JP6652705B2 - Solid electrolyte and all solid state battery - Google Patents

Description

  The present invention relates to a solid electrolyte and an all-solid battery.

  Energy storage technology that stores electricity generated from minute energy such as solar energy, vibration energy, and human and animal body temperature, and uses it for sensors, wireless transmission power, etc., is safe and reliable under all global environments. A secondary battery is required.

  At present, in a liquid battery using an organic solvent solution that is widely used, there is a concern that the positive electrode active material is degraded with repeated cycles, and the battery capacity is reduced. Further, in the above-mentioned liquid battery, there is a concern that the organic electrolyte in the battery may catch fire due to short-circuit due to the formation of dendrites and fire.

  Therefore, in recent years, all-solid-state batteries in which all constituent materials are solid have been attracting attention. The all-solid-state battery is advantageous in that it has excellent cycle characteristics without fear of liquid leakage or ignition and has a high degree of freedom in shape.

As a solid electrolyte used for an all-solid lithium secondary battery, that is, a lithium ion conductor, for example, the following are known (for example, see Patent Documents 1 to 3 and Non-Patent Documents 1 to 5). As oxides, there are known a LiSICON type based on Li ₃ PO ₄ and Li ₄ GeO ₄ , a NASICON type based on a sodium ion conductor, a LiLaZrO garnet type, and a perovskite type such as LLTO. Li ₁₀ GeP ₂ S ₁₁ and Li ₇ P ₃ S ₁₁ are known as sulfides.
However, these solid electrolytes have a problem that they are unstable in the atmosphere or use rare and expensive Ge.

JP 2007-528108A JP 2010-272344 A JP-A-8-198638

H. Y-P. Hong. , Materials Research Bulletin, Volume 13, Issue 2, February 1978, Pages 117-124. R. Murugan, V .; Thangadurai, W.C. Weppner. Angew. Chem. Int. Ed. , (2007), 46; 7778-7781 Y. Inaguma, C.I. Liquan, M .; Itoh, T.W. Nakamura, T .; Uchida, H .; Ikuta, M .; Wakihara. , Solid State Communications Volume 86, Issue 10, June 1993, Pages 689-693. N. Kayama, K .; Homma, Y .; Yamakawa, M .; Hirayama, R .; Kanno, M .; Yonemura, T .; Kamiyama, Y .; Kato, S.M. Hama, K .; Kawamoto & A. Mitsui. , Nature Materials 10,682-686 (2011). A. Hayashi, S .; Hama, T .; Minami, M .; Tatumsumago. , Electrochem. Commun. , 5 (2003), p. 111

  An object of the present invention is to provide an inexpensive solid electrolyte that is stable even in the atmosphere, and an all-solid-state battery using the solid electrolyte.

In one embodiment, the solid electrolyte comprises:
Having Li, Al, P, H, and O as constituent elements,
It has a P ₃ O ₁₀ structure and an AlO ₆ structure that is a hexacoordinate octahedral structure.

In one aspect, the all-solid-state battery is
A positive electrode active material-containing layer, a negative electrode active material-containing layer, and a solid electrolyte layer interposed between the positive electrode active material-containing layer and the negative electrode active material-containing layer,
The solid electrolyte layer is a layer composed of the disclosed solid electrolyte.

In one aspect, an inexpensive solid electrolyte that is stable in the atmosphere can be obtained.
In one aspect, an all-solid-state battery that is stable even in the atmosphere and uses an inexpensive solid electrolyte can be obtained.

FIG. 1 is a schematic cross-sectional view of an example of the disclosed all solid state battery. FIG. 2 is an X-ray diffraction spectrum of AlH ₂ P ₃ O ₁₀ obtained in Example 1. FIG. 3 is an X-ray diffraction spectrum of the solid electrolyte obtained in Example 1.

(Solid electrolyte)
The disclosed solid electrolyte has Li (lithium), Al (aluminum), P (phosphorus), H (hydrogen), and O (oxygen) as constituent elements.
The solid electrolyte has a P ₃ O ₁₀ structure and an AlO ₆ structure that is a hexacoordinate octahedral structure.

Conventionally known sulfide-based solid electrolytes are unstable in the atmosphere. Further, many solid electrolytes require rare and expensive elements such as Ge in order to obtain lithium ion conductivity, which is a necessary performance of the solid electrolyte.
Since the disclosed solid electrolyte does not require S (sulfur) as a constituent element, it is stable even in the atmosphere. In addition, the disclosed solid electrolyte has Li, Al, P, H, and O as constituent elements, but does not require a rare element such as Ge as a constituent element. Therefore, a rare element such as Ge is used as a constituent element. Less expensive than the required solid electrolyte.

The P ₃ O ₁₀ structure is composed of three tetrahedral PO ₄ bonded by sharing an oxygen atom. One tetrahedral PO ₄ has one P (phosphorus) at the center and four Os (oxygen) at the top. In the P ₃ O ₁₀ structure, the outer tetrahedron shares one vertex with the central tetrahedron, and the central tetrahedron shares two vertices with the outer tetrahedron.

The solid electrolyte is represented, for example, by the following composition formula (1).
_{Li x AlH 2.0-x P 3} O 10 ··· composition formula (1)
However, in the composition formula (1), x satisfies 0 <x ≦ 2.0.

<Method for producing solid electrolyte>
The method for producing the solid electrolyte is not particularly limited and may be appropriately selected depending on the intended purpose. A method in which at least a part of H (hydrogen) of AlH ₂ P ₃ O ₁₀ is replaced by Li (lithium). (Hereinafter may be referred to as “ion exchange method”) is preferable in that the production is easy.

AlH ₂ P ₃ O ₁₀ has a P ₃ O ₁₀ structure and an AlO ₆ structure which is a hexacoordinate octahedral structure. Therefore, by substituting at least part of H (hydrogen) with Li (lithium) in AlH ₂ P ₃ O ₁₀ , the disclosed solid electrolyte can be easily obtained.

The method for producing AlH ₂ P ₃ O ₁₀ is described, for example, in the literature [d'Yvoire, F. Bull. Soc. Chim. Fr. 1224 (1962)].

The Li source used in the ion exchange method is not particularly limited as long as it is a Li-containing compound, and can be appropriately selected depending on the purpose. Examples thereof include LiClO ₄ , LiCO ₃ , LiNO ₃ , and LiBF _4. Can be

In the ion exchange method, the solid electrolyte can be obtained by mixing and firing AlH ₂ P ₃ O ₁₀ and a Li-containing compound.
The ratio of AlH ₂ P ₃ O ₁₀ and the Li-containing compound at the time of mixing is not particularly limited, and can be appropriately selected depending on the purpose.
The firing is preferably performed in an inert atmosphere, and more preferably in an Ar atmosphere.
The firing temperature and time are not particularly limited, and can be appropriately selected depending on the purpose.

(All solid state battery)
The disclosed all solid state battery has at least a positive electrode active material-containing layer, a negative electrode active material-containing layer, and a solid electrolyte layer interposed between the positive electrode active material-containing layer and the negative electrode active material-containing layer. It has other members according to.

<Positive electrode active material containing layer>
The positive electrode active material-containing layer is not particularly limited as long as it is a layer containing a positive electrode active material, and can be appropriately selected depending on the purpose.

The positive electrode active material-containing layer may be the positive electrode active material itself or a mixture of the positive electrode active material and the solid electrolyte.
When the positive electrode active material-containing layer is a layer made of a mixture of the positive electrode active material and the solid electrolyte, in the positive electrode active material-containing layer, the ratio of the positive electrode active material and the solid electrolyte is as follows: There is no particular limitation, and it can be appropriately selected according to the purpose. However, the mass ratio (positive electrode active material: solid electrolyte) is preferably 1.0: 0.1 to 1.0: 2.0, and 1.0: 0.1 to 1.0: 2.0. : 0.3 to 1.0: 1.5 is more preferable, and 1.0: 0.5 to 1.0: 1.0 is particularly preferable.

The positive electrode active material is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include a lithium-containing composite oxide. The lithium-containing composite oxide is not particularly limited as long as it is a composite oxide containing lithium and another metal, and can be appropriately selected depending on the purpose. For example, LiCoO ₂ , LiNiO ₂ , LiCrO _{2 2} , LiVO ₂ , LiM _x Mn ₂ -xO ₄ (M is at least one of Co, Ni, Fe, Cr and Cu; 0 ≦ x <2), LiFePO ₄ , LiCoPO ₄ , LiNiPO ₄ , LiNi _1/3 Mn _1/3 Co _1/3 O _{2 and the} like.

  The average thickness of the positive electrode active material-containing layer is not particularly limited, but may be appropriately selected, for example, from a range of about 0.1 mm to 1.0 mm according to a target battery capacity and a battery shape. Can be.

<Solid electrolyte layer>
The solid electrolyte layer comprises the disclosed solid electrolyte.

  The average thickness of the solid electrolyte layer is not particularly limited and may be appropriately selected depending on the intended purpose without a short circuit between the positive electrode and the negative electrode, and is preferably 0.05 mm to 3.0 mm, more preferably 0.1 mm to 3.0 mm. 2.0 mm is more preferable, and 0.5 mm to 1.5 mm is particularly preferable.

<Negative electrode active material containing layer>
The negative electrode active material-containing layer is not particularly limited as long as it is a layer containing a negative electrode active material, and can be appropriately selected depending on the purpose.

The negative electrode active material-containing layer may be the negative electrode active material itself or a mixture of the negative electrode active material and the solid electrolyte.
When the negative electrode active material-containing layer is a layer made of a mixture of the negative electrode active material and the solid electrolyte, in the negative electrode active material-containing layer, the ratio of the negative electrode active material and the solid electrolyte is as follows: There is no particular limitation, and it can be appropriately selected according to the purpose. However, the mass ratio (negative electrode active material: solid electrolyte) is preferably 1.0: 0.1 to 1.0: 2.0, and 1.0: 0.1 to 1.0: 2.0. : 0.3 to 1.0: 1.5 is more preferable, and 1.0: 0.5 to 1.0: 1.0 is particularly preferable.

The negative electrode active material is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include lithium, a lithium alloy, Li ₄ Ti ₅ O ₁₂ , LiVO ₃ , amorphous carbon, natural graphite, and artificial graphite. , TiS ₂ , TiO ₂ , CoO _{2 and the} like.

  The average thickness of the negative electrode active material-containing layer is not particularly limited and may be appropriately selected depending on the intended purpose. However, the average thickness is preferably from 0.05 mm to 3.0 mm, more preferably from 0.1 mm to 2.0 mm, 0.5 mm to 1.5 mm is particularly preferred.

<Other components>
The other members are not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include a positive electrode current collector, a negative electrode current collector, and a battery case.

<< Positive electrode current collector >>
The size and structure of the positive electrode current collector are not particularly limited, and can be appropriately selected depending on the purpose.
Examples of the material of the positive electrode current collector include die steel, stainless steel, aluminum, aluminum alloy, titanium alloy, copper, and nickel.
Examples of the shape of the positive electrode current collector include a foil shape, a plate shape, and a mesh shape.

<< Negative electrode current collector >>
The size and structure of the negative electrode current collector are not particularly limited, and can be appropriately selected depending on the purpose.
Examples of the material of the negative electrode current collector include die steel, gold, indium, nickel, copper, and stainless steel.
Examples of the shape of the negative electrode current collector include a foil shape, a plate shape, and a mesh shape.

<< Battery case >>
The battery case is not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include a known laminated film that can be used in a conventional all-solid-state battery. Examples of the laminate film include a resin laminate film and a film obtained by depositing a metal on a resin laminate film.

  The shape of the all-solid-state battery is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include a cylindrical shape, a square shape, a button shape, a coin shape, and a flat shape.

  The all-solid-state battery is a so-called thin-film all-solid-state battery in which the positive electrode active material-containing layer, the solid electrolyte layer, and the negative electrode active material-containing layer are stacked using a gas phase method, and has a cycle life of It is preferable because it is excellent.

  FIG. 1 is a schematic cross-sectional view of an example of the disclosed all-solid-state battery. In the all-solid-state battery of FIG. 1, a positive electrode active material-containing layer 2, a solid electrolyte layer 3, a negative electrode active material-containing layer 4, and a negative electrode current collector 5 are stacked on a positive electrode current collector 1 in this order. .

  The operation principle of the all-solid-state battery will be described by taking a lithium ion all-solid-state secondary battery as an example. At the time of charging, Li is ionized, escapes from the positive electrode active material containing layer, moves in the solid electrolyte toward the negative electrode active material containing layer, and is inserted into the negative electrode active material containing layer. On the other hand, at the time of discharge, the Li ions inserted into the negative electrode active material containing layer move to the positive electrode active material containing layer side in the solid electrolyte and return to the positive electrode active material containing layer. As described above, in the lithium ion battery, charging and discharging are performed by moving Li ions between the positive electrode and the negative electrode.

<Manufacturing method of all solid state battery>
The method for producing the all-solid-state battery is not particularly limited and can be appropriately selected depending on the intended purpose.For example, a powder of a material constituting the positive electrode active material-containing layer, a powdery solid electrolyte, A method of laminating a powder of a material constituting the negative electrode active material in a layered form and press-molding the layered layer may be used.
When the solid electrolyte is used, it is not necessary to heat to a high temperature during the pressure molding, and an all-solid battery having excellent battery performance at a low temperature can be manufactured.
The pressure in the pressure molding includes, for example, 127 kgf / cm ^{2 to} 1,270 kgf / cm ² .
The temperature in the pressure molding includes, for example, room temperature.

  Hereinafter, examples of the present invention will be described, but the present invention is not limited to the following examples.

(Example 1)
<Synthesis of solid electrolyte (lithium ion conductor)>
<< Synthesis of Precursor (AlH ₂ P ₃ O ₁₀ ) >>
First, phosphoric acid (H ₃ PO ₄ ) and aluminum hydroxide [Al (OH) ₃ ] are mixed in a beaker made of Teflon (registered trademark) in a mass ratio of [H ₃ PO ₄ : Al (OH) ₃ ] = Mix at 12: 1. The obtained mixture was subjected to a heat treatment at 220 ° C. for 12 hours in an electric furnace. The obtained gel was washed with distilled water, filtered, and dried in a vacuum dryer at 200 ° C. for 12 hours to obtain AlH ₂ P ₃ O ₁₀ .
An X-ray diffraction spectrum of the obtained AlH ₂ P ₃ O ₁₀ is shown in FIG. In FIG. 2 and FIG. 3, the middle spectrum data is powder data of AlH ₂ P ₃ O ₁₀ (PDF: 00-036-0320).

<< Ion exchange >>
As a lithium (Li) ion source to be replaced, LiClO ₄ was mixed with the obtained precursor at a molar ratio (LiClO ₄ : precursor) = 4: 1. The obtained mixture was baked at 260 ° C. for 12 hours in an Ar atmosphere. The obtained solid was pulverized in a dry room adjusted to a dew point of -46 ° C, washed with dehydrated ethanol, and filtered.
The obtained powder was vacuum-dried at 60 ° C. for 12 hours to obtain a target solid electrolyte.

FIG. 3 shows an X-ray diffraction spectrum of the obtained solid electrolyte. By comparing the spectrum of AlH ₂ P ₃ O ₁₀ of FIG. 2 with the powder data of AlH ₂ P ₃ O ₁₀ (PDF: 00-036-0320) (middle spectrum), the P ₃ O ₁₀ structure is maintained. It was confirmed that.

  In addition, ICP analysis of the obtained solid electrolyte was performed. As a result, the element ratio of Li, P, and Al in the solid electrolyte was Li: P: Al = 1.07: 3.13: 1.00.

As described above, the obtained solid electrolyte has a P ₃ O ₁₀ structure and an AlO ₆ structure, and the composition formula is LiAlHP ₃ O ₁₀ (that is, in the composition formula (1), X is about 1.0 ) Was confirmed.

<Lithium ion conductivity>
After the obtained solid electrolyte was compacted at 28 MPa, pellets (diameter 10 mm, thickness 0.5 mm) were obtained. An Au electrode (electrode area: 0.785 cm ² ) was formed on both surfaces of the pellet by a crimping method, and connected to an AC impedance analyzer (AUTOLAB PGSTAT30, manufactured by Metrohm Autolab). The applied voltage was 50 mV and the frequency range was 1 M-0.1 Hz. As a result, a Cole-Cole plot showing a semicircle of 200 kΩ was obtained. As a result, the lithium ion conductivity was 3 × 10 ⁻⁷ S / cm.
Specifically, the Au electrode was formed by uniformly spreading 20 mg of Au powder (made by Nilaco, 2-5 μm, dendritic shape) on one surface of the solid electrolyte and crimping at 28 MPa.

Regarding the above embodiments, the following supplementary notes are further disclosed.
(Appendix 1)
Having Li, Al, P, H, and O as constituent elements,
A solid electrolyte having a P ₃ O ₁₀ structure and an AlO ₆ structure which is a hexacoordinate octahedral structure.
(Appendix 2)
The solid electrolyte according to Supplementary Note 1 represented by the following composition formula (1).
_{Li x AlH 2.0-x P 3} O 10 ··· composition formula (1)
However, in the composition formula (1), x satisfies 0 <x ≦ 2.0.
(Appendix 3)
A positive electrode active material-containing layer, a negative electrode active material-containing layer, and a solid electrolyte layer interposed between the positive electrode active material-containing layer and the negative electrode active material-containing layer,
The solid electrolyte layer is a layer composed of a solid electrolyte,
The solid electrolyte has Li, Al, P, H, and O as constituent elements, and further has a P ₃ O ₁₀ structure and an AlO ₆ structure that is a six-coordinate octahedral structure.
An all-solid-state battery comprising:
(Appendix 4)
The all-solid-state battery according to Supplementary Note 3, wherein the solid electrolyte is represented by the following composition formula (1).
_{Li x AlH 2.0-x P 3} O 10 ··· composition formula (1)
However, in the composition formula (1), x satisfies 0 <x ≦ 2.0.

REFERENCE SIGNS LIST 1 positive electrode current collector 2 positive electrode active material containing layer 3 solid electrolyte layer 4 negative electrode active material containing layer 5 negative electrode current collector

Claims (2)

Having Li, Al, P, H, and O as constituent elements,
And P ₃ O ₁₀ structure, the AlO ₆ structure is 6-coordinated octahedral structure possess,
A solid electrolyte represented by the following composition formula (A) .
LiAlHP ₃ O _10: Composition formula (A) A positive electrode active material-containing layer, a negative electrode active material-containing layer, and a solid electrolyte layer interposed between the positive electrode active material-containing layer and the negative electrode active material-containing layer,
The solid electrolyte layer is a layer composed of a solid electrolyte,
The solid electrolyte has Li, Al, P, H, and O as constituent elements, and further includes P ₃ O ₁₀ Structure and a six-coordinate octahedral structure, AlO ₆ Having a structure represented by the following composition formula (A):
An all-solid-state battery comprising:
LiAlHP ₃ O ₁₀     ... Composition formula (A)