All-solid-state batteries and containers for all-solid-state batteries

Abstract

To provide an all-solid-state battery and a case for an all-solid-state battery, capable of accurately measuring characteristics of a battery material.SOLUTION: An all-solid-state battery of the present application includes a working electrode, a counter electrode, and a solid electrolyte layer disposed between the working electrode and the counter electrode. The solid electrolyte layer includes an extension part protruding outward from the working electrode and the counter electrode and surrounds around peripheries of the working electrode and the counter electrode, in plan view. A reference electrode is disposed on a main surface of the extension part of the solid electrolyte layer, the reference electrode surrounding at an equal distance from the peripheries of the working electrode or the counter electrode, in plan view. A case for an all-solid-state battery of the present application can accommodate and tightly seal the all-solid-state battery of the present application and includes a first cell frame, a second cell frame, and a third cell frame in this order. The first cell frame is connected to a first external terminal part, the second cell frame is connected to a second external terminal part, and the third cell frame is connected to a third external terminal part.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present application relates to an all-solid-state battery and a container for an all-solid-state battery capable of accurately measuring the characteristics of battery materials of the all-solid-state battery.

Background Art

[0002] As an electrochemical property measurement cell that can be used for measuring the properties of battery materials such as a positive electrode material, a negative electrode material, a separator, and an electrolyte of a lithium-ion secondary battery, for example, a cell configuration described in Patent Document 1 in which a battery element formed by laminating a positive electrode, a separator, and a negative electrode in this order is sealed in a state of being immersed in an electrolyte has been proposed.

[0003] On the other hand, regarding an all-solid-state battery, as a battery configuration capable of accurately measuring the potential of a positive electrode and / or a negative electrode, a configuration of an all-solid-state battery described in Patent Document 2 in which a positive electrode, a solid electrolyte layer, and a negative electrode are laminated, and a third electrode (reference electrode) is provided in a solid electrolyte portion provided so as to be connected to the solid electrolyte layer has been proposed.

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 measuring the properties of battery materials in all-solid-state batteries, unlike measurements in batteries that use an electrolyte, such as lithium-ion secondary batteries, the arrangement of the reference electrode is important, as described in Patent Document 2. However, in the battery configuration described in Patent Document 2, the Li that serves as the reference electrode is only present in a portion of the area surrounding the working electrode and the counter electrode. Therefore, if, for example, there is a difference in the depth of charge (SOC) between the working electrode and the counter electrode, it becomes impossible to accurately measure the properties of the material.

[0006] This invention solves the above-mentioned problems and provides an all-solid-state battery capable of accurately measuring the characteristics of the battery material of the all-solid-state battery, and an all-solid-state battery container capable of housing the all-solid-state battery and measuring its characteristics. [Means for solving the problem]

[0007] The all-solid-state battery of the present invention includes a working electrode, a counter electrode, and a solid electrolyte layer disposed between the working electrode and the counter electrode, wherein the solid electrolyte layer has an extended portion that, in a plan view, protrudes outward from the working electrode and the counter electrode and circles around the periphery of the working electrode and the counter electrode, and a reference electrode is disposed on the main surface of the extended portion of the solid electrolyte layer, circling at an equidistant distance from the periphery of the working electrode or the counter electrode in a plan view.

[0008] The container for a solid-state battery of the present invention is capable of housing and sealing the solid-state battery of the present invention, and includes a first cell frame, a second cell frame, and a third cell frame in that order, wherein the first cell frame has a recess formed on the upper surface of its central portion, the second cell frame has a through-hole formed in its central portion, the first cell frame and the second cell frame constitute a battery housing for housing the solid-state battery, the third cell frame covers the opening of the battery housing and is capable of sealing the battery housing, the first cell frame is connected to a first external terminal portion, the second cell frame is connected to a second external terminal portion, and the third cell frame is connected to a third external terminal portion. [Effects of the Invention]

[0009] According to this invention, the characteristics of the battery material of an all-solid-state battery can be accurately measured. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic plan view showing an all-solid-state battery according to an embodiment. [Figure 2] Figure 2 is a schematic cross-sectional view of line II in Figure 1. [Figure 3] Figure 3 is an external view of the container for an all-solid-state battery according to the embodiment. [Figure 4] Figure 4 is a schematic cross-sectional view taken along the line II-II shown in Figure 3. [Figure 5] Figure 5 shows the charge and discharge curves of the all-solid-state battery in the example. [Figure 6] Figures 6A and 6B show the virtual charge and discharge curves of the all-solid-state battery in the embodiment. [Modes for carrying out the invention]

[0011] (All-solid-state battery) An embodiment of the all-solid-state battery of the present invention will now be described. The all-solid-state battery of this embodiment comprises a working electrode, a counter electrode, and a solid electrolyte layer disposed between the working electrode and the counter electrode, wherein the solid electrolyte layer has an extended portion that, in a plan view, protrudes outward from the working electrode and the counter electrode and circles around the periphery of the working electrode and the counter electrode, and a reference electrode is disposed on the main surface of the extended portion of the solid electrolyte layer, circling at an equidistant distance from the periphery of the working electrode or the counter electrode in a plan view.

[0012] In this embodiment of the all-solid-state battery, the solid electrolyte layer has an extended portion that, in a plan view, protrudes outward from the working electrode and the counter electrode and circles around the periphery of the working electrode and the counter electrode. A reference electrode is placed on the main surface of the extended portion of the solid electrolyte layer, and in a plan view, it circles at an equidistant distance from the periphery of the working electrode or the counter electrode. As a result, the working electrode and the counter electrode are not short-circuited by the reference electrode, and the potential between the working electrode and the reference electrode, and the potential between the counter electrode and the reference electrode can be accurately measured, thus allowing for accurate determination of the electrochemical properties of the all-solid-state battery.

[0013] Furthermore, when storage tests and charge-discharge cycle tests are performed on actual all-solid-state batteries, a gradual difference in the state of charge (SOC) between the positive and negative electrodes may occur. For example, if the SOC of the positive electrode deviates from the initially designed SOC state after some test, and SOC adjustment becomes necessary, the SOC of the positive electrode can be adjusted by, for example, using a reference electrode made of Li metal as a temporary negative electrode, and performing charging (extraction of Li) or discharging (supply of Li) to the positive electrode using a charge-discharge device between the temporary negative electrode and the positive electrode whose SOC needs adjustment. In this case, the original negative electrode is not affected in any way as no current or voltage is applied to it. Thus, in this all-solid-state battery, the SOC of the electrodes can be adjusted, and in particular, in this all-solid-state battery, the reference electrode is orbited around the electrode (working electrode or counter electrode) at an equidistant distance from its periphery, so the electrode whose SOC needs adjustment can be uniformly corrected, and as a result, the battery life can be extended.

[0014] Furthermore, since the electrochemical properties of the all-solid-state battery of this embodiment can be accurately determined, it becomes possible to diagnose abnormalities in the battery during actual use, control charging and discharging, and predict the battery's lifespan, thereby improving overall battery safety, maintaining battery characteristics, and extending the battery's lifespan.

[0015] The all-solid-state battery of this embodiment will now be described based on the drawings. Figure 1 is a schematic plan view of the all-solid-state battery of this embodiment, and Figure 2 is a schematic cross-sectional view taken along line II in Figure 1. In Figures 1 and 2, the all-solid-state battery 10 of this embodiment comprises a circular working electrode 11, a circular counter electrode 12, and a circular solid electrolyte layer 13 disposed between the working electrode 11 and the counter electrode 12. The solid electrolyte layer 13 has an annular extension portion 13a that extends outward from the working electrode 11 and the counter electrode 12 in a plan view, and an annular reference electrode 14 is disposed on the main surface of the extension portion 13a, such that the distance from the periphery to the inner edge of the working electrode 11 is equidistant in a plan view. The working electrode 11 and the counter electrode 12 each have circular current collector plates 15 and 16, and the reference electrode 14 has an annular current collector plate 17.

[0016] In the all-solid-state battery 10 of the present embodiment, the reference electrode 14 is formed on the main surface (the upper surface in FIG. 2) of the extending portion 13a on the working electrode 11 side, but it may be formed on the main surface (the lower surface in FIG. 2) of the extending portion 13a on the counter electrode 12 side. That is, the reference electrode 14 may be formed on at least one of the main surfaces of the extending portion 13a, or may be formed on both surfaces of the extending portion 13a. Further, if the reference electrode 14 is formed on at least one of the main surfaces of the extending portion 13a, it may be further formed on the side surface 13b of the extending portion 13a. However, if the reference electrode 14 is formed only on the side surface 13b of the extending portion 13a, the amount of lithium supplied from the reference electrode to the electrode decreases, making it difficult to adjust the SOC of the electrode by using the reference electrode.

[0017] In the all-solid-state battery 10 of the present embodiment, as described above, the working electrode 11, the counter electrode 12, the solid electrolyte layer 13, and the current collectors 15 and 16 are each formed in a circular shape, but are not limited to a circular shape and may be formed in a rectangular shape, an elliptical shape, or the like. Further, the extending portion 13a is formed in an annular shape as described above, but may be formed in a frame shape. Furthermore, the reference electrode 14 is formed in an annular shape as described above, but is not limited to an annular shape as long as it can go around the periphery of the electrode so that the distances from the periphery of the working electrode 11 or the counter electrode 12 to the inner edge of the reference electrode 14 are all equal in a plan view. Furthermore, the current collector 17 is formed in an annular shape, but is not limited to an annular shape.

[0018] In the all-solid-state battery 10 of the present embodiment, the battery element composed of the working electrode 11, the counter electrode 12, the solid electrolyte layer 13, and the reference electrode 14 is housed in a battery container (not shown), and the battery element is used under pressure from the direction of the arrow in FIG. 2.

[0019] Next, each component of the all-solid-state battery of the present embodiment will be described. Of the working electrode and the counter electrode of the all-solid-state battery of the present embodiment, one functions as a positive electrode and the other functions as a negative electrode. Hereinafter, the case where the working electrode is the positive electrode and the counter electrode is the negative electrode will be described.

[0020] <Working Electrode (Positive Electrode)> The positive electrode constituting the working electrode 11 can be formed from a molded body of a positive electrode mixture containing a positive electrode active material. The type of positive electrode active material used in the positive electrode is not particularly limited as long as it functions as a positive electrode component of the power generation element. For example, materials used in the positive electrodes of lithium-ion secondary batteries, such as lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt manganese composite oxide, and olivine-type composite oxide, can be used, and these may be mixed as appropriate. For example, a positive electrode molded body (pellet) formed by molding a positive electrode mixture containing LCO (LiCoO2, lithium cobalt oxide), a sulfide-based solid electrolyte, and acetylene black as a conductive additive into a cylindrical shape can be used as the positive electrode.

[0021] <Opposite pole (negative pole)> The negative electrode constituting the counter electrode 12 can be formed from a molded body of a negative electrode mixture containing a negative electrode active material. The type of negative electrode active material used in the negative electrode is not particularly limited as long as it functions as a negative electrode component of the power generation element. For example, materials used in the negative electrodes of lithium-ion secondary batteries can be used, such as lithium titanate; metallic lithium, lithium alloys; carbon materials such as graphite and low-crystallinity carbon; oxides such as SiO, and these may be mixed as appropriate. For example, LTO(Li4Ti5O 12 A negative electrode can be used as a negative electrode if it is formed into a cylindrical shape from a negative electrode mixture containing lithium titanate, a sulfide-based solid electrolyte, and acetylene black, which is a conductive additive.

[0022] <Solid electrolyte layer> The solid electrolyte layer 13 can be used as a molded body (pellet) formed by shaping the solid electrolyte into a cylindrical form. The type of solid electrolyte used in the solid electrolyte layer 13 is not particularly limited; for example, hydride-based solid electrolytes, sulfide-based solid electrolytes, oxide-based solid electrolytes, etc., can be used. However, from the viewpoint of ionic conductivity, sulfide-based solid electrolytes, particularly argyrodite-type sulfide-based solid electrolytes, are preferred. When using a sulfide-based solid electrolyte, it is preferable to coat the surface of the positive electrode active material with a lithium-ion conductive material such as niobium oxide to prevent reaction with the positive electrode active material. Furthermore, the solid electrolytes contained in the positive electrode and negative electrode, as mentioned above, are not particularly limited and may also be hydride-based solid electrolytes or oxide-based solid electrolytes.

[0023] <Extension> The extended portion 13a can be provided as an extension of the solid electrolyte layer 13, and in that case, the width of the extended portion 13a is not particularly limited, but for example, it may be 1 to 5 mm.

[0024] <Reference pole> The reference electrode 14 can be made of Li or a Li alloy. Since the potential of the reference electrode 14 is constant, the potential of the positive electrode and the potential of the negative electrode can be accurately measured by measuring the voltage between the positive electrode and the reference electrode, and the voltage between the negative electrode and the reference electrode, thereby accurately determining the electrochemical properties of the all-solid-state battery.

[0025] <Current collector plate> The current collector plates 15, 16, and 17 can be formed from metal plates such as Ni, Al, Cu, Ni-Cr alloy, or Ni-Sn alloy.

[0026] <Battery container> Examples of battery containers used in the all-solid-state battery of this embodiment include coin-shaped containers, cylindrical containers, and rectangular containers.

[0027] (Container for all-solid-state batteries) An embodiment of the container for a solid-state battery of the present invention will now be described. The container for a solid-state battery of this embodiment can house and seal the solid-state battery of the present invention, and comprises a first cell frame, a second cell frame, and a third cell frame in that order. The first cell frame has a recess formed on the upper surface of its central portion, and the second cell frame has a through-hole formed in its central portion. The first cell frame and the second cell frame constitute a battery housing for housing the solid-state battery, and the third cell frame covers the opening of the battery housing, thereby sealing the battery housing. Furthermore, the first cell frame is connected to a first external terminal, the second cell frame is connected to a second external terminal, and the third cell frame is connected to a third external terminal.

[0028] The container for the all-solid-state battery of this embodiment can house and seal the all-solid-state battery of the present invention as described above. Therefore, the working electrode and counter electrode of the all-solid-state battery are not short-circuited by the reference electrode, and the potential between the working electrode and the reference electrode, and the potential between the counter electrode and the reference electrode can be accurately measured. This allows for accurate understanding of the electrochemical characteristics of the all-solid-state battery, making it easy to obtain basic data for improving battery performance.

[0029] Furthermore, as described above, the container for the all-solid-state battery of this embodiment facilitates the adjustment of the SOC of the electrodes of the all-solid-state battery and enables accurate measurement of the characteristics of the battery material.

[0030] Furthermore, since the electrochemical properties of the all-solid-state battery container of this embodiment can be accurately determined, it becomes possible to diagnose abnormalities in the battery during actual use, control charging and discharging, and predict the battery's lifespan, thereby improving overall battery safety, maintaining battery characteristics, and extending the battery's lifespan.

[0031] The container for the all-solid-state battery of this embodiment will be described below with reference to the drawings. Figure 3 is an external view of the container for the all-solid-state battery of this embodiment, and Figure 4 is a schematic cross-sectional view taken from the direction of the arrow line II-II in Figure 3. Figure 4 shows the state in which the all-solid-state battery 10 (excluding the current collector plates 15 and 16 shown in Figure 2) is housed in the all-solid-state battery container 20, but it shows the state before the all-solid-state battery container is sealed.

[0032] In Figures 3 and 4, the solid-state battery container 20 of this embodiment comprises a first cell frame 21, a second cell frame 22 positioned on the first cell frame 21, and a third cell frame 23 positioned on the second cell frame 22.

[0033] The first cell frame 21 has the shape of a disc of a predetermined thickness, and a recessed portion 21a of a predetermined depth is formed in the center of its flat upper surface. The recessed portion 21a is circular in plan view, its inner wall is perpendicular to the upper surface of the first cell frame 21, and its bottom surface is horizontal. Furthermore, an annular groove 21b is formed on the upper surface of the first cell frame 21 so as to surround the recessed portion 21a, and an O-ring 21c made of, for example, fluororesin is fitted into the annular groove 21b. In addition, screw holes 21d that penetrate in the thickness direction are formed in the vicinity of the outer circumference of the first cell frame 21 at intervals in the circumferential direction, for example, three locations. The first cell frame 21 needs to be conductive, and its material is preferably stainless steel from the viewpoint of maintaining mechanical strength, stain resistance, and rust resistance, but is not limited to this. The first cell frame 21 is also connected to the first external terminal portion 24 (described later).

[0034] The second cell frame 22 has the shape of a disc of a predetermined thickness, and a through-hole 22a is formed in its center. The through-hole 22a is circular in plan view, and its inner wall is perpendicular to the upper and lower surfaces of the second cell frame 22. Furthermore, an annular groove 22b is formed on the upper surface of the second cell frame 22 so as to surround the through-hole 22a, and an O-ring 22c made of, for example, fluororesin is fitted into the annular groove 22b. In addition, through-holes 22d that penetrate in the thickness direction are formed in the vicinity of the outer circumference of the second cell frame 22, at intervals in the circumferential direction, for example, three locations. The second cell frame 22 needs to be conductive, and its material is preferably stainless steel from the viewpoint of maintaining mechanical strength, stain resistance, and rust resistance, but is not limited to this. Also, a current-collecting bolt (second external terminal part) 25 is attached to the second cell frame 22, protruding from its side surface.

[0035] The outer diameters of the first cell frame 21 and the second cell frame 22 are approximately the same, and an annular insulating sheet 26 made of fluororesin, for example, is placed between the first cell frame 21 and the second cell frame 22. Furthermore, the recessed portion 21a of the first cell frame 21 and the through-hole 22a of the second cell frame 22 are formed and positioned so that their respective outer circumferences coincide in a plan view. The recessed portion 21a and the through-hole 22a form a battery housing portion 27 for housing the all-solid-state battery 10. In this embodiment, the battery housing portion 27 is formed in a cylindrical shape, but it can also be formed in a shape other than cylindrical by changing the shape of the recessed portion 21a and the through-hole 22a according to the outer shape of the all-solid-state battery 10 to be housed. The depth of the battery housing portion 27 can also be set to an appropriate value according to the thickness of the all-solid-state battery 10 to be housed and the thickness of the spacer (described later) used with the all-solid-state battery 10. Furthermore, the screw holes 21d of the first cell frame 21 and the through holes 22d of the second cell frame 22 are formed and positioned at corresponding locations in the upper and lower parts of the frame.

[0036] The third cell frame 23 is formed from a disc-shaped member having an outer diameter approximately the same as that of the first cell frame 21 and the second cell frame 22, and having a predetermined thickness. The third cell frame 23 also has through holes 23d that penetrate in the thickness direction, corresponding to the screw holes 21d and through holes 22d provided in the first cell frame 21 and the second cell frame 22. The third cell frame 23 needs to be conductive, and its material is preferably stainless steel from the viewpoint of maintaining mechanical strength, stain resistance, and rust resistance, but is not limited to this. In addition, a current-collecting bolt (third external terminal portion) 28 is attached to the third cell frame 23, protruding from the upper surface near its outer circumference.

[0037] Between the second cell frame 22 and the third cell frame 23, for example, an annular insulating sheet 29 made of fluororesin is placed. This allows the third cell frame 23 to cover the opening of the battery compartment 27, thereby sealing the battery compartment 27, as will be described later.

[0038] The first cell frame 21, the second cell frame 22, and the third cell frame 23 are assembled by screwing a bolt 31, which has a screw shaft portion 31a protruding upwards, into the screw hole 21d of the first cell frame 21 from below via a washer 30, and passing the through holes 22d and 23d through the bolt 31, the second cell frame 22, and the third cell frame 23 in this order. A nut 33 is then screwed onto the screw shaft portion 31a protruding from the upper surface of the third cell frame 23 via a washer 32 and tightened to assemble them. In addition, insulating bushings 22e and 23e are fitted into the through holes 22d and 23d to insulate the bolt 31 from the second cell frame 22 and the third cell frame 23.

[0039] Furthermore, the first cell frame 21 and the bolt 31 are electrically connected, and the screw shaft portion 31a protruding from the upper surface of the third cell frame 23 functions as the first external terminal portion 24.

[0040] Next, a method for measuring the electrochemical properties of an all-solid-state battery using the container for all-solid-state batteries of this embodiment will be described.

[0041] First, as shown in Figure 4, a bolt 31 is passed through the threaded hole 21d of the first cell frame 21, and an O-ring 21c is placed in the annular groove 21b of the first cell frame 21. An annular insulating sheet 26 is also placed on the outer circumference of the first cell frame 21. Then, a bolt 31 is passed through the through hole 22d of the second cell frame 22, and with the first cell frame 21 and the second cell frame 22 stacked on top of each other, an annular spacer 18, for example, made of fluororesin, is placed in the recessed portion 21a of the first cell frame 21. The annular spacer 18 is positioned so that its outer surface is in contact with the inner surface of the recessed portion 21a. Next, a circular counter electrode 12 is placed inside the annular spacer 18. The thicknesses of the annular spacer 18 and the counter electrode 12 are set to be approximately the same.

[0042] Next, an annular spacer 19, for example, made of fluororesin, is placed on top of the annular spacer 18. The width of the annular portion of the annular spacer 19 is set to be smaller than the width of the annular portion of the annular spacer 18. Subsequently, a circular solid electrolyte layer 13 is placed inside the annular spacer 19. The thickness of the annular spacer 19 and the solid electrolyte layer 13 are set to be approximately the same.

[0043] Next, an annular lithium metal reference electrode 14 is placed on the annular extension 13a of the solid electrolyte layer 13 that extends outward beyond the counter electrode 12. Subsequently, an annular nickel current collector plate 17, for example, with nickel tabs 17a at its ends, is placed on the reference electrode 14. The current collector plate 17 is positioned so as to completely cover the reference electrode (lithium metal) 14 and to be in contact with the second cell frame 22. Next, an annular spacer 34, for example, made of fluororesin, is placed on the current collector plate 17, and the tabs 17a are pressed against the inner circumferential surface of the second cell frame 22 to connect them.

[0044] Next, a circular working electrode 11 is placed on the solid electrolyte layer 13 through the inside of the annular spacer 34. Subsequently, a circular pressure plate 35, for example made of stainless steel, is placed on the working electrode 11 and the annular spacer 34, with a size that completely covers the working electrode 11 and covers a portion of the annular spacer 34. Next, a pressure spring 36 is placed on the pressure plate 35.

[0045] Next, an O-ring 22c is placed in the annular groove 22b of the second cell frame 22, and an annular insulating sheet 29 is placed on the outer circumference of the second cell frame 22. Then, the third cell frame 23 is placed on top of it by passing a bolt 31 through it. Finally, by tightening the nut 32, the first cell frame 21, the second cell frame 22, and the third cell frame 23 are assembled, and the action of the pressing plate 35 and the pressure spring 36 presses the housed solid-state battery 10 into a compressed state, thereby sealing the solid-state battery container 20. However, the mechanism for sealing the solid-state battery container 20 is not limited to the bolt and nut tightening mechanism of this embodiment.

[0046] In this state, the first cell frame 21 is connected to the counter electrode 12 of the solid-state battery 10, and the first external terminal section 24 functions as the counter electrode external terminal section; the second cell frame 22 is connected to the reference electrode 14 of the solid-state battery 10, and the second external terminal section 25 functions as the reference electrode external terminal section; and the third cell frame 23 is connected to the working electrode 11 of the solid-state battery 10, and the third external terminal section 28 functions as the working electrode external terminal section.

[0047] The container 20 for the all-solid-state battery, prepared as described above, can be connected to a charge / discharge test device (not shown) to accurately measure the electrochemical properties of the all-solid-state battery 10. [Examples]

[0048] The all-solid-state battery and container for the all-solid-state battery of the present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[0049] <Fabrication of all-solid-state batteries> A sulfide-based solid electrolyte (Li6PS5Cl) containing LiCoO2 and acetylene black in a 5% by mass ratio was mixed in a 1:1 volume ratio to produce 0.15 g of positive electrode mixture. This mixture was then compressed and molded to produce a positive electrode (working electrode) with a diameter of 9 mm and a thickness of 0.85 mm.

[0050] Also, Li4Ti5O 12 A sulfide-based solid electrolyte (Li6PS5Cl) containing 5% by mass of acetylene black was mixed with 0.10 g of a negative electrode mixture in a 1:1 volume ratio. This mixture was then compressed and molded to produce a negative electrode (counter electrode) with a diameter of 9 mm and a thickness of 0.85 mm.

[0051] For the solid electrolyte layer, 0.30 g of sulfide-based solid electrolyte (Li6PS5Cl) was compressed and molded to a diameter of 16 mm and a thickness of 1.05 mm.

[0052] A ring-shaped lithium metal electrode with an inner diameter of 11 mm, a width of 4.5 mm, and a thickness of 0.15 mm was used as the reference electrode.

[0053] Stainless steel plates were used for the current collector plates of the working electrode and counter electrode, while nickel plates were used for the current collector plate of the reference electrode.

[0054] Using the aforementioned working electrode, counter electrode, solid electrolyte layer, and reference electrode, an all-solid-state battery container, as shown in Figure 4, was assembled, housing the all-solid-state battery shown in Figure 2.

[0055] Next, the all-solid-state battery was charged and discharged at a current of 1.5 mA under a temperature of 105°C, and the potentials of the working electrode and counter electrode relative to the reference electrode were measured. The results are shown in Figure 5.

[0056] Figure 5 shows that the potentials of these electrodes during charging and discharging are similar to those reported for lithium-ion secondary batteries using organic electrolytes, indicating that the potentials of each electrode were measured correctly.

[0057] <Detection of the difference in SOC between the positive and negative electrodes> When storage tests and charge-discharge cycle tests are performed on actual all-solid-state batteries, a gradual difference in state of charge (SOC) may occur between the positive and negative electrodes. In such cases, as mentioned above, the SOC can be adjusted by performing charge and discharge between the positive electrode and the reference electrode, or between the negative electrode and the reference electrode. Whether or not a difference in the SOC between the positive and negative electrodes has occurred can be detected by observing the behavior of the charge-discharge curve (voltage of each electrode) of the all-solid-state battery, as shown below.

[0058] For example, Figures 6A and 6B show the virtual charge-discharge curves of the LTO (lithium titanate) / LCO (lithium cobalt oxide) trielectrode cell (reference electrode is Li metal) fabricated in the previous example. First, from the charge-discharge curve in Figure 6A, it can be seen that the voltage of the LCO (positive electrode) changes abruptly at the end of discharge, and in this case, the sharp drop in cell voltage is due to the sharp change in the voltage of the LCO (positive electrode). This is thought to be because the state of charge (SOC) of the positive electrode was lower than that of the negative electrode.

[0059] On the other hand, the charge-discharge curve in Figure 6B shows that the voltage of the LTO (negative electrode) changes abruptly at the end of discharge. In this case, the sharp drop in cell voltage is due to the abrupt change in the voltage of the LTO (negative electrode). This is thought to be because the state of charge (SOC) of the negative electrode was lower than that of the positive electrode.

[0060] In the example above, we used two types of cells to explain the difference in state of charge (SOC) of the electrodes. However, even with a single cell, by conducting storage tests and charge-discharge cycle tests and comparing the charge-discharge curves before and after the tests, it is possible to detect whether or not there is a difference in the depth of charge (SOC) between the positive and negative electrodes.

[0061] Although embodiments of the all-solid-state battery and container for the all-solid-state battery of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications are possible as long as they do not depart from the spirit of the invention. [Explanation of symbols]

[0062] 10 Solid-state battery, 11 Working electrode, 12 Counter electrode, 13 Solid electrolyte layer, 14 Reference electrode, 15, 16, 17 Current collector plate, 18, 19 Annular spacer, 20 Solid-state battery container, 21 First cell frame, 22 Second cell frame, 23 Third cell frame, 24 First external terminal section, 25 Second external terminal section, 26, 29 Insulating sheet, 27 Battery housing section, 28 Third external terminal section, 30, 32 Washer, 31 Bolt, 33 Nut, 34 Annular spacer, 35 Pressure plate, 36 Pressure spring

Claims

1. An all-solid-state battery comprising a working electrode, a counter electrode, and a solid electrolyte layer disposed between the working electrode and the counter electrode, The solid electrolyte layer, in a plan view, has an extended portion that protrudes outward from the working electrode and the counter electrode and encircles the periphery of the working electrode and the counter electrode. An all-solid-state battery characterized in that a reference electrode is arranged on the main surface of the extended portion of the solid electrolyte layer, and in a plan view, the reference electrode is positioned at an equidistant distance from the periphery of the working electrode or the counter electrode.

2. The all-solid-state battery according to claim 1, wherein the working electrode, the counter electrode, and the solid electrolyte layer are formed in a circular shape, and the extended portion and the reference electrode are formed in an annular shape.

3. The all-solid-state battery according to claim 1, wherein the working electrode and the counter electrode each further comprises a current collector plate.

4. The all-solid-state battery according to claim 3, wherein the current collector plate is formed in a circular shape.

5. The all-solid-state battery according to claim 1, wherein the reference electrode further comprises a current collector plate.

6. The all-solid-state battery according to claim 5, wherein the current collector plate is formed in an annular shape.

7. The all-solid-state battery according to claim 1, wherein the reference electrode is formed of Li or a Li alloy.

8. The all-solid-state battery according to claim 1, wherein the battery elements, which consist of the working electrode, the counter electrode, the solid electrolyte layer, and the reference electrode, are housed in a battery container and the battery elements are pressurized.

9. A container for an all-solid-state battery that can house and seal the all-solid-state battery described in claim 1, The first cell frame, the second cell frame, and the third cell frame are included in this order. The first cell frame has a recessed portion formed on the upper surface of the central part. The aforementioned second cell frame has a through-hole formed in the center, The first cell frame and the second cell frame constitute a battery housing section for housing the all-solid-state battery. The third cell frame can cover the opening of the battery compartment and seal the battery compartment. The first cell frame is connected to the first external terminal section, The second cell frame is connected to the second external terminal section, A container for an all-solid-state battery, characterized in that the third cell frame is connected to a third external terminal.

10. The container for a solid-state battery according to claim 9, wherein the first cell frame and the third cell frame are configured to press against the solid-state battery.

11. The container for an all-solid-state battery according to claim 9, wherein an annular groove is formed on the upper surface of the first cell frame surrounding the recessed portion, and an O-ring is fitted into the annular groove.

12. The first cell frame is connected to the counter electrode of the all-solid-state battery, and the first external terminal portion functions as the counter electrode external terminal portion. The second cell frame is connected to the reference electrode of the all-solid-state battery, and the second external terminal portion functions as the reference electrode external terminal portion. The container for a solid-state battery according to claim 9, wherein the third cell frame is connected to the working electrode of the solid-state battery, and the third external terminal portion functions as the external terminal portion of the working electrode.

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