JP2014146458A - All-solid-state battery and battery system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an all-solid-state battery capable of suppressing an increase in battery resistance due to heating charge, and the like.SOLUTION: An all-solid-state battery includes a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and a solid electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer. An active material of a rock salt layered structure containing Li, at least one of Ni, Co and Mn, O and further at least one of Al and Ga is used as the positive electrode active material. At least one of the positive electrode active material layer and the solid electrolyte layer contains an iodine-containing solid electrolyte material.

Description

  The present invention relates to an all-solid-state battery capable of suppressing an increase in battery resistance due to heating and charging, and a battery system using the same.

  With the rapid spread of information-related equipment and communication equipment such as personal computers, video cameras, and mobile phones in recent years, the development of batteries (eg, lithium batteries) that are excellent as power sources has been regarded as important. In fields other than information-related equipment and communication-related equipment, for example, in the automobile industry, development of lithium batteries and the like used for electric cars and hybrid cars is being promoted.

  Here, since commercially available lithium batteries use an organic electrolyte solution (liquid electrolyte) that uses a flammable organic solvent, it is possible to prevent the installation of safety devices and to prevent short circuits to suppress temperature rise during short circuits. Therefore, it is necessary to improve the structure and material. In contrast, an all-solid-state battery in which the liquid electrolyte is changed to a solid electrolyte does not use a flammable organic solvent in the battery, so the safety device can be simplified, and the manufacturing cost and productivity are considered excellent. Yes.

  In the all-solid-state battery, a solid electrolyte having a lower conductivity than the liquid electrolyte described above is used, so that there is a problem that it is difficult to cope with high-efficiency short-time charging. On the other hand, for example, Patent Document 1 discusses heating and charging in which charging is rapidly performed by heating an all-solid battery having a polymer solid electrolyte and increasing the conductivity of the polymer solid electrolyte. Yes.

Japanese Patent Laid-Open No. 4-10366 JP 2011-113792 A

By the way, in the field of a lithium battery, in order to make ion conductivity favorable, the fixed electrolyte material containing an iodine is used suitably for a positive electrode active material layer or a solid electrolyte layer.
However, when heating charging is applied to an all-solid battery having a positive electrode active material such as a lithium nickel manganese cobalt based composite compound and a solid electrolyte material containing iodine, there is a problem that the resistance of the battery increases. .

  The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide an all-solid-state battery capable of suppressing an increase in battery resistance due to heating and charging, and a battery system having the battery.

  In order to solve the above problems, in the present invention, a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and between the positive electrode active material layer and the negative electrode active material layer And having a solid electrolyte layer formed as a positive electrode active material, Li, at least one of Ni, Co, and Mn, O, and at least one of Al and Ga. There is provided an all solid state battery using an active material, wherein at least one of the positive electrode active material layer and the solid electrolyte layer contains a solid electrolyte material containing iodine.

  In the said invention, it is preferable that the active material of the said rock salt layered structure contains Al.

In the above invention, the active material of the rock salt bed granulation structure, general formula _{Li a Ni 1-x-y} -z-w Co x Mn y M 1 z M 2 w O 2 (0.92 ≦ a ≦ 1. 25, 0 ≦ x ≦ 1, 0 ≦ y ≦ 0.5, 0.001 ≦ z ≦ 0.04, 0 ≦ w ≦ 0.1, x + y + z + w ≦ 1, M ¹ is at least one of Al and Ga, M ² is preferably at least one element selected from the group consisting of Mg, Ti, Zr, W and Mo.).

  The present invention provides a battery system comprising the all solid state battery described above and a heating unit that heats the all solid state battery to 45 ° C. or higher during charging.

According to the present invention, by using an active material having a rock salt layered structure containing at least one of Al and Ga as a positive electrode active material, an all-solid battery that can suppress an increase in battery resistance due to heat charging is obtained. be able to.
Moreover, according to this invention, it can be set as the battery system which can suppress the increase in the resistance of the battery by heat charging by having the all-solid-state battery mentioned above.

It is a schematic sectional drawing which shows an example of the all-solid-state battery of this invention. It is a schematic sectional drawing which shows an example of the battery system of this invention. It is a graph which shows the relationship between content (mol%) of Al of the positive electrode active material of Example 1, Example 2, and a comparative example, and resistance increase rate (%). It is a figure which shows the iodine (I) density | concentration of the active material of the rock salt layered structure of Example 2 after a charge condition preservation | save, and a comparative example.

  Hereinafter, the all-solid-state battery and battery system of this invention are demonstrated.

A. All-solid battery The all-solid battery of the present invention is formed between a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and the positive electrode active material layer and the negative electrode active material layer. Active material having a layered structure of a rock salt layer and containing, as the positive electrode active material, at least one of Li, Ni, Co, and Mn, O, and at least one of Al and Ga And at least one of the positive electrode active material layer and the solid electrolyte layer contains a solid electrolyte material containing iodine.

FIG. 1 is a schematic cross-sectional view showing an example of the all solid state battery of the present invention.
As illustrated in FIG. 1, the all solid state battery 10 of the present invention includes a positive electrode active material layer 11 containing a positive electrode active material, a negative electrode active material layer 12 containing a negative electrode active material, a positive electrode active material layer 11 and a negative electrode. And a solid electrolyte layer 13 formed between the active material layers 12. In addition, the all solid state battery 10 of the present invention has a rock salt layered structure containing, as the positive electrode active material 1, at least one of Li, Ni, Co, and Mn, O, and at least one of Al and Ga. The positive electrode active material layer 11 is made of a substance and contains the solid electrolyte material 2 containing iodine. In addition, in FIG. 1, although the positive electrode active material layer 11 has shown about the example containing the solid electrolyte material 2 containing an iodine, it is not limited to this, Although not shown in figure, a solid electrolyte layer contains iodine. The solid electrolyte material to be contained may be contained, and both the positive electrode active material layer and the solid electrolyte layer may contain the solid electrolyte material containing iodine.

  According to the present invention, by using an active material having a rock salt layered structure containing at least one of Al and Ga as a positive electrode active material, an all-solid battery that can suppress an increase in battery resistance due to heat charging is obtained. be able to.

Here, when heating charging is applied to the above-described conventional all-solid-state battery, the reason why the resistance of the battery increases is estimated as follows.
That is, in the above-described all solid state battery, for example, a positive electrode active material such as a lithium nickel manganese cobalt based composite compound and a solid electrolyte material containing iodine are present in close proximity. Moreover, when the above-mentioned all solid state battery is placed in a high temperature environment, the dissociation and movement of iodide ions from the solid electrolyte material containing iodine are promoted. Further, at the time of charging, the positive electrode active material changes its ionic radius due to the change of the valences of Ni, Co, and Mn with the release of Li ions, and between the ions in the crystal structure. It is presumed that the distance will increase. Therefore, when the above-described conventional all-solid battery is heated and charged, it is assumed that iodide ions easily enter the crystal structure of the positive electrode active material in which the distance between each ion is widened. In addition, it is assumed that the resistance of the battery is increased because insertion / extraction of lithium ions becomes difficult at a portion where iodide ions are included in the crystal structure.

On the other hand, in the all solid state battery of the present invention, by using an active material having a rock salt layered structure containing at least one of Al and Ga as a positive electrode active material, the reason why the increase in battery resistance can be suppressed is as follows. It is estimated as follows.
That is, Al and Ga have a trivalence that is the average valence of Ni, Co, and Mn, and have an ionic radius close to that of Ni, Co, and Mn, and therefore are uniformly distributed in the crystal structure of the active material.
In addition, unlike Ni, Co, and Mn, Al and Ga do not undergo oxidation-reduction reactions during charge and discharge, and therefore the ionic radius does not change, so it is assumed that changes in the distance between ions can be suppressed.
As a result, it is presumed that an increase in battery resistance can be suppressed because it is possible to suppress the penetration of iodide ions into the positive electrode active material and not to inhibit the insertion / extraction of lithium ions. .
Hereinafter, details of the all solid state battery of the present invention will be described.

1. Positive electrode active material layer The positive electrode active material layer used in the present invention contains a positive electrode active material. In the positive electrode active material layer, at least a part of the positive electrode active material is present in the vicinity of the solid electrolyte material containing iodine. In the present invention, it is more preferable that at least a part of the positive electrode active material is in contact with a solid electrolyte material containing iodine.
Hereinafter, the details of the positive electrode active material layer used in the present invention will be described.

(1) Positive electrode active material (a) Active material having a rock salt layer structure The positive electrode active material in the present invention contains Li, at least one of Ni, Co, and Mn, and O, and further includes at least Al and Ga. An active material having a rock salt layered structure containing one (hereinafter may be simply referred to as an active material) is used.
Here, “the active material further contains at least one of Al and Ga” means that the rock salt layered structure of the active material contains at least one of Al and Ga. Further, it does not indicate a configuration in which the surface of the active material particles is covered with at least one of Al particles and Ga particles, or at least one of Al compound particles and Ga compound particles.

  The active material is not particularly limited as long as it contains Li, at least one of Ni, Co, and Mn, and O, and at least one of Al and Ga. However, at least one of Al and Ga has a crystal structure. It is preferable that it is incorporated in.

  Moreover, the active material is not particularly limited as long as it contains at least one of Al and Ga. Among them, Al is easy to produce an active material and easy to obtain raw materials. It is particularly preferable to contain

Moreover, as said active material, you may substitute by elements other than Al and Ga to about 10 mol% of a transition metal. The other elements are M ² elements in the general formula described later. The transition element will be described later.

Specifically, examples of the active material include those having a crystal phase represented by the following general formula 1.
Li _a Ni _1-xyzw Co _x Mn _y M ¹ _z M ² _w O ₂ (general formula 1)
(0.92 ≦ a ≦ 1.25, 0 ≦ x ≦ 1, 0 ≦ y ≦ 0.5, 0.001 ≦ z ≦ 0.04, 0 ≦ w ≦ 0.1, x + y + z + w ≦ 1, M ¹ is At least one of Al and Ga, M ² is at least one element selected from the group consisting of Mg, Ti, Zr, W and Mo.)

For example, a in the general formula 1 preferably satisfies 0.92 ≦ a ≦ 1.25, more preferably satisfies 0.95 ≦ a ≦ 1.20, and 0.98 ≦ a ≦ 1. .16 is particularly preferred.
For example, x in the general formula 1 preferably satisfies 0 ≦ x ≦ 1.
For example, y in the general formula 1 preferably satisfies 0 ≦ y ≦ 0.5.
For example, z in the general formula 1 preferably satisfies 0.001 ≦ z ≦ 0.04, more preferably satisfies 0.0025 ≦ z ≦ 0.03, and 0.004 ≦ z ≦ 0. 0.02 is particularly preferable.
As w in the general formula 1, it is preferable to satisfy 0 ≦ w ≦ 0.1. Further, the crystalline phase may have a M ^2, may not have the M ^2. When the crystal phase has M ² , w preferably satisfies 0.001 ≦ w ≦ 0.1, more preferably satisfies 0.0025 ≦ w ≦ 0.075, and 0.0035 ≦ w It is particularly preferable that ≦ 0.055 is satisfied.

Moreover, as said active material, what has the crystal phase shown by the following general formula 2 is mentioned.
_{Li b (Ni 1-α-} β Co α Mn β) (1-γ-δ) M 1 γ M 2 δ O 2 ( Formula 2)
(0.92 ≦ b ≦ 1.25, α: β = 1: 0.9 to 0.9: 1, 0.6 ≦, α + β ≦ 0.7, 0.001 ≦ γ ≦ 0. 04, 0 ≦ δ ≦ 0.1, γ + δ ≦ 1, M ¹ is at least one of Al and Ga, M ² is at least one element selected from the group consisting of Mg, Ti, Zr, W and Mo .)

For β, γ, and δ in the above general formula 2, it is preferable to take the same numerical ranges as, for example, a, z, and w in the above general formula 1, respectively.
The relation between α and β in the general formula 2 is, for example, in the range of α: β = 1: 0.9 to 0.9: 1, and 0.6 ≦, α + β ≦ 0.7. Is preferred. With such a relationship, the molar ratio of Ni, Co, and Mn can be made equivalent.

The content of at least one of Al and Ga contained in the active material is not particularly limited as long as it can form an active material having a rock salt layered structure, but the content of Al and Ga contained in the active material is not limited. It is preferably 0.1 mol% or more, particularly 0.2 mol% or more, particularly 0.4 mol% or more, preferably 6 mol% or less, especially 4 mol% or less, particularly 2. It is preferably 5 mol% or less.
If the content of at least one of Al and Ga is too small, it may be difficult to suppress an increase in battery resistance even when the active material contains at least one of Al and Ga. This is because if the content of at least one of Al and Ga is too large, it may be difficult to obtain the active material itself.
The transition element refers to Ni when the active material contains Ni, for example, Co when the active material contains Co, and when the active material contains Mn, for example. Mn, for example, when the active material contains Ni and Co, Ni and Co, for example, when the active material contains Ni and Mn, Ni and Mn, When the active material contains Ni, Co, and Mn, it means Ni, Co, and Mn.

  The shape of the active material of the present invention is not particularly limited, and may be, for example, particulate (powder) or thin film, but is preferably particulate. This is because peeling and cracking do not occur as in the case of a thin film, and the durability is excellent.

  The average particle diameter of the particulate active material is, for example, preferably 100 nm or more, especially 1 μm or more, particularly 2 μm or more. On the other hand, the average particle size is, for example, preferably 100 μm or less, more preferably 20 μm or less. The average particle diameter can be calculated with a laser diffraction particle size distribution meter.

The specific surface area of the active material is, for example, preferably 0.1 m ² / g or more, more preferably 0.3 m ² / g or more. On the other hand, the specific surface area is, for example, preferably 300 m ² / g or less, particularly preferably 100 m ² / g or less. The specific surface area can be calculated by the BET method (gas adsorption method).

It does not specifically limit as a formation method of the said active material, A well-known method can be used suitably. As an example, the following active material formation method may be mentioned, but the method is not limited thereto.
First, an acidic aqueous solution is prepared by dissolving at least one of a Ni source, a Co source, and a Mn source in an acid. Next, a hydroxide containing at least one of Ni, Co, and Mn is precipitated by adding an alkaline aqueous solution to the acidic aqueous solution. Next, an active material is formed by baking the said hydroxide with Li source. By using at least one of an Al source and a Ga source in at least one of the melting step and the firing step, an active material having a rock salt layer structure containing at least one of Al and Ga can be obtained.

(B) Coat layer The positive electrode active material used in the present invention is not particularly limited as long as the above-described active material having a rock salt layered structure is used.
In the present invention, a sulfide solid electrolyte material is included as a solid electrolyte material, and when the sulfide solid electrolyte material is used so as to be in contact with the positive electrode active material, the positive electrode active material is added to the active material described above. It is preferable to further have a coat layer made of an ion conductive oxide on the surface of the active material. This is because the formation of a high resistance layer generated at the contact interface between the sulfide solid electrolyte material and the active material described above can be suppressed.

  The coat layer in the present invention is formed on the surface of the active material and is composed of an ion conductive oxide.

The composition of the ion conductive oxide is not particularly limited. For example, an oxide containing an element of Group 1 or Group 2 and an element of Groups 3 to 6 and Groups 13 to 15 is included. Is preferred. Among these, a Li-containing oxide containing lithium as a Group 1 element is more preferable. In addition, the ion conductive oxides include B, Si, Ti, Zr, V, P, Al, Nb, Ta, Cr, Mo, Group 3 to Group 6, and Group 13 to Group 15 elements. And at least one element selected from W. Specifically, LiNbO ₃ , Li ₃ BO ₃ , LiBO ₂ , Li ₂ CO ₃ , LiAlO ₂ , Li ₄ SiO ₄ , Li ₂ SiO ₃ , Li ₃ PO ₄ , Li ₂ SO ₄ , Li ₂ TiO ₃ , Li Examples include ₄ Ti ₅ O ₁₂ , Li ₂ Ti ₂ O ₅ , Li ₂ ZrO ₃ , Li ₂ MoO _4, and Li ₂ WO _4. Among them, LiNbO ₃ is more preferable.

Further, the ion conductive oxide may be a Li-containing oxide composite compound. As such a composite compound, any combination of the above-described Li-containing oxides can be employed. For example, Li ₃ PO ₄ —Li ₄ SiO ₄ , Li ₃ BO ₃ —Li ₄ SiO ₄ , Li ₃ PO ₄ -Li ₄ GeO _4, and the like can be given. Other examples of the ion conductive oxide include Li ₂ O—B ₂ O ₃ —P ₂ O ₅ , Li ₂ O—SiO ₂ , Li ₂ O—B ₂ O ₃ , Li ₂ O—B _2. Crystalline oxidation of amorphous oxides such as O ₃ —ZnO, LiI—Al ₂ O ₃ , Li ₅ La ₃ Ta ₂ O ₁₂ , Li ₇ La ₃ Zr ₂ O ₁₂ , Li ₆ BAla ₂ Ta ₂ O ₁₂ And the like.

The ion conductivity (25 ° C.) of the ion conductive oxide is preferably, for example, 10 ⁻⁹ S / cm to 10 ⁻³ S / cm. Moreover, it is preferable that the electronic conductivity (25 degreeC) of an ion conductive oxide is 10 < ^-8 > S / cm-10 < ^-1 > S / cm, for example.

  The average thickness of the coating layer is not particularly limited as long as it is a thickness capable of suppressing the reaction between the active material and the sulfide solid electrolyte material when the active material is used in an all-solid battery. For example, it is preferably in the range of 1 nm to 500 nm, and more preferably in the range of 2 nm to 100 nm. This is because if the coat layer is too thick, the ionic conductivity and the electronic conductivity may be reduced. On the other hand, if the coat layer is too thin, the active material and the sulfide solid electrolyte material may react. Because there is. The average thickness of the coat layer can be measured, for example, by observation with a transmission electron microscope (TEM).

  The form of the coating layer is not particularly limited as long as it is formed on the surface of the active material, but for example, it is preferable to coat the surface of the active material. The coverage of the coat layer on the surface of the active material is preferably high for the purpose of suppressing an increase in interfacial resistance. Specifically, it is preferably 50% or more, more preferably 80% or more. . The coat layer may cover the entire surface of the active material. The coverage of the coating layer can be measured using, for example, a transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), or the like.

The method for forming the coating layer used in the present invention is not particularly limited, and a known method can be appropriately selected and used. As an example, the following coating layer forming method may be mentioned, but the method is not limited thereto.
First, a precursor layer is formed on the surface of the active material using a coating layer forming solution containing a coating layer forming raw material and a solvent. Next, the precursor layer is subjected to a heat treatment to form a coat layer made of an ion conductive oxide.

(2) Positive electrode active material layer The positive electrode active material layer used for this invention contains the positive electrode active material mentioned above.
As content of the positive electrode active material contained in the said positive electrode active material layer, it is preferable to exist in the range of 10 weight%-99 weight%, for example, and it is in the range of 20 weight%-90 weight%. More preferred.

In the present invention, it is preferable that the positive electrode active material layer contains a solid electrolyte material. This is because the ion conductivity of the positive electrode active material layer can be improved. In the present invention, among solid electrolyte materials, a solid electrolyte material containing iodine is preferable. By containing the solid electrolyte material containing iodine in the positive electrode active material layer, it is possible to more effectively suppress an increase in battery resistance due to heat charging.
In the present invention, the solid electrolyte material containing iodine is more preferably a sulfide solid electrolyte material.

As the solid electrolyte material containing iodine, for _{example, LiI, Li 2 S-P} 2 S 5 -LiI, Li 2 S-P 2 S 5 -Li 2 O-LiI, Li 2 S-SiS 2 -LiI, Li _{2 S-SiS 2 -B 2 S} 3 -LiI, mention may be made of _{Li 2 S-SiS 2 -P 2} S 5 -LiI like. 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.

When the sulfide solid electrolyte material is formed using a raw material composition containing LiI, the proportion of LiI is preferably in the range of, for example, 1 mol% to 60 mol%, for example, 5 mol% to 50 mol%. More preferably, it is in the range, more preferably in the 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%.

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.

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. Further, the Li 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.

Examples of the shape of the sulfide solid electrolyte material in the present invention include a particle shape such as a true sphere and an oval sphere, and a thin film shape. When the sulfide solid electrolyte material has the above particle shape, the average particle diameter (D ₅₀ ) is not particularly limited, but is preferably 40 μm or less, more preferably 20 μm or less, and more preferably 10 μm. More preferably, it is as follows. This is because it is easy to improve the filling rate in the positive electrode active material layer. On the other hand, the average particle diameter is preferably 0.01 μm or more, and more preferably 0.1 μm or more. In addition, the said average particle diameter can be determined with a particle size distribution meter, for example.

In the present invention, the positive electrode active material layer may contain a solid electrolyte material other than the solid electrolyte material containing iodine. In this case, a sulfide solid electrolyte material that does not contain iodine can be suitably used as the solid electrolyte material.
Examples of the sulfide solid electrolyte material containing no iodine include Li ₂ S—P ₂ S ₅ , Li ₂ S—P ₂ S ₅ —Li ₂ O, Li ₂ S—SiS ₂ , Li ₂ S—SiS ₂ —. _{LiBr, Li 2 S-SiS 2} -LiCl, Li 2 S-B 2 S 3, Li 2 S-P 2 S 5 -Z m S n ( however, m, n is the number of positive .Z is, Ge, Zn , one of _{Ga.), Li 2 S-} GeS 2, Li 2 S-SiS 2 -Li 3 PO 4, Li 2 S-SiS 2 -Li x MO y ( provided that, x, y number positive .M Can be any of P, Si, Ge, B, Al, Ga, and In.

  In the case where the sulfide solid electrolyte material not containing iodine is a raw material composition containing LiX (X = Cl, Br), the proportion of LiX is the same as the above-described proportion of LiI. Therefore, the description here is omitted. Moreover, since it is the same as that of the sulfide solid electrolyte material containing iodine about the point other than the above about the sulfide solid electrolyte material which does not contain iodine, description here is abbreviate | omitted.

  The positive electrode active material layer in the present invention may further contain at least one of a conductive material and a binder in addition to the positive electrode active material and the solid electrolyte material described above. Examples of the conductive material include acetylene black, ketjen black, and carbon fiber. Examples of the binder include fluorine-containing binders such as PTFE and PVDF. The thickness of the positive electrode active material layer varies depending on the intended configuration of the all-solid battery, but is preferably in the range of 0.1 μm to 1000 μm, for example.

2. Negative electrode active material layer The negative electrode active material layer in the present invention is a layer containing at least a negative electrode active material, and may contain at least one of a solid electrolyte material, a conductive material and a binder, if necessary. good.
Examples of the negative electrode active material include a metal active material and a carbon active material. Examples of the metal active material include In, Al, Si, and Sn. On the other hand, examples of the carbon active material include mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon. Note that the conductive material and the binder used in the negative electrode active material layer are the same as those in the positive electrode active material layer described above. Moreover, it is preferable that the thickness of a negative electrode active material layer exists in the range of 0.1 micrometer-1000 micrometers, for example.

3. Next, the solid electrolyte layer in the present invention will be described. The solid electrolyte layer in the present invention is a layer formed between the positive electrode active material layer and the negative electrode active material layer, and is a layer containing at least a solid electrolyte material. As described above, when the positive electrode active material layer contains a solid electrolyte material containing iodine, the solid electrolyte material contained in the solid electrolyte layer is not particularly limited as long as it has ion conductivity, A solid electrolyte material containing iodine may be used, and other solid electrolyte materials may be used. When it is other than the solid electrolyte material containing iodine, the sulfide solid electrolyte material not containing iodine is preferable. On the other hand, when the positive electrode active material layer does not contain a solid electrolyte material containing iodine, the solid electrolyte layer contains a solid electrolyte material containing iodine. In particular, in the present invention, it is preferable that both the positive electrode active material layer and the solid electrolyte layer contain a solid electrolyte material containing iodine. This is because the effects of the present invention can be sufficiently exhibited. The solid electrolyte material containing iodine used for the solid electrolyte layer is more preferably a sulfide solid electrolyte material.

  The solid electrolyte material containing iodine and the sulfide solid electrolyte material not containing iodine are the same as the contents described in the above section “1. Positive electrode active material layer”, and thus the description thereof is omitted here. . Moreover, about solid electrolyte materials other than the solid electrolyte material containing iodine and the sulfide solid electrolyte material not containing iodine, the same material as the solid electrolyte material used in a general all-solid battery can be used.

  The content of the solid electrolyte material in the solid electrolyte layer is, for example, preferably in the range of 10% by weight to 100% by weight, and more preferably in the range of 50% by weight to 100% by weight. The solid electrolyte layer may contain a fluorine-containing binder such as PTFE or PVDF. The thickness of the solid electrolyte layer is preferably in the range of 0.1 μm to 1000 μm, for example, and more preferably in the range of 0.1 μm to 300 μm.

4). Other Configurations The all solid state battery of the present invention has at least the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer described above. Furthermore, it usually has a positive electrode current collector for collecting current of the positive electrode active material layer and a negative electrode current collector for collecting current of the negative electrode active material layer. 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. Moreover, the battery case used for a general all-solid-state battery can be used for the battery case used for this invention, For example, the battery case made from SUS etc. can be mentioned. Further, the all solid state battery of the present invention may be one in which the power generating element is formed inside the insulating ring.

5. All-solid-state battery In this invention, the increase in the resistance of the battery by heating charge can be suppressed by using the active material of the rock salt layered structure containing at least one of Al and Ga mentioned above as a positive electrode active material. Although it does not specifically limit about the heating temperature in the said heating charge, It is preferable that it is 45 degreeC or more, especially 60 degreeC or more.
LiPF ₆ generally used in liquid batteries is said to thermally decompose at about 60 ° C. The all solid state battery of the present invention can be heated and charged at a heating temperature that cannot be applied to a liquid battery.
The upper limit of the heating temperature is not particularly limited, but is about 100 ° C. from the viewpoint of safety.

  The all-solid-state battery of the present invention is a secondary battery, and can be repeatedly charged and discharged, so that it is useful, for example, as an in-vehicle battery. Examples of the shape of the all solid state battery of the present invention 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. it can. As an example of an all-solid-state battery manufacturing method, a power generation element is manufactured by sequentially pressing the material forming the positive electrode active material layer, the material forming the solid electrolyte layer, and the material forming the negative electrode active material layer. In addition, a method of storing the power generation element inside the battery case and caulking the battery case can be exemplified.

B. Battery System The battery system of the present invention includes the all solid state battery described above and a heating unit that heats the all solid state battery to 45 ° C. or higher during charging.

  FIG. 2 is a schematic sectional view showing an example of the battery system of the present invention. As illustrated in FIG. 2, the battery system 100 of the present invention includes an all solid state battery 10 and a heating unit 20 that heats the all solid state battery 10 to 45 ° C. or more during charging. .

According to this invention, it can be set as the battery system which can suppress the increase in the resistance of the battery by heat charging by having the all-solid-state battery mentioned above.
Hereinafter, the battery system of the present invention will be described.

1. All-solid-state battery The all-solid-state battery used in the present invention is the same as the content described in the above-mentioned section “A. All-solid-state battery”, and thus the description thereof is omitted here.

2. Heating part The heating part used for this invention heats the said all-solid-state battery to 45 degreeC or more at the time of charge.

  The heating unit is not particularly limited as long as it heats the all-solid-state battery to 45 ° C. or higher. In particular, the heating unit is preferably heated to 60 ° C. or higher. In addition, the upper limit of the heating temperature by the heating unit can be the same as the heating temperature at the time of charging of the all-solid battery described in the section “A. All-solid-state battery” described above. Omitted.

  The configuration of the heating unit is not particularly limited as long as the all solid state battery can be heated to 45 ° C. or more during charging. For example, the heating unit may be one that heats the all solid state battery simultaneously with the start of charging of the all solid state battery. it can.

  The heating unit may have a structure in which the heating unit and the all solid state battery are in direct contact with each other to transmit heat, and the heating unit and the all solid state battery are not in direct contact with each other, for example, like a thermostatic bath, A structure for transferring heat via gas, liquid, or the like may be used.

3. Other Configurations The battery system used in the present invention is not particularly limited as long as it has the above-described all solid state battery and a heating unit.

  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.

[Example 1]
(Production of active material)
According to the following procedure, Li _1.14 Ni _0.331 Co _0.331 Mn _0.331 Al _0.008 O ₂ (Li _1.14 (Ni _1/3 Co _1/3 Mn _1/3 ) _0.992 Al An active material having a rock salt layer structure having a crystal phase represented by _0.008 O ₂ ) was synthesized.
First, a Ni source, a Co source, a Mn source, and an Al source were dissolved in sulfuric acid or the like to prepare a sulfate aqueous solution. Next, a bath with adjusted pH was prepared as a reaction field, and the sulfate aqueous solution and the alkaline aqueous solution were added dropwise to precipitate a hydroxide containing Ni, Co, Mn and Al. Next, a hydroxide containing Ni, Co, Mn and Al is taken out from the bath, and the hydroxide is fired together with a Li source such as Li ₂ CO ₃ at a predetermined temperature for a predetermined time, whereby the active material described above is obtained. Could get.

(Preparation of coat layer)
Next, a coating layer composed of LiNbO ₃ was formed on the surface of the above active material by the following procedure.
A composition for a coat layer prepared by dissolving equimolar LiOC ₂ H ₅ and Nb (OC ₂ H ₅ ) ₅ in an ethanol solvent is applied to the surface of the above active material by a rolling fluid coating apparatus (SFP- 01, manufactured by POWREC Co., Ltd.). Thereafter, the coated active material was heat-treated at 350 ° C. under atmospheric pressure for 1 hour to form a coat layer composed of LiNbO _{3 on} the surface of the active material.
The positive electrode active material was obtained by performing the above procedure.

(Production of solid electrolyte)
By the following procedure created a _Li 2 _S-P 2 _{S 5} based glass ceramics (solid electrolyte) containing LiI.
As starting materials, lithium sulfide (Li ₂ S), diphosphorus pentasulfide (P ₂ S ₅ ) and lithium iodide (LiI) 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. Next, LiI was weighed so that LiI was 30 mol%. 2 g of this mixture is charged into a planetary ball mill container (45 cc, made of ZrO ₂ ), dehydrated heptane (moisture content of 30 ppm or less, 4 g) is charged, and ZrO ₂ balls (φ = 5 mm, 53 g) are charged. 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 40 times with a base plate rotation speed of 500 rpm and a one-hour treatment and a 15-minute pause. Thereafter, the obtained sample was dried on a hot plate so as to remove heptane to obtain a sulfide solid electrolyte material which is glass. Thereafter, the sulfide solid electrolyte material that is glass was heat-treated in an Ar atmosphere at 180 ° C. (temperature equal to or higher than the crystallization temperature) for 1 hour to obtain a sulfide solid electrolyte material that was glass ceramic. The composition of the obtained sulfide solid electrolyte material was 30LiI · 70 (0.75Li ₂ S · 0.25P ₂ S ₅ ).
The sulfide solid electrolyte material has an ionic conductivity at 45 ° C. of about twice as high as that at room temperature (25 ° C.) and an ionic conductivity at 60 ° C. of about 3 times. It has the characteristic that becomes.

(Preparation of positive electrode mixture)
400 mg of the above positive electrode active material, 12 mg of VGCF (Showa Denko), 134 mg of the above solid electrolyte, and 1 g of dehydrated heptane (Kanto Chemical) were weighed and mixed thoroughly.
The above-mentioned mixed material was heated at 100 ° C. to volatilize heptane to obtain a positive electrode mixture.

(Preparation of negative electrode composite)
A negative electrode mixture was prepared by weighing and mixing 900 mg of graphite (Mitsubishi Chemical) and 964 mg of the above-mentioned solid electrolyte.

(Preparation of battery characteristics measurement cell)
65 mg of the above-mentioned solid electrolyte was weighed into a 1 cm ² mold and pressed at 100 MPa to produce a solid electrolyte layer. 20.5 mg of the positive electrode mixture was placed on one side, and pressed at 100 MPa to produce a positive electrode.
A negative electrode was prepared by putting 21 mg of the negative electrode mixture on the opposite side and pressing at 400 MPa.
A battery characteristic measurement cell was obtained by the above procedure.

[Example 2]
In the same manner as in Example 1, Li _1.14 Ni _0.328 Co _0.328 Mn _0.328 Al _0.017 O ₂ (Li _1.14 (Ni _1/3 Co _1/3 Mn _1/3 ) An active material having a rock salt layered structure having a crystal phase represented by _0.983 Al _0.017 O ₂ ) was synthesized. Except for the above, a positive electrode active material was produced in the same manner as in Example 1, and a cell for measuring battery characteristics was produced.

[Comparative example]
Li _1.14 Ni _0.333 Co _0.333 Mn _0.333 O ₂ (Li _1.14 Ni _1/3 Co _1/3 Mn _1/3 O ₂ ) to which Al is not added as an active material A positive electrode active material was prepared in the same manner as in Example 1 except that an active material having a rock salt layered structure having a crystal phase was used, and a battery characteristic measurement cell was prepared.

[Evaluation]
<Measurement of battery characteristics>
(conditioning)
The following cell characteristics measurement cell was conditioned at 25 ° C.
The battery characteristics measurement cells of Example 1, Example 2 and Comparative Example were charged with constant current-constant voltage at 0.27 mA (upper limit 4.3 V, cut current 0.027 mA), and after resting for 15 minutes, 0.27 mA. Was subjected to constant current-constant voltage discharge (lower limit: 3.0 V, cut current: 0.027 mA), and then rested for 15 minutes to condition the cell for measuring battery characteristics.

(Resistivity increase rate of battery DC resistance by storage of charge state)
First, the battery direct current resistance measurement was performed at 25 degreeC about the battery characteristic measurement cell before charge condition preservation | save.
About the battery characteristic measurement cell of Example 1, Example 2, and the comparative example, constant current-constant voltage charge was performed at 0.27 mA. As charging conditions, the upper limit of the voltage was 3.6 V and the cut current was 0.027 mA. After resting for 1 minute after charging, constant current discharge was performed at 8.1 mA for 5 seconds. The battery DC resistance (R = ΔV / I) was calculated from the voltage difference (ΔV) before and after the discharge and the current value (I) that was passed.

Next, the state of charge of the following battery characteristic measurement cell was stored at 60 ° C.
The cell for measuring battery characteristics of Example 1, Example 2 and Comparative Example was charged with constant current-constant voltage (upper limit 4.3 V) at 0.27 mA for 200 hours. Next, after resting for 15 minutes, constant current discharge (lower limit: 3.0 V) was performed at 0.27 mA.

  Then, the battery characteristic measurement cell after completion | finish of charge condition preservation | save was moved to the 25 degreeC thermostat, and battery direct current resistance measurement was performed in the same procedure as the above-mentioned charge state preservation | save.

  The rate of increase in resistance was obtained from the value of the DC resistance of the battery before and after storing the state of charge. The results are shown in Table 1 and FIG. FIG. 3 is a graph showing the relationship between the Al content (mol%) of the positive electrode active materials of Example 1, Example 2, and Comparative Example, and the resistance increase rate (%).

(Cross-sectional TEM-EDX analysis after storage of charge state)
About the active material of the rock salt layered structure of Example 2 and a comparative example, the cross-sectional TEM-EDX analysis after charge condition preservation | save was performed.
FIB processing and TEM-EDX analysis were all performed under an inert atmosphere. The results are shown in FIG. FIG. 4 is a diagram showing the I concentration (atomic%) of the active material of the rock salt layered structure of Example 2 and Comparative Example after storage of the charged state.

Compared with Example 2, the comparative example had a higher I concentration near the surface of the active material having a rock salt layered structure.
Thus, the addition of Al could suppress the entry of iodide ions.

DESCRIPTION OF SYMBOLS 1 ... Positive electrode active material 2 ... Solid electrolyte material which has iodine 10 ... All-solid-state battery 11 ... Positive electrode active material layer 12 ... Negative electrode active material layer 13 ... Solid electrolyte layer 20 ... Heating part 100 ... Battery system

Claims (4)

A positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and a solid electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer,
As the positive electrode active material, a rock salt layered active material containing at least one of Li, Ni, Co, and Mn, O, and at least one of Al and Ga is used.
An all-solid battery, wherein at least one of the positive electrode active material layer and the solid electrolyte layer contains a solid electrolyte material containing iodine.   The all-solid-state battery according to claim 1, wherein the active material having a rock salt layered structure contains Al. Active material of the rock salt layer forming structure, the general formula _{Li a Ni 1-x-y} -z-w Co x Mn y M 1 z M 2 w O 2 (0.92 ≦ a ≦ 1.25,0 ≦ x ≦ 1,0 ≦ y ≦ 0.5,0.001 ≦ z ≦ 0.04,0 ≦ w ≦ 0.1, x + y + z + w ≦ 1, M 1 is at least one of Al and Ga, ^{M 2} is Mg, Ti 3. The all-solid-state battery according to claim 1, wherein the all-solid-state battery has a crystal phase represented by: at least one element selected from the group consisting of Zr, W, and Mo. An all solid state battery according to any one of claims 1 to 3,
A heating unit for heating the all solid state battery to 45 ° C. or more during charging;
A battery system comprising:

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