BATTERY, BATTERY EXTERIOR, AND MEASUREMENT METHOD

A battery includes: a power generating element including a first electrode layer, a second electrode layer, and a first solid electrolyte layer located between the first electrode layer and the second electrode layer; and a reference electrode section including a second solid electrolyte layer having a first main surface in contact with a side surface of the power generating element and a second main surface opposite to the first main surface, and a reference electrode in contact with the second main surface of the second solid electrolyte layer, in which a length of the first main surface is longer than a length of the side surface in a laminating direction in the power generating element.

BACKGROUND

1. Technical Field

The present disclosure relates to a battery, a battery exterior, and a measurement method.

2. Description of the Related Art

A solid-state battery that uses a flame-retardant solid electrolyte instead of a liquid electrolyte containing a flammable organic solvent for use in a battery in the related art such as a non-aqueous electrolyte type lithium-ion secondary battery holds high superiority in basic performance for safety. Thus, having high potential in terms of cost and energy density, such as simplification of a safety device in product development, the solid-state battery is seen as a promising next-generation battery and development competition thereof is accelerating.

However, in order to put solid-state batteries into practical use and further improve their performance, further development is required for active materials capable of achieving high capacity and high output, high-conductivity solid electrolytes, optimum design, process construction, and the like. To this end, it is very important to accurately grasp the battery characteristics in development of various materials, design using combinations of them, and manufacturing process study. In particular, being able to measure electrical characteristics such as a potential of a positive electrode and/or a negative electrode is extremely useful in advancing the research and development effectively and efficiently. Furthermore, if electrical characteristics such as a potential of each of electrodes including the positive electrode, the negative electrode, and the like during operation can be measured during actual use of a battery, it is possible to perform appropriate battery control based on the measured values, and also possible to improve the performance, for example, such as safety and cycling performance.

As a method for investigating the potential and electrochemical behavior of each single electrode, known is a three-electrode measurement method using a reference electrode. For example, “Q&A de Rikaisuru Denkikagaku no Sokulei Houhou(Understanding of Electrochemical Measurement Method with Q & A)” edited by The Electrochemical Society of Japan, published by Mimizuku-sha on December 2009, p. 10 (hereinafter referred to as Non Patent Literature 1) describes battery configurations of solid-state batteries having various structures in which the three-electrode measurement is possible. In addition, Japanese Unexamined Patent Application Publication No. 2013-20915 (hereinafter referred to as Patent Literature 1) discloses a solid-state battery in which a positive electrode current collector, a positive electrode, a solid electrolyte layer, a negative electrode, and a negative electrode current collector are laminated and a third electrode is provided as a reference electrode in contact with a solid electrolyte portion provided being connected with the same width as the length of the side surface of the solid electrolyte layer or the length of the side surfaces of the positive electrode, the solid electrolyte layer, and the negative electrode.

SUMMARY

However, regarding the battery configurations in the related art for performing three-electrode measurement in solid-state batteries, the structures of the batteries are complicated and the formation of the reference electrode requires precise work. For these reasons, it is difficult to form a solid-state battery for performing three-electrode measurement.

One non-limiting and exemplary embodiment provides a battery and the like in which an electrical characteristic of each electrode can be easily measured.

In one general aspect, the techniques disclosed here feature a battery according to one aspect of the present disclosure includes: a power generating element including a first electrode layer, a second electrode layer, and a first solid electrolyte layer located between the first electrode layer and the second electrode layer; and a reference electrode section including a second solid electrolyte layer having a first main surface in contact with a side surface of the power generating element and a second main surface opposite to the first main surface, and a reference electrode in contact with the second main surface of the second solid electrolyte layer, in which a length of the first main surface is longer than a length of the side surface in a laminating direction in the power generating element.

According to the present disclosure, an electrical characteristic of each electrode can be measured easily.

DETAILED DESCRIPTIONS

Outline of Present Disclosure

The outline of one aspect of the present disclosure is as follows.

A battery according to one aspect of the present disclosure includes: a power generating element including a first electrode layer, a second electrode layer, and a first solid electrolyte layer located between the first electrode layer and the second electrode layer; and a reference electrode section including a second solid electrolyte layer having a first main surface in contact with a side surface of the power generating element and a second main surface opposite to the first main surface, and a reference electrode in contact with the second main surface of the second solid electrolyte layer, in which a length of the first main surface is longer than a length of the side surface in a laminating direction in the power generating element.

In this structure, the reference electrode section can be produced with such dimensional accuracy that the length of the first main surface just has to be greater than the length of the side surface so as to easily bring the side surface into contact with the first main surface in production of the reference electrode section. Hence, it is possible to easily produce a battery which includes a reference electrode and in which an electrical characteristic such as a potential of each electrode of the battery can be measured. Therefore, according to the present aspect, an electrical characteristic of each electrode can be measured easily.

Moreover, for example, the first solid electrolyte layer and the second solid electrolyte layer may have lithium-ion conductivity.

This makes it possible to easily measure an electrical characteristic of each electrode in a lithium-ion battery.

In addition, for example, the reference electrode may contain at least one of metallic lithium, a lithium alloy, or a lithium compound.

Since this structure has a small equilibrium potential variation, the measurement accuracy of an electrical characteristic of each electrode can be improved.

Moreover, for example, the battery may include a plurality of power generating elements laminated, each of which being the power generating element included in the battery.

With this structure, even in a multilayer type battery, an electrical characteristic of each electrode can be easily measured.

In addition, for example, the first main surface may be in contact with the plurality of power generating elements.

With this structure, an electrical characteristic of each electrode in each of the plurality of power generating elements can be measured. Further, since the first main surface is in contact with the plurality of power generating elements, the area where the reference electrode section is in contact with the power generating elements can be increased, so that the mechanical strength of the battery can be improved.

In addition, for example, the battery may further include an exterior covering the power generating element and the reference electrode section.

In this structure, the power generating element and the reference electrode section are protected and held by the exterior and deterioration, damage, and the like of the battery are suppressed, so that an electrical characteristic of each electrode can be measured stably.

Moreover, for example, the exterior may have a first cavity extending in a first direction and a second cavity extending in a second direction crossing the first direction and communicating with the first cavity, the power generating element may be in contact with an inner surface of the exterior forming the first cavity, and the reference electrode section may be in contact with an inner surface of the exterior forming the second cavity.

With this structure, the power generating element and the reference electrode section are held by the exterior even when expanding and contracting during charging and discharging. Further, since the power generating element and the reference electrode section are easily kept pressurized by the exterior, the measurement accuracy of an electrical characteristic of each electrode in the battery can be improved.

Then, for example, at least one of the first cavity or the second cavity may have a cylindrical shape.

This structure allows easy formation of the first cavity and the second cavity. In addition, this structure is capable of uniformly dispersing a pressure applied for forming the power generating element and the reference electrode section in the first cavity and the second cavity and a stress due to expansion and contraction of the power generating element and the reference electrode section during charging and discharging, therefore making the exterior less likely to be damaged even under a higher pressure or stress, and enabling stable measurement of an electrical characteristic of each electrode.

Moreover, for example, a portion of the exterior in contact with the power generating element and the reference electrode section may contain a resin material.

Thus, since the resin material has good workability, it is possible to easily form an exterior in a shape suited to the shapes of the power generating element and the reference electrode section.

In addition, for example, the exterior may have a first exterior section in contact with the power generating element and the reference electrode section and a second exterior section located outside the first exterior section, and a strength of the second exterior section may be higher than a strength of the first exterior section.

Even when a high pressure is applied to the power generating element, this structure suppresses deformation and damage of the first exterior section and therefore enables the power generating element to be formed appropriately. In addition, the power generating element can be kept pressurized even at a higher pressure. This makes it possible to stably measure an electrical characteristic of each electrode in the battery.

Meanwhile, for example, the second exterior section may contain a metal material.

Thus, the second exterior section having a higher strength can be easily formed.

A current line may further be provided between the reference electrode and at least one of the first electrode layer or the second electrode layer.

With this structure, the positive or negative electrode is electrically connected to the reference electrode, which enables charging and discharging.

There, lithium ions are intercalated and deintercalated between the positive or negative electrode and the reference electrode, so that characteristics of the battery can be improved. For example, it is possible to perform an operation such as controlling the charge-discharge capacity, changing the rate-determining conditions of the positive and negative electrodes, changing the irreversible capacity, or improving the cycling performance.

In addition, since this operation can be performed dynamically even after the battery is built or while the battery is being used as a power source, it is possible to perform more appropriate control for improving the characteristics according to conditions of the built battery or the operating battery.

Then, a battery exterior according to one aspect of the present disclosure is the exterior described above.

The battery exterior described above allows formation of the power generating element and the reference electrode section therein, and is capable of protecting and holding the power generating element and the reference electrode section formed.

A measurement method according to one aspect of the present disclosure is a method for measuring an electrical characteristic of a battery including a power generating element including a first electrode layer, a second electrode layer, and a first solid electrolyte layer located between the first electrode layer and the second electrode layer, the method including: preparing a reference electrode section including a second solid electrolyte layer having a first main surface in contact with a side surface of the power generating element and a second main surface opposite to the first main surface, and a reference electrode in contact with the second main surface of the second solid electrolyte layer; bringing the first main surface of the second solid electrolyte layer into contact with the side surface of the power generating element; and measuring an electrical characteristic between the reference electrode and at least one of the first electrode layer or the second electrode layer, in which a length of the first main surface is longer than a length of the side surface in a laminating direction in the power generating element.

In this method, the reference electrode section can be easily prepared because the reference electrode section can be produced with such dimensional accuracy that the length of the first main surface just has to be greater than the length of the side surface so as to easily bring the side surface into contact with the first main surface in production of the reference electrode section. This easily makes it possible to stably measure an electrical characteristic of each electrode in the battery.

Hereinafter, embodiments will be described specifically in reference to the accompanying drawings.

Each of the embodiments described below presents a comprehensive or specific example. The numeric values, shapes, materials, constituent elements, a layout and a connection form of the constituent elements, manufacturing processes, the order of the manufacturing processes, and so on described in the following embodiments are just examples and are not intended to limit the present disclosure. Among the constituent elements in the following embodiments, the constituent elements not specified in independent claims are described as optional constituent elements.

The drawings are schematic ones and are not necessarily illustrated exactly.

Therefore, for example, the scales and the like are not always consistent among the drawings. Moreover, in the drawings, substantially the same constituent elements are assigned with the same reference sign and the repetitive description will be omitted or simplified.

In the present description, terms indicating relationships between elements such as parallel and orthogonal, terms indicating the shapes of elements such as a rectangular shape and a circular shape, and numerical ranges are not expressions specifying strict meanings only, but are expressions meaning substantially the equivalent ranges, for example, including a difference by about several percent.

In the present description and drawings, an x axis, a y axis, and a z axis represent three axes in a three-dimensional Cartesian coordinate system. In the embodiments, a z-axis direction is used as a laminating direction that is a direction perpendicular to a main surface of a power generating element. A positive z-axis direction is regarded as an upper side in the z-axis direction, whereas a negative z-axis direction is regarded as a lower side in the z-axis direction. In the present description, “plan view” means a view of a battery seen along the z axis. In the present description, “thickness” means a length in a direction perpendicular to the main surface of each layer.

In the present description, the meanings of “inner” and “outer” in “an inner side” and “an outer side” are such that “inner” means a direction closer to the center of the battery and “outer” means a direction farther from the center of the battery, unless otherwise stated.

In the present description, the terms “upper” and “lower” in the structure of the battery do not refer to an absolutely upper direction (vertically upper side) and an absolutely lower direction (vertically lower side) in a spatial recognition, but are used as terms specified according to a relative positional relationship based on the order of layers in a multi-layer structure. In addition, the terms “upper” and “lower” are also applied to not only a case where two constituent elements are arranged close to each other and in contact with each other, but also a case where two constituent elements are spaced apart from each other and another constituent element is present between the two constituent elements.

First, a battery according to Embodiment 1 will be described.

Structure of Battery

First, a structure of a battery according to the present embodiment will be described.FIG.1is a sectional view illustrating a schematic configuration of a battery500according to the present embodiment.

As illustrated inFIG.1, the battery500includes a solid-state battery section100having a power generating element50and a reference electrode section150. The battery500is, for example, an all-solid-state battery. The shape of the battery500is, for example, a coin type, a laminate type, a cylindrical type, a square type, or the like.

The solid-state battery section100includes the power generating element50, a positive electrode current collector60, and a negative electrode current collector70. In the solid-state battery section100, the positive electrode current collector60is laminated on a surface of a positive electrode layer10opposite to a first solid electrolyte layer30and the negative electrode current collector70is laminated on a surface of a negative electrode layer20opposite to the first solid electrolyte layer30. In other words, the solid-state battery section100has a structure in which the negative electrode current collector70, the negative electrode layer20, the first solid electrolyte layer30, the positive electrode layer10, and the positive electrode current collector60are laminated in this order. The solid-state battery section100has, for example, a cuboid shape, a polygonal columnar shape, a cylindrical shape, or the like.

The power generating element50has the positive electrode layer10, the negative electrode layer20, and the first solid electrolyte layer30located between the positive electrode layer10and the negative electrode layer20. The positive electrode layer10is an example of the first electrode layer and the negative electrode layer20is an example of the second electrode layer. In the power generating element50, the negative electrode layer20, the first solid electrolyte layer30, and the positive electrode layer10are laminated in this order.

The reference electrode section150includes a second solid electrolyte layer130having a first main surface130ain contact with a side surface50aof the power generating element50and a second main surface130bopposite to the first main surface130a, and a reference electrode110in contact with the second main surface130b.

Hereinafter, detailed description will be given of the constituent elements included in the battery500.

The power generating element50is located between the positive electrode current collector60and the negative electrode current collector70. The side surface50aof the power generating element50is in contact with the reference electrode section150, more specifically the first main surface130aof the second solid electrolyte layer130. The side surface50ais a surface connecting end portions of the two main surfaces of the power generating element50and is a flat surface parallel with a laminating direction in the power generating element50inFIG.1. The side surface50amay incline with respect to the laminating direction in the power generating element50. The laminating direction in the power generating element50is a direction in which the layers constituting the power generating element50are laminated, or more specifically the negative electrode layer20, the first solid electrolyte layer30, and the positive electrode layer10are laminated one on top of another.

The power generating element50has, for example, a cuboid shape, a polygonal columnar shape, a cylindrical shape, or the like.

The positive electrode layer10is located between the positive electrode current collector60and the first solid electrolyte layer30, and is in contact with the positive electrode current collector60and the first solid electrolyte layer30. Moreover, a side surface of the positive electrode layer10on the reference electrode section150side is in contact with the second solid electrolyte layer130, more specifically the first main surface130a.

The positive electrode layer10contains at least a positive electrode active material. As a material for the positive electrode layer10in addition to the positive electrode active material, a positive electrode mixture containing at least one of a solid electrolyte, a conductive aid, or a binder material may be used, if necessary.

As the positive electrode active material, any known material capable of intercalating and deintercalating (inserting and extracting or dissolving and precipitating) metal ions such as lithium ions, sodium ions, magnesium ions, potassium ions, calcium ions, or copper ions may be used.

Examples of the positive electrode active material include transition metal oxides containing lithium, transition metal oxides containing no lithium, transition metal fluorides, polyanionic materials, fluorinated polyanionic materials, transition metal sulfides, transition metal oxyfluorides, transition metal oxysulfides, transition metal oxynitrides, and the like. When a lithium-containing transition metal oxide is used as the positive electrode active material, it is possible to reduce the battery manufacturing cost and also increase the average discharge voltage of the battery.

Examples of a material capable of extracting and inserting lithium ions usable as the positive electrode active material include lithium cobalt composite oxide (LCO), lithium nickel composite oxide (LNO), lithium manganese composite oxide (LMO), lithium-manganese-nickel composite oxide (LMNO), lithium-manganese-cobalt composite oxide (LMCO), lithium-nickel-cobalt composite oxide (LNCO), lithium-nickel-manganese-cobalt composite oxide (LNMCO), and the like. Specific examples of the positive electrode active material include LiCoO2, LiMn2O4, Li2NiMn3O8, LiVO2, LiCrO2, LiFePO4, LiCoPO4, LiNiO2, LiNi1/3Co1/3Mn1/3O2, LiNixMnyAlzO2, LiNixCoyMnz, LiNixCoyAlz, and the like.

As the solid electrolyte, a known material that conducts protons or metal ions such as lithium ions, sodium ions, magnesium ions, potassium ions, calcium ion, copper ions, or silver ions may be used. An example usable as the solid electrolyte is a solid electrolyte material such as a sulfide solid electrolyte, a halogen-based solid electrolyte, an oxide solid electrolyte, or a polymer solid electrolyte.

An example of the sulfide solid electrolyte usable as a material capable of conducting lithium ions is a composite (Li2S—P2S5) composed of lithium sulfide (Li2S) and diphosphorus pentasulfide (P2S5). As the sulfide solid electrolyte, there are sulfides such as Li2S—P2S5, Li2S—P2SS—LiBH4, Li7P3S11, Li2S—SiS2, Li2S—SiS2—Li3PO4, Li2S—SiS2—Li4SiO4, Li2S—B2S3, Li2S—GeS2, Li6PS5Cl, LiSiPSCl, and a sulfide containing Li3N or Li3N(H). As the sulfide solid electrolyte, any of the above sulfides to which at least one of Li3N, LiCl, LiBr, LiI, Li3PO4, or Li4SiO4is added as an additive may be used. Moreover, other specific sulfide solid electrolytes are Li10GeP2SI2(LGPS), Na3Zr2(SiO4)2PO4(NASICON), and the like.

An example of the oxide solid electrolyte usable as a material capable of conducting lithium ions is Li7La3Zr2O12(LLZ), Li1.3Al0.3Ti1.7(PO4)3(LATP), (La,Li)TiO3(LLTO), or the like.

The halogen-based solid electrolyte is a solid electrolyte containing a halide. The halide is a compound composed of, for example, Li, M′, and X′, M′ is at least one element selected from the group consisting of metal elements other than Li and metalloid elements. X′ is at least one element selected from the group consisting of F, Cl, Br, and I. The “metal elements” are all the elements contained in groups 1 to 12 of the periodic table (but excluding hydrogen), and all the elements contained in groups 13 to 16 of the periodic table (but excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se). The “metalloid elements” are B, Si, Ge, As, Sb, and Te. For example, M′ may include Y (yttrium). Halides containing Y are Li3YCl6and Li3YBr6.

The polymer solid electrolyte is not particularly limited and may be any solid electrolyte containing a polymer material having ion-conductivity. Examples of the polymer material having ion-conductivity include polyethers, polyether-derivatives, polyesters, polyimines, and the like.

As the solid electrolyte, a solid electrolyte material in a thin film form such as lithium phosphorus oxynitride (LIPON) may be used, other than the above solid electrolyte materials.

In the positive electrode layer10, a volume ratio of the positive electrode active material to the total volume of the positive electrode active material and the solid electrolyte is, for example, greater than or equal to 30% and less than or equal to 95%. Then, a volume ratio of the solid electrolyte to the total volume of the positive electrode active material and the solid electrolyte is, for example, greater than or equal to 5% and less than or equal to 70%. When the amount of the positive electrode active material and the amount of the solid electrolyte are in the above volume ratios, a sufficient energy density of the battery500can be easily ensured and the battery500can be easily operated with high output.

Examples of the conductive aid include graphite such as natural graphite and artificial graphite, carbon black such as acetylene black, furnace black, and Ketjen black (registered trademark), conductive fibers such as VGCF, carbon nanotubes, carbon nanofibers, fullerene, carbon fiber, and metal fiber, metal powders such as carbon fluoride and aluminum powders, conductive whiskers such as zinc oxide whiskers and potassium titanate whiskers, conductive metal oxides such as titanium oxide, conductive polymer compounds such as polyaniline, polypyrrole, and polythiophene, and the like.

The conductive aid is in, for example, a needle form, a scaly form, a spherical form, or an elliptical spherical form. The conductive aid may be particles.

The thickness of the positive electrode layer10is, for example, greater than or equal to 10 μm and less than or equal to 500 μm. When the thickness of the positive electrode layer10is within the above range, a sufficient energy density of the battery500can be easily ensured, and the battery500can be easily operated with high output.

An example of a method for forming the positive electrode layer10is a method of uniaxial pressing of a powdered positive electrode mixture or the like. Instead, a paste-like paint in which a positive electrode mixture and a solvent are kneaded may be applied onto a substrate, the first solid electrolyte layer30, the positive electrode current collector60, or the like, and then dried to produce the positive electrode layer10.

The negative electrode layer20is located between the negative electrode current collector70and the first solid electrolyte layer30and is in contact with the negative electrode current collector70and the first solid electrolyte layer30. Then, a side surface of the negative electrode layer20on the reference electrode section150side is in contact with the second solid electrolyte layer130, more specifically the first main surface130a.

The negative electrode layer20contains at least a negative electrode active material. As a material for the negative electrode layer20in addition to the negative electrode active material, a negative electrode mixture containing at least one of a solid electrolyte, a conductive aid, or a binder material may be used, if necessary.

As the negative electrode active material, any known material capable of intercalating and deintercalating (inserting and extracting or dissolving and precipitating) metal ions such as lithium ions, sodium ions, magnesium ions, potassium ions, calcium ions, or copper ions may be used. As the negative electrode active material, there are metal materials, carbon materials, oxides, nitrides, tin compounds, silicon compounds, and the like.

An example of a material capable of extracting and inserting lithium ions usable as the negative electrode active material is a carbon material such as natural graphite, artificial graphite, graphite carbon fiber, or heat-treated resin carbon, metallic lithium, a lithium alloy, an oxide of lithium and transition metal elements, or the like. Metals usable for the lithium alloy include indium, aluminum, silicon, germanium, tin, zinc, and the like. Specific ones as the oxide of lithium and transition metal elements are Li4TiiO2, LixSiO, and the like.

For the solid electrolyte of the negative electrode layer20, the foregoing solid electrolyte materials may be used. In addition, for the conductive aid of the negative electrode layer20, the foregoing conductive aids may be used. Moreover, as the binder material of the negative electrode layer20, the foregoing binder materials may be used.

In the negative electrode layer20, a volume ratio of the negative electrode active material to the total volume of the negative electrode active material and the solid electrolyte is, for example, greater than or equal to 30% and less than or equal to 95%. Then, a volume ratio of the solid electrolyte to the total volume of the negative electrode active material and the solid electrolyte is, for example, greater than or equal to 5% and less than or equal to 70%. When the amount of the negative electrode active material and the amount of the solid electrolyte are in the above volume ratios, a sufficient energy density of the battery500can be ensured, and the battery500can be easily operated with high output.

The thickness of the negative electrode layer20is, for example, greater than or equal to 10 μm and less than or equal to 500 μm. When the thickness of the negative electrode layer20is within the above range, a sufficient energy density of the battery500can be easily ensured, and the battery500can be easily operated with high output.

An example of a method for forming the negative electrode layer20is a method of uniaxial pressing of a powdered negative electrode mixture or the like. Instead, a paste-like paint in which a negative electrode mixture and a solvent are kneaded may be applied onto a substrate, the first solid electrolyte layer30, the negative electrode current collector70, or the like, and then dried to produce the negative electrode layer20.

The first solid electrolyte layer30is located between the positive electrode layer and the negative electrode layer20and is in contact with the positive electrode layer10and the negative electrode layer20. Then, a side surface of the first solid electrolyte layer on the reference electrode section150side is in contact with the second solid electrolyte layer130, more specifically the first main surface130a.

The first solid electrolyte layer30has conductivity of metal ions such as lithium ions, sodium ions, magnesium ions, potassium ions, calcium ions, or copper ions. The first solid electrolyte layer30may have lithium-ion conductivity.

The first solid electrolyte layer30contains at least a solid electrolyte, and may contain a binder material if necessary. The first solid electrolyte layer30may contain a solid electrolyte having lithium-ion conductivity.

For the solid electrolyte of the first solid electrolyte layer30, the foregoing solid electrolyte materials may be used. For the first solid electrolyte layer30, one solid electrolyte may be used or two or more solid electrolytes may be used. Moreover, as the binder material of the first solid electrolyte layer30, the foregoing binder materials may be used.

The thickness of the first solid electrolyte layer30is, for example, greater than or equal to 0.1 μm and less than or equal to 1000 μm. From the viewpoint that the energy density of the battery500can be improved, the thickness of the first solid electrolyte layer may be greater than or equal to 0.1 μm and less than or equal to 50 μm.

An example of a method for forming the first solid electrolyte layer30is a method of uniaxial pressing of a powdered material containing the first solid electrolyte layer30, or the like. Instead, a paste-like paint in which a material containing the first solid electrolyte layer30and a solvent are kneaded may be applied onto a substrate, the positive electrode layer10, the negative electrode layer20, or the like, and then dried to produce the first solid electrolyte layer30.

The side surface of the positive electrode layer10, the side surface of the negative electrode layer20, and the side surface of the first solid electrolyte layer30are flush with each other and constitute the side surface50a. However, the side surface of the positive electrode layer10, the side surface of the negative electrode layer20, and the side surface of the first solid electrolyte layer30do not have to be flush with each other. For example, the side surfaces of the positive electrode layer10and the negative electrode layer20may be covered with the first solid electrolyte layer30and the side surface of the first solid electrolyte layer30may alone constitute the side surface50a.

The positive electrode current collector60is located on top of the positive electrode layer10and is in contact with the positive electrode layer10. The negative electrode current collector70is located under the negative electrode layer20and is in contact with the negative electrode layer20. Side surfaces of the positive electrode current collector60and the negative electrode current collector70are in contact with the first main surface130a.

A material for the positive electrode current collector60and the negative electrode current collector70is a metal material having high conductivity such as, for example, copper, aluminum, nickel, iron, stainless steel, platinum, gold, an alloy of two or more of these, or a plated product of any of these. The positive electrode current collector60and the negative electrode current collector70may be formed of the same material or formed of different materials.

The shapes of the positive electrode current collector60and the negative electrode current collector70are not particularly limited and may be set depending on the shape of the battery500and the like. The positive electrode current collector60and the negative electrode current collector70have, for example, a rod shape, a plate shape, a sheet shape, a foil shape, a mesh shape, or the like.

The thickness of each of the positive electrode current collector60and the negative electrode current collector70is, for example, greater than or equal to 1 μm and less than or equal to 10 mm. Instead, the thickness of each of the positive electrode current collector60and the negative electrode current collector70may be greater than or equal to 10 mm depending on the shape of the battery500.

The second solid electrolyte layer130is located between the reference electrode110and the power generating element50. The second solid electrolyte layer130has the first main surface130aand the second main surface130b.

The first main surface130ais in contact with the side surface50aof the power generating element50. Specifically, the first main surface130ais in contact with all the side surfaces on the reference electrode section150side of the positive electrode layer10, the negative electrode layer20, and the first solid electrolyte layer30constituting the power generating element50. In other words, the first main surface130ais in contact with a region spanning from one end to the other end of the side surface50ain the laminating direction (z-axis direction). The first main surface130ais also further in contact with the positive electrode current collector60and the negative electrode current collector70. In the laminating direction in the power generating element50, a length L2of the first main surface130ais longer than a length L1of the side surface50ain contact with the first main surface130a. The length L1is a length of a portion of the side surface50ain contact with the first main surface130a. Meanwhile, the second main surface130bis in contact with the reference electrode110.

As a material for forming the second solid electrolyte layer130, the same materials as in the first solid electrolyte layer30may be used. Here, for the first solid electrolyte layer30and the second solid electrolyte layer130, the same material may be used or different materials may be used. For the second solid electrolyte layer130, one solid electrolyte may be used or two or more solid electrolytes may be used.

Then, the thickness of the second solid electrolyte layer130is, for example, greater than or equal to 10 μm and less than or equal to 10 mm.

The reference electrode110is in contact with the second main surface130bof the second solid electrolyte layer130. InFIG.1, the reference electrode110is in contact with the entire second main surface130b. Instead, the reference electrode110do not have to be in contact with the entire second main surface130b, but may be provided to be in contact with a partial region on the second main surface130b.

As a material for the reference electrode110, any material that exhibits an equilibrium potential when being in electrochemical contact with the second solid electrolyte layer130may be used without particular limitation. The reference electrode110contains at least one of, for example, metallic lithium, an lithium alloy, or a lithium compound. From the viewpoint of measurement accuracy, a material having a small equilibrium potential variation may be used as the material for the reference electrode110. Examples of the material having a small equilibrium potential variation include metallic lithium, lithium alloys such as In—Li and lithium compounds such as Li4Ti5O12.

Each of the positive electrode layer10, the negative electrode layer20, the first solid electrolyte layer30, the positive electrode current collector60, the negative electrode current collector70, the second solid electrolyte layer130, and the reference electrode110has, for example, a circular shape, a rectangular shape, a polygonal shape, or the like in plan view.

As a method for producing the battery500according to the present embodiment, the same method as a method for producing a general battery may be used except that the method includes providing the second solid electrolyte layer130and the reference electrode110. For example, first, powders of a material for forming the positive electrode layer10, a material for forming the first solid electrolyte layer30, and a material for forming the negative electrode layer20are sequentially pressed and compression molded to produce the power generating element50. Moreover, before or after the power generating element50is produced, a material for forming the second solid electrolyte layer130is pressed and compression molded to form the second solid electrolyte layer130. Thereafter, on the second solid electrolyte layer130thus formed, for example, the reference electrode110is placed or a material for forming the reference electrode110is pressed and compression molded to produce the reference electrode section150. Then, the first main surface130aof the second solid electrolyte layer130is brought into contact with the side surface50aof the power generating element50, so that the battery500can be produced. Instead, the reference electrode section150may be directly formed on the side surface50aof the power generating element50.

Method for Measuring Electrical Characteristic of Battery

Next, a method for measuring an electrical characteristic of the battery500according to the present embodiment will be described. Specifically, the method for measuring the electrical characteristic of the battery500including the power generating element50will be described by usingFIGS.2A and2B.

FIGS.2A and2Bare diagrams for describing the method for measuring the electrical characteristic of the battery500.

As illustrated inFIG.2A, first, the power generating element50and the reference electrode section150are prepared by using the aforementioned production method or the like. Then, the first main surface130aof the second solid electrolyte layer130is brought into contact with the side surface50aof the power generating element50. Thus, the battery500is formed as illustrated inFIG.2B. In the contact state, the length of the first main surface130ais longer than the length of the side surface50ain the laminating direction in the power generating element50as described above. To be more specific, in the preparation of the reference electrode section150, the reference electrode section150is prepared which includes the second solid electrolyte layer130having the first main surface130awith a length in at least one direction (the length L2in the present embodiment) longer than the length L1of the side surface50ain the laminating direction in the power generating element50.

Then, for example, as illustrated inFIG.2B, voltage meters91,92, and93are electrically connected between the positive electrode layer10and the negative electrode layer20, between the positive electrode layer10and the reference electrode110, and between the negative electrode layer20and the reference electrode110, respectively. This makes it possible to measure a voltage V1between the positive electrode layer10and the negative electrode layer20, a voltage V2between the positive electrode layer10and the reference electrode110, and a voltage V3between the negative electrode layer20and the reference electrode110. In this way, the electrical characteristic such as the voltage between the reference electrode110and at least one of the positive electrode layer10or the negative electrode layer20is measured. Instead, as the electrical characteristic, an electrical characteristic other than the voltage, such as impedance, may be measured.

In this measurement, the reference electrode110exhibits a certain value as the equilibrium potential with the second solid electrolyte layer130irrespective of operations of the positive electrode layer10and the negative electrode layer20, so that the potential of the positive electrode layer10and/or the negative electrode layer20can be measured as a potential difference between the reference electrode110and the positive electrode layer and/or the negative electrode layer20.

For the solid-state batteries having the reference electrodes in the related art, various structures have been studied as disclosed in Non Patent Literature 1, but these structures are complicated and are not easy to form.

The solid-state battery having the reference electrode disclosed in Patent Literature 1 has the structure in which the positive electrode, the solid electrolyte layer, and the negative electrode are laminated, and the third electrode is provided as the reference electrode in contact with the solid electrolyte portion provided being connected with the same width as the length of the side surface of the solid electrolyte layer or the length of the side surfaces of the positive electrode, the solid electrolyte layer, and the negative electrode, and therefore is capable of measuring the potential of the positive electrode and/or the negative electrode.

However, it is not easy to form the solid electrolyte portion matching the length of the side surface of the solid electrolyte layer or the length of the side surfaces of the positive electrode, the solid electrolyte layer, and the negative electrode as in the structure described in Patent Literature 1. In addition, a solid-state battery having thin electrodes and a thin solid electrolyte layer is more preferable because the solid-state battery can achieve better characteristics. The solid-state battery thus having the thin layers, however, has a problem that the formation of the solid electrolyte portion is even more difficult.

Meanwhile, in order to operate a solid-state battery formed, the solid-state battery has to be brought into a pressurized state in general. However, it is not easy to pressurize the complicated structures as described in Non Patent Literature 1 and Patent Literature 1 while keeping their functions and measure the characteristics of the batteries and the electrodes.

In the present embodiment, it is found that, for three-electrode measurement, the second solid electrolyte layer130in contact with the power generating element50does not have to have a structure in which the length of the first main surface130aexactly matches the side surface50ain the laminating direction in the power generating element50, but just has to be brought into electrochemical contact with the power generating element50. Thus, as illustrated inFIG.1, the battery500has the structure which includes the power generating element50and the reference electrode section150and in which the length L2of the first main surface130aof the second solid electrolyte layer130is longer than the length L1of the side surface50aof the power generating element50in the laminating direction in the power generating element50. Therefore, the reference electrode section150can be produced with such dimensional accuracy that the length L2of the first main surface130ajust has to be longer than the length L1of the side surface50aso as to easily bring the side surface50ainto contact with the first main surface130ain the production of the reference electrode section150. Hence, it is possible to easily produce the battery500in which the electrical characteristics such as the potentials of the positive electrode layer and the negative electrode layer20can be measured. As a result, the electrical characteristic of each electrode can be easily measured by using the battery500and the method for measuring the electrical characteristic of the battery500.

The potential of each of the positive electrode layer10and/or the negative electrode layer20can be measured easily by using the battery500according to the present embodiment. Thus, in the development of batteries, the electrical characteristic of the positive electrode layer10and/or the negative electrode layer20can be grasped and the electrical characteristics of the positive electrode layer10and the negative electrode layer can be measured separately, so that the development and designing of batteries can be promoted efficiently and effectively.

Then, in the case where the battery500according to the present embodiment is applied to a battery for practical use, the following effects may be achieved, for example. For example, in the positive electrode layer10, in the case where the active material at a certain potential or higher changes in its structure and thereby deteriorates the electrode performance, such as a charge-discharge capacity and cycling performance, the potential of the positive electrode layer10can be monitored and controlled so as not to reach the certain potential or higher. As a result, deterioration in the electrode performance due to charging in the battery500can be prevented. Meanwhile, in the negative electrode layer20, for example, in the case where the electrode during charging is used up to around a metallic lithium precipitation potential, the potential of the electrode is monitored and controlled so as not to reach the metallic lithium precipitation potential (for example, greater than or equal to 0 V, vs. Li+/Li), so that the metallic lithium precipitation can be prevented. As a result, it is possible to reduce the risks in the battery500such as shortening of the battery life along with a decrease in the charge-discharge capacity and cycling deterioration, as well as a short-circuit phenomenon, heating, and ignition associated with the precipitation of metallic lithium.

Next, a battery according to Embodiment 2 will be described.

Embodiment 2 is different from Embodiment 1 mainly in that the battery according to Embodiment 2 includes multiple power generating elements laminated. In the following description, different points from Embodiment 1 will be mainly described, and the description of the common points will be omitted or simplified.

FIG.3is a sectional view illustrating a schematic configuration of a battery501according to the present embodiment. As compared with the battery500according to Embodiment 1, the battery501includes a solid-state battery section101in place of the solid-state battery section100.

As illustrated inFIG.3, the battery501according to the present embodiment includes the solid-state battery section101including multiple power generating elements50laminated and a reference electrode section150.

The solid-state battery section101includes the multiple power generating element50laminated in a parallel circuit form with current collectors (positive electrode current collectors60inFIG.3) interposed in between. In addition, the solid-state battery section101includes the positive electrode current collectors60between the multiple power generating elements50and negative electrode current collectors70located on the sides of the power generating elements50opposite to the respective positive electrode current collector60sides. In the solid-state battery section101, the multiple power generating elements50are laminated such that the positive electrode layer10of the upper power generating element50and the positive electrode layer10of the lower power generating element50out of the power generating elements50neighboring in the laminating direction are in contact with the positive electrode current collectors60between the neighboring power generating elements50. In other words, the solid-state battery section101has a structure in which the multiple power generating elements50are laminated with their upper and lower directions alternately inverted so that the homopolar electrode layers in the neighboring power generating elements50can face each other across the current collectors.

A first main surface130aof the second solid electrolyte layer130is in contact with side surfaces50aof the respective multiple power generating elements50. Since the first main surface130ais in contact with the multiple power generating elements50as described above, the area where the reference electrode section150is in contact with the power generating elements50can be increased to improve the mechanical strength of the battery501. Although the first main surface130ais in contact with all the side surfaces50aof the power generating elements50inFIG.3, the power generating element50having the side surface50aout of contact with the first main surface130amay be present.

Even in such battery501, the reference electrode section150thus provided makes it possible to measure an electrical characteristic such as an electrode potential of at least one of the multiple positive electrode layers10or negative electrode layers20laminated in the parallel circuit form and therefore easily and independently measure an electrical characteristic, such as a potential behavior of each of the positive electrode layers10and the negative electrode layers20, as in the case of the battery500.

Although the power generating elements50are laminated such that both surfaces of one positive electrode current collector60are in contact with another positive electrode current collector60and the positive electrode layer10inFIG.3, each of the power generating elements50may have a structure in which the positive electrode layer10and the negative electrode layer20are reversed. Moreover, although the solid-state battery section101includes two power generating elements50inFIG.3, the solid-state battery section101may include three or more power generating elements50laminated in a parallel circuit form. In the case where the solid-state battery section101includes three or more power generating elements50, the battery501may include multiple reference electrode sections150, and each of the first main surfaces130aof the multiple reference electrode sections150may be in contact with the side surface50aof at least one power generating element50among the three or more power generating elements50.

Next, a battery according to Embodiment 3 will be described.

Embodiment 3 is different from Embodiment 1 mainly in that the battery according to Embodiment 3 further includes an exterior. In the following description, different points from Embodiments 1 and 2 will be mainly described, and the description of the common points will be omitted or simplified.

FIG.4Ais a top view illustrating a schematic configuration of a battery502according to the present embodiment.FIG.4Bis a sectional view illustrating the schematic configuration of the battery502according to the present embodiment.FIG.4Billustrates a cross section of the battery502at a position specified by a line IVB-IVB inFIG.4A.FIG.4Cis a side view illustrating the schematic configuration of the battery502according to the present embodiment.FIG.4Cillustrates a side surface of the battery502when viewed from a reference electrode section152side of the battery502(that is, a positive x-axis direction side). As compared with the battery500according to Embodiment 1, the battery502includes the solid-state battery section102and the reference electrode section152in place of the solid-state battery section100and the reference electrode section150. In addition, as compared with the battery500according to Embodiment 1, the battery502further includes an exterior200and a reference electrode current collector160.

As illustrated inFIGS.4A,4B, and4C, the battery502includes the solid-state battery section102including a power generating element52, the reference electrode section152, the reference electrode current collector160, and the exterior200covering the power generating element52and the reference electrode section152and having a first cavity210and a second cavity220. The battery502has a cylindrical shape.

The solid-state battery section102includes the power generating element52, a positive electrode current collector62, and a negative electrode current collector72. The solid-state battery section102has a structure in which the negative electrode current collector72, a negative electrode layer22, a first solid electrolyte layer32, a positive electrode layer12, and the positive electrode current collector62are laminated in this order. The solid-state battery section102has a cylindrical shape. The solid-state battery section102may include multiple power generating elements52laminated with current collectors interposed in between.

The power generating element52includes the positive electrode layer12, the negative electrode layer22, and the first solid electrolyte layer32located between the positive electrode layer12and the negative electrode layer22. The power generating element52is located inside the first cavity210, and is in contact with an inner surface210aof the exterior200forming the first cavity210. Specifically, a portion ofa side surface52aof the power generating element52out of contact with a first main surface132ais in contact with the inner surface210a. The power generating element52has a cylindrical shape.

The reference electrode section152includes a second solid electrolyte layer132having the first main surface132ain contact with the side surface52aof the power generating element52and a second main surface132bopposite to the first main surface132a, and a reference electrode112in contact with the second main surface132b. The reference electrode section152is located inside the second cavity220, and is in contact with an inner surface220aof the exterior200forming the second cavity220. Specifically, a side surface of the reference electrode section152(in other words, the surface parallel with a laminating direction in the reference electrode section152) is in contact with the inner surface220a. The reference electrode section152has a cylindrical shape.

Since the power generating element52and the reference electrode section152are in contact with the inner surface210aand the inner surface220a, respectively, as described above, the power generating element52and the reference electrode section152are held by the exterior200even when expanding and contracting during charging and discharging. Further, since the power generating element52and the reference electrode section152are easily kept pressurized by the exterior200, the measurement accuracy of an electrical characteristic of each of the electrodes in the battery502can be improved.

The positive electrode current collector62is located inside the first cavity210. A side surface of the positive electrode current collector62is in contact with the inner surface210a. An upper surface of the positive electrode current collector62is flush with an upper surface of the exterior200. However, the upper surface of the positive electrode current collector62may be located inside the first cavity210. Instead, the positive electrode current collector62may protrude from the upper surface of the exterior200.

The negative electrode current collector72is located inside the first cavity210. A side surface of the negative electrode current collector72is in contact with the inner surface210a. A lower surface of the negative electrode current collector72is flush with a lower surface of the exterior200. However, the lower surface of the negative electrode current collector72may be located inside the first cavity210. Instead, the negative electrode current collector72may protrude from the lower surface of the exterior200.

The reference electrode current collector160is located on a side of the reference electrode112opposite to the second solid electrolyte layer132side and is in contact with the reference electrode112. Here, the position at which the reference electrode current collector160is in contact with the reference electrode112is not particularly limited, and the reference electrode current collector160may be in contact with any of the surfaces of the reference electrode112other than the surface in contact with the second solid electrolyte layer132. The reference electrode current collector160is in contact with the entire surface on the side of the reference electrode112opposite to the second solid electrolyte layer132side, but instead may be in contact with a portion of the surface on the side of the reference electrode112opposite to the second solid electrolyte layer132side.

The reference electrode current collector160is located inside the second cavity220. A surface on a side of the reference electrode current collector160opposite to the reference electrode112side is flush with an outer surface of the exterior200. However, the surface on the side of the reference electrode current collector160opposite to the reference electrode112side may be located inside the second cavity220. Instead, the reference electrode current collector160may protrude from the outer surface of the exterior200.

A material for the reference electrode current collector160is a metal material having high conductivity, such as, for example, copper, aluminum, nickel, iron, stainless steel, platinum, gold, an alloy of two or more of these, or a plated product of any of these.

The shape of the reference electrode current collector160is not particularly limited and may be set depending on the shapes of the battery502and the exterior200and the like. The reference electrode current collector160has, for example, a rod shape, a plate shape, a sheet shape, a foil shape, a mesh shape, or the like.

The thickness of the reference electrode current collector160is, for example, greater than or equal to 1 μm and less than or equal to 10 mm. Instead, the thickness of the reference electrode current collector160may be greater than or equal to 10 mm depending on the shapes of the battery502and the exterior200.

Each of the positive electrode layer12, the negative electrode layer22, the first solid electrolyte layer32, the positive electrode current collector62, the negative electrode current collector72, the second solid electrolyte layer132, the reference electrode112, and the reference electrode current collector160has a circular shape in plan view, but the shape is not limited to that shape and may be a rectangular shape, a polygonal shape, or the like.

The battery502may further include a take-out terminal electrically connected to each of the positive electrode current collector62, the negative electrode current collector72, and the reference electrode current collector160. A material for the take-out terminal may be any material having conductivity and materials generally used for batteries may be used. Examples of the material for the take-out terminal include copper, aluminum, stainless steel, and the like. The take-out terminal has a foil shape, a lead shape, or the like. Here, the positive electrode current collector62, the negative electrode current collector72, and the reference electrode current collector160may also work as the take-out terminals.

The exterior200is a battery exterior in which the power generating element52and the reference electrode section152are formed and which is for holding the power generating element52and the reference electrode section152. The shape of the exterior200is not particularly limited and may be any shape capable of covering the power generating element52and the reference electrode section152. In the example illustrated, the exterior200has a cylindrical shape having the cavities in which the power generating element52and the reference electrode section152are to be formed. The exterior200may have a cuboid shape, a polygonal columnar shape, or the like.

The exterior200has the first cavity210extending in a first direction and the second cavity220extending in a second direction crossing the first direction and communicating with the first cavity210. In the example illustrated, the first direction is the laminating direction in the power generating element52(the z-axis direction) and the second direction is the direction normal to the side surface52aof the power generating element52(the x-axis direction). In the present embodiment, the first direction and the second direction are orthogonal to each other. The first cavity210is a hole located at a center portion in the exterior200when viewed from the first direction and passing through the exterior200. The second cavity220is a hole located at a center portion in the exterior200when viewed from the second direction and extending from the outer surface of the exterior200to the first cavity210.

The side surface52aof the power generating element52located inside the first cavity210and the first main surface132aof the second solid electrolyte layer132in the reference electrode section152located inside the second cavity220are in contact with each other at an intersection of the first cavity210and the second cavity220where the first cavity210and the second cavity220communicate with each other. The first cavity210and the second cavity220have cylindrical shapes. The cylindrical shapes of the first cavity210and the second cavity220allows easy formation of the first cavity210and the second cavity220. In addition, this structure is capable of uniformly dispersing a pressure applied for forming the power generating element52and the reference electrode section152and the stress due to expansion and contraction of the power generating element52and the reference electrode section152during charging and discharging, therefore making the exterior200less likely to be damaged even under a higher pressure or stress, and enabling measurement of an electrical characteristic of each electrode under conditions in wider ranges. Note that the shapes of the first cavity210and the second cavity220are not limited to the cylindrical shapes but may be cuboid shapes or polygonal columnar shapes. The first cavity210and the second cavity220may be tapered.

The inner surface210aof the exterior200forming the first cavity210is in contact with the power generating element52, the positive electrode current collector62, and the negative electrode current collector72. In short, the inner surface210ais in contact with the solid-state battery section102. The inner surface220aof the exterior200forming the second cavity220is in contact with the reference electrode section152and the reference electrode current collector160.

The positional relationship between and the shapes of the first cavity210and the second cavity220may be any positional relationship and shapes as long as the power generating element52and the reference electrode section152can be in electrochemical contact with each other. The positional relationship between and the shapes of the first cavity210and the second cavity220may be any positional relationship and shapes determined based on ease of processing and current extraction from the positive electrode layer12, the negative electrode layer22, and the reference electrode112.

A material for the exterior200is not particularly limited and may be any material having insulating properties. Examples of the material for the exterior200include resin materials, such as epoxy resin, polycarbonate resin, polybutadiene resin, acrylic resin, polyamide resin, and polyacetal resin, ceramic, and the like. Among these, a resin material may be contained as a main component in a portion of the exterior200in contact with the power generating element52and the reference electrode section152from the viewpoints of workability, light weight, and cost.

Next, a battery according to Embodiment 4 will be described.

Embodiment 4 is different from Embodiment 3 mainly in that the exterior of the battery according to Embodiment 4 has a two-layer structure. In the following description, different points from Embodiments 1 to 3 will be mainly described, and the description of the common points will be omitted or simplified.

FIG.5Ais a top view illustrating a schematic configuration of a battery503according to the present embodiment.FIG.5Bis a sectional view illustrating the schematic configuration of the battery503according to the present embodiment.FIG.5Billustrates a cross section of the battery503at a position specified by a line VB-VB inFIG.5A. As compared with the battery502according to Embodiment 3, the battery503includes an exterior203in place of the exterior200. Since the exterior200and the exterior203have the same outer shapes, a side surface of the battery503has the same shape as in the battery502illustrated inFIG.4C.

As illustrated inFIGS.5A and5B, the battery503includes a solid-state battery section102including a power generating element52, a reference electrode section152, a reference electrode current collector160, and the exterior203covering the power generating element52and the reference electrode section152and having a first cavity213and a second cavity223.

The exterior203has a first exterior section230and a second exterior section240located outside the first exterior section230when viewed from the first direction. Each of the first exterior section230and the second exterior section240has a cylindrical shape in which a cavity is formed.

The first cavity213is a hole located at a center portion in the first exterior section230when viewed from the first direction and passing through the first exterior section230. The first cavity213is formed in the first exterior section230. An inner surface213aof the first exterior section230forming the first cavity213is in contact with the power generating element52, a positive electrode current collector62, and a negative electrode current collector72. In short, the inner surface213ais in contact with the solid-state battery section102.

The second cavity223is a hole located at a center portion in the second exterior section240(exterior203) when viewed from the second direction and extending from an outer surface of the second exterior section240through the first exterior section230to the first cavity213. In an inner surface223aof the exterior203forming the second cavity223, the inner surface of the first exterior section230is in contact with the reference electrode section152. In the inner surface223aof the exterior203forming the second cavity223, the inner surface of the second exterior section240is out of contact with the reference electrode section152. However, the inner surface of the second exterior section240may be in contact with the reference electrode section152.

The first exterior section230is in contact with the power generating element52and the reference electrode section152. Specifically, the first exterior section230is in contact with both of the side surfaces of the power generating element52and the reference electrode section152. The first exterior section230is a portion of the exterior203in contact with the power generating element52and the reference electrode section152. When viewed from the first direction, the outer surface of the first exterior section230is entirely covered with the second exterior section240and is contact with the second exterior section240. However, when viewed from the first direction, a portion of the outer surface of the first exterior section230may not be covered with the second exterior section240.

As a material for the first exterior section230, the foregoing materials for the exterior200may be used. The first exterior section230may contain a resin material as a main component.

The second exterior section240is in contact with the reference electrode current collector160. Then, the second exterior section240is out of contact with the power generating element52and the reference electrode section152. However, the second exterior section240may be out of contact with the reference electrode current collector160. For example, another member may be inserted between the reference electrode current collector160and the second exterior section240. Instead, the second exterior section240may be in contact with the reference electrode section152.

When viewed from the first direction, an inner surface of the second exterior section240is in contact with the first exterior section230. The second exterior section240is a cylinder having a cylindrical cavity for storing the first exterior section230at a center portion when viewed from the first direction. The strength of the second exterior section240is higher than the strength of the first exterior section230. Thus, even when a high pressure is applied to the power generating element52, deformation and damage of the first exterior section230are suppressed since the first exterior section230is covered with the second exterior section240having the higher strength and therefore the power generating element52can be formed appropriately. In addition, the power generating element52can be kept pressurized even at a higher pressure. This makes it possible to stably measure an electrical characteristic of each of the electrodes in the battery503. Moreover, as compared with the structure in which the exterior only includes the first exterior section230, the structure in which the exterior203includes the second exterior section240allows the exterior to be formed with the same degree of strength even if a portion covering the power generating element52is thin, and thereby enables size reduction. Here, the second exterior section240may cover the outer side of the first exterior section230when viewed from the second direction. In this case, a higher pressure can be applied to the reference electrode section152.

A material for the second exterior section240may be a material having a higher strength than that of the first exterior section230. Examples of the material for the second exterior section240include metal materials including metals, such as iron, copper, nickel, and aluminum, alloys of combinations of these, alloys each mainly containing any of them, and the like, high strength resins, such as engineering plastics and resin composite materials reinforced with carbon fibers or the like. The second exterior section240may contain a metal material as a main component from the viewpoint of strength and workability. For the second exterior section240, a stainless steel may be used from the viewpoint of corrosion resistance.

Example

Hereinafter, Example in the present disclosure will be described. This Example is only for illustrative purposes and is not intended to limit the present disclosure.

First, glass electrolyte powder of a sulfide solid electrolyte Li2S—P2S5(Li2S:P2S5=70:30 (mole ratio)) was prepared as a raw material for the solid electrolyte. The powder obtained by annealing treatment of the above glass electrolyte powder at 200° C. was used as the solid electrolyte. The power thus obtained contained triclinic crystals as a main component, had a wide crystalline distribution from crystalline to amorphous, and had an average particle size of 5 μm.

Next, LiNi0.85Co0.15Al0.05O2powder as the positive electrode active material and the solid electrolyte weighed to a volume ratio of 1:1 were mixed to obtain the positive electrode mixture.

Then, natural graphite powder as the negative electrode active material and the solid electrolyte weighed to a volume ratio of 1:1 were mixed to obtain the negative electrode mixture.

Subsequently, the exterior including the first exterior section made of an acrylic resin and the second exterior section made of a stainless steel was prepared such that the first exterior section had a cylindrical shape with a diameter of 20 mm and a height of 20 mm and had a first cavity with a diameter of 9.5 mm formed at the center thereof, the second exterior section had a cylindrical shape with a diameter of 30 mm and a height of 20 mm and had a cavity for storing the first exterior section with the diameter of 20 mm at the center thereof, and a second cavity with a diameter of 3 mm communicating with the first cavity was formed at a center portion of a side surface of the exterior. Then, 30 mg of the solid electrolyte was put in the second cavity and pressurized to form the second solid electrolyte layer, and thereafter the reference electrode section was produced by placing metallic lithium as the reference electrode in contact with the second solid electrolyte layer. Meanwhile, 80 mg of the solid electrolyte was put in the first cavity and pressurized at 100 MPa to form the first solid electrolyte layer, and thereafter 16.7 mg of the positive electrode mixture was put on one of the surface sides of the first solid electrolyte layer and pressurized at 100 MPa to obtain the positive electrode layer. Subsequently, 15.4 mg of the negative electrode mixture was put on the side of the first solid electrolyte layer opposite to the positive electrode layer side and pressurized at 600 MPa to form the negative electrode layer, so that the power generating element was produced. The power generating element was formed such that the side surface of the power generating element was in contact with the second solid electrolyte layer. In this way, the battery including the power generating element and the reference electrode section was obtained. Here, a jig for pressurization was used to pressurize each of the layers.

Next, the positive electrode current collector and the negative electrode current collector were formed by inserting stainless steel rods in a cylindrical shape with a diameter of 9.5 mm into the first cavity from the upper and lower directions. Meanwhile, the reference electrode current collector was formed by inserting a stainless steel rod with a diameter of 3 mm into the second cavity.

Next, the battery in Example was obtained which was kept pressurized at a pressure of 150 MPa by pressurization with bolts from the upper and lower directions of the stainless steel rods serving as the positive electrode current collector and the negative electrode current collector. In the following description, the positive electrode layer and the positive electrode current collector will be collectively referred to as the positive electrode, the negative electrode layer and the negative electrode current collector will be collectively referred to as the negative electrode, and the reference electrode and the reference electrode current collector will be collectively referred to as the reference electrode.

In the battery for evaluation thus obtained, voltage meters were connected between the positive electrode and the negative electrode, between the positive electrode and the reference electrode, and between the negative electrode and the reference electrode, and then a current of 120 μA was applied between the positive electrode and the negative electrode to charge the battery to 4.2 V. Thereafter, the battery was discharged to 2.5 V with the same current value.FIG.6is a diagram presenting results of voltage measurements of the battery in Example when being charged and discharged.

As illustrated inFIG.6, in the battery in Example, the battery voltage, which is a voltage between the positive electrode and the negative electrode, rose during charging and dropped during discharging, which confirms that the battery was able to be charged and discharged. In addition, the positive electrode potential (vs. Li) and the negative electrode potential (vs. Li) demonstrated the behaviors corresponding to the battery voltage during the charging and discharging, which confirms that each of the positive electrode potential and the negative electrode potential was able to be measured concurrently together with the battery voltage.

Other Embodiments

Although the battery, the exterior, and the method for measuring an electrical characteristic of a battery according to the present disclosure have been described heretofore based on the embodiments, the present disclosure should not be limited to these embodiments. The scope of the present disclosure includes various modifications of the embodiments conceivable by those skilled in the art and other modes constructed by combining some of the constituent elements in the embodiments, without departing from the gist of the present disclosure.

In the foregoing embodiments, the power generating element includes the positive electrode layer and the negative electrode layer, but is not limited to this structure. For example, in the case where the battery is used to grasp an electrical characteristic of an electrode, the power generating element may have a second positive electrode layer in place of the negative electrode layer. In this case, an electrical characteristic of each of the positive electrode layers can be measured alone. In addition, the power generating element may include a second negative electrode layer in place of the positive electrode layer.

Further, in the foregoing embodiments, various changes, replacements, additions, omissions, or the like can be made within the scope of claims or the scope of the equivalents thereof.

According to the present disclosure, it is possible to obtain a battery in which a potential of a positive electrode and/or a negative electrode can be easily measured. In addition, it is also possible to obtain an exterior that enables easy formation of a battery and is capable of holding the battery.