Secondary battery

Abstract

To provide a secondary battery which can be reduced in size and has better input / output performance and capacity.SOLUTION: A secondary battery 1 includes a first electrode 10 that functions as a p-type semiconductor, a second electrode 20 that functions as an n-type semiconductor, and a dielectric layer 30 that is disposed between the first electrode 10 and the second electrode 20. In the dielectric layer 30, a compound having a perovskite structure is supported on Japanese paper. The secondary battery 1 includes a plurality of units 50 which each include the first electrode 10, the dielectric layer 30 and the second electrode 20. It is preferable that, in the units 50, the first electrode 10 in one unit 50 and the second electrode in the other unit 50 are laminated so as to be in direct contact with each other.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a secondary battery.

Background Art

[0002] Currently, lithium-ion secondary batteries are widely used. A typical lithium-ion secondary battery includes a positive electrode using a lithium-containing transition metal composite oxide as an active material, a negative electrode using a material capable of occluding and releasing lithium ions as an active material, a non-aqueous electrolyte, and a separator. However, since conventional lithium-ion secondary batteries are chemical batteries, there is a limit to miniaturization. Therefore, in recent years, various secondary batteries have been proposed as alternatives to lithium-ion secondary batteries.

[0003] For example, Patent Document 1 proposes a secondary battery including a first electrode that functions as a p-type semiconductor, a second electrode that functions as an n-type semiconductor, and a solid electrolyte provided between the first electrode and the second electrode.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Although the secondary battery described in Patent Document 1 is excellent in input / output performance and capacity and can be miniaturized, there is a demand for further improving the input / output performance and capacity.

[0006] Therefore, an object of the present invention is to provide a secondary battery that can be miniaturized and has more excellent input / output performance and capacity.

Means for Solving the Problems

[0007] The present invention relates to a first electrode that functions as a p-type semiconductor, a second electrode that functions as an n-type semiconductor, and a dielectric layer disposed between the first electrode and the second electrode, and provides a secondary battery in which the dielectric layer is formed by supporting a compound having a perovskite structure on Japanese paper.

Advantages of the Invention

[0008] According to the present invention, a secondary battery that can be miniaturized and has more excellent input / output performance and capacity is provided.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0010] The present invention will be described below based on its preferred embodiments with reference to the drawings. FIG. 1 schematically shows an embodiment of a secondary battery of the present invention. The secondary battery 1 shown in the figure includes a first electrode 10, a second electrode 20, and a dielectric layer 30 disposed between these electrodes. The secondary battery 1 further includes a first current collector 11 and a second current collector 22 made of a metal such as aluminum or copper. The first current collector 11 is disposed on the surface of the first electrode 10 that does not face the dielectric layer 30 among the two surfaces of the first electrode 10. The second current collector 22 is disposed on the surface of the second electrode 20 that does not face the dielectric layer 30 among the two surfaces of the second electrode 20. The first electrode 10 functions as a p-type semiconductor. On the other hand, the second electrode 20 functions as an n-type semiconductor. As described below, the first electrode 10 functions as a positive electrode. The second electrode 20 functions as a negative electrode.

[0011] In the secondary battery 1 of the embodiment shown in FIG. 1, the first electrode 10 and the dielectric layer 30 are in direct contact with each other, and no other layer is interposed between them. However, for the purpose of enhancing various performances of the secondary battery 1, it is not prohibited to interpose one or two or more other layers between the first electrode 10 and the dielectric layer 30. In the secondary battery 1 of the embodiment shown in FIG. 1, the second electrode 20 and the dielectric layer 30 are in direct contact with each other, and no other layer is interposed between them. However, for the purpose of enhancing various performances of the secondary battery 1, it is not prohibited to interpose one or two or more other layers between the second electrode 20 and the dielectric layer 30.

[0012] Unlike a conventional lithium-ion secondary battery, the secondary battery 1 of this embodiment including the first electrode 10 functioning as a p-type semiconductor, the second electrode 20 functioning as an n-type semiconductor, and the dielectric layer 30 achieves charge and discharge by the movement of holes and electrons instead of the movement of ions. Specifically, during charging, the high-potential terminal of an external power source (not shown) is electrically connected to the first electrode 10, and the low-potential terminal is electrically connected to the second electrode 20. As a result, holes present in the first electrode 10 move to the opposing surface of the dielectric layer 30 and its vicinity. At the same time, electrons present in the second electrode 20 move toward the opposing surface of the dielectric layer 30. Thus, both charges are respectively accumulated near both surfaces of the dielectric layer 30. On the other hand, during discharging, holes present in the first electrode 10 move toward the first current collector 11 side. At the same time, electrons present in the second electrode 20 move toward the second current collector 22 side and are further released to an external circuit (not shown), thereby causing an electric current to flow. Thus, it can be said that the secondary battery 1 of this embodiment is a battery that operates based on the principle of a semiconductor battery.

[0013] Since holes and electrons are smaller and lighter than ions, they have high mobility. That is, the secondary battery of the present invention operates by the movement of holes and electrons, which is faster than the movement of ions. Therefore, the secondary battery 1 of this embodiment has high input / output performance and high rapid charging performance. In addition, since the secondary battery 1 of this embodiment does not involve a chemical reaction during operation, it has high capacity, high output, and high safety.

[0014] Since the first electrode 10 functions as a p-type semiconductor as described above, it is preferably composed of a p-type semiconductor material. There is no particular limitation on the p-type semiconductor material, and those known so far can be used. For example, as the p-type semiconductor material, an impurity semiconductor material obtained by doping an intrinsic semiconductor material such as silicon, germanium, or selenium with a trivalent element such as boron, aluminum, and gallium, a compound semiconductor material composed of two or more elements, and an oxide semiconductor material can be used. These p-type semiconductor materials can be used alone or in combination of two or more.

[0015] Specific examples of the p-type semiconductor material include nickel oxide, manganese(IV) oxide, cobalt(II) oxide, iron oxide, copper oxide, cuprous oxide, cobalt(II,III) oxide, and rhodium oxide. When nickel oxide is used as the p-type semiconductor material, the nickel oxide may be doped with a doping element. Examples of such a doping element include antimony. Nickel oxide has low solubility and it is difficult to perform patterning by wet etching. Therefore, when forming the first electrode 10 made of nickel oxide by sputtering and performing patterning without using a metal mask, it is preferable to perform lithography and dry etching after film formation. As a result of the study by the present inventors, it has become clear that the number of holes per one metal atom in nickel oxide is the largest among general cathode materials such as manganese, cobalt, and iron. Therefore, it is particularly preferable that the first electrode contains nickel oxide.

[0016] The first electrode 10 can be formed by various thin film formation methods such as sputtering and chemical vapor deposition. Alternatively, the first electrode 10 can also be formed by applying a slurry containing particles of the p-type semiconductor material or by compression molding the particles of the p-type semiconductor material.

[0017] Since the second electrode 20 functions as an n-type semiconductor as described above, it is preferably configured to include an n-type semiconductor material. The second electrode 20 that functions as an n-type semiconductor can occlude and release ions, holes, and electrons generated in the first electrode 10 that functions as a p-type semiconductor. There is no particular limitation on the n-type semiconductor material, and those known heretofore can be used. For example, as the n-type semiconductor material, an impurity semiconductor material obtained by doping an intrinsic semiconductor material such as silicon, germanium, or selenium with a pentavalent element such as phosphorus, arsenic, and antimony, a compound semiconductor material composed of two or more elements, and an oxide semiconductor material can be used. These n-type semiconductor materials can be used alone or in combination of two or more.

[0018] Specific examples of the n-type semiconductor material include silicon, graphene, various natural graphites, artificial graphites, silicon-based composite materials (silicides), silicon oxide-based materials, titanium alloy-based materials, and various alloy composition materials. These substances can be used alone or in combination of two or more kinds. Particularly, when using graphene as the n-type semiconductor material, in the second electrode 20 during charging, the volume where charges can be accumulated increases, and the charges can be arranged orderly in the direction perpendicular to the electric field direction. As a result, the charges are less likely to leak and the charge accumulation amount increases. Thereby, there is an advantage that the capacity that can be stored electrically further increases.

[0019] When using silicon as the n-type semiconductor material, the silicon may be doped with phosphorus oxide, sulfur oxide, or arsenic. These dopings are performed, for example, using a high shear force disperser. Silicon functioning as an n-type semiconductor is less likely to generate heat. Therefore, the secondary battery 1 having silicon in the second electrode 20 has an advantage that it is less likely to generate heat even when an internal short circuit occurs in the secondary battery 1. Due to this, the safety and life of the secondary battery 1 are improved. In particular, since the second electrode 20 contains silicon, an electron accumulation layer can be provided on the second electrode 20.

[0020] Other elements other than the above-described elements may be doped into the n-type semiconductor material. For example, alkali metal elements such as lithium, sodium, and potassium, and transition metal elements such as copper, titanium, and zinc may be doped.

[0021] The second electrode 20 can be formed by various thin film formation methods such as sputtering, physical vapor deposition method, or chemical vapor deposition method. Alternatively, the second electrode 20 can also be formed by applying a slurry containing particles of the n-type semiconductor material or by compression molding the particles of the n-type semiconductor material.

[0022] The dielectric layer 30 is a layer formed by supporting a ferroelectric substance on a support. From the viewpoint of reducing the thickness of the dielectric layer 30 and decreasing the internal resistance of the secondary battery 1, it is preferable to use Japanese paper as the support. On the other hand, when using a support made of a material other than Japanese paper, it is difficult to sufficiently reduce the thickness of the dielectric layer 30 while maintaining the strength. Japanese paper is superior to other types of paper in that it has high strength even when its thickness is reduced. Examples of the material of Japanese paper include kozo, mitsumata, ganpi, hemp, sandalwood, sophora flavescens, and butterbur. These can be used alone or in combination of two or more. Among them, since it has high strength even when the thickness is reduced, it is preferable to use kozo as the material of Japanese paper. Japanese paper may be hand-made Japanese paper or machine-made Japanese paper. Examples of the hand-making method include flow casting and dipping.

[0023] From the viewpoint of enhancing the mechanical strength of the dielectric layer 30, the thickness of the Japanese paper is preferably 4.0 μm or more. Also, from the viewpoint of reducing the resistance of the dielectric layer, the thickness of the Japanese paper is preferably 11.8 μm or less, and more preferably 8.6 μm or less.

[0024] In this specification, "ferroelectric" refers to a substance having a relative permittivity of 1 or more and 30,000 or less. From the viewpoint of making the advantages of the dielectric layer 30 described later more prominent, the ferroelectric preferably has a relative permittivity of 40 or more and 1,000 or less, and more preferably 70 or more and 500 or less. As the ferroelectric supported on the support, a compound having a perovskite structure can be preferably used. A compound having a perovskite structure is advantageous in that it enables densification of the ferroelectric even without sintering.

[0025] In this embodiment, the dielectric layer 30 may be composed of a single layer including a sheet of Japanese paper carrying a ferroelectric, or may be composed of two or more layers including two or more sheets of Japanese paper carrying a ferroelectric. When the dielectric layer 30 includes two or more sheets of Japanese paper, the same ferroelectric may be carried on each sheet of Japanese paper, or different ferroelectrics may be carried on each sheet of Japanese paper. The ferroelectric may be carried on only one side of the Japanese paper, or may be carried on both sides of the Japanese paper. Further, the ferroelectric may be carried inside the Japanese paper.

[0026] The ferroelectric may be carried on one side of the support, or may be carried on both sides of the support. Further, the ferroelectric may be carried inside the support in the thickness direction of the support.

[0027] Specific examples of the compound having a perovskite structure to be carried on the support include lithium niobate, sodium potassium niobate, sodium niobate, bismuth ferrite, bismuth titanate, sodium bismuth titanate, and the like. Among them, since it can be used even at a high potential such as 10 V, it is preferable to use lithium niobate as the compound having a perovskite structure. Further, lithium niobate is also economically advantageous compared to other compounds having a perovskite structure.

[0028] By interposing the dielectric layer 30 between the first electrode 10 and the second electrode 20, holes can be transported between the first electrode 10 functioning as a p-type semiconductor and the second electrode 20 functioning as an n-type semiconductor. At the same time, physical contact between the first electrode 10 and the second electrode 20 is prevented. On the other hand, when an insulator such as silica or an organic polymer such as an epoxy resin is used as the dielectric layer 30, electrons in the second electrode 20 functioning as an n-type semiconductor cannot move to the insulator or the organic polymer and the secondary battery does not operate. Further, when an acrylic resin having a radical is used as the dielectric layer 30, the present inventor has confirmed that although initial characteristics can be obtained, deterioration of the secondary battery progresses due to an oxidation-reduction reaction and the life is short.

[0029] From the viewpoint of further enhancing the above advantages, the content of the ferroelectric in the dielectric layer 30 is preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 75% by mass or more. Also, from the viewpoint of reliably supporting the ferroelectric by the support and improving the structural stability of the dielectric layer 30, the content of the ferroelectric in the dielectric layer 30 is preferably 85% by mass or less, more preferably 80% by mass or less, still more preferably 75% by mass or less.

[0030] Examples of the method for supporting the ferroelectric on the support include a method of supporting it on the support by applying a slurry containing the ferroelectric or by compression molding the ferroelectric particles. Alternatively, the ferroelectric can also be supported on the support by various thin film formation methods such as sputtering and chemical vapor deposition. The support of the ferroelectric may be performed on one side of the support or on both sides of the support.

[0031] Conventional lithium ion secondary batteries are almost always formed by kneading and applying active materials, so there are limitations in thinning and miniaturizing the electrodes. As a result, there are also limitations in miniaturizing the battery. In contrast, the first electrode 10, the second electrode 20, and the dielectric layer 30 of the secondary battery 1 according to this embodiment can be formed by a thin film formation method such as sputtering or vapor deposition. In that case, a thinned and miniaturized secondary battery, for example, a small secondary battery with a size of 2 mm square, can be obtained. As a result, it becomes possible to form the secondary battery 1 into a small chip shape and arrange the thus formed secondary battery 1 on the electronic substrate of an electronic device. Also, it becomes possible to safely install the secondary battery 1 in a small space such as a heart pacemaker. Further, since the secondary battery 1 does not involve a chemical reaction during operation, the expansion and contraction of the battery that occur in conventional lithium ion secondary batteries do not occur, and it is possible to maintain a small chip shape.

[0032] In the secondary battery 1, it is preferable to adjust the volume and thickness of the first electrode 10, the dielectric layer 30, and the second electrode 20 so that the polarizing force of the dielectric layer 30 is below a certain level. When the polarizing force of the dielectric layer 30 is strong, in the first electrode 10, holes are likely to be polarized on the side opposite to the surface facing the dielectric layer 30. Also, in the second electrode 20, charges are likely to be polarized and biased on the side opposite to the surface facing the dielectric layer 30. As a result, there is a risk of a short circuit occurring at the portion where the first electrode 10 and the second electrode 20 are in contact. For the purpose of preventing this inconvenience, it is preferable to adjust the volume of the first electrode 10, the dielectric layer 30, and the second electrode 20. From this perspective, it is preferable that the volume of the first electrode 10 is larger than the volume of the second electrode 20 and the volume of the dielectric layer 30. In this case, when the volume of the first electrode 10 is V1, the volume of the dielectric layer 30 is V3, and the volume of the second electrode 20 is V2, the value of V1 / V2 is preferably 1.5 or more, more preferably 1.7 or more, and even more preferably 1.9 or more. Also, the value of V1 / V2 is preferably 4.0 or less, more preferably 3.0 or less, and even more preferably 2.1 or less. On the other hand, the value of V1 / V3 is preferably 1.0 or more, more preferably 2.0 or more, and even more preferably 3.3 or more. Also, the value of V1 / V3 is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.4 or less. As described above, among the first electrode 10, the dielectric layer 30, and the second electrode 20, it is preferable that the volume of the first electrode 10 is the largest. Regarding the volumes of the dielectric layer 30 and the second electrode 20, the dielectric layer 30 may be larger, the second electrode 20 may be larger, or they may be the same.

[0033] The volumes V1, V2, and V3 can be calculated, for example, when the shape of the Japanese paper, which is a support, is a rectangular parallelepiped, by measuring the area and thickness of the Japanese paper respectively and taking their product. At this time, the thickness of the Japanese paper is measured by the method described later.

[0034] As a result of the inventor's study, it has been found that by forming the first electrode 10 thicker, holes are less likely to be polarized on the side of the first electrode 10 opposite to the surface facing the dielectric layer 30. From this perspective, the thickness T1 of the first electrode 10 is preferably 20 μm or more, more preferably 40 μm or more, and still more preferably 60 μm or more. Also, the thickness T1 of the first electrode 10 is preferably 110 μm or less, more preferably 90 μm or less, and still more preferably 70 μm or less.

[0035] The thickness T2 of the second electrode 20 is preferably 5 μm or more, more preferably 20 μm or more, and still more preferably 30 μm or more. Also, the thickness T2 of the second electrode 20 is preferably 55 μm or less, more preferably 45 μm or less, and still more preferably 35 μm or less. The thickness T3 of the dielectric layer 30 is preferably 10 μm or more, more preferably 15 μm or more, and still more preferably 20 μm or more. Also, the thickness T3 of the dielectric layer 30 is preferably 100 μm or less, more preferably 50 μm or less, and still more preferably 30 μm or less. By setting the thickness T3 of the dielectric layer 30 within the above range, the strength of the dielectric layer 30 can be sufficiently increased while reducing the resistance of the dielectric layer 30.

[0036] For the measurement of the thicknesses T1, T2, and T3, for example, a constant-pressure thickness measuring instrument conforming to JIS K6250 is used. When measuring the thickness T3, the dielectric layer 30 is sandwiched between two glass plates to form a measurement sample, and the thickness of the measurement sample is measured with the above-mentioned constant-pressure thickness measuring instrument under a load of 500 Pa. Then, T3 is calculated by subtracting the thickness of the glass plate from the thickness of the measurement sample. When measuring the thickness T1 or T2, the same method as for measuring the thickness T3 is used, but as measurement samples, a measurement sample not including the layer to be measured (the first electrode 10 or the second electrode 20) and a measurement sample including the layer to be measured are used. Then, the difference in thickness between the two measurement samples is taken as the thickness T1 of the first electrode 10 or the thickness T2 of the second electrode 20. Also, as a method for more clearly measuring the thicknesses T1, T2, and T3, there is cross-sectional observation using a secondary electron image. In this measurement method, the vicinity of the center in the plan view of the secondary battery 1 is cut in the thickness direction with a cutter to obtain a measurement sample having a vertical and horizontal width of about 2 mm. An ion beam is irradiated onto the cut surface of the measurement sample using an IB-09010CP cross-sectional sample preparation apparatus (manufactured by JEOL Ltd.) to process the cut surface by about 0.5 mm. By observing the processed cut surface with a scanning electron microscope (manufactured by JEOL Ltd.), the thicknesses T1, T2, and T3 can be measured.

[0037] By disposing the secondary battery 1 of the present embodiment on, for example, an electronic substrate of an electronic device, it can function as a power source or an auxiliary power source of the electronic device. For example, by disposing the secondary battery 1 on an electronic substrate of a personal computer as an electronic device and functioning as an auxiliary power source, it becomes possible to retain the content of the volatile memory and mitigate the impact on electronic components when the power supply from the main power source is interrupted due to a power outage or the like. Also, even when the main power source is off, power can be supplied from the secondary battery 1 to the volatile memory to retain the content. In addition, the secondary battery 1 can be disposed on an electronic substrate of a pacemaker as an electronic device and function as a main power source. Since the secondary battery 1 does not involve a chemical reaction during operation, it has high safety. Therefore, it is suitable as the main power source of a pacemaker. Furthermore, the secondary battery 1 is also suitable as the main power source of a pacemaker in that it is a rechargeable secondary battery instead of a non-rechargeable primary battery used in conventional pacemakers.

[0038] The secondary battery 1 of this embodiment can also be arranged on an electronic substrate in a state of being accommodated in a housing 40 as shown in FIG. 2. The housing 40 can be formed of a conductive material such as copper, for example. The housing 40 can have a main body portion 41 and a lid portion 42. Both the main body portion 41 and the lid portion 42 can be formed of a conductive material. The main body portion 41 has an opening 41a and has an accommodation space S for the secondary battery 1 inside. The accommodation space S communicates with the outside of the main body portion 41 through the opening 41a. The lid portion 42 has a shape that can block the entire area of the opening 41a of the main body portion 41. In a state where the lid portion 42 closes the opening 41a, it is preferable that the lid portion 42 and the main body portion 41 are not electrically conductive. For this purpose, it is preferable to arrange an electrically insulating O-ring 43 on the peripheral edge 41b of the opening 41a and electrically insulate the lid portion 42 and the main body portion 41 by this O-ring 43.

[0039] In a state where the secondary battery 1 is arranged in the housing 40, as shown in FIG. 2, the first electrode 10 can be electrically connected to the lid portion 42 through a current-carrying member 44 such as a lead wire, a wire, or a conductive paste. On the other hand, the second electrode 20 can be electrically connected to various parts of the main body portion 41, for example, the bottom surface portion 41c. By electrically connecting the main body portion 41 and the lid portion 42 of the housing 40 to the circuit of the electronic substrate, the secondary battery 1 functions as a power source or an auxiliary power source of the electronic device. By accommodating the secondary battery 1 in the housing 40, deterioration of the secondary battery 1 due to the heat of the electronic device and leakage of electricity when the electronic device is submerged can be effectively prevented.

[0040] As one means for electrically connecting the second electrode 20 to the bottom surface portion 41c of the main body portion 41, a method using a metal mask can be mentioned. In this case, by using various thin film forming methods, the secondary battery 1 can be manufactured by laminating the second electrode 20, the dielectric layer 30, and the first electrode 10 in this order on the bottom surface portion 41c of the main body portion 41. Thereby, the bottom surface portion 41c of the main body portion 41 and the second electrode 20 are directly electrically connected. Instead of using a metal mask, the secondary battery 1 may be manufactured by a method of performing lithography and etching after film formation.

[0041] In the embodiment shown in FIG. 2, the first electrode 10 is electrically connected to the lid portion 42 of the housing 40. Instead, the first electrode 10 may be electrically connected to the side wall portion 41d of the main body portion 41. In this case, for the purpose of preventing a short circuit between the first electrode 10 and the second electrode 20, it is preferable to interpose an electrically insulating O-ring between the bottom surface portion 41c and the side wall portion 41d of the main body portion 41 to electrically insulate the bottom surface portion 41c and the side wall portion 41d. When the first electrode 10 is connected to the side wall portion 41d of the main body portion 41, it is not necessary to arrange an O-ring at the opening 41a of the main body portion 41 to electrically insulate the main body portion 41 and the lid portion 42.

[0042] Instead of using a conductive material for the housing 40, an electrically insulating material such as silica may be used. In this case, a through hole (not shown) may be provided at an arbitrary position of the housing 40, and a current-carrying member (not shown) electrically connected to the first electrode 10 and the second electrode 20 respectively may be drawn out of the housing 40 through the through hole.

[0043] When the secondary battery 1 is housed in the housing, the embodiment shown in FIG. 3 may be adopted instead of FIG. 2. In the embodiment shown in the figure, a secondary battery 1 in which the second electrode 20, the dielectric layer 30, and the first electrode 10 are laminated in this order is formed on a support member 45 made of an insulating material such as silica to manufacture a unit 46, and the unit 46 is housed in the housing 40. A through hole 45a is provided in the support member 45 in the unit 46, and a current-carrying member 44 is arranged in the through hole 45a. The current-carrying member 44 electrically connects the second electrode 20 and the bottom surface portion 41c of the main body portion 41.

[0044] In the embodiment shown in FIG. 3, a conductive material may also be used for the support member 45. In this case, it is not necessary to provide the through hole 45a and the current-carrying member 44.

[0045] FIG. 4 shows another embodiment of the secondary battery 1 of the present invention. The secondary battery 1 of the embodiment shown in the figure includes a coil 47 for wireless power supply, and power can be charged via the coil 47. Thereby, even when the secondary battery 1 is installed on the electronic substrate of the electronic device, the secondary battery 1 can be charged non - contact. In particular, when the secondary battery 1 is used as the main power source of the pacemaker, it is possible to charge the secondary battery 1 wirelessly from outside the body before the battery runs out. Therefore, the conventional battery replacement by surgery is not required, and the secondary battery 1 can be used semi - permanently. One end 47a of the coil 47 is electrically connected to the first electrode 10 via the lid portion 42. The other end 47b of the coil 47 is electrically connected to the second electrode 20 via the main body portion 41.

[0046] FIG. 5 shows another embodiment of the secondary battery of the present invention. The embodiment shown in the figure has a plurality of units 50 including a first electrode 10, a dielectric layer 30, and a second electrode 20. Specifically, the unit 50 consists of two sets, a first unit 50a and a second unit 50b. The plurality of units 50 are laminated such that the first electrode 10 in the first unit 50a and the second electrode 20 in the second unit 50b are in direct contact. As a result, the secondary battery 1 of the present embodiment is in a state where two sets of units 50a and 50b are connected in series. Therefore, in the secondary battery 1 of the present embodiment, the output voltage is doubled. Note that, if a current collector is disposed between the first electrode 10 in the first unit 50a and the second electrode 20 in the second unit 50b, the first unit 50a and the second unit 50b will not be diode - connected and will cause current leakage. Therefore, it is preferable that no current collector is disposed between the two units 50a and 50b.

[0047] In the first unit 50a, the dielectric connection portion 31 is disposed on the side of the first electrode 10, the second electrode 20, and the dielectric layer 30. On the other hand, in the second unit 50b, the dielectric connection portion 31 is disposed on the side of the second electrode 20 and the dielectric layer 30. The side surface of the first electrode 10 in the second unit 50b is exposed. An insulating layer 32 is disposed between the first electrode 10 in the first unit 50a and the second electrode 20 in the second unit 50b and the dielectric connection portion 31, respectively, so that these electrodes and the dielectric connection portion 31 are not electrically connected. As the dielectric connection portion 31, for example, similar to the dielectric layer 30, a ferroelectric carried on a support can be used. In this case, the ferroelectric and the support may be the same as those of the dielectric layer 30 or different ones. From the viewpoint of reducing the manufacturing cost of the secondary battery of the present invention, it is preferable that the dielectric layer 30 and the dielectric connection portion 31 are made of the same material. In addition, in FIG. 5, the dielectric layer 30 and the dielectric connection portion 31 are shown as different members, but the dielectric layer 30 and the dielectric connection portion 31 may be formed of an integrated single member. By arranging the dielectric layer 30 and the dielectric connection portion 31 integrally in this way, it is possible to effectively prevent the first electrode 10 and the second electrode 20 from contacting each other in one unit. Making the first electrode 10 and the second electrode 20 not contact each other in one unit has the advantage that charge can be stored as an independent unit.

[0048] As shown in FIG. 5, a second current collector 22 is disposed on the outer surface of the second electrode 20 in the first unit 50a. On the other hand, a first current collector 11 is disposed on the outer surface of the first electrode 10 in the second unit 50b. By connecting a load between the first current collector 11 and the second current collector 22, current can be taken out to the outside.

[0049] The embodiment shown in FIG. 6 is an embodiment in which the number of stacked layers of the unit 50 is 4 in the embodiment shown in FIG. 5. Hereinafter, unless otherwise specified, the above description of the embodiment shown in FIG. 5 is also applicable to the embodiment shown in FIG. 6. In the embodiment shown in FIG. 6, the first unit 50a, the second unit 50b, the third unit 50c, and the fourth unit 50d are stacked in this order. Specifically, the first electrode 10 in the first unit 50a and the second electrode 20 in the second unit 50b are stacked so as to be in direct contact. Similarly, the first electrode 10 in the second unit 50b and the second electrode 20 in the third unit 50c are stacked so as to be in direct contact, and the first electrode 10 in the third unit 50c and the second electrode 20 in the fourth unit 50d are stacked so as to be in direct contact. Therefore, in the secondary battery 1 of this embodiment, the output voltage is quadrupled.

[0050] A dielectric connection portion 31 is disposed on the side of each electrode except the first electrode 10 in the fourth unit 50d. In addition, an insulating layer 32 is disposed between each electrode except the second electrode 20 in the first unit 50a and the first electrode 10 in the fourth unit 50d and the dielectric connection portion 31 so that these electrodes and the dielectric connection portion 31 are not electrically connected.

[0051] Regarding points not particularly described in the embodiments shown in FIGS. 5 and 6, the descriptions of the embodiments shown in FIGS. 1 to 4 are appropriately applied. Also, in FIGS. 5 and 6, the same members as those in FIGS. 1 to 4 are denoted by the same reference numerals.

[0052] As described above, the present invention has been described based on its preferred embodiments, but the present invention is not limited to the above embodiments. For example, the secondary batteries shown in FIGS. 5 and 6 may be housed in the housing 40 shown in any of FIGS. 2 to 4.

Example

[0053] Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, “%” and “parts” mean “mass %” and “parts by mass”, respectively. In Reference Examples 1 to 3 described below, the materials of the supports were compared.

[0054] [Reference example 1] The support was made of washi paper A (Tengucho paper, pure kozo paper, white, ultra-thin, manufactured by Inoue Kamiten Co., Ltd.). The thickness of washi paper A was 4.1 μm. Lithium niobate manufactured by Johnson Matthey was used as the ferroelectric substance. First, lithium niobate powder and Kureha Corporation's PVDF#1320 (a solution in N-methylpyrrolidone (NMP) with a solid content of 12 parts) were mixed in a mass ratio of 94:6 to obtain a mixed solution. The mixed solution was dispersed to obtain a slurry, which was then applied to both sides of Japanese paper A. The paper was then dried in a vacuum desiccator at 120°C for 12 hours to impregnate the Japanese paper A with the ferroelectric material, thereby obtaining a dielectric layer. The thickness of the obtained dielectric layer was measured by the above-mentioned method and found to be 20 μm. The content of the ferroelectric material in the dielectric layer was 75 mass%. Next, a paint containing n-type silicon powder (manufactured by Kojundo Chemical Laboratory Co., Ltd.) doped with 16.7% by mass of graphene (manufactured by Strem Chemicals) was applied to one side of the dielectric layer, and then vacuum dried at 120°C for 12 hours to obtain a layer of the second electrode. The paint containing n-type silicon was prepared as follows. Nippon Paper Industries Co., Ltd.'s MAC-350HC (CMC powder) was added to pure water to a concentration of 1.4% and stirred. N-type silicon powder was added thereto. Zeon Corporation's binder BM-451B was further added and stirred. The mass ratio of n-type silicon powder, BM451B binder solid content, and CMC solid content was 92:4:4.

[0055] Next, a paint containing nickel oxide was applied to the other surface of the dielectric layer and vacuum dried at 120° C. for 12 hours to obtain a first electrode layer. The method for producing the paint containing nickel oxide was the same as the method for producing the paint used in producing the second electrode. The resistance of the battery thus obtained was 5.5 MΩ.

[0056] [Reference example 2] A dielectric layer and a battery were manufactured in the same manner as in Reference Example 1, except that Japanese paper B (Tengucho paper, pure kozo paper, white, very thin, manufactured by Inoue Kamiten Co., Ltd.) was used as the support instead of Japanese paper A. The thickness of Japanese paper B was 8.6 μm. The resulting dielectric layer had a thickness of 30 μm, the content of the ferroelectric material in the dielectric layer was 70 mass %, and the resistance value of the battery was 20 MΩ.

[0057] [Reference example 3] Except for using a nonwoven fabric (Bencotto PS-2 manufactured by Ozu Sangyo Co., Ltd.) as the support, a dielectric layer and a battery were produced in the same manner as in Reference Example 1. The thickness of the nonwoven fabric was 15.3 μm. The thickness of the obtained dielectric layer was 50 μm, the content of the ferroelectric material in the dielectric layer was 60 mass %, and the resistance value of the battery was unmeasurable due to its high resistance.

[0058] As described above, it is clear that the thickness of Japanese paper can be made smaller than that of nonwoven fabric, and therefore the use of Japanese paper as a support can reduce the resistance value of the battery.

[0059] Next, in Example 1 and Comparative Example 1 described below, a comparison was made between the secondary battery of the present invention and a conventional lithium ion secondary battery.

[0060] Comparative Example 1 A conventional lithium ion secondary battery was used as Comparative Example 1. Lithium nickel manganese cobalt oxide BC-618 manufactured by Sumitomo 3M Limited, PVDF#1320 manufactured by Kureha Corporation (12 parts solid content in N-methylpyrrolidone (NMP) solution), and acetylene black were mixed in a mass ratio of 3:1:0.09, and N-methylpyrrolidone (NMP) was further added and stirred with a twin-arm kneader to prepare a positive electrode material. The positive electrode material was applied to an aluminum foil having a thickness of 13.3 μm and dried, and then rolled to a total thickness of 155 μm, and then cut to a specific size to form a positive electrode.

[0061] Artificial graphite, styrene-butadiene copolymer rubber particle binder BM-400B (solid content 40 parts) manufactured by Nippon Zeon Co., Ltd., and carboxymethyl cellulose were mixed at a mass ratio of 100:2.5:1, and stirred with an appropriate amount of water using a two-arm kneader to prepare a negative electrode material. After applying the negative electrode material to a copper foil with a thickness of 10 μm and drying it, it was rolled to a total thickness of 180 μm, and then cut into a specific size to form a negative electrode.

[0062] A polypropylene microporous film with a thickness of 20 μm was used as a separator, and the film was sandwiched between the positive electrode and the negative electrode to obtain a laminate. This laminate was cut into a predetermined size and housed in an electrolytic cell can. An electrolytic solution in which 1 M of LiPF6 was dissolved in a mixed solvent of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate was injected into the electrolytic cell can in a dry air environment and left for a certain period. Then, after performing a preliminary charge at a current corresponding to 0.1C for about 20 minutes, it was sealed to fabricate a laminated lithium-ion secondary battery. Then, it was left to age at room temperature for a certain period.

[0063] 〔Example 1〕 Lithium niobate powder manufactured by Johnson Matthey and PVDF #1320 (N-methylpyrrolidone (NMP) solution with a solid content of 12 parts) manufactured by Kuraray Co., Ltd. were mixed at a mass ratio of 94:6. The mixed solution was dispersed to obtain a slurry. This slurry was impregnated into Japanese paper with a thickness of 4 μm (Tengu Shoten's Tenugui paper, pure kozo (paper mulberry) paper, white, ultra-ultra-thin) for 5 minutes. The Japanese paper impregnated with the slurry was vacuum dried at 120°C for 12 hours to obtain a dielectric layer. The content of the ferroelectric in the dielectric layer was 75% by mass. A paint containing n-type silicon powder (manufactured by High Purity Chemical Research Institute Co., Ltd.) doped with 16.7% by mass of graphene (manufactured by Sigma-Aldrich) was applied to one surface of the dielectric layer, and then vacuum dried at 120°C for 12 hours to obtain a layer of the second electrode. The preparation of the paint containing n-type silicon was carried out in the same manner as in Reference Example 1.

[0064] Next, a paint containing nickel oxide was applied to the other surface of the dielectric layer and vacuum dried at 120°C for 12 hours to obtain the first electrode layer. The paint containing nickel oxide was prepared in the same manner as in Reference Example 1. Ten of the thus obtained laminates were stacked to form a laminated laminate battery. The film formation volume ratio of n-type silicon: lithium niobate: nickel oxide was 5:3:10. The thickness of the first electrode was 60 μm, the thickness of the dielectric layer was 18 μm, and the thickness of the second electrode was 30 μm. Also, the volume of the first electrode was 0.324 cm 3 , the volume of the second electrode was 0.162 cm 3 , and the volume of the dielectric layer was 0.126 cm 3 . This battery was evaluated by the method shown below. The results are shown in Table 1 below.

[0065] 〔Initial battery capacity evaluation〕 The discharge capacity of the secondary battery of Example 1 was compared with the 1C discharge capacity in the specified potential range of 2V - 4.3V of Comparative Example 1, with the 1C discharge capacity of Comparative Example 1 set as 100. Also, the discharge capacity ratio of 100C / 1C was measured. Based on this, the high-power performance was evaluated. Similarly, the charge capacity ratio of 100C / 1C was measured. Based on this, the input performance and rapid charging performance were evaluated.

[0066] 〔Safety test〕 As the safety test, an overcharge test and a nail penetration test were conducted by the following methods.

[0067] 〔Overcharge test〕 A current was passed through the battery so that a charging rate of 200% was maintained, and it was determined whether or not there was a change in appearance after 15 minutes or more. The secondary battery that did not exhibit any abnormalities was evaluated as "OK", and the secondary battery that showed a change (such as swelling or rupture) was evaluated as "NG".

[0068] 〔Nail penetration test〕 For the fully charged secondary battery, the heat generation state and appearance were observed when a 2.7 mm diameter iron round nail was penetrated at a speed of 5 mm / second in a normal temperature environment. The secondary battery in which no change in temperature and appearance occurred was evaluated as "OK", and the secondary battery in which changes in temperature and appearance occurred was evaluated as "NG".

[0069]

Table 1

[0070] As shown in Table 1, it can be seen that the secondary battery of Example 1 does not generate heat even when rapidly charged at 100C, and can be charged in a short time of within 5 minutes. Since the resistance (z) of the battery is represented by the following formula (1), when the secondary battery has the structure of this example, the resistance decreases as the number of layers increases. Therefore, it can be seen that the performance of the battery can be obtained more than the capacity sum.

[0071]

Number

Explanation of symbols

[0072] 1 Secondary battery 10 First electrode 20 Second electrode 30 Dielectric layer

Claims

1. a first electrode that functions as a p-type semiconductor; a second electrode that functions as an n-type semiconductor; a dielectric layer disposed between the first electrode and the second electrode, and comprising: a secondary battery, wherein the dielectric layer is formed by supporting a compound having a perovskite structure on Japanese paper.

2. comprising a plurality of units each including the first electrode, the dielectric layer, and the second electrode; the secondary battery according to claim 1, wherein the plurality of units are stacked such that the first electrode in one unit is in direct contact with the second electrode in another unit.

3. the secondary battery according to claim 1, wherein the thickness of the dielectric layer is 10 μm or more and 100 μm or less.

4. the secondary battery according to claim 1, wherein the first electrode contains nickel oxide.

5. the secondary battery according to claim 1, wherein the second electrode contains silicon.

6. the secondary battery according to claim 1, wherein the volume of the first electrode is larger than the volume of the second electrode and the volume of the dielectric layer.

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