JPWO2013084302A1 - All solid battery - Google Patents

Abstract

An object of the present invention is to provide an all-solid-state battery having a self-restraining force and capable of reducing the size of external restraints.
An all-solid battery having a positive electrode layer containing a positive electrode active material, a negative electrode layer containing a negative electrode active material, and a solid electrolyte layer formed between the positive electrode layer and the negative electrode layer, wherein the negative electrode layer Contains a negative electrode active material in which a carbon-based active material and a metal-based active material are mixed, and the metal-based active material undergoes an alloying reaction with Li to generate a metal represented by the general formula M or the general formula M _x O _y (M is a metal) and the charge and discharge potential of the metal-based active material is more noble than the carbon-based active material, and the capacity occupied by the carbon-based active material in the negative electrode layer The problem is solved by providing an all-solid-state battery characterized in that the ratio is higher than that of the metal-based active material.

Description

  The present invention relates to an all-solid-state battery having self-restraining force and capable of miniaturizing external restraint.

  With the rapid spread of information-related equipment and communication equipment such as personal computers, video cameras, and mobile phones in recent years, development of batteries that are used as power sources has been regarded as important. In the automobile industry, high-power and high-capacity batteries are being developed for electric cars and hybrid cars, and lithium batteries with high energy density are being developed.

  As a negative electrode active material in such a lithium battery, a material containing Si or Sn having a high theoretical capacity has been studied in order to cope with an increase in the capacity of the battery. However, when a negative electrode active material containing Si or Sn is used, the volume change due to expansion and contraction of the active material that occurs during the lithium insertion / release reaction is large.

  Patent Document 1 discloses an all-solid battery having a structure that has a sulfide solid electrolyte as an electrolyte material and improves the energy density while suppressing the increase in size of the all-solid battery.

JP 2011-124084 A

  However, the all-solid-state battery of Patent Document 1 is used in a state of being restrained by applying pressure from the outside, but expansion / contraction due to insertion / desorption of lithium is not considered, and when the volume expansion is large, external restraint is increased. Therefore, there is a problem that further miniaturization of the lithium battery is difficult.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an all-solid-state battery having a self-restraining force and capable of reducing the size of the external restraint.

In order to solve the above problems, in the present invention, a positive electrode layer containing a positive electrode active material, a negative electrode layer containing a negative electrode active material, a solid electrolyte layer formed between the positive electrode layer and the negative electrode layer, The negative electrode layer contains a negative electrode active material obtained by mixing a carbon-based active material and a metal-based active material, and the metal-based active material causes an alloying reaction with Li, A metal represented by the formula M or a metal oxide represented by the general formula M _x O _y (M is a metal), and the charge / discharge potential of the metal-based active material is more noble than the carbon-based active material. The all-solid-state battery is characterized in that the capacity ratio of the carbon-based active material in the negative electrode layer is larger than that of the metal-based active material.

  According to the present invention, since the metal-based active material has a noble potential compared to the carbon-based active material, the insertion reaction of lithium ions occurs earlier than the carbon-based active material in the initial stage of charging, causing volume expansion, and the negative electrode Self-restraining force can be applied inside the layer. For this reason, since the metal-based active material still exists in the subsequent charge (after the initial charge), lithium ions are always inserted into the carbon-based active material with a self-binding force applied to the inside of the negative electrode layer. . Therefore, the external constraint can be reduced in size. Further, according to the present invention, since the capacity ratio of the carbon-based active material in the negative electrode layer is larger than that of the metal-based active material, the cushion for relieving the stress generated when the carbon-based active material expands the metal-based active material. It acts as a material and can suppress expansion of the negative electrode layer.

In the said invention, it is preferable that the capacity | capacitance ratio which the said metal type active material occupies for the said negative electrode layer is below the minimum capacity | capacitance ratio of a battery use area (SOC area | region). By making the capacity ratio of the metal-based active material less than or equal to the minimum capacity ratio of the battery usage range (hereinafter sometimes referred to simply as the SOC region), the metal-based active material into which lithium ions are inserted is charged and discharged. This is because it can be used as a member capable of providing a self-binding force. That is, in the first charge reaction, lithium ions are inserted into the metal-based active material, but since the capacity ratio of the metal-based active material is equal to or less than the minimum capacity ratio of the SOC region (for example, SOC 20%), the subsequent charge / discharge is performed. In the reaction (for example, SOC 20% to 80%), the metal-based active material into which lithium ions are inserted does not contribute to the charge / discharge reaction.
On the other hand, in the SOC region, since the metal-based active material exists with its volume expanded, a self-binding force can always be applied to the negative electrode layer. As a result, input / output characteristics and cycle characteristics are improved.

It is a schematic sectional drawing which shows an example of the all-solid-state battery of this invention. It is a graph which shows the electric potential change with respect to the capacity factor of the negative electrode active material obtained by Example 1, the comparative example 1, and the comparative example 2. FIG. It is a graph which shows the result of the capacity | capacitance maintenance factor at the time of the high rate of the negative electrode active material obtained in Example 2 and Comparative Example 3. It is a graph which shows the result of the capacity | capacitance maintenance factor after the cycle under the low external restraint of the negative electrode active material obtained in Example 2, Comparative Example 3, and Comparative Example 4.

  Hereinafter, the all solid state battery of the present invention will be described in detail.

A. First, the all solid state battery of the present invention will be described. An all solid state battery of the present invention is an all solid having a positive electrode layer containing a positive electrode active material, a negative electrode layer containing a negative electrode active material, and a solid electrolyte layer formed between the positive electrode layer and the negative electrode layer. In the battery, the negative electrode layer contains a negative electrode active material obtained by mixing a carbon-based active material and a metal-based active material, and the metal-based active material causes an alloying reaction with Li, and is represented by the general formula M It is a metal or a metal oxide represented by the general formula M _x O _y (M is a metal), and the charge / discharge potential of the metal-based active material is more noble than the carbon-based active material, and the carbon-based activity The capacity ratio of the material to the negative electrode layer is larger than that of the metal-based active material.

  FIG. 1 is a schematic cross-sectional view showing an example of the all solid state battery of the present invention. An all-solid battery 10 illustrated in FIG. 1 includes a positive electrode layer 1, a negative electrode layer 2, a solid electrolyte layer 3 formed between the positive electrode layer 1 and the negative electrode layer 2, and a positive electrode collector that collects current from the positive electrode layer 1. It has a current collector 4, a negative electrode current collector 5 that collects current from the negative electrode layer 2, and a battery case 6 that houses these members. The negative electrode layer 2 includes a negative electrode active material 11 composed of a carbon-based active material 7 and a metal-based active material 8 and a sulfide solid electrolyte material 9. Here, the “all solid state battery” of the present invention refers to a member containing at least a power generation element composed of the positive electrode layer 1, the negative electrode layer 2, and the solid electrolyte layer 3. Therefore, the all solid state battery of the present invention may be only the power generation element, or may have a positive electrode current collector, a negative electrode current collector, and a battery case as shown in FIG.

  According to the present invention, since the metal-based active material has a noble potential compared to the carbon-based active material, the insertion reaction of lithium ions occurs earlier than the carbon-based active material in the initial stage of charging, causing volume expansion, and the negative electrode Self-restraining force can be applied inside the layer. For this reason, since the metal-based active material still exists in the subsequent charge (after the initial charge), lithium ions are always inserted into the carbon-based active material with a self-binding force applied to the inside of the negative electrode layer. . Therefore, the external constraint can be reduced in size. Further, according to the present invention, since the capacity ratio of the carbon-based active material in the negative electrode layer is larger than that of the metal-based active material, the cushion for relieving the stress generated when the carbon-based active material expands the metal-based active material. It acts as a material and can suppress expansion of the negative electrode layer.

  In addition, the metal-based active material has a higher theoretical capacity than the carbon-based active material, but is characterized by large expansion and contraction due to charge / discharge, while the carbon-based active material has a small volume expansion coefficient. The capacity is inferior to a metal-based active material. ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to obtain the all-solid-state battery which has a high capacity | capacitance and can suppress volume expansion by using combining a metal type active material and a carbon type active material. Furthermore, since carbon-based active materials tend to have less irreversible capacity during initial charging than metal-based active materials, the capacity ratio of carbon-based active materials in the negative electrode layer should be greater than that of metal-based active materials. Thus, an all solid state battery having a smaller irreversible capacity can be obtained.

  Hereinafter, the all solid state battery of the present invention will be described for each configuration.

1. Negative electrode layer The negative electrode layer in the present invention is a layer containing a negative electrode active material obtained by mixing a carbon-based active material and a metal-based active material.

(1) Negative electrode active material The negative electrode active material in the present invention is a mixture of a carbon-based active material and a metal-based active material, and is charged and discharged by inserting and desorbing lithium ions into each active material. Is.
Hereinafter, each structure of the negative electrode active material will be described.

(I) Metal-based active material The metal-based active material in the present invention causes an alloying reaction with Li, and a metal oxide represented by a metal represented by the general formula M or a general formula M _x O _y (M is a metal). The charge / discharge potential is more noble than the carbon-based active material. Here, the alloying reaction refers to a reaction in which a metal oxide or a metal reacts with a metal ion of Li ion to change to a lithium alloy.

The metal-based active material has a higher charge / discharge potential (lithium ion insertion / desorption potential) than the carbon-based active material. Therefore, the lithium ion insertion / release reaction with respect to the metal-based active material occurs before the lithium ion insertion / release reaction with respect to the carbon-based active material. For this reason, although the metal-based active material is in a state where the volume is expanded, the above-described expansion is moderately suppressed by the carbon-based active material described later, and thus the self-binding force is effectively applied inside the negative electrode layer. It becomes possible.
In addition, it can confirm that the said metal type active material has a noble charge / discharge potential more noble than the said carbon type active material by measuring by the cyclic voltammetry method, for example.
Moreover, it is preferable that a metal type active material has a theoretical capacity larger than a carbon type active material. This is because the capacity of the all-solid battery can be improved.

The metal or metal oxide used in the metal-based active material in the present invention is represented by the general formula M or the general formula M _x O _y (M is a metal). In the above general formula, M is Bi, Sb, Sn, Si, Al, Pb, In, Mg, Ti, Zr, V, Fe, Cr, Cu, Co, Mn, Ni, Zn, Nb, Ru, Mo, Sr, Y, Ta, W, or Ag is preferable. In the present invention, Al, Si, and Sn are more preferable, and Al is more preferable.
Al has a relatively large electric capacity, an alloy of Al and lithium is inexpensive and has high performance, has a large plateau region at the potential at the time of lithium ion insertion and desorption, and most of the capacity is larger than the reaction of graphite. This is because it occurs at a noble potential.
Moreover, as a metal oxide in this invention, SiO, SnO, etc. are preferable. In the present invention, M may contain two or more kinds of metals.

Examples of the shape of the metal-based active material in the present invention include a particle shape such as a true sphere and an oval sphere, a needle shape, a thin film shape, and the like. Among these, a particle shape is preferable. The average particle diameter (D ₅₀ ) of the metal-based active material is, for example, preferably in the range of ₅ nm to ₅₀ μm, and more preferably in the range of ₅₀ nm to ₅ μm.

(Ii) Carbon-based active material The carbon-based active material in the present invention has a larger capacity ratio in the negative electrode layer than the metal-based active material described above, and performs charge / discharge by lithium ion insertion / release reaction. Moreover, when a metal type active material produces the expansion | swelling of the volume by the insertion reaction of lithium ion, it has a function which suppresses expansion | swelling moderately as a cushioning material.

The type of the carbon-based active material in the present invention is preferably one having a softness that can moderately relieve stress generated when the metal-based active material expands and contracts. For example, natural graphite (graphite) and its improved body Artificial graphite (for example, MCMB), non-graphitizable material (hard carbon), easily graphitizable material (soft carbon), and the like can be mentioned. Among them, it is preferable to use graphite. This is because the crystallinity is high and the theoretical capacity is relatively high.
In addition, the carbon-based active material in the present invention preferably has a lower volume expansion coefficient than the metal-based active material. This is because it is easy to make the external restraint smaller.

Examples of the shape of the carbon-based active material in the present invention include a particle shape such as a true sphere and an oval sphere, and a thin film shape. Among these, a particle shape is preferable. Moreover, when a carbon type active material is a particle shape, it is preferable that the average particle diameter exists in the range of 0.1 micrometer-100 micrometers, and it is more preferable that it exists in the range of 1 micrometer-50 micrometers.
If the particle size of the carbon-based active material is too large, the resistance may increase at the contact portion with the solid electrolyte material described later. On the other hand, if the particle size of the carbon-based active material is too small, the particle size is larger than that of the solid electrolyte. This is because a carbon-based active material having a small diameter and poor lithium ion conduction is generated.

The negative electrode layer in the present invention contains a carbon-based active material and a metal-based active material. The mass ratio of both is not particularly limited because it varies depending on the specific gravity, the maximum capacity of lithium ions, and the like. Especially, it is preferable that a metal type active material exists in the range of 0.1 mass part-200 mass parts with respect to 100 mass parts of carbon type active materials, and exists in the range of 1 mass part-100 mass parts. Is more preferable, and it is still more preferable to be in the range of 5 to 50 parts by mass.
This is because if the content of the metal-based active material is too large, the carbon-based active material may not be able to suppress the volume expansion of the metal-based active material. On the other hand, if the content of the metal-based active material is too small, the relative proportion of the metal-based active material is reduced, and the capacity of the carbon-based active material is smaller than that of the metal-based active material, so the capacity of the negative electrode layer is improved. Because there is a possibility of not.

(Iii) Negative electrode active material (a) Capacity ratio In the present invention, one characteristic is that the capacity ratio of the carbon-based active material to the negative electrode layer is usually larger than that of the metal-based active material.
The volume ratio of the carbon-based active material to the total capacity of the carbon-based active material and the metal-based active material is, for example, preferably in the range of 50% to 95%, and in the range of 70% to 95%. Is more preferable.
On the other hand, the volume ratio of the metal-based active material to the total capacity of the carbon-based active material and the metal-based active material is, for example, preferably in the range of 5% to 50%, and in the range of 5% to 30%. More preferably.
Further, the difference between the volume ratio of the carbon-based active material and the volume ratio of the metal-based active material with respect to the total capacity of the carbon-based active material and the metal-based active material is preferably 10% or more, for example, 10% to More preferably, it is within the range of 45%.

  Furthermore, the capacity ratio of the metal-based active material in the negative electrode layer is preferably not more than the minimum capacity ratio of the SOC region. By making the capacity ratio of the metal-based active material not more than the minimum capacity ratio of the battery use area (SOC area), the metal-based active material into which lithium ions are inserted does not contribute to the charge / discharge reaction, and further This is because it can be used as a member capable of applying a restraining force. That is, in the first charge reaction, lithium ions are inserted into the metal-based active material, but since the capacity ratio of the metal-based active material is equal to or less than the minimum capacity ratio of the SOC region (for example, SOC 20%), the subsequent charge / discharge is performed. In the reaction (for example, SOC 20% to 80%), the metal-based active material into which lithium ions are inserted does not contribute to the charge / discharge reaction. On the other hand, in the SOC region, since the metal-based active material exists with its volume expanded, a self-binding force can always be applied to the negative electrode layer. As a result, input / output characteristics and cycle characteristics are improved.

  Here, the relationship between the SOC region of the all-solid battery and the capacity ratio of the negative electrode active material contained in the all-solid battery will be described. Usually, an all-solid-state battery is used by determining an SOC region, which is a capacity region to be used, and controlling within that range. For example, in an in-vehicle battery or the like, various settings such as SOC 20% -80%, SOC 10% -80%, SOC 20% -90% are set. For example, an all solid state battery set with SOC 20% -80% indicates that the battery capacity is actually used in the range of 20% to 80%. The all solid state battery of the present invention may be used, for example, at an SOC of 5% or more, an SOC of 10% or more, or an SOC of 20% or more.

  Moreover, it is preferable to adjust the capacity | capacitance ratio of the negative electrode active material contained according to especially the minimum capacity | capacitance ratio of the SOC area | region set to the all-solid-state battery used. For example, in the case of an all-solid battery set to SOC 20% or more, the capacity ratio of the metal-based active material in the negative electrode layer is preferably within a range of 10% to 20%, and within a range of 10% to 18%. It is more preferable that

(B) Others Although content of the negative electrode active material in the negative electrode layer in this invention is not specifically limited, For example, it is preferable to exist in the range of 1 mass%-50 mass%, and 5 mass%- More preferably, it is in the range of 10% by mass.
When the amount is less than the above range, the amount of the negative electrode active material that inserts and desorbs lithium ions is small, which may reduce the volume capacity. On the other hand, when the amount is larger than the above range, the ionic conductivity may be reduced and input / output may be lowered.

(2) Solid electrolyte material It is preferable that the negative electrode layer in this invention contains the solid electrolyte material. This is because the ion conductivity in the negative electrode layer can be improved by adding the solid electrolyte material. In the present invention, when the self-binding force acts in the negative electrode layer, the contact between the negative electrode active material and the solid electrolyte material is improved. That is, input / output and cycle characteristics can be improved.

  The solid electrolyte material in the present invention is not particularly limited as long as it has lithium ion conductivity. For example, sulfide solid electrolyte material, oxide solid electrolyte material, nitride solid electrolyte material, halide solid electrolyte Inorganic solid electrolyte materials such as materials can be mentioned. In the present invention, it is preferable to use a sulfide solid electrolyte material and an oxide solid electrolyte material, and it is particularly preferable to use a sulfide solid electrolyte material. The sulfide solid electrolyte material is preferable in terms of high ion conductivity, and the oxide solid electrolyte material is preferable in terms of high chemical stability. The halide solid electrolyte material refers to an inorganic solid electrolyte material containing halogen.

  The sulfide solid electrolyte material usually contains at least lithium element (Li) and sulfur (S). In particular, the sulfide solid electrolyte material preferably contains Li, A (A is at least one selected from the group consisting of P, Si, Ge, Al, and B) and S. The sulfide solid electrolyte material may contain a halogen such as Cl, Br, or I. By containing halogen, ion conductivity can be improved. The sulfide solid electrolyte material may contain O. By containing O, chemical stability can be improved.

Examples of the sulfide solid electrolyte material include Li ₂ S—P ₂ S ₅ , Li ₂ S—P ₂ S ₅ —LiI, Li ₂ S—P ₂ S ₅ —Li ₂ O, and Li ₂ S—P ₂ S. _{5 -Li 2 O-LiI, Li} 2 S-SiS 2, Li 2 S-SIS 2 -LiI, Li 2 S-SiS 2 -LiBr, Li 2 S-SiS 2 -LiCl, Li 2 S-SiS 2 -B _{2 S 3 -LiI, Li 2 S} -SiS 2 -P 2 S 5 -LiI, Li 2 S-B 2 S 3, Li 2 S-P 2 S 5 -Z m S n ( however, m, n are positive Z is one of Ge, Zn, and Ga.), Li ₂ S—GeS ₂ , Li ₂ S—SiS ₂ —Li ₃ PO ₄ , Li ₂ S—SiS ₂ —Li _x MO _y (where, x and y are positive numbers, M is P, Si, Ge, B, Al, Ga, I One of the.), And the like can be given. The description of “Li ₂ S—P ₂ S ₅ ” means a sulfide solid electrolyte material using a raw material composition containing Li ₂ S and P ₂ S _5, and the same applies to other descriptions. is there.

Also, the sulfide solid electrolyte material, if it is made by using the raw material composition containing Li ₂ S and _P 2 _{S 5,} the proportion of Li ₂ S to the total of Li ₂ S and _P 2 _{S 5} is For example, it is preferably in the range of 70 mol% to 80 mol%, more preferably in the range of 72 mol% to 78 mol%, and still more preferably in the range of 74 mol% to 76 mol%. This is because a sulfide solid electrolyte material having an ortho composition or a composition in the vicinity thereof can be obtained, and a sulfide solid electrolyte material having high chemical stability can be obtained. Here, ortho generally refers to one having the highest degree of hydration among oxo acids obtained by hydrating the same oxide. In the present invention, the crystal composition in which Li ₂ S is added most in the sulfide is called the ortho composition. In the Li ₂ S—P ₂ S ₅ system, Li ₃ PS ₄ corresponds to the ortho composition. In the case of a Li ₂ S—P ₂ S ₅ -based sulfide solid electrolyte material, the ratio of Li ₂ S and P ₂ S ₅ to obtain the ortho composition is Li ₂ S: P ₂ S ₅ = 75: 25 on a molar basis. It is. Instead of _P 2 _{S 5} in the raw material composition, even when using the _Al 2 _{S 3,} or _B 2 _{S 3,} a preferred range is the same. In the Li ₂ S—Al ₂ S ₃ system, Li ₃ AlS ₃ corresponds to the ortho composition, and in the Li ₂ S—B ₂ S ₃ system, Li ₃ BS ₃ corresponds to the ortho composition.

Also, the sulfide solid electrolyte material, if it is made by using the raw material composition containing Li ₂ S and SiS _2, the ratio of Li ₂ S to the total of Li ₂ S and SiS _2, for example 60 mol% ~ It is preferably within the range of 72 mol%, more preferably within the range of 62 mol% to 70 mol%, and even more preferably within the range of 64 mol% to 68 mol%. This is because a sulfide solid electrolyte material having an ortho composition or a composition in the vicinity thereof can be obtained, and a sulfide solid electrolyte material having high chemical stability can be obtained. In the Li ₂ S—SiS ₂ system, Li ₄ SiS ₄ corresponds to the ortho composition. In the case of a Li ₂ S—SiS ₂ -based sulfide solid electrolyte material, the ratio of Li ₂ S and SiS ₂ to obtain the ortho composition is Li ₂ S: SiS ₂ = 66.7: 33.3 on a molar basis. . Instead of SiS ₂ in the raw material composition, even when using a GeS _2, the preferred range is the same. In the Li ₂ S—GeS ₂ system, Li ₄ GeS ₄ corresponds to the ortho composition.

Moreover, when the sulfide solid electrolyte material is formed using a raw material composition containing LiX (X = Cl, Br, I), the ratio of LiX is, for example, in the range of 1 mol% to 60 mol%. It is preferably within a range of 5 mol% to 50 mol%, more preferably within a range of 10 mol% to 40 mol%. Also, the sulfide solid electrolyte material, if it is made by using the raw material composition containing Li ₂ O, the ratio of Li ₂ O is, for example, is preferably in the range of 1 mol% 25 mol%, More preferably, it is in the range of 3 mol% to 15 mol%.

The sulfide solid electrolyte material may be sulfide glass, crystallized sulfide glass, or a crystalline material obtained by a solid phase method. The sulfide glass can be obtained, for example, by performing mechanical milling (ball mill or the like) on the raw material composition. Crystallized sulfide glass can be obtained, for example, by subjecting sulfide glass to a heat treatment at a temperature equal to or higher than the crystallization temperature. Moreover, the lithium ion conductivity at normal temperature of the sulfide solid electrolyte material is, for example, preferably 1 × 10 ⁻⁵ S / cm or more, and more preferably 1 × 10 ⁻⁴ S / cm or more.

On the other hand, examples of the oxide solid electrolyte material include a compound having a NASICON type structure. As an example of a compound having a NASICON type structure, a compound represented by the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 2) can be given. Among them, the oxide solid electrolyte material _is preferably _{Li 1.5 Al 0.5 Ge 1.5 (PO} 4) _3. Another example of the compound having a NASICON structure is a compound represented by the general formula Li _{1 + x} Al _x Ti _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 2). Among them, the oxide solid electrolyte material _is preferably _{Li 1.5 Al 0.5 Ti 1.5 (PO} 4) _3. Other examples of the oxide solid electrolyte material include LiLaTiO (for example, Li _0.34 La _0.51 TiO ₃ ), LiPON (for example, Li _2.9 PO _3.3 N _0.46 ), LiLaZrO ( for _example, mention may be made of _{Li 7 La 3 Zr 2 O 12} ) or the like.

Examples of the shape of the solid electrolyte material in the present invention include particles and thin films. The average particle diameter (D ₅₀ ) of the solid electrolyte material is preferably in the range of 1 nm to 100 μm, for example, and more preferably in the range of 10 nm to 30 μm.
Further, the content of the solid electrolyte material in the negative electrode layer is not particularly limited, but is preferably in the range of 10% by mass to 90% by mass, for example.

(3) Negative electrode layer The negative electrode layer in the present invention may further contain at least one of a binder and a conductive agent, if necessary.
The conductive agent is not particularly limited. For example, carbon materials such as mesocarbon microbeads (MCMB), acetylene black, ketjen black, carbon black, coke, carbon fiber, vapor-grown carbon, and graphite. Can be mentioned. Examples of the binder include polyimide, polyamideimide, polyacrylic acid and the like.
In addition, the thickness of the negative electrode layer in the present invention is, for example, preferably in the range of 0.1 μm to 1000 μm, and more preferably in the range of 1 μm to 100 μm.

  As a method for forming the negative electrode layer in the present invention, a general method can be used. For example, a negative electrode layer forming paste containing the negative electrode active material, the solid electrolyte material, the binder, and the conductive agent described above is applied onto a negative electrode current collector, which will be described later, and then dried. By doing so, a negative electrode layer can be formed.

2. Positive electrode layer The positive electrode layer in the present invention is a layer containing at least a positive electrode active material, and in the positive electrode active material, lithium ion insertion / release reaction occurs to cause charge / discharge.

(1) Positive electrode active material The type of the positive electrode active material of the positive electrode layer in the present invention is appropriately selected according to the type of the all-solid battery, and examples thereof include an oxide active material and a sulfide active material. Examples of the positive electrode active material include layered positive electrode active materials such as LiCo ₂ , LiNiO ₂ , LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , LiVO ₂ , LiCrO ₂ , LiMn ₂ O ₄ , Li (Ni _{0). .25} Mn _0.75 ) ₂ O ₄ , LiCoMnO ₄ , Li ₂ NiMn ₃ O _{8 and} other spinel positive electrode active materials, LiCoPO ₄ , LiMnPO ₄ and LiFePO _{4 and} other olivine positive electrode active materials, Li ₃ V ₂ P ₃ A NASICON type positive electrode active material such as O ₁₂ can be used.

Examples of the shape of the positive electrode active material include particles and thin films. The average particle diameter (D ₅₀ ) of the positive electrode active material is, for example, preferably in the range of 1 nm to 100 μm, and more preferably in the range of 10 nm to 30 μm.

  The content of the positive electrode active material in the positive electrode layer in the present invention is not particularly limited, but is preferably in the range of 40% by mass to 99% by mass, for example.

(2) Positive electrode layer The positive electrode layer may contain a solid electrolyte material. This is because the inclusion of the solid electrolyte material allows the positive electrode active material and the solid electrolyte material to be in contact with each other, thereby improving the ionic conductivity of the positive electrode layer. The solid electrolyte material is the same as that described in the above section “1. Negative electrode layer”, and thus the description thereof is omitted here. Although content of the solid electrolyte material in a positive electrode layer is not specifically limited, For example, it is preferable to exist in the range of 10 mass%-90 mass%.

The positive electrode layer in the present invention may further contain at least one of a conductive agent and a binder, and the contents described in the above section “1. Negative electrode layer” regarding the conductive agent and the binder. The description is omitted here.
The thickness of the positive electrode layer is, for example, preferably in the range of 0.1 μm to 1000 μm, and more preferably in the range of 1 μm to 100 μm.

  As a method for forming the positive electrode layer in the present invention, a general method can be used. For example, a positive electrode layer forming paste containing a positive electrode active material, a solid electrolyte material, a binder, and a conductive agent is applied on a positive electrode current collector, which will be described later, dried, and then pressed. Thus, a positive electrode layer can be formed.

3. Solid electrolyte layer The solid electrolyte layer in this invention is demonstrated. The solid electrolyte layer in the present invention is a layer formed between the positive electrode layer and the negative electrode layer, and is a layer containing at least a solid electrolyte material. Lithium ions are conducted between the positive electrode active material and the negative electrode active material through the solid electrolyte material.

(1) Solid electrolyte material Examples of the solid electrolyte material in the present invention include inorganic solid electrolyte materials such as sulfide solid electrolyte materials, oxide solid electrolyte materials, nitride solid electrolyte materials, and halide solid electrolyte materials. In particular, it is preferable to use the same material as the solid electrolyte material used in “1. Negative electrode layer” described above. In addition, since it is the same as that of the content described in "1. Negative electrode layer" about solid electrolyte material, description here is abbreviate | omitted. The content of the solid electrolyte material contained in the solid electrolyte layer in the present invention is, for example, preferably 60% by mass or more, more preferably 70% by mass or more, and 80% by mass or more. Is particularly preferred.

(2) Solid electrolyte layer The solid electrolyte layer in this invention may contain the binder and may be comprised only from the solid electrolyte material. The thickness of the solid electrolyte layer varies greatly depending on the configuration of the all-solid-state battery. For example, the thickness of the solid electrolyte layer is preferably in the range of 0.1 μm to 1000 μm, and more preferably in the range of 0.1 μm to 300 μm. preferable.

  A general method can be used as the method for forming the solid electrolyte layer in the present invention. For example, the solid electrolyte layer can be formed by pressing a solid electrolyte layer forming material containing a solid electrolyte material and a binder.

4). Other Configurations The all solid state battery of the present invention has at least the positive electrode layer, the negative electrode layer, and the solid electrolyte layer described above, and further includes a positive electrode current collector that collects current from the positive electrode layer, and a negative electrode layer. You may have the negative electrode electrical power collector which collects electric current. Examples of the material for the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, and carbon. On the other hand, examples of the material for the negative electrode current collector include SUS, copper, nickel, and carbon.
In addition, the thickness and shape of the positive electrode current collector and the negative electrode current collector are preferably appropriately selected according to the use of the all solid state battery.

  As the battery case in the present invention, a general battery case of an all-solid battery can be used. Examples of the battery case include a SUS battery case.

5. All-solid battery The all-solid battery of the present invention may be a primary battery or a secondary battery, but among them, a secondary battery is preferred. It can be charged and discharged repeatedly, and is useful, for example, as an in-vehicle battery. Examples of the shape of the all solid state battery include a coin type, a laminate type, a cylindrical type, and a square type.

  The method for producing an all-solid battery of the present invention is not particularly limited as long as it is a method capable of obtaining the above-described all-solid battery, and a method similar to a general method for producing an all-solid battery may be used. Examples thereof include a pressing method, a coating method, a vapor deposition method, and a spray. When manufacturing an all-solid battery using the pressing method, first, a material constituting the solid electrolyte layer is pressed to form a solid electrolyte layer, and a material constituting the positive electrode layer is formed on one surface of the solid electrolyte layer. The positive electrode layer is formed by adding and pressing together with the positive electrode current collector, and then the material constituting the negative electrode layer is added to the other surface of the solid electrolyte layer negative electrode layer. The method of obtaining an all-solid-state battery by forming a negative electrode layer by pressing together and coat | covering the circumference | surroundings of the obtained electric power generation element with an exterior body is illustrated.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

[Synthesis example]
(Synthesis of sulfide solid electrolyte materials)
As starting materials, lithium sulfide (Li ₂ S, manufactured by Nippon Chemical Industry Co., Ltd.) and diphosphorus pentasulfide (P ₂ S ₅ , manufactured by Aldrich) were used. Next, in a glove box under an Ar atmosphere (dew point −70 ° C.), Li ₂ S and P ₂ S ₅ have a molar ratio of 75Li ₂ S · 25P ₂ S ₅ (Li ₃ PS ₄ , ortho composition). Weighed as follows. 2 g of this mixture was mixed for 5 minutes in an agate mortar. Then, 2 g of the obtained mixture was put into a planetary ball mill container (45 cc, made of ZrO ₂ ), 4 g of dehydrated heptane (moisture content of 30 ppm or less) was added, and 53 g of ZrO ₂ balls (φ = 5 mm) were added. The container was completely sealed (Ar atmosphere). This container was attached to a planetary ball mill (P7 made by Fritsch), and mechanical milling was performed for 40 hours at a base plate rotation speed of 500 rpm. Then, the obtained sample was dried so as to remove heptane on a hot plate to obtain a sulfide solid electrolyte material (75Li ₂ S · 25P ₂ S ₅ glass).

[Example 1]
(Preparation of negative electrode active material)
Graphite (Mitsubishi Chemical Co., Ltd.) 860 mg and Al powder (Sigma Aldrich Co.) 71 mg were weighed and mixed to obtain a negative electrode active material.
Next, 860 mg of the sulfide solid electrolyte material 75Li ₂ S-25P ₂ S ₅ prepared in the synthesis example was weighed and mixed with the above-described negative electrode active material to obtain a negative electrode layer forming material.

(Preparation of single electrode evaluation battery)
On one surface of the solid electrolyte layer formed using 100 mg of the sulfide solid electrolyte material 75Li ₂ S · 25P ₂ S ₅ prepared in the synthesis example, an active layer is formed using 15 mg of the negative electrode layer forming material, and then A counter electrode was formed on the other surface of the solid electrolyte layer using metallic lithium to produce a single electrode evaluation battery.

[Comparative Example 1]
Using 930 mg of graphite as the negative electrode active material, the negative electrode active material and the sulfide solid electrolyte material prepared in Synthesis Example were mixed to obtain a negative electrode layer forming material. Using 17 mg of this negative electrode layer forming material, a single electrode evaluation battery was obtained in the same manner as in Example 1.

[Comparative Example 2]
Using 930 mg of Al as the negative electrode active material, the negative electrode active material was mixed with the sulfide solid electrolyte material prepared in Synthesis Example to obtain a negative electrode layer forming material. Using 6.5 mg of this negative electrode layer forming material, a single electrode evaluation battery was obtained in the same manner as in Example 1.

[Evaluation 1]
(First irreversible efficiency)
Using the unipolar evaluation batteries obtained in Example 1, Comparative Example 1 and Comparative Example 2, at a battery evaluation environmental temperature of 25 ° C., a constant current discharge was performed to a voltage of 0 V at a current rate of 0.1 C, and then the current rate Constant current charging was performed until the voltage reached 1.5 V at 0.1 C. The weight capacity at this time, the volume capacity before expansion, and the initial irreversible rate were measured. The results are shown in Table 1.

As Table 1 shows, since the working electrode obtained in Example 1 contains Al having a high capacity, the weight capacity and the volume capacity before expansion can be improved as compared with Comparative Example 1 made of only graphite.
In addition, it is suggested that the working electrode obtained in Example 1 has a lower value of the initial irreversibility rate than the working electrode of Comparative Example 2 made of only Al, and is suppressed to a value almost unchanged from Comparative Example 1. . That is, it is considered that by adding graphite to Al, the graphite becomes a buffer material and suppresses the influence of Al expansion and contraction.

[Evaluation 2]
(Negative potential during battery discharge)
For the unipolar evaluation batteries obtained in Example 1, Comparative Example 1 and Comparative Example 2, the lithium insertion / extraction potential with respect to the total capacity ratio in the above-described charge / discharge was measured. The result is shown in FIG.

As shown in FIG. 2B, when the potential changes of Comparative Example 1 and Comparative Example 2 are compared, the negative electrode active material of Comparative Example 2 is more lithium than the negative electrode active material of Comparative Example 1 that is graphite. Since the potential of insertion / desorption is noble, it is suggested that lithium ions are inserted into Al first when the battery is charged, while lithium is desorbed from Al later than graphite when the battery is discharged. As shown in FIG. 2A, in Example 1 containing the negative electrode active material in which Al and graphite are mixed, the volume ratio of Al is mixed to 20% or less of SOC. When the lithium ion insertion reaction occurs first and the SOC is 20% or more, all Al is filled with lithium ions and is expanded. That is, it is considered that only the lithium insertion / extraction reaction to graphite occurs when the SOC is 20% or more. Further, since a plateau appears at 0.5 V vs Li / Li ⁺ near SOC 80%, it is considered that lithium ions are desorbed from Al after desorption of lithium ions from graphite. That is, it is presumed that self-restraining force is applied in the negative electrode layer by expanding all of Al at the initial stage of charging.

[Example 2]
(Preparation of positive electrode layer forming material)
As a positive electrode active material, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (manufactured by Nichia Chemical) 600 mg, as a conductive agent, VGCF (manufactured by Showa Denko) 25.5 mg, and as a solid electrolyte material Then, 250 mg of 75Li ₂ S-25P ₂ S ₅ prepared in the synthesis example was weighed and mixed to obtain a positive electrode layer forming material.
(Production of all-solid battery)

50 mg of the sulfide solid electrolyte material 75Li ₂ S-25P ₂ S ₅ prepared in the synthesis example was weighed, put into a 1 cm ² mold, and pressed at 1 ton / cm ² to form a solid electrolyte layer. The positive electrode layer was formed by adding 19 mg of said positive electrode layer forming material to one surface side of the obtained solid electrolyte layer, and pressing at 1 ton / cm < ² >. Next, 15 mg of the negative electrode layer forming material prepared in Example 1 was added to the other surface side of the solid electrolyte layer, and the negative electrode layer was formed by pressing at 4.3 ton / cm ^2. Obtained.
A 15 μm thick Al foil (manufactured by Nippon Foil Co., Ltd.) as the positive electrode current collector and a 10 μm thick Cu foil (manufactured by Nippon Foil Co., Ltd.) as the negative electrode current collector are disposed on the obtained power generation element, and all solid A battery was obtained.
In addition, the SOC area | region of the all-solid-state battery obtained in Example 2 shall be SOC20% -80%.

[Comparative Example 3]
In the production of the all solid state battery of Example 2, an all solid state battery was obtained in the same manner as in Example 2 except that 17 mg of the negative electrode layer forming material prepared in Comparative Example 1 was used to form the negative electrode layer.
In addition, the SOC area | region of the all-solid-state battery obtained by the comparative example 3 shall be SOC20% -80%.

[Comparative Example 4]
In the production of the all-solid battery of Example 2, an all-solid battery was obtained in the same manner as in Example 2, except that 6.5 mg of the negative electrode layer forming material prepared in Comparative Example 2 was used to form the negative electrode layer.
In addition, the SOC area | region of the all-solid-state battery obtained by the comparative example 4 shall be SOC20% -80%.

[Evaluation 3]
(Capacity maintenance rate at high rate)
Next, the all solid state batteries obtained in Example 2 and Comparative Example 3 were subjected to constant current charging at a battery evaluation environmental temperature of 25 ° C. with a current rate of 0.1 C and a voltage of 4.5 V, or up to 10 hours. Thereafter, an operation of discharging at a constant current up to a voltage of 2.5 V at a current rate of 0.1 C was performed. Next, a constant current charge was performed up to a voltage of 4.5 V at a current rate of 1.5 C or 40 minutes, and then a constant current discharge was performed up to a voltage of 2.5 V at a current rate of 1.5 C.
From the ratio of the discharge capacity at 1.5 C discharge to the discharge capacity at 0.1 C discharge, the capacity retention rate at charge / discharge at high rate was measured. The result is shown in FIG. Moreover, the improvement rate of Example 2 with respect to the comparative example 3 in the charge / discharge at the time of a high rate is shown in FIG.3 (b). As shown in FIG. 3A, it is suggested that the capacity retention rate of Example 2 is improved as compared with Comparative Example 3. Further, FIG. 3B suggests that the capacity of Example 2 is 120% or more when the capacity of Comparative Example 3 in charge / discharge at high rate is 100%. That is, by using the negative electrode layer of Example 2, all of the high-capacity Al mixed so as to have an SOC of 20% or less expands due to the first insertion of lithium ions in the initial charging stage, and the SOC is 20% or more. The above expanded state is also maintained at. Therefore, the contact between the graphite and the solid electrolyte material is improved, and the input / output and cycle characteristics are improved. Therefore, it is considered that the capacity retention rate can be higher than that of the graphite alone.

[Evaluation 4]
(Measurement of capacity maintenance rate under low external restraint)
In the all-solid-state batteries obtained in Example 2, Comparative Example 3, and Comparative Example 4, a current rate of 2 C and a voltage range of 3 were applied at a battery evaluation environmental temperature of 60 ° C. with an external binding force of 15 kgf / cm ^2. Charging / discharging was repeated until the number of times of charging / discharging became 10 times as 0.5V-4.5V.
The capacity retention rate after 10 charge / discharge cycles were measured. The result is shown in FIG.

  As shown in FIG. 4, Example 2 showed almost the same capacity retention rate as that of Comparative Example 3, and it was confirmed that the capacity maintenance rate was higher than that of Comparative Example 4. In Comparative Example 4 using the single Al negative electrode layer, the expansion and contraction of the volume of Al occurs due to repeated charge and discharge, so that electrode peeling occurs between the particles and from the current collector under low external restraint, and the capacity after the cycle Will decline. On the other hand, Example 2 is a mixture of Al and graphite, and even when repeated charge and discharge is performed, the expanded state of Al is always maintained in the SOC region, and is constrained by self-restraint force in the negative electrode layer. Become. Therefore, it is considered that the capacity retention rate after the cycle shows a value equivalent to that of graphite even under a low external constraint.

DESCRIPTION OF SYMBOLS 1 ... Positive electrode layer 2 ... Negative electrode layer 3 ... Solid electrolyte layer 4 ... Positive electrode collector 5 ... Negative electrode collector 6 ... Battery case 7 ... Carbon-type active material 8 ... Metal-type active material 9 ... Sulfide solid electrolyte material 10 ... All-solid-state battery 11 ... Negative electrode active material

Claims (2)

An all-solid battery having a positive electrode layer containing a positive electrode active material, a negative electrode layer containing a negative electrode active material, and a solid electrolyte layer formed between the positive electrode layer and the negative electrode layer,
The negative electrode layer contains a negative electrode active material obtained by mixing a carbon-based active material and a metal-based active material,
The metal-based active material undergoes an alloying reaction with Li, and is a metal represented by the general formula M or a metal oxide represented by the general formula M _x O _y (M is a metal),
The charge / discharge potential of the metal-based active material is more noble than the carbon-based active material,
The all-solid-state battery, wherein a capacity ratio of the carbon-based active material in the negative electrode layer is larger than that of the metal-based active material.   2. The all-solid-state battery according to claim 1, wherein a capacity ratio of the metal-based active material in the negative electrode layer is equal to or less than a minimum capacity ratio in a battery use region (SOC region).

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