that the oxides, composite salts, metal fluorides, etc. used as the raw material of the glass electrolyte are all decomposed and converted into oxides when melted. It is the composition which described each component contained in a glass electrolyte by making mol number into 100 mol%.

<Composition of glass electrolyte>
Hereinafter, the component which comprises the glass electrolyte of this invention, and its effect | action are demonstrated.

The Li ₂ O component is an essential component useful for imparting lithium ion conductivity by providing Li ⁺ ion carriers to the glass electrolyte. Therefore, the content of the Li ₂ O component is preferably 39.8%, more preferably 40%, more preferably 45%, and still more preferably 48%.
On the other hand, by making the content of the Li ₂ O component 65% or less, devitrification or crystallization of the glass when the molten glass raw material is cooled can be suppressed, and chemical durability can be enhanced. Therefore, the upper limit of the content of the Li ₂ O component is preferably 65%, more preferably 62%, and still more preferably 60%.

The P ₂ O ₅ component is an essential component useful for the formation of glass and is a component capable of lowering the glass transition point, particularly by containing 30% or more. Therefore, the content of the P ₂ O ₅ component is preferably 30%, more preferably 33%, and still more preferably 35%.
On the other hand, by setting the content of the P ₂ O ₅ component to 60% or less, crystallization of the glass electrolyte due to heat treatment during battery production can be reduced. In addition, when preparing the electrode layer sheet or the electrolyte layer sheet, it becomes difficult to elute the glass components into the solvent in the slurry. As a result, when the slurry is dried, it is eluted into the solvent in the slurry. It can also suppress that the glass component which had been precipitated in a crystalline state. In this way, by suppressing the crystallization of the components eluted in the solvent, the decrease in the ionic conductivity of the positive electrode layer, the negative electrode layer, and the electrolyte layer made from the positive electrode sheet, the negative electrode sheet, and the electrolyte sheet is suppressed. Can do. Therefore, the content of the P ₂ O ₅ component is preferably 60%, more preferably 55%, still more preferably 50%, and still more preferably 48%.

Y ₂ O ₃ component, Sc ₂ O ₃ component, ZrO ₂ component, CeO ₂ component and Sm ₂ O ₃ component contain at least 0.2% in total of one or more selected from these, Resistance of the glass electrolyte to the polar solvent can be increased. As a result, when the slurry is prepared using a polar solvent, it is possible to suppress an extreme decrease in ion conductivity due to elution of the glass component. In addition, this increases the ionic conductivity. Therefore, the total amount of at least one selected from the Y ₂ O ₃ component, Sc ₂ O ₃ component, ZrO ₂ component, CeO ₂ component and Sm ₂ O ₃ component is preferably 0.2%, more preferably 0 0.5%, more preferably 0.8% is the lower limit.
On the other hand, by making the total amount of one or more of these components 10% or less, devitrification or crystals when producing glass electrolyte by melting glass raw materials due to excessive inclusion of these components Can be suppressed. By suppressing these, the yield is easily improved, so that mass production of the glass electrolyte can be facilitated. Further, in the production of an all solid lithium ion secondary battery from a positive electrode sheet, a negative electrode sheet, and an electrolyte sheet, when the glass electrolyte contained in these sheets is softened and cooled by heat treatment, the ionic conductivity due to crystallization is extremely low. Reduction can be suppressed. Moreover, crystal precipitation of the eluted component in the solvent can be suppressed. Therefore, the total amount of at least one of these components is preferably 10%, more preferably 8%, and even more preferably 5%.

Among these components, the resistance to the polar solvent of the glass electrolyte can be further increased by containing at least 0.1% in total of at least one selected from the ZrO ₂ component and the CeO ₂ component. In addition, this increases the ionic conductivity. Therefore, the total amount of one or more selected from the ZrO ₂ component and the CeO ₂ component is preferably 0.1%, more preferably 0.3%, and even more preferably 0.5%.
On the other hand, devitrification due to excessive inclusion of these components can be reduced by making the total amount of one or more of these components 10% or less. In particular, mass production is facilitated by reducing devitrification or crystallization when the glass raw material is melted. Further, in the production of an all-solid-state lithium ion secondary battery, crystallization when the glass electrolyte is softened and cooled can be suppressed, and an extreme decrease in ionic conductivity due to such crystallization can be suppressed. Moreover, crystal precipitation of the eluted component in the solvent can be suppressed. Therefore, the total amount of at least one of these components is preferably 10%, more preferably 8%, and even more preferably 5%.

The ZrO ₂ component is an optional component that can increase the resistance of the glass electrolyte to the polar solvent when it is contained in an amount of more than 0%. Therefore, the content of the ZrO ₂ component is preferably more than 0%, more preferably 0.3%, and even more preferably 0.5%.
On the other hand, devitrification due to excessive inclusion of these components can be reduced by setting the content of ZrO ₂ to 10% or less. In particular, mass production is facilitated by reducing devitrification or crystallization when the glass raw material is melted. Further, in the production of an all-solid-state lithium ion secondary battery, crystallization when the glass electrolyte is softened and cooled can be suppressed, and an extreme decrease in ionic conductivity due to such crystallization can be suppressed. Furthermore, it is possible to suppress crystal precipitation of the eluted component in the solvent. Accordingly, the upper limit of the content of ZrO ₂ is preferably 10%, more preferably 8%, and still more preferably 5%.

The CeO ₂ component is an optional component that can increase the resistance of the glass electrolyte to the polar solvent when it is contained in an amount of more than 0%. Therefore, the CeO ₂ component content is preferably more than 0%, more preferably 0.3%, and even more preferably 0.5%.
On the other hand, by making the content of CeO ₂ 10% or less, melting of the raw material can be promoted, and devitrification or crystallization when the molten glass raw material is cooled can be reduced. Accordingly, the CeO ₂ content is preferably 10%, more preferably 8%, and even more preferably 5%.

The Y ₂ O ₃ component is an optional component that can form a stable glass phase and can enhance ion conductivity by partially replacing the Al ₂ O ₃ component described later. Therefore, the lower limit of the Y ₂ O ₃ component is preferably more than 0%, more preferably 0.5%, and even more preferably 1%.
On the other hand, by making the Y ₂ O ₃ component 10% or less, it is possible to suppress a decrease in ion conductivity due to devitrification or crystallization when the molten glass raw material is cooled. Accordingly, the upper limit of the content of the Y ₂ O ₃ component is preferably 10%, more preferably 8%, and even more preferably 5%.

The Sc ₂ O ₃ component is an optional component that can form a stable glass phase and can enhance ion conductivity by partially replacing the Al ₂ O ₃ component described later. Accordingly, the Sc ₂ O ₃ component may preferably have a lower limit of more than 0%, more preferably 0.5%, and even more preferably 1%.
On the other hand, by making the Sc ₂ O ₃ component 10% or less, a decrease in ion conductivity due to devitrification or crystallization when the molten glass raw material is cooled can be suppressed. Accordingly, the content of the Sc ₂ O ₃ component is preferably 10%, more preferably 8%, and even more preferably 5%.

The Sm ₂ O ₃ component is an optional component that can enhance the resistance of the glass electrolyte to the polar solvent when it is contained in an amount of more than 0%. Accordingly, the content of the Sm ₂ O ₃ component is preferably more than 0%, more preferably 0.5%, and even more preferably 1%.
On the other hand, by making the content of the Sm ₂ O ₃ component 10% or less, melting of the raw material can be promoted, and devitrification or crystallization when the molten glass raw material is cooled can be reduced. Therefore, the content of the Sm ₂ O ₃ component is preferably 10%, more preferably 8%, and further preferably 5%.

When the Al ₂ O ₃ component is contained in an amount of more than 0%, the melting point can be lowered and the resistance of the glass electrolyte to the polar solvent can be increased. As a result, it is an optional component that can suppress an extreme decrease in ion conductivity due to elution of the glass component when a slurry is prepared using a polar solvent. Therefore, the content of the Al ₂ O ₃ component is preferably more than 0%, more preferably 1%, and even more preferably 2%.
On the other hand, by making the content of the Al ₂ O ₃ component 10% or less, devitrification or crystallization when the molten glass raw material due to excessive inclusion of the Al ₂ O ₃ component is cooled, A decrease in ionic conductivity due to crystallization due to heat treatment can be suppressed. Moreover, crystal precipitation of the eluted component in the solvent can be suppressed. Accordingly, the upper limit of the content of the Al ₂ O ₃ component is preferably 10%, more preferably 8%, and even more preferably 7%.

The SiO ₂ component is an optional component that facilitates the formation of a glass network structure and promotes the formation of glass when it contains more than 0%.
On the other hand, when the content of the SiO ₂ component is 10% or less, a glass electrolyte having a low glass transition point and a low softening point can be easily obtained. Therefore, the upper limit of the content of SiO ₂ is preferably 10%, more preferably 5%, and still more preferably 3%.

Here, the total amount of the P ₂ O ₅ component and the SiO ₂ component is preferably 60%, more preferably 55%, even more preferably from the viewpoint of reducing devitrification or crystallization when the molten glass raw material is cooled. Is 50%, more preferably 48%.

RO (R is at least one selected from Mg, Ca, and Sr) is an optional component that can lower the melting point and Tg of the glass electrolyte when the total content exceeds 0%.
On the other hand, the fall of the ionic conductivity of a glass electrolyte can be suppressed by making RO into 10% or less in total. Therefore, the total content of RO is preferably 10%, more preferably 8%, more preferably 5%.

When DO ₂ (D is at least one selected from Ti and Ge) exceeds 0% in total, devitrification or crystallization can be suppressed when the molten glass raw material is cooled. , Thereby being an optional component that can suppress degradation of thermal and chemical durability.
On the other hand, by 5% or less of DO ₂ in total, it is suppressing a decrease in ion conductivity due to devitrification at the time of cooling the molten glass raw material. Therefore, the total content of DO ₂ is preferably 5%, more preferably 3%, and still more preferably 1%.

TeO ₂ is an optional component that can lower the melting point and Tg of the glass electrolyte when it is contained in excess of 0%. On the other hand, by making the content of TeO ₂ 10% or less, damage to the crucible when the glass raw material is melted can be reduced. Therefore, the upper limit of the content of TeO ₂ is preferably 10%, more preferably 8%, and still more preferably 6%.

M ′ ₂ O ₃ (where M ′ is one or more selected from In, La, Pr, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) exceeds 0% in total When it contains, it is an arbitrary component which can improve the meltability and devitrification resistance of glass.
On the other hand, from the viewpoint of suppressing an increase in the material cost of the glass electrolyte, the total amount of one or more of these components is preferably 5%, more preferably 1%, and even more preferably not substantially contained.

Nb ₂ O ₅ is an optional component that can lower the melting point and Tg of the glass electrolyte when it contains more than 0% in total. On the other hand, the content of Nb ₂ O ₅ is preferably 5%, more preferably 3%, from the viewpoint of suppressing an increase in the material cost of the glass electrolyte.

ZnO and PbO may contain at least one of more than 0% in total from the viewpoint of further improving the meltability of the glass raw material.
On the other hand, from the viewpoint of suppressing a decrease in the ionic conductivity of the glass electrolyte, the total amount of one or more of these components is preferably 3%, more preferably 0.5% as an upper limit, and still more preferably substantially contained. I won't let you.

<Production of glass electrolyte>
The glass electrolyte of the present invention can be produced, for example, by the following method. That is, a predetermined amount of each starting material is weighed and mixed uniformly, then placed in a crucible made of alumina, quartz, gold, or platinum and accommodated in an electric furnace, and the temperature is raised to 750 ° C to 1300 ° C. Hold for 30 minutes to 4 hours to dissolve. A molten glass obtained by melting is formed into a plate shape and cooled by slow cooling or water cooling, whereby a plate-like glass electrolyte can be obtained.

<Characteristics of glass electrolyte>
The glass electrolyte of the present invention preferably has lithium ion conductivity. More specifically, the lithium ion conductivity (ion conductivity) at 25 ° C. of the glass electrolyte is preferably 1.0 × 10 ⁻¹⁰ S · cm ⁻¹ or more. Thereby, since the conduction of lithium ions through the glass electrolyte is performed smoothly, the resistance of the battery can be lowered. Here, the ionic conductivity of the glass electrolyte of the present invention is preferably 1.0 × 10 ⁻¹⁰ S · cm ⁻¹ or more, more preferably 1.0 × 10 ⁻⁹ S · cm ⁻¹ , and even more preferably 1. The lower limit is 0.0 × 10 ⁻⁷ S · cm ⁻¹ . When this ionic conductivity is less than 1 × 10 ⁻¹⁰ , lithium ion conduction does not substantially occur.

The glass electrolyte of the present invention preferably has high resistance to polar solvents. That is, the weight loss rate (weight loss rate) before and after being immersed in water at 60 ° C. for 1 hour is preferably less than 50% by mass. Thereby, the fall of the ion conductivity by the glass electrolyte itself and the specific component contained in a glass electrolyte eluting to a solvent, and the ionic conductivity fall by crystallization of the glass component eluted to the solvent can be suppressed. Here, the weight loss rate before and after immersing the glass electrolyte of the present invention in water at 60 ° C. for 1 hour is less than 50 mass%, more preferably less than 40 mass%, and still more preferably less than 37 mass%.
In addition, as an index of resistance to a polar solvent, it is preferable to use resistance to water, which is a highly polar solvent, as described above.

  The glass electrolyte of the present invention is preferably easily softened. More specifically, the glass electrolyte of the present invention preferably has a glass transition point (Tg) of 500 ° C. or lower. Thereby, since glass electrolyte becomes easy to soften by heating, formation of the space | gap between particle | grains can be made easy and ion conductivity can be raised. Therefore, Tg of the glass electrolyte of the present invention is preferably 500 ° C, more preferably 450 ° C, and most preferably 400 ° C. On the other hand, the lower limit of Tg is not limited, but may be, for example, 100 ° C. or higher, more specifically 200 ° C. or higher, and more specifically 300 ° C. or higher.

  The crystallization start temperature Tx of the glass electrolyte of the present invention is preferably 400 ° C., more preferably 410 ° C., and further preferably 420 ° C. By increasing this temperature, it is possible to suppress a decrease in ionic conductivity due to devitrification of the glass electrolyte.

The melting point of the glass electrolyte of the present invention is preferably 700 ° C. or lower, more preferably 650 ° C. or lower, and further preferably 600 ° C. Thereby, the thermal decomposition reaction between the glass electrolyte, the crystalline solid electrolyte, and the electrode active material due to the heat treatment at the time of manufacturing the battery can be reduced, and the decrease in the discharge capacity caused thereby can be suppressed.
On the other hand, the melting point of the glass electrolyte of the present invention is preferably 400 ° C., more preferably 450 ° C., and still more preferably 500 ° C. This makes it possible to suppress the dissolution of the glass electrolyte and the resulting reaction of the glass electrolyte when degreasing the binder contained in the sheet formed from the slurry when producing a laminated all solid lithium ion secondary battery. . In addition, by suppressing the simultaneous progress of glass electrolyte dissolution and binder degreasing, it is possible to smoothly degrease the sheet when producing a laminated all-solid lithium ion secondary battery. Battery short-circuiting due to the conduction of electrons in the electrolyte layer due to the generated residual carbon can be suppressed.
In particular, since the melting point of the glass electrolyte depends on the degreasing temperature of the binder used for sheet forming, the lower limit of the binder degreasing temperature + 50 ° C. may be used. This makes it possible to smoothly degrease the sheet when producing a laminated all-solid-state lithium ion secondary battery, so that the battery short circuit due to the conduction of electrons in the electrolyte layer due to residual carbon generated due to poor degreasing of the binder Can be suppressed.

[All-solid lithium ion secondary battery]
The glass electrolyte of the present invention can be preferably used for all solid lithium ion secondary batteries including lithium ion secondary batteries. The all-solid-state lithium ion secondary battery has a positive electrode layer and a negative electrode layer, and an electrolyte layer interposed therebetween, and at least one of the positive electrode layer, the negative electrode layer, and the electrolyte layer has a main layer. The glass electrolyte of the invention is preferably included as a solid electrolyte.
As a result, when the electrolyte layer or the electrode layer is produced from the slurry, the glass electrolyte can be well dispersed in the slurry using a polar solvent, and the glass component is made difficult to elute into the polar solvent. Crystal precipitation can be suppressed. Therefore, the electrolyte layer and the electrode layer can be easily produced from the slurry, and a decrease in ionic conductivity due to elution of the glass component can be suppressed.
Further, the electrode layer or the electrolyte layer can be densified by heat treatment at a temperature near or above the melting point or melting point of the glass electrolyte in a state where the glass electrolyte of the present invention is contained in the electrode layer or the electrolyte layer. By increasing the density, the distance between the particles is narrowed, and the contact probability between the crystalline solid electrolytes and the contact probability between the electrode active material and the crystalline material can be increased, so that the ion conductivity can be improved. At this time, since the glass electrolyte has ion conductivity, the density of the electrode layer and the electrolyte layer can be increased without hindering the original conduction of lithium ions.
For example, such high densification may be caused by the fact that the glass electrolyte of the present invention enters the gap between the crystalline solid electrolyte and the electrode active material, so that the crystalline solid electrolytes are bonded to each other via the glass electrolyte. It is thought that these contact properties are improved by bonding the electrode active material and the crystalline solid electrolyte via the.
Furthermore, since the ionic conductivity of the electrolyte layer and the electrode layer is enhanced by improving the ionic conductivity of the glass electrolyte itself, the charge / discharge characteristics of the all-solid lithium ion secondary battery can be further enhanced.
In particular, it is more preferable that a glass electrolyte is included as a solid electrolyte in all of the positive electrode layer, the negative electrode layer, and the electrolyte layer. Thereby, the effect regarding the ease of preparation of an all-solid-state lithium ion secondary battery and the improvement of charging / discharging characteristic can be heightened more.

<Electrolyte layer>
The electrolyte layer of this embodiment preferably includes a glass electrolyte and a crystalline solid electrolyte, and more preferably includes a ceramic electrolyte as the crystalline solid electrolyte. More specifically, the total content of the glass electrolyte and the crystalline solid electrolyte is preferably 80% or more with respect to the total mass of the electrolyte layer. Thereby, since the path | route which lithium ion conducts becomes easy to be formed in an electrolyte layer, the lithium ion conductivity of an electrolyte layer can be improved more.
On the other hand, the upper limit of the total content of the glass electrolyte and the crystalline solid electrolyte is not particularly limited, and may be 100%.

The thickness of the electrolyte layer is preferably in the range of 1 μm or more and 50 μm or less.
In particular, by setting the thickness of the electrolyte layer to 50 μm or less, the internal resistance of the all-solid lithium ion secondary battery can be reduced by reducing the ionic conduction resistance of the electrolyte layer. In addition, since the electrolyte layer is thinned, the number of electrode layers stacked per unit volume can be increased, and as a result, the discharge capacity and energy density per unit volume can be improved. In this case, the upper limit of the thickness of the electrolyte layer is preferably 50 μm, more preferably 40 μm, and most preferably 20 μm.
On the other hand, the short circuit between the positive electrode layer and the negative electrode layer can be reduced by setting the thickness of the electrolyte layer to 1 μm or more. Moreover, as the particles of the crystalline solid electrolyte powder and the glass electrolyte used for the electrolyte layer, particles having an average particle diameter of 1/5 to 1/10 of the target thickness are generally preferably used. Since it becomes possible to use larger particles by increasing the thickness, the material cost of the all-solid-state lithium ion secondary battery can be reduced. In this case, the lower limit of the thickness of the electrolyte layer is preferably 1 μm, more preferably 3 μm, and most preferably 5 μm.

<Positive electrode layer and negative electrode layer>
The positive electrode layer in this embodiment preferably contains a glass electrolyte, a crystalline solid electrolyte, a positive electrode active material, and a conductive additive. Moreover, it is preferable that the negative electrode layer in this embodiment contains a glass electrolyte, a crystalline solid electrolyte, a negative electrode active material, and a conductive additive.
Further, by containing the glass electrolyte of the present invention, the electrode layer or the electrolyte layer is densified, so that the contact between the crystalline solid electrolytes and the contact between the electrode active material and the crystalline solid electrolyte can be improved. Therefore, the ionic conductivity of the positive electrode layer and the negative electrode layer can be increased.
Furthermore, since the desired ionic conductivity can be ensured even if the glass electrolyte content contained in these electrode layers is reduced, the content of the electrode active material and the conductive auxiliary agent can be increased instead. It can be easily adjacent to both the electrolyte and the conductive additive.
In this specification, the positive electrode layer and the negative electrode layer are collectively referred to as an electrode layer, and the positive electrode active material and the negative electrode active material are collectively referred to as an electrode active material.

In the electrode layer of this embodiment, the total content of the glass electrolyte and the crystalline solid electrolyte is preferably 20 to 70% by mass with respect to the total mass of the electrode layer.
In particular, by setting the total content to 20% or more, it becomes easy to secure a migration path of lithium ions formed by the glass electrolyte, and thus it is possible to easily improve the charge / discharge characteristics and battery capacity of the battery. Therefore, the total content of the glass electrolyte and the crystalline solid electrolyte in the electrode layer is preferably 20%, more preferably 25%, and still more preferably 30%.
On the other hand, since the content of the electrode active material contained in the electrode layer is increased by setting the total content to 70% or less, the energy density of the all-solid lithium ion secondary battery can be increased. Therefore, the total content of the glass electrolyte and the crystalline solid electrolyte in the electrode layer is preferably 70%, more preferably 65%, and still more preferably 60%.

The crystalline solid electrolyte, for example, the general formula _{Li 1 + x + 2y + z} M 2-x-2y A x B z Si z P 3-x O 12 ( where, 0 ≦ x ≦ 0.7,0 ≦ y ≦ 0.4 0 ≦ Z ≦ 0.5, M is one or more selected from Zr, Ti, and Ge, A is one or more selected from Al, Y, and Sc, and B is Ca. Or a ceramic electrolyte represented by the general formula Li ₇ La ₃ Zr ₂ O ₁₂ [LLZ].

The thickness of the positive electrode layer and the negative electrode layer is preferably 40 μm or less. Thereby, since the distance which conducts lithium ion in an electrode layer becomes short, battery resistance can be made small. Moreover, even if it increases content of the electrode active material in an electrode layer by this, the electrode active material to which a lithium ion cannot conduct easily can be reduced. Therefore, the upper limit of the thickness of the positive electrode layer and the negative electrode layer is preferably 40 μm, more preferably 30 μm, and most preferably 20 μm.
On the other hand, by setting the thickness of the positive electrode layer and the negative electrode layer to 1 μm or more, the ratio of the electrode layer can be increased in the ratio of the electrode layer to the electrolyte layer, and extremely thin electrolyte layers and extremely fine electrolyte particles can be obtained. Even if it is not used, the energy density of the battery can be increased. In particular, in a laminated all solid lithium ion secondary battery, an increase in electrical resistance in the direction perpendicular to the lamination direction can be suppressed. Therefore, the lower limit of the thickness of the positive electrode layer and the negative electrode layer is preferably 1 μm, more preferably 2 μm, still more preferably 5 μm, and most preferably 10 μm.

(Positive electrode active material and negative electrode active material)
The positive electrode active material is, for example, NASICON-type LiV ₂ (PO ₄ ) ₃ , olivine-type Li _x J _y MtPO ₄ (where J is at least one selected from Al, Mg, W, Mt is Ni, One or more selected from Co, Fe, and Mn, 0.9 ≦ x ≦ 1.5, 0 ≦ y ≦ 0.2), a layered oxide, or a spinel oxide is preferable.
As specific examples of the positive electrode active material, for example, LiV ₂ (PO ₄ ) ₃ , LiFePO ₄ , LiCoPO ₄ , LiCoO ₂ , LiMn ₂ O ₄ can be used.

The negative electrode active material is at least one selected from an oxide containing NASICON, olivine, and spinel crystals, a rutile oxide, an anatase oxide, an amorphous metal oxide, or a metal alloy. Preferably there is.
Specific examples of the negative electrode active material include, for example, Li ₂ V ₂ (PO ₄ ) ₃ , Li ₂ Fe ₂ (PO ₄ ) ₃ , LiFePO ₄ , Li ₄ Ti ₅ O ₁₂ , TiO ₂ , SiO _x (0.25 ≦≦ x ≦ 2), Cu ₆ Sn ₅ can be used.

The content of the positive electrode active material and the negative electrode active material is preferably 1% by mass or more and 20% by mass or less with respect to the entire material of the electrode layer (that is, the positive electrode material or the negative electrode material).
In particular, the battery capacity of the secondary battery can be increased by setting these contents to 1% by mass or more. Therefore, the content of the positive electrode active material and the negative electrode active material is preferably 1% by mass, more preferably 2% by mass, and still more preferably 4% by mass.
On the other hand, by setting these contents to 20% by mass or less, it is possible to easily ensure the electron conductivity of the electrode layer. Therefore, the content of the positive electrode active material and the negative electrode active material is preferably 20% by mass, more preferably 15% by mass, and still more preferably 10% by mass.

These electrode layers may also be mixed with the same inorganic binder as the electrolyte layer.
The content of the inorganic binder contained in the electrode layer is preferably 20%, more preferably 10%, and still more preferably 5% with respect to the total mass of the electrode layer.

(Conductive aid)
As the conductive assistant, use carbon such as acetylene black, ketjen black, carbon black, a metal composed of at least one of Ni, Fe, Mn, Co, Mo, Cr, Ag and Cu, and alloys thereof. it can. Alternatively, a metal such as titanium, stainless steel, or aluminum, or a noble metal such as platinum, silver, gold, or rhodium may be used. By using such a material with high electron conductivity as a conductive additive, the amount of current that can be conducted through the narrow electron conduction path formed in the electrode layer increases, so the charge / discharge characteristics of the all-solid-state lithium ion secondary battery Can be increased.

  The content of the conductive assistant is 1% by mass or more and 20% by mass with respect to the entire electrode material (that is, the positive electrode material or the negative electrode material) of the electrode layer in consideration of the balance between the battery capacity and the electron conductivity of the electrode layer. The content is preferably 2% by mass or more and 15% by mass or less, more preferably 4% by mass or more and 10% by mass or less.

  In the all solid lithium ion secondary battery using the glass electrolyte of the present invention, one or two of the electrolyte layer, the positive electrode layer, and the negative electrode layer may be conventionally known. However, by using a glass electrolyte for all of the electrolyte layer, the positive electrode layer, and the negative electrode layer, an all-solid lithium ion secondary battery having a longer life and higher charge / discharge characteristics can be formed.

(Current collector)
In the all solid lithium ion secondary battery of this embodiment, a current collector may be provided in the positive electrode layer and / or the negative electrode layer. Thereby, since it becomes easy to take out electricity through a collector, it can carry out charge to an all-solid-state lithium ion secondary battery, and discharge from an all-solid-state lithium ion secondary battery easily. As a specific embodiment of the current collector, a thin film metal layer may be laminated or bonded to the positive electrode layer and / or the negative electrode layer, and a metal layer or a conductor precursor is laminated on the raw material composition. And then fired. Note that the current collector may not be provided if the electrode layer itself has high electron conductivity.

The contents of the glass electrolyte, electrode active material, and conductive additive contained in the electrolyte layer and electrode layer described in this specification and the composition thereof are used to cut out the electrolyte layer and electrode layer, and to provide a field emission transmission electron microscope. It is possible to specify using an energy loss analysis apparatus or X-ray analysis apparatus mounted on (FE-TEM), or an X-ray analysis apparatus mounted on a field emission scanning microscope (FE-SEM). By using such quantitative analysis or point analysis, for example, the presence or absence of glass electrolyte in the electrolyte layer, its content and composition can be known. Here, when an X-ray analyzer is used, the Li ₂ O component cannot be directly analyzed, but the content of the Li ₂ O component can be estimated by calculating the charge from other components.

  When preparing the positive electrode layer, the negative electrode layer, and the electrolyte layer, specifically, the positive electrode sheet, the negative electrode sheet, and the electrolyte sheet should include a composite of a glass electrolyte and a crystalline solid electrolyte prepared in advance. You can also. As a result, the glass electrolyte powder is softened by the heat treatment in obtaining the applied product and enters the gap between the powders of the crystalline solid electrolyte. The contact property between the electrolyte and the electrode active material is improved. In addition, since a dense structure solidified by the glass electrolyte is formed, a layer containing a solid electrolyte that has higher ionic conductivity and mechanical properties can be produced.

[Examples 1-14, Comparative Examples 1-3]
Tables 1 to 3 show the compositions of the glass electrolytes of Examples and Comparative Examples of the present invention, and the lithium ion conductivity of these glass electrolytes and the results of resistance (weight loss rate) to polar solvents. The following examples are merely for illustrative purposes, and are not limited to these examples.
The following notations in Table 1 indicate the following contents (mol%) as follows.
Y + Sc + Zr + Ce + Sm: Total content of Y ₂ O ₃ component, Sc ₂ O ₃ component, ZrO ₂ component, CeO ₂ component and Sm ₂ O ₃ component Zr + Ce: Total content of ZrO ₂ component and CeO ₂ component

(Production of glass electrolyte)
As raw materials for each component, high-purity raw materials such as boric acid, aluminum metaphosphate, aluminum oxide, zirconium oxide, yttrium oxide, cerium oxide, scandium oxide, lithium carbonate, lithium metaphosphate, and lithium phosphate are used, and these are based on oxides. The glass raw material was prepared so that it might become a composition of Table 1-Table 3 per mol% unit. The prepared glass raw material was put into a crucible made of alumina, quartz, gold, or platinum, and heated and melted for 30 minutes to 4 hours while stirring at 750 ° C. to 1300 ° C. in an electric furnace.

  Then, the glass electrolyte shape | molded by the thin plate shape was obtained by pinching and shape | molding the fuse | melted glass raw material between two cast plates. After the obtained thin glass block was cut, both surfaces thereof were ground and polished to obtain a disk-shaped glass electrolyte having a diameter of 25.4 mm and a thickness of 0.25 mm.

  On the other hand, the molten glass raw material was poured into a metal mold, formed into a plate shape, and cooled by slow cooling or water cooling to produce a glass block. This glass block was pulverized to an average particle size of 1 μm (D50) using a stamp mill and a planetary ball mill to obtain a glass electrolyte powder.

  The glass transition point (Tg), crystallization start temperature Tx (° C.), and melting point (° C.) shown in Tables 1 to 3 are values measured by a thermal analysis system (TG-DTA2000SA manufactured by BRUKER). In addition, the melting point of the glass electrolyte in this specification means mp measured with this thermal analysis system device.

(Production of crystalline solid electrolyte (ceramic electrolyte))
Li _1.3 Al _0.1 Zr _1.8 Y _0.1 Si _0.1 P _2.9 O ₁₂ powder was produced as a ceramic electrolyte that is a crystalline solid electrolyte by the following method.
Li ₂ CO ₃ , ZrO ₂ , Al ₂ O ₃ , Y ₂ O _3, and SiO ₂ powder and a H ₃ PO ₄ solution were mixed in a stoichiometric ratio as raw materials, and then mixed at 1480 ° C. on a platinum plate. The mixture was fired for a period of time, and the fired mixture was pulverized with a stamp mill so as to have a diameter of 200 μm or less. To this, a YTZ ball of φ2 mm and ethanol were added, and further pulverized and dried using a planetary ball mill to obtain a ceramic electrolyte powder having an average particle size of 1.0 μm (D50).

  6 g of glass electrolyte powder and 114 g of ceramic electrolyte powder were mixed, and 77.3 g of an acrylic polymer (Oricox KC-250 (trade name), manufactured by Kyoeisha Chemical Co., Ltd.) was used as a binder, and BYK180 was used as a polymer dispersant. 8.6 g (manufactured by Big Chemie Japan), 0.4 g of silicone-containing oligomer (Polyflow KL-100, manufactured by Kyoeisha Chemical Co., Ltd.) as a wetting material, di-2-ethylhexyl sebacate (DOS, Ito Oil Co., Ltd.) as a plasticizer 7.7g made by company) and 50g ethanol as a solvent were added and mixed with a ball mill to prepare an electrolyte slurry.

  The obtained electrolyte slurry was applied to a base material made of PET subjected to a release treatment at a drying temperature of 110 ° C. at the same time as applying with a gap of 400 μm using a coating machine, and a thickness of 30 μm, a width of 18 cm, A sheet having a length of 5 m was obtained. The sheet was cut into a 12 cm square to produce an electrolyte sheet.

Subsequently, 30 sheets of the obtained electrolyte sheets were laminated using a single wafer type laminating machine (manufactured by Alpha System Co., Ltd.).
At this time, the outer dimension of the sheet after the release treatment was set to 15 cm square, temporary lamination was performed each time the layers were laminated, and finally, two-stage pressing was performed as the main lamination. Temporary lamination was performed at normal pressure and a press pressure of 100 kPa. Next, vacuum deaeration was performed to remove bubbles in the sheet. The main lamination performed thereafter was performed at a press pressure of 250 kPa.

The sheet laminate obtained by lamination was cut out at a diameter of 11 mm and degreased at 400 ° C. for 3 hours in a nitrogen atmosphere. Thereafter, the upper mold is placed in a mold, heated to 600 ° C. at a rate of 2 ° C./sec while applying a pressure of 2000 kg / cm ² with a hydraulic press, and after reaching 600 ° C., the pressure is released. By allowing to cool to room temperature, a composite electrolyte containing a glass electrolyte and a ceramic electrolyte was obtained.

  The lithium ion conductivity of the glass electrolyte and the composite electrolyte was calculated at 25 ° C. by complex impedance measurement by an alternating current two-terminal method using an impedance analyzer SI-1260 manufactured by Solartron. Here, the complex impedance measurement was performed using a quick coater manufactured by Sanyu Electronics, using gold as a target, sputtering on both surfaces of the glass electrolyte, attaching gold electrodes, and using these gold electrodes as terminals.

As an accelerated test to confirm the resistance of glass electrolyte to polar solvent (ethanol), we measured the weight loss rate (%) before and after being immersed for 1 hour at a high temperature of 60 ° C using safe water with higher polarity. did. The purpose of this test is to avoid the danger of using high-temperature ethanol in experiments.

  As shown in the table, the glass electrolyte of the example of the present invention has a weight loss rate of less than 50% by mass before and after being immersed in water at 60 ° C. for 1 hour, more specifically less than 37% by mass. there were. On the other hand, the weight loss of the glass electrolytes of Comparative Examples 1 and 2 was 50% by mass or more. Moreover, the weight loss of the glass electrolyte of Comparative Example 3 was 37% by mass or more. Therefore, it was confirmed that the glass electrolyte of the Example of this invention has the tolerance with respect to a polar solvent higher than the glass of a comparative example. From this, it can be expected that resistance to polar solvents (ethanol) is also increased.

Moreover, the glass electrolyte of the Example of this invention was 1 * 10 < ^-9 > S / cm or more in ionic conductivity, and was in the desired range. In particular, the glass electrolytes of Examples 9 to 14 had an ionic conductivity of 1.5 × 10 ⁻⁷ S / cm or more and higher ionic conductivity than Examples 1 to 8. As a reason for exhibiting such high ion conductivity, it is inferred that the glass electrolytes of Examples 9 to 14 commonly contain the Al ₂ O ₃ component, thereby improving the stability of the glass. Is done.

Moreover, the ionic conductivity when the glass electrolyte of the Example of this invention added a ceramic electrolyte and produced composite electrolyte was 1 * 10 < ^-6 > S / cm or more, and showed high ionic conductivity. On the other hand, the glass electrolytes of Comparative Examples 1 to 3 had an ionic conductivity lower than 1 × 10 ⁻⁶ S / cm. Therefore, it was confirmed that the glass electrolyte of the example of the present invention has higher ionic conductivity than the glass of the comparative example, particularly when used as a raw material of the composite electrolyte together with the ceramic electrolyte.

(Preparation of stacked all-solid lithium ion secondary battery)
The glass electrolytes of the respective examples and comparative examples and ceramic electrolytes were mixed at the ratios shown in Tables 4 and 5, and then acrylic polymers (Oricox KC-250 (trade name), Kyoeisha Chemical Co., Ltd.) as binders. Manufactured by), BYK180 (manufactured by Big Chemie Japan Co., Ltd.) as a polymeric dispersant, silicone-containing oligomer (Polyflow KL-100, manufactured by Kyoeisha Chemical Co., Ltd.) as a wetting material, and di-2-ethylhexyl sebacate (DOS Ito Oil Co., Ltd.) and ethanol as a solvent were added in the proportions shown in Tables 4 and 5 and then mixed using a ball mill to prepare an electrolyte slurry.
Further, in the proportions shown in Table 4 and Table 5, the glass electrolyte of Examples and Comparative Examples, LiFePO 4 _{(manufactured} by Hohsen Corporation) as a positive electrode active material, acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd. as a conductive additive , Denka Black (trade name)) and the ceramic electrolyte, and then the same binder, dispersant, wetting agent, plasticizer and solvent as the electrolyte slurry were added in the proportions shown in Tables 4 and 5, and then a ball mill was used. And mixed to prepare a positive electrode slurry.
In addition, at the ratios shown in Tables 4 and 5, the glass electrolytes of the examples and comparative examples were Li ₄ Ti ₅ O ₁₂ (manufactured by Titanium Industry Co., Ltd.) as the negative electrode active material and acetylene black (electrochemical) as the conductive assistant. After mixing Denka Black (trade name) manufactured by Kogyo Co., Ltd.) and a ceramic electrolyte, and then adding the same binder, dispersant, wetting agent, plasticizer and solvent as the electrolyte slurry in the proportions shown in Tables 4 and 5 The negative electrode slurry was prepared by mixing using a ball mill.

Here, Li _1.7 Al _0.4 Zr _1.8 Y _0.1 Si _0.2 P _2.8 O _{12 which} is a ceramic electrolyte used for the positive electrode was produced as follows. Li ₂ CO ₃ , ZrO ₂ , Al ₂ O ₃ , Y ₂ O _3, and SiO ₂ powder and a H ₃ PO ₄ solution were mixed in a stoichiometric ratio as raw materials, and then mixed at 1480 ° C. on a platinum plate. After firing for a time, the fired mixture was pulverized to 200 μm or less by a stamp mill. To this, a YTZ ball having a diameter of 2 mm and ethanol were added, and further pulverized and dried using a planetary ball mill to obtain a ceramic electrolyte powder having an average particle diameter of 1.0 μm (D50).

  The obtained positive electrode slurry, negative electrode slurry and electrolyte slurry were dried at a drying temperature of 110 ° C. at the same time as applying to a base material made of PET subjected to release treatment with a gap of 400 μm using a coating machine, A sheet having a thickness of 80 μm, a width of 18 cm, and a length of 5 m was obtained. This sheet was cut into a 12 cm square to prepare a positive electrode sheet, a negative electrode sheet, and an electrolyte sheet.

Among these, the positive electrode sheet and the negative electrode sheet were irradiated with laser using a laser processing machine (manufactured by Panasonic Electric Works SUNX Co., Ltd., model number LPV-15U) to form an opening having a circular opening with a diameter of 1 mm. As shown in FIG. 3 (c), seven positive electrode sheets having openings formed thereon were prepared as sheets C, and seven negative electrode sheets having openings formed therein as sheets A were prepared as shown in FIG. At this time, the positive electrode sheet and the negative electrode sheet were formed with openings at different positions. Further, as shown in FIG. 3D, one sheet of positive electrode sheet not forming an opening is prepared as a sheet D, and one sheet of negative electrode sheet not forming an opening is prepared as a sheet B as shown in FIG. did.
On the other hand, the electrolyte sheet is also irradiated with a laser using a laser processing machine, and an opening having a circular opening with a diameter of 0.8 mm at a position overlapping with the center of at least one opening of the positive electrode sheet and the negative electrode sheet. Formed. At this time, as shown in FIG. 3G, one electrolyte sheet having an opening formed only at a position overlapping with the center of the opening of the positive electrode sheet is prepared as a sheet G, and the negative electrode is formed as shown in FIG. One sheet of the electrolyte sheet in which the opening is formed only at a position overlapping the center of the opening of the sheet is prepared as a sheet F, and the electrolyte sheet in which the opening is formed in both positions as shown in FIG. 13 sheets were prepared.
The schematic diagram of the opening part formed in sheet | seat AG is shown in FIG.

Subsequently, the positive electrode sheet, the positive electrode sheet, the electrolyte sheet, the negative electrode sheet, the electrolyte sheet, and the positive electrode sheet were alternately stacked in this order using a single wafer type laminator (manufactured by Alpha System Co., Ltd.). More specifically, after the sheet D, the sheet F, the sheet A, the sheet E, the sheet C, and the sheet C are sequentially stacked, the sheet E, the sheet A, the sheet E, the sheet C, and the sheet C are repeated six times in this order. After that, the sheet G and the sheet B were sequentially laminated. At this time, the opening at the common position of the two positive electrode sheets and the opening at the electrolyte sheet adjacent to the opening are overlapped, and the opening of the negative electrode sheet and the opening at the electrolyte sheet adjacent thereto are overlapped Are superimposed.
At this time, the outer dimension of the sheet after the release treatment was set to 15 cm square, temporary lamination was performed every time each layer was laminated, and finally, two-stage pressing was performed as the main lamination. Temporary lamination was performed at normal pressure and a press pressure of 100 kPa. Next, vacuum deaeration was performed to remove bubbles in the sheet. Subsequent main lamination was performed at a press pressure of 250 kPa to obtain a sheet laminate.

The pressed sheet laminate was cut out at a diameter of 11 mm and degreased at 400 ° C. for 3 hours in a nitrogen atmosphere. Thereafter, the upper mold is placed in a mold, heated to 600 ° C. at a rate of 2 ° C./sec while applying a pressure of 2000 kg / cm ² with a hydraulic press, and after reaching 600 ° C., the pressure is released. By allowing to cool to room temperature, a laminated all-solid lithium ion secondary battery was obtained. When the cross section of the produced laminated all solid lithium ion secondary battery was observed with an electron microscope, the thickness of the positive electrode layer was 40 μm, the thickness of the negative electrode layer was 40 μm, and the thickness of the electrolyte layer was 15 μm.

  The produced laminated all-solid-state lithium ion secondary battery was dried in a vacuum at 100 ° C. for 1 hour, and then dew point − using a cell holder made of a tab film, an aluminum laminate film, a copper foil, and an aluminum foil. Packaged in a vacuum at 50 ° C. in a dry room. At this time, a copper foil current collector is arranged on the negative electrode side, an aluminum foil current collector is arranged on the positive electrode side, and a laminated all-solid lithium ion secondary battery is vacuum-packed by sandwiching the upper and lower sides with an aluminum laminate package. Then, the packaged laminated all solid lithium ion secondary battery was obtained by fastening the aluminum laminate package with a clip.

  About this packaged laminated all-solid-state lithium ion secondary battery, it put in the thermostat, and the charge / discharge test was done at 25 degreeC. Charge at a constant current of 1/100 C, stop charging when it reaches 2.8 V, discharge at a constant current of 1/100 C, measure the discharge capacity until it reaches 0.3 V, and the weight of the positive electrode active material The discharge capacity per unit was calculated. As a result, discharge capacities when the glass electrolytes of Examples and Comparative Examples are used for the electrolyte layer, the positive electrode layer, and the negative electrode layer are as shown in Tables 1 to 3, respectively.

  As shown in the table, the all solid lithium ion secondary battery using the glass electrolyte of the example of the present invention for each of the electrolyte layer, the positive electrode layer, and the negative electrode layer has a discharge capacity of 100 mAh / g or more, more specifically. Was 105 mAh / g or more, and a high discharge capacity was obtained. On the other hand, the secondary battery using the glass of the comparative example for each of the electrolyte layer, the positive electrode layer, and the negative electrode layer had a discharge capacity of less than 100 mAh / g. Therefore, it was confirmed that the all-solid-state lithium ion secondary battery produced from the glass electrolyte of the Example of this invention can obtain a higher discharge capacity than the secondary battery produced from the glass electrolyte of a comparative example.

FIG. 1 shows the relationship between the weight loss rate of the glass electrolytes of Examples and Comparative Examples and the discharge capacity of an all-solid-state lithium ion secondary battery manufactured using the same. FIG. 2 also shows the weight loss ratio of the glass electrolyte of the example and the glass electrolyte of the comparative example, and the logarithm of the ionic conductivity of the composite electrolyte produced using the glass electrolyte and the ceramic electrolyte of the example and the comparative example. The relationship is shown. From FIG. 1 and FIG. 2, it is inferred that the weight loss rate shows a substantially linear correlation with the logarithm of ionic conductivity and the discharge capacity.
This indicates that a glass electrolyte having a smaller weight loss rate, that is, a higher resistance to a polar solvent, has higher ionic conductivity and higher discharge capacity.

It is presumed that the resistance of the glass electrolyte to the polar solvent is increased, so that the glass electrolyte is less likely to be affected by the solvent at the time of slurry formation, so that —OH groups or the like are less likely to enter the surface of the glass electrolyte. At this time, since the conduction of Li ⁺ ions is performed by movement of Li ⁺ through the grain boundary, it is difficult for the —OH group to exist at the grain boundary during molding, thereby reducing the lithium ion conductivity due to the —OH group. Presumed to be suppressed.
Although some of the —OH groups and H ₂ O adsorbed on the glass at the time of forming the slurry are removed by heating at the time of forming, etc., the —OH groups near the surface of the glass are close to chemical adsorption. It is considered that the —OH group, which cannot be completely removed even by heating at the time and continues to exist on the surface of the glass, adversely affects lithium ion conductivity.

  In addition, the resistance of the glass electrolyte to the polar solvent increases, and it becomes difficult for the glass electrolyte itself and a specific component contained in the glass electrolyte to elute into the solvent. It is presumed that the decrease in lithium ion conductivity due to precipitation and crystallization of eluted components can be suppressed.

  Thus, by reducing the weight loss rate of the glass electrolyte, that is, by increasing the resistance to polar solvents, the lithium ion conductivity of the glass electrolyte and the discharge capacity of the all-solid lithium ion secondary battery can be increased. Considered from this experiment.

  From this, in the glass electrolyte of the Example of this invention, ion conductivity improves and the discharge capacity of an all-solid-state lithium ion secondary battery is raised. Therefore, it is speculated that higher charge / discharge characteristics can be realized by using these glass electrolytes in an all-solid-state lithium ion secondary battery.

  As mentioned above, although embodiment of this invention was described in detail for the purpose of illustration, this invention is not restrict | limited to the said embodiment. Those skilled in the art can make many modifications without departing from the spirit and scope of the present invention, and these are also included within the scope of the present invention.

Claims (6)

On oxide basis,
Li ₂ O component from 39.8 to 65 mol%,
P ₂ O ₅ component 30-60 mol%,
Al ₂ O ₃ component 0 to 10 mol% and one or more selected from Y ₂ O ₃ component, Sc ₂ O ₃ component, ZrO ₂ component, CeO ₂ component and Sm ₂ O ₃ component in total 0.2 -10 mol%
Contains glass electrolyte. The glass electrolyte according to claim 1, comprising a total of 0.1 to 5 mol% of at least one selected from a ZrO ₂ component and a CeO ₂ component on an oxide basis. The glass electrolyte according to claim 1 or 2, comprising 1 to 10 mol% of an Al ₂ O ₃ component based on an oxide.   An all-solid lithium ion secondary battery comprising the glass electrolyte according to claim 1 in any one of a positive electrode layer, a negative electrode layer, and an electrolyte layer. _{Li 1 + x + 2y + z} M 2-x-2y A x B z Si z P 3-x O 12 ( where a 0 ≦ x ≦ 0.7,0 ≦ y ≦ 0.4,0 ≦ Z ≦ 0.5, M is one or more selected from Zr, Ti, and Ge, A is one or more selected from Al, Y, and Sc, and B is one or more selected from Ca and Mg. An all-solid-state lithium ion secondary battery in which the crystalline solid electrolyte of (1) and the glass electrolyte according to any one of claims 1 to 3 are contained in any of a positive electrode layer, a negative electrode layer, and an electrolyte layer. A crystalline solid electrolyte represented by the general formula Li ₇ La ₃ Zr ₂ O ₁₂ [LLZ] and the glass electrolyte according to any one of claims 1 to 3 are any of a positive electrode layer, a negative electrode layer, and an electrolyte layer. All-solid lithium ion secondary battery included.

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