JP2013097969A - Electrode for all-solid battery, and all-solid battery including the same - Google Patents

Abstract

An electrode for an all solid state battery capable of maintaining a filling rate higher than that of the prior art and an all solid state battery including the electrode are provided.
An electrode for an all-solid battery containing at least a powdered electrode active material and a powdered lithium ion conductive solid electrolyte, having a Young's modulus of 0.1 GPa or more and / or a tensile strength. An electrode for an all solid state battery, characterized by being 0.1 MPa or more.
[Selection] Figure 3

Description

  The present invention relates to an electrode for an all solid state battery capable of maintaining a higher filling rate than before, and an all solid state battery including the electrode.

  The secondary battery can convert the decrease in chemical energy associated with the chemical reaction into electrical energy and perform discharge. In addition, the secondary battery converts electrical energy into chemical energy by flowing current in the opposite direction to that during discharge. The battery can be stored (charged). Among secondary batteries, lithium secondary batteries are widely used as power sources for notebook personal computers, mobile phones, and the like because of their high energy density.

In the lithium secondary battery, when graphite (expressed as C) is used as the negative electrode active material, the reaction of the following formula (I) proceeds in the negative electrode during discharge.
Li _x C → C + xLi ⁺ + xe ⁻ (I)
(In the above formula (I), 0 <x <1.)
Electrons generated by the reaction of formula (I) reach the positive electrode after working with an external load via an external circuit. Then, lithium ions (Li ⁺ ) generated by the reaction of the formula (I) move by electroosmosis from the negative electrode side to the positive electrode side in the electrolyte sandwiched between the negative electrode and the positive electrode.

When lithium cobaltate (Li _1-x CoO ₂ ) is used as the positive electrode active material, the reaction of the following formula (II) proceeds at the positive electrode during discharge.
Li _1-x CoO ₂ + xLi ⁺ + xe ⁻ → LiCoO ₂ (II)
(In the above formula (II), 0 <x <1.)
At the time of charging, reverse reactions of the above formulas (I) and (II) proceed in the negative electrode and the positive electrode, respectively, and in the negative electrode, graphite (Li _x C) containing lithium by graphite intercalation is Since lithium cobaltate (Li _1-x CoO ₂ ) is regenerated, re-discharge is possible.

  Among secondary batteries, secondary batteries with solid electrolytes and solidified batteries do not contain flammable organic solvents in the batteries, so they can be safely and simplified, manufacturing costs and productivity It is considered excellent. In Patent Document 1, in an all-solid lithium secondary battery in which at least a negative electrode, a lithium ion conductive solid electrolyte, a positive electrode, and a current collector are stacked, a powdered positive electrode, a powdered lithium ion conductive solid electrolyte, An all-solid lithium secondary battery is disclosed, which is characterized by using a laminate formed by press-molding integrally.

JP 2009-164059 A

  Paragraph [0031] of the specification of Patent Document 1 describes the advantage of integrally pressing a powdered positive electrode and a powdered lithium ion conductive solid electrolyte in a laminated form. However, as a result of investigations by the present inventors, it has been clarified that in the configuration as described in Patent Document 1, the filling rate of the battery after pressure molding is significantly reduced.

  FIG. 6A shows a part of a conventional all-solid battery, in which a solid electrolyte layer 1 made of a solid electrolyte 4 having lithium ion conductivity and the solid electrolyte layer 1 are sandwiched between a pair of positive and negative electrodes. It is the figure which showed typically the cross section cut | disconnected in the lamination direction about the laminated body restrained with comparatively strong force. Usually, the positive electrode is mixed with the positive electrode active material 5 and the positive electrode active material layer 2 mixed with the solid electrolyte 4 if necessary, and the negative electrode is mixed with the negative electrode active material 6 and if necessary with the solid electrolyte 4. Each of the negative electrode active material layers 3 is provided. The laminated body shown in FIG. 6A is restrained by relatively strong pressure from both sides in the lamination direction, as indicated by arrows 7. Such a relatively strong pressure is a pressure applied mainly in a production process of a laminate, for example, a pressure molding process.

On the other hand, FIG.6 (b) is the figure which showed typically the cross section cut | disconnected in the lamination direction about the said laminated body restrained with comparatively weak pressure. Such a relatively weak pressure is mainly a pressure applied after pressure molding of the laminate. Therefore, as shown in FIG. 6B, in the conventional manufacturing process of an all-solid-state battery, the internal pressure in the laminated body is released after pressure molding, and the so-called springback reverses the pressure direction, that is, the outside. As a result, the filling rate of the all-solid-state battery, particularly the filling rate of the electrode, may be reduced, and the battery resistance may be increased.
The present invention has been accomplished in view of the above circumstances, and an object of the present invention is to provide an electrode for an all solid state battery that can maintain a filling rate higher than that in the past, and an all solid state battery including the electrode.

  The electrode for an all solid state battery of the present invention is an electrode for an all solid state battery containing at least a powdered electrode active material and a powdered lithium ion conductive solid electrolyte, and has a Young's modulus of 0.1 GPa or more, and / Or the tensile strength is 0.1 MPa or more.

  In this invention, it is preferable to further contain the binder containing a metal or an alloy.

  In the present invention, it is preferable that the binder contains at least one metal element selected from the group consisting of chromium, titanium, and aluminum.

  In the present invention, the binder preferably contains a metal or alloy having a Young's modulus of 10 GPa or more and / or a tensile strength of 50 MPa or more.

  In the present invention, the electrode active material, the lithium ion conductive solid electrolyte, and the binder are preferably pressure-molded so as to be integrated.

  The all solid state battery of the present invention is an all solid state battery comprising a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode, wherein at least one of the positive electrode and the negative electrode is The all-solid-state battery electrode is characterized in that

  In the present invention, the positive electrode, the negative electrode, and the solid electrolyte layer may be pressure molded so as to be integrated.

  According to the present invention, when the Young's modulus and / or the tensile strength is equal to or greater than a predetermined value, when the electrode according to the present invention is employed in an all-solid battery, spring back due to a difference in restraining pressure is suppressed, As a result of always keeping the filling rate above a certain level, the resistance of the all solid state battery can be reduced and a higher output than the conventional all solid state battery can be exhibited.

It is a figure which shows the typical example of the layer structure of the electrode for all-solid-state batteries which concerns on this invention, Comprising: It is the figure which showed typically the cross section cut | disconnected in the lamination direction. It is the figure which showed typically the cross section cut | disconnected in the lamination direction about the typical example of the laminated body which is a part of the all-solid-state battery which concerns on this invention. 5 is a graph showing the filling rate of negative electrodes for all solid state batteries of Example 1 to Example 2 and Comparative Example 1 to Comparative Example 2. FIG. 3 is a bar graph showing the Young's modulus of the all-solid battery negative electrode of Example 1 and Comparative Example 1. FIG. 6 is a graph showing the DC internal resistance of all solid state batteries of Example 3 to Example 4 and Comparative Example 3 to Comparative Example 4. FIG. It is the figure which showed typically the cross section cut | disconnected in the lamination direction about the laminated body which is a part of the conventional all-solid-state battery.

1. Electrode for all-solid-state battery The electrode for all-solid-state battery of the present invention is an electrode for all-solid-state battery containing at least a powdered electrode active material and a powdered lithium ion conductive solid electrolyte, and has a Young's modulus of 0. .1 GPa or more and / or tensile strength is 0.1 MPa or more.

As shown in Comparative Examples 3 and 4 which will be described later, the present inventors have used a conventional method of restraining with a relatively weak pressure (15 kgf / cm ² ) comparable to that of a liquid battery using an electrolytic solution. The all-solid-state battery (Comparative Example 4) has a significantly higher DC internal resistance than the conventional all-solid battery (Comparative Example 3) constrained with a relatively strong pressure (450 kgf / cm ² ). I found the problem of low. This is because, for a conventional all-solid-state battery, when it is released from a relatively strong restraint pressure during pressure molding, the above-described springback occurs, resulting in a decrease in electrode density, dissociation between battery materials, and electrode-electrolyte. This is thought to be because peeling between layers occurs. As a result of the study by the present inventors, it was found that the filling rate of the all-solid-state battery when the constraint pressure is low is 2% lower for the positive electrode and 5% lower for the negative electrode than when the constraint pressure is high. .

As a result of diligent efforts, the inventors of the present invention have a Young's modulus of 0.1 GPa or more and / or a tensile strength of 0.1 MPa or more. Even when it becomes weaker, the effect of increasing the bonding force between the materials contained in the electrode, that is, the so-called anchor effect is exhibited. The inventors have found that the output of can be improved, and have completed the present invention.
When the Young's modulus of the all-solid-state battery electrode is less than 0.1 GPa and the tensile strength is less than 0.1 MPa, the mechanical strength of the all-solid-state battery electrode is too weak. There is a possibility that springback due to release cannot be suppressed.
The all-solid-state battery electrode of the present invention more preferably has a Young's modulus of 0.1 to 1 GPa and a tensile strength of 1 to 100 MPa.

Examples of the Young's modulus measurement method include static test methods such as a tensile test method, a torsion test method, and a compression test method; dynamic test methods such as a pendulum method, a resonance method, and an ultrasonic pulse method. A tensile test method which is a kind of static test method can be performed in accordance with, for example, JIS G0567. The compression test method, which is a kind of static test method, is measured using, for example, a micro compression tester (manufactured by Shimadzu Corporation, model number: MCT-211, etc.) as shown in the examples described later. The Young's modulus is calculated from the measured displacement and the pressure applied to the sample. In addition, a resonance method and an ultrasonic pulse method, which are a kind of dynamic test method, can be performed in accordance with, for example, JIS Z2280.
Measurement of tensile strength (tensile strength) can be performed according to the method described in JIS Z2241 and / or JIS G0567.

The electrode for an all solid state battery according to the present invention contains a powdered electrode active material and a powdered lithium ion conductive solid electrolyte.
Hereinafter, the positive electrode for an all-solid battery and the negative electrode for an all-solid battery according to the present invention will be described in order.

1-1. Positive electrode for all-solid-state battery When the all-solid-state battery electrode according to the present invention is a positive electrode for an all-solid-state battery, preferably, a positive electrode active material containing a powdery positive electrode active material and the above lithium ion conductive solid electrolyte With layers. The positive electrode for an all-solid battery according to the present invention usually includes a positive electrode current collector and a positive electrode lead connected to the positive electrode current collector in addition to the positive electrode active material layer.

Specific examples of the positive electrode active material used in the present invention include LiCoO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNiPO ₄ , LiMnPO ₄ , LiNiO ₂ , LiMn ₂ O ₄ , LiCoMnO _4. , Li ₂ NiMn ₃ O ₈ , Li ₃ Fe ₂ (PO ₄ ) _3, Li ₃ V ₂ (PO ₄ ) _{3 and the} like. On the surface of fine particles composed of the positive electrode active material may be coated with LiNbO ₃ or the like.

  The average particle diameter of the positive electrode active material is, for example, preferably in the range of 1 to 50 μm, more preferably in the range of 1 to 20 μm, and particularly preferably in the range of 3 to 5 μm. If the average particle size of the positive electrode active material is too small, the handleability may be deteriorated. If the average particle size of the positive electrode active material is too large, it may be difficult to obtain a flat positive electrode active material layer. It is. The average particle diameter of the positive electrode active material can be determined by measuring and averaging the particle diameter of the active material carrier observed with, for example, a scanning electron microscope (SEM).

Examples of the lithium ion conductive solid electrolyte used in the present invention include sulfide solid electrolytes and oxide solid electrolytes.
Specific examples of the sulfide-based solid electrolyte include Li ₂ S—P ₂ S ₅ , Li ₂ S—P ₂ S ₃ , Li ₂ S—P ₂ S ₃ —P ₂ S ₅ , and Li ₂ S—SiS. _{2, Li 2 S-Si 2} S, Li 2 S-B 2 S 3, Li 2 S-GeS 2, LiI-Li 2 S-P 2 S 5, LiI-Li 2 S-SiS 2 -P 2 S 5 _{, Li 2 S-SiS 2 -Li} 4 SiO 4, Li 2 S-SiS 2 -Li 3 PO 4, Li 3 PS 4 -Li 4 GeS 4, Li 3.4 P 0.6 Si 0.4 S 4, Examples include Li _3.25 P _0.25 Ge _0.76 S ₄ , Li _4-x Ge _1-x P _x S _{4, and the} like. Among these sulfide-based solid electrolytes, in particular, solid electrolytes containing Li ₂ S and P ₂ S ₅ , that is, Li ₂ S—P ₂ S ₅ , Li ₂ S—P ₂ S ₃ —P ₂ S ₅ , _{LiI-Li 2 S-P 2} S 5, LiI-Li 2 S-SiS 2 -P 2 S 5, Li 3.4 P 0.6 Si 0.4 S 4, Li 3.25 P 0.25 Ge 0 _.76 S ₄ , Li _4-x Ge _1-x P _x S ₄ are preferred.
Specifically, as the oxide-based solid electrolyte, LiPON (lithium phosphate oxynitride), Li _1.3 Al _0.3 Ti _0.7 (PO ₄ ) ₃ , La _0.51 Li _0.34 TiO Examples include _0.74 , Li ₃ PO ₄ , Li ₂ SiO ₂ , Li ₂ SiO _{4 and the} like.
Only one type of solid electrolyte may be used alone, or two or more types may be used in combination.

In the present invention, it is further preferable to use a binder containing a metal or an alloy. Since the binder containing a metal or an alloy has a relatively higher Young's modulus than the electrode active material and the lithium ion conductive solid electrolyte, the material between the materials can be improved by suppressing the spring back that occurs after the pressure is released during pressure molding. As a result of maintaining the contact, the anchor effect appears. Due to the anchor effect, even when the restraint pressure becomes weak after pressure molding, the materials are held together by the binder, so that the internal pressure inside the electrode is hardly released and the filling rate of the electrode is kept high.
In addition, it is preferable that the binder used for this invention is a metal or an alloy itself from a viewpoint that ductility is exhibited effectively.

The binder used in the present invention preferably contains a metal or alloy having a Young's modulus of 10 GPa or more and / or a tensile strength of 50 MPa or more. As described above, by including a metal or alloy material having a Young's modulus and / or tensile strength of a specific value or more, the anchor effect is exhibited, and the Young's modulus and tensile strength of the all-solid-state battery electrode itself are increased. The filling rate of the electrodes can be kept higher. When the Young's modulus of the binder is less than 10 GPa and the tensile strength is less than 50 MPa, since the material strength of the binder is too weak, the force to hold the electrode materials together is due to the release of the internal pressure described above. May not be able to withstand springback. The measuring method of Young's modulus and tensile strength is as described above.
The binder used in the present invention more preferably contains a metal or alloy having a Young's modulus of 20 to 1,000 GPa and a tensile strength of 100 MPa to 1 GPa.

Specifically, it is preferable to use a metal or alloy containing chromium, titanium, or aluminum as the binder. One kind of these metal elements may be contained in the binder, or two or more kinds thereof may be contained.
Examples of the metal or alloy containing chromium element include chromium alone, SUS, chromium molybdenum steel, nickel chromium steel, and copper chromium.
Examples of the metal or alloy containing aluminum element include aluminum alone, aluminum fabric (# 1000 series), aluminum copper series alloy (# 2000 series), aluminum manganese series alloy (# 3000 series), and aluminum silicon series alloy (# 4000 series). , Aluminum magnesium alloy (No. 5000), aluminum magnesium silicon alloy (No. 6000), aluminum zinc magnesium alloy (No. 7000), and the like.
Examples of the metal or alloy containing titanium element include: titanium alone; near α-type titanium alloy such as Ti ₅ Al _2.5 Sn; α + β-type titanium alloy such as Ti ₆ Al ₄ V and Ti ₆ Al ₆ V ₂ Sn; Ti ₁₃ Β-type titanium alloys such as V ₁₁ Cr ₃ Al and Ti ₂₀ V ₄ AlSn;
These chromium simple substance, chromium alloy, aluminum simple substance, aluminum alloy, titanium simple substance, and titanium alloy are preferable because they are stable to the lithium ion conductive solid electrolyte material and can efficiently exhibit the anchor effect.

The shape and size of the binder is not particularly limited as long as it can increase the bonding force between the electrode materials and exhibit the anchor effect. Examples of the shape of the binder include a particle shape, a fiber shape, a belt shape, and a plate shape. In addition, the binder in the electrode after manufacture may be deform | transformed from the shape of the raw material of the binder before manufacture.
Although the content rate of the binder in a positive electrode active material layer changes with kinds of binder, Preferably it is 1-10 volume%.

The positive electrode active material layer may contain a conductive material, a binder, and the like as necessary.
The conductive material used in the present invention is not particularly limited as long as the conductivity of the positive electrode active material layer can be improved. Examples thereof include carbon black such as acetylene black and ketjen black. . Moreover, although the content rate of the electrically conductive material in a positive electrode active material layer changes with kinds of electrically conductive material, it is in the range of 1-10 mass% normally.

  Examples of the binder used in the present invention include polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE). In addition, the content of the binder in the positive electrode active material layer may be an amount that can fix the positive electrode active material or the like, and is preferably smaller. The content rate of a binder is in the range of 1-10 mass% normally.

  The thickness of the positive electrode active material layer used in the present invention varies depending on the intended use of the all-solid battery, but is preferably in the range of 10 to 250 μm and in the range of 20 to 200 μm. Is particularly preferable, and most preferably in the range of 30 to 150 μm.

  The positive electrode current collector used in the present invention has a function of collecting the positive electrode active material layer. Examples of the material for the positive electrode current collector include aluminum, copper, SUS, nickel, iron, and titanium. Of these, aluminum, copper, and SUS are preferable. Moreover, as a shape of a positive electrode electrical power collector, foil shape, plate shape, mesh shape etc. can be mentioned, for example, Foil shape is preferable.

  The method for producing the positive electrode for an all-solid battery according to the present invention is not particularly limited. The positive electrode active material, the lithium ion conductive solid electrolyte, and the binder are integrated so as to improve the filling rate of the electrode material in the positive electrode and efficiently exhibit the anchor effect by the binder. It is preferable to perform pressure molding.

1-2. Negative electrode for all-solid-state battery When the all-solid-state battery electrode according to the present invention is a negative electrode for all-solid-state battery, the negative electrode active material preferably contains a powdery negative electrode active material and the lithium ion conductive solid electrolyte. With layers. The all-solid-state battery negative electrode according to the present invention usually includes a negative electrode current collector and a negative electrode lead connected to the negative electrode current collector in addition to the negative electrode active material layer.

The negative electrode active material used in the present invention contains a metal, an alloy material, and / or a carbon material.
Specific examples of metals and alloy materials that can be used for the negative electrode active material include alkali metals such as lithium, sodium, and potassium; group 2 elements such as magnesium and calcium; group 13 elements such as aluminum; zinc, iron, and the like Or transition metal of these; or alloy materials and compounds containing these metals. Examples of the carbon material that can be used for the negative electrode active material include graphite. The negative electrode active material may be in the form of a powder or a thin film.
Examples of the compound containing lithium element include a lithium alloy, a metal oxide containing lithium element, a metal nitride containing lithium element, and a metal sulfide containing lithium element.
Examples of the lithium alloy include a lithium aluminum alloy, a lithium tin alloy, a lithium lead alloy, and a lithium silicon alloy. Examples of the metal oxide containing lithium element include lithium titanium oxide. Examples of the metal nitride containing lithium element include lithium cobalt nitride, lithium iron nitride, and lithium manganese nitride. Lithium coated with a solid electrolyte can also be used for the negative electrode active material layer.

The lithium ion conductive solid electrolyte used for the all-solid battery negative electrode can be the same as the above-described all-solid battery positive electrode. Moreover, it is preferable to use the binder mentioned above for the negative electrode for an all-solid-state battery according to the present invention.
The negative electrode active material layer may contain a conductive material, a binder, and the like as necessary. As the conductive material and the binder, the same materials as those for the positive electrode for an all-solid battery described above can be used.
Although it does not specifically limit as a film thickness of a negative electrode active material layer, For example, it is preferable to exist in the range of 10-100 micrometers, especially in the range of 10-50 micrometers.

  The same material as the positive electrode current collector described above can be used for the negative electrode current collector. Further, as the shape of the negative electrode current collector, the same shape as that of the positive electrode current collector described above can be adopted.

  The method for producing the all-solid battery negative electrode according to the present invention is not particularly limited. In addition, in order to improve the filling rate of the electrode material in the negative electrode and to efficiently exhibit the anchor effect by the binder, the negative electrode active material, the lithium ion conductive solid electrolyte, and the binder are integrated. It is preferable to perform pressure molding.

FIG. 1 is a diagram illustrating a typical example of the layer configuration of an electrode for an all solid state battery according to the present invention, and is a diagram schematically illustrating a cross section cut in a stacking direction. Double broken lines indicate omission of the figure.
A typical example 100 of an electrode for an all solid state battery includes an electrode active material layer 9 and an electrode current collector 10. When the typical example 100 is a positive electrode for an all-solid battery, the electrode active material layer 9 is a positive electrode active material layer, and the electrode current collector 10 is a positive electrode current collector. When the typical example 100 is an all-solid battery negative electrode, the electrode active material layer 9 is a negative electrode active material layer, and the electrode current collector 10 is a negative electrode current collector.
As shown in FIG. 1, the electrode active material layer 9 contains an electrode active material 11, a lithium ion conductive solid electrolyte 4, and a binder 12. As shown in FIG. 1, the binder 12 preferably has a shape that connects the electrode materials in the electrode active material layer to each other.

2. All-solid battery The all-solid battery of the present invention is an all-solid battery comprising a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode, and at least one of the positive electrode and the negative electrode The electrode is an electrode for an all-solid battery.
When the all-solid-state battery electrode contains a binder, the all-solid-state battery according to the present invention having the all-solid-state battery electrode is less likely to have a low filling rate even at a relatively weak restraint pressure. The internal resistance is smaller than that, and high output operation is possible.

  In the all solid state battery according to the present invention, the positive electrode and the negative electrode may be the all solid state battery electrodes described above. Moreover, the all-solid-state battery which concerns on this invention may be the electrode for all-solid-state batteries which any one of the positive electrode or the negative electrode mentioned above.

  When only the negative electrode is the above-described negative electrode for an all solid state battery, the positive electrode in the all solid state battery according to the present invention is the same as the above-described positive electrode for an all solid state battery except that it does not contain a binder.

When only the positive electrode is the above-described positive electrode for an all-solid battery, the negative electrode active material layer included in the negative electrode in the all-solid battery according to the present invention may contain only the negative electrode active material. In addition, it may contain at least one of the above-described conductive material and binder. For example, when the negative electrode active material has a foil shape, a negative electrode active material layer containing only the negative electrode active material can be obtained. On the other hand, when the negative electrode active material is in a powder form, a negative electrode active material layer having a negative electrode active material and a binder can be obtained.
About another point, it is the same as that of the negative electrode for all-solid-state batteries mentioned above except not containing a binder.

FIG. 2A shows a part of an all-solid battery according to the present invention, in which the solid electrolyte layer 1 is sandwiched between the above-described positive electrode for an all-solid battery and the negative electrode for an all-solid battery, and is restrained with a relatively strong force. It is the figure which showed typically the cross section cut | disconnected in the lamination direction about the typical example of the laminated body.
The typical example 200 includes a solid electrolyte layer 1, a positive electrode, and a negative electrode. The solid electrolyte layer 1 includes a lithium ion conductive solid electrolyte 4. The positive electrode includes a positive electrode active material layer 2 including a positive electrode active material 5, a lithium ion conductive solid electrolyte 4, and a binder 12. The negative electrode includes a negative electrode active material layer 3 including a negative electrode active material 6, a lithium ion conductive solid electrolyte 4, and a binder 12. The typical example 200 shown in FIG. 2A is restrained by a relatively strong pressure from both sides in the stacking direction, as indicated by an arrow 7.
On the other hand, FIG. 2B is a diagram schematically showing a cross section cut in the stacking direction of the above-described typical example 200 restrained by a relatively weak pressure. As shown in FIG. 2B, in the present typical example 200, the electrode materials are connected to each other by the binder, so that the spring back can be suppressed and the filling rate of the all-solid battery can be prevented from being lowered. Therefore, the present typical example 200 can prevent an increase in internal resistance and a decrease in output regardless of the restraining pressure.

  Hereinafter, the solid electrolyte layer used in the all solid state battery according to the present invention and the battery case suitably used will be described in detail.

The solid electrolyte layer used in the present invention is held between the positive electrode and the negative electrode, and has a function of exchanging metal ions between the positive electrode and the negative electrode.
As the solid electrolyte, in addition to the above-described sulfide-based solid electrolyte and oxide-based solid electrolyte, a polymer electrolyte or the like can be used.
The polymer electrolyte usually contains a lithium salt and a polymer. Examples of lithium salts include inorganic lithium salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ and LiAsF ₆ ; LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ (Li-TFSI), LiN (SO ₂ C ₂ F ₅ ) ₂ and organic lithium salts such as LiC (SO ₂ CF ₃ ) ₃ . The polymer is not particularly limited as long as it forms a complex with a lithium salt, and examples thereof include polyethylene oxide.
Only one type of solid electrolyte may be used alone, or two or more types may be used in combination.

  The all solid state battery of the present invention may be pressure molded so that the positive electrode, the negative electrode, and the solid electrolyte layer are integrated. The method of pressure molding is not particularly limited, and a known method can be employed.

  The all solid state battery according to the present invention usually includes a battery case that houses a positive electrode, a negative electrode, a solid electrolyte layer, and the like. Specific examples of the shape of the battery case include a coin type, a flat plate type, a cylindrical type, and a laminate type.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples.

1. Preparation of negative electrode for all solid state battery [Example 1]
9.06 mg of graphite (manufactured by Mitsubishi Chemical) as a negative electrode active material and 8.24 mg of 75Li ₂ S · 25P ₂ S ₅ as a solid electrolyte were weighed and mixed. The mixture was further mixed with SUS powder (particle size: 8 to 10 μm) as a binder so as to be 3% by volume with respect to the total volume of the mixture.
The negative electrode composite in a mold having a bottom area 1 cm ² to 30mg weighed and pressed at 4 ton / cm ^2. Then, it restrained by 450 kgf / cm < ² > and produced the negative electrode for all-solid-state batteries of Example 1. FIG.

[Example 2]
The process up to the preparation of the negative electrode mixture is the same as in Example 1.
The negative electrode composite in a mold having a bottom area 1 cm ² to 30mg weighed and pressed at 4 ton / cm ^2. Then, it restrained by 15 kgf / cm < ² > and the negative electrode for all-solid-state batteries of Example 2 was produced.

[Comparative Example 1]
A negative electrode mixture was prepared in the same manner as in Example 1 except that SUS powder was not added.
The negative electrode composite in a mold having a bottom area 1 cm ² to 30mg weighed and pressed at 4 ton / cm ^2. Then, it restrained by 450 kgf / cm < ² > and produced the negative electrode for the all-solid-state battery of the comparative example 1. FIG.

[Comparative Example 2]
A negative electrode mixture was prepared in the same manner as in Example 1 except that SUS powder was not added.
The negative electrode composite in a mold having a bottom area 1 cm ² to 30mg weighed and pressed at 4 ton / cm ^2. Then, it restrained by 15 kgf / cm < ² > and produced the negative electrode for all-solid-state batteries of the comparative example 2.

2. Measurement of Filling Ratio and Young's Modulus of Negative Electrode for All Solid Battery The filling ratio and Young's modulus of the negative electrode for all solid battery of Example 1 to Example 2 and Comparative Example 1 to Comparative Example 2 were measured.
The measurement conditions for the filling rate are as follows. First, an empty restraining jig is restrained with the same pressure as the restraining pressure applied to the sample to be measured (Example 1 and Comparative Example 1: 450 kgf / cm ² , Example 2 and Comparative Example 2: 15 kgf / cm ² ), The dial gauge was adjusted to zero. Next, the amount of the negative electrode mixture for a thickness of 200 mm was calculated from the specific gravity of each raw material of the negative electrode mixture, and weighed. In addition, the jig insertion part was φ 11.28 mm (1 cm ² ). Subsequently, the negative electrode composite material weighed was put into a restraining jig, and pressure-molded at 4 ton / cm ² . The restraint jig after press molding was restrained by the above pressure (Example 1 and Comparative Example 1: 450 kgf / cm ² , Example 2 and Comparative Example 2: 15 kgf / cm ² ), and the height of the sample was measured with a dial gauge. Was measured, and the filling rate was calculated from the specific gravity.
The filling factor was measured at room temperature (15 to 25 ° C.) in an argon atmosphere.

The measurement conditions for Young's modulus are as follows. For the measurement, a micro compression tester (manufactured by Shimadzu Corporation, model number: MCT-211) was used. The Young's modulus was measured at room temperature (15 to 25 ° C.) in an argon atmosphere.
First, a sample (φ11.28 mm (1 cm ² ), pellet of t = 200 mm) used for the filling rate measurement was taken out from the restraining jig. Next, the pellet was placed in a cylindrical jig having an inner diameter of φ10 mm, and the center of the pellet was pushed with the indenter of the tester to measure the displacement. The Young's modulus was calculated from the measured displacement and the pressure applied to the pellet.

FIG. 3 is a graph showing the filling rates of the negative electrodes for all solid state batteries of Example 1 to Example 2 and Comparative Example 1 to Comparative Example 2. FIG. 3 is a graph in which the vertical axis represents the filling rate (%) and the horizontal axis represents the binder addition ratio (volume%). In FIG. 3, the black square plot indicates the filling rate of the negative electrode for all solid state batteries constrained at 450 kgf / cm ² , and the black triangle plot indicates the filling rate of the negative electrode for all solid state batteries constrained at 15 kgf / cm ^2. .
As can be seen from FIG. 3, the filling rate of Comparative Example 1 (binding agent addition ratio: 0% by volume, restraining pressure: 450 kgf / cm ² ) is 97.3%. Moreover, the filling rate of Comparative Example 2 (binding agent addition ratio: 0% by volume, restraining pressure: 15 kgf / cm ² ) is 92.6%. Therefore, the difference in filling factor between Comparative Example 1 and Comparative Example 2 is 4.7%.
On the other hand, as can be seen from FIG. 3, the filling rate of Example 1 (binding agent addition ratio: 3% by volume, restraint pressure: 450 kgf / cm ² ) is 96.2%. Moreover, the filling rate of Example 2 (binder addition ratio: 3 volume%, restraint pressure: 15 kgf / cm ² ) is 95.7%. Therefore, the difference in filling rate between Example 1 and Example 2 is 0.5%.
From the above, when 3% by volume of the binder was added (Example 1 and Example 2), the filling rate due to the difference in restraint pressure was higher than when no binder was added (Comparative Example 1 and Comparative Example 2). The difference is very small. From this result, it is suggested that the electrode materials containing the binder are held together by the press at the time of production, and the spring back is suppressed when the restraining pressure is weakened.

FIG. 4 shows the total solids of Example 1 (Binder addition ratio: 3% by volume, restraint pressure: 450 kgf / cm ² ) and Comparative Example 1 (Binder addition ratio: 0% by volume, restraint pressure: 450 kgf / cm ² ). It is the bar graph which showed the Young's modulus of the negative electrode for batteries.
As can be seen from FIG. 4, the Young's modulus of Comparative Example 1 is 0.080 GPa. On the other hand, the Young's modulus of Example 1 is 0.748 GPa. Therefore, the Young's modulus of Example 1 to which 3% by volume of the binder was added exceeded 9 times the Young's modulus of Comparative Example 1 to which no binder was added, and the negative electrode for the all-solid-state battery of Example 1 was a comparative example. It can be seen that the mechanical strength is superior to 1.

3. Production of all-solid battery [Example 3]
LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (Nichia Chemical) 12.03 mg as a positive electrode active material, 0.51 mg of vapor grown carbon fiber (VGCF, Showa Denko) as a conductive material, solid As an electrolyte, 5.03 mg of 75Li ₂ S · 25P ₂ S ₅ was weighed and mixed to prepare a positive electrode mixture.
Next, 9.06 mg of graphite (manufactured by Mitsubishi Chemical) as the negative electrode active material and 8.24 mg of 75Li ₂ S · 25P ₂ S ₅ as the solid electrolyte were weighed and mixed. The mixture was further mixed with SUS powder (particle size: 8 to 10 μm) as a binder so as to be 3% by volume with respect to the total volume of the mixture.
75Li ₂ S · 25P ₂ S ₅ was used for the solid electrolyte layer.

The mold bottom area 1 cm ^2, the solid electrolyte _{(75Li 2 S · 25P 2 S} 5) and 50mg weighed to form a pressed solid electrolyte layer at 1 ton / cm ^2. Next, 19.5 mg of the positive electrode mixture was added to one side of the solid electrolyte layer, and pressed at 1 ton / cm ² to form a positive electrode active material layer. Subsequently, 18.5 mg of the negative electrode mixture was added to the surface of the solid electrolyte layer opposite to the surface on which the positive electrode active material layer was formed, and pressed at 4 ton / cm ² to form a negative electrode active material layer.
An aluminum foil (made of Japanese foil, thickness 15 μm) is used as the positive electrode current collector from the positive electrode active material layer side, and the negative electrode active material layer side, with the above laminate comprising the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer. From this, the negative electrode current collector was sandwiched between copper foils (manufactured by Nippon Foil Co., Ltd., thickness: 10 μm) and restrained at 450 kgf / cm ² to produce an all-solid battery of Example 3.

[Example 4]
An all-solid battery of Example 4 was produced in the same manner as in Example 3 except that the restraining pressure was changed from 450 kgf / cm ² to 15 kgf / cm ² .

[Comparative Example 3]
A positive electrode mixture was prepared in the same manner as in Example 3. 75Li ₂ S · 25P ₂ S ₅ was used for the solid electrolyte layer in the same manner as in Example 3. A negative electrode mixture was prepared in the same manner as in Example 3 except that SUS powder was not added.
In the same manner as in Example 3, a solid electrolyte layer and a positive electrode active material layer were formed. Next, 17.1 mg of the negative electrode mixture was added to the surface of the solid electrolyte layer opposite to the surface on which the positive electrode active material layer was formed, and pressed at 4 ton / cm ² to form a negative electrode active material layer.
In the same manner as in Example 3, the above laminate comprising the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer was used as the positive electrode current collector from the positive electrode active material layer side, and the negative electrode current collector was collected from the negative electrode active material layer side. An all-solid-state battery of Comparative Example 3 was fabricated by sandwiching it with a copper foil as an electric body and restraining it with 450 kgf / cm ² .

[Comparative Example 4]
A positive electrode mixture was prepared in the same manner as in Example 3. 75Li ₂ S · 25P ₂ S ₅ was used for the solid electrolyte layer in the same manner as in Example 3. A negative electrode mixture was prepared in the same manner as in Example 3 except that SUS powder was not added.
In the same manner as in Example 3, a solid electrolyte layer and a positive electrode active material layer were formed. Next, 17.1 mg of the negative electrode mixture was added to the surface of the solid electrolyte layer opposite to the surface on which the positive electrode active material layer was formed, and pressed at 4 ton / cm ² to form a negative electrode active material layer.
In the same manner as in Example 3, the above laminate comprising the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer was used as the positive electrode current collector from the positive electrode active material layer side, and the negative electrode current collector was collected from the negative electrode active material layer side. An all-solid-state battery of Comparative Example 4 was produced by sandwiching it with a copper foil as an electric conductor and restraining it with 15 kgf / cm ² .

4). Measurement of direct current internal resistance (DCIR) of all solid state batteries For all solid state batteries of Example 3 to Example 4 and Comparative Example 3 to Comparative Example 4, direct current internal resistance was measured. The measurement conditions of the DC internal resistance are as follows.
Measurement temperature: 25 ° C
Measurement potential: 3.6V
Discharge rate: 3C
Measurement time: 5 seconds Measuring instrument: manufactured by Toyo System Co., Ltd. Model: TOSCAT-3200
Measurement atmosphere: Argon

FIG. 5 is a graph showing the DC internal resistance of all solid state batteries of Example 3 to Example 4 and Comparative Example 3 to Comparative Example 4. FIG. 5 is a graph in which the vertical axis represents DC internal resistance (DCIR, Ω · cm ² ) and the horizontal axis represents restraint pressure (kgf / cm ² ). In FIG. 5, the black square plot indicates the direct current internal resistance of the all solid state battery (Example 3 and Example 4) in which the binder addition ratio in the negative electrode active material layer is 3% by volume, and the black triangle plot indicates the negative electrode. DC internal resistances of all solid state batteries (Comparative Example 3 and Comparative Example 4) containing no binder in the active material layer are shown.
As can be seen from FIG. 5, the direct current internal resistance of Comparative Example 3 (binding agent addition ratio: 0% by volume, restraint pressure: 450 kgf / cm ² ) is 65.5 Ω · cm ² . Moreover, the direct-current internal resistance of Comparative Example 4 (binding agent addition ratio: 0% by volume, restraint pressure: 15 kgf / cm ² ) is 73.7 Ω · cm ² .
On the other hand, as can be seen from FIG. 5, the DC internal resistance of Example 3 (binding agent addition ratio: 3% by volume, restraint pressure: 450 kgf / cm ² ) is 56.8 Ω · cm ² . Further, the direct current internal resistance of Example 4 (binding agent addition ratio: 3% by volume, restraint pressure: 15 kgf / cm ² ) is 61.7 Ω · cm ² .
As described above, the all solid state battery (Example 3 and Example 4) including the negative electrode active material layer containing 3% by volume of the binder is the all solid state battery (Comparative Example 3 and Example 3) including the negative electrode active material layer containing no binder. The DC internal resistance is smaller than in Comparative Example 4). As a result of this, as a result of the press at the time of producing the all-solid-state battery, the electrode materials including the binder are connected to each other, and the density in the negative electrode active material layer is increased. As a result, the internal resistance is reduced regardless of the strength of the restraint pressure. It shows that.

In addition, the internal resistance of Example 3 whose restraint pressure is 450 kgf / cm < ² > is smaller than the internal resistance of Example 4 whose restraint pressure is 15 kgf / cm < ² >. This is because SUS used as a binder is considered to work as a conductive material in the negative electrode active material layer, so that the all-solid-state battery of Example 3 is more charged and discharged than the all-solid-state battery of Example 4. Suggests that However, since the difference in internal resistance between Example 3 and Example 4 is smaller than the difference in internal resistance between Comparative Example 3 and Comparative Example 4, SUS not only functions as a conductive material but also serves as a negative electrode as a binder. It is also considered to have a function of keeping the filling rate in the active material layer high.

DESCRIPTION OF SYMBOLS 1 Solid electrolyte layer 2 Positive electrode active material layer 3 Negative electrode active material layer 4 Lithium ion conductive solid electrolyte 5 Positive electrode active material 6 Negative electrode active material 7 Arrow 8 which shows the direction of a comparatively strong pressure 8 Arrow 9 which shows the direction of a comparatively weak pressure Electrode active material layer 10 Electrode current collector 11 Electrode active material 12 Binder 100 Typical example of electrode for all-solid-state battery according to the present invention 200 Typical example of laminate as part of the all-solid-state battery according to the present invention

Claims (7)

An electrode for an all solid state battery containing at least a powdered electrode active material and a powdered lithium ion conductive solid electrolyte,
An electrode for an all-solid-state battery having a Young's modulus of 0.1 GPa or more and / or a tensile strength of 0.1 MPa or more.   The electrode for an all-solid-state battery according to claim 1, further comprising a binder containing a metal or an alloy.   The all-solid-state battery electrode according to claim 1, wherein the binder contains at least one metal element selected from the group consisting of chromium, titanium, and aluminum.   The all-solid-state battery electrode according to any one of claims 1 to 3, wherein the binder contains a metal or alloy having a Young's modulus of 10 GPa or more and / or a tensile strength of 50 MPa or more.   The electrode for an all solid state battery according to any one of claims 2 to 4, wherein the electrode active material, the lithium ion conductive solid electrolyte, and the binder are pressure-molded so as to be integrated. An all-solid battery comprising a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode,
6. An all-solid battery, wherein at least one of the positive electrode and the negative electrode is an electrode for an all-solid battery according to any one of claims 1 to 5.   The all-solid-state battery of Claim 6 currently pressure-molded so that the said positive electrode, the said negative electrode, and the said solid electrolyte layer may be united.

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