JP2017228453A - All-solid-state battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an all-solid-state battery that can be manufactured without requiring high temperature treatment.SOLUTION: The all-solid-state battery includes: a positive electrode active material layer containing positive electrode active material particles and lithium perchlorate; a solid electrolyte layer; and a negative electrode.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an all solid state battery.

  2. Description of the Related Art In recent years, secondary batteries that store electric energy have attracted attention for application to hybrid vehicles, electric vehicles, and the like. In addition, energy harvesting technology that generates power from small environmental energy is attracting attention as an energy-saving technology, and the secondary battery that can store and supply the generated electrical energy has widespread potential for various applications. Has been. For example, application to a sensor or the like in combination with energy harvesting is also being studied.

  In these applications, all-solid-state batteries that do not use liquid as an electrolyte (see, for example, Patent Document 1) are attracting a great deal of attention because there is no risk of liquid leakage.

  As one aspect of the all solid state battery, there is an aspect in which a positive electrode active material layer is formed using positive electrode active material particles and a binder. As this aspect, for example, an all solid state battery in which lithium borate is used as a binder and lithium cobaltate is used as positive electrode active material particles has been reported (for example, see Non-Patent Document 1). However, the preparation of the positive electrode active material layer in this report requires heat treatment at 700 ° C. When the positive electrode active material layer is produced at such a high temperature, there may be a problem that the battery resistance is increased.

JP 2005-38843 A

Shingo Ohta et al. , Journal of Power Sources, 238, (2013) 53-56.

  An object of this invention is to provide the all-solid-state battery which can be produced without requiring a high temperature process.

In one embodiment, the all-solid battery is
A cathode active material layer containing cathode active material particles and lithium perchlorate;
A solid electrolyte layer;
A negative electrode.

  As one aspect, an all-solid battery that can be manufactured without requiring high-temperature treatment can be provided.

FIG. 1 is a schematic cross-sectional view for explaining a state in which a different phase is formed in an all-solid battery. FIG. 2 is a schematic diagram of another example of the disclosed all solid state battery. FIG. 3 is a charge / discharge curve of the all-solid-state battery of Example 1. FIG. 4 is a charge / discharge curve of the all-solid-state battery of Example 2.

(All-solid battery)
The disclosed all solid state battery includes at least a positive electrode active material layer, a solid electrolyte layer, and a negative electrode, and further includes other members as necessary.

  When a positive electrode active material layer is formed using lithium borate as a binder, a high temperature of about 700 ° C. is required to melt lithium borate. Then, depending on the type of the positive electrode active material particles, as shown in FIG. 1, the surface of the positive electrode active material particles 111 surrounded by the binder 112 or the positive electrode active material layer 11 and the solid are processed at a high temperature. A heterogeneous phase 119 is formed at the interface with the electrolyte layer 12. This heterogeneous phase 119 causes a decrease in battery performance such as an increase in battery resistance, and in some cases deprives the function as a battery.

Therefore, the present inventors have intensively studied to provide an all solid state battery that can be manufactured without requiring high temperature treatment.
As a result, it was found that by using lithium perchlorate as a binder when producing the positive electrode active material layer, an all-solid battery can be produced without requiring high-temperature treatment, and the present invention has been completed.
Since high temperature treatment is not required, the formation of a heterogeneous phase can be prevented, and an all solid state battery in which the performance of the positive electrode active material particles and the performance of the solid electrolyte layer are well reflected can be obtained.
In addition, since high temperature treatment is not required, energy used for manufacturing an all-solid battery can be reduced.

<Positive electrode active material layer>
The positive electrode active material layer contains at least positive electrode active material particles and lithium perchlorate, preferably contains a conductive material, and further contains other components as necessary.

<< Positive electrode active material particles >>
There is no restriction | limiting in particular as said positive electrode active material particle, According to the objective, it can select suitably, For example, lithium containing complex oxide etc. are mentioned. 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 according to the purpose. For example, LiCoO ₂ , LiNiO ₂ , LiCrO ₂ , LiVO ₂ , LiM _x Mn _2−x O ₄ (M is at least one of Co, Ni, Fe, Cr, and Cu, 0 ≦ x <2), LiFePO ₄ , LiCoPO ₄ , Li ₂ CoP ₂ O ₇ etc. are mentioned.
These may be used individually by 1 type and may use 2 or more types together.

Examples of the lithium-containing composite oxide include lithium cobaltate (LiCoO ₂ ) and lithium cobalt pyrophosphate (Li ₂ CoP ₂ O ₇ ), LiCoO ₂ is preferable in terms of proven results, and Li ₂ CoP ₂ O ₇ has a potential. It is preferable in that it can be increased.

There is no restriction | limiting in particular as an average particle diameter of the said positive electrode active material particle, Although it can select suitably according to the objective, 0.05 micrometer-20 micrometers are preferable, and 0.1 micrometer-10 micrometers are more preferable.
The average particle diameter can be obtained, for example, by an arithmetic average value when arbitrarily observing 50 particles with an electron microscope.

<< Lithium perchlorate >>
The lithium perchlorate (LiClO ₄ ) functions as a binder in the positive electrode active material layer, and prevents the positive electrode active material particles from being detached from the positive electrode active material layer.

  There is no restriction | limiting in particular as content of the said lithium perchlorate in the said positive electrode active material layer, Although it can select suitably according to the objective, 15 mass parts or more with respect to 100 mass parts of the said positive electrode active material particles. 50 parts by mass or less is preferable. When the content is less than 15 parts by mass, the battery resistance may be decreased. When the content exceeds 50 parts by mass, the content of the positive electrode active material particles is relatively decreased, resulting in a decrease in battery capacity. Sometimes.

<< Conductive material >>
The conductive material has a function of ensuring electrical conductivity in the positive electrode active material layer.
There is no restriction | limiting in particular as said electrically conductive material, According to the objective, it can select suitably, For example, carbon black, graphite, etc. are mentioned.
Examples of the carbon black include ketjen black, acetylene black, furnace black, and thermal black.
Among these, ketjen black is preferable in that it exhibits excellent conductivity with a very small amount, and excellent conductivity can be obtained with addition of a small amount.

  There is no restriction | limiting in particular as content of the said electrically conductive material in the said positive electrode active material layer, Although it can select suitably according to the objective, The total amount of the said positive electrode active material particle and the said lithium perchlorate is 100 mass parts. On the other hand, 5 mass parts or more and 40 mass parts or less are preferable, and 10 mass parts or more and 30 mass parts or less are more preferable.

  There is no restriction | limiting in particular as average thickness of the said positive electrode active material layer, Although it can select suitably according to the objective, 1 micrometer-300 micrometers are preferable, and 10 micrometers-100 micrometers are more preferable.

As a method for forming the positive electrode active material layer, for example, a paste containing the positive electrode active material particles, the lithium perchlorate, a solvent, and preferably the conductive material is applied onto the solid electrolyte layer. And a method of performing a heat treatment after removing the solvent.
The solvent is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include γ-butyrolactone and terpineol.
The heat treatment may be heating at a low temperature, and the heating temperature is preferably 100 ° C. to 250 ° C., more preferably 130 ° C. to 200 ° C. The lithium perchlorate has a melting point of about 260 ° C. and is preferably heat-treated at a temperature lower than the melting point.
Even in heat treatment at 200 ° C. or lower, the lithium perchlorate functions as a binder.

<Solid electrolyte layer>
The solid electrolyte layer is not particularly limited as long as it is a layer composed of a solid electrolyte, and can be appropriately selected according to the purpose.

  The solid electrolyte is not particularly limited as long as it is a solid electrolyte having lithium ion conductivity, which is a carrier responsible for battery reaction, and can be appropriately selected according to the purpose. For example, an oxide-based solid electrolyte And sulfide-based solid electrolytes.

  Examples of the oxide solid electrolyte include perovskite oxides, NASICON oxides, LISICON oxides, and garnet oxides.

Examples of the perovskite oxide include Li-La-Ti perovskite oxides such as Li _a La _1-a TiO ₃ and Li _b La _1-b TaO _3. that Li-La-Ta-based perovskite type _oxide, in Li _{c La 1-c} NbO represented by Li-La-Nb-based perovskite type oxide as such ₃ and the like (the above formula, 0 <a < 1, 0 <b <1, 0 <c <1.)

As the NASICON type oxide, for _{example, Li 1 + l Al l Ti} 2-l (PO 4) in _{Li m X n Y o P p} O q ( Formula to ShuAkira crystals typified by _3, X Is at least one element selected from the group consisting of B, Al, Ga, In, C, Si, Ge, Sn, Sb, and Se, and Y is Ti, Zr, Ge, In, Ga, Sn And at least one element selected from the group consisting of Al, and 0 ≦ l ≦ 1, m, n, o, p, and q are arbitrary positive numbers. Can be mentioned.

Examples of the LISICON-type oxide include Li ₄ XO ₄ -Li ₃ YO ₄ (wherein X is at least one element selected from Si, Ge, and Ti, and Y is P, An oxide represented by at least one element selected from As and V).

Examples of the garnet-type oxide include Li-La-Zr-based oxides typified by lithium lanthanum zirconate (Li ₇ La ₃ Zr ₂ O ₁₂ ).

Examples of the sulfide-based solid electrolyte include Li ₂ S—P ₂ S ₅ , Li ₂ S—SiS ₂ , Li _3.25 P _0.25 Ge _0.76 S ₄ , and Li _4-r Ge _1-r. P _r S ₄ (where a 0 ≦ r ≦ _1.), such as _{Li 7 P 3 S 11, Li} 2 S-SiS 2 -Li 3 PO 4 and the like. The sulfide-based solid electrolyte may be either a crystalline sulfide or an amorphous sulfide.

In addition, as long as the crystal structure is equivalent, these solid electrolytes may be those in which some of the elements are replaced with other elements, or may have different element composition ratios.
Moreover, these solid electrolytes may be used individually by 1 type, and may use multiple types.

  As the solid electrolyte, lithium lanthanum zirconate is preferable because it has no reactivity with the Li negative electrode.

  There is no restriction | limiting in particular as average thickness of the said solid electrolyte layer, Although it can select suitably according to the objective, 100 micrometers-2,000 micrometers are preferable, 300 micrometers-1,500 micrometers are more preferable, 500 micrometers-1,000 micrometers are preferable. Particularly preferred.

  A method for forming the solid electrolyte layer is not particularly limited and may be appropriately selected depending on the intended purpose. A sintered body obtained by firing a powder can easily produce a solid electrolyte layer having a preferable average thickness. This is preferable in terms of cost and cost reduction.

<Negative electrode>
As said negative electrode, it has at least a negative electrode active material layer, and also has other members, such as a negative electrode collector, as needed.

<< Negative electrode active material layer >>
The negative electrode active material layer is not particularly limited as long as it is a layer containing a negative electrode active material, and can be appropriately selected according to the purpose.
The negative electrode active material layer may be the negative electrode active material itself.

  There is no restriction | limiting in particular as said negative electrode active material, According to the objective, it can select suitably, For example, lithium, lithium aluminum alloy, amorphous carbon, natural graphite, artificial graphite etc. are mentioned.

  There is no restriction | limiting in particular as average thickness of the said negative electrode active material layer, Although it can select suitably according to the objective, 0.05 micrometer-3.0 micrometers are preferable, and 0.1 micrometer-2.0 micrometers are more preferable.

  There is no restriction | limiting in particular as a formation method of the said negative electrode active material layer, According to the objective, it can select suitably, For example, the vapor deposition method using the vapor deposition source of the said negative electrode active material, the said negative electrode active material is compression-molded. The method etc. are mentioned.

<< Negative electrode current collector >>
There is no restriction | limiting in particular as a magnitude | size and a structure of the said negative electrode collector, According to the objective, it can select suitably.
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.
Examples of the average thickness of the negative electrode current collector include 10 μm to 500 μm.

<Other members>
There is no restriction | limiting in particular as said other member, According to the objective, it can select suitably, For example, a positive electrode electrical power collector, a battery case, etc. are mentioned.

<< Positive electrode current collector >>
There is no restriction | limiting in particular as a magnitude | size and a structure of the said positive electrode electrical power collector, According to the objective, it can select suitably.
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.
Examples of the average thickness of the positive electrode current collector include 10 μm to 500 μm.

  The positive electrode current collector and the positive electrode active material layer may be collectively referred to as a positive electrode.

<< Battery case >>
There is no restriction | limiting in particular as said battery case, According to the objective, it can select suitably, For example, the well-known laminate film etc. which can be used with the conventional all-solid-state battery are mentioned. Examples of the laminate film include a resin laminate film, a film obtained by vapor-depositing a metal on a resin laminate film, and the like.

  There is no restriction | limiting in particular as a shape of the said all-solid-state battery, According to the objective, it can select suitably, For example, a cylindrical shape, a square shape, a button shape, a coin shape, a flat type etc. are mentioned.

  FIG. 2 is a schematic cross-sectional view of an example of the disclosed all solid state battery. In the all solid state battery of FIG. 2, the solid electrolyte layer 2 and the positive electrode active material layer 1 are laminated in this order on the negative electrode 3. The positive electrode active material layer 1 contains positive electrode active material particles 1A and lithium perchlorate 1B.

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

Example 1
Lithium cobaltate (LiCoO ₂ , average particle size 10 μm, cell seed, manufactured by Nippon Chemical Industry Co., Ltd.) and lithium perchlorate (LiClO ₄ , manufactured by Kishida Chemical Co., Ltd.) are 2: 1 in mass ratio (LiCoO ₂ : LiClO ₄ ). Ketjen black (ECP600JD, manufactured by Lion Co., Ltd.) as a conductive material was mixed with the mixed material so as to be 20% by mass with respect to the total amount of lithium cobaltate and lithium perchlorate, and γ as a solvent. -An appropriate amount of butyrolactone was added to prepare a positive electrode paste.
Next, the positive electrode paste was applied to a solid electrolyte substrate [lithium lanthanum zirconate (Li ₇ La ₃ Zr ₂ O ₁₂ ), 500 μm] so as to have a diameter of 5 mm and an average thickness of 40 μm, and the solvent was removed by drying. Heat treatment was performed at 150 ° C. for 1 h to form a positive electrode active material layer.
Thereafter, 2.0 μm of Li was formed on the surface of the solid electrolyte substrate opposite to the positive electrode active material layer by vapor deposition to obtain an all-solid lithium ion secondary battery.
About the obtained secondary battery, charging / discharging evaluation was performed using the charging / discharging evaluation apparatus (TOSCAT, the Toyo System Co., Ltd. make). The results are shown in FIG. It turns out that it is operating as a battery without problems.

(Example 2)
An all solid lithium ion secondary battery was obtained in the same manner as in Example 1 except that lithium cobaltate was changed to lithium cobalt pyrophosphate (Li ₂ CoP ₂ O ₇ , average particle diameter of 1 μm) in Example 1. It was.
About the obtained secondary battery, charging / discharging evaluation was performed using the charging / discharging evaluation apparatus (TOSCAT, the Toyo System Co., Ltd. make). The results are shown in FIG. It turns out that it is operating as a battery without problems.
In addition, lithium cobalt pyrophosphate (Li ₂ CoP ₂ O ₇ ) used in Example 2 and Comparative Example 1 was synthesized according to the literature (Hyungsub Kim, et al., Chem. Mater. 2011, 23, 3930-3937). .

(Comparative Example 1)
Lithium cobalt pyrophosphate (Li ₂ CoP ₂ O ₇ , average particle size 1 μm) and lithium borate (Li ₃ BO ₃ , manufactured by Toshima Seisakusho Co., Ltd.) in a mass ratio (Li ₂ CoP ₂ O ₇ : Li ₃ BO ₃ ) 20% by mass of ketjen black (ECP600JD, manufactured by Lion Co., Ltd.) as a conductive material with respect to the total amount of lithium cobaltate and lithium perchlorate, Then, an appropriate amount of γ-butyrolactone was added as a solvent to prepare a positive electrode paste.
Next, the positive electrode paste was applied to a solid electrolyte substrate [lithium lanthanum zirconate (Li ₇ La ₃ Zr ₂ O ₁₂ ), 500 μm] so as to have a diameter of 5 mm and an average thickness of 40 μm, and the solvent was removed by drying. Heat treatment was performed at 700 ° C. for 1 h to form a positive electrode active material layer.
Thereafter, 2.0 μm of Li was formed on the surface of the solid electrolyte substrate opposite to the positive electrode active material layer by vapor deposition to obtain an all-solid lithium ion secondary battery.
About the obtained secondary battery, charging / discharging evaluation was performed using the charging / discharging evaluation apparatus (TOSCAT, the Toyo System Co., Ltd. make). As a result, charging / discharging operation was not confirmed.
Therefore, when the positive electrode active material layer was analyzed by X-ray diffraction, it was confirmed that the Li ₂ CoP ₂ O ₇ peak disappeared and another material (heterogeneous phase) was generated.

Regarding the above embodiment, the following additional notes are disclosed.
(Appendix 1)
A cathode active material layer containing cathode active material particles and lithium perchlorate;
A solid electrolyte layer;
An all solid state battery comprising a negative electrode.
(Appendix 2)
The all-solid-state battery according to appendix 1, wherein the positive electrode active material particles are lithium cobalt pyrophosphate.
(Appendix 3)
The all-solid-state battery according to appendix 1, wherein the positive electrode active material particles are lithium cobalt oxide.
(Appendix 4)
The all solid state battery according to any one of appendices 1 to 3, wherein the positive electrode active material layer further contains a conductive material.
(Appendix 5)
The all-solid battery according to any one of supplementary notes 1 to 4, wherein the negative electrode is lithium.

DESCRIPTION OF SYMBOLS 1 Positive electrode active material layer 1A Positive electrode active material particle 1B Lithium perchlorate 2 Solid electrolyte layer 3 Negative electrode

Claims (5)

A cathode active material layer containing cathode active material particles and lithium perchlorate;
A solid electrolyte layer;
An all solid state battery comprising a negative electrode.   The all solid state battery according to claim 1, wherein the positive electrode active material particles are lithium cobalt pyrophosphate.   The all-solid-state battery according to claim 1, wherein the positive electrode active material particles are lithium cobalt oxide.   The all-solid-state battery in any one of Claim 1 to 3 in which the said positive electrode active material layer contains a electrically conductive material further.   The all-solid-state battery according to claim 1, wherein the negative electrode is lithium.