Flexible all-solid-state battery and method for manufacturing the same

Abstract

According to one embodiment of the present invention, provided is a flexible all-solid-state battery having a weight energy density as high as that of a lithium ion battery that uses a conventional electrolytic solution, and having high safety in which short-circuiting does not occur even when being bent by an excessive bending load. According to one embodiment of the present invention, provided is a flexible all-solid-state battery having a layer of a solid polymer electrolyte disposed between a layer of a separator that holds a solid polymer electrolyte and a layer comprising a negative electrode active material. In this flexible all-solid-state battery, the separator may comprise any one of: a woven fabric, a knitted fabric, or a nonwoven fabric formed of inorganic or polymer fibers in an amount of 1-70 g / m2 and in a thickness of 1-100 μm; an oxide ceramic particle layer that includes oxide ceramic particles at a filling rate in the range of 5-60%, each having a particle size of 1-20 μm; and a composite body of the oxide ceramic particles and the woven fabric, the knitted fabric, or the nonwoven fabric.

Description

Technical Field

[0001] The present invention relates to a new structure of a flexible all-solid-state battery and a technique for manufacturing the battery.

Background Art

[0002] Since the early 2000s, the popularity of wearable devices as computers worn on the body has been increasing. Currently, devices such as eyeglass-type devices and IoT (Internet of Things) sensors that are linked to smartphones have attracted attention. Recently, the technical development of sensor suits for inertial motion capture systems that estimate a person's posture by wearing sensors equipped with magnetism, acceleration, and gyro has been carried out. In addition, the technical development of organic devices that do not feel worn and are in harmony with humans using highly biocompatible organic materials that can be used in the healthcare field has been carried out. Thus, the uses of wearable devices are expanding day by day.

[0003] Regarding the batteries that supply power to these wearable devices, lithium-ion batteries with high energy density, small size, and light weight are used. However, for devices that require a storage capacity of several hundred mAh or more, there is a problem that the user feels inconvenient due to the body wearing of lithium-ion batteries that are hard and cannot be bent.

[0004] Therefore, in lithium-ion batteries using conventional electrolytes, batteries formed in the shape of a cable in Non-Patent Document 1 have been studied. In addition, batteries in which extremely small lithium-ion batteries in Non-Patent Document 2 are joined with flexible electrical wiring have been studied. In addition, batteries in which an internal battery is sealed with an elastomer such as silicone rubber in Non-Patent Document 3 and connected with a spring-shaped wiring have been studied. In addition, batteries with a structure such as kirigami in Non-Patent Document 4 have been studied. In addition, batteries in which lithium-ion batteries in Non-Patent Document 5 are formed in a fibrous shape have been studied. However, in these batteries, there is a problem that the volume ratio occupied by the wiring support and the exterior body connecting the internal batteries is high, and the expected energy density of the entire battery is significantly reduced.

[0005] In addition, a method of providing flexibility by making the lithium-ion battery itself thin has been adopted. However, since it has an electrolytic solution that can cause ignition, there are significant problems with the safety of wearing the battery. Even in the thin lithium polymer battery using the polymer electrolyte of Patent Document 1, it can have flexibility, but when it is bent under an excessive load, it easily short-circuits, so there are issues with safety.

[0006] All-solid-state batteries using flame-retardant or non-combustible materials have high safety. However, in a sulfide-based all-solid-state battery manufactured by press-molding a powder battery material as in Patent Document 2, it is necessary to tightly press with a strong force so that the solid electrolyte does not peel off due to the expansion and contraction of the active material accompanying charge and discharge, and since it has a strong and rigid exterior body or support body that does not let go of that force, it cannot be bent. Similarly, an oxide-based all-solid-state battery manufactured by a sintering method is also hard and cannot be bent. In a thin-film all-solid-state battery manufactured by a thin-film process such as a sputtering method, since it is impossible to provide an active material layer with a sufficient thickness, it is difficult to manufacture a battery with a storage capacity exceeding several mAh.

[0007] An all-solid-state lithium polymer battery in which an active material and a separator are adhered with a solid polymer electrolyte does not require a strong exterior body and has flexibility, and the structure and the manufacturing method of the battery of Patent Document 3 are preferable. However, in reality, when it becomes larger than several mAh (area is 4 cm 2 ), due to a phenomenon peculiar to solid polymers in which the active material and the separator easily adhere to each other, the battery reaction between lithium ions and the active material is inhibited, and as a result, there is a problem that lithium dendrites are generated during charging and it easily short-circuits.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Non-Patent Documents

[0009]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

Non-Patent Document 5

Non-Patent Document 6

Summary of the Invention

Problems to be Solved by the Invention

[0010] One object of an embodiment of the present invention is to provide a flexible all-solid-state battery having a weight energy density comparable to that of a conventional lithium-ion battery using an electrolytic solution and having high safety such that it does not short-circuit even when folded by an excessive bending load.

Means for Solving the Problems

[0011] According to one embodiment of the present invention, a flexible all-solid-state battery is provided, which includes a layer of a solid polymer electrolyte disposed between a layer holding a solid polymer electrolyte and a layer including a negative electrode active material.

[0012] In the flexible all-solid-state battery, the separator may be a woven, knitted, or non-woven fabric of inorganic fibers or polymer fibers having a thickness in the range of 1 μm to 100 μm, 1 g / m 2 to 70 g / m 2 , or an oxide ceramic particle layer containing oxide ceramic particles having a particle diameter in the range of 1 μm to 20 μm at a filling rate in the range of 5% to 60%, or a composite of a woven, knitted, or non-woven fabric and oxide ceramic particles.

[0013] In the flexible all-solid-state battery, the thickness of the layer of the solid polymer electrolyte may be in the range of 500 nm to 60 μm.

[0014] In the flexible all-solid-state battery, a negative electrode sheet composed of a layer including a negative electrode active material and a negative electrode current collector in contact with the negative electrode active material is provided, and the negative electrode sheet may have a capacity of 0.1 mAh / cm 2 to 7 mAh / cm 2 .

[0015] In the flexible all-solid-state battery, a positive electrode sheet having a capacity of 0.1 mAh / cm 2 to 7 mAh / cm 2 may be further provided.

[0016] In the flexible all-solid-state battery, the thickness of the layer of the solid polymer electrolyte disposed between the layer in which the solid polymer electrolyte is held by the separator and the layer including the positive electrode active material may be in the range of 500 nm to 60 μm.

[0017] The flexible all-solid-state battery may have an electrode area larger than 1.77 cm 2 .

[0018] The flexible all-solid-state battery may have a folded shape.

[0019] Further, according to an embodiment of the present invention, a polymer solution in which a polymer electrolyte and an initiator are mixed is applied to a composite layer including an active material holding a solid polymer electrolyte, a flat plate or film is laminated, and crosslinking is performed while applying a weight in the range of 1 kPa to 500 kPa. Then, the polymer solution is applied onto a positive electrode sheet or a negative electrode sheet, a separator is placed on the applied polymer solution to impregnate the polymer solution, and after laminating with the negative electrode sheet or the positive electrode sheet, it is sandwiched between flat plates or films and crosslinked while applying a weight in the range of 1 kPa to 500 kPa, thereby manufacturing a flexible all-solid-state battery having solid polymer electrolyte layers on both sides of a separator holding a solid polymer electrolyte.

[0020] In the method for manufacturing a flexible all-solid-state battery, an all-solid-state battery having a solid polymer electrolyte layer may be sandwiched between flat plates or films, and initial charging may be performed while applying a weight of 1 kPa to 1 MPa.

Advantages of the Invention

[0021] According to the present invention, it is possible to provide a flexible all-solid-state battery having a weight energy density comparable to that of a conventional lithium-ion battery using an electrolytic solution and having high safety such that it does not short-circuit even when folded under excessive bending load.

Brief Description of the Drawings

[0022]

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Figure 15

Embodiments for Carrying Out the Invention

[0023] Hereinafter, a flexible all-solid-state battery and a method for manufacturing the same according to the present invention will be described with reference to the drawings. Note that the flexible all-solid-state battery and the method for manufacturing the same according to the present invention are not construed as being limited to the description of the following embodiments and examples. In the drawings referred to in the present embodiment and the examples described later, the same parts or parts having the same functions are denoted by the same reference numerals, and the repeated description thereof is omitted.

[0024] As a result of intensive studies on a new structure of a lithium-ion battery and a method for manufacturing the same that can solve the above-described problems of the prior art, the inventors have found that by providing layers of a solid polymer electrolyte on both sides of a layer of a separator holding a solid polymer electrolyte, it is possible to construct a flexible all-solid battery that can be charged and discharged and is not short-circuited even when bent, with a size of 1 cm 2 or larger.

[0025] [Embodiment 1] FIG. 1 is a cross-sectional end view of an internal battery 1 of a flexible all-solid battery according to an embodiment of the present invention. The internal battery 1 includes a separator layer 10 holding a solid polymer electrolyte and a layer 9 including a negative electrode active material. The internal battery 1 further includes a layer 11 of a solid polymer electrolyte disposed between the separator layer 10 holding the solid polymer electrolyte and the layer 9 including the negative electrode active material. The internal battery 1 further includes a layer 8 including a positive electrode active material on a surface of the separator layer 10 holding the solid polymer electrolyte on a side opposite to the surface on which the layer 9 including the negative electrode active material is disposed.

[0026] [Separator layer holding a solid polymer electrolyte] In one embodiment, the separator layer 10 holding the solid polymer electrolyte includes the solid polymer electrolyte and a separator 4. The separator 4 is made of a material that does not react with lithium ions and can be arranged in a sheet-like structure. The separator 4 has pores 4-1 that penetrate the sheet-like structure and in which the solid polymer electrolyte can be arranged. In other words, the separator 4 has openings 4-2 on both sides of the sheet-like structure and has pores 4-1 in which at least two openings 4-2 arranged corresponding to the sheet-like structure are connected. In the present embodiment, as the separator 4, one selected from glass fiber, a woven fabric of aramid fiber, and alumina particles can be used, but is not limited thereto.

[0027] The pores disposed in the separator 4 have openings sized such that when the polymer solution of the polymer crosslinks to form a solid polymer electrolyte, the solid polymer electrolyte does not escape from the pores 4-1. Specifically, the separator 4 is composed of fibers with a thickness of 40 μm or less per fiber and is a woven fabric, knitted fabric, or non-woven fabric of inorganic fibers or polymer fibers having a thickness of about 1 μm to 100 μm. Or, the separator 4 is a woven fabric, knitted fabric, or non-woven fabric of inorganic fibers or polymer fibers having openings of about 1 μm to 2 mm. Or, the separator 4 is a woven fabric, knitted fabric, or non-woven fabric of inorganic fibers or polymer fibers having a basis weight of about 1 g / m 2 to 70 g / m 2 Or, the separator 4 is an oxide ceramic particle layer in which oxide ceramic particles with a particle size of 1 μm to 20 μm are arranged at a filling rate of about 10% to 60%. Or, the separator 4 is a composite of these woven fabrics, knitted fabrics, or non-woven fabrics and oxide ceramic particles. In FIG. 1, as an example of the separator 4, an oxide ceramic particle layer formed by arranging oxide ceramic particles is shown, but it is not limited thereto. Examples of inorganic fibers include fibers of alumina, silica, and compounds containing them. Examples of polymer fibers include fibers of nylon, aramid, vinylon, vinylidene, polyvinyl chloride, polyester, acrylic, polyethylene, polypropylene, polyurethane, polyvinyl chloride, polylactic acid, polytetrafluoroethylene (PTFE), and polyvinylidene fluoride. Examples of oxide ceramic particles include particles of alumina, silica, titania, magnesia, zirconia, zinc oxide, and compounds containing them.

[0028] As the solid polymer electrolyte, a material with a product of ionic conductivity and transference number better than 5.0×10 -6 S / cm at room temperature (25°C) is preferred, with an ionic conductivity of 2.0×10 -5 S / cm at room temperature (25°C) and 1.0×10 -4Materials superior to S / cm are preferred. For example, the ion-conductive polymers containing lithium ions described in Non-Patent Document 6 can be used. More specifically, a mixture of a polymer having a poly(propylene glycol)-pol(ethylene glycol)-poly(propylene glycol) (PPG-PEG-PPG) backbone and having a 2-ureido-4-pyrimidone motif with a quadruple bond introduced into the backbone and lithium ions can be suitably used as a solid polymer electrolyte.

[0029] Also, in one embodiment, examples of the starting material used when forming the solid polymer electrolyte by a polymerization reaction include, but are not limited to, starting materials such as azobisisobutyronitrile disclosed in Prior Document 3.

[0030] The solid polymer electrolyte is preferably disposed in the pores 4-1 of the separator 4 and continuously disposed in the inner pores 4-1 so as to connect the openings 4-2 disposed on both sides of the separator 4.

[0031] <Layer comprising a negative electrode active material> The layer 9 comprising a negative electrode active material includes a negative electrode composite material layer 9-1 and the above-described solid polymer electrolyte. The negative electrode composite material layer 9-1 is a layer in which the negative electrode active material 6 is formed in a sheet shape. As the negative electrode active material 6, for example, graphite or lithium titanate is preferred, but it is not limited thereto. In addition to the negative electrode active material 6, the negative electrode composite material layer 9-1 may further contain a binder such as polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE), or a conductive auxiliary agent such as carbon nanotubes (for example, VGCF (registered trademark)).

[0032] Further, a negative electrode current collector 7 can be disposed on the surface of the negative electrode composite layer 9-1 facing the surface on which the solid polymer electrolyte layer 11 is disposed, thereby forming a negative electrode sheet 13. In other words, the negative electrode sheet 13 has a structure in which a layer 9 including a negative electrode active material is disposed on the negative electrode current collector 7. Therefore, the negative electrode sheet 13 includes the negative electrode current collector 7, the negative electrode composite layer 9-1, and the solid polymer electrolyte disposed inside the negative electrode composite layer 9-1.

[0033] In one embodiment, as the negative electrode current collector 7, a copper foil is exemplified, but a foil having electrical conductivity and flexibility that does not react with and corrode a solid polymer electrolyte such as a gold foil or a platinum foil can be used. The thickness of the negative electrode current collector 7 only needs to have appropriate flexibility. For example, it is in the range of 500 nm to 100 μm, preferably in the range of 5 μm to 30 μm, and more preferably has a thickness of 12 μm.

[0034] The capacity of the negative electrode sheet 13 only needs to be larger than the capacity of the positive electrode sheet 12. For example, it is in the range of 0.1 mAh / cm 2 to 7 mAh / cm 2 and preferably has a capacity of about 1.6 mAh / cm 2 .

[0035] <Layer of solid polymer electrolyte> The solid polymer electrolyte layer 11 is a layer disposed between the separator layer 10 holding the solid polymer electrolyte and the layer 9 including the negative electrode active material, and is a layer including the above-described solid polymer electrolyte.

[0036] The thickness of the solid polymer electrolyte layer 11 only needs to be such that the separator 4 and the negative electrode active material 6 constituting the negative electrode composite layer 9-1 do not adhere to each other. Specifically, it is preferably in the range of 500 nm to 60 μm, or 2 μm to 30 μm. Further, the solid polymer electrolyte layer 11 may include an inorganic solid electrolyte having a reduction potential lower than that of the negative electrode active material such as a garnet-type solid electrolyte.

[0037] <Layer including positive electrode active material> The layer 8 comprising the positive electrode active material includes a positive electrode composite material layer 8-1 and the above-described solid polymer electrolyte. The positive electrode composite material layer 8-1 is a layer in which the positive electrode active material 3 is formed in a sheet shape. As the positive electrode active material 3, for example, a material selected from lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel manganese cobaltate, and lithium iron phosphate is preferable, but it is not limited thereto. The positive electrode composite material layer 8-1 may further contain a binder such as polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE), or a conductive aid such as carbon nanotubes (e.g., VGCF (registered trademark)) in addition to the positive electrode active material 3.

[0038] Also, the positive electrode current collector 2 can be disposed on the surface of the positive electrode composite material layer 8-1 facing the surface on which the separator layer 10 holding the solid polymer electrolyte is disposed, thereby forming the positive electrode sheet 12. In other words, the positive electrode sheet 12 has a structure in which the layer 8 comprising the positive electrode active material is disposed on the positive electrode current collector 2. Therefore, the positive electrode sheet 12 includes the positive electrode current collector 2, the positive electrode composite material layer 8-1, and the solid polymer electrolyte disposed inside the positive electrode composite material layer 8-1.

[0039] In one embodiment, as the positive electrode current collector 2, an aluminum foil is exemplified, but a flexible and electrically conductive foil that does not react with and corrode the solid polymer electrolyte and is selected from stainless steel foil, titanium foil, gold foil, platinum foil, etc. can be used. The thickness of the positive electrode current collector 2 only needs to have appropriate flexibility, for example, it is in the range of 500 nm to 100 μm, preferably in the range of 5 μm to 30 μm, and preferably has a thickness of 12 μm.

[0040] The capacity of the positive electrode sheet 12 only needs to be smaller than the capacity of the negative electrode sheet 13. For example, it is in the range of 0.1 mAh / cm 2 to 7 mAh / cm 2 and preferably has a capacity of about 1.5 mAh / cm 2 .

[0041] In this embodiment, layer 10 of the separator holding the solid polymer electrolyte and layer 8 provided with the positive electrode active material are arranged in close contact. In the internal battery 1 according to this embodiment, the solid polymer electrolyte contained in layer 9 provided with the negative electrode active material, the solid polymer electrolyte contained in layer 10 of the separator holding the solid polymer electrolyte, and the solid polymer electrolyte contained in layer 8 provided with the positive electrode active material are arranged continuously, and lithium ion conductivity from the positive electrode active material 3 to the negative electrode active material 6 can be imparted through the separator 4.

[0042] <All-solid-state battery> FIG. 2 is a schematic diagram of a flexible all-solid-state battery 18 according to an embodiment of the present invention. The internal battery 1 in which the positive electrode current collector 2, layer 8 provided with the positive electrode active material, layer 10 of the separator holding the solid polymer electrolyte, layer 11 of the solid polymer electrolyte, layer 9 provided with the negative electrode active material, and the negative electrode current collector 7 are sequentially laminated is covered with the exterior body 17, whereby the flexible all-solid-state battery 18 according to this embodiment can be configured. The exterior body 17 can be formed, for example, by vacuum-packing the internal battery 1 with a laminate film, or by wrapping it with glass fiber or aramid fiber and then impregnating it with a resin such as an epoxy resin.

[0043] The flexible all-solid-state battery 18 according to this embodiment suppresses the close contact between the separator 4 and the negative electrode active material 6, and prevents the generation of lithium dendrites in the low potential region in the battery reaction between graphite and lithium ions, so that it has flexibility enabling normal charge and discharge and does not short-circuit even when bent. An all-solid-state battery larger than 1 cm 2 can be realized.

[0044] [Embodiment 2] In Embodiment 1, a flexible all-solid-state battery 18 having an internal battery 1 provided with a solid polymer electrolyte layer 11 disposed between a separator layer 10 holding a solid polymer electrolyte and a layer 9 provided with a negative electrode active material was described. In the present embodiment, an internal battery 1a provided with a solid polymer electrolyte layer 11 will be described, which is disposed between the separator layer 10 holding the solid polymer electrolyte and the layer 9 provided with the negative electrode active material, and between the separator layer 10 holding the solid polymer electrolyte and the layer 8 provided with the positive electrode active material.

[0045] FIG. 3 is a cross-sectional end view of an internal battery 1a of a flexible all-solid-state battery according to an embodiment of the present invention. In FIG. 3, an example using a separator 4a composed of a woven fabric, knitted fabric, or non-woven fabric of inorganic fibers or polymer fibers is shown. However, in the internal battery 1a, a separator 4 composed of an oxide ceramic particle layer may be used. The separator 4a has pores 4a-1 penetrating through a sheet-like structure and capable of disposing a solid polymer electrolyte. In other words, the separator 4a has openings 4a-2 on both surfaces of the sheet-like structure, and has pores 4a-1 in which at least two openings 4a-2 arranged corresponding to the sheet-like structure are connected.

[0046] In the internal battery 1a, solid polymer electrolyte layers 11 are respectively disposed on both surfaces of a separator layer 10a holding a solid polymer electrolyte. On one of the solid polymer electrolyte layers 11, a layer 9 provided with a negative electrode active material is disposed facing the separator 4, and on the other solid polymer electrolyte layer 11, a layer 8 provided with a positive electrode active material is disposed. A negative electrode current collector 7 is disposed on the surface of the layer 9 provided with the negative electrode active material facing the separator 4. Also, a positive electrode current collector 2 is disposed on the surface of the layer 8 provided with the positive electrode active material facing the separator 4.

[0047] Note that the positive electrode current collector 2, the negative electrode current collector 7, the layer 8 provided with the positive electrode active material, the layer 9 provided with the negative electrode active material, and the solid polymer electrolyte layer 11 may have the same configurations as those described in Embodiment 1, and detailed descriptions thereof are omitted.

[0048] By using the internal battery 1a instead of the internal battery 1, the flexible all-solid-state battery 18 can be configured. The exterior body 17 covering the internal battery 1a may have the same configuration as that described in Embodiment 1, and detailed description thereof is omitted.

[0049] The flexible all-solid-state battery 18 according to the present embodiment suppresses the adhesion between the separator 4a and the negative electrode active material 6 and the adhesion between the separator 4a and the positive electrode active material 3, and in the battery reaction between graphite and lithium ions, it has flexibility that enables normal charge and discharge and does not short-circuit even when bent, and can realize an all-solid-state battery larger than 1 cm 2 or more.

[0050] [Embodiment 3] As Embodiment 3, an electric unit 21 in which a plurality of internal batteries 1 of Embodiment 1 or a plurality of internal batteries 1a of Embodiment 2 are stacked will be described. FIG. 4 is an exploded perspective view of the electric unit 21 according to the present embodiment. In the electric unit 21, an internal battery 1 and an internal battery 20 in which the upper and lower sides of the internal battery 1, that is, the arrangement of the positive electrode sheet 12 and the negative electrode sheet 13, are configured in reverse with respect to the separator layer 10 holding the solid polymer electrolyte are stacked to form an internal battery laminate 19. The internal battery 20 may have the same configuration as the internal battery 1 except that the arrangement of the positive electrode sheet 12 and the negative electrode sheet 13 is reversed, and detailed description thereof is omitted. In the internal battery laminate 19, the positive electrode current collector 2 of the adjacent internal battery 1 and the positive electrode current collector 2 of the internal battery 20 are adjacent, and the negative electrode current collector 7 of the internal battery 20 and the negative electrode current collector 7 of the internal battery 1 are stacked so as to be adjacent.

[0051] The exterior body 17 covers the internal battery laminate 19 to configure the electric unit 21. The exterior body 17 may have the same configuration as that described in Embodiment 1, and detailed description thereof is omitted.

[0052] Also, in the electric unit 21, an internal battery 1a can be used instead of the internal battery 1. In this case, the internal battery 20 is an internal battery in which the arrangement of the positive electrode sheet 12 and the negative electrode sheet 13 with respect to the internal battery 1a is configured in reverse with respect to the separator layer 10 holding the solid polymer electrolyte.

[0053] The electric unit 21 according to the present embodiment suppresses the adhesion between the separator 4 and the negative electrode active material 6, and in the battery reaction between graphite and lithium ions, in order to prevent the generation of lithium dendrites in the low potential region, it has flexibility that enables normal charge and discharge and does not short-circuit even when bent, and can realize an electric unit larger than 1 cm 2 or more.

[0054] [Manufacturing method of internal battery] Taking the internal battery 1a described in Embodiment 2 as an example, the manufacturing method of the internal battery will be described. FIGS. 5 to 7 are schematic diagrams of the manufacturing method of the internal battery 1a according to an embodiment of the present invention. A positive electrode composite layer 8-1 having a positive electrode active material 3 is impregnated with a polymer solution 14 on the positive electrode current collector 2 (FIG. 5(1)), and the polymer solution 14 is impregnated (FIG. 5(2)). The positive electrode composite layer 8-1 impregnated with the polymer solution 14 and the positive electrode current collector 2 are sandwiched between two glass or metal plates 16, and the polymer contained in the polymer solution 14 is crosslinked by heat or light while applying pressure (FIG. 5(3)) to produce a positive electrode sheet 12 (FIG. 5(4)). Subsequently, a polymer solution is further applied to the positive electrode sheet 12 (FIG. 5(5)), and similarly, it is sandwiched between plates 16 and crosslinked while applying pressure (FIG. 5(6)). Thereby, a layer 11 of solid polymer electrolyte can be laminated on the positive electrode sheet 12 (FIG. 5(7)). When crosslinking the polymer while applying pressure, a polymer film 15 may be provided between the plate 16 and the polymer solution 14. The polymer film 15 is preferably a PET film, a polyethylene film, etc., but is not limited thereto.

[0055] The negative electrode composite layer 9-1 provided with the negative electrode active material 6 on the negative electrode current collector 7 (Fig. 6(1)) is impregnated with the polymer solution 14 (Fig. 6(2)). The negative electrode composite layer 9-1 impregnated with the polymer solution 14 and the negative electrode current collector 7 are sandwiched between two glass or metal plates 16, and the polymer contained in the polymer solution 14 is cross-linked by heat or light while applying pressure (Fig. 6(3)) to produce the negative electrode sheet 13 (Fig. 6(4)). Subsequently, the polymer solution 14 is further applied to the negative electrode sheet 13 (Fig. 6(5)), and in the same manner, it is sandwiched between the plates 16 and cross-linked while applying pressure (Fig. 6(6)), so that the layer 11 of the solid polymer electrolyte can be laminated on the negative electrode sheet 13 (Fig. 6(7)). When cross-linking while applying pressure, a polymer film 15 may be provided between the plate 16 and the polymer solution 14. The polymer film 15 is preferably a PET film, a polyethylene film, etc., but is not limited thereto.

[0056] Next, after laminating the positive electrode sheet 12 and the negative electrode sheet 13 with the layer 11 of the solid polymer electrolyte laminated thereon via the separator 4 impregnated with the polymer solution 14 (Fig. 7(1)), these are sandwiched between two plates and cross-linked by heat while applying pressure to manufacture the battery structure (Fig. 7(2)). Thereafter, the internal battery 1a is manufactured by performing initial charging while being sandwiched between the two plates 16 and applying pressure. Subsequently, the plates 16 are removed, and only the internal battery 1a is taken out (Fig. 7(3)), and by arranging and sealing it in a laminate film or a fiber-reinforced plastic, the flexible all-solid-state battery 18 provided with the exterior body 17 can be manufactured. Note that after the initial charging is completed, it may be discharged to such an extent that over-discharge does not occur, and then the internal battery is taken out to form the exterior body 17.

[0057] In one embodiment, the pressure applied when cross-linking the polymer is preferably in the range of 1 kPa to 500 kPa, or in the range of 5 kPa to 300 kPa.

[0058] In one embodiment, the pressure applied during initial charging is preferably in the range of 1 kPa to 1 MPa, or in the range of 5 kPa to 300 kPa.

Example

[0059] <Example 1>Internal battery 1a Next, a preferred specific manufacturing method of the flexible all-solid-state battery described in the above-described embodiment will be described with reference to FIGS. 5 to 7. Hereinafter, the steps of the examples and comparative examples were carried out in a dry booth or in a vacuum with a dew point temperature of -40°C or lower.

[0060] A portion where the positive electrode composite layer 8-1 of a commercially available positive electrode sheet (HS-LIB-P-Co-003 or HS-LIB-P-NMC-001, Takizawa Co., Ltd.) was coated was cut out to be 37 mm × 47 mm, and a portion where the positive electrode composite was not coated and the aluminum foil which is the positive electrode current collector 2 was exposed was cut out as an electrode terminal with a width of 10 mm and a length of 15 mm. Then, the positive electrode composite layer 8-1 was impregnated with a polymer solution in which a commercially available polymer electrolyte and an initiator were mixed (in the crosslinked solid polymer electrolyte, the product of the ionic conductivity and the transference number is about 1.0×10 -4 S / cm) (FIG. 5(2)), a laminate film 15 (Diamiron (registered trademark) M, thickness 70 μm, Mitsubishi Chemical Corporation) cut out to be 50 mm × 60 mm was laminated, sandwiched between two glass plates 16 with a thickness of 5 mm, and further sandwiched between two alloy tool steels (SKD11 vacuum quenched, 3 mm thick). M3 screws were passed through four screw holes (eight holes in two sheets) and tightened with a torque of 3 cN·m, and crosslinked at the same temperature as in Patent Document 3 (FIG. 5(3)). Subsequently, the laminate film 15 was peeled off (FIG. 5(4)), the polymer solution 14 was applied to the positive electrode composite layer 8-1 provided with the solid polymer electrolyte (FIG. 5(5)). Similarly, the laminate film 15 was laminated and sandwiched between the glass plate 16 and the alloy tool steel, the M3 screw was tightened with a torque of 3 cN·m, and crosslinked by heat in the same manner (FIG. 5(6)). The laminate film 15 was peeled off, and the layer 11 of the solid polymer electrolyte was laminated on the positive electrode sheet 12 (FIG. 5(7)).

[0061] Next, a portion where the negative electrode composite layer 9-1 of a commercially available negative electrode sheet (HS-LIB-N-Gr-001, Takizawa Co., Ltd.) was coated was cut out as an electrode terminal with a width of 10 mm and a length of 15 mm at a position different from that of the above positive electrode sheet 12, with a size of 40 mm × 50 mm. A portion where the copper foil, which is the negative electrode current collector 7 and where the negative electrode composite layer 9-1 was not coated, was exposed. Then, the negative electrode composite was impregnated with the polymer solution 14 (Fig. 6(2)), a laminated film 15 cut out to 50 mm × 60 mm was laminated, sandwiched between two 5 mm-thick glass plates 16, further sandwiched between two alloy tool steels, and M3 screws were passed through four screw holes (eight holes in two sheets) and tightened with a torque of 3 cN·m, and similarly cross-linked by heat (Fig. 6(3)). Subsequently, the laminated film 15 was peeled off (Fig. 6(4)), the polymer solution 14 was applied to the negative electrode composite layer 9-1 provided with the solid polymer electrolyte (Fig. 6(5)), the laminated film 15 was laminated in the same manner, sandwiched between the glass plate 16 and the alloy tool steel, and the M3 screw was tightened with a torque of 3 cN·m (Fig. 6(6)), the laminated film 15 was peeled off, and the layer 11 of the solid polymer electrolyte was laminated on the negative electrode sheet 13 (Fig. 6(7)).

[0062] Next, the polymer solution 14 was applied onto the layer 11 of the solid polymer electrolyte on the negative electrode sheet 13. Then, as the separator 4a, a glass cloth cut out to 50 mm × 60 mm (fiber thickness 5 μm, 24 g / m 2 , thickness 20 μm, see Fig. 8) was placed on the applied polymer solution 14 and impregnated, and after being bonded to the positive electrode sheet 12 on which the layer 11 of the solid polymer electrolyte was laminated (Fig. 7(1)), in order to enable the extraction of the electrode terminal, it was sandwiched between two laminated films 15, which was further sandwiched between the glass plate 16 and the alloy tool steel, and the M3 screw was tightened with a torque of 3 cN·m and cross-linked by heat in the same manner to obtain a structure having an internal battery (Fig. 7(2)). Twenty-two of these structures were fabricated, and none of them were short-circuited.

[0063] Next, with the structure having the internal battery without removing the M3 screw, the electrode terminals were connected to a battery charge and discharge device (manufactured by Hokuto Denko), and in an environment of 60°C, HS-LIB-P-Co-003 was charged at a constant current of 0.1 C until it reached 4.2 V, and HS-LIB-P-NMC-001 was charged at a constant current of 0.1 C until it reached 4.3 V. Then, the current was controlled so that the voltage remained constant for 1 hour or more. After that, it was discharged at a constant current of 0.1 C until it reached 3.0 V. The typical charge and discharge curves are shown in FIG. 9. After confirming that typical charge and discharge curves of about 25 mAh to 27 mAh were obtained, the internal battery 1a was fabricated by removing the M3 screw and the glass plate, alloy tool steel, and laminate film 15. FIG. 10 is a cross-sectional SEM image of the fabricated internal battery 1a. It can be confirmed that the solid polymer electrolyte layer 11 is provided so that the glass cloth as the separator 4 does not contact the negative electrode active material 6 and the positive electrode active material 3. Out of the 22 fabricated internal batteries 1a, normal charge and discharge were possible for 19 of them.

[0064] FIG. 11 is a cross-sectional SEM image of the internal battery 1a of Example 1. In the internal battery 1a, it became clear that the solid polymer electrolyte layer 11 was formed with a film thickness of 2 μm to 30 μm.

[0065] Next, the internal battery was wrapped with glass cloth so that the electrode terminals of the positive and negative electrodes could be taken out, and the exterior body 17 was formed by impregnating the glass cloth with a flexible epoxy resin (Mitsubishi Chemical Corporation) by the vacuum impregnation method (VaRTM), and the flexible all-solid-state battery 18 was fabricated. FIG. 12 is a photograph when the flexible all-solid-state battery 18 was connected with a propeller attached to the rotating shaft of the motor. Since the motor could be rotated even when bent (c), folded (d) and (e), cut off by clamping (f), pressed with a finger, or tapped with the handle of the clamp, it was confirmed that it had high safety.

[0066] In the same process as above, a negative electrode sheet with a diameter of 13 mm and a positive electrode sheet of 1 cm 2Four small-sized batteries were fabricated using a circle, and it was confirmed that all four could be charged and discharged normally. The separators used at that time were the glass cloth with a thickness of 20 μm described above, and glass fibers and aramid fibers with a thickness of 65 μm (opening diameter of about 1 mm, see Fig. 13).

[0067] <Example 2> Internal battery 1 A commercially available positive electrode sheet (HS-LIB-P-NMC-001, Takizawa Co., Ltd.) was cut out in a circle with a diameter of 1 cm. 2 Alumina particles with a particle size of 10 μm were adhered onto the positive electrode composite layer 8-1 as the separator 4. Then, it was impregnated with a polymer solution, a laminate film was laminated to cover the polymer solution, sandwiched between plates 16, crosslinked by heat while applying a pressure of 250 MPa, and the laminate film was peeled off, so that a layer 10 of a separator provided with a solid polymer electrolyte was laminated so as to contact the positive electrode sheet 12.

[0068] Next, a commercially available negative electrode sheet (HS-LIB-N-Gr-001, Takizawa Co., Ltd.) was cut out with a diameter of 13 mmφ. Then, the negative electrode composite layer 9-1 was impregnated with a polymer solution, a laminate film was laminated to cover the polymer solution, sandwiched between plates 16, crosslinked by heat while applying a pressure of 180 MPa, and the laminate film was peeled off, so that the negative electrode sheet 13 was fabricated.

[0069] Next, a polymer solution 14 was applied onto the negative electrode sheet 13, and the positive electrode sheet 12 with a layer 10 of a separator provided with a solid polymer electrolyte laminated thereon was bonded, sandwiched between conductive plates 16, and crosslinked by heat in the same manner while applying a pressure of 250 MPa, so as to obtain a structure provided with the internal battery 1. Two of these structures were fabricated, and none of them were short-circuited.

[0070] Next, while maintaining the structure with the internal battery under a load of 250 MPa, each plate 16 in contact with the positive electrode current collector 2 and the negative electrode current collector 2 was connected to a battery charging / discharging device (Hokuto Electric Works Co., Ltd.). In an environment of 60°C, it was charged with a constant current of 0.1 C until it reached 4.3 V, and then the current was controlled so that the voltage remained constant for 1 hour or more. Thereafter, it was discharged with a constant current of 0.1 C until it reached 3.0 V. Out of the two fabricated internal batteries 1, normal charging and discharging were possible with both.

[0071] <Comparative Example> Internal battery by a process without providing a solid polymer electrolyte layer A portion coated with the positive electrode mixture of a commercially available positive electrode sheet (HS-LIB-P-Co-003 or HS-LIB-P-NMC-001, Hokusen Co., Ltd.) was cut out as an electrode terminal with dimensions of 37 mm × 47 mm, and a portion where the positive electrode mixture was not coated and the aluminum foil was exposed was cut out as an electrode terminal with a width of 10 mm and a length of 15 mm. Thereafter, it was impregnated with a polymer solution, laminated with a laminate film cut out to 50 mm × 60 mm, sandwiched between two glass plates, further sandwiched between two alloy tool steels, M3 screws were passed through four screw holes (eight holes in two) and tightened with a torque of 3 cN·m, and after crosslinking with heat in the same manner, the laminate film was peeled off to fabricate the positive electrode sheet 1A.

[0072] Next, a portion coated with the negative electrode mixture of a commercially available negative electrode sheet (HS-LIB-N-Gr-001, Hokusen Co., Ltd.) was cut out as an electrode terminal with dimensions of 40 mm × 50 mm, and a portion where the negative electrode mixture was not coated and the copper foil was exposed was cut out as an electrode terminal with a width of 10 mm and a length of 15 mm at a position different from that of the above positive electrode sheet. Thereafter, the negative electrode mixture was impregnated with a polymer solution, laminated with a laminate film cut out to 50 mm × 60 mm, sandwiched between two glass plates with a thickness of 5 mm, further sandwiched between two alloy tool steels, M3 screws were passed through four screw holes (eight holes in two) and tightened with a torque of 3 cN·m, and after crosslinking with heat in the same manner, the laminate film was peeled off to fabricate the negative electrode sheet 1A.

[0073] Next, in the same manner as in the prior art document 3, a polymer solution was applied onto the negative electrode sheet 1A, and then a glass cloth (fiber thickness: 5 μm, 24 g / m 2 , thickness: 20 μm) cut out to 50 mm × 60 mm was placed on the polymer solution-coated surface for impregnation and then bonded to the positive electrode sheet 1A. Thereafter, in order to enable extraction of the electrode terminals, it was sandwiched between two laminate films, which were further sandwiched between a glass plate and an alloy tool steel, and an M3 screw was tightened with a torque of 3 cN·m and crosslinked by heat in the same manner to obtain a structure provided with an internal battery. Hereinafter, this structure provided with the internal battery is referred to as Comparative Battery 1A-L. Eight of these batteries were fabricated.

[0074] In the same process as Comparative Battery 1A-L, a small battery was fabricated with a negative electrode sheet having a diameter of 13 mm and a positive electrode sheet having a diameter of 1 cm 2 . This structure provided with the internal battery is referred to as Comparative Battery 1A-S.

[0075] A portion of a commercially available positive electrode sheet (HS-LIB-P-NMC-001, Takizawa Co., Ltd.) where the positive electrode composite material was coated was cut out to 37 mm × 47 mm or 27 mm × 47 mm, and a portion where the positive electrode composite material was not coated and the aluminum foil was exposed was cut out as an electrode terminal with a width of 10 mm and a length of 15 mm. Alumina particles with a particle size of 2 μm were adhered onto the positive electrode composite material layer. Thereafter, it was impregnated with a mixed solution of a polymer solution and crosslinked by heat in the same manner to fabricate a positive electrode sheet. This positive electrode sheet is referred to as positive electrode sheet 1B.

[0076] A portion of a commercially available positive electrode sheet (HS-LIB-P-NMC-001, Takizawa Co., Ltd.) where the positive electrode composite material was coated was cut out to 37 mm × 47 mm or 27 mm × 47 mm, and a portion where the positive electrode composite material was not coated and the aluminum foil was exposed was cut out as an electrode terminal with a width of 10 mm and a length of 15 mm. Thereafter, it was impregnated with a mixed solution of a polymer solution and crosslinked by heat in the same manner to fabricate a positive electrode sheet. This positive electrode sheet is referred to as positive electrode sheet 1C.

[0077] Next, a portion of the commercially available negative electrode sheet (HS-LIB-N-Gr-001, Takizawa Co., Ltd.) where the negative electrode composite material was coated was cut out as an electrode terminal with a width of 10 mm and a length of 15 mm at a position different from that of the above positive electrode sheet, with dimensions of 40 mm × 50 mm or 30 mm × 50 mm. A portion where the negative electrode composite material was not coated and the copper foil was exposed was also cut out at a different position from the above positive electrode sheet, with the same width and length as the electrode terminal. Alumina particles with a particle size of 2 μm were adhered onto the negative electrode composite material layer. Thereafter, the mixture solution of the polymer solution was impregnated, and crosslinked by heat in the same manner to produce a positive electrode sheet. This negative electrode sheet is referred to as negative electrode sheet 1B.

[0078] Next, a portion of the commercially available negative electrode sheet (HS-LIB-N-Gr-001, Takizawa Co., Ltd.) where the negative electrode composite material was coated was cut out as an electrode terminal with a width of 10 mm and a length of 15 mm at a position different from that of the above positive electrode sheet, with dimensions of 40 mm × 50 mm or 30 mm × 50 mm. A portion where the negative electrode composite material was not coated and the copper foil was exposed was also cut out at a different position from the above positive electrode sheet, with the same width and length as the electrode terminal. Thereafter, the mixture solution of the polymer solution was impregnated, and crosslinked by heat in the same manner to produce a positive electrode sheet. This negative electrode sheet is referred to as negative electrode sheet 1C.

[0079] A polymer solution was applied onto negative electrode sheet 1B or negative electrode sheet 1C. Thereafter, a glass cloth (fiber thickness: 5 μm, 24 g / m 2 , thickness: 20 μm) cut out to 50 mm × 60 mm was placed on the polymer solution-coated surface and impregnated, and then laminated with positive electrode sheet 1B or positive electrode sheet 1C. Thereafter, it was sandwiched between two laminated films so that the electrode terminal could be taken out, then sandwiched between a glass plate, and further sandwiched between alloy tool steel, and an M3 screw was tightened with a torque of 3 cN·m and crosslinked by heat in the same manner to obtain a structure equipped with an internal battery. Hereinafter, this structure equipped with an internal battery is referred to as comparative battery 1B-L.

[0080] A polymer solution was applied to the negative electrode sheet 1B, and then it was laminated with the positive electrode sheet 1B. Then, it was sandwiched between two laminate films so that the electrode terminals could be taken out, and further sandwiched between a glass plate and then between alloy tool steel, and an M3 screw was tightened with a torque of 3 cN·m and crosslinked by heat in the same manner to obtain a structure equipped with an internal battery. Hereinafter, this structure equipped with an internal battery is referred to as a comparative battery 1C-L.

[0081] In the same process as the comparative battery 1B-L, a small battery was fabricated with a negative electrode sheet of 13 mmφ and a positive electrode sheet of 1 cm 2 in diameter. This structure equipped with an internal battery is referred to as a comparative battery 1B-S.

[0082] In the same process as the comparative battery 1C-L, a small battery was fabricated with a negative electrode sheet of 13 mmφ and a positive electrode sheet of 1 cm 2 in diameter. This structure equipped with an internal battery is referred to as a comparative battery 1C-S.

[0083] A polymer solution was applied onto the negative electrode sheet 1C, and then a non-woven fabric (obtained by dissolving the paraffin of a medicine wrapping paper with hot acetone) cut out to 50 mm × 60 mm was placed on the polymer solution and impregnated, and then laminated with the positive electrode sheet 1C. Then, it was sandwiched between two laminate films so that the electrode terminals could be taken out, and further sandwiched between a glass plate and then between alloy tool steel, and an M3 screw was tightened with a torque of 3 cN·m and crosslinked by heat in the same manner to obtain a structure equipped with an internal battery. Hereinafter, this structure equipped with an internal battery is referred to as a comparative battery 1D-L.

[0084] For the fabricated comparative cells 1A-L, 1A-S, 1B-L, 1B-S, 1C-L, 1C-S, and 1D-L, with the structure equipped with an internal battery without removing the screws, the electrode terminals were connected to a battery charge / discharge device (manufactured by Hokuto Denko), and in an environment of 60 °C, HS-LIB-P-Co-003 was charged at a constant current of 0.1 C until it reached 4.2 V, and HS-LIB-P-NMC-001 was charged at a constant current of 0.1 C until it reached 4.3 V. Then, the current was controlled so that the voltage remained constant for 1 hour or more. Subsequently, it was discharged at a constant current of 0.1 C until it reached 3.0 V.

[0085] Among the comparative cells 1A-L, 1B-L, 1C-L, and 1D-L, a total of 17 cells were capable of charge and discharge, but only 1 cell of the comparative cell 1A-L was. Among the comparative cells 1A-S, 1B-S, and 1C-S, a total of 9 cells were capable of charge and discharge, and 2 cells were. For the comparative cell 1D-L, since it reached 4.3 V immediately after the start of charging, it was considered that lithium ions did not conduct at all.

[0086] When the polymer solution was impregnated by coating it on the non-woven fabric, but when crosslinked by heat in the same way, the solid polymer electrolyte leaked out of the non-woven fabric. From this, it is considered that in the comparative cell 1D-L, since the separator layer did not have a solid polymer electrolyte, it could not be charged. Also, since the solid polymer electrolyte, which is an organic polymer, has a very large molecular weight, it means that it is likely to leak out from small pores when crosslinked and solidified. That is, unless the layer of the solid polymer electrolyte is intentionally laminated on the positive electrode composite layer and the negative electrode composite layer, the solid polymer electrolyte between the separator and the active material will leak out due to the crosslinking of the polymer electrolyte, and as a result, the separator and the active material will adhere closely, suppressing the movement of lithium ions and making charge and discharge impossible.

[0087] In particular, when graphite is used as the negative electrode active material, the reduction potential is about 0.5 V (vs. Li / Li +Since it is extremely low, it is highly conceivable that metallic lithium is likely to be generated if a separator that inhibits the movement of lithium ions adheres to the surface of the graphite, and as a result, it is likely to short-circuit during charging. Such defects caused by the adhesion of the separator and the active material are considered to be more likely to occur as the electrode area increases.

[0088] Actually, from the cross-sectional SEM image (Figure 14) of the comparative battery 1A-L that could not be charged, it can be confirmed that the glass cloth, which is the separator 4a, is in close contact with the positive electrode active material 3 and the negative electrode active material 6.

[0089] Also, a 1 cm 2 circle made in the same process as the positive electrode sheet 1C and a 13 mmφ made in the same process as the negative electrode sheet 1A were bonded together with a polymer solution and then adhered by cross-linking with heat. Both of the two internal batteries showed normal charge and discharge characteristics.

[0090] <Comparative Example 2> An internal battery not pressurized during initial charging A portion of a commercially available positive electrode sheet (HS-LIB-P-NMC-001, Takizawa Co., Ltd.) where the positive electrode composite material was coated was cut out with a 1 cm 2 circle, impregnated with a polymer solution, and similarly cross-linked with heat to produce a positive electrode sheet 2A.

[0091] A portion of a commercially available negative electrode sheet (HS-LIB-N-Gr-001, Takizawa Co., Ltd.) where the negative electrode composite material was coated was cut out with a 1 cm 2 circle, impregnated with a polymer solution, and similarly cross-linked with heat to produce a negative electrode sheet 2A.

[0092] A portion of a commercially available positive electrode sheet (HS-LIB-P-NMC-001, Takizawa Co., Ltd.) where the positive electrode composite material was coated was cut out with a 1 cm 2 circle, and a positive electrode sheet 2B impregnated with a polymer electrolyte not containing a starting material was produced.

[0093] A portion of a commercially available negative electrode sheet (HS-LIB-N-Gr-001, Takizawa Co., Ltd.) where the negative electrode composite material was coated was cut out with a 1 cm 2A negative electrode sheet 2B was produced by cutting it out with a circle and impregnating it with a polymer electrolyte not containing a starting material.

[0094] A polymer solution was applied onto the negative electrode sheet 2A, and placed on a polymer solution coated with a glass cloth (fiber thickness: 5 μm, 24 g / m 2 , thickness: 20 μm) or alumina particles with a particle size of 2 μm and impregnated, and then laminated with the positive electrode sheet 2A. Thereafter, while taking out the electrodes of the positive and negative electrodes, it was vacuum-packed and cross-linked by heating in the same manner to obtain a structure provided with an internal battery. Hereinafter, the structure provided with this internal battery is referred to as a comparative battery 2A.

[0095] After laminating the positive electrode sheet 2B and the negative electrode sheet 2B via a solid polymer electrolyte sheet (thickness: about 50 μm) of about 20 mm × 20 mm, while taking out the electrodes of the positive and negative electrodes, it was vacuum-packed to obtain a structure provided with an internal battery. Hereinafter, the structure provided with this internal battery is referred to as a comparative battery 2B.

[0096] Regarding the produced comparative battery 2A and comparative battery 2B, the electrode terminals were connected to a battery charging and discharging device (manufactured by Hokuto Denko), charged at a constant current of 0.1 C until it reached 4.3 V in an environment of 60°C, and the current was controlled so that the voltage became constant for 1 hour or more as it was, but none of the total 14 sheets of the comparative battery 2A and comparative battery 2B could be charged and discharged. The vacuum packing swelled when charging was applied.

[0097] When using graphite for the negative electrode, it is known that a Solid Electrolyte Interphase (SEI) is formed by the reaction between the graphite surface and the electrolyte. Gas may be generated during the formation of the SEI, and it is considered necessary to apply pressure during the initial charging to maintain the adhesion state between the active material and the solid polymer electrolyte.

[0098] <Comparative Example 3> An internal battery without a separator After laminating the positive electrode sheet 2B and the negative electrode sheet 2B through a solid polymer electrolyte sheet (thickness: approximately 50 μm) of about 20 mm × 20 mm, sandwich them with two alloy tool steels, and tighten this alloy tool steel with an M6 screw at a torque of 3 cN·m so that the battery does not short-circuit. Hereinafter, the structure including this internal battery is referred to as a comparative battery 3. Two comparative batteries 3 were fabricated.

[0099] Next, without removing the M6 screw of this comparative battery 3, while keeping the structure including the internal battery, connect it to a battery charge / discharge device (manufactured by Hokuto Denko), charge it at a constant current of 0.1 C until it reaches 4.3 V in an environment of 60°C, and then control the current so that the voltage remains constant for 1 hour or more. Thereafter, discharge it at a constant current of 0.1 C until it reaches 3.0 V. Both of the two fabricated batteries showed normal charge and discharge. Subsequently, remove the M6 screw and take out the internal battery. When bent, both short-circuited. Since there is no separator, it was confirmed that short-circuiting occurs due to excessive bending.

[0100] <Comparative Example 4> Adhesion before crosslinking the polymer solution impregnated in the composite material layer Cut out a portion where the positive electrode composite of a commercially available positive electrode sheet (HS-LIB-P-NMC-001, Takizawa Co., Ltd.) is coated with dimensions of 37 mm × 47 mm, and a portion where the positive electrode composite is not coated and the aluminum foil is exposed with a width of 10 mm and a length of 15 mm as an electrode terminal. Thereafter, a positive electrode sheet 4A impregnated with a polymer solution was fabricated.

[0101] Next, cut out a portion where the negative electrode composite of a commercially available negative electrode sheet (HS-LIB-N-Gr-001, Takizawa Co., Ltd.) is coated with dimensions of 40 mm × 50 mm, and a portion where the negative electrode composite is not coated and the copper foil is exposed with a width of 10 mm and a length of 15 mm as an electrode terminal at a position different from that of the above positive electrode sheet. Thereafter, a negative electrode sheet 4A impregnated with a polymer solution in the negative electrode composite was fabricated.

[0102] Apply a polymer solution onto the negative electrode sheet 4A, and then a glass cloth cut out to 50 mm × 60 mm (fiber thickness: 5 μm, 24 g / m 2, placed on top of the polymer solution (thickness: 20 μm) and impregnated, and then laminated with the positive electrode sheet 4A, all six fabricated batteries short-circuited.

[0103] <Comparative Example 5> Solid Polymer Electrolyte with Low Ionic Conductivity Following the same steps as in Comparative Examples 1 to 4, 32 internal batteries were fabricated using a solid polymer electrolyte with an ionic conductivity of 5.0 × 10 -5 S / cm and a lithium ion transference number of 0.1 at room temperature (25°C). However, even under the conditions of 60°C and 0.01 C, the voltage immediately rose to over 4.2 V during the initial charge, and none of them could be charged and discharged. Considering the performance of the solid electrolyte, it is thought that the ionic conductivity required to charge and discharge a storage density of 1.5 mAh / cm 2 is insufficient.

Table 1

[0104] The results of Example 1, Example 2, and Comparative Examples 1 to 5 are shown in Table 1 above. By providing a layer of solid polymer electrolyte between the active material and the separator, not only high safety is achieved where it does not short-circuit even when bent, but also excellent effects such as being dramatically easier to manufacture even for a large area are obtained.

[0105] <Example 3> Electric Unit with Stacked Internal Batteries After stacking 18 internal batteries fabricated in Example 1 as shown in Figure 4, they were wrapped with aramid fibers so that the electrode terminals could be taken out, and an outer package was formed by impregnating with a flexible epoxy resin using VaRTM, thus fabricating a high-capacity all-solid-state battery.

[0106] Figure 15 shows the charge-discharge characteristics of the fabricated high-capacity all-solid-state battery evaluated at 60°C and 0.05 C. The discharge capacity is 440 mAh, and it also has a sufficient weight energy density of 100 Wh / kg including the outer package, which is sufficient performance for mounting on wearable devices.

Industrial Applicability

[0107] The flexible all-solid-state battery according to the present invention has sufficient performance to power various sensor devices. Among them, not only is it flexible, but it also has extremely high safety that does not short-circuit even when folded, cut, or struck, making it suitable for use as a wearable lithium-ion secondary battery from a battery that can be carried around by people.

Explanation of Symbols

[0108] 1: Internal battery of flexible all-solid-state battery, 1a: Internal battery of flexible all-solid-state battery, 2: Positive electrode current collector, 3: Positive electrode active material, 4: Separator, 4-1: Pore, 4-2: Opening, 4a: Separator, 4a-1: Pore, 4a-2: Opening, 5: Solid polymer electrolyte, 6: Negative electrode active material, 7: Negative electrode current collector, 8: Layer including positive electrode active material, 8-1: Positive electrode composite material layer, 9: Layer including negative electrode active material, 9-1: Negative electrode composite material layer, 10: Separator layer including solid polymer electrolyte, 11: Solid polymer electrolyte layer, 12: Positive electrode sheet, 13: Negative electrode sheet, 14: Polymer solution, 15: Polymer film, 16: Plate, 17: Outer package, 18: Flexible all-solid-state battery containing high-capacity internal battery, 19: Internal battery laminate, 20: High-capacity internal battery with electrode terminal positions reversed between positive and negative electrodes, 21: Electrical unit with high-capacity internal batteries laminated

Claims

1. A flexible all-solid-state battery comprising a layer of solid polymer electrolyte disposed between a separator layer holding a solid polymer electrolyte and a layer comprising a negative electrode active material.

2. The separator has a thickness in the range of 1 μm to 100 μm, 1 g / m 2 to 70 g / m 2 of a woven fabric, knitted fabric or non-woven fabric of inorganic fibers or polymer fibers, or an oxide ceramic particle layer containing oxide ceramic particles having a particle diameter of 1 μm to 20 μm at a filling rate in the range of 5% to 60%, or a composite of the woven fabric, knitted fabric or non-woven fabric and the oxide ceramic particles, The flexible all-solid-state battery according to claim 1, characterized in that it comprises.

3. The flexible all-solid-state battery according to claim 1, wherein the thickness of the layer of solid polymer electrolyte is in the range of 500 nm to 60 μm.

4. The flexible all-solid-state battery comprises a negative electrode sheet composed of a layer comprising the negative electrode active material and a negative electrode current collector in contact with the negative electrode active material. The negative electrode sheet has a capacity of 0.1 mAh / cm 2 to 7 mAh / cm 2 The flexible all-solid-state battery according to claim 1, characterized by having such a capacity.

5. The flexible all-solid-state battery further includes a positive electrode sheet having a capacity of 0.1 mAh / cm 2 to 7 mAh / cm 2 The flexible all-solid-state battery according to claim 1, characterized in that it further includes a positive electrode sheet having a capacity of 0.1 mAh / cm

6. The flexible all-solid-state battery according to claim 1, wherein the thickness of the layer of solid polymer electrolyte disposed between the layer in which the solid polymer electrolyte is held in the separator and the layer comprising a positive electrode active material is in the range of 500 nm to 60 μm.

7. The flexible all-solid-state battery has an electrode area larger than 1.77 cm 2 The flexible all-solid-state battery according to claim 1, characterized by having an electrode area larger than 2 .

8. The flexible all-solid-state battery according to any one of claims 1 to 7, wherein the flexible all-solid-state battery has a folded shape.

9. A polymer solution obtained by mixing a polymer electrolyte and an initiator is applied to a composite layer comprising an active material holding a solid polymer electrolyte, flat plates or films are laminated, and crosslinking is performed while applying a pressure in the range of 1 kPa to 500 kPa. A polymer solution is applied onto a positive electrode sheet or a negative electrode sheet, a separator is placed on the applied polymer solution to impregnate the polymer solution, and after laminating with the negative electrode sheet or the positive electrode sheet, it is sandwiched between flat plates or films, and crosslinking is performed while applying a pressure in the range of 1 kPa to 500 kPa. A method for manufacturing a flexible all-solid-state battery, characterized by manufacturing an all-solid-state battery having layers of solid polymer electrolyte on both sides of a separator holding a solid polymer electrolyte.

10. The method for manufacturing a flexible all-solid-state battery according to claim 9, characterized in that an all-solid-state battery having a layer of solid polymer electrolyte is sandwiched between flat plates or films, and initial charging is performed while applying a pressure of 1 kPa to 1 MPa.

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