JP5731278B2 - All-solid-state lithium ion battery - Google Patents

Description

  The present invention relates to an all solid lithium ion battery.

  An all-solid-state lithium ion battery that uses an inorganic solid electrolyte and does not use organic substances as an electrode is expected to be a safe battery because there is no concern about leakage of the organic electrolyte or gas generation from the organic electrolyte. In addition, the all-solid-state lithium ion battery is less likely to cause side reactions other than the battery reaction as compared with the liquid battery, and thus can be expected to have a longer life than the liquid battery.

  As an example of the all-solid-state lithium ion battery, a battery in which a positive electrode layer and a negative electrode layer are laminated on both sides of a solid electrolyte layer can be given. In particular, when a sintered body is used as the inorganic solid electrolyte layer, a solid electrolyte layer or an unsintered body thereof is laminated with unsintered bodies of a positive electrode layer and a negative electrode layer, and these are fired at the same time, whereby an electrode or a solid electrolyte is obtained. These sintered bodies are produced at the same time, and these interfaces are well bonded. Therefore, it is expected to reduce the manufacturing cost by reducing the manufacturing process of the all-solid-state lithium ion battery and to reduce the ion transfer resistance at the junction interface between the electrode layer and the solid electrolyte layer.

Here, in Patent Document 1, the polyanion contained in the positive electrode layer, the negative electrode layer, and the solid electrolyte layer is composed of PO ₄ and SO ₄ , and these are made to have the same chemical structure, so that A technique for improving conductivity is disclosed.

Non-Patent Document 1 discloses a technique in which a polyanion constituting a positive electrode active material contained in a positive electrode layer is composed of SiO ₄ or BO ₃ .

JP 2007-258165 A

Ikuo Yamada “Structure and electrode properties of new oxoacid cathode materials”, materials for the 68th New Battery Concept Committee Meeting, New Battery Concept Section, Electrochemical Society Battery Technology Committee, March 2, 2009, p. 1-10

However, in the combination disclosed in Patent Document 1 and Non-Patent Document 1, it is difficult to increase the charge / discharge voltage, and thus there remains a problem in increasing the output of the all-solid-state battery. In particular, when the polyanion constituting the positive electrode active material is composed of SiO ₄ having an electronegativity lower than that of PO ₄ , fine particles and complexing with carbon are performed in order to increase the output voltage of the all-solid-state battery. In addition, it is necessary to reduce side reactions with moisture in the air. Also, when the polyanion constituting the positive electrode active material was composed of BO _3, the output voltage of the all-solid-state battery is insufficient.

In particular, when an all-solid-state lithium ion battery is used as a secondary battery, the function as an electrode active material may be impaired due to oxidation, reduction, or decomposition of the electrode active material while the charge / discharge cycle is repeated. Since the compound which inhibits is produced | generated, there exists a problem that a discharge capacity tends to fall by the repeated charging / discharging of a secondary battery, and cycling characteristics are low. For example, an all-solid-state lithium ion battery having a olivine (LiFePO ₄ ) structure and containing a positive electrode active material made of a phosphate has LiM ²⁺ PO ₄ ⇔ as the positive electrode active material desorbs Li during charging. Since the reduction of the central metal M such as M ³⁺ PO ₄ → M ²⁺ ₂ P ₂ O ₇ is likely to occur, an irreversible decomposition reaction is likely to occur.

  That is, even if the electrode layer-solid electrolyte layer interface is satisfactorily bonded by firing, deterioration due to a chemical reaction of the electrode active material occurs, and as a result, charging and discharging of a large current becomes difficult.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an all-solid-state lithium ion battery that has a high output voltage and is less likely to have a reduced discharge capacity even after repeated charge and discharge. There is.

  As a result of intensive studies in view of such a situation, the present inventors made charging while maintaining the output voltage of the all-solid-state battery by keeping the polyanion portion of the positive electrode active material within a specific composition range. It was found that the irreversible decomposition reaction of the positive electrode active material due to Li desorption at the time can be suppressed. Specifically, the present invention provides the following.

_{(1) Li x Al y M} z P q E r O 4 positive electrode active material made, all-solid-state lithium-ion battery having a positive electrode layer containing a lithium ion conductive solid electrolyte.
Here, 0.9 ≦ x ≦ 1.9, 0 ≦ y ≦ 0.5, 0.5 ≦ z ≦ 0.95, 0.5 ≦ q ≦ 0.95 and 0.05 ≦ r ≦ 0.5 M is one or more selected from Fe, Mn, Co, and Ni, and E is one or more selected from B and Si.

  (2) The positive electrode layer includes the positive electrode active material and a lithium ion conductive solid electrolyte, and a mass ratio of the solid electrolyte to the positive electrode active material is 1/9 or more and 9 or less. All solid lithium ion battery.

  (3) The all-solid-state lithium ion battery according to (1) or (2), wherein the positive electrode active material is coated with carbon.

  (4) The all-solid-state lithium ion battery in any one of (1) to (3) in which the said positive electrode layer contains 1 mass% or more and 20 mass% or less of conductive support agents.

(5) The lithium ion conductive solid electrolyte is Li _{1 + x + z} (Al, Sc, Y, Ga, La) _x (Ti, Zr, Ge) _2−x P _3−z Si _z O ₁₂ (0 ≦ X ≦ 1, 0 ≦ Z <1), γ-Li ₃ PO ₄ , a garnet structure, a perovskite structure, or a Li ₂ S—P ₂ S ₅ crystal, comprising (1) to (4) The all-solid-state lithium ion battery in any one.

  According to the present invention, it is possible to provide an all-solid-state lithium ion battery having a high output voltage and high cycle characteristics.

It is a graph which shows the result of having performed X-ray diffraction (XRD) with respect to the positive electrode active material of Example 1 of this invention. It is a graph which shows the relationship between the cycle number of charging / discharging and discharge capacity in the positive electrode half cell of Example 1 of this invention. It is a graph which shows the relationship between content of Si and B of a positive electrode active material, and discharge capacity in the positive electrode half-cell of Example 1 of the present invention. It is a graph which shows the relationship between the cycle number of charging / discharging and discharge capacity in the all-solid-state lithium ion battery of Example 2 of this invention.

All-solid-state lithium-ion batteries of the present _invention, the _{Li x Al y M z P q} E r O 4 as the positive electrode active material, the electrolyte is a lithium ion conductive solid electrolyte. Here, 0.9 ≦ x ≦ 1.9, 0 ≦ y ≦ 0.5, 0.5 ≦ z ≦ 0.95, 0.5 ≦ q ≦ 0.95 and 0.05 ≦ r ≦ 0.5 M is one or more selected from Fe, Mn, Co, and Ni, and E is one or more selected from B and Si. Among the polyanion sites of the positive electrode active material, in particular, one or more of B and Si and P are used in combination, and the composition ratio is within a specific range, while the output voltage of the all-solid-state battery is maintained high. The irreversible decomposition reaction accompanying the reduction of the positive electrode active material from M ³⁺ to M ^{2+ due} to the elimination of Li during charging is suppressed. Therefore, an all-solid-state lithium ion battery having a high output voltage and high cycle characteristics when used as a secondary battery can be provided.

  Hereinafter, embodiments of the all-solid-state lithium ion battery and the method for producing the same of the present invention will be described in detail, but the present invention is not limited to the following embodiments, and within the scope of the object of the present invention, Changes can be made as appropriate. In addition, although description may be abbreviate | omitted suitably about the location where description overlaps, the meaning of invention is not limited.

[All-solid-state lithium-ion battery]
The all-solid-state lithium ion battery of the present invention has an electrode layer made of two inorganic solids, a positive electrode layer and a negative electrode layer, across a solid electrolyte layer, and a current collector is bonded to each electrode layer. . In this specification, the positive electrode layer and the negative electrode layer are collectively referred to as an electrode layer, and the positive electrode active material and the negative electrode active material are collectively referred to as an electrode active material.

<Positive electrode layer>
The positive electrode layer in this embodiment is composed of at least a positive electrode active material and a solid electrolyte, but may contain a conductive additive.

(Positive electrode active material)
Among these, the positive electrode active material is Li _x Al _y M _z P _{q Er} O ₄ (where 0.9 ≦ x ≦ 1.9, 0 ≦ y ≦ 0.5, 0.5 ≦ z ≦ 0.95). 0.5 ≦ q ≦ 0.95 and 0.05 ≦ r ≦ 0.5 are satisfied, M is one or more selected from Fe, Mn, Co, and Ni, and E is selected from B and Si. More than species). Using _{Li x Al y M z P q} E r O 4 as the positive electrode active material, by setting the percentage of each component constituting the positive electrode active material within a predetermined range, the electronegativity to polyanion site of the positive electrode active material Since high P is contained, the fall of the output voltage of an all-solid-state battery is suppressed. At the same time, by using Si or B having a valence smaller than P, the polyanion structure becomes electron-excess, so that the irreversible decomposition reaction accompanied by reduction of the positive electrode active material from M ³⁺ to M ²⁺ during charging. Is suppressed. Further, deterioration in the structure of the positive electrode active material due to repeated charge and discharge is suppressed. Therefore, an all-solid-state lithium ion battery having a high output voltage and high cycle characteristics when used as a secondary battery can be provided.

  Here, M in the above formula is one or more selected from Fe, Mn, Co, and Ni, but it is more preferable that it contains at least Co, and most preferably a solid solution of Co and Ni. Thereby, it is possible to ensure the electron conductivity and increase the charge / discharge voltage. At this time, the ratio of the Ni content to the sum of the Co and Ni contents is preferably 5 to 70 mol%, more preferably 7 to 65 mol%, and most preferably 10 to 60 mol%. preferable.

  Further, E in the above formula is at least one selected from Si and B, but it is more preferable that at least Si is contained, and Si is most preferable. Accordingly, Si having a small difference in valence with P is contained in the positive electrode active material, so that the positive electrode active material can easily maintain the olivine structure, so that the positive electrode active material can occlude and release lithium ions. Therefore, the discharge capacity and the output voltage can be increased.

  Here, r in the formula is preferably from 0.05 to 0.5, more preferably from 0.05 to 0.2, and most preferably from 0.1 to 0.2. Further, q in the formula is preferably from 0.5 to 0.95, more preferably from 0.8 to 0.95, and most preferably from 0.8 to 0.9. In particular, by setting r to 0.05 or more and q to 0.95 or less, the irreversible reduction reaction of the positive electrode active material during charging is reduced, so that a secondary battery with higher cycle characteristics can be obtained. Can do. On the other hand, when r is 0.5 or less and q is 0.5 or more, the positive electrode active material can easily maintain the olivine structure, so that the discharge capacity and the output voltage can be increased. The total of r and q in the formula is preferably 0.90 or more and 1 or less, more preferably 0.95 or more and 1 or less, and most preferably 1. This makes it difficult for elements other than P, Si, and B to enter the polyanion portion of the positive electrode active material, so that the olivine structure of the positive electrode active material can be easily maintained.

As such a positive electrode active material, for example, Li _1.1 Co _0.5 Ni _0.5 P _0.9 Si _0.1 O ₄ , Li _1.4 Co _0.5 Ni _0.5 P _0.8 B _{0 .2} O ₄ , Li _1.2 Co _0.5 Ni _0.5 P _0.8 Si _0.2 O ₄ , Li _1.5 Co _0.5 Ni _0.5 P _0.5 Si _0.5 O ₄ Li _1.05 Co _0.5 Ni _0.5 P _0.95 Si _0.05 O ₄ or the like can be used. Among these, Li _1.1 Co _0.5 Ni _0.5 P _0.9 Si _0.1 O ₄ is particularly preferable from the viewpoint of further improving the cycle characteristics of the all-solid-state lithium ion battery.

  The content of the positive electrode active material in the positive electrode layer is preferably 1% by mass or more and 20% by mass or less with respect to the entire material of the positive electrode layer. In particular, when the content is 1% by mass or more, the discharge capacity of the all-solid-state lithium ion battery can be increased. Therefore, the lower limit of the content of the positive electrode active material is preferably 1% by mass, more preferably 2% by mass, and most preferably 4% by mass. On the other hand, by setting the content to 20% by mass or less, the ion conductivity and the electronic conductivity of the solid electrolyte electrode layer can be increased, so that higher charge / discharge characteristics can be easily ensured. Therefore, the upper limit of the content of the positive electrode active material is preferably 20% by mass, more preferably 15% by mass, and most preferably 10% by mass.

  It is also preferable that a coating layer made of a conductor such as carbon is formed on the surface of the crystal grain boundary of the positive electrode active material in the present embodiment. Thereby, since it becomes easy for the coating layer which has electroconductivity to exist in the crystal grain boundary of a positive electrode active material, transfer of the electron accompanying occlusion and discharge | release of lithium ion can be performed more smoothly. In order to obtain this effect, the thickness of the coating layer formed at the crystal grain boundary of the positive electrode active material is preferably 1 nm to 1 μm, more preferably 3 nm to 100 nm, and most preferably 5 nm to 10 nm. In order to obtain this effect, the covering area of the coating layer is preferably 5% or more of the surface area of the crystal grain boundary of the positive electrode active material, more preferably 40% or more, and 60% or more. Most preferably. On the other hand, from the viewpoint of securing a path through which lithium ions are conducted and suppressing a decrease in discharge capacity, the covering area of the covering layer is preferably 99% or less of the surface area of the crystal grain boundary of the positive electrode active material. % Or less is more preferable, and 95% or less is most preferable.

  Here, the thickness of the coating layer formed at the crystal grain boundary of the electrode active material can be measured by slicing the electrode layer and observing a sample in a fine powder state with a TEM (transmission electron microscope). it can. Further, since the ratio of the area covered by the coating layer to the surface area of the crystal grain boundary is difficult to measure three-dimensionally, the coating layer has a total length of the boundary of the crystal grain boundary appearing in the TEM image. Let the ratio of length be the ratio of this area. When the crystal grain boundary cannot be observed with TEM, the existing area ratio can be obtained in the same manner by observing by mapping analysis with EPMA. The ratio of the area covered by the coating layer may not be measured for all the parts of the electrode layer, and a measured value in a TEM observation image of an arbitrarily selected part can be used. In addition, even if the ratio of the area covered by the coating layer in a specific part of the electrode layer (for example, 3% or less of the volume of the electrode layer) is different from the other part, the other part is in the present invention. The electrode layer can obtain the effects of the present invention as long as it matches the area ratio of the coating layer defined in (1).

(Solid electrolyte)
As the solid electrolyte, a material having lithium ion conductivity can be used. For example, LiN, LISICON, La _0.55 Li _0.35 TiO ₃ having a perovskite structure, a substance having a NASICON type structure (for example, Li _{1 + X} Al _{x (Ti, Ge) 2-} X (PO 4) 3, Li 1 + x Al x Ti 2-x (PO 4) 3, Li 1.5 Al 0.5 Ge 1.5 (PO 4) 3 and LiTi ₂ P ₃ O _{12 and} other general formulas Li _{1 + x + z} (Al, Sc, Y, Ga, La) _x (Ti, Zr, Ge) _2−x P _3−z Si _z O ₁₂ (0 ≦ X ≦ 1, 0 ≦ Z < A material including at least one of the substance represented by 1) and γ-Li ₃ PO ₄ , etc.), a garnet structure, and Li ₂ S—P ₂ S ₅ can be used. As a result, a lithium ion conduction path is easily formed between the electrode layer and the solid electrolyte layer, and the lithium ion conduction is promoted to reduce the internal resistance of the all solid lithium ion battery. An all-solid-state lithium ion battery with a high output voltage can be produced.

Among them, Li _{1 + x + z} E _y G _{2 -j} Si _z P _{3 -z} O ₁₂ (where j, x, y, and z are 0 ≦ x ≦ 0.8, 0 ≦ z ≦ 0.6, and y is 0) ≦ y ≦ 0.6, j satisfies 0 ≦ j ≦ 0.6, E is one or more selected from Al and Ga, and G is one or more selected from Ge, Ti, Zr, Y, and Sc) A substance containing crystals has an advantage that it has high lithium ion conductivity, is chemically stable, and is easy to handle. Further, this crystal can be precipitated as a crystal in glass ceramics by heat-treating a glass having a specific composition. The glass-ceramic particles containing this crystal are preferable in that they have almost no vacancies or crystal grain boundaries that hinder ion conduction.

  Here, the glass ceramic is a substance obtained by heat-treating an amorphous glass to precipitate a crystal phase in the glass phase, and means a substance composed of an amorphous solid and a crystal. Further, it includes a substance in which all of the glass phase is phase-transitioned into a crystalline phase, that is, a substance whose crystal amount (crystallinity) in the substance is 100% by mass.

As the raw glass that can precipitate the crystal by heat treatment,
In mol% display based on oxide,
Li ₂ O: 10 to 25%,
_{Al 2 O 3 + Ga 2 O} 3: 0.5~15%,
TiO ₂ + GeO ₂ + ZrO ₂ + Y ₂ O ₃ + Sc ₂ O ₃ : 25 to 50%,
SiO _2: 0~15%, and P ₂ O _5: 26~40%
Glass obtained by melting and quenching a glass raw material having the composition range of

  Here, as a means for causing the positive electrode layer to contain a solid electrolyte, there is a means for mixing the glass ceramic powder or glass ceramic raw glass powder into a positive electrode active material or a conductive additive. Here, when the raw glass powder is used, the glass ceramics can be formed by precipitating crystals in the glass powder when firing the solid electrolyte layer or the electrode layer. That is, the raw glass capable of precipitating the crystals is an inorganic solid that can exhibit lithium ion conductivity after sintering.

The content of the solid electrolyte in the positive electrode layer is preferably 1/9 or more and 9 or less, more preferably 2/8 or more and 6/4 or less, by mass ratio with respect to the positive electrode active material in the positive electrode layer. Most preferably, it is 7 or more and 4/6 or less. Using _{Li x Al y M z P q} E r O 4 as a cathode active material, and by defining the amount of the solid electrolyte to positive electrode active material, when charging the all-solid-state lithium-ion batteries and during the firing of the electrode layer In addition, since the decomposition of the positive electrode active material at the interface between the positive electrode layer and the solid electrolyte layer and the grain boundary between the positive electrode active material and the solid electrolyte and the generation of compounds that greatly inhibit ionic conduction are effectively suppressed, The discharge capacity of the lithium ion battery can be increased and the cycle characteristics can be improved.

(Conductive aid)
In this embodiment, carbon, a metal composed of at least one of Ni, Fe, Mn, Co, Mo, Cr, Ag, and Cu, and alloys thereof can be used as the conductive assistant. Alternatively, a metal such as titanium, stainless steel, or aluminum, or a noble metal such as platinum, silver, gold, or rhodium may be used. It may also be used metal oxides such as WO ₃ or SnO _2. By using such a material having a high electron conductivity as a conductive additive, the amount of current that can be conducted through the narrow electron conduction path formed in the electrode layer increases, so the charge / discharge characteristics of the all-solid-state lithium ion battery are improved. be able to.

  The content of the conductive auxiliary agent is preferably 1% by mass or more and 20% by mass or less with respect to the entire electrode material of the positive electrode layer in consideration of the balance between the discharge capacity and the electron conductivity of the positive electrode layer. % To 15% by mass is more preferable, and 4% to 10% by mass is most preferable.

<Negative electrode layer>
The negative electrode layer in this embodiment preferably contains at least a negative electrode active material. In addition to these negative electrode active materials, the above-mentioned solid electrolyte and conductive aid may be added.

(Negative electrode active material)
The negative electrode active material is preferably at least one selected from an oxide containing NASICON, olivine, and spinel crystals, an amorphous metal oxide, or a metal alloy. Among them, Li _{1 + x + z} Al _y Ti ₂ Si _z P _3-z O ₁₂ (where x, y, and z are 0 ≦ x ≦ 0.8, 0 ≦ z ≦ 0.6, and y is 0 ≦ y ≦ 0. 6), Li ₃ V ₂ (PO ₄ ) ₃ , Li ₃ Fe ₂ (PO ₄ ) ₃ , LiFePO ₄ , Li ₄ Ti ₅ O ₁₂ , LiTiO, TiO ₂ , SiO _x (0.25 ≦ x ≦ 2 ), Cu ₆ Sn ₅ is more preferable. This facilitates the joining of the solid electrolyte and the negative electrode active material, and facilitates the transfer of lithium ions between the solid electrolyte and the positive electrode active material, thereby further improving the charge / discharge characteristics of the all solid lithium ion battery. be able to. In particular, by comprising LiTiO and / or TiO _x , the negative electrode potential can be lowered, so that the output voltage from the all-solid-state lithium ion battery can be further increased. Specific examples of the negative electrode active material include Li ₂ V ₂ (PO ₄ ) ₃ , Li ₂ Fe ₂ (PO ₄ ) ₃ , LiFePO ₄ , Li ₄ Ti ₅ O ₁₂ , SiO _x (0.25 ≦ x ≦ 2). ), Cu ₆ Sn ₅ can be used.

  Here, it is also preferable that the negative electrode active material is formed with a coating layer made of carbon similarly to the positive electrode active material. Thereby, since it becomes easy for the coating layer which has electroconductivity to exist in the crystal grain boundary of a negative electrode active material, the transfer of the electron accompanying occlusion and discharge | release of lithium ion can be performed more smoothly. The preferred thickness of the coating layer formed at the crystal grain boundary of the negative electrode active material and the ratio of the preferred coating area of the coating layer to the surface area of the crystal grain boundary of the negative electrode active material are the same as those of the positive electrode active material.

(Solid electrolyte)
When the negative electrode layer contains a solid electrolyte, the mass ratio of the solid electrolyte to the negative electrode active material is preferably 1/9 or more and 10 or less, more preferably 2/8 or more and 6/4 or less, and 3/7 or more. 4/6 or less is most preferable. Thereby, since the lithium ion conduction path between the solid electrolyte layer joined to the negative electrode layer and the active material in the negative electrode layer is well formed, the lithium ion conductivity in the negative electrode layer can be increased, The output voltage of the lithium ion battery can be increased.

<Solid electrolyte layer>
The solid electrolyte layer physically separates the positive electrode layer and the negative electrode layer and is responsible for conduction of lithium ions between the positive electrode layer and the negative electrode layer. The positive electrode layer and the negative electrode layer are joined to the solid electrolyte layer. Here, one of the positive electrode layer and the negative electrode layer is preferably bonded by firing, and more preferably both the positive electrode layer and the negative electrode layer are bonded by baking. Thereby, the conductivity of the lithium ion inside the all-solid-state lithium ion battery can be increased, and the mechanical strength of the all-solid-state lithium ion battery can be increased.

  The solid electrolyte layer in this embodiment preferably contains at least the above-mentioned solid electrolyte.

The contents of the solid electrolyte, electrode active material, and conductive additive contained in the all solid lithium ion battery of the present invention and the composition thereof are determined by shaving the solid electrolyte layer and / or electrode layer constituting the all solid lithium ion battery. Using an energy loss analyzer or X-ray analyzer mounted on a field emission transmission electron microscope (FE-TEM), or an X-ray analyzer mounted on a field emission scanning microscope (FE-SEM) Can be specified. By using such quantitative analysis or point analysis, for example, the presence or absence of the positive electrode active material in the positive electrode layer and its content can be known. Here, when an X-ray analyzer is used, since Li ₂ O cannot be directly analyzed, the Li ₂ O content can be estimated by calculating the charge from other components.

[Production of all-solid-state lithium-ion batteries]
The all solid lithium ion battery of the present invention can be produced by firing the electrode layer precursor and the solid electrolyte layer precursor to form the electrode layer and the solid electrolyte layer. More specifically, the electrode layer precursor and the solid electrolyte layer precursor are each fired, stacked, and fired again to join the layers, or any one of the electrode layer precursor and the solid electrolyte layer precursor. After firing the sinter into a sintered body, another precursor is laminated on the sintered body, and the sintered body and the precursor are fired at the same time, and two or more layer precursors are laminated. Although the method of joining an interlayer etc. is formed, forming a sintered compact by baking simultaneously, It is not limited to these, A various aspect can be used. In the present invention, the electrode layer precursor and the solid electrolyte layer precursor mean an unfired body of the electrode layer and an unfired body of the solid electrolyte layer, respectively.

(Mixing of raw materials)
In preparing the electrode layer precursor and the solid electrolyte layer precursor, first, a raw material composition is prepared by mixing the powdered solid electrolyte with an electrode active material, a conductive auxiliary agent, and the like as necessary. Thereby, uneven distribution of each component is reduced by mixing a raw material composition uniformly. Therefore, particularly in the electrode layer, the electrode active material can be easily adjacent to both the solid electrolyte and the conductive additive, and desired high discharge capacity and output voltage can be easily obtained.

  As a specific aspect for preparing the raw material composition for the electrode layer, for example, an aspect for preparing a raw material composition in which a powdered solid electrolyte, an electrode active material, and a conductive additive are mixed with a solvent or a binder can be cited. Moreover, as a specific aspect which produces the raw material composition of a solid electrolyte, the aspect which produces the raw material composition by which the solvent and binder were mixed, for example with the powdery solid electrolyte is mentioned. Thereby, since fluidity | liquidity is brought to a raw material composition at normal temperature, shaping | molding of a raw material composition can be performed easily. However, in this embodiment, it is preferable to reduce the solvent and binder contained in the raw material composition, and it is most preferable that these are not contained at all. Thereby, when the electrode layer precursor and the solid electrolyte layer precursor are baked, the volatilization of the solvent, the binder, and the like is reduced, so that it is possible to obtain an all solid lithium ion battery with fewer voids and high charge / discharge characteristics. .

  Here, the solid electrolyte powder and the electrode active material powder contained in the raw material composition of the electrode layer and the solid electrolyte layer may be those having the above crystal phase or those capable of forming the above crystal phase, It may be in the form of glass ceramics or raw glass. In particular, the positive electrode active material used in the present invention is prepared by uniformly mixing oxides, carbonates, phosphates, and the like of each constituent element according to the stoichiometric ratio, and firing this to produce a crystalline phase. can do.

  Among these, the average particle diameter of the solid electrolyte powder contained in the raw material composition of the solid electrolyte layer is preferably 0.1 μm to 3 μm, more preferably 0.1 μm to 1 μm, and most preferably 0.1 μm to 0.6 μm. By reducing the average particle diameter of the solid electrolyte powder in this way, the solid electrolyte layer is densely formed and the voids are reduced, so that the ionic conductivity of the electrode layer and the solid electrolyte layer is increased, and the all solid lithium ion battery The charge / discharge characteristics can be improved. Further, by setting the average particle diameter of the solid electrolyte powder to 0.1 μm or more, the time required for pulverizing the solid electrolyte powder can be reduced.

  On the other hand, the average particle diameter of the electrode active material powder contained in the raw material composition of the electrode layer is preferably 0.1 μm to 10 μm, more preferably 0.1 μm to 3 μm, and most preferably 0.1 μm to 1 μm. The average particle size of the solid electrolyte powder contained in the electrode layer material composition is preferably 0.1 μm to 10 μm, more preferably 0.1 μm to 1 μm, and most preferably 0.1 μm to 0.6 μm. Thus, by reducing the average particle size of the electrode active material powder and the solid electrolyte powder contained in the raw material composition of the electrode layer, the reaction area for exchanging lithium ions in the electrode layer is increased. The charge / discharge characteristics of the ion battery can be enhanced. Further, by setting the average particle size of these powders to 0.1 μm or more, the time required for pulverizing the solid electrolyte powder can be reduced.

  The average particle diameter of the conductive additive powder contained in the electrode layer raw material composition as necessary is preferably 10 nm to 3 μm, more preferably 10 nm to 1 μm, and most preferably 10 nm to 50 nm. Thereby, since it becomes easy to exchange electrons with the electrode active material powder by the conductive additive, the discharge capacity of the all-solid-state lithium ion battery can be increased. Further, by setting the average particle diameter of the conductive additive powder to 10 nm or more, the time required for pulverizing the conductive additive powder can be reduced.

  The “average particle diameter” in the present specification is D50 (cumulative 50% diameter) on a volume basis measured by a laser diffraction / scattering particle size distribution measuring device, and specifically, a particle size analyzer manufactured by Nikkiso Co., Ltd. A value measured by Microtrac MT3300EXII or a submicron particle analyzer N5 manufactured by Beckman Coulter can be used. The average particle diameter is a value represented.

  At this time, a coating layer made of a conductor may be formed on the surface of the electrode active material powder prior to preparation of the raw material composition for the electrode layer. For example, by drying the moisture while mixing the electrode active material powder and an aqueous solution of saccharides such as sucrose and glucose, heat treatment under an inert atmosphere in the graphite crucible forms a coating layer made of carbon on the electrode active material powder it can.

(Formation of electrode layer precursor and solid electrolyte layer precursor)
Next, the raw material composition is molded to form an electrode layer precursor and a solid electrolyte layer precursor. Thereby, since a raw material composition is shape | molded by the electrode layer precursor of a predetermined shape, and a solid electrolyte layer precursor, it can be easy to obtain the all-solid-state battery which has a predetermined shape.

  As a specific aspect of molding the raw material composition, it is preferable to have a step of supplying the raw material composition into the inside of a mold and flattening the surface of the raw material composition. Moreover, you may shape | mold by pressurizing a raw material composition. As a result, the powdery raw material composition is supplied to the inside of the mold at a constant thickness to form the electrode layer precursor and the solid electrolyte layer precursor. When fired, a positive electrode layer, a negative electrode layer and / or a solid electrolyte layer having a certain thickness can be easily formed. As the step of flattening the surface of the raw material composition, for example, a rod-shaped member having the same shape and size as the opening of the mold can be used.

  In addition, the electrode layer precursor and the solid electrolyte layer precursor may be formed by pressure forming the raw material composition as described above, but the electrode layer precursor is formed by forming a green sheet from the raw material composition. Alternatively, a solid electrolyte layer precursor may be produced. Thereby, since it becomes easy to form into a thin plate shape or an arbitrary shape, an all-solid-state lithium ion battery having an arbitrary shape can be manufactured.

  Here, the green sheet is formed by mixing an organic binder, a plasticizer, a solvent and the like with the powder of the raw material composition described above to form a mixed slurry, and after forming the mixed slurry into a thin plate shape, the solvent is volatilized. It means the green body to be formed. The green sheet can be formed by a doctor blade, a calendar method, a coating method such as spin coating and dip coating, a printing method, a die coater method, and a spray method. Since the green sheet before firing is flexible, it can be cut into any shape or laminated.

  As the organic binder, a general-purpose binder that is commercially available as a molding aid for press molding, rubber press, extrusion molding, or injection molding can be used. Specifically, acrylic resin, ethyl cellulose, polyvinyl butyral, methacrylic resin, urethane resin, butyl methacrylate, vinyl-based copolymer, and the like can be used. The content of the organic binder with respect to the total amount of the mixed slurry is preferably 1% by mass, more preferably 3% by mass, and most preferably 5% by mass in order to easily obtain a green sheet having a desired shape. Further, the content of the organic binder with respect to the total amount of the mixed slurry is preferably 50% by mass, more preferably 40% by mass, and most preferably 30% by mass, in order to easily reduce voids after degreasing.

  The solvent may be used for uniformly dispersing the powder of the raw material composition. As the solvent, known materials such as PVA, IPA, butanol, toluene, xylene, acetonitrile, NMP and the like can be used, but alcohol or water is preferable in that the influence on the environment can be reduced. In addition, in order to obtain a more homogeneous and dense solid electrolyte, it is also possible to add an appropriate amount of a dispersant, and in order to improve foam removal during mixing and drying of the mixed slurry, an appropriate amount of a surfactant or the like is added. May be.

Moreover, it is also preferable to contain simultaneously the inorganic compound containing Li in a green sheet. Thereby, since the inorganic compound containing Li works as a sintering aid (binder), the particles can be bonded more firmly at the time of firing. Examples of the inorganic compound containing Li include Li ₃ PO ₄ , LiPO ₃ , LiI, LiN, Li ₂ O, Li ₂ O _2, and LiF.

  The thickness of the green sheet formed by one molding is preferably 300 μm or less, more preferably 150 μm or less, and most preferably 100 μm or less. As a result, when the green sheet is dried, the amount of the solvent remaining in the sheet is reduced, so that the occurrence of cracks on the surface of the green sheet can be reduced. On the other hand, the thickness of the green sheet formed by one molding is preferably 1 μm or more, more preferably 5 μm or more, and most preferably 10 μm or more. Thereby, since it becomes difficult to damage a green sheet, the stable handling property can be given. Moreover, in order to make the solid electrolyte layer and electrode layer after firing have a desired thickness, the same type of green sheets may be laminated. In order to further improve the denseness of the solid electrolyte layer after firing, the green sheet may be pressed by a roll press, uniaxial, isotropic pressurization or the like.

  When a green sheet is laminated to produce a solid electrolyte layer precursor or an electrode layer precursor, the upper limit of the thickness of the green sheet after lamination is preferably 2 mm or less, more preferably 1 mm or less from the viewpoint of shortening the firing time. 800 μm or less is most preferable. Further, the lower limit value of the thickness of the green sheet is preferably 30 μm or more, more preferably 100 μm or more, and most preferably 200 μm or more in order to reduce waviness due to firing. In order to prevent the green sheet laminate from being bent or damaged when fired, it is also preferable to laminate these green sheets on a support and fire.

(Baking of electrode layer precursor and solid electrolyte layer precursor)
Next, the electrode layer precursor and the solid electrolyte layer precursor are fired. As a result, the solid electrolyte, the electrode active material, and the conductive additive constituting the solid electrolyte layer precursor and the electrode layer precursor are firmly bound, and therefore, the electrode layer having high lithium ion conductivity and high mechanical strength and / or A solid electrolyte layer can be produced.

  Here, the maximum temperature when firing the electrode layer precursor can be set within a range in which the solid electrolyte, the electrode active material, and the conductive additive are firmly bonded and do not melt or change phase. preferable. That is, the maximum temperature is preferably 750 ° C. or higher and 1100 ° C. or lower, more preferably 850 ° C. or higher and 1050 ° C. or lower, and most preferably 900 ° C. or higher and 1000 ° C. or lower. On the other hand, the maximum temperature when firing the solid electrolyte layer precursor is preferably 750 ° C. or higher and 1100 ° C. or lower, more preferably 850 ° C. or higher and 1050 ° C. or lower, and most preferably 900 ° C. or higher and 1000 ° C. or lower.

In this case, the use of the _{Li x Al y M z P q} E r O 4 as the positive electrode active material, even when the firing in making the positive electrode layer, hardly occur thermal decomposition of the positive electrode active material, and, It becomes difficult to produce a compound that greatly inhibits ion conduction at the interface between the positive electrode active material and the solid electrolyte. Therefore, it is possible to provide an all solid lithium ion battery having a larger charge / discharge capacity. This also facilitates the direct bonding between the solid electrolyte and the positive electrode active material, and facilitates the transfer of lithium ions between the solid electrolyte and the positive electrode active material. A battery can be provided.

When the electrode layer precursor or the solid electrolyte layer precursor is fired, it is preferably fired in an atmosphere containing at least one gas selected from N ₂ , H ₂ , He, Ar, CO ₂ , CO, and CH ₄ . Thereby, deterioration and burning of a solid electrolyte, an electrode active material, a conductive additive, and a heat treatment apparatus can be suppressed.

The thickness of the electrode layer after firing is preferably 5 μm to 1 mm, more preferably 10 μm to 500 μm, and most preferably 20 to 100 μm. Here, if the electrode layer is too thick, the ion migration resistance in the electrode layer increases, and if the electrode layer is too thin, the discharge capacity decreases. In addition, in the case where one electrode layer (for example, the negative electrode layer) is provided with a function as a support, the thickness of the electrode layer may have an upper limit of 2 mm.
On the other hand, the thickness of the solid electrolyte layer after sintering is sufficient if the negative electrode and the positive electrode can be separated, and a thinner one is preferable. However, in consideration of mechanical strength, 1 μm to 100 μm is preferable, 1 μm to 50 μm is more preferable, and 1 μm to 20 μm is most preferable.

  In preparing the all solid lithium ion battery of this embodiment, a current collector may be stacked on the formed electrode layer. As a means for laminating the current collector, a thin metal layer may be laminated on the electrode layer after firing, and the current collector and its precursor are laminated on the electrode layer precursor, followed by firing and bonding. May be. Further, if the electrode layer has high electron conductivity, the current collector may be omitted.

  Hereinafter, the all-solid-state lithium ion battery of the present invention will be described with specific examples.

[Preparation of solid electrolyte raw glass]
As raw materials, H ₃ PO ₄ , Al (PO ₃ ) ₃ , Li ₂ CO ₃ , SiO ₂ and TiO ₂ were used, and these were mol% in terms of oxide, P ₂ O ₅ was 35.0%, Al ₂ O ₃ Is 7.5%, Li ₂ O is 15.0%, TiO ₂ is 38.0%, and SiO ₂ is 4.5%. The glass melt was melted for 4 hours with stirring at 1500 ° C. Thereafter, the glass melt was dropped into running water to obtain flaky glass.

  This flaky glass was pulverized with a lab-scale jet mill and classified by a zirconia rotating roller to prepare a powder having an average particle diameter of 20 μm. This powder was further pulverized by a planetary ball mill, an attritor, a bead mill or the like to obtain an original glass powder (hereinafter referred to as an original glass powder) of lithium ion conductive glass ceramics (solid electrolyte) having an average particle diameter of 0.6 μm.

[Preparation of positive electrode active material]
Li ₂ CO ₃ , CoO, NiO, LiPO ₃ , SiO ₂ , H ₃ BO ₃ were used as raw materials, and Li, Co, Ni, P, Si, B stoichiometric amounts of each positive electrode active material listed in Table 1 They were weighed so as to achieve a theoretical ratio, mixed uniformly, then placed in an alumina crucible, and fired at 1000 ° C. for 1 hour in an electric furnace to obtain a positive electrode active material. In the same procedure, Li _{1 + x} Co _0.5 Ni _0.5 P _1-x Si _x O ₄ and Li _{1 + 2x} Co _0.5 Ni _0.5 P _1-x B _x O ₄ (x = 0 To 0.6) was obtained. Among these, the X-ray diffraction (XRD) pattern of the positive electrode active material Li _1.2 Co _0.5 Ni _0.5 P _0.8 Si _0.2 O ₄ is shown in FIG.

[Pretreatment of positive electrode active material]
The obtained positive electrode active material was pulverized. To 10 g of the positive electrode active material, 40 g of denatured ethanol and 200 g of zirconia balls having a diameter of 10 mm (YTZ balls, manufactured by Tosoh Corporation) were placed in a 250 cc zirconia pot, and pulverized at 250 rpm for 100 minutes using a planetary ball mill. Thereafter, the zirconia balls were changed to 300 g having a diameter of 0.5 mm, and pulverization was performed at 300 rpm for 100 minutes. The particle diameter of the positive electrode active material after pulverization was approximately 0.5 μm in terms of D50 (cumulative 50% diameter) on a volume basis. This positive electrode active material was dried at 80 ° C. for 10 hours, the dried positive electrode active material was transferred to a 120 cc plastic cup, 150 g of zirconia balls having a diameter of 10 mm (YTZ ball, manufactured by Tosoh Corporation) were added, and crushed at 120 rpm for 15 hours. Processed. The average particle diameter of the positive electrode active material after pulverization was approximately 2.0 μm in terms of D50 (cumulative 50% diameter) on a volume basis.

[Preparation of porous positive electrode layer precursor green sheet]
Prepare the positive electrode active material, raw glass powder, pore former (polymer beads Φ6μm), acrylic binder, dispersant, antifoaming agent and deionized water in the amounts shown in Table 1 and place them in a 120cc plastic cup. A positive electrode slurry was prepared by using a planetary ball mill for 12 hours using 150 g of zirconia balls having a diameter of 10 mm (YTZ ball, manufactured by Tosoh Corporation). This positive electrode slurry was formed into a sheet shape with a 100 μm gap on a PET film by a doctor blade method. After forming, it was dried and released from the PET film. The formed sheet had a thickness of 30 μm, and was used as a porous positive electrode layer precursor green sheet.

[Preparation of solid electrolyte layer precursor green sheet]
140.0 g of raw glass powder (average particle size 0.6 μm), acrylic binder 140.0 g, dispersant 7.0 g, antifoaming agent 3.0 g, plasticizer 2.0 g and deionized water 90.0 g were prepared, A YTZ ball (made by Nikkato Co., Ltd., diameter: 10 mm) was put and mixed for 12 hours with a planetary ball mill to prepare a solid electrolyte slurry. This solid electrolyte slurry was formed into a sheet shape with a 100 μm gap on a PET film by a doctor blade method. After forming, it was dried and released from the PET film. The formed sheet had a thickness of 25 μm, and this sheet was used as a solid electrolyte layer precursor green sheet.

[Step of obtaining green sheet sintered body (lamination and firing)]
The porous positive electrode layer precursor green sheet and the solid electrolyte layer precursor green sheet were fired to obtain a positive electrode porous body. Here, a porous positive electrode layer precursor green sheet and a solid electrolyte layer precursor green sheet were laminated and fired simultaneously. Specifically, two porous positive electrode layer precursor green sheets and 12 solid electrolyte layer precursor green sheets are laminated in order, and a hot water laminator device (WIP device, manufactured by Nikkiso Co., Ltd.) is used. After pressurizing for 1 minute under a load of 80 ° C and 2t, cut into a size of 30mm in diameter, sandwiched by a quartz plate (diameter 40mm, thickness 1mm), and fired at 950 ° C for 10 minutes while circulating air did. Thereby, the laminated body by which the porous body containing the positive electrode active material used as a positive electrode layer and the solid electrolyte layer were joined by sintering was produced.

[Filling conductive additive powder]
A conductive material powder was filled in the porous body formed in the positive electrode layer of the laminate. As a slurry containing a conductive additive, a conductive paste (manufactured by Lion Corporation, Lion Paste W-370C) was used. This includes ketjen black having an average particle size of 0.04 μm as a conductive additive, the solvent is water, and the concentration of the slurry is 16 wt%. This slurry was filled in the positive electrode layer porous body of the laminate using a spin coater. After the slurry was filled, the outer periphery of the laminate was polished with # 1000 water-resistant abrasive paper to maintain insulation between the positive electrode side and the negative electrode side. Thereafter, the laminate was fired by heating to 180 ° C. in an electric furnace.

[Production of polymer electrolyte]
After preparing 7.7 g of Zeospan (manufactured by ZEON CORPORATION), 2.3 g of LiTFSI (manufactured by Morita Chemical Co., Ltd.) and 70.0 g of denatured ethanol, the mixture was stirred at 1400 rpm at atmospheric pressure for 10 minutes using a rotating / revolving mixer. Thereafter, the pressure was reduced to 150 torr and the mixture was stirred for 3 minutes to degas. The obtained gel polymer was molded into a sheet with a 700 μm gap on a PET film by the doctor blade method. After forming, it was dried and released from the PET film. The formed sheet had a thickness of 50 μm, and this sheet was used as a polymer electrolyte.

[Battery]
A polymer electrolyte was affixed to the solid electrolyte layer of the produced laminate, and lithium metal cut to a diameter of 20 mm was affixed on the polymer electrolyte to produce a positive electrode half-cell cell. On the lithium metal side of the cell, a copper foil with a thickness of 25 μm, in which a lead with a width of 5 mm was attached in a circle with a diameter of 25 mm, was arranged as a current collector to form a negative electrode. On the other hand, in the positive electrode layer of the cell, an aluminum foil having a thickness of 25 μm obtained by attaching a lead having a width of 5 mm to a circle having a diameter of 25 mm was disposed as a current collector to form a positive electrode. These were vacuum-packed with an aluminum laminate film to ensure contact between the cell, copper foil and aluminum foil.

[Charge / discharge test]
About the produced positive electrode half cell, the charge / discharge cycle test was done and transition of the discharge capacity of the unit weight (positive electrode reference | standard) with respect to the number of charge / discharge cycles was measured.
Charging was performed at a charge rate of 0.05 C until the charging voltage reached the voltage shown in Table 2, and then the charging was terminated when the charging capacity reached the theoretical capacity while maintaining the charging voltage. After charging, the battery was discharged at a discharge rate of 0.05 C, and the discharge was terminated when the discharge voltage reached 3.0V. Here, 50 cycles were repeated with charging and discharging as one cycle, and the discharge capacity after each cycle was measured. In addition, the environmental temperature and measurement temperature at the time of charging / discharging were 60 degreeC.

[result]
Table 2 shows the results of the charge / discharge test of the positive electrode half-cell produced in this example. FIG. 2 shows the relationship between the number of charge / discharge cycles and the discharge capacity in the positive electrode half-cell produced in this example, and FIG. 3 shows the relationship between the contents of Si and B in the positive electrode active material and the discharge capacity.

  As shown in Table 1 and FIG. 2, after performing 50 cycles of the charge / discharge test for the discharge capacity after performing the charge / discharge test for only one cycle in the examples (1-A to 1-E) of the present invention. The cycle retention ratio representing the ratio of the discharge capacity was 36% or more. On the other hand, the cycle maintenance factor in the comparative example (1-a · 1-b) of the present invention was 26% or less. Therefore, it became clear that the positive electrode half cell produced in the example of the present invention has improved cycle characteristics as compared with the positive electrode half cell of the comparative example. For this reason, it is guessed that the all-solid-state lithium ion battery of this invention has higher cycling characteristics.

  Further, as shown in FIG. 3, it was found that the cycle retention rate was increased when 5% or more of P in the polyanion portion of the positive electrode active material was substituted with Si or B compared with the case where P was not substituted. On the other hand, it has been clarified that those in which 50% or more of P in the polyanion portion of the positive electrode active material is substituted with Si or B have a lower cycle maintenance ratio than those without substitution. For this reason, the all-solid-state lithium ion battery of the present invention has higher cycle characteristics when it is replaced with Si or B in the range of 5% to 50% of P in the polyanion portion of the positive electrode active material. It is inferred.

  Further, as shown in FIG. 3, it was also clarified that those in which P in the polyanion portion of the positive electrode active material was replaced with Si had a higher cycle retention rate than those in which P in the polyanion portion was replaced with B. For this reason, it is guessed that the all-solid-state lithium ion battery of the present invention has higher cycle characteristics when the P in the polyanion portion of the positive electrode active material is replaced with Si.

[Preparation of solid electrolyte raw glass]
A raw glass powder (hereinafter referred to as raw glass powder) of lithium ion conductive glass ceramics (solid electrolyte) having an average particle diameter of 0.6 μm was obtained in the same procedure as in Example 1.

[Preparation of positive electrode active material]
Li ₂ CO ₃ , CoO, NiO, LiPO ₃ , SiO ₂ , H ₃ BO ₃ were used as raw materials, and Li, Co, Ni, P, Si, B stoichiometry of each positive electrode active material listed in Table 3 They were weighed so as to achieve a theoretical ratio, mixed uniformly, then placed in an alumina crucible, and fired at 1000 ° C. for 1 hour in an electric furnace to obtain a positive electrode active material.

[Pretreatment of positive electrode active material]
The obtained positive electrode active material was pulverized. To 10 g of the positive electrode active material, 40 g of denatured ethanol and 200 g of zirconia balls having a diameter of 10 mm (YTZ balls, manufactured by Tosoh Corporation) were placed in a 250 cc zirconia pot, and pulverized at 250 rpm for 100 minutes using a planetary ball mill. Thereafter, the zirconia balls were changed to 300 g having a diameter of 0.5 mm, and pulverization was performed at 300 rpm for 100 minutes. The particle diameter of the positive electrode active material after pulverization was approximately 0.5 μm in terms of D50 (cumulative 50% diameter) on a volume basis. This positive electrode active material was dried at 80 ° C. for 10 hours, the dried positive electrode active material was transferred to a 120 cc plastic cup, 150 g of zirconia balls having a diameter of 10 mm (YTZ ball, manufactured by Tosoh Corporation) were added, and crushed at 120 rpm for 15 hours. Processed. The average particle diameter of the positive electrode active material after pulverization was approximately 2.0 μm in terms of D50 (cumulative 50% diameter) on a volume basis.

[Pretreatment of negative electrode active material]
The negative electrode active material Li ₄ Ti ₅ O ₁₂ was subjected to a surface treatment. 2.5 g of a 20 wt% sucrose solution was added to 10 g of a negative electrode active material having an average particle size (volume basis D50) of 20 μm, mixed in a mortar and dried, and then placed in a carbon crucible. A dish containing graphite powder was placed above the carbon crucible and fired in a nitrogen atmosphere at 600 ° C. for 3 hours.

[Preparation of porous positive electrode layer precursor green sheet]
Prepare the positive electrode active material, raw glass powder, pore former (polymer beads Φ6μm), acrylic binder, dispersant, antifoaming agent and deionized water in the amounts shown in Table 3, and place them in a 120cc plastic cup. A positive electrode slurry was prepared by using a planetary ball mill for 12 hours using 150 g of zirconia balls having a diameter of 10 mm (YTZ ball, manufactured by Tosoh Corporation). This positive electrode slurry was formed into a sheet shape with a 100 μm gap on a PET film by a doctor blade method. After forming, it was dried and released from the PET film. The formed sheet had a thickness of 30 μm, and was used as a porous positive electrode layer precursor green sheet.

[Preparation of solid electrolyte layer precursor green sheet]
140.0 g of raw glass powder (average particle size 0.6 μm), acrylic binder 140.0 g, dispersant 7.0 g, antifoaming agent 3.0 g, plasticizer 2.0 g and deionized water 90.0 g were prepared, A YTZ ball (made by Nikkato Co., Ltd., diameter: 10 mm) was put and mixed for 12 hours with a planetary ball mill to prepare a solid electrolyte slurry. This solid electrolyte slurry was formed into a sheet shape with a 100 μm gap on a PET film by a doctor blade method. After forming, it was dried and released from the PET film. The formed sheet had a thickness of 25 μm, and this sheet was used as a solid electrolyte layer precursor green sheet.

[Preparation of porous negative electrode layer precursor green sheet]
In the amount shown in Table 4, raw glass powder (average particle size 0.6 μm), spherical carbon (average particle size 20 μm) as a pore-forming agent, binder, dispersant, antifoaming agent and deionized water are prepared, A YTZ ball (made by Nikkato Co., Ltd., diameter: 10 mm) was put and mixed for 12 hours with a planetary ball mill to prepare a negative electrode slurry. This negative electrode slurry was molded into a sheet with a 100 μm gap on a PET film by the doctor blade method. After forming, it was dried and released from the PET film. The formed sheet had a thickness of 30 μm, and this sheet was used as a porous negative electrode layer precursor green sheet.

[Step of obtaining green sheet sintered body (lamination and firing)]
The porous positive electrode layer precursor green sheet and the porous negative electrode layer precursor green sheet were fired to obtain a porous body. Here, a porous positive electrode layer precursor green sheet, a solid electrolyte layer precursor green sheet and a porous negative electrode layer precursor green sheet were laminated and fired simultaneously. Specifically, two porous positive electrode layer precursor green sheets, 12 solid electrolyte layer precursor green sheets, and two porous negative electrode layer precursor green sheets are laminated in order, After pressurizing with a laminator device (WIP device, manufactured by Nikkiso Co., Ltd.) with a load of 2 t for 1 minute, it is punched into a diameter of 30 mm, sandwiched between quartz plates (diameter 40 mm, thickness 1 mm), and air Firing was carried out at 950 ° C. for 10 minutes while flowing. Thereby, the laminated body by which the porous body containing the positive electrode active material used as a positive electrode layer, the solid electrolyte layer, and the porous body used as a negative electrode layer were joined by sintering was produced.

[Filling of negative electrode active material]
A negative electrode active material subjected to the surface treatment in the amount shown in Table 5, 2.0 g of an acrylic binder, 0.2 g of a dispersant, and 6.0 g of modified ethanol were mixed to prepare a negative electrode slurry. This was applied to a porous body to be the negative electrode layer of the laminate, and the slurry at the peripheral edge was wiped off with a waste cloth. The slurry was dried in the air, and then fired in a nitrogen atmosphere at 500 ° C. for 10 minutes.

[Filling conductive additive powder]
The conductive material powder was filled in the porous body formed in the positive electrode layer and the negative electrode layer of the laminate. As a slurry containing a conductive additive, a conductive paste (manufactured by Lion Corporation, Lion Paste W-370C) was used. This includes ketjen black having an average particle size of 0.04 μm as a conductive additive, the solvent is water, and the concentration of the slurry is 16 wt%. This slurry was filled in the positive electrode layer porous body of the laminate using a spin coater. After the slurry was filled, the outer periphery of the laminate was polished with # 1000 water-resistant abrasive paper to maintain insulation between the positive electrode side and the negative electrode side. Then, it heated at 150 degreeC with the electric furnace, the laminated body was baked, and the cell of the all-solid-state lithium ion battery was produced.

[Battery]
A copper foil with a thickness of 25 μm, in which a lead with a width of 5 mm was attached in a circle with a diameter of 25 mm, was placed on the negative electrode layer of the produced cell, thereby forming a negative electrode. On the other hand, an aluminum foil having a thickness of 25 μm, in which a lead having a width of 5 mm was attached to a circular shape having a diameter of 25 mm, was disposed on the positive electrode layer of the cell to form a positive electrode. These were vacuum-packed with an aluminum laminate film to ensure contact between the cell, copper foil and aluminum foil.

[Charge / discharge test]
About the produced all-solid-state lithium ion battery, the charging / discharging cycle test was done and transition of the discharge capacity of the unit weight (positive electrode reference | standard) with respect to the number of charging / discharging cycles was measured.
Charging was performed at a charging rate of 0.05 C until the charging voltage reached 4 V, and then the charging was terminated when the charging capacity reached the theoretical capacity while maintaining the charging voltage of 4 V. After charging, the battery was discharged at a discharge rate of 0.05C, and the discharge was terminated when the discharge voltage reached 0.01V. Here, 50 cycles were repeated with charging and discharging as one cycle, and the discharge capacity after each cycle was measured. In addition, the environmental temperature and measurement temperature at the time of charging / discharging were 120 degreeC.

[result]
Table 5 shows the charge / discharge test results of the all-solid-state lithium ion battery produced in this example. FIG. 4 shows the relationship between the number of charge / discharge cycles and the discharge capacity in the all-solid-state lithium ion battery produced in this example.

  As shown in Table 1 and FIG. 2, in the example (2-A) of the present invention, the discharge capacity after 50 cycles of the charge / discharge test with respect to the discharge capacity after 1 cycle of the charge / discharge test. The cycle maintenance ratio representing the ratio was 56%. On the other hand, the cycle maintenance factor in Comparative Example (2-a) of the present invention was 1%. Therefore, it became clear that the all-solid-state lithium ion battery of the example of the present invention has improved cycle characteristics as compared with the all-solid-state lithium ion battery of the comparative example.

  Although the present invention has been described in detail for the purpose of illustration, this embodiment is only for the purpose of illustration, and many modifications can be made by those skilled in the art without departing from the spirit and scope of the present invention. Will be understood.

Claims (5)

Li _x M _z P _q E and the positive electrode active material made _r O _4, all-solid-state lithium ion battery characterized by having a positive electrode layer containing lithium ion conductive solid electrolyte, a.
Here, 1.05 ≦ x ≦ 1.9, z = 1.0, 0.5 ≦ q ≦ 0.95 and 0.05 ≦ r ≦ 0.5 are satisfied, and the sum of r and q is 1. , M is at least one selected from Co and Ni, and E is at least one selected from B and Si.   2. The all solid lithium according to claim 1, wherein the positive electrode layer includes the positive electrode active material and a lithium ion conductive solid electrolyte, and a mass ratio of the solid electrolyte to the positive electrode active material is 1/9 or more and 9 or less. Ion battery.   The all-solid-state lithium ion battery according to claim 1, wherein the positive electrode active material is coated with carbon.   The all-solid-state lithium ion battery in any one of Claim 1 to 3 in which the conductive support agent is contained in the said positive electrode layer 1 mass% or more and 20 mass% or less. The lithium ion conductive solid electrolyte is Li _{1 + x + z} (Al, Sc, Y, Ga, La) _x (Ti, Zr, Ge) _2−x P _3−z Si _z O ₁₂ (0 ≦ X ≦ 1, 0 ≦ Z <1), γ-Li ₃ PO ₄ , garnet structure, perovskite structure, any crystal of Li ₂ S—P ₂ S ₅ , All solid lithium ion battery.

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