Stacked solid-state battery unit and method for manufacturing the same

Abstract

To provide a laminated solid-state battery unit with a reference electrode, having such a structure that potential separation and resistance separation are less likely to occur between the reference electrode and a positive or negative electrode.SOLUTION: A laminated solid-state battery 10 has a flat positive electrode layer 2, an electrolyte layer 5, and a negative electrode layer 4 having a dimension larger than that of the positive electrode layer 2, in this order. The electrolyte layer 5 has a first electrolyte layer 51 at the positive electrode layer side and a second electrolyte layer 52 at the negative electrode side, and has a crimp region P where the first electrolyte layer 51 and the second electrolyte layer 52 are crimped and a non-crimp region NP where they are not crimped. A reference electrode 16 is provided between the first electrolyte layer 51 and the second electrolyte layer 52 in the non-crimp region NP so as to be opposed to the positive electrode layer 2 and the negative electrode layer 4.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a laminated solid battery having a reference electrode and a method for manufacturing the same.

Background Art

[0002] In recent years, the development of solid batteries has been promoted aiming at higher energy density. In order to achieve a high electrode utilization rate, it is necessary to accurately measure the potentials of the positive electrode and the negative electrode. Although it is also possible to grasp the performance of the electrodes by performing a destructive inspection of the battery after charge and discharge, the electrode potential and the internal resistance of the electrode can be measured non-destructively by using a reference electrode.

[0003] In the case of a conventional liquid battery system, as in Patent Document 1, by immersing a reference electrode in an electrolytic solution, it is possible to separately measure the potentials of the positive electrode and the negative electrode. In a solid battery system, as in Patent Document 2, a solid electrolyte part is separately provided on the side of the solid electrolyte layer sandwiched between the positive electrode and the negative electrode so as to be connected to the solid electrolyte layer, the positive electrode, and the negative electrode, and a reference electrode is attached to this solid electrolyte part, thereby making it possible to separately measure the potentials of the positive electrode and the negative electrode.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a sheet lamination type lithium battery, from the viewpoint of avoiding short circuits and concentrated precipitation of lithium due to current concentration at the sheet ends, in many cases, the negative electrode is designed to be slightly larger than the positive electrode. However, in the cell structure of the solid battery disclosed in Patent Document 2, since the solid electrolyte part is attached to the positive electrode and the negative electrode of the same size, this structure cannot be applied to cells with different-sized negative and positive electrodes. Further, in the cell structure disclosed in Patent Document 2, since the positive electrode and the reference electrode do not face each other, and the negative electrode and the reference electrode also do not face each other, there is a risk that potential separation and resistance separation may not be reliable.

[0006] An object of the present invention is to provide a laminated solid battery unit of a sheet lamination type in which the negative electrode and the positive electrode have different sizes, includes a reference electrode, and has a structure in which potential separation and resistance separation hardly occur between the reference electrode and the positive electrode or the negative electrode, and a solid battery.

Means for Solving the Problems

[0007] According to a first aspect of the present invention, there is provided a laminated solid battery, having a flat plate-shaped positive electrode layer, an electrolyte layer, and a negative electrode layer having a larger size than the positive electrode layer in this order, wherein the electrolyte layer has a first electrolyte layer on the positive electrode layer side and a second electrolyte layer on the negative electrode side, and has a pressure-bonded region where the first electrolyte layer and the second electrolyte layer are pressure-bonded and a non-pressure-bonded region where they are not pressure-bonded, and a reference electrode is provided between the first electrolyte layer and the second electrolyte layer in the non-pressure-bonded region so as to face the positive electrode layer and the negative electrode layer. The laminated solid battery is provided.

[0008] In the laminated solid battery, the non-pressure-bonded region may be a region protruding from the battery reaction region where the battery reaction occurs, sandwiched between the positive electrode layer and the negative electrode layer. In this case, further, a positive electrode current collector layer covering the positive electrode layer, a positive electrode terminal extending from the positive electrode current collector layer and externally connected, a negative electrode current collector layer covering the negative electrode layer, and a negative electrode terminal extending from the negative electrode current collector layer and externally connected are provided, and the protruding region may be present on the positive electrode terminal.

[0009] According to a second aspect of the present invention, there is provided a laminated solid-state battery structure including the laminated solid-state battery of the first aspect and a plurality of laminated solid-state batteries laminated on the laminated solid-state battery.

[0010] According to a third aspect of the present invention, forming a positive electrode layer containing a positive electrode active material and a negative electrode layer having a dimension larger than that of the positive electrode layer and containing a negative electrode active material, forming a first electrolyte layer on the positive electrode layer, forming a second electrolyte layer on the negative electrode layer, pressing the first electrolyte layer and the second electrolyte layer, except for a part, in a region where the first electrolyte layer and the second electrolyte layer face each other and overlap, and providing a reference electrode between the first electrolyte layer and the second electrolyte layer in the part of the overlapping region so as to face the positive electrode layer and the negative electrode layer, thereby providing a method for manufacturing a laminated solid-state battery.

[0011] In the manufacturing method, preparing a negative electrode current collector having a negative electrode terminal for external connection and a positive electrode current collector having a positive electrode terminal for external connection, forming the negative electrode layer on the negative electrode current collector, forming the positive electrode layer on the positive electrode current collector, and the positive electrode layer may be formed on at least a portion of the positive electrode terminal that overlaps with the negative electrode layer.

Advantages of the Invention

[0012] In the solid-state battery of the present invention, even in a sheet-laminated solid-state battery in which the negative electrode has a larger size than the positive electrode, the reference electrode can be used to separate the potentials of the positive electrode and the negative electrode. Since the reference electrode faces the positive electrode layer and the negative electrode layer, the potentials of the positive electrode layer and the negative electrode layer can be accurately measured independently. Therefore, it becomes possible to detect the operations of the positive electrode and the negative electrode and abnormalities in the materials constituting those electrodes, and it is possible to prevent short circuits and perform maintenance of the battery unit. Further, since the reference electrode is provided on the electrolyte that is connected on the same plane as the electrolyte in the reaction region where the battery reaction occurs, the structure is simple and the manufacturing is easy.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0014] <First Embodiment> A laminated solid-state battery according to an embodiment of the present invention will be described. Since a plurality of laminated solid-state batteries are laminated to form a solid-state battery structure or a module as described later, hereinafter, it will be referred to as a "solid-state battery unit". As shown in FIGS. 1(a) to 1(c), the solid-state battery unit 10 includes a positive electrode sheet 1, a negative electrode sheet 3, and a solid electrolyte layer 5 sandwiched therebetween. The positive electrode sheet 1 has a flat plate-shaped positive electrode layer 2 containing a positive electrode active material and a flat plate-shaped positive electrode current collector 6 provided so as to cover the surface of the positive electrode layer 2. The negative electrode sheet 3 has a flat plate-shaped negative electrode layer 4 containing a negative electrode active material layer and a flat plate-shaped negative electrode current collector 8 provided so as to cover the surface of the negative electrode layer 4.

[0015] Both the positive electrode layer 2 and the negative electrode layer 4 have a substantially rectangular shape, and the negative electrode layer 4 is wider and has a larger surface area than the positive electrode layer 2. Therefore, as shown in FIG. 1(a), when the positive electrode layer 2 and the negative electrode layer 4 are overlapped, there are a corresponding region S1 (a region overlapping in the vertical direction) where the positive electrode layer 2 and the negative electrode layer 4 face each other and a non-facing region S2 (a region not overlapping in the vertical direction) where they do not face each other. The positive electrode current collector 6 and the negative electrode current collector 8 each have a positive electrode terminal 12 and a negative electrode terminal 14 protruding from the peripheral edge for external connection. In the present embodiment, as shown in FIG. 1(a), in the non-facing region S2 where the positive electrode layer 2 and the negative electrode layer 4 do not face each other, there is a portion S3 (positive electrode terminal / negative electrode layer facing portion) where the positive electrode terminal 12 and the negative electrode layer 4 face each other.

[0016] The electrolyte layer 5 exists between the positive electrode layer 2 and the negative electrode layer 4. In the manufacturing process of the solid-state battery, it is common to apply the electrolyte layer 5 to either the positive electrode layer 2 or the negative electrode layer 4 and press them together. However, in the present application, the electrolyte layer is introduced in two layers, one on the positive electrode layer side and the other on the negative electrode layer side. That is, as shown in FIG. 1(b), an electrolyte layer 51 (hereinafter referred to as the "first electrolyte layer") is provided on the positive electrode layer 2, and an electrolyte layer 52 (hereinafter referred to as the "second electrolyte layer") is formed on the negative electrode layer 4. Since the negative electrode layer 4 is larger than the positive electrode layer 2, the second electrolyte layer 52 also has a larger lateral width and longitudinal width than the first electrolyte layer 51.

[0017] The first electrolyte layer 51 and the second electrolyte layer 52 are pressure-bonded to each other in a pressure-bonding process for pressure-bonding the positive electrode layer 2, the negative electrode layer 4, and the electrolyte layer 5. In the present embodiment, a corresponding region S1 where the positive electrode layer 2 and the negative electrode layer 4 face each other is pressure-bonded to form a pressure-bonded region P. A portion where the first electrolyte layer 51 and the second electrolyte layer 52 are pressure-bonded to each other is referred to as the "pressure-bonded electrolyte layer" or the "pressure-bonded region of the electrolyte layer". On the other hand, a region where the first electrolyte layer 51 and the second electrolyte layer 52 are not pressure-bonded to each other is referred to as the "non-pressure-bonded electrolyte layer" or the "non-pressure-bonded region of the electrolyte".

[0018] In the solid battery of the present embodiment, an attached positive electrode layer 2a and an attached first electrolyte layer 51a are formed on the positive electrode terminal 12, and they are continuous with the positive electrode layer 2 and the first electrolyte layer 51 on the positive electrode current collector layer 6. Therefore, as shown in FIG. 1(c), in the positive electrode terminal / negative electrode layer facing portion S3, there is a laminated structure of the positive electrode terminal 12: the attached positive electrode layer 2a: the attached first electrolyte layer 51a: the second electrolyte layer 52: the negative electrode layer 4: the negative electrode current collector 8. However, in the positive electrode terminal / negative electrode layer facing portion S3, the attached first electrolyte layer 51a and the attached second electrolyte layer 52a are not pressure-bonded and form a non-pressure-bonded region NP of the electrolyte. The reason for providing such a non-pressure-bonded region NP is as follows. In the solid battery unit of the present invention, a reference electrode is inserted into the electrolyte layer. Since the electrolyte layer is, for example, about 50 μm thick, the distance between the reference electrode and the positive electrode or the negative electrode is about 25 μm, which is half of that. When such a thin electrolyte layer is pressure-bonded together with the reference electrode and the positive electrode or the negative electrode, there is a possibility of a short circuit between the reference electrode and the positive electrode layer or the negative electrode layer. Therefore, the region of the electrolyte where the reference electrode is provided is set as a non-pressure-bonded region to prevent such a short circuit. Also, since the reference electrode is provided in a region different from the region where the battery reaction in the solid battery is intended, the operation of the solid battery is not affected even if that region is not pressure-bonded.

[0019] In the non-bonding region NP of the electrolyte layer, since the first electrolyte layer 51a and the second electrolyte layer 52a are not bonded, their boundary is clear and it is easy to separate the two layers. On the other hand, in the bonding region P of the electrolyte layer, it is impossible to separate the first electrolyte layer 51 and the second electrolyte layer 52 or physically recognize their boundary. Therefore, it can be said that the bonding region P of the electrolyte is a layer with a uniform layer structure, and the non-bonding region NP has a boundary or is a two-layer electrolyte layer. Furthermore, it has been observed that the layer thickness of the bonding region P is about 1 / 3 to 1 / 2 thinner than that of the non-bonding region NP. Due to these structural differences, the bonding region P and the non-bonding region NP of the electrolyte layer can be distinguished. Also, in the non-bonding region NP, the resistance becomes high and it is difficult for a sufficient battery reaction to occur between the positive electrode and the negative electrode. That is, in the solid battery unit 10, the originally planned battery reaction occurs between the positive electrode layer 2 and the negative electrode layer 4 in the bonding region P of the electrolyte layer 51 (the opposing region in Fig. 1(a)).

[0020] As shown in Fig. 1(c), a flat plate-shaped or foil-shaped reference electrode 16 is inserted between the first electrolyte layer 51a and the second electrolyte 52, and the reference electrode 16 is opposed to the attached positive electrode layer 2 and negative electrode layer 4 substantially in parallel. A terminal (reference electrode current collector) 18 is connected to the reference electrode 16 for external extraction.

[0021] By connecting the positive electrode terminal 12 and the reference electrode 16 of the solid battery having the above structure with a voltage measuring device, the potential of the positive electrode layer 2 can be measured through the positive electrode layer 2a. Also, by connecting the negative electrode current collector 16 and the reference electrode 16 with a voltage measuring device, the potential of the negative electrode layer 4 can be measured. As described above, since the positive electrode layer 2a and the reference electrode 16 are opposed, and the negative electrode layer 4 is also opposed to the reference electrode 6, the potential separation of the positive electrode layer 2 and the negative electrode layer 4 is surely performed and the respective potentials can be accurately measured. Also, even when a negative electrode layer 4 with a larger area than the positive electrode layer 2 is used, by providing the reference electrode 6 using the region where the positive electrode terminal 12 and the negative electrode layer 4 are opposed, the potentials of the positive electrode layer 2 and the negative electrode layer 4 can be accurately measured independently with a simple structure.

[0022] <Second Embodiment> In the solid-state battery unit 20 of the second embodiment, as shown in FIG. 2, the reference electrode 16 is provided in the opposing region S1 where the positive electrode layer 2 and the negative electrode layer 4 face each other, that is, in the portion protruding from the battery reaction region. The positive electrode current collector 6 has a shape with a protruding portion 6p where a part of the periphery of a rectangle protrudes, and an attached positive electrode layer and an attached first electrolyte layer are formed on the protruding portion 6p. The protruding portion 6p overlaps with the negative electrode layer 4 and extends to the outer edge of the negative electrode layer 4. In the specific example shown in FIG. 2, the protruding portion 6p faces the negative electrode layer 4 and the second electrolyte layer thereon and extends to the outer edge of the negative electrode layer 4, but it is not limited thereto, and it does not have to reach the peripheral edge of the negative electrode layer 4, or it may protrude so as to extend beyond the negative electrode layer 4.

[0023] The positive electrode layer and the first electrolyte layer on the protruding portion 6p are continuous with the positive electrode layer 2 and the first electrolyte layer 51 existing in the opposing region S1, respectively. The first electrolyte layer and the second electrolyte layer in the protruding portion 6p are not crimped and constitute a non-crimped region. And a flat reference electrode 16 is inserted between the attached first electrolyte layer 51a and the second electrolyte layer 52, and the reference electrode 16 faces the positive electrode layer 2a and the negative electrode layer 4 in the protruding region 6p in parallel.

[0024] Also in the solid-state battery unit with this structure, similar to the first embodiment, by connecting the protruding portion 6p of the positive electrode current collector and the reference electrode 16 with a voltage measuring device, the potential of the positive electrode layer 2 can be measured, and by connecting the negative electrode current collector 8 and the reference electrode 16 with a voltage measuring device, the potential of the negative electrode layer 4 can be measured. Note that, similar to the first embodiment, the battery reaction in the solid-state battery unit occurs between the positive electrode layer 2 and the negative electrode layer 4 in the crimped region P of the electrolyte layer, that is, in the opposing region S1.

[0025] <Third Embodiment> In the first and second embodiments, the reference electrode is provided outside the positive electrode current collector and the positive electrode layer, that is, outside the opposing region S1. However, in this embodiment, it is provided within the opposing region S1. As shown in FIG. 3, only the first electrolyte layer and the second electrolyte layer of a part of the rectangular positive electrode current collector 6 and the positive electrode layer 2 are crimped to form a crimped region P, and the first electrolyte layer 51 and the second electrolyte layer 52 in the region 2c along the width direction of the lower edge of the positive electrode layer 2 are not crimped and become an uncrimped region NP. That is, in this solid battery unit 30, the crimped region P is smaller than the opposing region S1 and exists inside the uncrimped region NP. A reference electrode 16 exists between the first electrolyte layer 51 and the second electrolyte layer 52 in the uncrimped region NP.

[0026] Also in the solid battery unit 30 of this embodiment, the potential of the positive electrode layer 2 can be measured by connecting the positive electrode current collector 6 and the reference electrode 16 in the uncrimped region NP with a voltage measuring device, and the potential of the negative electrode layer 4 can be measured by connecting the negative electrode current collector 8 and the reference electrode 16 with a voltage measuring device. Note that also in the solid battery unit 30, the battery reaction occurs between the positive electrode layer 2 and the negative electrode layer 4 in the crimped region P of the electrolyte layer 5.

[0027] The solid battery unit having the reference electrode according to the above embodiment can accurately measure the potential of the positive electrode layer 2 and the potential of the negative electrode layer 4 independently, so that it is possible to detect the operation of the positive electrode or the negative electrode and the deterioration of the materials constituting these electrodes. For example, in a positive electrode composed of NCA, there is a risk that the crystal structure changes and the battery performance deteriorates at 4.2 V or higher. However, by detecting an abnormality by measuring the potential of the reference electrode - positive electrode layer, it becomes possible to maintain the battery operation at 4.2 V or lower. Also, in the negative electrode, for example, in an active material such as graphite whose voltage drops near the Li deposition potential, by detecting an abnormality by measuring the potential of the reference electrode - negative electrode layer, the battery operation becomes possible without reaching the Li deposition potential, and it becomes possible to prevent a short circuit due to Li electrodeposition.

[0028] The materials constituting the solid battery unit of the above embodiment will be described below.

[0029] [Positive Electrode Current Collector and Negative Electrode Current Collector] The positive electrode current collector can be made of any conductive material, for example, a conductive metal material such as stainless steel like SUS, Ni, Ti, Fe, Cu, Al, or an alloy thereof, or a carbon material, etc. The shape of the positive electrode current collector is not particularly limited, and it can be, for example, in the form of a foil, a substantially flat plate, or a net. The negative electrode current collector can be made of a material and have a shape similar to those of the positive electrode current collector.

[0030] [Solid electrolyte layer] Solid electrolyte layers such as the first and second electrolyte layers contain a solid electrolyte. As the solid electrolyte, for example, a sulfide solid electrolyte, an oxide solid electrolyte, or a polymer electrolyte can be used. As the sulfide solid electrolyte, it contains at least lithium and sulfur, for example, Li2S - P2S5 systems (Li7P3S 11 , Li3PS4, Li8P2S9, etc.), Li2S - SiS2, LiI - Li2S - SiS2, LiI - Li2S - P2S5, LiI - LiBr - Li2S - P2S5, Li2S - P2S5 - GeS2 (Li 13 GeP3S 16 , Li 10 GeP2S 12 , etc.), LiI - Li2S - P2O5, LiI - Li3PO4 - P2S5, Li 7-x PS 6-x Cl x , etc. can be used.

[0031] The oxide solid electrolyte contains at least lithium and oxygen, and when classified by crystal structure, it can be classified into NASICON type, perovskite type, garnet type, etc. For example, Li 1+x Al x Ti 2-x (PO4)3, Li 1+x Al x Ge 2-x (PO4)3, Li 3x La 2 / 3-x TiO3, Li7La3Zr2O 12、 Li 7-x La3Zr 1-x Nb x O 12、 Li 7-3x La3Zr2Al x O 12, Li3PO4, or Li 3+x PO 4-x N x (LiPON) or the like can be used. Among these, an oxide solid electrolyte having a garnet-type structure or a garnet-type similar structure containing at least Li, La, Zr, and O is preferable. In particular, Li7La3Zr2O 12、 (hereinafter referred to as "LLZ"), and those obtained by element substitution of LLZ with at least one of Mg and A ("A" is Ca, Sr, Ba, or a combination thereof) (hereinafter referred to as "substituted LLZ") are preferable. The powder composed of the electrolyte of LLZ or substituted LLZ is referred to as "LLZ-based powder".

[0032] When using LLZ-based powder as the solid electrolyte of the solid electrolyte layer, it is preferably further contained with a lithium ion conduction aid. The lithium ion conduction aid contains an ionic liquid having lithium ion conductivity. The ionic liquid having lithium ion conductivity is, for example, an ionic liquid in which a lithium salt is dissolved. Note that the ionic liquid consists of only a cation and an anion and is a substance that is liquid at room temperature. Examples of the above lithium salt include lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium trifluoromethanesulfonate (Li(SO3CF3)), lithium bis(trifluoromethanesulfonyl)imide (LiN(SO2CF3)2), lithium bis(fluorosulfonyl)imide (LiN(SO2F)2) (hereinafter referred to as "LiFSI"), lithium bis(pentafluoroethanesulfonyl)imide (LiN(SO2C2F5)2), and the like are used.

[0033] As the ionic liquid, those having, as the cation, ammonium-based such as butyltrimethylammonium and trimethylpropylammonium, imidazolium-based such as 1-ethyl-3-methylimidazolium and 1-butyl-3-methylimidazolium, piperidinium-based such as 1-butyl-1-methylpiperidinium and 1-methyl-1-propylpiperidinium, pyridinium-based such as 1-butyl-4-methylpyridinium and 1-ethylpyridinium, pyrrolidinium-based such as 1-butyl-1-methylpyrrolidinium and 1-methyl-1-propylpyrrolidinium, sulfonium-based such as trimethylsulfonium and triethylsulfonium, phosphonium-based, morpholinium-based, etc. are used.

[0034] Further, as the ionic liquid, those having, as the anion, halide-based such as Cl - , Br - etc., boride-based such as BF4 - etc., amine-based such as (NC)2N - , (CF3SO2)2N - , (FSO2)2N - etc., sulfate, sulfonate-based such as CH3SO4 - , CF3SO3 - etc., phosphate-based such as PF6 - etc. are used.

[0035] More specifically, as the ionic liquid, butyltrimethylammonium bis(trifluoromethanesulfonyl)imide, trimethylpropylammonium bis(trifluoromethanesulfonyl)imide, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-methyl-1-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, etc. are used. By containing a lithium ion conduction auxiliary, in the state where the LLZ-based powder is pressure-molded, it intervenes at the grain boundaries of the LLZ-based powder to improve the lithium ion conductivity at the grain boundaries.

[0036] The solid electrolyte layer may contain a binder. Examples of the binder include, for example, polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVDF-HFP), polytetrafluoroethylene, polyimide, polyamide, silicone, styrene-butadiene rubber, acrylic resin, polyethylene oxide, and the like. Examples of additives such as the above-mentioned LLZ-based powder (ionic conductive powder), ionic liquid, and binder are disclosed in, for example, Japanese Patent No. 6682708, and they can be used in the solid battery unit of the present invention.

[0037] The thicknesses of the first electrolyte layer and the second electrolyte layer are each 5 μm to 50 μm, preferably 5 μm to 15 μm, and the total thickness of the electrolyte layer is 10 μm to 100 μm, preferably 10 μm to 30 μm.

[0038] [Positive electrode layer] The positive electrode layer contains a positive electrode active material, and may further contain additives such as the solid electrolyte constituting the above-mentioned solid electrolyte layer, a lithium ion conduction aid, an electron conduction aid, and a binder. Examples of the positive electrode active material include, for example, S, TiS2, LiCoO2, LiNiO2, LiNi 1―x―y Co x Al y O2, LiNi 1―x―y Co x Mn y O2, LiMn2O4, LiFePO4, and the like. The above-mentioned ionic liquid having lithium ion conductivity may be included as the lithium ion conduction aid. Note that the solid electrolyte also functions as a lithium ion conduction aid. As the electron conduction aid, an electron conduction aid such as conductive carbon, Ni, Pt, or Ag can be used. As the binder, the same ones as those that can be contained in the solid electrolyte layer can be used. The thickness of the positive electrode layer can be, for example, 20 μm to 60 μm.

[0039] [Negative electrode layer] The negative electrode layer contains a negative electrode active material, and may further contain additives such as a solid electrolyte constituting the aforementioned solid electrolyte layer, a lithium ion conduction aid, an electron conduction aid, and a binder. Examples of the negative electrode active material include Li metal, Li-Al alloy, Li4Ti5O 12 , carbon, Si, SiO, etc. As the lithium ion conduction aid, the aforementioned ionic liquid having lithium ion conductivity may be included. Note that the solid electrolyte also functions as a lithium ion conduction aid. As the electron conduction aid, an electron conduction aid such as conductive carbon, Ni, Pt, or Ag can be used. As the binder, the same binder as that which can be included in the solid electrolyte layer can be used. The thickness of the negative electrode layer can be, for example, 20 μm to 70 μm.

[0040] [Reference electrode] The reference electrode may be formed, for example, from a lithium alloy or an oxide containing lithium. The size of the reference electrode 16 is not limited, but from the viewpoint of inserting it between the electrolyte layers, a flat plate with a thickness of about 10 to 50 μm is preferable. For the terminal for external connection connected to the reference electrode, a copper tape, a copper foil, or the same material as the positive electrode current collector can be used.

[0041] [Manufacturing method of the solid battery unit] The manufacturing method of the solid battery unit will be described by taking the manufacturing method of the solid battery unit of the first embodiment as an example. First, as shown respectively on the left and right of FIG. 4(a), a rectangular positive electrode current collector and a negative electrode current collector having a width longer than that of the positive electrode current collector are prepared. Next, a mixture in which a positive electrode mixture containing a positive electrode active material and a solid electrolyte is dispersed in a solvent is prepared, and this mixture is applied to the entire surface of the positive electrode current collector by wet coating or the like as shown on the left side of FIG. 4(b). After drying, a positive electrode sheet having a positive electrode layer formed on the positive electrode current collector is obtained. Also, a mixture in which a negative electrode mixture containing a negative electrode active material and a solid electrolyte is dispersed in a solvent is prepared, and this mixture is wet-coated on the region excluding the upper part of the surface of the negative electrode current collector as shown on the right side of the same figure. After drying, a negative electrode sheet having a negative electrode layer formed on the negative electrode current collector is obtained.

[0042] Next, as shown on the left side of FIG. 4(c), an electrolyte layer binder containing a solid electrolyte is applied onto the positive electrode layer of the positive electrode sheet to form a first electrolyte layer. The positive electrode sheet provided with the positive electrode layer and the first electrolyte layer is referred to as a "positive electrode electrolyte sheet". An electrolyte layer binder having the same components and composition as the first electrolyte layer is applied onto the negative electrode layer of the negative electrode sheet as shown on the right side of the same figure to form a second electrolyte layer. The negative electrode sheet provided with the negative electrode layer and the second electrolyte layer is referred to as a "negative electrode electrolyte sheet".

[0043] Next, as shown in FIG. 4(d), the positive electrode electrolyte sheet and the negative electrode electrolyte sheet are punched out such that the positive electrode terminal (positive electrode lead portion) and the negative electrode terminal (negative electrode lead portion) partially protrude from the sheet surface. By punching, the positive electrode terminal is composed of the positive electrode layer and the first electrolyte layer on the Al foil, and the negative electrode terminal consists of only the negative electrode current collector.

[0044] Then, as shown in FIG. 4(e), the punched positive electrode electrolyte sheet and the negative electrode electrolyte sheet are overlapped such that the first electrolyte faces and overlaps the second electrolyte. At this time, a reference electrode is inserted into the overlapping portion of the first electrolyte layer on the positive electrode terminal and the second electrolyte layer of the negative electrode sheet. After that, the overlapped positive electrode electrolyte sheet and the negative electrode electrolyte sheet are crimped. For crimping, a press machine heated to about 60°C is used. The crimping region is only the portion excluding the positive electrode terminal, that is, the rectangular portion where the first electrolyte and the second electrolyte overlap (the battery reaction portion). As long as only a partial region can be crimped, any crimping method can be used, not limited to a press machine. Also, the insertion of the reference electrode may be performed after the crimping process. In this way, a solid battery unit having the structure shown in FIGS. 1(a) to (c) can be manufactured.

[0045] To the solid battery unit manufactured as described above, a plurality of solid battery units without a reference electrode are stacked as shown in Fig. 5, and the positive electrode terminals and the negative electrode terminals are connected in parallel, thereby completing the solid battery structure 100 (or solid battery module). The solid battery structure can be sealed, for example, by being placed in a casing such as a laminate film made of a thermoplastic resin and heat-pressing. The welded positive electrode terminal and negative electrode terminal can be extended outside the casing as a positive electrode tab and a negative electrode tab, respectively.

[0046] When stacking the solid battery units, as shown in Fig. 5, the negative electrode current collectors and the positive electrode current collectors may be stacked so as to overlap each other, or the positive electrode current collector of the solid battery unit on which the negative electrode current collector of the solid battery unit is stacked via a separator may be stacked so as to face each other. Also, in the example shown in Fig. 5, only one solid battery unit of the solid battery structure had a reference electrode, but a plurality or all of the battery units constituting the solid battery structure may have a reference electrode. Alternatively, a solid battery unit provided with a reference electrode for each battery unit of different manufacturing lots may be introduced into the solid battery structure. The solid battery unit without a reference electrode may use a single-layer electrolyte layer instead of dividing the electrolyte layer into the first and second electrolyte layers and pressing them as described above, or may be a solid battery unit manufactured by another known method.

[0047] The manufacturing method of the solid battery unit has been described by taking the manufacturing method of the solid battery of the first embodiment as an example, but the solid batteries of the second embodiment and the third embodiment can be manufactured in the same manner by changing the insertion position and the pressing position of the reference electrode. The solid battery structure composed of a plurality of solid battery units may be provided with a battery control circuit, a voltage measurement unit, and other detectors and elements.

Example

[0048] Hereinafter, the solid battery unit and its manufacturing method will be specifically described by way of examples, but the present invention is not limited to those examples.

[0049] Lithium nickel cobalt aluminum oxide (NCA) was used as the positive electrode active material, vapor-grown carbon fiber (VGCF) was used as the electron conduction assistant, LLZ was used as the solid electrolyte, LiFSI was used as the lithium ion conduction assistant, and PVDF-HFP was used as the binder. These materials were dispersed in an organic solvent to prepare a positive electrode mixture. This positive electrode mixture was wet-coated on an Al foil with a size of 78 mm × 46 mm × 15 μm (thickness) as the positive electrode current collector to a thickness of about 30 μm to prepare a positive electrode sheet having a positive electrode layer (see FIGS. 4(a) and (b)).

[0050] Natural graphite was used as the negative electrode active material, vapor-grown carbon fiber (VGCF) was used as the electron conduction assistant, LLZ was used as the solid electrolyte, LiFSI was used as the lithium conduction assistant, and PVDF-HFP was used as the binder. These materials were mixed and dispersed in an organic solvent to prepare a negative electrode mixture. This negative electrode mixture was wet-coated on a Cu foil with a size of 80 mm × 50 mm × 12 μm (thickness) as the negative electrode current collector to a thickness of about 40 μm to prepare a negative electrode sheet having a negative electrode layer (see FIGS. 4(a) and (b)).

[0051] LLZ was used as the solid electrolyte, LiFSI (P13FSI) was used as the lithium conduction assistant, and PVDF-HFP was used as the binder. These materials were formulated to prepare a paste-like electrolyte layer mixture. The electrolyte layer mixture was wet-coated on the positive electrode layer of the positive electrode sheet and the negative electrode layer of the negative electrode sheet to a thickness of about 25 μm each to prepare a positive electrode electrolyte sheet and a negative electrode electrolyte sheet (see FIG. 4(c)).

[0052] The positive electrolyte sheet and the negative electrolyte sheet were each punched out in the upper rectangular portion (positive electrode sheet: 32 mm × 36 mm, negative electrode sheet: 30 mm × 40 mm) so that the positive electrode terminal and the negative electrode terminal protruded (see Fig. 4(d)). Next, the positive electrolyte sheet and the negative electrolyte sheet were overlapped so that the electrolytes faced each other, and a reference electrode of Li metal with a size of 5 mm × 15 mm × (thickness) 50 μm was inserted at the boundary of the overlapping portion of the electrolyte on the positive electrode terminal and the electrolyte of the negative electrolyte sheet (see Fig. 4(e)). In this state, the positive electrolyte sheet and the negative electrolyte sheet were crimped. The crimping was performed using a roll press while heating the crimping portion to about 60°C, and only the portion excluding the positive electrode terminal and the negative electrode terminal (battery reaction portion) was crimped.

[0053] For the solid battery unit thus obtained, the following measurements were carried out. Charging was performed up to 20 mAh at a current density of 0.08 mA / cm 2 between the positive electrode and the negative electrode, and then discharging was performed up to 2.5 V. At this time, a voltage measuring device was connected between the positive electrode and the reference electrode and between the negative electrode and the reference electrode, respectively, to measure the voltage. Also, the voltage was measured in the same manner between the positive electrode and the negative electrode. The charging curve and the discharging curve of the measurement results are shown in Figs. 6 and 7, respectively. From these figures, it can be seen that the potentials of the positive electrode and the negative electrode can be measured respectively, and the potentials of the positive electrode and the negative electrode are sufficiently ionically separated and can be measured. In addition, from the comparison with the voltage measurement curve using the half cell composed of Li and the positive electrode, it is known that the potential of the reference electrode is a constant 0 V (vs Li / Li + ).

[0054] The solid-state battery and its manufacturing method of the present invention have been described above using embodiments and examples. However, the technical scope of the present invention is not limited to the above range. It is obvious to those skilled in the art that various changes or improvements can be made to the above embodiments and examples, and it is also clear from the description of the claims that forms with such changes or improvements can be included in the technical scope of the present invention. For example, in the manufacturing process of the solid-state battery unit with reference to FIG. 4, the negative electrode layer and the second electrolyte layer were not formed on the negative electrode terminal, but the negative electrode layer and the second electrolyte layer may also be provided on the negative electrode terminal. Also, although the positive electrode layer and the first electrolyte layer were formed in all regions of the positive electrode current collector before punching, the positive electrode layer and the first electrolyte layer may be formed only in a part of the region for partitioning the positive electrode terminal, and it is sufficient if a reference electrode is inserted between that part and the second electrolyte layer.

[0055] In the manufacturing method shown in the specification and drawings, the execution order of each process is not specifically specified, and unless the output of the previous process is used in the subsequent process, it can be executed in any order. For the sake of convenience, even if it is described using "first," "next," etc., it does not mean that it is essential to be implemented in this order.

Explanation of Reference Signs

[0056] 10, 20, 30 Solid-state battery units 2 Positive electrode layer, 3 Negative electrode sheet, 4 Negative electrode layer 5 Electrolyte layer, 6 Positive electrode current collector, 8 Negative electrode current collector, 12 Positive electrode terminal 14 Negative electrode terminal, 16 Reference electrode, 18 Reference electrode terminal 51 First electrolyte layer, 52 Second electrolyte layer 100 Solid-state battery structure P Crimping region, NP Non-crimping region S1 Opposing region, S2 Non-opposing region, S3 Positive electrode / Positive electrode terminal / Negative electrode layer opposing portion

Claims

1. A laminated solid-state battery, comprising a flat positive electrode layer, an electrolyte layer, and a negative electrode layer having dimensions larger than those of the positive electrode layer, in this order, wherein the electrolyte layer has a first electrolyte layer on the positive electrode layer side and a second electrolyte layer on the negative electrode side, and has a crimped region where the first electrolyte layer and the second electrolyte layer are crimped and an uncrimped region where they are not crimped, a reference electrode is provided between the first electrolyte layer and the second electrolyte layer in the uncrimped region so as to face the positive electrode layer and the negative electrode layer, and the reference electrode is not crimped to either the first electrolyte layer or the second electrolyte layer.

2. The laminated solid-state battery according to claim 1, wherein the uncrimped region is a region protruding from a battery reaction region where a battery reaction occurs, sandwiched between the positive electrode layer and the negative electrode layer.

3. Furthermore, it includes a positive electrode current collector layer covering the positive electrode layer, a positive electrode terminal extending from the positive electrode current collector layer and externally connected, a negative electrode current collector layer covering the negative electrode layer, and a negative electrode terminal extending from the negative electrode current collector layer and externally connected, and the protruding region is present on the positive electrode terminal. The laminated solid-state battery according to claim 2.

4. A laminated solid-state battery structure including the laminated solid-state battery according to claim 1 and a plurality of laminated solid-state batteries laminated on the laminated solid-state battery.

5. forming a positive electrode layer containing a positive electrode active material and a negative electrode layer having dimensions larger than those of the positive electrode layer and containing a negative electrode active material, forming a first electrolyte layer on the positive electrode layer, forming a second electrolyte layer on the negative electrode layer, crimping the first electrolyte layer and the second electrolyte layer, except for a part, in a region where the first electrolyte layer and the second electrolyte layer face each other and overlap, including providing a reference electrode between the first electrolyte layer and the second electrolyte layer in the part of the overlapping region so as to face the positive electrode layer and the negative electrode layer, and in the part, the first electrolyte layer and the second electrolyte layer are not crimped in a state sandwiching the reference electrode. A method for manufacturing a laminated solid-state battery.

6. preparing a negative electrode current collector having a negative electrode terminal for external connection and a positive electrode current collector having a positive electrode terminal for external connection, forming the negative electrode layer on the negative electrode current collector, forming the positive electrode layer on the positive electrode current collector, The manufacturing method according to claim 5, comprising forming the positive electrode layer on at least a portion of the positive electrode terminal that overlaps with the negative electrode layer.

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