WO2019078307A1

WO2019078307A1 - Composite electrode and all solid lithium battery

Info

Publication number: WO2019078307A1
Application number: PCT/JP2018/038876
Authority: WO
Inventors: 努西▲崎▼; 田村　哲也
Original assignee: セントラル硝子株式会社
Priority date: 2017-10-20
Filing date: 2018-10-18
Publication date: 2019-04-25
Also published as: JP2019164980A

Abstract

Provided is an electrode that contributes to charging and discharging of a large amount of an electrode active material contained in the electrode, and has a capacity closer to the theoretical capacity than in the past, by reducing a solid electrolyte that does not contribute to the formation of a lithium ion conduction path. Provided is a composite electrode, the composite electrode being a sintered compact that contains an electrode active material and a solid electrolyte, wherein the composite electrode is characterized by being an alternating array in which sheet-form electrode active material layers containing an oxide-type electrode active material and sheet-form solid electrolyte layers containing an oxide-type solid electrolyte are alternatingly aligned, the width of the electrode active material layers being 10 nm to 20 µm, the width of the solid electrolyte layers being 10 nm to 20 µm, and the solid electrolyte layers passing through the composite electrode.

Description

Composite electrode and all solid lithium battery

The present invention relates to a composite electrode containing an electrode active material and a solid electrolyte, which is used for an all solid lithium battery.

Secondary batteries are used in portable devices such as mobile phones and notebook computers, transport machines for automobiles and aircraft, and power storage devices for power leveling, and the energy density is required to be improved in any application. There is. At present, the practical secondary battery with the highest energy density is a lithium ion battery, and studies are underway to try to further increase the energy density while maintaining safety. As part of that research, research is being conducted on an all-solid-state battery (a battery using a solid electrolyte instead of an electrolytic solution), which is an improvement technology of a lithium ion battery.

The all-solid battery is packaged separately by repeatedly laminating the negative electrode layer, the separator layer (lithium ion conductive layer), the positive electrode layer, and the electron conductive layer, since the negative electrode, the electrolyte and the positive electrode constituting the battery are all solid. Since it is possible to manufacture a battery having a series structure even if it is not used, it is considered to be suitable for automobiles and power storage. Furthermore, by increasing the proportion of the oxide among the negative electrode active material, the solid electrolyte, and the positive electrode active material, the all solid battery can be expected to have an effect on safety and high temperature durability in addition to energy density improvement.

In an electrode of a lithium ion battery using an electrolytic solution that has been put into practical use, the electrolytic solution that has penetrated into the gap between the positive electrode and the negative electrode functions as a lithium ion conduction path. In Patent Document 1, in order to form a lithium ion conduction path to an electrode active material in an electrode layer using a solid electrolyte, a sintered body obtained by combining an electrode active material and an oxide-based solid electrolyte is used as an electrode. Is being considered. In addition, in order to form a lithium ion conduction path to an electrode active material, it has been studied to use a composite in which the electrode active material and a solid electrolyte are mixed as an electrode (Patent Documents 2 and 3).

Further, Patent Document 4 discloses an electrode laminate in which one or more solid electrolyte layers and one or more active material layers are alternately stacked in order to secure lithium ion conductivity and obtain high capacity density. . Furthermore, Patent Document 5 discloses a manufacturing method for obtaining an active material molded body and a solid electrolyte layer by firing a first film and a second film obtained using an inkjet in order to efficiently manufacture an electrode complex. ing.

International Publication 2017/018488 JP, 2010-033877, A JP, 2013-080637, A (patent No. 5864993) JP, 2012-248468, A (patent No. 5494572) JP, 2017-004674, A

However, as described in Patent Documents 1 to 3, when the solid electrolyte is randomly distributed in the electrode, there is a solid electrolyte which does not contact the other solid electrolyte and does not contribute to the formation of the lithium ion conduction path. There is a problem that the percentage of the electrode active material still present in the electrode but not contributing to charge and discharge is not small because the solid electrolyte is locally distributed and the lithium ion conduction path does not reach the surface of the electrode. There was a point.

Further, in Patent Document 4, since sintering is not performed in the manufacturing process and there is a limit to increasing the density of the active material layer and reducing the width, an electrode that is present in the electrode but does not contribute to charge and discharge There is a problem that the proportion of active material is not small. Also in Patent Document 5, since the first film is formed by discharging the first liquid material containing the formation material of the active material by the ink jet, and the width of the first film can not be thinner than the size of the droplets of the ink jet. There has been a problem that the width of the molded article becomes large, and the proportion of the electrode active material which is present in the electrode but does not contribute to charge and discharge is not small.

The present invention has been made to solve the problems of the prior art, and by reducing the solid electrolyte not contributing to the formation of the lithium ion conduction path, many electrode activities included in the electrode are realized. An object of the present invention is to provide an electrode having a capacity closer to the theoretical capacity than in the past by contributing a substance to charge and discharge.

As a result of intensive studies, the inventors of the present invention can provide a lithium ion conduction path in a range in which lithium ions can permeate from the electrode active material, if the lithium ion conduction path is regularly provided in the electrode. It has been found that more electrode active materials in the electrode can contribute to charge and discharge, and the present invention has been completed.

Specifically, in the present invention, it is a composite electrode which is a sintered body containing an electrode active material and a solid electrolyte, and the composite electrode is a sheet-like electrode active material containing an oxide-based electrode active material. Layer and sheet-like solid electrolyte layer containing an oxide-based solid electrolyte are alternately arranged, and the width of the electrode active material layer is 10 nm or more and 20 μm or less, and the width of the solid electrolyte layer is Provided is a composite electrode having a thickness of 10 nm or more and 20 μm or less, wherein the solid electrolyte layer penetrates the composite electrode.

Further, in the present invention, a method of manufacturing the composite electrode is a method of obtaining a laminate in which a layer containing an electrode active material or a precursor thereof and a layer containing a solid electrolyte or a precursor thereof are alternately laminated. Also provided is a method for producing a composite electrode, comprising the steps of: sintering the laminate; and obtaining a laminated sintered body in which an electrode active material layer and a solid electrolyte layer are alternately laminated. Do.

According to the present invention, by reducing the solid electrolyte not contributing to the formation of the lithium ion conduction path, many electrode active materials contained in the electrode are contributed to charge and discharge, and a capacity closer to the theoretical capacity than in the past is realized. An electrode can be provided.

FIG. 1 is a schematic view of a composite electrode 10 of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS The schematic diagram of the composite electrode 21 of this invention. BRIEF DESCRIPTION OF THE DRAWINGS The schematic diagram of the all-solid-state lithium ion battery using the composite electrode 10 of this invention. (A), (b) The schematic diagram of the manufacture process of the composite electrode 10 of this invention. The schematic diagram of the composite electrode 51 of this invention. (A), (b) The schematic diagram of the manufacture process of the composite electrode 51 of this invention. FIG. 1 is a schematic view of a lithium ion battery 101 of the present invention. (A)-(d) is a schematic view of the manufacturing process of the lithium ion battery 101 of the present invention. The schematic diagram of the assembled battery 151 of this invention. The schematic diagram of the assembled battery 161 of this invention. The schematic diagram of the assembled battery 181 of this invention. FIG. 6 is a diagram showing a production flow of LTO calcined particles in Example 1; FIG. 6 is a diagram showing a production flow of LLTO pre-sintered body particles of Example 1. FIG. 6 is a diagram showing a production flow from temporary firing body particles to an arrayed sintered body of Example 1. The figure which shows the powder XRD result which grind | pulverized the laminated sintered compact of Example 1. FIG. (A), (b) Cross-sectional electron micrograph of laminated sintered body of Example 1. The figure which shows the powder XRD result which grind | pulverized the laminated sintered compact of Example 2. FIG. (A), (b) Cross-sectional electron micrograph of laminated sintered body of Example 2. The figure which shows the powder XRD result which grind | pulverized the laminated sintered compact of Example 3. FIG. (A), (b) Cross-sectional electron micrograph of laminated sintered body of Example 3. The figure which shows the powder XRD result which grind | pulverized the laminated sintered compact of Example 4. FIG. (A), (b) Cross-sectional electron micrograph of laminated sintered body of Example 4. (A) Cross-sectional electron micrograph of the laminated sintered body of Example 4 and (b) to (d) EDX mapping. The figure which shows the powder XRD result which grind | pulverized the laminated sintered compact of Example 5. FIG. (A), (b) Cross-sectional electron micrograph of laminated sintered body of Example 5. The figure which shows the powder XRD result which grind | pulverized the laminated sintered compact of Example 6. FIG. (A), (b) Cross-sectional electron micrograph of laminated sintered body of Example 6. The figure which shows the powder XRD result which grind | pulverized the laminated sintered compact of Example 7. FIG. (A), (b) Cross-sectional electron micrograph of laminated sintered body of Example 7. The figure which shows the powder XRD result which grind | pulverized the laminated sintered compact of Example 8. FIG. (A), (b) Cross-sectional electron micrograph of laminated sintered body of Example 8. The figure which shows the powder XRD result which grind | pulverized the laminated sintered compact of Example 9. FIG. (A), (b) Cross-sectional electron micrograph of laminated sintered body of Example 9. The figure which shows the powder XRD result which grind | pulverized the laminated sintered compact of Example 10. FIG. (A), (b) Cross-sectional electron micrograph of laminated sintered body of Example 10. Initial charge and discharge curves of Examples 1, 2 and 4 and Comparative Examples 1 and 3 at 90 ° C. Initial charge and discharge curves of Example 3 and Comparative Examples 2 and 4 at 90 ° C. Initial charge and discharge curves of Examples 2 and 4 to 6 at 60 ° C. Initial charge and discharge curves of Examples 7 to 10 at 60 ° C.

Hereinafter, the present invention will be described in detail. However, the description of the constituent requirements described below is an example of the embodiment of the present invention, and the present invention is not limited to these specific contents. Various modifications may be made within the scope of the present invention.

<Composite electrode>
As shown in FIG. 1, the composite electrode 10 of the present invention is a composite electrode which is a sintered body containing an electrode active material and a solid electrolyte, and in the composite electrode 10, as shown in the figure, It is characterized by having a solid electrolyte layer 13 penetrating in the thickness direction of the composite electrode.

In particular, as shown in FIG. 1, the composite electrode 10 has a flat plate shape, and the sheet-like electrode active material layer 11 parallel to the thickness direction 15 of the composite electrode and the sheet parallel to the thickness direction 15 of the composite electrode It is preferable that the solid electrolyte layers 13 in the shape of a circle are alternately arranged. In addition, as shown in FIG. 1, it is preferable that the solid electrolyte layer 13 penetrate the composite electrode 10 in the thickness direction of the composite electrode 10. When solid electrolyte 13 penetrates composite electrode 10, solid electrolyte layer 13 can be disposed near electrode active material layer 11, and the lithium ion conduction path can be spread over the entire composite electrode 10. . In addition, since the solid electrolyte 13 penetrates the composite electrode 10, the lithium ion conduction path can be made to reach the surface of the composite electrode 10, and the lithium ion can be easily from the separator layer 35 described later to the solid electrolyte layer 13. Can be moved. Although both ends of the alternate arrangement of the electrode active material layer 11 and the solid electrolyte layer 13 are the electrode active material layer 11 in FIG. 1, the end is not limited to the electrode active material layer 11, and the solid electrolyte layer 13 is It may be an end. The same applies to the other composite electrodes in the present embodiment.

The thickness C of the composite electrode 10 is preferably 10 μm or more and 3 mm or less, more preferably 15 μm or more and 1 mm or less, and particularly preferably 20 μm or more and 500 μm or less. However, the thickness C may be 100 μm or more. The depth Y of the composite electrode 10 depends on the desired device size and battery capacity, and can be determined appropriately.

The composite electrode is preferably compact. The degree of compactness can be quantified by the porosity. As an example of the measuring method of the porosity, the method of using a density is mentioned.
Porosity (%) = 100-(actual density / theoretical density) x 100
As a method of measuring the actual density, a dimension method calculated from weight and outer dimensions, Archimedes method, etc. can be used. The theoretical density can be referred to a database or calculated from the composition and crystal structure.
The porosity is preferably 40% or less, more preferably 30% or less, and particularly preferably 25% or less. The porosity is exemplified by the porosity calculated by the above equation based on the actual density measured by the Archimedes method, that is, the porosity calculated by the Archimedes method.

Both the capacity density and the power density of the composite electrode are preferably large. The capacity density can be increased by increasing the proportion of the active material. The power density can be increased by increasing the conductivity of electrons and lithium ions. The power density can be increased by increasing the proportion of the solid electrolyte and the conductive additive in the composite electrode. In the present invention, coexistence of capacity density and power density can be realized by arranging the electrode active material layer and the solid electrolyte layer efficiently. However, since there is a trade-off between capacity density and power density, the use of the battery You can decide the proportion according to. The capacity density is the power capacity per weight or volume of the battery, and the power density is the maximum amount of power that can be taken out per weight or volume of the battery.

The initial charge capacity and / or the initial discharge capacity of the composite electrode 10 is preferably 10 mAh / g or more, more preferably 30 mAh / g or more, and particularly preferably 50 mAh / g or more. The initial charge capacity and the initial discharge capacity of the composite electrode 10 were obtained by laminating the positive electrode, the separator layer, and the negative electrode in this order using the composite electrode 10 as a positive electrode, a dry polymer electrolyte or the like as a separator layer, and metallic lithium as a negative electrode. It can be evaluated by performing a charge and discharge test at a temperature of 60 ° C. and a rate of 0.002 mA / cm ² using an all solid type cell. The above capacity means the capacity per unit mass of the composite electrode obtained by dividing the capacity of the all solid cell by the mass of the composite electrode.

The width B of the electrode active material layer 11 shown in FIG. 1 is preferably 10 nm or more and 20 μm or less, more preferably 15 μm or less, still more preferably 10 μm or less, and particularly preferably 6 μm or less . If the width B of the electrode active material layer 11 is too small, the amount of the electrode active material contained in the composite electrode 10 may be small. When the width B of the electrode active material layer 11 is too large, there is a possibility that lithium ions are less likely to conduct to the electrode active material at the center of the electrode active material layer 11. In particular, by setting the width B of the electrode active material layer to 10 μm or less, more electrode active materials in the electrode can contribute to charge and discharge.

The width A of the solid electrolyte layer 13 is preferably 10 nm or more and 20 μm or less, more preferably 10 μm or less, and particularly preferably 5 μm or less. When the width A of the solid electrolyte layer 13 is too small, the cross-sectional area of the layer is reduced, the crystallinity of the particles constituting the layer is reduced, or the interface between the solid electrolyte layer 13 and the electrode active material layer 11 is It becomes difficult to ensure sufficient lithium ion conductivity due to resistance increase and the like. When the width A of the solid electrolyte layer 13 is too large, the proportion of the electrode active material contained in the composite electrode 10 decreases, and the capacity density of the composite electrode 10 decreases.

The electrode active material layer 11 and the solid electrolyte layer 13 do not necessarily have to be flat layers, and may be curved. In addition, there may be partial defects, and adjacent electrode active material layers 11 or adjacent solid electrolyte layers 13 may be in contact with each other.

The electrode active material layer 11 and the solid electrolyte layer 13 are preferably parallel to the thickness direction 15 of the composite electrode, but may be inclined up to about 45 degrees.

The aspect ratio (C / B or C / A) obtained by dividing the thickness C of the composite electrode 10 by the width A of the solid electrolyte layer 13 or the width B of the electrode active material layer 11 is preferably 10 or more. It is more preferably 50 or more, and particularly preferably 100 or more. When the thickness C of the composite electrode 10 is constant, the volume of the solid electrolyte layer 13 is reduced by decreasing the width A of the solid electrolyte layer 13 (as C / A increases). The volume can be increased to increase the capacity density of the composite electrode 10. In addition, as the width B of the electrode active material layer 11 is reduced (as C / B increases), the electrode active material layer 11 is thinner, so lithium ions can be conducted to the central portion of the electrode active material layer 11 .

Further, with regard to the number of layers to be laminated, and the width X of the composite electrode 10 determined by the widths of the electrode active material layer 11 and the solid electrolyte layer 13 and the number of layers to be laminated, the desired device size, battery capacity and It can be determined appropriately in consideration of mechanical strength and the like.

The volume ratio of the electrode active material to the solid electrolyte contained in the composite electrode 10 is preferably 5: 5 or more and 9.5: 0.5 or less. A larger amount of the electrode active material is preferable because the capacity of the composite electrode 10 is increased.

The electrode active material layer 11 is a layer containing an electrode active material. Examples of the electrode active material include oxide-based electrode active materials, carbon materials, and other materials. As the oxide-based electrode active material, a spinel type or ramsdellite type lithium titanate (a part of elements constituting lithium titanate may be replaced with another element, even if another element is doped Other elements include Mg, Cr, Zn, Co, Fe, Ni, Mn, Al, Zr, Nb, Sn, Mo, and W. Specifically, LiMg _1/2 Ti _3/2 Examples include O ₄ , LiCo _1/2 Ti _3/2 O ₄ , LiZn _1/2 Ti _3/2 O ₄ , LiCrTiO ₄ , LiFeTiO _4, etc. When one of the constituent elements is replaced with another element, When doping with another element, it is conceivable to add the other element at the time of production. The same applies to other materials), transition metal oxides (eg, titanium oxide, niobium oxide, oxide) Tungsten, molybdenum oxide, etc.), lithium transition metal oxides (e.g., lithium cobalt oxide of a layered rock-salt, lithium nickelate of layered rock-salt, the layered rock salt type called NCM ternary _{_{_{Li (Ni x Co y Mn z}}} ) _{O 2 (x + y + z} = 1), ternary layered rock-salt type called _{_{_{_{NCA Li (Ni x Co y Al}}}} z) O 2 (x + y + z = 1), spinel lithium manganate, spinel lithium manganate nickel ( LiMn _1.5 Ni _0.5 O ₄ ), LiMPO ₄ (M = Fe, Mn, Co, Ni) such as lithium olivine type lithium phosphate or lithium manganese phosphate, etc., Li ₃ V _{2 with} NASICON structure PO ₄ ) ₃ is mentioned. Moreover, as a carbon material, artificial graphite, natural graphite, graphitizable carbon, non-graphitizable carbon (hard carbon) having a spacing of (002) plane of 0.37 nm or more, and a spacing of (002) plane of 0. 0. Graphite etc. of 34 nm or less are mentioned. Other materials include elemental silicon, silicon compounds, elemental sulfur, metal sulfides (eg, Li ₂ S, SnS, NiS, etc.), metal phosphides (eg, Ni ₅ P ₄ , NiP ₂ etc.), Li ₃ PS ₄ can be mentioned.

In addition to the electrode active material, the electrode active material layer 11 may contain a sintering aid, a conductive aid, and the like. The sintering aid includes borate, silicate and phosphate, and mixtures thereof. Moreover, as a conductive support agent, metals such as gold, silver, copper and nickel, conductive oxides such as tin oxide, zinc oxide, titanium oxide and indium tin oxide, materials such as carbon, particles, fibers and rods , Tubes, etc. can be used. Examples of carbon-based conductive assistants include carbon fibers, carbon black, carbon nanotubes, carbon nanofibers, graphene, graphite and the like.

The solid electrolyte layer 13 is a layer containing a solid electrolyte. Examples of the solid electrolyte include oxide-based solid electrolytes, sulfide-based solid electrolytes, and polymer-based solid electrolytes.

As oxide-based solid electrolytes, perovskite-type oxides containing lithium, garnet-type oxides containing lithium, lithium phosphate (Li ₃ PO ₄ ), lithium niobate (LiNbO ₃ ), and LAGP with NASICON structure (Li _{1 + x} Al) _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 1), LATP with NASICON structure (Li _{1 + x} Al _x Ti _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 1)), LZP structure with NASICON structure (Li _{1 + 4x} Zr _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 0.4, part of LZP metal elements may be replaced by another metal element, even if other metal elements are doped As another metal element, Na, Sr, Ca, Mg, La, Y, Sc, Ce, In, Al, Ge, Ti, V, etc. may be mentioned. Be

The lithium-containing perovskite oxide is an oxide represented by ABO ₃ having a perovskite crystal structure, and at least one A site is selected from the group consisting of La, Sr, Ba, Na, Ca and Nd. It is preferable that the element contains a species element and Li, and the B site contains at least one element selected from the group consisting of Ti, Ta, Cr, Fe, Co, Ga and Nb. Specifically, as perovskite type oxides, lithium lanthanum titanate Li _3x La _{2/3 -x} TiO ₃ (0 ≦ x ≦ 1/6, also called LLTO), lithium lanthanum niobate (Li _x La _{(1- x) / 3} NbO ₃ ) (0 ≦ x ≦ 1), and the like. Note that part of the elements constituting lithium lanthanum titanate may be replaced with another element, or another element may be doped. Other elements include Na, K, Rb, Ag, Tl, Mg, Sr, Ca, Ba, Nb, Ta, Ru, Cr, Mn, Fe, Co, Al, Ga, Si, Ge, Zr, hf, Pr, Nd, Sm, Gd, Dy, Y, Eu, Tb and the like, _{_{_{_{specifically, La (2/3) -x Sr x}}}} Li x TiO 3, Li x La 2/3 Ti 1- _x Al _x O _{3 and the} like.
Examples of garnet-type oxides include Li ₇ La ₃ Zr ₂ O ₁₂ , Li ₅ La ₃ Nb ₂ O ₁₂ , Li ₅ La ₃ Ta ₂ O ₁₂ , and Li ₆ La ₂ BaTa ₂ O ₁₂ .

As the sulfide-based solid electrolyte, glass-based sulfides (for example, Li ₂ S-P ₂ S ₅ , Li ₂ S-SiS ₂ -P ₂ S ₅ -LiI, etc.), algirodite-type sulfides (for example, Li ₇ PS) ₆ , Li ₆ PS ₅ Cl, Li ₆ PS ₅ Br, Li ₆ PS ₅ I, etc., thiolysicon based sulfides (eg, Li _4-x Ge _1-x P _x S ₄ (0 ≦ x ≦ 1 etc)) , Li ₇ P ₃ S ₁₁ , Li ₁₀ GeP ₂ S ₁₂ (LGPS), Li _9.54 Si _1.74 P _1.44 S _11.7 Cl _0.3 (LiSiPSCl), Li _9.6 P ₃ S ₁₂ And Li-Sn-Si-P-S (LSSPS) system. As a polymer type solid electrolyte, the dry polymer electrolyte layer etc. which contain lithium salt in polymers, such as a polyethylene oxide, are mentioned.

In addition to the solid electrolyte, the solid electrolyte layer 13 may contain a sintering aid, a conductive aid, and the like. The sintering aid may, for example, be a borate, a silicate, a phosphate, a mixture thereof or the like, or a material used for the electrode active material layer. Moreover, as a conductive support agent, metals such as gold, silver, copper and nickel, conductive oxides such as tin oxide, zinc oxide, titanium oxide and indium tin oxide, materials such as carbon, particles, fibers and rods , Tubes, etc. can be used. Examples of carbon-based conductive assistants include carbon fibers, carbon black, carbon nanotubes, carbon nanofibers, graphene, graphite and the like.

The volume of the solid electrolyte contained in the solid electrolyte layer is preferably 40% or more of the volume of the solid electrolyte layer, more preferably 50% or more, and it may be a dense body of 100% solid electrolyte. The higher the volume of the solid electrolyte contained in the solid electrolyte layer, the easier it is to form the lithium ion conduction path in the thickness direction of the composite electrode.

Alternatively, a pattern may be formed in which the solid electrolyte layer is divided into a portion mainly composed of the solid electrolyte and a portion mainly composed of the electrode active material. At this time, as in the electrode complex 51 of FIG. 5, the portion 57 mainly composed of an island-like solid electrolyte that forms a sea-island structure when viewed from above is mainly composed of a sea-like electrode active material in the thickness direction. By forming a pattern so as to penetrate the portion 55, it is possible to increase the capacity of the electrode complex while securing the lithium ion conduction path. As a specific production example of such a pattern, as shown in FIG. 6A, when laminating the solid electrolyte layer 53, the portion 57 mainly composed of a strip-like solid electrolyte and the strip-like electrode active material are mainly composed. As shown in FIG. 6 (b), a laminated sintered body 61 is prepared as shown in FIG. 6 (b), and these laminated sintered bodies 61 are cut. By setting the long side direction of the strip-like portion as the thickness direction of the electrode complex 51, the portion 57 mainly composed of the strip-like solid electrolyte penetrates the electrode active material layer 11 and the electrode active material portion 55 in the thickness direction. It can be arranged.

In the present invention, the materials of the electrode active material and the solid electrolyte are not particularly limited, but from the viewpoints of safety and heat resistance, it is preferable to contain an oxide, and in the case of mainly oxide, the electrode active material The weight fraction of the oxide in the layer 11 or the solid electrolyte layer 13 is preferably 60% or more, more preferably 70% or more, and particularly preferably 80% or more. Further, since the composite electrode obtained by sintering is a dense sintered body, the volume percentage occupied by the oxide in the composite electrode is preferably 30% or more, and is 50% or more. Is more preferable, and 70% or more is particularly preferable. Further, assuming that a composite is formed by sintering, it is preferable that both the electrode active material layer 11 and the solid electrolyte layer 13 contain an oxide.

Furthermore, a composite electrode 21 having a metal layer 23 as shown in FIG. 2 may be used as the composite electrode of the present invention. The position of the metal layer 23 is not particularly limited, but as in the solid electrolyte layer 13-electrode active material layer 25-metal layer 23-electrode active material layer 25-solid electrolyte layer 13, the metal layer 23 is a solid electrolyte layer 13. Parallel to the center of the electrode active material layer 25. The electron conductivity in the composite electrode 21 can be enhanced by the metal layer 23, and in particular, parallel to the solid electrolyte layer 13, it is easy to move electrons between the electrode active material layer 25 and the current collector layer. can do. The width D of the metal layer 23 is preferably 1 nm or more and 10 μm or less, and as the material thereof, gold, silver, copper, nickel, aluminum, niobium, an alloy of two or more of these, and the like can be mentioned. Alternatively, two or more metals may be used to form the metal layer. Since the metal layer 23 can not conduct lithium ions, when the metal layer 23 is sandwiched between two electrode active material layers 25 as shown in FIG. 2, the width E of the electrode active material layer 25 does not have the metal layer 23. It is preferable that the width is half the width B of the electrode active material layer 11.

Lithium-ion battery
In the lithium ion battery of the present invention, a negative electrode layer for absorbing and desorbing lithium ions, a separator layer for conducting lithium ions, and a positive electrode layer for absorbing and desorbing lithium ions are laminated in this order as a negative electrode layer or a positive electrode layer. It is characterized by using the composite electrode of the present invention.

FIG. 3 is a view showing the lithium ion battery 31 of the present invention, in which the composite electrode 10, the separator layer 35 and the counter electrode layer 33 are laminated in order. Furthermore, normally, metal electrodes (not shown) are provided on the composite electrode layer 10 and the counter electrode layer 33. The positive electrode and the negative electrode change depending on the voltage of the electrode active material contained in each of the composite electrode 10 and the counter electrode layer 33, and when the composite electrode 10 is a positive electrode, the counter electrode layer 33 becomes a negative electrode, and the composite electrode 10 is a negative electrode. In the case of the above, the counter electrode layer 33 is a positive electrode.

For example, when the composite electrode includes spinel type or ramsdellite type lithium titanate as an electrode active material, lithium titanate is often used as a negative electrode active material of a lithium ion secondary battery, but metal lithium When a material having a charge / discharge potential relatively lower than that of lithium titanate, such as lithium alloy, is used for the counter electrode (negative electrode), it can be used as a positive electrode active material. In addition, the composite electrode of the present invention can be used as an electrode of a primary battery by using metal lithium or a lithium alloy as a counter electrode. In the present invention, a lithium ion battery includes both a primary battery and a secondary battery, and in addition to a battery using metal lithium or a lithium alloy as an electrode, electricity in which lithium ions move between a positive electrode and a negative electrode Includes the entire chemical device.

The separator layer 35 is a layer that easily conducts lithium ions and hardly conducts electrons. The lithium ion battery 31 may be an electrolyte battery, and the separator layer 35 may be a film impregnated with the electrolyte. As a film for a separator, non-woven fabric or porous sheet made of polyolefin such as polypropylene and polyethylene, cellulose, paper, glass fiber and the like is used. It is preferable that these films be micro-porous so that the electrolyte can penetrate and the ions can easily permeate. Furthermore, the negative electrode layer, the positive electrode layer, and the separator film may be disposed in the electrolytic solution and may be disposed in a coin-type, cylindrical-type, square-type metal can, or a laminate exterior body. It may be sealed.

The lithium ion battery 31 may be an all solid battery, and the separator layer 35 may be a solid electrolyte layer. As a solid electrolyte contained in a solid electrolyte layer, a sulfide type solid electrolyte and an oxide type solid electrolyte can be used. As the sulfide-based solid electrolyte, glass-based sulfides (for example, Li ₂ S-P ₂ S ₅ , Li ₂ S-SiS ₂ -P ₂ S ₅ -LiI, etc.), algirodite-type sulfides (for example, Li ₇ PS) ₆ , Li ₆ PS ₅ Cl, Li ₆ PS ₅ Br, Li ₆ PS ₅ I, etc., thiolysicon based sulfides (eg, Li _4-x Ge _1-x P _x S ₄ (0 ≦ x ≦ 1 etc)) , Li ₇ P ₃ S ₁₁ , Li ₁₀ GeP ₂ S ₁₂ (LGPS), Li _9.54 Si _1.74 P _1.44 S _11.7 Cl _0.3 (LiSiPSCl), Li _9.6 P ₃ S ₁₂ And Li-Sn-Si-P-S (LSSPS), etc., and a perovskite-type lithium lanthanum niobate (Li _x La _{(1-x) / 3} NbO ₃ ) can be used as the oxide-based solid electrolyte. (0 _{_{x ≦ 1), Li 7 La}} 3 Zr 2 O 12 garnet-type _{_{_{_{oxide, Li 5 La 3 Nb 2 O}}}} 12 garnet-type _{_{_{_{oxide, Li 5 La 3 Ta 2 O}}}} 12 garnet-type oxide, garnet-type oxide _Li 6 _La ₂ BaTa 2 O ₁₂ of the object, lithium phosphate _(Li 3 _PO 4), lithium niobate _(LiNbO 3), _LAGP of NASICON structure _{_{(Li 1 + x Al x Ge}} 2-x (PO 4) 3 (0 ≦ It is possible to use x ≦ 1)), LATP with a NASICON structure (Li _{1 + x} Al _x Ti _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 1)), and the like.
In addition, you may use the dry polymer electrolyte layer which contains a lithium salt in a polymer as a solid electrolyte layer.

In addition, in the lithium ion battery 31 of the present invention, a current collector layer may be provided on the surfaces of the composite electrode 10 and the counter electrode layer 33. The current collector layer is provided to exchange electricity with the outside during charge and discharge in the all solid battery, and an electron conductive material, usually an electron conductive substance such as metal or carbon material itself, or an electron conductive substance. Are dispersed in a matrix of oxide or the like. As a metal constituting the current collector layer, at least one metal selected from the group consisting of nickel, copper, silver, gold and the like can be used. The current collector layer can be obtained by applying a metal paste and baking it in an atmosphere containing a reducing gas containing hydrogen and the like. In the present invention, if materials are appropriately selected, it is also possible to obtain an all-solid battery by collectively sintering all of the current collector layer, the composite electrode, the separator layer, and the counter electrode layer.

<Method of manufacturing composite electrode>
The method for producing a composite electrode of the present invention will be described with reference to FIG. First, in the laminating step, a layer containing the electrode active material or its precursor (hereinafter referred to as an electrode active material layer green sheet) and a layer containing a solid electrolyte or its precursor (hereinafter referred to as a solid electrolyte layer green sheet) And a green sheet laminate (also referred to as a precursor of a composite electrode because it becomes a composite electrode by sintering) is obtained. Thereafter, as shown in FIG. 4A, in the sintering step, the laminate is sintered to obtain a laminated sintered body 41. Furthermore, as shown in FIG. 4B, in the cutting step, the laminated sintered body 41 is cut out in a plane perpendicular to the plane direction of each layer, and the electrode active material layer 11 and the solid electrolyte layer 13 are alternately arranged in a flat plate. An arrayed sintered body is obtained. The arrayed sintered body can be used as the composite electrode 10.

The sintering step may be performed after the cutting step by replacing the sintering step and the cutting step. That is, a green sheet laminate is cut out in a plane perpendicular to the plane direction of each layer, and an electrode active material layer green sheet and a solid electrolyte layer green sheet are alternately arranged to obtain an array on a flat plate, and the array is fired A flat plate-like arrayed sintered body may be obtained by bonding.

The laminated sintered body 41 can also be used as a composite electrode without cutting, and can be used, for example, as the negative electrode band 103 or the positive electrode band 107 of the lithium ion battery 101 described later.

(On the precursor of the electrode active material and the solid electrolyte)
In addition, the precursor of an electrode active material or a solid electrolyte is a material which becomes an electrode active material or a solid electrolyte by heating, such as baking and sintering.

When lithium titanate is used as the electrode active material, the precursor of lithium titanate may be a compound containing lithium and titanium, or may be a mixture of a lithium source and a titanium source. As a lithium source, a halide, carbonate, hydroxide or the like of lithium can be used, and as a titanium source, an oxide, halide, carbonate, hydroxide or the like of titanium can be used. As described later, a precursor of lithium titanate can be obtained by solvothermal treatment of a mixture containing a lithium source, a titanium source and a solvent.

When using lithium lanthanum titanate as the solid electrolyte, the lithium lithium titanate precursor may be a compound containing lithium, titanium and lanthanum, or a mixture of a lithium source, a titanium source and a lanthanum source, It is also good. As a lithium source, a halide, carbonate, hydroxide or the like of lithium can be used, and as a titanium source, an oxide, halide, carbonate, hydroxide or the like of titanium can be used. As a lanthanum source, chlorides, oxychlorides, hydroxides, oxides, and nitrates of lanthanum can be used. As described later, a precursor of lithium lanthanum titanate can be obtained by solvothermal treatment of a mixture containing a lithium source, a titanium source, a lanthanum source and a solvent.

(Lamination process)
First, a paste containing an electrode active material or a precursor thereof and a paste containing a solid electrolyte or a precursor thereof are prepared. The paste may contain an organic binder such as acrylic resin, PVA (polyvinyl alcohol), PVB (polyvinyl butyral) and the like. The organic binder maintains the shape of the green sheet, is thermally decomposed by heating, and is removed from the sintered body. The specific surface area of the electrode active material or its precursor calculated by BET method using nitrogen adsorption is preferably 0.5 m ² / g or more, more preferably 1.2 m ² / g, and 13 m ² It is more preferable if it is / g or more. The specific surface area of the solid electrolyte or the precursor thereof is preferably 0.5 m ² / g or more, more preferably 3 m ² / g, and further preferably 15 m ² / g or more. Since the specific surface area tends to increase as the primary particle size decreases, the uniformity of the application process and the sintering process can be obtained by using an electrode active material having a large specific surface area or a precursor thereof, or a solid electrolyte or a precursor thereof. The sinterability can be enhanced, the width of the electrode active material layer or the solid electrolyte layer in the laminated sintered body can be reduced, and the porosity can be reduced.

In order to form a green sheet laminate, a paste containing an electrode active material or a precursor thereof is applied onto a substrate and dried to form an electrode active material green sheet, and a solid electrolyte or a precursor thereof is contained. A method of applying and drying the paste to form a solid electrolyte green sheet, peeling one or both of them and bonding them to the other, applying pressure and / or heat to bring them in close contact to obtain a green sheet laminate (crimping) There is a law).

Also, a paste containing an electrode active material or a precursor thereof is applied and dried on a substrate to form an electrode active material green sheet, and a paste containing a solid electrolyte or a precursor thereof is further applied and dried thereon. There is also a method (sequential coating method) in which a solid electrolyte green sheet is formed, the base material is peeled off, and then the binder is removed by heating to form a laminate.

(Sintering process)
Thereafter, the laminate of the electrode active material green sheet and the solid electrolyte green sheet is sintered to obtain a laminated sintered body in which the electrode active material layer and the solid electrolyte layer are laminated.

In the sintering step, the temperature is preferably 200 ° C. or more and 1300 ° C. or less, preferably 300 ° C. or more and 1250 ° C. or less, more preferably 400 ° C. or more and 1200 ° C. or less, and 500 ° C. or more and 1150 ° C. It is further preferable that the temperature is not higher than ° C. In order to prevent the side reaction of the electrode active material, heating at 1300 ° C. or less is more preferable, and heating at 500 ° C. or more is preferable in order to obtain a dense sintered body.

Further, as the atmosphere during sintering, any of an air atmosphere, an inert atmosphere such as nitrogen, a highly oxidizing atmosphere such as oxygen, and a reducing atmosphere such as hydrogen can be used. The environment may be a reduced pressure environment or a pressurized environment, for example, an environment in the range of 0.1 Pa to 1 MPa in absolute pressure, preferably 1 Pa to 500 kPa. The temperature holding time can be appropriately changed according to the temperature etc., but considering production efficiency etc, it is preferably 48 hours or less, more preferably 24 hours or less. The temperature holding time may be a short time of 1 hour or less, and further, the holding time may be 0 minutes and heating may be stopped immediately after reaching the target temperature. The cooling method is also not particularly limited, but may be natural cooling (cooling in a furnace) or may be cooled more rapidly than natural cooling, and a step of holding a predetermined temperature for a predetermined time during cooling You may provide.

In particular, when lithium lanthanum titanate is contained as the solid electrolyte, lithium lanthanum titanate crystal-grows at 700 ° C. or higher, and therefore the resistance of the solid electrolyte layer can be reduced by setting the sintering temperature to 800 ° C. or higher.

Moreover, when using lithium titanate as an electrode active material, spinel type lithium titanate can be obtained from the precursor of lithium titanate by setting sintering temperature to 400 degreeC or more and 1000 degrees C or less. Furthermore, by setting the sintering temperature to more than 1000 ° C., ramsdellite lithium titanate can be obtained from a precursor of lithium titanate.

When lithium titanate is used as the electrode active material and lithium lanthanum titanate is used as the solid electrolyte, sintering in the first stage is more than 1000 ° C., preferably 1100 ° C. or more and 1500 ° C. or less, more preferably 1150 ° C. or more and 1300 ° C. The spinel type lithium titanate can be obtained from the precursor of lithium titanate by carrying out the second stage sintering at 400 ° C. or more and 1000 ° C. or less, and the second stage of sintering is performed from the precursor of lithium lanthanum titanate, Perovskite-type lithium lanthanum titanate can be obtained. By adopting such a two-step sintering method, lithium lanthanum titanate can be a compact sintered body and the lithium ion conductivity can be enhanced by the step of heating at temperatures exceeding 1000 ° C. At that time, lithium titanate is of the ramsdellite type, and by subsequent sintering at 1000 ° C. or less, spinel type lithium titanate more suitable as an electrode active material can be obtained. In the second stage of sintering, the ramsdellite lithium titanate contained in the sintered body is maintained for 2 hours or more in a temperature range of 400 ° C. to 1000 ° C., preferably in a temperature range of 500 ° C. to 950 ° C. A phase change to spinel-type lithium titanate can be made by staying for 4 hours or more, more preferably for 8 hours or more in a temperature range of 600 ° C. to 900 ° C. By staying in a temperature range of 600 ° C. to 900 ° C. for 10 hours or more, preferably 15 hours or more, substantially single phase spinel lithium titanate can be obtained. After the first-stage sintering, the second-stage sintering may be performed during cooling, or may be heated to 400 ° C. or lower after returning to normal temperature to perform the second-stage sintering. The time of staying in the temperature range of 400 ° C. or more and 1000 ° C. or less during cooling or heating after the first stage sintering can also be included in the staying time in the second stage sintering.

In the step of sintering the green sheet laminate to obtain a laminated sintered body, lithium titanate and lithium lanthanum titanate are generated from the precursor of lithium titanate and the precursor of lithium lanthanum titanate by heating. Heating causes a change in the crystalline phase from the precursor and / or an improvement in crystallinity. The change in crystal phase and / or the improvement in crystallinity can be confirmed by powder X-ray diffraction. The change in crystal phase is reflected in the change in diffraction pattern, and the improvement in crystallinity is reflected in the X-ray diffraction pattern as the decrease in width of diffraction line. For example, (Li _1.81 , H _0.19 ) Ti ₂ O ₅ .2H ₂ O [ICDD No. 00-047-0123], Li _0.77 H _1.23 (Ti ₃ O ₇ ) present in the precursor ) The diffraction pattern which can be determined in 2H ₂ O [ICDD No. 00-040-0304], (Li ₂ TiO ₃ ) _1.333 [ICDD No. 01-075-0614] disappears by sintering, and the spinel type crystal structure Lithium titanate having a crystal such as Li ₄ Ti ₅ O ₁₂ (ICDD No. 00-049-0207), lithium titanate having a ramsdellite crystal structure such as Li ₂ Ti ₃ O ₇ (ICDD No. 00-034-0393) ], Li _0.94 Ti ₂ O ₄ [ICDD No. 01-088-0609], lithium titanate having a perovskite crystal structure Lanthanum, for example, Li _3x La _{2 / 3-x} TiO ₃ (0 <x ≦ 1/6) [ICDD Nos. 01-074-4217, 00-046-0467, 01-087-0935, 00-046-0466, etc.] Generates.

(Cutting process)
The laminated sintered body 41 is cut along a plane perpendicular to the plane direction of each layer to obtain a flat composite electrode 10. Here, a plane perpendicular to the plane direction of each layer means a plane perpendicular to the plane direction of each layer and an angle within ± 45 degrees.

Although the cutting method is not particularly limited, laser processing, electron beam processing, plasma processing, ultrasonic processing, gas cutting, diamond grinding, etc. can be used as a method capable of cutting a hard sintered body into a thin plate shape.

(Method of forming the metal layer 23)
In order to obtain the composite electrode 21 having the metal layer 23, the metal layer 23 needs to be laminated in the laminate. The metal layer 23 can be formed by coating / screen-printing a paste in which metal fine particles are dispersed, preparing a green sheet from the paste, and depositing metal under vacuum.

<Method of Producing Lithium Lanthanum Titanate Precursor>
It is preferable that a lithium lanthanum titanate precursor used when forming a solid electrolyte layer green sheet be obtained by solvothermal treatment of a mixture containing a Ti element source, a La element source, a Li element source, and a solvent.

As a method for producing a lithium lanthanum titanate precursor according to the present invention, an aqueous solution preparation step of preparing an aqueous solution containing La cation and Ti cation, and mixing the aqueous solution obtained in the aqueous solution preparation step with a basic aqueous solution A coprecipitation step of obtaining a precipitate containing an oxide and / or hydroxide of La element and an oxide and / or hydroxide of Ti element, and the precipitate obtained in the coprecipitation step. Forming a solid substance by a solvothermal treatment method of a mixture containing a compound of Li element source and a solvent, and a method of producing a precursor.

Aqueous solution preparation process
In the aqueous solution preparation step, an aqueous solution containing La cation and Ti cation is prepared. Examples of the La cation include La ³⁺ , and examples of the Ti cation include Ti ⁴⁺ . Each of the La cation and the Ti cation may form a complex using water, ammonia, an oxide ion, a hydroxide ion, a counter anion described later, or the like as a ligand. As a counter anion of La cation and Ti cation, in addition to oxide ion and hydroxide ion, for example, chlorine-containing anion such as chloride ion, nitrate anion and the like can be mentioned. The above counter anions may be used alone or in combination of two or more.

The aqueous solution is prepared, for example, by dissolving a lanthanum compound that generates La cation by dissolution and a titanium compound that generates Ti cation by dissolution in water or an acidic aqueous solution. As these lanthanum compounds and titanium compounds, for example, chlorides, oxychlorides, hydroxides, oxides, nitrates and the like can be mentioned, and chlorides or oxychlorides are preferred because they are easy to obtain and inexpensive. Is preferred. In addition, nitrate is preferable from the viewpoint of easy dissolution. It does not specifically limit as a form of said lanthanum compound and a titanium compound, For example, liquids, such as solid, such as a powder, aqueous solution, etc. are mentioned. Each of the above-mentioned lanthanum compound and titanium compound may be used alone or in combination of two or more.

The aqueous solution prepared in the aqueous solution preparation step preferably has a pH of less than 7, ie, acidic. La cation exhibits high aqueous solution in the strongly acidic to weakly acidic region, but Ti cation exhibits high water solubility only in the strongly acidic region. Therefore, from the viewpoint of stability, the aqueous solution prepared in the aqueous solution preparation step is preferably strongly acidic (for example, pH 3 or less).

Simultaneous precipitation process
In the coprecipitation process step, precipitation comprising an oxide and / or hydroxide of lanthanum and an oxide and / or hydroxide of titanium by mixing the aqueous solution obtained in the aqueous solution preparation step with a basic aqueous solution. Get things. The method for mixing the aqueous solution obtained in the aqueous solution preparation step and the basic aqueous solution is not particularly limited, and examples thereof include a method in which the aqueous solution obtained in the aqueous solution preparation step is dropped or sprayed onto the basic aqueous solution.

The pH of the basic aqueous solution is preferably 8 or more from the viewpoint of the precipitation rate. The basic aqueous solution is not particularly limited, and examples thereof include aqueous ammonia and an aqueous lithium hydroxide solution. Ammonia water is preferred in terms of availability and low cost. Further, from the viewpoint of preventing contamination to the solid electrolyte, an aqueous lithium hydroxide solution in which the alkali cation is a lithium ion, that is, a cation constituting the solid electrolyte is preferable.

The molar equivalent of the base of the basic aqueous solution used in the simultaneous precipitation process step is the molar equivalent of the counter anion of the La cation and Ti cation in the aqueous solution obtained in the aqueous solution preparation process (excluding oxide ion and hydroxide ion) More is preferable, and a large excess (for example, about twice or more) is more preferable. When the molar equivalent of the base of the basic aqueous solution is larger than the molar equivalent of the above counter anion, the basicity of the mixed solution can be sufficiently maintained even after the aqueous solution obtained in the aqueous solution preparation step and the basic aqueous solution are mixed.

The precipitate obtained in the coprecipitation process step is separated and washed as appropriate. The separation method is not particularly limited, and examples thereof include centrifugation, decantation, and filtration. The solvent used for washing is not particularly limited, and water is preferably exemplified from the viewpoint of easy availability and low cost.

In the aqueous solution preparation process according to the present invention, inexpensive raw materials such as chlorides can be used instead of expensive alkoxides used in the sol-gel method. In addition, the precipitate obtained in the simultaneous precipitation treatment step can prevent a large mass loss caused by the detachment of the organic ligand at the time of sintering, which is generated by the sol-gel method.

[Solvo-thermal processing process]
In the solvothermal treatment step, the pressure is higher than atmospheric pressure by mixing a solid or solution containing La cation and Ti cation such as precipitates obtained in the simultaneous precipitation treatment step, a compound of lithium element source, and a solvent Heat under to obtain a precursor.

The compound of the lithium element source is not particularly limited, and examples thereof include lithium carbonate, lithium chloride, lithium fluoride, lithium hydroxide, lithium nitrate, lithium acetate, and hydrates of these. These lithium compounds may be used alone or in combination of two or more. Further, the form of the lithium compound may be, for example, a solid such as a powder or an aqueous solution, and is not particularly limited.

It is preferable that the content ratio of La element to Ti element in the mixture before the solvothermal treatment process be La / Ti ≦ 0.66. In the case of La / Ti ≦ 0.66, La (OH) ₃ other than LTO or LLTO is difficult to be retained by firing because more La than the electrode complex containing the lithium lanthanum titanate having the target composition requires is difficult to remain after firing. It is difficult to form an impurity phase such as La ₂ O ₃ or La ₂ Ti ₂ O ₇ .

In the present invention, as solvothermal treatment, hydrothermal treatment using water as a solvent is mainly performed. The hydrothermal treatment refers to a compound synthesis method or a crystal growth method performed in the presence of high temperature and high pressure hot water, and a chemical reaction which does not occur in an aqueous solution at normal temperature and pressure may progress. In the present invention, an aqueous solution containing a lithium element is added to a solid or solution containing a La cation and a Ti cation, and a high temperature and high pressure treatment is performed to obtain a lithium element which is water soluble at normal temperature and pressure. Complex chloride can be incorporated into the complex salt, and the complex salt is separated from the solvent to obtain a precursor. In addition, although water is used as a solvent in the hydrothermal treatment, the same effect can be expected also by a method (solvothermal method) using a solvent other than water (for example, an organic solvent etc.).

In the hydrothermal treatment of the present invention, preferably, the absolute pressure is higher than atmospheric pressure and lower than 8.7 MPa, and the temperature is 60 ° C. or more and 300 ° C. or less, more preferably, the absolute pressure is 0.15 MPa or more. It is preferable to heat at about 0 MPa or less and at a temperature of 60 ° C. to 250 ° C. for about 1 hour to 100 hours. If the pressure and temperature are in the above ranges, the reaction is likely to proceed, impurities are less likely to be generated, and a high-pressure pressure container is not required, which is less likely to cause an increase in manufacturing cost. Moreover, productivity is hard to fall that reaction time is in the said range.

An acid may be further added to the hydrothermally treated body obtained in the solvothermal treatment step to carry out the second solvothermal treatment step. In that case, the solvothermal treatment step is a first solvothermal treatment step. As the acid, both inorganic acids and organic acids can be used, and hydrochloric acid, nitric acid, sulfuric acid, formic acid, acetic acid and the like can be used.

As the addition amount of the acid, the difference from the molar ratio (Li / Ti) of lithium to titanium in the molar ratio of acid to titanium (acid / Ti) is 0.1 <[(Li / Ti)-(acid / Ti) It is preferable to satisfy | fill <1.5, It is still more preferable to satisfy | fill 0.3 <[(Li / Ti)-(acid / Ti)] <1.1. Moreover, it is preferable that pH of the solution after addition of an acid is 8 or more and 14 or less. By adjusting the addition amount of the acid, the amount of lithium contained in the solid after the second solvothermal treatment can be adjusted to a preferable range.

Alternatively, the La element source may be added together with the acid when performing the second solvothermal treatment without adding it in the first aqueous solution preparation step.

In the precursor production method described above, the solvothermal treatment is performed on the precipitate obtained by the simultaneous precipitation method, but the single salt of Ti element and the single element of La element obtained by other than the simultaneous precipitation method. The solvothermal treatment may be performed on a mixture containing a salt, a simple salt of Li element and a solvent.

It does not specifically limit as a simple salt of La element, The oxide and / or hydroxide of lanthanum are mentioned. It does not specifically limit as a monosalt of Ti element, The oxide and / or hydroxide of titanium are mentioned. The monosalt of Li element is not particularly limited, and examples thereof include lithium carbonate, lithium chloride, lithium fluoride, lithium hydroxide, lithium nitrate, lithium acetate, and hydrates of these.

The average particle diameter of the Ti single salt is preferably 100 nm or less, more preferably 50 nm or less, and particularly preferably 30 nm or less. If the particles of the Ti single salt are in the above range, complex chloride of Li and Ti is likely to progress during the solvothermal treatment.

<Method of Producing Lithium Titanate Precursor>
The precursor of lithium titanate used when forming the electrode active material layer green sheet can be obtained by not using the La element source in the process of manufacturing the above-mentioned lithium lanthanum titanate precursor.

[Drying process]
Thereafter, the precursor obtained in the solvothermal treatment step may be dried. As conditions of a drying process, 60 degreeC or more and 250 degrees C or less, 1 hour or more and 10 hours or less are mentioned, for example.

[Temporary firing process]
In addition, although the precursor obtained in the solvothermal treatment step may be used as it is as a green sheet, it is possible to use as a green sheet temporary calcinated particles obtained by temporarily calcining a lithium titanate precursor and a lithium lanthanum titanate precursor. preferable. By performing the pre-firing step before the sintering step, it is possible to alleviate the gas generation and the weight reduction of the compact in the sintering step.

In the pre-baking step, the lithium titanate or the lithium titanate precursor is preferably heated at 250 ° C. or more and 1500 ° C. or less, more preferably 400 ° C. or more and 1300 ° C. or less, to form lithium titanate or lithium titanate or The precursor or lithium lanthanum titanate or a precursor thereof is produced. Pre-baking may be performed at a lower temperature to produce only lithium titanate, and lithium lanthanum titanate may not be produced, or pre-baking may be performed at a higher temperature to produce both lithium titanate and lithium lanthanum titanate. You may

(Another form of lithium ion battery)
In the method of manufacturing the lithium ion battery 31 described above, the laminate of the electrode active material layer and the solid electrolyte layer before or after sintering is cut to obtain the composite electrode 10, and then the separator layer 35 and the counter electrode layer 33 are obtained. The lithium ion battery can also be obtained by forming the composite electrode, the separator, and the counter electrode adjacent to each other without performing the cutting step.

The lithium ion battery 101 of the present invention will be described. As shown in FIG. 7, the current collector 109, the negative electrode band 103, the separator band 105, the positive electrode band 107, and the current collector 111 are adjacent in this order. The negative electrode band 103 is composed of negative electrode active material sheets 113a to 113d and solid electrolyte sheets 123a to 123c stacked alternately. All these layers (all seven layers depicted in FIG. 7) constitute a composite electrode and act as one negative electrode. Similarly, the positive electrode band 107 is composed of positive electrode active material sheets 117a to 117d and solid electrolyte sheets 127a to 127c alternately stacked, and all of these layers constitute a composite electrode and function as one positive electrode. The negative electrode band 103 and the positive electrode band 107 correspond to the composite electrode 10 of the present invention. The current collectors 109a to 109g and the current collectors 111a to 111g are stacked, respectively, to form

current collectors

109 and 111. The separator sheets 115a to 115g are stacked to form one separator band 105.

By sandwiching the solid electrolyte sheets 123a to 123c between the negative electrode active material sheets 113a to 113d, a lithium ion conduction path to the negative electrode active material of the negative electrode active material sheet can be provided. Similarly, for the positive electrode active material sheets 117a to 117d, lithium ion conductive paths to the positive electrode active material in the positive electrode active material sheet can be provided by the solid electrolyte sheets 127a to 127c. Although the outermost layer of the negative electrode band 103 is the negative electrode active material sheet 113a and the negative electrode active material sheet 113d in FIG. 7, the outermost layer is not limited to the negative electrode active material sheet, and the solid electrolyte sheet is the outermost surface. It may be a layer of Similarly for the positive electrode zone 107, the solid electrolyte sheet may be the outermost layer.

The same material as the above-described electrode active material layer 11 can be used for the negative electrode active material sheets 113a to 113d or the positive electrode active material sheets 117a to 117d. Note that although the negative electrode active material and the positive electrode active material may use the same material, they are generally different materials. For example, when using spinel type or ramsdellite type lithium titanate as the negative electrode active material of the negative electrode zone 103, a known oxide-based positive electrode active material such as lithium transition metal oxide is used as the positive electrode active material of the positive electrode zone 107. It can be used.

In lithium ion battery 101, both negative electrode band 103 and positive electrode band 107 have solid electrolyte sheets 123a-c or 127a-c, but they necessarily have solid electrolyte sheets in both negative electrode band and positive electrode band. It may not be necessary, and only the negative electrode band or the positive electrode band may have the solid electrolyte sheet. For example, when the solid electrolyte sheet is provided only in the negative electrode zone and not in the positive electrode zone, the negative electrode zone corresponds to the electrode complex of the present invention, and the positive electrode zone does not correspond to the electrode composite of the present invention. On the contrary, it is not necessary to have a solid electrolyte sheet only in the positive electrode zone, and not to have a solid electrolyte sheet in the negative electrode zone.

The same material as the solid electrolyte layer 13 described above can be used for the solid electrolyte sheets 123a to 123c. In addition, the solid electrolyte sheets 123a to 123c and 127a to 127c may be the same material or different materials.

The separator sheets 115a to 115g can use the same material as the separator layer 35 described above, but are preferably formed of a sulfide-based or oxide-based solid electrolyte. The separator sheets 115a to 115g may be the same material as or different from the solid electrolyte sheets 123a to 123c.

For the current collectors 109a to 109g and the current collectors 111a to 111g, the same materials as the above-described current collector layers can be used.

The thickness D of the negative electrode active material sheets 113 a to 113 d and the thickness D of the positive electrode active material sheets 117 a to 117 d are in the same numerical range as the width B of the electrode active material layer 11.

The thickness E of the solid electrolyte sheets 123 a-c and 127 a-c is in the same numerical range as the width A of the solid electrolyte layer 13.

The width F of the negative electrode band 103 and the width H of the positive electrode band 107 are in the same numerical range as the thickness C of the composite electrode 10. The width F and the width H may or may not be the same value.

In the negative electrode band 103, it is preferable to combine 100 or more layers of the negative electrode active material sheet 113 and the solid electrolyte sheet 123, preferably 500 or more layers, and more preferably 1000 or more layers. Is particularly preferred. The same applies to the positive electrode band 107.

The width G of the separator band 105 is preferably 1 μm to 300 μm, more preferably 5 μm to 100 μm, and particularly preferably 10 μm to 30 μm. The width G is preferably as small as possible as long as short circuit or dielectric breakdown does not occur, but there is a problem of dimensional accuracy in printing process, lamination process and sintering process at the time of production. difficult.

It is preferable that the width I of the current collector 109 and the width J of the current collector 111 be as small as possible so long as electrons can be smoothly exchanged with the negative electrode band or the positive electrode band. The width I and the width J may be the same or different. The current collector is required to be a material which is located between the external terminal and the negative electrode zone or the positive electrode zone to facilitate the movement of electrons and which does not cause lithium ion exchange between the negative electrode zone or the positive electrode zone. If the conditions are satisfied, the current collector may be omitted and the negative electrode band or the positive electrode band may be brought into direct contact with the external terminal, or may be substituted by a coating of an electron conductive material prepared by vapor deposition or coating after sintering. It is good.

If this embodiment is used, it is possible to make the thickness E of the solid electrolyte sheets 123 and 127 smaller than the width G of the separator band 105 which is restricted by the dimensional accuracy of the printing process, the laminating process and the sintering process in manufacturing. become.

(How to make a battery)
The method of producing the lithium ion battery 101 of the present invention will be described with reference to FIGS. 8 (a) to 8 (d). First, as shown in FIG. 8A, the current collector 109a, the negative electrode active material green sheet 133a, the separator green sheet 135a, the positive electrode active material green sheet 137a, and the current collector 111a are formed to be adjacent in this order. .

The negative electrode active material green sheet 133a is obtained by forming a paste containing the negative electrode active material or a precursor thereof into a predetermined shape and drying it. The separator green sheet 135a is obtained using a paste containing a solid electrolyte or a precursor thereof, and the positive electrode active material green sheet 137a is obtained using a paste containing a positive electrode active material or a precursor thereof. The specific surface area of the negative electrode active material or the precursor thereof or the positive electrode active material or the precursor thereof calculated by BET method using nitrogen adsorption is preferably 0.5 m ² / g or more, and 1.2 m ² / g Is more preferably 13 m ² / g or more. The specific surface area of the solid electrolyte or the precursor thereof is preferably 0.5 m ² / g or more, more preferably 3 m ² / g, and still more preferably 15 m ² / g or more. Since the specific surface area tends to increase as the primary particle size decreases, the uniformity of the application process and the sintering process can be obtained by using an electrode active material having a large specific surface area or a precursor thereof, or a solid electrolyte or a precursor thereof. The sinterability can be enhanced, the width of the electrode active material layer or the solid electrolyte layer in the laminated sintered body can be reduced, and the porosity can be reduced.

As an example of the formation method of such a structure, the method of forming the paste of each material by printing is mentioned. As a printing method, an inkjet method of discharging the paste to a predetermined position, an intaglio printing method of transferring the paste into the concave portion of the plate and transferring, a relief printing method of adhering the paste onto the convex portion of the plate and transferring, A lithographic printing method in which a portion with different affinity to the paste is made and the paste is attached to the affinity portion for transfer, a large open portion of fine holes is made in the plate, and the paste passed through the holes under pressure is transferred And the like.

Thereafter, as shown in FIG. 8B, the current collector 109b is on the current collector 109a, the solid electrolyte green sheet 143a is on the negative electrode active material green sheet 133a, and the separator green is on the separator green sheet 135a. The sheet 135b is formed on the positive electrode active material green sheet 137a, the solid electrolyte green sheet 147a is formed, and the current collector 111b is formed on the current collector 111a.

Thereafter, as shown in FIG. 8C, the current collector 109b is on the current collector 109b, the negative electrode active material green sheet 133b is on the solid electrolyte green sheet 143a, and the separator green is on the separator green sheet 135b. The positive electrode active material green sheet 137b is formed on the solid electrolyte green sheet 147a, and the current collector 111c is formed on the current collector 111b.

Thereafter, as shown in FIG. 8D, the current collector 109c is on the current collector 109c, the solid electrolyte sheet 143b is on the negative electrode active material green sheet 133b, and the separator green sheet is on the separator green sheet 135c. The sheet 135d is formed on the positive electrode active material green sheet 137b, and the solid electrolyte green sheet 147b is formed, and the current collector 111d is formed on the current collector 111c. These steps are repeated a predetermined number of times to form a green sheet laminate. In addition, as a method of repeating these processes, a method of printing in multilayers may be used, or a method may be used in which a green sheet formed on a release film is peeled off, aligned and placed, and pressure-bonded. The process shown in FIG. 8A is omitted, and in FIG. 8B, the current collector 109a, the negative electrode active material green sheet 133a, and the separator green sheet 135a formed in the process shown in FIG. 8A. The current collector 109b, the solid electrolyte green sheet 143a, the separator green sheet 135b, the solid electrolyte green sheet 147a, and the current collector 111b are formed to be adjacent to each other in this order without the positive electrode active material green sheet 137a and the current collector 111a. May be In addition, the formation of the laminate, which is performed by repeating the above steps a predetermined number of times, may be completed by any of the step shown in FIG. 8C and the step shown in FIG.

Thereafter, the laminate of the green sheets is sintered to make the negative electrode active material green sheet the negative electrode active material sheet, the positive electrode active material green sheet the positive electrode active material sheet, the separator green sheet the separator sheet, and the solid electrolyte green sheet Thus, the lithium ion battery 101 can be obtained as a solid electrolyte sheet.

In addition, when a precursor is not used, the lithium ion battery 101 can also be obtained without performing a sintering process. That is, a negative electrode active material sheet 113a containing a negative electrode active material, a separator sheet 115a containing a solid electrolyte, and a positive electrode active material sheet 117a containing a positive electrode active material are formed adjacent to each other, and a solid electrolyte sheet 123a containing a solid electrolyte is formed thereon. Forming the separator sheet 115b and the solid electrolyte sheet 127a containing the solid electrolyte is a process repeated. Alternatively, the step of repeating may be solid, instead of starting from forming the negative electrode active material sheet 113a containing a negative electrode active material, the separator sheet 115a containing a solid electrolyte, and the positive electrode active material sheet 117a containing a positive electrode active material. It may start from adjacently forming a solid electrolyte sheet 123a containing an electrolyte, a separator sheet 115b, and a solid electrolyte sheet 127a containing a solid electrolyte. Moreover, the process to repeat may be completed by forming the negative electrode active material sheet, the separator sheet, and the positive electrode active material sheet adjacent to each other, or forming the solid electrolyte sheet, the separator sheet, and the solid electrolyte sheet adjacent to each other. You may end with

(Series connected batteries)
If a plurality of lithium ion batteries 101 are used and the positive electrode band of one battery is electrically connected to the negative electrode band of another battery, a battery assembly in series connection can be obtained. For example, as shown in FIG. 9, a current collector 109, a negative electrode band 103a, a separator band 105a, a positive electrode band 107a, an electrode band 153, a negative electrode band 103b, a separator band 105b, and a positive electrode band 107b. A battery assembly 151 in series connection in which the current collectors 111 are adjacent in this order is obtained. Although the battery pack 151 connects two lithium ion batteries 101 in series, more lithium ion batteries 101 can be connected in series.

Since the electrode band 153 can be similarly made of the same material as the

current collectors

109 and 111, the battery assembly 151 is also formed by laminating the respective layers as shown in FIGS. 8 (a) to 8 (d). You can get it.

The width of the electrode band 153 is preferably as small as possible so long as electrons are sufficiently conducted and short-circuiting or dielectric breakdown of lithium ions does not occur. However, the dimensional accuracy of the printing process, the lamination process, and the sintering process at the time of manufacturing And it is difficult to make it less than 10 μm. Practically, the thickness is preferably 10 μm to 300 μm, more preferably 10 μm to 100 μm, and particularly preferably 10 μm to 30 μm.

(Parallel connected battery pack)
If a plurality of lithium ion batteries 101 are used to electrically connect the positive electrode bands or the negative electrode bands of the plurality of batteries, a battery assembly in parallel connection can be obtained. For example, as shown in FIG. 10, the current collector 163, the negative electrode band 103a, the separator band 105a, the positive electrode band 107a, the current collector 165, the positive electrode band 107b, the separator band 105b, and the negative electrode band 103b The current collector 167 is adjacent in this order, and a battery assembly 161 in parallel connection in which the current collector 165 and the current collector 167 are connected by the connection portion 169 is obtained.

Note that the insulator 171 is preferably filled between the connection portion 169 and the negative electrode band 103 a and the like so as not to cause a short circuit without the current collector 163 and the like. In FIG. 10, the insulator 171 is drawn transparent. Although a known insulating material can be used as the insulator 171, a metal oxide-based insulating material such as alumina, silica, or titania is used in order to obtain a sintered body together with the lithium ion battery 101. It is preferable to do.

Although FIG. 10 shows a structure in which the positive electrode band 107a and the positive electrode band 107b are inside, the positions of the positive electrode band and the negative electrode band may be interchanged and the

negative electrode bands

103a and 103b may be inside.

Since the

current collectors

163, 165, 167, and the connection portion 169 can be similarly made of the same material as the current collector 109, the assembled battery 161 is also as shown in FIGS. 8 (a) to 8 (d). Can be obtained by a method of laminating each layer.

Moreover, although the assembled battery 161 connects two lithium ion batteries 101 in parallel, more lithium ion batteries 101 can be connected in parallel. FIG. 11 shows a battery assembly 181 in which three lithium ion batteries 101 are connected in parallel. The

positive electrode bands

107 a and 107 b are electrically connected to the positive electrode band 107 c through the current collector 165, the connection portion 185, and the current collector 183. The negative electrode band 103a is electrically connected to the

negative electrode bands

103b and 103c through the current collector 163, the connection portion 169, and the current collector 167. In FIG. 11, the

insulators

171, 173, 175, and 177 are drawn transparent.

The widths of the current collectors 165 and the current collectors 167 can be determined in consideration of the dimensional accuracy problems of the printing process, the lamination process, and the sintering process at the time of manufacturing as in the case of the electrode band 153. Unlike in the case of the band 153, there is no need to consider the problem of lithium ion short circuiting or dielectric breakdown, and if the positive or negative band has sufficient electron conductivity, the portion in the positive or negative band is You may omit it.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited by the examples.

Example 1
[Preparation of lithium titanate (LTO) calcined particles]
FIG. 12 shows a flow of preparation of lithium titanate (LTO) calcined particles.
(Coprecipitation process)
An aqueous solution of titanium tetrachloride aqueous solution, Ti concentration 3.45 mmol / g, and Cl concentration 13.79 mmol / g was prepared. The aqueous solution was clear and did not form a precipitate upon standing at room temperature. When 1203 g of this aqueous solution was sprayed into 2000 g of 28 mass% ammonia water, a precipitate was formed. The precipitate is separated off, washed with water, dried at 200 ° C. and mechanically disintegrated.

(First solvothermal treatment process)
38.9 g of the above precipitate was placed in a pressure resistant vessel, and 219.32 mL of a 4 N aqueous solution of lithium hydroxide (equivalent to 0.88 mol of lithium hydroxide) was added. The above-mentioned pressure-resistant container was sealed, heated in a constant temperature bath set at 120 ° C. for 12 hours, subjected to hydrothermal treatment, and allowed to cool.

(2nd solvothermal treatment process)
The contents of the pressure resistant vessel subjected to the first solvothermal treatment were stirred, and 0.526 mol of acetic acid was added. Thereafter, the pressure-resistant container was sealed, and was heated in a constant temperature bath set at 180 ° C. for 12 hours to conduct hydrothermal treatment. After natural cooling, the precipitate was separated, washed with water, and dried at 200 ° C. to obtain a solid hydrothermally treated body (LTO precursor).

(Pre-baking treatment process)
The hydrothermally treated body obtained in the above step was placed in a firing boat made of alumina, and fired in air at 500 ° C. for 10 hours to obtain lithium titanate (LTO) calcined particles. The specific surface area of the calcined body calculated by the BET method using nitrogen adsorption was 14.8 m ² / g.

[Preparation of lithium lanthanum titanate (LLTO) calcined particles]
FIG. 13 shows a flow of preparation of lithium lanthanum titanate (LLTO) calcined particles.
(Coprecipitation process)
A solution obtained by dissolving lanthanum chloride heptahydrate in water is mixed with an aqueous solution of titanium tetrachloride, and an aqueous solution containing 0.96 mmol / g of La, 1.71 mmol / g of Ti, and 6.84 mmol / g of Cl is prepared. Prepared. The aqueous solution was clear and did not form a precipitate upon standing at room temperature. When 412 g of this aqueous solution was sprayed into 500 g of 28% by mass ammonia water, a precipitate was formed. The precipitate is separated off, washed with water, dried at 200 ° C. and mechanically disintegrated.

(First solvothermal treatment process)
38.4 g of the above precipitate was placed in a pressure resistant vessel, and 104.31 mL of a 4 N lithium hydroxide aqueous solution (equivalent to 0.41 mol of lithium hydroxide) was added. The above-mentioned pressure-resistant container was sealed, heated in a constant temperature bath set at 120 ° C. for 12 hours, subjected to hydrothermal treatment, and allowed to cool.

(2nd solvothermal treatment process)
The contents of the pressure resistant container subjected to the first solvothermal treatment were stirred, and 0.350 mol of acetic acid was added. Thereafter, the pressure-resistant container was sealed, and was heated in a constant temperature bath set at 180 ° C. for 12 hours to conduct hydrothermal treatment. After natural cooling, the precipitate was separated, washed with water, and dried at 200 ° C. to obtain a solid hydrothermally treated body (LLTO precursor).

(Pre-baking treatment process)
The hydrothermally treated body obtained in the above step was placed in a firing boat made of alumina, and fired in air at 700 ° C. for 10 hours to obtain lithium lanthanum titanate (LLTO) calcined particles. The specific surface area of the calcined body calculated by the BET method using nitrogen adsorption was 19.3 m ² / g.

[Preparation of lithium titanate layer and lithium lanthanum titanate layer green sheet]
FIG. 14 shows a flow from pre-sintered sintered body particles to preparation of arrayed sintered bodies.
(Paste preparation process)
Polyvinyl butyral was dissolved in a mixed solvent of toluene and 2-propanol to prepare a binder solution. Each paste was prepared by adding the above-mentioned lithium titanate (LTO) calcined particles or lithium lanthanum titanate (LLTO) calcined particles to the binder solution and kneading.

(Coating process)
The obtained layer paste was applied onto a polyethylene terephthalate (PET) film by a doctor blade method, and dried at 120 ° C. for 10 minutes to prepare a layer green sheet.

[Production of green sheet laminate]
The lithium titanate layer green sheet and the lithium lanthanum titanate layer green sheet produced by the above method were cut into a disk shape having a diameter of 12 mm. Each layer green sheet obtained by cutting and peeling the PET film was alternately stacked, and both ends were made to be a lithium titanate layer green sheet. The lithium titanate layer green sheets at both ends are held between peeled PET films, and after thermocompression bonding with a thermocompression bonding device at 80 ° C. for 30 minutes, the PET films of the uppermost layer and the lowermost layer are peeled off to obtain lithium titanate-titanate A lithium lanthanum laminate was prepared. 51 sheets of lithium titanate layer green sheets and 50 sheets of lithium lanthanum titanate layer green sheets were used.

[Fabrication of laminated sintered body (sintering process)]
By sandwiching the green sheet laminate prepared by the above method with an alumina plate and removing polyvinyl butyral by prebaking in the atmosphere at 500 ° C. for 10 hours, the main firing is carried out in the air atmosphere at 950 ° C. for 12 hours. A laminated sintered body was produced.

[Evaluation of laminated sintered body]
It was confirmed that the layers of the laminated sintered body produced by the above method were in close contact, and an integrated laminate was obtained. When a part of the laminated sintered body was crushed and powder X-ray diffraction measurement was performed, Li ₄ Ti ₅ O ₁₂ (LTO), which is a lithium titanate having a spinel type crystal structure [ICDD No. 00-049-0207] Diffraction lines were detected which were determined relative to lithium lanthanum titanate (LLTO) having a perovskite crystal structure [ICDD No. 01-087-0935] (FIG. 15). Since no side reaction product was confirmed by powder X-ray diffraction, it can be seen that no side reaction product is contained at the interface between the lithium titanate layer and the lithium lanthanum titanate layer.
In addition, as a result of observing a cross section with an electron microscope, two layers were arranged regularly. When a lithium titanate layer and a lithium lanthanum titanate layer form one set, the average width of a total of 5 or more sets of layers is measured along a straight line perpendicular to these layers and divided by the number of sets. The width was 9.0 μm. Further, when the area ratio was determined from the cross-sectional photograph, LTO: LLTO was 1.45: 1. Therefore, the average value of the width of each layer was 5.3 μm for lithium titanate and 3.7 μm for lithium lanthanum titanate (FIG. 16).
In addition, the volume ratio of lithium titanate and lithium lanthanum titanate contained in the laminated sintered body calculated from the preparation ratio was LTO: LLTO = 65: 35.

[Preparation of arrayed sintered body]
The laminated sintered body produced by the above method was cut out and processed using a grinder to produce a sintered body in which a lithium titanate layer and a lithium lanthanum titanate layer were arranged. The thickness of the sintered body (that is, the thickness C of the composite electrode) was measured with a caliper and found to be 400 μm. Further, the actual density of the arrayed sintered body calculated by the dimension method is 2.53 g / cm ³ , the relative density is 61%, the porosity is 39%, and the arrayed sintered body calculated by the Archimedes method The actual density was 3.05 g / cm ³ , the relative density was 73%, and the porosity was 27%. The width X of the cut out array sintered body was 400 μm, and the depth Y was 4 mm. The thickness C / width B was about 75, and the thickness C / width A was about 108.

Example 2
A laminated sintered body was produced in the same manner as in Example 1 except that the main sintering for producing the laminated sintered body in Example 1 was changed to 1150 ° C. for 5 hours and then to 850 ° C. for 12 hours.

[Evaluation of laminated sintered body]
It was confirmed that the layers of the laminated sintered body produced by the above method were in close contact, and an integrated laminate was obtained. When a part of the laminated sintered body was crushed and powder X-ray diffraction measurement was performed, Li ₄ Ti ₅ O ₁₂ (LTO), which is a lithium titanate having a spinel type crystal structure [ICDD No. 00-049-0207] Diffraction lines were detected which were determined relative to lithium lanthanum titanate (LLTO) having a perovskite crystal structure [ICDD No. 01-087-0935] (FIG. 17).
In addition, as a result of observing a cross section with an electron microscope, two layers are arranged regularly, and as a result of evaluating by the same method as Example 1, the average value of the width of each layer is 6.4 μm for lithium titanate, titanium The lithium acid lithium was 3.2 μm (FIG. 18).
Moreover, the volume ratio of lithium titanate and lithium lanthanum titanate contained in the laminated sintered body calculated from the preparation ratio was LTO: LLTO = 67: 33.

[Preparation of arrayed sintered body]
The laminated sintered body produced by the above method was cut out and processed using a grinder to produce a sintered body (400 μm in thickness) in which a lithium titanate layer and a lithium lanthanum titanate layer were arranged. The actual density of the arrayed sintered body calculated by the dimension method is 2.97 g / cm ³ , the relative density is 72%, the porosity is 28%, and the arrayed sintered body calculated by the Archimedes method The actual density was 3.38 g / cm ³ , the relative density was 81%, and the porosity was 19%.

[Example 3]
A laminated sintered body was produced in the same manner as in Example 1 except that the main sintering for producing the sintered body in Example 1 was changed to 1150 ° C. for 5 hours.

[Evaluation of laminated sintered body]
It was confirmed that the layers of the laminated sintered body produced by the above method were in close contact, and an integrated laminate was obtained. When a part of the laminated sintered body was crushed and powder X-ray diffraction measurement was performed, Li ₂ Ti ₃ O ₇ [ICDD No. 00-034-0393], a lithium titanate having a ramsdellite crystal structure, perovskite A diffraction line specific to lithium lanthanum titanate (LLTO) [ICDD No. 01-087-0935] having a crystal structure of the crystal structure was detected (FIG. 19).
In addition, as a result of observing a cross section with an electron microscope, two layers are arranged regularly, As a result of evaluating by the same method as Example 1, the width of an average of each layer is 4.3 micrometers of lithium titanate, lithium titanate The lantern was 2.1 μm (FIG. 20).
Further, the volume ratio of lithium titanate and lithium lanthanum titanate contained in the laminated sintered body calculated from the feed ratio was lithium titanate: LLTO = 68: 32.

[Preparation of arrayed sintered body]
The laminated sintered body produced by the above method was cut out and processed using a grinder to produce a sintered body (400 μm in thickness) in which a lithium titanate layer and a lithium lanthanum titanate layer were arranged. Further, the actual density of the arrayed sintered body calculated by the dimension method is 2.94 g / cm ³ , the relative density is 74%, the porosity is 24%, and the arrayed sintered body calculated by the Archimedes method The actual density was 3.15 g / cm ³ , the relative density was 79%, and the porosity was 21%.

Example 4
[Production of green sheet laminate]
The lithium titanate layer green sheet and the lithium lanthanum titanate layer green sheet produced in Example 1 were cut into a disk shape having a diameter of 12 mm. Each layer green sheet obtained by cutting and peeling the PET film was alternately stacked, and both ends were made to be a lithium titanate layer green sheet. The lithium titanate layer green sheets at both ends were sandwiched by the peeled PET film, and thermocompression bonding was performed at 80 ° C. for 10 minutes using a thermocompression bonding apparatus. As a thermocompression-bonded body, 11 sheets of lithium titanate layer green sheets and 10 sheets of lithium lanthanum titanate layer green sheets were used.

Gold is vapor-deposited on one side of the obtained thermocompression-bonded body, five gold-deposited thermocompression-bonded bodies are stacked, a lithium titanate green sheet at both ends is sandwiched with a PET film, and thermocompression-bonded at 80 ° C. for 30 minutes with a thermocompression bonding device did. A lithium titanate-lithium lanthanum titanate-gold laminate was produced by peeling the PET film of the top layer and the bottom layer.

[Production of laminated sintered body]
The green sheet laminate prepared by the above method is sandwiched between alumina plates, and after removing polyvinyl butyral by preliminary baking in the atmosphere at 500 ° C. for 10 hours, air atmosphere atmosphere at 1150 ° C. for 5 hours and 850 ° C. for 12 hours The laminated sintered body was produced by carrying out the main firing in this way.

[Evaluation of laminated sintered body]
It was confirmed that the layers of the laminated sintered body produced by the above method were in close contact, and an integrated laminate was obtained. The laminated sintered body was pulverized and powder X-ray diffraction measurement was conducted to find that Li ₄ Ti ₅ O ₁₂ (LTO), which is a lithium titanate having a spinel type crystal structure [ICDD No. 00-049-0207], perovskite type Diffraction lines were detected which were determined relative to lithium lanthanum titanate (LLTO) having a crystal structure [ICDD No. 01-087-0935] and Au [ICDD No. 00-004-0784] (FIG. 21).
In addition, as a result of observing a cross section with an electron microscope, two layers were arranged regularly, and as a result of evaluating by the same method as Example 1, the width of an average of each layer is 4.9 micrometers of lithium titanate, lithium titanate The lantern was 2.5 μm (FIG. 22). In addition, it was confirmed from EDX mapping that a gold layer having an average width of 3 μm was formed (FIG. 23).
In addition, the volume ratio of lithium titanate and lithium lanthanum titanate contained in the laminated sintered body calculated from the preparation ratio was LTO: LLTO = 68: 32.

[Preparation of arrayed sintered body]
A sintered body (400 μm thick) in which a lithium titanate layer, a lithium lanthanum titanate layer and a gold layer are arranged is produced by cutting out and processing the laminated sintered body produced by the above method using a grinder. did. Further, the actual density of the arrayed sintered body calculated by the dimension method is 2.92 g / cm ³ , the relative density is 60%, the porosity is 40%, and the arrayed sintered body calculated by the Archimedes method The actual density was 4.04 g / cm ³ , the relative density was 83%, and the porosity was 17%.

[Example 5]
[Preparation of lithium titanate layer and lithium lanthanum titanate layer green sheet]
Polyvinyl butyral was dissolved in a mixed solvent of toluene and 2-propanol to prepare a binder solution. The lithium titanate (LTO) calcined particles produced in Example 1 or lithium lanthanum titanate (LLTO) calcined particles and acetylene black (AB) were mixed at a weight ratio of 95: 5 to prepare a mixed powder. Each paste was prepared by adding the mixed powder to the binder solution and kneading. Acetylene black is a type of carbon black.

[Production of green sheet laminate]
A lithium titanate-lithium lanthanum titanate laminate was produced in the same manner as in Example 1 except that the lithium titanate layer green sheet and the lithium lanthanum titanate layer green sheet produced by the above method were used.

[Fabrication of laminated sintered body (sintering process)]
The green sheet laminate prepared by the above method is sandwiched between alumina plates, and after removing polyvinyl butyral by pre-baking in the atmosphere at 450 ° C. for 10 hours, at 0 ° C. for 5 hours, then at 850 ° C. for 12 hours. The laminated sintered body was produced by performing main firing in an N ₂ atmosphere containing 5 volume% of hydrogen.

[Evaluation of laminated sintered body]
It was confirmed that the layers of the laminated sintered body produced by the above method were in close contact, and an integrated laminate was obtained. When a part of the laminated sintered body was crushed and powder X-ray diffraction measurement was performed, Li ₄ Ti ₅ O ₁₂ (LTO), which is a lithium titanate having a spinel type crystal structure [ICDD No. 00-049-0207] , Rams Delight type _Li 2 _Ti 3 _O 7 is a lithium titanate having a crystal structure [ICDD No. 00-034-0393, lithium titanate lanthanum having a perovskite crystal structure (LLTO) [ICDD No. 01-087-0935 Diffraction lines identified in [] were detected (FIG. 24). Since no side reaction product was confirmed by powder X-ray diffraction, it can be seen that no side reaction product is contained at the interface between the lithium titanate layer and the lithium lanthanum titanate layer.
In addition, as a result of observing a cross section with an electron microscope, two layers were arranged regularly, and as a result of evaluating by the same method as Example 1, the width of each layer average is 5.5 micrometers of lithium titanate, lithium titanate The lantern was 3.1 μm (FIG. 25).
Further, the volume ratio of lithium titanate and lithium lanthanum titanate contained in the laminated sintered body calculated from the feed ratio was LTO: LLTO = 69: 31.

[Preparation of arrayed sintered body]
The laminated sintered body produced by the above method was cut out and processed using a grinder to produce a sintered body (400 μm in thickness) in which a lithium titanate layer and a lithium lanthanum titanate layer were arranged. The actual density of the arrayed sintered body calculated by the dimension method is 3.19 g / cm ³ , the relative density is 77%, the porosity is 23%, and the arrayed sintered body calculated by the Archimedes method The actual density was 3.74 g / cm ³ , the relative density was 90%, and the porosity was 10%.

[Example 6]
[Preparation of lithium lanthanum titanate green sheet]
Polyvinyl butyral was dissolved in a mixed solvent of toluene and 2-propanol to prepare a binder solution. The lithium lanthanum titanate (LLTO) calcined particles prepared in Example 1 and vapor grown carbon fiber (VGCF) were mixed at a weight ratio of 95: 5 to prepare a mixed powder. The paste was prepared by adding the mixed powder to the binder solution and kneading.

(Coating process)
The obtained paste was applied onto a polyethylene terephthalate (PET) film by a doctor blade method, and dried at 120 ° C. for 10 minutes to produce a green sheet.

[Production of green sheet laminate]
A lithium titanate-lithium lanthanum titanate laminate is prepared in the same manner as in Example 1 except that the lithium titanate layer green sheet produced in Example 1 and the lithium lanthanum titanate layer green sheet produced by the above method are used. Made.

[Fabrication of laminated sintered body (sintering process)]
A laminated sintered body was produced in the same manner as in Example 5 except that the green sheet laminate produced by the above method was used.

[Evaluation of laminated sintered body]
It was confirmed that the layers of the laminated sintered body produced by the above method were in close contact, and an integrated laminate was obtained. When a part of the laminated sintered body was crushed and powder X-ray diffraction measurement was performed, Li ₄ Ti ₅ O ₁₂ (LTO), which is a lithium titanate having a spinel type crystal structure [ICDD No. 00-049-0207] Diffraction lines were detected which were determined relative to lithium lanthanum titanate (LLTO) having a perovskite crystal structure [ICDD No. 01-087-0935] (FIG. 26). Since no side reaction product was confirmed by powder X-ray diffraction, it can be seen that no side reaction product is contained at the interface between the lithium titanate layer and the lithium lanthanum titanate layer.
In addition, as a result of observing a cross section with an electron microscope, two layers were arranged regularly, and as a result of evaluating by the same method as Example 1, the width of an average of each layer is 4.9 micrometers of lithium titanate, lithium titanate The lantern was 3.5 μm (FIG. 27).
Further, the volume ratio of lithium titanate and lithium lanthanum titanate contained in the laminated sintered body calculated from the feed ratio was LTO: LLTO = 69: 31.

[Preparation of arrayed sintered body]
The laminated sintered body produced by the above method was cut out and processed using a grinder to produce a sintered body (400 μm in thickness) in which a lithium titanate layer and a lithium lanthanum titanate layer were arranged. Further, the actual density of the arrayed sintered body calculated by the dimension method is 3.01 g / cm ³ , the relative density is 73%, the porosity is 27%, and the arrayed sintered body calculated by the Archimedes method The actual density was 3.48 g / cm ³ , the relative density was 84%, and the porosity was 16%.

[Example 7]
(Coating process)
The mixed powder paste of LTO and AB prepared in Example 5 and the mixed powder paste of LLTO and VGCF prepared in Example 6 are coated on a polyethylene terephthalate (PET) film by a doctor blade method, 120 ° C. The resultant was dried for 10 minutes to prepare a green sheet.

[Production of green sheet laminate]
A lithium titanate-lithium lanthanum titanate laminate was produced in the same manner as in Example 1 except that the lithium titanate layer green sheet and the lithium lanthanum titanate layer green sheet produced by the above method were used. 61 sheets of lithium titanate layer green sheets and 60 sheets of lithium lanthanum titanate layer green sheets were used.

[Fabrication of laminated sintered body (sintering process)]
After the green sheet laminate prepared by the above method is sandwiched between alumina plates and the polyvinyl butyral is removed by pre-baking under N ₂ atmosphere containing 1 vol% oxygen at 500 ° C. for 10 hours, then 1 hour at 1150 ° C. Then, a laminated sintered body was produced by performing main firing in an N ₂ atmosphere containing 0.5 volume% of hydrogen at 850 ° C. for 12 hours.

[Evaluation of laminated sintered body]
It was confirmed that the layers of the laminated sintered body produced by the above method were in close contact, and an integrated laminate was obtained. When a part of the laminated sintered body was crushed and powder X-ray diffraction measurement was performed, Li ₄ Ti ₅ O ₁₂ (LTO), which is a lithium titanate having a spinel type crystal structure [ICDD No. 00-049-0207] Diffraction lines were detected which were determined relative to lithium lanthanum titanate (LLTO) having a perovskite crystal structure [ICDD No. 01-087-0935] (FIG. 28). Since no side reaction product was confirmed by powder X-ray diffraction, it can be seen that no side reaction product is contained at the interface between the lithium titanate layer and the lithium lanthanum titanate layer.
In addition, as a result of observing a cross section with an electron microscope, two layers are arranged regularly, As a result of evaluating by the same method as Example 1, the width of an average of each layer is 2.9 micrometers of lithium titanate, lithium titanate The lantern was 1.8 μm (FIG. 29).
In addition, the volume ratio of lithium titanate and lithium lanthanum titanate contained in the laminated sintered body calculated from the preparation ratio was LTO: LLTO = 68: 32.

[Preparation of arrayed sintered body]
The laminated sintered body produced by the above method was cut out and processed using a grinder to produce a sintered body (400 μm in thickness) in which a lithium titanate layer and a lithium lanthanum titanate layer were arranged. Further, the actual density of the arrayed sintered body calculated by the dimension method is 3.03 g / cm ³ , the relative density is 76%, the porosity is 24%, and the arrayed sintered body calculated by the Archimedes method The actual density was 3.80 g / cm ³ , the relative density was 95%, and the porosity was 5%.

[Example 8]
[Production of green sheet laminate]
Example except using the lithium titanate layer green sheet and the lithium lanthanum titanate layer green sheet prepared in Example 7 and laminating so that the width after sintering is 10 μm or less in LTO and 5 μm or less in LLTO A lithium titanate-lithium lanthanum titanate laminate was prepared in the same manner as in (7).

[Fabrication of laminated sintered body (sintering process)]
A laminated sintered body was produced in the same manner as in Example 7 except that the green sheet laminate produced by the above method was used.

[Evaluation of laminated sintered body]
It was confirmed that the layers of the laminated sintered body produced by the above method were in close contact, and an integrated laminate was obtained. When a part of the laminated sintered body was crushed and powder X-ray diffraction measurement was performed, Li ₄ Ti ₅ O ₁₂ (LTO), which is a lithium titanate having a spinel type crystal structure [ICDD No. 00-049-0207] , Rams Delight type _Li 2 _Ti 3 _O 7 is a lithium titanate having a crystal structure [ICDD No. 00-034-0393, lithium titanate lanthanum having a perovskite crystal structure (LLTO) [ICDD No. 01-087-0935 A diffraction line identified in [] was detected (FIG. 30). Since no side reaction product was confirmed by powder X-ray diffraction, it can be seen that no side reaction product is contained at the interface between the lithium titanate layer and the lithium lanthanum titanate layer.
In addition, as a result of observing a cross section with an electron microscope, two layers were arranged regularly, and as a result of evaluating by the same method as Example 1, the width of an average of each layer is 9 micrometers of lithium titanate, lithium lanthanum titanate It was 5 μm (FIG. 31).
In addition, the volume ratio of lithium titanate and lithium lanthanum titanate contained in the laminated sintered body calculated from the preparation ratio was LTO: LLTO = 68: 32.

[Preparation of arrayed sintered body]
The laminated sintered body produced by the above method was cut out and processed using a grinder to produce a sintered body (400 μm in thickness) in which a lithium titanate layer and a lithium lanthanum titanate layer were arranged. Further, the actual density of the arrayed sintered body calculated by the dimension method is 2.77 g / cm ³ , the relative density is 70%, the porosity is 30%, and the arrayed sintered body calculated by the Archimedes method The actual density was 3.78 g / cm ³ , the relative density was 95%, and the porosity was 5%.

[Example 9]
[Production of green sheet laminate]
The lithium titanate layer green sheet and the lithium lanthanum titanate layer green sheet prepared in Example 7 were laminated so that the width after sintering was 15 μm or less in LTO and 7.5 μm or less in LLTO A lithium titanate-lithium lanthanum titanate laminate was produced in the same manner as in Example 7.

[Evaluation of laminated sintered body]
It was confirmed that the layers of the laminated sintered body produced by the above method were in close contact, and an integrated laminate was obtained. When a part of the laminated sintered body was crushed and powder X-ray diffraction measurement was performed, Li ₄ Ti ₅ O ₁₂ (LTO), which is a lithium titanate having a spinel type crystal structure [ICDD No. 00-049-0207] , Rams Delight type _Li 2 _Ti 3 _O 7 is a lithium titanate having a crystal structure [ICDD No. 00-034-0393, lithium titanate lanthanum having a perovskite crystal structure (LLTO) [ICDD No. 01-087-0935 The diffraction line identified in [] was detected (Figure 32). Since no side reaction product was confirmed by powder X-ray diffraction, it can be seen that no side reaction product is contained at the interface between the lithium titanate layer and the lithium lanthanum titanate layer.
In addition, as a result of observing a cross section with an electron microscope, two layers were arranged regularly, and as a result of evaluating by the same method as Example 1, the width of the average of each layer is 13 μm of lithium titanate and lithium lanthanum titanate. It was 5.8 micrometers (FIG. 33).
In addition, the volume ratio of lithium titanate and lithium lanthanum titanate contained in the laminated sintered body calculated from the preparation ratio was LTO: LLTO = 68: 32.

[Preparation of arrayed sintered body]
The laminated sintered body produced by the above method was cut out and processed using a grinder to produce a sintered body (400 μm in thickness) in which a lithium titanate layer and a lithium lanthanum titanate layer were arranged. Further, the actual density of the arrayed sintered body calculated by the dimension method is 3.06 g / cm ³ , the relative density is 77%, the porosity is 23%, and the arrayed sintered body calculated by the Archimedes method The actual density was 3.65 g / cm ³ , the relative density was 92%, and the porosity was 8%.

[Example 10]
[Production of green sheet laminate]
Example except using the lithium titanate layer green sheet and the lithium lanthanum titanate layer green sheet prepared in Example 7 and laminating so that the width after sintering is 15 μm or more in LTO and 10 μm or less in LLTO A lithium titanate-lithium lanthanum titanate laminate was prepared in the same manner as in (7).

[Evaluation of laminated sintered body]
It was confirmed that the layers of the laminated sintered body produced by the above method were in close contact, and an integrated laminate was obtained. When a part of the laminated sintered body was crushed and powder X-ray diffraction measurement was performed, Li ₄ Ti ₅ O ₁₂ (LTO), which is a lithium titanate having a spinel type crystal structure [ICDD No. 00-049-0207] , Rams Delight type _Li 2 _Ti 3 _O 7 is a lithium titanate having a crystal structure [ICDD No. 00-034-0393, lithium titanate lanthanum having a perovskite crystal structure (LLTO) [ICDD No. 01-087-0935 The diffraction line identified in [] was detected (FIG. 34). Since no side reaction product was confirmed by powder X-ray diffraction, it can be seen that no side reaction product is contained at the interface between the lithium titanate layer and the lithium lanthanum titanate layer.
In addition, as a result of observing a cross section with an electron microscope, two layers were arranged regularly, and as a result of evaluating by the same method as Example 1, the width of an average of each layer is 20 micrometers of lithium titanate, lithium lanthanum titanate It was 9 μm (FIG. 35).
In addition, the volume ratio of lithium titanate and lithium lanthanum titanate contained in the laminated sintered body calculated from the preparation ratio was LTO: LLTO = 68: 32.

[Preparation of arrayed sintered body]
The laminated sintered body produced by the above method was cut out and processed using a grinder to produce a sintered body (400 μm in thickness) in which a lithium titanate layer and a lithium lanthanum titanate layer were arranged. The actual density of the arrayed sintered body calculated by the dimension method is 3.00 g / cm ³ , the relative density is 75%, the porosity is 25%, and the arrayed sintered body calculated by the Archimedes method The actual density was 3.63 g / cm ³ , the relative density was 91%, and the porosity was 9%.

Comparative Example 1
The lithium titanate layer green sheet produced in Example 1 was cut into a disc having a diameter of 12 mm. The green sheet from which the PET film was peeled off was overlapped, and the lithium titanate layer green sheet was sandwiched between the peeled PET film and thermocompression bonded by a thermocompression bonding apparatus at 80 ° C. for 30 minutes, then the PET film of the uppermost layer and the lowermost layer By peeling off, a laminate of lithium titanate layer green sheets was produced.

[Production of sintered body]
The green sheet laminate prepared by the above method is sandwiched between alumina plates, and after removing polyvinyl butyral by preliminary baking in the atmosphere at 500 ° C. for 10 hours, air atmosphere atmosphere at 1150 ° C. for 5 hours and 850 ° C. for 12 hours The sintered body was produced by performing main firing in this way.

[Evaluation of sintered body]
When a part of the sintered body produced by the above method was pulverized and powder X-ray diffraction measurement was conducted, Li ₄ Ti ₅ O ₁₂ which is a lithium titanate having a spinel type crystal structure [ICDD No. 00-049- [0207] A diffraction line identified was detected. In addition, as a result of observing a cross section with an electron microscope, the layer of LTO was closely_contact | adhered and integrated, and the whole sintered compact was comprised by LTO.

[Preparation of sintered body for evaluation]
The sintered body produced by the above method was cut out and processed using a grinder to produce a sintered body for evaluation (thickness: 400 μm).

Comparative Example 2
A sintered body was produced in the same manner as in Comparative Example 1 except that the main sintering for producing the sintered body was changed to 1150 ° C. for 5 hours.

[Evaluation of sintered body]
When the sintered compact produced by said method was grind | pulverized and powder X-ray-diffraction measurement was performed, it is Li ₂ Ti ₃ O ₇ which is a lithium titanate which has a ramsdellite type crystal structure [ICDD number 00-034-0393] Diffraction lines were detected that were identified. In addition, as a result of observing a cross section with an electron microscope, the layer of LTO was closely_contact | adhered and integrated, and the whole sintered compact was comprised by LTO.

Comparative Example 3
[Preparation of calcined particles of lithium titanate (LTO) -lithium lanthanum titanate (LLTO) composite]
(Coprecipitation process)
A solution obtained by dissolving lanthanum chloride heptahydrate in water is mixed with an aqueous solution of titanium tetrachloride, and an aqueous solution containing 0.20 mmol / g of La, 3.10 mmol / g of Ti, and 8.67 mmol / g of Cl is prepared. Prepared. The aqueous solution was clear and did not form a precipitate upon standing at room temperature. When 250 g of this aqueous solution was sprayed into 550 g of 28% by mass ammonia water, a precipitate was formed. The precipitate is separated off, washed with water, dried at 200 ° C. and mechanically disintegrated.

(First solvothermal treatment process)
9.28 g of the precipitate generated in the above-mentioned simultaneous precipitation treatment step was placed in a pressure resistant vessel, and 43.59 mL of a 4 N aqueous solution of lithium hydroxide (equivalent to 0.17 mol of lithium hydroxide) was added. The above-mentioned pressure-resistant container was sealed, heated in a constant temperature bath set at 120 ° C. for 12 hours, subjected to hydrothermal treatment, and allowed to cool.

(2nd solvothermal treatment process)
The contents of the pressure resistant vessel subjected to the first solvothermal treatment were stirred, and 0.103 mol of acetic acid was added. The pressure resistant container was sealed, and heated in a constant temperature bath set at 180 ° C. for 12 hours to conduct hydrothermal treatment. After natural cooling, the precipitate was separated, washed with water, and dried at 200 ° C. to obtain a solid hydrothermally treated product (precursor of LTO-LLTO complex).

(Pre-baking treatment process)
The hydrothermally treated body obtained in the above step is placed in a firing boat made of alumina, fired in air at 700 ° C. for 10 hours, and calcined particles of lithium titanate (LTO) -lithium lanthanum titanate (LLTO) composite I got

[Preparation of lithium titanate-lithium lanthanum titanate composite green sheet]
(Paste preparation process)
Polyvinyl butyral was dissolved in a mixed solvent of toluene and 2-propanol to prepare a binder solution. A paste was prepared by adding the above-mentioned calcined particles of lithium titanate (LTO) -lithium lanthanum titanate (LLTO) composite to the binder solution and kneading.

(Coating process)
The obtained paste was applied onto a polyethylene terephthalate (PET) film by a doctor blade method, and dried at 120 ° C. for 10 minutes to prepare a composite green sheet.

The composite green sheet produced above was cut into a disk shape having a diameter of 12 mm. The composite green sheet obtained by cutting and peeling the PET film is overlapped, sandwiched by the peeled PET film, and thermocompression bonded by a thermocompression bonding device at 80 ° C. for 30 minutes, and then peeling the PET film of the uppermost layer and the lowermost layer A laminate of composite green sheets was produced.

[Evaluation of sintered body]
When the sintered body produced by the above method was pulverized and powder X-ray diffraction measurement was conducted, Li ₄ Ti ₅ O ₁₂ [ICDD No. 00-049-0207] which is a lithium titanate having a spinel type crystal structure, A diffraction line specific to lithium lanthanum titanate [ICDD number 01-087-0935] having a perovskite crystal structure was detected. As a result of observing the cross section with an electron microscope, it is possible to form a complex in which LTO particles and LLTO particles are closely joined and integrated, and the entire sintered body is composed of a complex of LTO and LLTO. It was
Based on the above results, the volume ratio of lithium titanate and lithium lanthanum titanate contained in the sintered body, calculated from the feed ratio, was LTO: LLTO = 59: 41.

Comparative Example 4
A sintered body was produced in the same manner as in Comparative Example 3, except that the main sintering for producing the sintered body was changed to 1150 ° C. for 5 hours.

[Evaluation of sintered body]
When the sintered compact produced by said method was grind | pulverized and powder X-ray-diffraction measurement was performed, it is Li ₂ Ti ₃ O ₇ which is a lithium titanate which has a ramsdellite type crystal structure [ICDD number 00-034-0393] Diffraction lines were detected that were determined relative to lithium lanthanum titanate [ICDD number 01-087-0935] having a perovskite crystal structure.
As a result of observing the cross section with an electron microscope, it is possible to form a complex in which particles of lithium titanate and particles of LLTO are closely joined and integrated, and the whole sintered body is a composite of lithium titanate and LLTO. It was composed of the body.
Based on the above results, the volume ratio of lithium titanate and lithium lanthanum titanate contained in the sintered body calculated from the feed ratio was lithium titanate: LLTO = 61: 39.

[Charge / discharge test using all solid cells for test]
Charge / discharge tests were conducted on the arrayed sintered bodies obtained in Examples 1 to 10 and the sintered bodies for evaluation obtained in Comparative Examples 1 to 4. All solid cells for testing were made in a glove box. A sintered body in which polyethylene oxide with a weight average molecular weight of 600,000 and lithium bis (trifluoromethanesulfonyl) imide having a weight ratio of 35% to polyethylene oxide are mixed in acetonitrile and gold is deposited on the lower and side surfaces (sequence sintering It apply | coated on the upper surface of the body or the sintered compact for evaluation. Thereafter, drying under reduced pressure was performed at 130 ° C. for 12 hours, and acetonitrile was completely removed to obtain a laminate of a dry polymer electrolyte and a sintered body. Metal lithium is adhered to the dry polymer electrolyte side of this laminate and sealed in a coin-shaped container, thereby making the sintered body a positive electrode, the dry polymer electrolyte a solid electrolyte, and a coin lithium all solid cell for test using metallic lithium as a negative electrode. C. and charge / discharge tests at 60.degree. C. and 90.degree. The charge and discharge starts from the discharge, and performs a first discharge with a cut-off potential of 2.5 to 1.25 V at a constant current of 0.002 mA / cm ² , and a discharge termination voltage of 1.25 V, and then a charge termination voltage of 1. We performed initial charge at 5V. The initial discharge capacity and the initial charge capacity were converted to values per mass of the sintered body. 36 and 37 show initial charge-discharge curves of Examples 1 to 4 at 90 ° C. and Comparative Examples 1 to 4, FIG. 38 shows initial charge-discharge curves of Examples 2 and 4 to 60 ° C., and FIG. The initial charge-discharge curves of Examples 7 to 10 at 60 ° C. are shown. In addition, the coulombic efficiency was determined by dividing the initial charge capacity by the initial discharge capacity.

From the X-ray diffraction measurement of the sintered body, the sample in which LTO having a spinel structure was detected was an S-based sample, and the sample in which Li ₂ Ti ₃ O ₇ having a ramsdellite structure was detected was an R-based sample. The width of each layer of the composite electrode of each example and the thickness of the electrode are shown in Table 1, and the charge / discharge test results (90 ° C.) of Examples 1, 2 and 4 of the S-based sample and the comparative example are shown in Table 2. Table 3 shows the charge / discharge test results of Example 3 of the R-based sample and the comparative example, and Table 4 shows the charge / discharge test results (60 ° C.) of Examples 2 and 4 to 10 of the S-based sample.

When Example 1 and Comparative Example 1 are compared, the initial charge capacity and the Coulomb efficiency increased by using the arrayed sintered body as the positive electrode. This is considered to be because the lithium ion conduction path is in the positive electrode in Example 1 having a solid electrolyte layer, as compared with Comparative Example 1 in which the entire positive electrode is composed of lithium titanate.

Moreover, when comparative example 1 and comparative example 3 are compared, the direction of comparative example 3 is excellent in the first discharge capacity and the first charge capacity. Comparative Example 3 in which the whole of the positive electrode is composed of the LTO-LLTO complex is considered to be due to the formation of a lithium ion conduction path by LLTO in the positive electrode.

On the other hand, when Example 1 and Comparative Example 3 are compared, Comparative Example 3 is more excellent in initial discharge capacity and initial charge capacity. This is considered to be due to the fact that LLTO becomes a dense sintered body and lithium ion conductivity becomes high because Comparative Example 3 passes a high temperature of 1150 ° C. in the firing step.

Example 1 and Example 2 are compared. Example 1 in which LTO is obtained by heating to 1150 ° C. and then heating is performed at 850 ° C. Example 1 in which LTO is obtained in the sintering step at 950 ° C. As compared with the above, a dense laminated sintered body can be obtained, and both the initial discharge capacity and the initial charge capacity are excellent. In addition to the fact that the electrode active material layer of LTO has become dense, LLTO forms a dense fixed electrolyte layer and a lithium ion conduction path with low resistance is formed, so that the result of the charge and discharge test is good. It is thought that it became.

When Example 2 and Comparative Example 3 are compared, although the volume ratio of the solid electrolyte is lower in Example 2, the initial discharge capacity, the initial charge capacity, and the coulombic efficiency are excellent. Example 2 and Comparative Example 3 have the same thermal history in the firing step, but the positive electrode of Example 2 is an array sintered body, and a plurality of solid electrolyte layers penetrating the positive electrode in parallel to the thickness direction of the positive electrode are ordered. In the positive electrode LTO-LLTO complex of Comparative Example 3 and the distribution of LLTO in the positive electrode is random, the lithium ion conductive path of Example 2 is higher Is considered to be formed more.

When Example 2 and Example 4 are compared, the direction of Example 4 is excellent in first time discharge capacity, first time charge capacity, and coulombic efficiency. Example 2 and Example 4 have the same heat history in the firing step, but in Example 4, a metal layer parallel to the thickness direction of the positive electrode is intentionally provided, and electron conduction is caused to LTO and LLTO. This is considered to be due to the fact that the electron conductivity of the positive electrode is higher than that of Example 2 which relies on it.

When Example 3 and Comparative Example 2 are compared, the initial discharge capacity and the initial charge capacity were increased by using the array sintered body as the positive electrode. This is considered to be because the lithium ion conduction path is in the positive electrode in Example 3 having a solid electrolyte layer, as compared to Comparative Example 2 in which the entire positive electrode is composed of lithium titanate.

Moreover, when comparative example 2 and comparative example 4 are compared, the direction of comparative example 4 is excellent in the first discharge capacity and the first charge capacity. Comparative Example 4 in which the whole of the positive electrode is composed of the LTO-LLTO complex is considered to be because the lithium ion conduction path by LLTO is formed in the positive electrode.

When Example 3 and Comparative Example 4 are compared, although the volume ratio of the solid electrolyte is lower in Example 3, the initial discharge capacity and the initial charge capacity are excellent. Example 3 and Comparative Example 4 have the same thermal history in the firing step, but Example 3 is an arrayed sintered body, since a solid electrolyte layer parallel to the thickness direction of the positive electrode is intentionally provided. It is considered that this is because more lithium ion conduction paths are formed as compared with Comparative Example 4 in which the LLTO distribution is random.

When Example 2 is compared with Examples 5 to 10, Examples 5 and 6 are more excellent in the initial discharge capacity, the initial charge capacity, and the coulombic efficiency. Example 2 and Example 5 to 10 have the same heat history in the firing step, but in Example 5 to 10, acetylene black and vapor grown carbon fiber as a conductive additive are added, and LTO and LLTO are added. It is considered that the electron conductivity of the positive electrode is higher than that of Example 2 which relies on the electron conductivity.

When Examples 7 and 8 are compared with Examples 9 and 10, Examples 7 and 8 are superior in initial discharge capacity and initial charge capacity. Further, from the charging curve, it can be understood that the overvoltage is lower in Examples 7 and 8. Examples 7 to 10 have the same heat history in the firing step and the same additives (acetylene black and vapor grown carbon fiber), but Examples 7 and 8 have an LTO layer thickness of 10 μm or less, so It is considered that this is because the distance in which the lithium ions move in the LTO layer is shorter than in Examples 9 and 10, and the resistance is smaller.

DESCRIPTION OF SYMBOLS 10 composite electrode 11 electrode active material layer 13 solid electrolyte layer 15 thickness direction of composite electrode 21 composite electrode 23 metal layer 25 electrode active material layer 31 battery 33 counter electrode layer 35 separator layer 41 laminated sintered body 51 composite electrode 53 Solid electrolyte layer 55 electrode active material portion 57 solid electrolyte portion 61 laminated sintered body 101

battery

103, 103a to 103c

negative electrode band

105, 105a to

105c separator band

107, 107a to 107c

positive electrode band

109, 109a to 109g

current collector

111, 111a to 111g current collectors 113a to 113d negative electrode active material sheets 115a to 115 g separator sheets 117a to 117d positive electrode active material sheets 123a to 123c solid electrolyte sheets 127a to 127c

solid electrolyte sheets

133a and 113b negative electrode active material grease Sheets 135a to 135d

Separator Green Sheets

137a and 137b Positive Electrode Active

Material Green Sheets

143a and 143b Solid

Electrolyte Green Sheets

147a and 147b Solid Electrolyte Green Sheets 151 Battery Battery 153 Electrode Band 161 Battery Battery 163 Current Collector 165 Current Collector 167 Current Collector 169 connection portion 171 insulator 173 insulator 175 insulator 177 insulator 181 assembled battery 183 current collector 185 connection portion

Claims

A composite electrode which is a sintered body containing an electrode active material and a solid electrolyte,
The composite electrode is an alternating arrangement in which a sheet-like electrode active material layer containing an oxide-based electrode active material and a sheet-like solid electrolyte layer containing an oxide-based solid electrolyte are alternately arranged.
The width of the electrode active material layer is 10 nm or more and 20 μm or less,
The width of the solid electrolyte layer is 10 nm or more and 20 μm or less,
The composite electrode, wherein the solid electrolyte layer penetrates the composite electrode.
The width of the electrode active material layer is 10 nm or more and 10 μm or less,
The composite electrode according to claim 1, wherein the width of the solid electrolyte layer is 10 nm or more and 10 μm or less.
The thickness of the said composite electrode is 10 micrometers or more and 3 mm or less, The composite electrode of Claim 1 or 2 characterized by the above-mentioned.
The electrode active material is a spinel type or ramsdellite type lithium titanate, titanium oxide, niobium oxide, tungsten oxide, molybdenum oxide, layered rock salt type lithium cobaltate, layered rock salt type lithium nickelate, layered rock salt type three based system Li (Ni x Co y Mn z ) O 2 (x + y + z = 1), a layered rock-salt type ternary Li (Ni x Co y Al z ) O 2 (x + y + z = 1), the spinel-type lithium manganate, Lithium spinel type lithium manganese oxide (LiMn 1.5 Ni 0.5 O 4 ), lithium olivine type transition metal phosphate represented by LiMPO 4 (M = Fe, Mn, Co, Ni), and Li having a NASICON structure 3 V 2 (PO 4) any one of claims 1 to 3, wherein the at least one selected from the group consisting of 3 Composite electrode as described in.
The solid electrolyte comprises a perovskite-type lithium lanthanum titanate, a perovskite-type lithium lanthanum niobate (Li x La (1-x) / 3 NbO 3 ) (0 ≦ x ≦ 1), and a garnet-type Li 7 La 3 Zr 2 O 12 , garnet-type Li 5 La 3 Nb 2 O 12 , garnet-type Li 5 La 3 Ta 2 O 12 , garnet-type Li 6 La 2 BaTa 2 O 12 , lithium phosphate (Li 3 PO 4 ), Lithium niobate (LiNbO 3 ), LAGP with NASICON structure (Li 1 + x Al x Ge 2-x (PO 4 ) 3 (0 ≦ x ≦ 1)), LATP with NASICON structure (Li 1 + x Al x Ti 2-x (PO 4) 4 ) 3 (0 ≦ x ≦ 1), and LZP (Li 1 + 4x Zr 2-x (PO 4 ) of the NASICON structure 5. The composite electrode according to any one of claims 1 to 4, which is at least one selected from the group consisting of 3 (0 ≦ x ≦ 0.4).
The composite according to any one of claims 1 to 5, wherein the electrode active material is a spinel type or ramsdellite type lithium titanate, and the solid electrolyte is a perovskite type lithium lanthanum titanate. Body electrode.
The composite electrode is a sintered body having a porosity of 40% or less calculated by the Archimedes method,
Charge and discharge tests were performed at a rate of 0.002 mA / cm 2 at a temperature of 60 ° C. in an all-solid cell in which the composite electrode as the positive electrode, the dry polymer electrolyte as the separator layer, and metallic lithium as the negative electrode were laminated. The composite electrode according to any one of claims 1 to 6, wherein an initial charge capacity and / or an initial discharge capacity of the composite electrode at the time of carrying out is 10 mAh / g or more.
The composite electrode further has a metal layer parallel to the solid electrolyte layer,
The composite electrode according to any one of claims 1 to 7, wherein the metal layer contains at least one metal selected from the group consisting of gold, silver, copper, nickel, and aluminum.
The composite electrode according to any one of claims 1 to 8, wherein the solid electrolyte layer contains a conductive aid.
A precursor of a composite electrode comprising an electrode active material or a precursor thereof, and a solid electrolyte or a precursor thereof, and providing the composite electrode according to any one of claims 1 to 9 by sintering,
The precursor of the composite electrode has a layer of a solid electrolyte or a precursor thereof penetrating the precursor of the composite electrode,
A sheet-like solid including a layer of a sheet-like electrode active material or a precursor thereof containing an oxide-based electrode active material or a precursor thereof, and a precursor of the composite electrode containing an oxide-based solid electrolyte or a precursor thereof The electrolyte layer is an alternating array of layers of its precursors,
The specific surface area of the electrode active material or its precursor is 0.5 m 2 / g or more,
A precursor of a composite electrode, wherein a specific surface area of the solid electrolyte or a precursor thereof is 0.5 m 2 / g or more.
11. The precursor of a composite electrode according to claim 10, further comprising an organic binder which is pyrolyzed during sintering.
A method of producing the composite electrode according to any one of claims 1 to 9,
Obtaining a laminate in which a layer containing an electrode active material or a precursor thereof and a layer containing a solid electrolyte or a precursor thereof are alternately laminated;
Sintering the laminated body to obtain a laminated sintered body in which an electrode active material layer and a solid electrolyte layer are alternately laminated;
A method of manufacturing a composite electrode, comprising:
The laminating step is a step of obtaining a laminate in which a layer containing lithium titanate or a precursor thereof and a layer containing lithium lanthanum titanate or a precursor thereof are alternately laminated.
The sintering step is a step of sintering at a temperature of 400 ° C. or more and 1000 ° C. or less after sintering at a temperature of more than 1000 ° C.
The composite electrode according to claim 12, wherein the composite electrode is an alternating arrangement in which an electrode active material layer containing spinel lithium titanate and a solid electrolyte layer containing lithium lanthanum perovskite lithium titanate are alternately arranged. Method of manufacturing composite electrode.
A negative electrode layer for absorbing and releasing lithium ions, a separator layer for conducting lithium ions, and a positive electrode layer for absorbing and releasing lithium ions are laminated in this order,
A lithium ion battery using the composite electrode according to any one of claims 1 to 9 as the negative electrode layer or the positive electrode layer.
The negative electrode zone for inserting and extracting lithium ions, the separator zone for conducting lithium ions, and the positive electrode zone for inserting and extracting lithium ions are adjacent in this order,
The negative electrode band and / or the positive electrode band is the composite electrode according to any one of claims 1 to 9,
The lithium ion battery, wherein the solid electrolyte layer in the composite electrode extends in a direction perpendicular to the separator zone and is in contact with the separator zone.
The lithium ion battery according to claim 15, wherein the thickness of the solid electrolyte layer in the composite electrode is smaller than the width of the separator band.
The width of the negative electrode band is not less than 20 μm and not more than 500 μm,
The width of the separator band is 100 μm or less,
The lithium ion battery according to claim 15 or 16, wherein the width of the positive electrode band is 20 μm or more and 500 μm or less.
The lithium ion battery further comprises a first current collector and / or a second current collector,
The first current collector, the negative electrode band, and the separator band are adjacent in this order, and / or the separator band, the positive electrode band, and the second current collector are included. Adjacent in order,
The solid electrolyte layer in the composite electrode penetrates the composite electrode so as to connect between the first and / or second current collectors and the separator zone. A lithium ion battery according to any one of claims 15 to 17.
An assembled battery comprising a plurality of lithium ion batteries according to any one of claims 15 to 17, comprising:
The battery assembly includes a pair of current collectors, a plurality of the lithium ion batteries, and one or more electrode bodies.
A plurality of said lithium ion batteries are arranged in a row between said pair of current collectors;
The negative electrode band or the positive electrode band of the lithium ion battery at one end is adjacent to one of the pair of current collectors, and the negative electrode band or the positive electrode band of the lithium ion battery at the other end and the pair of current collectors Adjacent to the other
Two adjacent lithium ion batteries are adjacent to each other through one electrode body,
The negative electrode band of one of the lithium ion batteries is adjacent to the electrode body, and the positive electrode band of the other lithium ion battery is adjacent to the electrode body, with the one electrode body interposed therebetween.
An assembled battery comprising a plurality of the lithium ion batteries connected in series.
An assembled battery comprising a plurality of lithium ion batteries according to any one of claims 15 to 17, comprising:
The battery assembly includes a plurality of current collectors and a plurality of lithium ion batteries.
A plurality of said lithium ion batteries are arranged in a row,
The negative electrode band or the positive electrode band of the lithium ion battery at one end is adjacent to one current collector, and the negative electrode band or the positive electrode band of the lithium ion battery at the other end is other one current collector Are adjacent to each other,
The two adjacent lithium ion batteries are adjacent to each other via another one of the current collectors,
The negative electrode band of one of the lithium ion battery and the other of the lithium ion battery is adjacent to the current collector, or one of the lithium ion battery, with the other one of the current collectors interposed therebetween. The positive electrode band of the other lithium ion battery is adjacent to the current collector,
The current collectors adjacent to the negative electrode band are electrically connected to each other,
The current collectors adjacent to the positive electrode band electrically connect each other,
A battery assembly characterized by connecting a plurality of the lithium ion batteries in parallel.
A method of manufacturing a lithium ion battery according to any one of claims 15 to 18, comprising:
A structure in which a first portion containing a negative electrode active material or a precursor thereof, a second portion containing a solid electrolyte or a precursor thereof, and a third portion containing a positive electrode active material or a precursor thereof in this order Step 1 to form
The fourth portion containing the solid electrolyte or the precursor thereof, the fifth portion containing the solid electrolyte or the precursor thereof, and the sixth portion containing the solid electrolyte or the precursor thereof form an adjacent structure in this order. Process 2 to
Alternately to obtain a laminate,
A sintering step of sintering the laminate;
Have
However,
In step 1 performed after step 2, the first portion is placed on the fourth portion, the second portion is placed on the fifth portion, and the second portion is placed on the sixth portion. Form the third part,
In step 2, which is performed after step 1, the fourth portion is disposed on the first portion, the fifth portion is disposed on the second portion, and the fourth portion is disposed on the third portion. A method of manufacturing a lithium ion battery, comprising forming a sixth portion.
A method of manufacturing a lithium ion battery according to any one of claims 15 to 18, comprising:
Step 3 of forming a structure in which a negative electrode active material sheet containing a negative electrode active material, a first separator sheet containing a solid electrolyte, and a positive electrode active material sheet containing a positive electrode active material are adjacent in this order;
Step 4 of forming a structure in which a first solid electrolyte sheet containing a solid electrolyte, a second separator sheet containing a solid electrolyte, and a second solid electrolyte sheet containing a solid electrolyte are adjacent in this order;
Alternately to obtain a laminate,
However,
In step 3 performed after step 4, the negative electrode active material sheet is placed on the first solid electrolyte sheet, the first separator sheet is placed on the second separator sheet, and the second solid sheet is placed on the second solid sheet. Forming the positive electrode active material sheet on an electrolyte sheet;
In step 4 performed after step 3, the first solid electrolyte sheet is placed on the negative electrode active material sheet, the second separator sheet is placed on the first separator sheet, and the positive electrode active material sheet A method of manufacturing a lithium ion battery, wherein the second solid electrolyte sheet is formed on the