JP2017168429A - Bipolar lamination type all-solid type lithium secondary battery and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an all-solid type lithium secondary battery which has a structure to prevent an internal short circuit and which is arranged so that a whole bipolar laminate can be baked integrally.SOLUTION: A bipolar lamination type all-solid type lithium secondary battery comprises: a bipolar electrode 50b; and a solid electrolyte layer. The bipolar electrode includes a current collector layer 10b, a positive electrode layer 20b formed/laminated on one principal face of the current collector layer, and a negative electrode layer 30b formed/laminated on other principal face of the current collector layer. When viewed from a laminating direction, the bipolar electrode and the solid electrolyte layer each have a rectangular or circular form. The outer edges of the current collector layer are located inside the outer edges of the positive and negative electrode layers. In the bipolar electrode, one or each of the positive and negative electrode layers has an electrically insulative part in an outer edge region of a rectangle or circular form in a face where the one or each of the positive and negative electrode layers touches the current collector layer. When the bipolar electrode is viewed from the laminating direction, a projection of the electrically insulative part makes an entire circumference of the outer edge of a rectangle or circular form. The bipolar electrode and the solid electrolyte layer form a sintered assembly.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a lithium ion secondary battery, and more particularly to a bipolar laminated all solid lithium secondary battery using a solid electrolyte as an electrolyte that propagates lithium ions, and a method for manufacturing the same.

  Since the lithium ion secondary battery has a higher energy density than other secondary batteries, it is advantageous for reducing the size and weight, increasing the capacity, and / or increasing the output of the secondary battery. For this reason, lithium-ion secondary batteries are used for power sources for automobiles such as small electric devices (for example, portable personal computers and mobile phones) and large electric devices (for example, HEV (hybrid vehicles) and EVs (electric vehicles)). Power supply and power storage power source).

  In recent years, from the viewpoint of expanding the availability of lithium ion secondary batteries for large electrical equipment, installation in a high temperature environment (for example, in an engine room or outdoors) has been studied, and a lithium ion secondary that can withstand the high temperature environment. There is a need for a battery. However, the conventional lithium ion secondary battery using a non-aqueous electrolyte is generally said to have a heat resistance temperature of about 60 ° C., and the solvent constituting the non-aqueous electrolyte is flammable. Therefore, it has a weak point in terms of heat resistance and fire resistance.

  In order to overcome this weakness, an all-solid lithium secondary battery using a solid electrolyte instead of a non-aqueous electrolyte is now under intense research. All solid-state lithium secondary batteries use conventional lithium ions that use non-aqueous electrolytes because the solid electrolytes used (eg, solid polymer electrolytes and inorganic electrolytes) have a heat-resistant temperature exceeding 100 ° C and are not flammable. It can be used in a higher temperature environment than the secondary battery.

  In a lithium ion secondary battery, a bipolar laminated structure using bipolar electrodes is often employed as a battery structure that increases volume energy density. In the bipolar laminated type of the nonaqueous electrolyte lithium secondary battery, a short circuit between adjacent bipolar electrodes is prevented by providing a separator between the bipolar electrodes.

  On the other hand, in the all-solid lithium secondary battery, since the solid electrolyte layer does not have fluidity, the solid electrolyte layer itself can also function as a separator (in other words, it is necessary to provide a separate separator). Therefore, there is a potential that the volume energy density can be further increased as compared with the non-aqueous electrolyte lithium secondary battery. However, since a separate separator is not provided, it is necessary to devise a laminated structure and a manufacturing method for preventing an internal short circuit of the battery.

  For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-158222) discloses a thin-film solid lithium comprising five layers of a positive / negative active material layer, a solid electrolyte layer between them, a current collector layer directly above and immediately below the active material layer. A multi-layer battery having a configuration in which an ion battery is used as one battery cell and the battery cells are stacked in layers on a single substrate, and each layer of the battery cells is stacked. When laminating a plurality of layers, the width of the peripheral portion of the laminated film of each layer is increased in the order of the active material layer, the current collector layer, and the solid electrolyte layer, and the active material layer is surrounded by the current collector layer and the solid electrolyte layer. Further, a multilayer laminated battery having a structure in which the current collector layer is laminated with a solid electrolyte layer at the periphery to insulate the battery cells is disclosed.

  Patent Document 2 (WO 2012/020700) discloses at least first and second unit cells each composed of a positive electrode layer, a solid electrolyte layer, and a negative electrode layer, which are sequentially stacked, and the positive electrode of the first unit cell. An inner current collecting layer having one side surface in contact with the layer and the other side surface in contact with the negative electrode layer of the second unit cell, and disposed so as to be interposed between the first and second unit cells And the internal current collecting layer includes an electron conductive material, and further includes a specific conductive material that is ionically conductive and insulating.

  Patent Document 3 (WO 2012/164642) discloses a current collector, a positive electrode active material layer containing a positive electrode active material formed on one surface of the current collector, and the other surface of the current collector. A bipolar electrode having an electrode active material layer formed of a negative electrode active material layer containing a negative electrode active material, and a solid electrolyte layer containing a solid electrolyte, and a plurality of the bipolar electrodes via the solid electrolyte layer The electrode active material layer is formed on the inner side of the end of the current collector, and between the end of the electrode active material layer and the current collector surface. Discloses a bipolar all solid state battery in which a reinforcing layer formed on the surface of the current collector is disposed.

JP 2004-158222 A International Publication No. 2012/020700 International Publication No. 2012/164642

  All-solid lithium secondary batteries can be broadly classified into thin film types and bulk types. From the viewpoint of battery capacity, a bulk type that can increase the absolute amount of the electrode active material is advantageous. That is, when a large-capacity secondary battery for large-sized electrical equipment is assumed, a bulk-type all-solid lithium secondary battery is a target. In other words, since the battery capacity can be afforded with a bulk type configuration, there is less restriction due to the size of the electric device (the amount of power consumption), and the device can be widely applied.

  According to Patent Document 1, it is said that a multilayer laminated battery that does not require a photoresist process and greatly simplifies the manufacturing process (that is, reduces the manufacturing cost) can be provided. However, since the multilayer laminated battery of Patent Document 1 is a technique related to a thin-film type all-solid lithium secondary battery, it is difficult to simply apply the technique to a large-capacity secondary battery for a large electric device.

  According to Patent Document 2, in the positive electrode layer, the negative electrode layer, the solid electrolyte layer, and the internal current collector layer constituting the stacked solid battery, the active material and the solid electrolyte material included in the positive electrode layer and / or the negative electrode layer, By including a lithium-containing phosphate compound in the solid electrolyte material contained in the electrolyte layer and the specific conductive material contained in the internal current collector layer, each layer can share the phosphate skeleton, and peeling of each layer It is said that it is possible to provide a laminated solid battery that is integrally sintered while suppressing the occurrence of cracks. However, since the stacked solid state battery of Patent Document 2 is assumed to be a relatively small secondary battery for small electronic devices, the technology is simply transferred to a large capacity secondary battery for large electric devices. There are difficulties to do.

  According to Patent Document 3, the current collector is broken near the end of the bipolar all solid state battery by disposing a reinforcing layer that reinforces the current collector between the end of the electrode active material layer and the current collector surface. It is said that a bipolar all solid state battery capable of preventing the occurrence of an internal short circuit can be provided. Further, it is described that a thin metal foil is preferable as the current collector material, and a resin material is preferable as the reinforcing layer material. However, when a resin material is used as the reinforcing layer material, integrated high-temperature firing of the bipolar all solid state battery is considered difficult from the viewpoint of the heat resistance of the resin material.

  In an all-solid lithium secondary battery, the solid electrolyte as a lithium ion conduction path does not have fluidity. Therefore, in order to increase the output of the secondary battery, the solid electrolyte itself needs to have high ion conductivity. At the same time, a good ion conduction path is constructed between the solid electrolyte layer and the electrode active material layer (impedance of ion conduction is minimized), and a good electron conduction path is established between the electrode active material layer and the bipolar electrode. Need to build. In addition, in the case of a bipolar stacked battery, it is necessary to prevent an internal short circuit.

  In order to realize these requirements, it is preferable to integrally heat the entire bipolar laminate while preventing an internal short circuit, but it is difficult to achieve with a simple combination of the techniques of Patent Documents 1 to 3, and there are further ideas. is necessary.

  Accordingly, an object of the present invention is a bulk type bipolar stacked type all solid lithium secondary battery having a structure for preventing an internal short circuit, and capable of integrally firing the entire bipolar stacked body at a high temperature. An object of the present invention is to provide a solid lithium secondary battery and a manufacturing method thereof.

(I) One aspect of the present invention is a bipolar laminated all solid lithium secondary battery in which bipolar electrodes and solid electrolyte layers are alternately laminated,
The bipolar electrode includes a current collector layer, a positive electrode layer formed on one main surface of the current collector layer, and a negative electrode layer formed on the other main surface of the current collector layer. Consists of
When viewed from the stacking direction, each of the bipolar electrode and the solid electrolyte layer has a quadrangular or circular shape, and the current collector layer has an outer edge inside the outer edges of the positive electrode layer and the negative electrode layer. Yes,
The positive electrode layer and / or the negative electrode layer in the bipolar electrode includes an electrical insulating portion in an outer edge region of the quadrilateral or the circle on a surface in contact with the current collector layer, and the bipolar electrode is disposed in the stacking direction. When viewed from the projection of the electrical insulation portion constitutes the entire circumference of the quadrilateral or the circular outer edge,
The bipolar laminated all solid lithium secondary battery is characterized in that the bipolar electrode and the solid electrolyte layer form a sintered joined body.
In the present invention, a quadrangle includes a rectangle with rounded corners, and a circle includes a perfect circle, an ellipse, an ellipse, and a rounded rectangle (so-called racetrack shape).

The present invention can add the following improvements and changes to the above-mentioned bipolar stacked type all solid lithium secondary battery (I).
(I) When viewed from the stacking direction, each of the bipolar electrode and the solid electrolyte layer has a quadrilateral shape, and the electrical insulating portion of the positive electrode layer is disposed in a pair of opposite side regions of the quadrilateral, The electrically insulating portion of the negative electrode layer is disposed in another pair of opposite side regions of the quadrilateral.
(Ii) The current collector layer is mainly composed of a carbon-based material and / or a conductive oxide,
The positive electrode layer is mainly composed of a lithium transition metal composite oxide,
The negative electrode layer is mainly composed of a carbon-based material, a lithium transition metal composite oxide and / or a lithium transition metal composite nitride,
The solid electrolyte layer is mainly composed of a lithium composite oxide electrolyte.
In addition, in this invention, a main component shall mean the component used as the frame | skeleton and aggregate of the said layer.

(II) Another aspect of the present invention is a method for producing a bipolar laminated all solid lithium secondary battery in which bipolar electrodes and solid electrolyte layers are alternately laminated,
The bipolar electrode includes a current collector layer, a positive electrode layer formed on one main surface of the current collector layer, and a negative electrode layer formed on the other main surface of the current collector layer. Consists of
When viewed from the stacking direction, each of the bipolar electrode and the solid electrolyte layer has a quadrangular or circular shape, and the current collector layer has an outer edge inside the outer edges of the positive electrode layer and the negative electrode layer. Is formed to be
The positive electrode layer and / or the negative electrode layer in the bipolar electrode includes an electrical insulating portion in an outer edge region of the quadrilateral or the circle on a surface in contact with the current collector layer, and the bipolar electrode is disposed in the stacking direction. When viewed from the projection of the electrical insulation portion constitutes the entire circumference of the quadrilateral or the circular outer edge,
A current collector layer green in which a current collector layer green sheet containing a main component of the current collector layer and a resin binder is formed and then cut into a quadrilateral or circular shape of a predetermined size to prepare a current collector layer green substrate Substrate preparation process;
A positive electrode layer green substrate preparation step of preparing a positive electrode layer green substrate by cutting out into a quadrangular or circular shape of a predetermined dimension after forming a positive electrode layer green sheet containing the main component of the positive electrode layer and a resin binder;
A negative electrode layer green substrate preparation step of preparing a negative electrode layer green substrate by cutting out into a quadrangular or circular shape of a predetermined dimension after forming a negative electrode layer green sheet containing the main component of the negative electrode layer and a resin binder,
A solid electrolyte layer green substrate preparation step of preparing a solid electrolyte layer green substrate by forming a solid electrolyte layer green sheet containing a main component of the solid electrolyte layer and a resin binder and then cutting into a quadrilateral or circular shape of a predetermined size; ,
The negative electrode layer green substrate, the current collector layer green substrate, the positive electrode layer green substrate, and the solid electrolyte layer green substrate prepared in each of the above steps are sequentially stacked to form an all-solid battery green substrate stack. A solid battery green substrate laminate forming step;
An all-solid battery sintered assembly obtained by firing the whole solid battery green substrate laminate and sintering and bonding the negative electrode layer, the current collector layer, the positive electrode layer, and the solid electrolyte layer. An all solid state battery green substrate laminate firing step to form,
In the positive electrode layer green substrate preparation step and / or the negative electrode layer green substrate preparation step, after forming an electrical insulation part green sheet to be the electrical insulation part, the positive electrode active green part is embedded and integrated. The positive electrode layer green sheet and / or the negative electrode layer green sheet are formed by laminating the material part green sheet and / or the negative electrode active material part green sheet, and then the electric insulating part based on the electric insulating part green sheet Is a step of cutting so as to be disposed in the outer edge region of the quadrilateral or the circle,
The all-solid-state battery green substrate laminate forming step includes laminating the positive electrode layer green substrate on one main surface of the current collector layer green substrate and laminating the negative electrode layer green substrate on the other main surface. Including a bipolar electrode green substrate forming step of forming a bipolar electrode green substrate;
In the bipolar electrode green substrate forming step, the electrical insulating portion in the positive electrode green substrate and / or the negative electrode green substrate faces the current collector green substrate, and the bipolar electrode green substrate is stacked. When viewed from the direction, the positive electrode layer green substrate and the negative electrode layer green substrate are formed on the current collector layer green substrate so that the projection of the electrical insulating portion constitutes the entire circumference of the quadrilateral or the circular outer edge. Provided is a method for manufacturing a bipolar stacked type all solid lithium secondary battery, characterized in that it is a step of stacking.

The present invention can be modified or changed as described below in the manufacturing method (II) of the bipolar stacked type all solid lithium secondary battery.
(Iii) When viewed from the stacking direction, each of the bipolar electrode and the solid electrolyte layer has a quadrangular shape,
In the bipolar electrode green substrate forming step, when viewed from the stacking direction, the electrical insulating portion in the positive electrode layer green substrate is disposed in a pair of opposite side regions of the quadrilateral, and the positive electrode layer green substrate in the negative electrode layer green substrate The step of laminating the positive electrode layer green substrate and the negative electrode layer green substrate on the current collector layer green substrate such that an electrical insulating portion is disposed in another pair of opposite side regions of the quadrilateral.
(Iv) In the current collector layer green substrate preparation step, the current collector layer green substrate shrinks more than the positive electrode layer green substrate and the negative electrode layer green substrate in the all solid state battery green substrate laminate firing step. Is a step of adjusting the current collector layer slurry to form the current collector layer green sheet so as to increase.
(V) The all solid state battery green substrate laminate forming step includes:
A positive monopolar electrode green substrate forming step of forming the positive monopolar electrode green substrate by laminating the positive electrode layer green substrate on one main surface of the current collector layer green substrate;
A negative monopolar electrode green substrate forming step of forming the negative monopolar electrode green substrate by laminating the negative electrode layer green substrate on one main surface of the current collector layer green substrate;
The bipolar electrode green substrate and the solid electrolyte layer green substrate are alternately stacked, and the positive monopolar electrode green substrate and the negative monopolar electrode green are disposed at both ends of the bipolar electrode green substrate-solid electrolyte layer green substrate stack in the stacking direction. It further includes a laminate assembly process for laminating the substrates.
(Vi) The main component of the current collector layer is made of a carbon-based material and / or a conductive oxide,
The main component of the positive electrode layer is composed of a lithium transition metal composite oxide,
The main component of the negative electrode layer is composed of a carbon-based material, a lithium transition metal composite oxide and / or a lithium transition metal composite nitride,
The main component of the solid electrolyte layer is composed of a lithium composite oxide electrolyte.

  According to the present invention, an all-solid lithium secondary battery of a bulk type and a bipolar laminate type that has a structure that prevents an internal short circuit and that can integrally fire the entire bipolar laminate. A secondary battery and a method for manufacturing the secondary battery can be provided.

It is process drawing which shows an example of the manufacturing method of the bipolar laminated type all-solid-state lithium secondary battery which concerns on this invention. It is a decomposition | disassembly schematic diagram which shows an example of the all-solid-state battery green board | substrate laminated body which is a precursor of the bipolar lamination-type all-solid-state lithium secondary battery which concerns on this invention. It is a longitudinal cross-sectional schematic diagram which shows an example of the all-solid-state battery sintered joined body obtained by the all-solid-state battery green board | substrate laminated body baking process. It is a perspective schematic diagram which shows the example of a procedure of a positive electrode layer green board | substrate preparation process. It is a perspective schematic diagram which shows the other example of a procedure of a positive electrode layer green board | substrate preparation process. It is a perspective schematic diagram which shows the other example of a procedure of a positive electrode layer green board | substrate preparation process. It is a longitudinal cross-sectional schematic diagram which shows an example of the all-solid-state battery structure obtained by an external terminal connection process. It is a longitudinal cross-sectional schematic diagram which shows an example of the all-solid-state battery obtained by a packaging process.

(Basic idea of the present invention)
As described above, in the all-solid-state lithium secondary battery, the solid electrolyte as the lithium ion conduction path does not have fluidity. Therefore, in order to increase the output of the secondary battery, the solid electrolyte itself has high ion conductivity. And a good ion conduction path between the solid electrolyte layer and the electrode active material layer (to reduce the obstacle of ion conduction as much as possible) and between the electrode active material layer and the bipolar electrode layer It is necessary to construct a good electron conduction path. In addition, in the case of a bipolar stacked battery, it is necessary to prevent an internal short circuit. In order to realize these requirements, sintered junctions in which the entire bipolar laminate (the entire laminate of the positive electrode layer, the current collector layer, the negative electrode layer, and the solid electrolyte layer) is integrally fired while preventing an internal short circuit. The body is desirable.

  Patent Document 2 teaches a technical idea of integrally sintering the entire bipolar laminate, but does not take into account differences in the amount of firing shrinkage of each layer constituting the laminate. This is considered because Patent Document 2 assumes a relatively small secondary battery (for example, a laminated body diameter of 12 mm) for a small electronic device. More specifically, even if a difference of 5% occurs in the firing shrinkage of each layer, the difference in diameter is 0.6 mm (the protrusion amount on one side is 0.3 mm) with respect to the diameter of 12 mm. Since the absolute amount is small, it is considered that the internal short circuit of the battery need not be considered.

  On the other hand, the present invention assumes a large-capacity secondary battery (for example, a laminate size of about 50 to 100 mm square viewed from the stacking direction) for a large electric device. In this case, if the laminate size is 60 mm square and the difference in firing shrinkage of each layer is 5%, the length difference on one side is 3 mm (the protruding amount on one side is 1.5 mm). Since the absolute amount of the difference in shrinkage increases as the overall dimensions increase, there is a problem that the risk of an internal short circuit of the battery increases rapidly.

  Therefore, the present inventor has conducted earnest research on a laminate structure that can prevent internal short circuit of a battery and a method of manufacturing the laminate structure even if a certain amount of difference in firing shrinkage of each layer constituting the laminate occurs. It was. As a result, the amount of firing shrinkage of the current collector layer is controlled to be larger than those of the positive electrode layer and the negative electrode layer, and the surface of the positive electrode layer and the negative electrode layer in contact with the current collector layer has a quadrilateral opposite side region. It has been found that the internal short circuit of the battery (short circuit between the positive electrode layer and the negative electrode layer, short circuit between the current collector layers) can be effectively prevented by forming the electrical insulating portion. The present invention has been completed based on this finding.

  Hereinafter, an embodiment according to the present invention will be specifically described along a manufacturing procedure with reference to the drawings. However, the present invention is not limited to the embodiments mentioned here, and can be appropriately combined with known techniques or improved based on known techniques without departing from the technical idea of the invention. It is. In the drawings, the same reference numerals are given to the same members / parts, and duplicate descriptions are omitted.

  In this specification, a lithium ion secondary battery will be described as an example of an all-solid secondary battery. However, the technical idea of the present invention is not only a lithium ion secondary battery but also a sodium ion secondary battery, a magnesium ion The present invention can also be applied to secondary batteries, aluminum ion secondary batteries, and the like.

  FIG. 1 is a process diagram showing an example of a method for producing a bipolar laminated all solid lithium secondary battery according to the present invention. FIG. 2 is an exploded schematic view showing an example of an all solid state battery green substrate laminate obtained by the all solid state battery green substrate laminate formation step.

  As shown in FIGS. 1 and 2, the manufacturing method of the present invention includes a current collector layer green substrate preparation step for preparing a current collector layer green substrate 10b and a positive electrode layer green substrate preparation for preparing a positive electrode layer green substrate 20b. Negative electrode layer green substrate preparation step for preparing negative electrode layer green substrate 30b, solid electrolyte layer green substrate preparation step for preparing solid electrolyte layer green substrate 40b, current collector layer green substrate 10b and positive electrode layer green substrate 20b All-solid-state battery green substrate laminate forming step of forming all-solid-state battery green substrate laminate 100b from negative electrode layer green substrate 30b and solid electrolyte layer green substrate 40b, and sintering joining of all-solid-state battery green substrate laminate 100b as a whole And an all solid state battery green substrate laminate firing step for forming an all solid state battery sintered assembly.

  The all-solid-state battery green substrate laminate forming step includes a bipolar electrode green substrate forming step of forming a bipolar electrode green substrate 50b from the current collector layer green substrate 10b, the positive electrode layer green substrate 20b, and the negative electrode layer green substrate 30b. Positive monopolar electrode green substrate forming step of forming positive monopolar electrode green substrate 61b from electric body layer green substrate 10b and positive electrode layer green substrate 20b, negative monopolar electrode green substrate 65b from current collector layer green substrate 10b and negative electrode layer green substrate 30b Forming a negative monopolar electrode green substrate forming step, and forming an all-solid-state battery green substrate laminate 100b from a positive monopolar electrode green substrate 61b, a solid electrolyte layer green substrate 40b, a bipolar electrode green substrate 50b, and a negative monopolar electrode green substrate 65b You may comprise from the laminated body assembly process to do.

  Moreover, it further has the external terminal connection process which connects an external terminal to a positive monopolar electrode and a negative monopolar electrode, and the packaging process which packages an all-solid-state battery structure as needed.

  In the all-solid-state battery green substrate laminate firing step, the laminated green substrates are fired and contracted, and the sintered joining between the layers proceeds to form an all-solid battery sintered joined body. FIG. 3 is a schematic longitudinal sectional view showing an example of an all-solid battery sintered assembly obtained by the all-solid battery green substrate laminate firing step.

  As shown in FIG. 3, the all-solid battery sintered assembly 100c includes a positive monopolar electrode 61c (current collector layer 10c + positive electrode layer 20c), a solid electrolyte layer 40c, and a bipolar electrode 50c (negative electrode layer 30c + current collector). Layer 10c + positive electrode layer 20c) and negative monopolar electrode 65c (negative electrode layer 30c + current collector layer 10c). The current collector layer green substrate 10b is formed so as to have a firing shrinkage larger than that of other green substrates (the positive electrode layer green substrate 20b and the negative electrode layer green substrate 30b) during the firing process. The body layer 10c is formed such that its outer edge is inside the outer edges of the positive electrode layer 20c and the negative electrode layer 30c.

  In the example shown in FIG. 3, the opposite side region of the positive electrode layer 20c (a pair of opposite sides of the quadrangle as viewed from the stacking direction) and the opposite side region of the negative electrode layer 30c (the other pair of quadrilaterals as viewed from the stacking direction). Electrically insulating portions 22c and 32c are respectively formed in the opposite side region). That is, when the bipolar electrode 50c is viewed from the stacking direction, the projections of the electrical insulating portions 22c and 32c form the entire outer periphery of the quadrilateral. Thereby, even if the positive electrode layer 20c and the negative electrode layer 30c in the bipolar electrode 50c come into contact with each other, an internal short circuit can be prevented.

  Hereinafter, each process of the manufacturing method of the bipolar lamination type all solid lithium secondary battery concerning the present invention is explained more concretely.

(Positive layer green substrate preparation process)
This step is a step of preparing a positive electrode layer green substrate 20b by forming a positive electrode layer green sheet and then cutting it into a quadrangular or circular shape of a predetermined size. The positive electrode layer green substrate 20b includes a positive electrode active material portion 21b and an electric insulation portion 22b. In the example of FIG. 2, the electric insulation portion 22b is formed in the opposite side region of the quadrilateral.

  FIG. 4A is a schematic perspective view illustrating a procedure example of a positive electrode layer green substrate preparation step. As shown in FIG. 4A, first, a pair of parallel electrical insulation part green sheets 22 a is formed on the carrier sheet 70. Next, the positive electrode active material part green sheet 21a is laminated so as to embed and integrate a pair of parallel electric insulation part green sheets 22a to form the positive electrode layer green sheet 20a. Thereafter, the positive pair green substrate 20b is prepared by performing a cutting process so that the pair of parallel electric insulating portion green sheets 22a are arranged in the opposite side region of the quadrilateral.

  There is no special limitation in the formation method of each green sheet, For example, a doctor blade method and a screen printing method can be used suitably. Moreover, there is no special limitation in the cutting-out method of a green substrate, For example, a punching process can be used suitably. The same applies to the formation of the green sheet described below.

  FIG. 4B is a schematic diagram illustrating another example of the procedure for preparing the positive electrode layer green substrate. As shown in FIG. 4B, the electrical insulating portion green sheet 22 a ′ having a quadrilateral cutout is formed on the carrier sheet 70. Next, the positive electrode active material part green sheet 21a is laminated so as to embed and integrate the electrical insulating part green sheet 22a 'to form the positive electrode layer green sheet 20a'. Thereafter, the electrical insulation portion green sheet 22a 'is cut out so as to be disposed on the entire circumference of the quadrilateral outer edge region to prepare the positive electrode layer green substrate 20b'.

  FIG. 4C is a schematic diagram illustrating still another procedure example of the positive electrode layer green substrate preparation step. As shown in FIG. 4C, an electrical insulating part green sheet 22a ″ having a circular notch is formed on a carrier sheet 70. Next, a positive electrode active layer is formed so that the electrical insulating part green sheet 22a ″ is embedded and integrated. The material part green sheet 21a is laminated to form the positive electrode layer green sheet 20a ". After that, the electric insulation part green sheet 22a" is cut out so as to be disposed on the entire circumference of the circular outer edge region. A layer green substrate 20b "is prepared.

  In addition, regarding the in-plane width of the electrical insulating part green sheets 22a, 22a ′, 22a ″ disposed in the positive electrode layer green substrates 20b, 20b ′, 20b ″, the amount of sintering shrinkage of each green substrate in the subsequent firing step From the above, the positive electrode layer and the negative electrode layer sandwiching the current collector may be appropriately set so as not to be short-circuited.

  The positive electrode active material part green sheet 21a includes at least a positive electrode active material as a main component and a resin binder as a shape maintaining component. The green sheet 21a preferably further includes a sintering aid from the viewpoint of improving the sinterability between the positive electrode active material particles in the firing step, and from the viewpoint of improving the conductivity of the positive electrode active material part. It is preferable to further contain an agent.

The positive electrode active material is a crystalline material that releases lithium ions during charging and occludes lithium ions during discharge, and a positive electrode active material used in a conventional lithium ion secondary battery can be used. For example, a lithium transition metal composite oxide is preferable, and specific examples include LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiMnO ₃ , LiMn ₂ O ₃ , LiMnO ₂ , Li ₄ Mn ₅ O ₁₂ , Li ₂ Mn ₃ MO ₈ (M = Fe, Co, Ni, Cu, Zn), Li _1-x M _x Mn ₂ O ₄ (M = Mg, B, Al, Fe, Co, Ni, Cr, Zn, Ca, x = 0.01 ~ 0.1), LiMn _2-x M _x O ₂ (M = Co, Ni, Fe, Cr, Zn, Ta, x = 0.01 to 0.2), LiCo _1-x M _x O ₂ (M = Ni, Fe, Mn, x = 0.01 to 0.2), LiNi _1-x M _x O ₂ (M = Mn, Fe, Co, Al, Ga, Ca, Mg, x = 0.01 to 0.2), LiNi _1-xy Mn _x Co _y O ₂ ( x = 0.1 to 0.8, y = 0.1 to 0.8, x + y = 0.1 to 0.9), LiFeO ₂ , LiFePO ₄ , LiMnPO _{4 and the} like.

The sintering aid is a material for assisting the sintering joining in the positive electrode layer, the positive electrode layer-current collector layer, and the positive electrode layer-solid electrolyte layer, and has easy bondability and good ionic conductivity. It is preferable. For example, B ₂ O ₃ , Li ₃ PO ₄ , Li ₃ BO ₃ , a glass material based on one of these, and a solid electrolyte material can be preferably used.

The conductive auxiliary agent is a material for assisting conductivity in the positive electrode layer and between the positive electrode layer and the current collector layer, and preferably has better electronic conductivity than the positive electrode active material. For example, conductive fibers (vapor-grown carbon, carbon nanotubes, fibers produced by carbonizing pitch at a high temperature and carbon fibers produced from acrylic fibers, etc.) are preferably used. In addition, conductive materials that do not oxidize at the charge / discharge potential of the battery (usually 2.5 to 4.5 V) (for example, corrosion-resistant metals (such as titanium and gold), oxides (such as indium tin oxide, SnO, and ZnO), and carbides (SiC and WC) Etc.), nitrides (such as Si ₃ N ₄ and BN)) and carbon materials having a high specific surface area (such as carbon black and activated carbon) may be used.

  The resin binder is a material for maintaining the shape of the green sheet 21a, and is not particularly limited as long as it does not hinder the sintered joining of each layer in the firing step. For example, polyvinyl butyral (PVB) and ethyl cellulose (EC) can be suitably used. Moreover, you may further mix a plasticizer (for example, dioctyl phthalate: DOP) as needed.

  The electrical insulating part green sheet 22a includes at least an electrical insulating material as a main component and a resin binder as a shape maintaining component. The green sheet 22a preferably further includes a sintering aid from the viewpoint of improving the sinterability between the electrically insulating material particles in the firing step.

  In addition, the description regarding the electrical insulation part green sheet 22a is the same also about the electrical insulation part green sheet 22a ', 22a ".

As an electrically insulating material, an oxide material that is electrically insulating (10 ¹² Ωcm or more) at the charge / discharge potential of the battery (usually 2.5 to 4.5 V) and that does not burn out or flow out in the firing process (eg, 800 ° C.) If there is no particular limitation, for example, silica glass can be suitably used.

  The sintering aid for the green sheet 22a is a material that is electrically insulative at the charge / discharge potential of the battery and that will not be burned out or lost in the firing process, as well as an easily insulating material. preferable. For example, silica gel can be suitably used.

  As the resin binder of the green sheet 22a, PVB or EC can be suitably used as in the case of the green sheet 21a. Moreover, you may further mix a plasticizer (for example, DOP) as needed.

  The positive electrode layer green substrate 20b is a composite of the positive electrode active material part 21b and the electrical insulating part 22b, and each contains a resin component (resin binder, plasticizer). The rate shrinks by firing. In order to prevent the sintered body from cracking or peeling during firing shrinkage, it is necessary to control the firing shrinkage amount between the positive electrode active material portion 21b and the electrical insulating portion 22b so as not to cause a large difference. is there.

  The description regarding the positive electrode layer green substrate 20b is the same for the positive electrode layer green substrates 20b 'and 20b ".

  Specifically, in the step of forming each green sheet (more precisely, the step of preparing the slurry or paste for forming the green sheet), the total of the inorganic material component and the resin component in the slurry or paste The content of the inorganic material component (strictly speaking, it is the volume content, but the mass content after considering the specific gravity as a manufacturing process) is controlled. Hereinafter, the slurry or paste is collectively referred to as a slurry for simplification.

  By controlling the difference between the content of the inorganic material component in the slurry for the positive electrode active material part green sheet 21a and that in the slurry for the electrical insulation part green sheet 22a to within 5%, cracks in the sintered body And the occurrence of peeling can be effectively suppressed. At this time, it is more preferable that the content of the inorganic material component in the slurry for the positive electrode active material part green sheet 21a is equal to or less than the content in the slurry for the electrical insulation part green sheet 22a.

  In addition, among the inorganic material components in the slurry (when the total amount of the inorganic material components is 100%), the content of the main component is preferably 60% or more. By setting the content of the main component to 60% or more, the main component constitutes the aggregate (skeleton) of the sintered body, so that the effective linear expansion coefficient of the sintered body can be controlled. . As a result, it is possible to effectively suppress the occurrence of delamination and cracks due to thermal history and heat cycle. The same applies to the slurry for the other layers. In addition, the remainder (content rate 40% or less) of the inorganic material component in the slurry is composed of a sintering aid and / or a conductive aid.

(Negative electrode layer green substrate preparation process)
This step is a step of preparing a negative electrode layer green substrate 30b by forming a negative electrode layer green sheet and then cutting it into a quadrangular or circular shape of a predetermined size. The negative electrode layer green substrate 30b includes a negative electrode active material portion 31b and an electric insulating portion 32b. In the example of FIG. 2, the electric insulating portion 32b is formed in the opposite side region of the quadrilateral.

  The negative electrode layer green substrate 30b can be prepared in the same procedure as the positive electrode layer green substrate 20b (see FIG. 4A), except that the configuration of the negative electrode active material portion 31b is different from that of the positive electrode active material portion 21b.

  In the negative electrode green substrate having the positive electrode green substrate 20b ′, 20b ″ as a counterpart, the electrical insulating portion is formed by the same procedure as that of the positive electrode green substrate 20b ′, 20b ″ (see FIGS. 4B and 4C). Although the arranged negative electrode layer green board | substrate may be prepared, the negative electrode layer green board | substrate which does not arrange | position an electric insulation part in a board | substrate may be prepared. This is because in the positive electrode layer green substrates 20b 'and 20b ", the electrical insulating portion is arranged on the entire outer periphery of the substrate, thereby preventing an internal short circuit in the bipolar electrode.

  From this point of view, when preparing a negative electrode layer green substrate having an electrical insulating portion arranged around the entire outer edge of the substrate in the same procedure as FIG. 4B and FIG. 4C, You may prepare the positive electrode layer green board | substrate which does not arrange | position an electric insulation part in a board | substrate.

  However, the negative electrode active material portion 31b is the same as that of the negative electrode green substrate 30b in the negative electrode green substrate having the positive electrode green substrate 20b ', 20b "as a pair.

  The negative electrode active material part green sheet includes at least a negative electrode active material as a main component and a resin binder as a shape maintaining component. The green sheet preferably further contains a sintering aid from the viewpoint of improving the sinterability between the negative electrode active material particles in the firing step, and from the viewpoint of improving the conductivity of the negative electrode active material portion, the conductive aid. It is preferable that it is further included.

The negative electrode active material is a crystalline material that occludes lithium ions during charging and releases lithium ions during discharge, and a negative electrode active material used in a conventional lithium ion secondary battery can be used. Specific examples include carbon-based materials (eg, carbon black, graphitizable carbon materials, amorphous carbon materials), lithium transition metal composite oxides (eg, Li ₄ Ti ₅ O ₁₂ , LiTiO ₄ ), lithium transition metals. A composite nitride (for example, LiCoN) can be preferably used. The carbon-based material also functions as a conductive aid.

The sintering aid in the negative electrode active material part green sheet is the same as that in the positive electrode active material part green sheet 21a (for example, B ₂ O ₃ , Li ₃ PO ₄ , Li ₃ BO ₃ , based on one of these. Glass materials and solid electrolyte materials) can be suitably used.

  As the conductive additive in the negative electrode active material part green sheet, metallic lithium powder and powder of metal alloyed with lithium (for example, aluminum, silicon, tin) can be suitably used. Since these metals also function as a negative electrode active material, it is preferable to mix them. Since the linear expansion coefficient of metal is about an order of magnitude larger than that of oxide (in other words, the thermal expansion / contraction of metal is about 10 times larger than that of oxide), the sintered body In order to suppress the occurrence of cracks and peeling, the metal powder is preferably mixed as a conductive aid rather than as a main component of the negative electrode active material part green sheet.

  Regarding the relationship between the content of the inorganic material component in the slurry for the negative electrode active material part green sheet and the content of the inorganic material component in the slurry for the electrical insulation part green sheet, it is the same as that in the positive electrode layer green sheet 20a. is there.

(Current collector layer green substrate preparation process)
This step is a step of preparing the current collector layer green substrate 10b by forming the current collector layer green sheet and then cutting it into a quadrangular or circular shape having a predetermined size. There is no particular limitation on the method of forming the green sheet, and for example, a doctor blade method or a screen printing method can be suitably used. Moreover, there is no special limitation in the cutting-out method of a green substrate, For example, a punching process can be used suitably.

  The current collector layer green sheet includes at least a conductive (electron conductive) substance as a main component and a resin binder as a shape maintaining component. The green sheet preferably further contains a sintering aid from the viewpoint of improving the sinterability between the conductive substance particles in the firing step, and from the viewpoint of improving the conductivity of the current collector layer, the conductive aid. It is preferable that it is further included.

  As the main component of the current collector layer, a carbon-based material (for example, glassy carbon) or a conductive oxide (for example, indium tin oxide, SnO, ZnO) can be suitably used.

  The sintering aid in the current collector layer green sheet is not particularly limited as long as it is a material that is easily sinterable and does not hinder the conductivity of the main component. For example, a conductive glass mainly composed of vanadium oxide. Can be suitably used.

  As the conductive additive in the current collector layer green sheet, powders of highly conductive and corrosion resistant metals (for example, gold, silver, copper, platinum, nickel) can be suitably used. As described above, in order to suppress the occurrence of cracks and peeling in the sintered body, these metal powders are preferably mixed as a conductive aid rather than as a main component of the current collector layer green sheet.

  As described above, in the present invention, it is preferable to control the firing shrinkage amount of the current collector layer to be larger than those of the positive electrode layer and the negative electrode layer in the firing step. Therefore, in the slurry forming the current collector layer green sheet, the content of the inorganic material component relative to the sum of the inorganic material component and the resin component (resin binder, plasticizer) in the slurry is determined as the positive electrode layer or negative electrode layer electrode. It is preferable that the difference is within 5% below the content in the slurry for the active material part green sheet. By doing so, the occurrence of cracks and delamination in the sintered body can be effectively suppressed, and an internal short circuit of the battery can be effectively prevented.

(Solid electrolyte layer green substrate preparation process)
This step is a step of preparing a solid electrolyte layer green substrate 40b by forming a solid electrolyte layer green sheet and then cutting it into a quadrangular or circular shape of a predetermined size. There is no particular limitation on the method of forming the green sheet, and for example, a doctor blade method or a screen printing method can be suitably used. Moreover, there is no special limitation in the cutting-out method of a green substrate, For example, a punching process can be used suitably.

  The solid electrolyte layer green sheet includes at least a solid electrolyte as a main component and a resin binder as a shape maintaining component. The green sheet preferably further contains a sintering aid from the viewpoint of improving the sinterability between the solid electrolyte particles in the firing step.

As long as the solid electrolyte has high ion conductivity and heat resistance suitable for the firing step, the solid electrolyte of the conventional all-solid lithium secondary battery can be used. For example, a lithium composite oxide is preferable, and specific examples include a garnet-type lithium composite oxide (for example, Li ₇ La ₃ Zr ₂ O ₁₂ , Li _{7 + x} La ₃ Zr ₂ O _12−x M _x (0 <x <1.2 , M is N, Cl, S, or Se), Li ₅ La ₃ Ta ₂ O ₁₂ , Li ₅ La ₃ Nb ₂ O ₁₂ , Li ₆ BaLa ₂ Ta ₂ O ₁₂ ), perovskite-type lithium composite oxide ( For example, Li _0.34 La _0.51 TiO _2.94 ), NASICON type lithium composite oxide (eg, Li _1.1 Al _0.7 Ti _1.5 (PO ₄ ) ₃ ), glass type lithium composite oxide (eg, 50Li ₄ SiO ₄ -50Li ₃ BO ₃ , Li _1.07 Al _0.69 Ti _1.46 (PO ₄ ) ₃ , Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ , Li _1.4 Al _0.4 Ti _1.6 (PO ₄ ) ₃ , LiAlGe (PO ₄ ) ₃ , Li ₃ BO ₃ , LiVO ₃ , Li _3.4 V _0.6 Si _0.4 O ₄ , Li ₂ P ₂ O ₆ ) and the like. These solid electrolytes may be used alone or in combination of two or more.

The sintering aid in the solid electrolyte layer green sheet is the same as that in the positive electrode active material part green sheet 21a (for example, B ₂ O ₃ , Li ₃ PO ₄ , Li ₃ BO ₃ , based on one of these. Glass material) can be suitably used.

  In the slurry for forming the solid electrolyte layer green sheet, the content of the inorganic material component with respect to the sum of the inorganic material component and the resin component in the slurry is determined in the slurry for the electrode active material part green sheet of the positive electrode layer or the negative electrode layer. It is preferable to adjust so that the difference in content is within 5%. By doing so, the occurrence of cracks and delamination in the sintered body can be effectively suppressed, and an internal short circuit of the battery can be effectively prevented.

  In the following description, the embodiment shown in FIGS.

(All-solid battery green substrate laminate formation process)
In this step, the all-solid-state battery green substrate laminate 100b is formed from the current collector layer green substrate 10b, the positive electrode layer green substrate 20b, the negative electrode layer green substrate 30b, and the solid electrolyte layer green substrate 40b prepared in each of the above steps. It is a process. In forming the all-solid-state battery green substrate laminate 100b as shown in FIG. 2, each layer green substrate may be sequentially laminated. As shown below, an electrode green substrate (bipolar electrode green substrate 50b, positive monopolar The electrode green substrate 61b and the negative monopolar electrode green substrate 65b) may be formed in advance.

(A) Bipolar Electrode Green Substrate Formation Step This step is a step of forming a bipolar electrode green substrate 50b from the current collector layer green substrate 10b, the positive electrode layer green substrate 20b, and the negative electrode layer green substrate 30b. At this time, as shown in FIG. 2, the current collector layer green substrate 10b is laminated so that the electrical insulating portion 22b in the positive electrode green substrate 20b faces one main surface, and the negative electrode layer is formed on the other main surface. The green substrate 30b is laminated so that the electrical insulating portions 32b face each other. Furthermore, when viewed from the stacking direction, the electrical insulation portion 22b in the positive electrode layer green substrate 20b is disposed in a pair of opposite sides of the quadrilateral, and the electrical insulation portion 32b in the negative electrode layer green substrate 30b is the other of the quadrilateral shape. Lamination is performed so as to be arranged in a pair of opposite side regions.

(B) Positive monopolar electrode green substrate forming step This step is a step of forming the positive monopolar electrode green substrate 61b from the current collector layer green substrate 10b and the positive electrode layer green substrate 20b. A positive electrode layer green substrate 20b is laminated on the main surface. In FIG. 2, the positive layer green substrate 20b of the positive monopolar electrode green substrate 61b has an electrical insulating portion 22b. By using the positive electrode layer green substrate 20b prepared in the positive electrode layer green substrate preparation step, there is no need to prepare another step, and thus there is an advantage that the process cost as a whole can be reduced. However, the present invention is not limited thereto, and the positive electrode layer green substrate in the positive monopolar electrode green substrate may not have the electrical insulating portion 22b.

(C) Negative Monopolar Electrode Green Substrate Formation Step This step is a step of forming the negative monopolar electrode green substrate 65b from the current collector layer green substrate 10b and the negative electrode layer green substrate 30b. A negative electrode layer green substrate 30b is laminated on the main surface of the substrate. As in the case of the positive monopolar electrode green substrate 61b, the negative monopolar electrode green substrate 65b may or may not include the electrical insulating portion 32b in the negative electrode green substrate 30b. By using the negative electrode layer green substrate 30b prepared in the negative electrode layer green substrate preparation step, there is no need to prepare another step, which has an advantage of reducing the overall process cost.

(D) Laminate assembly process In this step, the bipolar electrode green substrate 50b and the solid electrolyte layer green substrate 40b are alternately laminated, and the bipolar electrode green substrate-solid electrolyte layer green substrate laminate is aligned at both ends in the stacking direction. In this step, the monopolar electrode green substrate 61b and the negative monopolar electrode green substrate 65b are laminated. When forming the all-solid-state battery green substrate laminate 100b, it is preferable to apply moderate pressure. For example, a cold isostatic press (CIP) or a warm isostatic press (WIP) may be used. .

(All-solid-state battery green substrate laminate firing process)
This step is performed by firing the whole solid battery green substrate laminate 100b, and sintering the solid layers of the negative electrode layer 30c, the current collector layer 10c, the positive electrode layer 20c, and the solid electrolyte layer 40c. This is a step of forming the bonded assembly 100c. As the firing process, after the step of burning off the resin component contained in each green substrate (for example, heating at 600 ° C. in the air atmosphere), the step of sintering the inorganic material component constituting each green substrate (for example, non-step) It is preferable to perform heating at 800 ° C. in an oxidizing atmosphere. Moreover, in order to promote the sintering joining between each layer, it is preferable to apply moderate pressure during firing.

  As described above, in the present invention, the surface of the electrical insulating portion 22b in the positive electrode layer green substrate 20b and the surface of the electrical insulating portion 32b in the negative electrode layer green substrate 30b are calculated backward from the sintering shrinkage amount of each green substrate in the firing step. Since the inner width is set, a short circuit between the positive electrode layer 20c and the negative electrode layer 30c sandwiching the current collector 10c can be prevented even after the firing step.

  By passing through the above process, the all-solid-state battery sintered joined body 100c which has the structure which prevents an internal short circuit, and which carried out integral high temperature baking of the whole bipolar laminated body is obtained. Thereafter, a bipolar laminated all solid lithium secondary battery is obtained through an external terminal connection process and a packaging process.

(External terminal connection process)
This step is a step of connecting an external terminal to the positive monopolar electrode and the negative monopolar electrode of the all-solid battery sintered assembly. FIG. 5 is a schematic longitudinal sectional view showing an example of the all solid state battery structure obtained by the external terminal connecting step. As shown in FIG. 5, the positive electrode external terminal 62 and the negative electrode external terminal 66 are connected to the current collector layer 10c of the positive monopolar electrode 61c and the current collector layer 10c of the negative monopolar electrode 65c via the bonding layer 80, respectively. The all-solid battery structure 100d is formed by bonding.

  There is no particular limitation on the positive electrode external terminal 62 and the negative electrode external terminal 66, and a highly conductive metal (for example, copper, nickel, aluminum) can be suitably used. Further, the material of the bonding layer 80 is not particularly limited, and a material (for example, silver paste or solder) that can electrically bond the highly conductive metal of the external terminal and the constituent material of the current collector layer 10c well. It can be used suitably.

(Packaging process)
This step is a step of packaging the all-solid battery structure 100d for protection and external insulation of the all-solid battery structure 100d. FIG. 6 is a schematic longitudinal sectional view showing an example of an all solid state battery obtained by the packaging process. As shown in FIG. 6, the other part of the all-solid-state battery structure 100d is electrically insulated packaging material so that a part of the positive external terminal 62 and a part of the negative external terminal 66 protrude to the outside. Sealing with 90 (for example, resin material, glass material) to form a bipolar laminated all solid lithium secondary battery 100e.

  By undergoing the above steps, the bipolar laminated all solid lithium secondary battery according to the present invention can be obtained.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited to the Example here.

[Preparation of Bipolar Laminated All Solid Lithium Secondary Battery of Example 1]
(1) Preparation of slurry for positive electrode active material part green sheet Using 75 parts by mass of LiCoO ₂ as a positive electrode active material, using 25 parts by mass of Li ₃ BO ₃ as a sintering aid, and 1 part by mass of a conductive aid Carbon black was used, 10 parts by weight of ethyl cellulose (EC) was used as a resin binder, and 10 parts by weight of dioctyl phthalate (DOP) was used as a plasticizer. They were put into a ball mill, and 100 parts by mass of acetone was added as a solvent and mixed well. The obtained mixed solution was degassed under reduced pressure and part of the solvent was volatilized to prepare a positive electrode active material part green sheet slurry (viscosity: about 10,000 mPa · s).

(2) Preparation of slurry for electrical insulation part green sheet Using 75 parts by mass of silica glass as an electrical insulation material, using 25 parts by mass of silica gel as a sintering aid, using 7 parts by mass of EC as a resin binder, 10 parts by mass of DOP was used as a plasticizer. They were put into a ball mill, and 100 parts by mass of acetone was added as a solvent and mixed well. The obtained mixed solution was degassed under reduced pressure and part of the solvent was volatilized to prepare a slurry for an electrical insulating part green sheet (viscosity: about 10,000 mPa · s).

(3) Preparation of slurry for negative electrode active material part green sheet Use 75 parts by mass of Li ₄ Ti ₅ O ₁₂ as negative electrode active material, use 25 parts by mass of Li ₃ BO ₃ as sintering aid, and use as conductive aid 1 part by weight of carbon black was used, 10 parts by weight of EC was used as a resin binder, and 10 parts by weight of DOP was used as a plasticizer. They were put into a ball mill, and 100 parts by mass of acetone was added as a solvent and mixed well. The obtained mixed solution was degassed under reduced pressure and part of the solvent was volatilized to prepare a negative electrode active material part green sheet slurry (viscosity: about 10,000 mPa · s).

(4) Production of positive electrode layer green substrate and negative electrode layer green substrate A positive electrode layer green substrate and a negative electrode layer green substrate were produced according to the procedure shown in FIG. 4A. First, using the slurry for electrical insulation green sheet prepared above, parallel to a polyethylene terephthalate (PET) carrier sheet by the doctor blade method using a doctor blade with a width of 60 mm with 10 mm notches at both ends. A pair of electrical insulating part green sheets (width 10 mm, interval 40 mm, thickness 20 μm) was formed (see FIG. 4A (a)). Thereafter, the parallel pair of electrically insulating part green sheets was divided into two together with the carrier sheet so as to be used for the positive electrode layer and the negative electrode layer.

  Next, the positive electrode active material part green sheet slurry prepared above is used and the positive electrode active material part green sheet is embedded and integrated by a doctor blade method using a doctor blade having a width of 60 mm. The material part green sheet was laminated to form a positive electrode layer green sheet (width 60 mm, thickness 70 μm) (see FIG. 4A (b)).

  Next, the positive electrode layer green sheet is punched into the positive electrode layer green so that a pair of parallel electrical insulation green sheets are arranged in a width of 5 mm in the opposite sides of the quadrilateral (one side of 50 mm). A substrate (50 mm square, 70 μm thick) was produced (see FIG. 4A (c)).

  Similarly to the positive electrode layer green substrate, a negative electrode layer green substrate (50 mm square, thickness 70 μm) was prepared using the slurry for the electrical insulating portion green sheet and the slurry for the negative electrode active material portion green sheet.

(5) Production of current collector layer green substrate 75 parts by mass of indium tin oxide (ITO) is used as the conductive material, 5 parts by mass of vanadium-based conductive glass is used as the sintering aid, and 23 as the conductive aid. Part by weight of silver was used, 10 parts by weight of PVB was used as a resin binder, and 12 parts by weight of DOP was used as a plasticizer. They were put into a ball mill, and 100 parts by mass of acetone was added as a solvent and mixed well. The obtained mixed solution was degassed under reduced pressure and part of the solvent was volatilized to prepare a current collector layer green sheet slurry (viscosity: about 10,000 mPa · s).

  Using the slurry for the collector layer green sheet prepared above, the collector layer green sheet (width 60 mm, thickness 50 μm) on the PET carrier sheet by the doctor blade method using a doctor blade with a width of 60 mm Formed. Thereafter, the current collector layer green sheet was punched to produce a current collector layer green substrate (50 mm square, thickness 50 μm).

(6) Production of solid electrolyte layer green substrate 75 parts by mass of Li ₇ La ₃ Zr ₂ O ₁₂ as a solid electrolyte, 30 parts by mass of Li ₃ BO ₃ as a sintering aid, and 10 parts by mass as a resin binder 10 parts by weight of DOP was used as a plasticizer. They were put into a ball mill, and 100 parts by mass of acetone was added as a solvent and mixed well. The resulting mixed solution was subjected to degassing under reduced pressure and partial volatilization of the solvent to prepare a solid electrolyte layer green sheet slurry (viscosity: about 10,000 mPa · s).

  Using the solid electrolyte layer green sheet slurry prepared above, a solid electrolyte layer green sheet (width 60 mm, thickness 100 μm) is formed on a PET carrier sheet by the doctor blade method using a doctor blade with a width of 60 mm. did. Thereafter, the solid electrolyte layer green sheet was punched into a solid electrolyte layer green substrate (50 mm square, thickness 100 μm).

(7) Production of all-solid-state battery green substrate laminate Using the positive electrode layer green substrate, negative electrode layer green substrate, current collector layer green substrate, and solid electrolyte layer green substrate prepared above, the structure shown in FIG. It was laminated so as to be. Thereafter, a warm isostatic press (temperature: 90 ° C., pressure: 40 MPa) was applied to the laminate and pressure-bonded to produce an all-solid battery green substrate laminate.

(8) Production of all-solid battery sintered joined body A firing process was performed on the all-solid battery green substrate laminate produced above to produce an all-solid battery sintered joined body. The firing condition is that the all-solid-state battery green substrate laminate is sandwiched between two alumina ceramic plates and held in an air atmosphere at 600 ° C. for 2 hours to burn off the resin components and then in a nitrogen gas atmosphere at 800 ° C. For 2 hours, and heat treatment was performed to sinter-bond the inorganic material components.

(9) Connection of external terminals For the positive monopolar electrode and negative monopolar electrode of the all-solid battery sintered assembly produced above, the positive external terminal and the negative external terminal of the nickel foil are respectively connected via the bonding layer of silver paste. Pasted together. Thereafter, heating was performed at 120 ° C. in an air atmosphere to ensure electrical connection between the monopolar electrode and the external terminal.

  Through the above steps, a bipolar laminated all solid lithium secondary battery (for test evaluation) of Example 1 was produced. In order to facilitate observation after the charge / discharge test, the all-solid battery structure was not packaged.

[Preparation of Bipolar Laminated All Solid Lithium Secondary Battery of Example 2]
A bipolar stacked all-solid lithium secondary battery (for test evaluation) of Example 2 was produced in the same manner as in Example 1 except that the arrangement of the electrical insulating portion on the positive electrode layer green substrate was changed to the embodiment of FIG. 4B. . Only differences from the first embodiment will be described below.

(10) Production of positive electrode layer green substrate and negative electrode layer green substrate A positive electrode layer green substrate was produced according to the procedure shown in FIG. 4B. First, the same electrical insulating part green sheet slurry as in Example 1 was used, and the electrical insulating part green sheet having a 40 mm square notch on the PET carrier sheet by screen printing using a screen plate having a metal mesh. (Whole width 60 mm, thickness 20 μm) was formed (see FIG. 4B (a)).

  Next, using the same positive electrode active material part green sheet slurry as in Example 1, the electrical insulating part green sheet having a 40 mm square notch was embedded by the doctor blade method using a doctor blade having a width of 60 mm. The positive electrode active material part green sheet was laminated so as to form a positive electrode layer green sheet (width 60 mm, thickness 70 μm) (see FIG. 4B (b)).

  Next, the positive electrode layer green sheet is punched into the positive electrode layer green substrate so that the electric insulation portion green sheet is arranged with a width of 5 mm around the outer edge region of the quadrilateral (side 50 mm). 50 mm square and 70 μm thickness) were produced (see FIG. 4B (c)).

  On the other hand, for the negative electrode layer green substrate, first, the negative electrode active material part green sheet slurry as in Example 1 was used, and the negative electrode layer green sheet (width 60 mm, A thickness of 70 μm) was formed. The electrical insulation part green sheet was not formed.

  Next, the negative electrode layer green sheet was punched to prepare a negative electrode layer green substrate (50 mm square, thickness 70 μm). That is, a negative electrode layer green substrate having no electrical insulating portion was produced.

[Preparation of Bipolar Laminated All Solid Lithium Secondary Battery of Example 3]
The bipolar laminated all solid-state lithium battery of Example 3 is the same as Example 1 except that the arrangement of the electrical insulating portion in the negative electrode layer green substrate is the embodiment of FIG. 4C and the shape of each green substrate is circular. A secondary battery (for test evaluation) was produced. Only differences from the first embodiment will be described below.

(11) Production of positive electrode layer green substrate and negative electrode layer green substrate A negative electrode layer green substrate was produced according to the procedure shown in FIG. 4C. First, using the same electrical insulating part green sheet slurry as in Example 1 and using a screen printing method using a screen plate having a metal mesh, an electrical insulating part having a circular notch with a diameter of 40 mm on a PET carrier sheet. A green sheet (whole width 60 mm, thickness 20 μm) was formed (see FIG. 4C (a)).

  Next, by using the same negative electrode active material part green sheet slurry as in Example 1 and a doctor blade method using a doctor blade having a width of 60 mm, the electrical insulating part green sheet having a circular notch with a diameter of 40 mm was obtained. A negative electrode active material part green sheet was laminated so as to be embedded and integrated to form a negative electrode layer green sheet (width 60 mm, thickness 70 μm) (see FIG. 4C (b)).

  Next, the negative electrode layer green sheet (diameter) is punched into the negative electrode layer green sheet so that the electric insulation part green sheet is arranged with a width of 5 mm around the entire outer edge region of the circle (diameter 50 mm). 50 mm and a thickness of 70 μm) (see FIG. 4C (c)).

  On the other hand, for the positive electrode layer green substrate, first, the positive electrode active material part green sheet slurry as in Example 1 was used, and the positive electrode layer green sheet (width 60 mm, A thickness of 70 μm) was formed. The electrical insulation part green sheet was not formed.

  Next, the positive electrode layer green sheet was punched to prepare a positive electrode layer green substrate (diameter 50 mm, thickness 70 μm). That is, a positive electrode layer green substrate having no electrical insulating portion was produced.

(12) Preparation of current collector layer green substrate and solid electrolyte layer green substrate Current collector layer green substrate (diameter) in the same manner as in Example 1 except that the punching shape was circular (diameter 50 mm). 50 mm, thickness 50 μm) and a solid electrolyte layer green substrate (diameter 50 mm, thickness 100 μm).

[Preparation of Bipolar Laminated All Solid Lithium Secondary Battery of Comparative Example 1]
A bipolar laminated all solid lithium secondary battery (for test evaluation) of Comparative Example 1 was prepared in the same manner as in Example 1 except that a positive electrode layer green substrate and a negative electrode layer green substrate having no electrical insulating portion were prepared and used. Produced.

[Preparation of Bipolar Multilayer All Solid Lithium Secondary Battery of Comparative Example 2]
A bipolar laminated all solid lithium secondary battery (for test evaluation) of Comparative Example 2 was produced in the same manner as in Example 1 except that a silver sheet (thickness: 50 μm) was used as the current collector layer.

[All-solid-state battery test evaluation]
Constant current constant voltage charge / discharge test (voltage range: 3.0 to 5.5 V, current density: 100 μA / cm) for the bipolar laminated all solid lithium secondary batteries of Examples 1 to 3 and Comparative Examples 1 and 2 prepared above. ² ) went. As a result, it was confirmed that the secondary batteries of Examples 1 to 3 had the charge / discharge characteristics (electric capacity, charge / discharge rate) as designed. This indicates that an internal short circuit is prevented and that the electrical connection between the layers constituting the secondary battery is sufficiently ensured. In addition, the present invention is also effective when the arrangement of the electrical insulating portions and the shape of each layer are changed.

  On the other hand, in the secondary battery of Comparative Example 1, the electric capacity was significantly lower than the design value. When the secondary battery after the test was closely observed, an internal short-circuited portion was observed between the positive electrode layer and the negative electrode layer at the end of the bipolar electrode. From this, it was considered that Comparative Example 1 using the positive electrode layer and the negative electrode layer that did not have an electrical insulating portion had a reduced electric capacity due to an internal short circuit of the battery.

  Moreover, the secondary battery of Comparative Example 2 was difficult to charge and discharge at the current density. When the secondary battery after the test was closely observed, a portion where peeling occurred between the current collector layer and the positive electrode layer or between the current collector layer and the negative electrode layer was observed. In Comparative Example 2 using a metal sheet as the current collector layer, the firing shrinkage behavior is greatly different between the current collector layer and the other layers (the current collector layer made of the metal sheet expands when the temperature rises). Shrinks when the temperature drops and returns to the original dimensions, but the other layers (positive layer, negative layer, solid electrolyte layer) shrink more than the green substrate by firing), causing delamination during the firing process, It was thought that sufficient electrical bondability could not be secured.

  The above-described embodiments and examples are described in order to facilitate understanding of the present invention, and the present invention is not limited to the specific configurations described. For example, it is possible to replace a part of the configuration of the embodiment with the configuration of common technical knowledge of those skilled in the art, and it is also possible to add the configuration of technical common sense of those skilled in the art to the configuration of the embodiment. That is, according to the present invention, a part of the configurations of the embodiments and examples of the present specification can be deleted, replaced with other configurations, and added with other configurations without departing from the technical idea of the invention. Is possible.

10b ... current collector layer green substrate, 10c ... current collector layer,
20a ... positive electrode layer green sheet, 20b ... positive electrode layer green substrate, 20c ... positive electrode layer,
21a ... cathode active material part green sheet, 21b ... cathode active material part,
22a ... Electric insulation part green sheet, 22b ... Electrical insulation part,
30b ... negative electrode layer green substrate, 30c ... negative electrode layer,
31b ... negative electrode active material part, 32b ... electrical insulation part,
40b ... Solid electrolyte layer green substrate, 40c ... Solid electrolyte layer,
50b ... Bipolar electrode green substrate, 50c ... Bipolar electrode,
61b ... Positive monopolar electrode green substrate, 61c ... Positive monopolar electrode, 62 ... Positive external terminal,
65b ... negative monopolar electrode green substrate, 65c ... negative monopolar electrode, 66 ... negative external terminal,
70 ... carrier sheet, 80 ... bonding layer, 90 ... packaging material,
100b ... all solid battery green substrate laminate, 100c ... all solid battery sintered joint,
100d: All-solid battery structure, 100e: Bipolar laminated all-solid lithium secondary battery.

Claims (8)

A bipolar laminated all solid lithium secondary battery in which bipolar electrodes and solid electrolyte layers are alternately laminated,
The bipolar electrode includes a current collector layer, a positive electrode layer formed on one main surface of the current collector layer, and a negative electrode layer formed on the other main surface of the current collector layer. Consists of
When viewed from the stacking direction, each of the bipolar electrode and the solid electrolyte layer has a quadrangular or circular shape, and the current collector layer has an outer edge inside the outer edges of the positive electrode layer and the negative electrode layer. Yes,
The positive electrode layer and / or the negative electrode layer in the bipolar electrode includes an electrical insulating portion in an outer edge region of the quadrilateral or the circle on a surface in contact with the current collector layer, and the bipolar electrode is disposed in the stacking direction. When viewed from the projection of the electrical insulation portion constitutes the entire circumference of the quadrilateral or the circular outer edge,
The bipolar laminated all solid lithium secondary battery, wherein the bipolar electrode and the solid electrolyte layer form a sintered joined body. In the bipolar laminated all solid lithium secondary battery according to claim 1,
When viewed from the stacking direction, each of the bipolar electrode and the solid electrolyte layer has a quadrilateral shape, and the electrical insulating portion of the positive electrode layer is disposed in a pair of opposite side regions of the quadrilateral, The bipolar laminated all solid lithium secondary battery, wherein the electrical insulating portion is disposed in another pair of opposite side regions of the quadrilateral. In the bipolar laminated all solid lithium secondary battery according to claim 1 or 2,
The current collector layer is mainly composed of a carbon-based material and / or a conductive oxide,
The positive electrode layer is mainly composed of a lithium transition metal composite oxide,
The negative electrode layer is mainly composed of a carbon-based material, a lithium transition metal composite oxide and / or a lithium transition metal composite nitride,
The bipolar electrolyte type all-solid lithium secondary battery, wherein the solid electrolyte layer is mainly composed of a lithium composite oxide electrolyte. A bipolar laminated all solid lithium secondary battery manufacturing method in which bipolar electrodes and solid electrolyte layers are alternately laminated,
The bipolar electrode includes a current collector layer, a positive electrode layer formed on one main surface of the current collector layer, and a negative electrode layer formed on the other main surface of the current collector layer. Consists of
When viewed from the stacking direction, each of the bipolar electrode and the solid electrolyte layer has a quadrangular or circular shape, and the current collector layer has an outer edge inside the outer edges of the positive electrode layer and the negative electrode layer. Is formed to be
The positive electrode layer and / or the negative electrode layer in the bipolar electrode includes an electrical insulating portion in an outer edge region of the quadrilateral or the circle on a surface in contact with the current collector layer, and the bipolar electrode is disposed in the stacking direction. When viewed from the projection of the electrical insulation portion constitutes the entire circumference of the quadrilateral or the circular outer edge,
A current collector layer green in which a current collector layer green sheet containing a main component of the current collector layer and a resin binder is formed and then cut into a quadrilateral or circular shape of a predetermined size to prepare a current collector layer green substrate Substrate preparation process;
A positive electrode layer green substrate preparation step of preparing a positive electrode layer green substrate by cutting out into a quadrangular or circular shape of a predetermined dimension after forming a positive electrode layer green sheet containing the main component of the positive electrode layer and a resin binder;
A negative electrode layer green substrate preparation step of preparing a negative electrode layer green substrate by cutting out into a quadrangular or circular shape of a predetermined dimension after forming a negative electrode layer green sheet containing the main component of the negative electrode layer and a resin binder,
A solid electrolyte layer green substrate preparation step of preparing a solid electrolyte layer green substrate by forming a solid electrolyte layer green sheet containing a main component of the solid electrolyte layer and a resin binder and then cutting into a quadrilateral or circular shape of a predetermined size; ,
The negative electrode layer green substrate, the current collector layer green substrate, the positive electrode layer green substrate, and the solid electrolyte layer green substrate prepared in each of the above steps are sequentially stacked to form an all-solid battery green substrate stack. A solid battery green substrate laminate forming step;
An all-solid battery sintered assembly obtained by firing the whole solid battery green substrate laminate and sintering and bonding the negative electrode layer, the current collector layer, the positive electrode layer, and the solid electrolyte layer. An all solid state battery green substrate laminate firing step to form,
In the positive electrode layer green substrate preparation step and / or the negative electrode layer green substrate preparation step, after forming an electrical insulation part green sheet to be the electrical insulation part, the positive electrode active green part is embedded and integrated. The positive electrode layer green sheet and / or the negative electrode layer green sheet are formed by laminating the material part green sheet and / or the negative electrode active material part green sheet, and then the electric insulating part based on the electric insulating part green sheet Is a process of cutting so as to be arranged in the quadrilateral or circular outer edge region,
The all-solid-state battery green substrate laminate forming step includes laminating the positive electrode layer green substrate on one main surface of the current collector layer green substrate and laminating the negative electrode layer green substrate on the other main surface. A bipolar electrode green substrate forming step of forming a bipolar electrode green substrate, wherein the bipolar electrode green substrate forming step includes the step of forming the current collector in the positive electrode green substrate and / or in the negative electrode green substrate. The positive electrode green layer so that the projection of the electric insulation portion forms the entire circumference of the quadrilateral or the circular outer edge when facing the layer green substrate and viewing the bipolar electrode green substrate from the stacking direction. Bipolar laminated all solid, characterized in that it is a step of laminating a substrate and the negative electrode layer green substrate on the current collector layer green substrate Method of manufacturing a lithium secondary battery. In the manufacturing method of the bipolar laminated all solid lithium secondary battery according to claim 4,
When viewed from the stacking direction, each of the bipolar electrode and the solid electrolyte layer has a quadrangular shape,
In the bipolar electrode green substrate forming step, when viewed from the stacking direction, the electrical insulating portion in the positive electrode layer green substrate is disposed in a pair of opposite side regions of the quadrilateral, and the positive electrode layer green substrate in the negative electrode layer green substrate It is a step of laminating the positive electrode layer green substrate and the negative electrode layer green substrate on the current collector layer green substrate so that an electrical insulating portion is disposed in another pair of opposite side regions of the quadrilateral. A method for manufacturing a bipolar laminated all solid lithium secondary battery. In the manufacturing method of the bipolar laminated all solid lithium secondary battery according to claim 4 or 5,
In the current collector layer green substrate preparation step, the current collector layer green substrate contracts more than the positive electrode layer green substrate and the negative electrode layer green substrate in the all solid state battery green substrate laminate firing step. Thus, the manufacturing method of the bipolar lamination type all-solid-state lithium secondary battery characterized by being the process of adjusting a collector layer slurry and forming the said collector layer green sheet. In the manufacturing method of the bipolar laminated type all solid lithium secondary battery according to any one of claims 4 to 6,
The all solid state battery green substrate laminate forming step includes:
A positive monopolar electrode green substrate forming step of forming the positive monopolar electrode green substrate by laminating the positive electrode layer green substrate on one main surface of the current collector layer green substrate;
A negative monopolar electrode green substrate forming step of forming the negative monopolar electrode green substrate by laminating the negative electrode layer green substrate on one main surface of the current collector layer green substrate;
The bipolar electrode green substrate and the solid electrolyte layer green substrate are alternately laminated, and the positive monopolar electrode green substrate and the negative monopolar electrode green are disposed at both ends in the lamination direction of the bipolar electrode green substrate-solid electrolyte layer green substrate laminate. A method for manufacturing a bipolar stacked type all solid lithium secondary battery, further comprising a stacked body assembly step of stacking the substrates. In the manufacturing method of the bipolar laminated type all solid lithium secondary battery according to any one of claims 4 to 7,
The main component of the current collector layer is made of a carbon-based material and / or a conductive oxide,
The main component of the positive electrode layer is composed of a lithium transition metal composite oxide,
The main component of the negative electrode layer is composed of a carbon-based material, a lithium transition metal composite oxide and / or a lithium transition metal composite nitride,
The main component of the solid electrolyte layer is made of a lithium composite oxide electrolyte, and the method for producing a bipolar laminated all solid lithium secondary battery.

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