The present invention relates to a power supply device in which a plurality of battery cells is stacked, an electric vehicle that includes such a power supply device, and a power storage device.
A power supply device in which a large number of battery cells is stacked is suitable as a power supply that is mounted on an electric vehicle and supplies electric power to a motor that drives the vehicle, a power supply that is charged with natural energy such as a solar cell or late-night power, and a backup power supply for power failure. In the power supply device having this structure, the separator is interposed between the stacked battery cells. The separator insulates heat conduction between the battery cells and suppresses induction of thermal runaway of the battery cells. The thermal runaway of the battery cell occurs due to an internal short circuit caused by a short circuit between the positive electrode and the negative electrode inside, erroneous handling, or the like. Since a large amount of heat is generated when thermal runaway of the battery cell occurs, thermal runaway is induced in the adjacent battery cell when the heat insulating property of the separator is not sufficient. When thermal runaway of the battery cell is induced, the entire power supply device releases extremely large heat energy, and the safety as a device is impaired. In order to prevent this adverse effect, a power supply device in which a separator having excellent heat insulation characteristics is interposed between battery cells has been developed. (See PTL 1).
PTL 1: Unexamined Japanese Patent Publication No. 2018-204708
In a power supply device in which a large number of batteries are stacked with a separator interposed therebetween, it is also important to dispose respective battery cells stacked with the separator interposed therebetween at a fixed position to prevent positional misalignment, in addition to insulating the battery cells with the separator. In the power supply device, expansion and contraction, and vibration and impact of the battery cell also cause positional misalignment. The relative positional misalignment of the battery cells in the use state causes damage to the connection part of the metal sheet fixed to the electrode terminal of the adjacent battery cell with the bus bar, damage to the bus bar itself, or adverse effects such as malfunction due to vibration.
In order to prevent positional misalignment of the battery cells, the power supply device fixes the stacked battery cells in a compressed state. In this power supply device, a pair of end plates is disposed on opposing end faces of a battery block in which a large number of battery cells is stacked, and the pair of end plates is fixed by the binding bar. The binding bar and the end plate hold the battery cell in a compressed state with considerably strong pressure to prevent malfunction due to relative movement and vibration of the battery cell. In this power supply device, for example, in a device in which an area of a separator interposed between battery cells is about 100 square centimeters, an end plate is pressed with a strong force of several tons and fixed by a binding bar. In the power supply device having this structure, when the internal pressure increases and the battery cell expands, the end plate is pressed to increase the internal stress of the binding bar and the end plate. Since the binding bar is fixed to the end plate in a state where a strong tensile force acts and fixes the battery cell in a compressed state, when the battery cell expands due to an increase in internal pressure, a stronger tensile force acts. When the binding bar extends in this state, the battery cells are misaligned, so that it is necessary to use a tough metal sheet or the like that withstands extremely strong tensile force for the binding bar, and the binding bar becomes thick and heavy.
The above adverse effects can be suppressed by using an elastic separator that absorbs expansion of the battery cell. However, in this power supply device, an increase in tensile force of the binding bar due to expansion of the battery cell can be suppressed, but damage due to fatigue of the battery cell over time increases. The battery cells are severely damaged in a region of the sealing plate that airtightly closes the opening of the battery case.
The present invention has been developed for the purpose of further solving the above disadvantages, and an object of the present invention is to provide a technique capable of preventing damage to an opening of a battery cell by absorbing expansion of the battery cell with a separator.
A power supply device according to an aspect of the present invention includes battery block 10 in which a plurality of battery cells 1 is stacked in a thickness direction with separator 2 interposed therebetween, a pair of end plates 3 disposed on opposing end faces of battery block 10, and binding bar 4 coupled to the pair of end plates 3 and fixing battery block 10 in a compressed state via end plates 3. In battery cell 1, sealing plate 12 is airtightly fixed to an opening edge of battery case 11 whose bottom is closed. Separator 2 has stack plane 2A stacked on facing plane 11A of battery case 11 in a surface contact state. Stack plane 2A has elasticity that absorbs expansion due to an increase in internal pressure of battery cell 1, and the Young's modulus of an outer peripheral edge part and upper edge part 2a of stack plane 2A is different from the Young's modulus of an internal region 2b located inside the outer peripheral edge part, and the Young's modulus of upper edge part 2a is made higher than that of internal region 2b.
In the present specification, the “upper edge part” of the separator is specified in the drawings. In the power supply device illustrated in
An electric vehicle according to an aspect of the present invention includes power supply device 100 described above, traction motor 93 that receives electric power from power supply device 100, vehicle body 91 that incorporates power supply device 100 and motor 93, and wheel 97 that is driven by motor 93 to let vehicle body 91 travel.
A power storage device according to an aspect of the present invention includes power supply device 100 described above and power supply controller 88 configured to control charging and discharging of power supply device 100. Power supply controller 88 enables charging of secondary battery cells 1 with electric power supplied from an outside and causes secondary battery cells 1 to charge.
The power supply device described above can effectively prevent the damage of the opening of the battery cell while absorbing the expansion of the battery cell by the separator.
Hereinafter, the present invention will be described in detail with reference to the drawings. In the following description, terms (for example, “top”, “bottom”, and other terms including those terms) indicating specific directions or positions are used as necessary. However, the use of those terms is for facilitating the understanding of the invention with reference to the drawings, and the technical scope of the present invention is not limited by the meanings of the terms. Parts denoted by the same reference numerals in a plurality of drawings indicate the identical or equivalent parts or members.
Further, the following exemplary embodiment illustrates specific examples of the technical concept of the present invention, and does not limit the present invention to the following exemplary embodiment. In addition, unless otherwise specified, dimensions, materials, shapes, relative arrangements, and the like of the components described below are not intended to limit the scope of the present invention, but are intended to be illustrative. The contents described in one exemplary embodiment and one example are also applicable to other exemplary embodiments and examples. In addition, sizes, positional relationships, and the like of members illustrated in the drawings may be exaggerated for the sake of clarity of description.
A power supply device according to the first exemplary embodiment of the present invention includes a battery block in which a plurality of battery cells is stacked in a thickness with a separator interposed therebetween, a pair of end plates disposed on opposing end faces of the battery block, and a binding bar coupled to the pair of end plates and fixing the battery block in a compressed state via the end plates. In the battery cell, a sealing plate is airtightly fixed to an opening edge of a battery case whose bottom is closed. The separator has elasticity that absorbs expansion due to an increase in internal pressure of the battery cell when a stack plane stacked on a facing plane of the battery case in a surface contact state is deformed, and the Young's modulus of an outer peripheral edge part and an upper edge part of the stack plane is different from the Young's modulus of an internal region located inside the outer peripheral edge part, and the Young's modulus of the upper edge part is made higher than that of the internal region.
In the power supply device described above, the Young's modulus of the outer peripheral edge part of the stack plane of the separator and the upper edge part along the outer peripheral edge of the sealing plate of the battery cell is increased to have high rigidity, and the Young's modulus of the internal region of the stack plane is made smaller than the Young's modulus of the upper edge part to have low rigidity. Therefore, in a state where the internal pressure of the battery cell rises and expands, the expansion of the internal region of the stack plane is absorbed by thinly deforming the low-rigidity separator while suppressing the deformation of the upper edge part. The upper edge part of the stack plane of the separator is located in a region along the outer peripheral edge of the sealing plate of the battery cell. In the battery cell, a sealing plate is airtightly fixed to a cylindrical opening whose bottom is closed by a method such as laser welding. In the battery cell having this structure, when part of an opening edge, of a cylindrical battery case, where a sealing plate is fixed is deformed due to an increase in internal pressure, fatigue increases and a failure occurs. Since the internal region of the stack plane can absorb deformation even if the central part of the battery cell is curved so as to protrude, even if the internal pressure of the battery cell is increased and deformed in an expanded state, damage of fatigue is extremely small. Therefore, the power supply device described above has a feature in which the separator can efficiently absorb expansion of the battery cell due to an increase in internal pressure, and damage due to fatigue of the upper edge part of the battery cell can be prevented.
Further, in addition to the above feature, in the power supply device, since the expansion of the battery cell is absorbed by the separator, it is possible to suppress an increase in a stress acting on the end plate and the binding bar in a state where the internal pressure increases and the battery cell expands, and to reduce the maximum stress. This is effective in reducing the thickness and weight of the end plate and the binding bar. In addition, in the power supply device described above, since the expansion of the battery cell is absorbed by the separator, it is also possible to suppress the deviation of the relative positions of respective battery cells in a state where the internal pressure of the battery cell increases and the battery cell expands. The relative positional misalignment between the adjacent battery cells causes damage to the bus bar of the metal sheet fixed to the electrode terminal of the battery cell and the electrode terminal. The power supply device capable of preventing the relative positional misalignment of a battery cell whose separator expands due to an increase in internal pressure can prevent failure of a connection part between an electrode terminal and a bus bar due to expansion of the battery cell.
Furthermore, in the power supply device described above, since the Young's modulus of the upper edge part is increased and the Young's modulus of the internal region is decreased without making the entire surface of the separator have the same Young's modulus, even if the battery cell expands in the internal region of the stack plane, the pressure rise between the battery cell and the separator is suppressed. In the battery block in which the battery cells are stacked, the pressing force acting on the entire surface of the stack plane acts on the end plate. In a power supply device capable of reducing the pressure in the internal region of the stack plane in a state where the battery cells expand, the maximum stress acting on the end plate and the bus bar can be reduced by reducing the pressing force by which the battery block presses the end plate in a state where the battery cells increase in internal pressure and expand. Further, it has a feature in which the pressing force on the entire surface on which the battery cell stresses the separator is reduced, and the battery cell can be suppressed from being misaligned due to an increase in the pressing force.
In the power supply device according to the second exemplary embodiment of the present invention, the separator is made of a hybrid material of an inorganic powder and a fibrous reinforcing material. In the power supply device according to the third exemplary embodiment of the present invention, the inorganic powder is a silica aerogel.
The separator described above is interposed between adjacent battery cells to insulate heat in the adjacent battery cells. The hybrid material suppresses induction of thermal runaway due to heating of adjacent battery cells by battery cells that have generated heat to a high temperature due to thermal runaway. Furthermore, the separator also functions as an insulating sheet that insulates the stacked battery cells.
In the power supply device according to the fourth exemplary embodiment of the present invention, the separator is made of one hybrid material. In the power supply device according to the fifth exemplary embodiment of the present invention, the packing density of the silica aerogel in the upper edge part of the hybrid material is higher than that in the internal region.
In the power supply device according to the sixth exemplary embodiment of the present invention, the separator includes a high rigidity sheet and a low rigidity sheet having a Young's modulus smaller than that of the high rigidity sheet, both the high rigidity sheet and the low rigidity sheet are made of a hybrid material of a silica aerogel and a fibrous reinforcing material, the high rigidity sheet is disposed at an upper edge part, and the low rigidity sheet is disposed in an internal region.
In the power supply device of the seventh exemplary embodiment of the present invention, the packing density of the silica aerogel of the high rigidity sheet is higher than that of the low rigidity sheet.
In a power supply device according to the eighth exemplary embodiment of the present invention, the low rigidity sheet is a laminated sheet of a hybrid material and an elastic sheet. In the power supply device according to the ninth exemplary embodiment of the present invention, the elastic sheet is a rubber elastic sheet. Furthermore, in a power supply device according to the tenth exemplary embodiment of the present invention, the rubber elastic sheet is a synthetic rubber sheet.
In the power supply device according to the eleventh exemplary embodiment of the present invention, the separator has a thickness between 0.5 mm and 3 mm, inclusive.
Hereinafter, a more specific power supply device will be described in detail.
Power supply device 100 illustrated in a perspective view of
As illustrated in
Battery cell 1 is a lithium ion secondary battery. Power supply device 100 in which battery cell 1 is a lithium ion secondary battery has an advantage that the charge capacity with respect to the capacity and weight can be increased. However, battery cell 1 may be any other chargeable battery such as a non-aqueous electrolyte secondary battery other than the lithium ion secondary battery.
End plate 3 is a metal sheet that has an outer shape substantially equal to the outer shape of battery cell 1, and that is not deformed by being pressed by battery block 10, and is coupled to binding bar 4 at both side edges. End plates 3 couples stacked battery cells 1 in a compressed state, and binding bar 4 fixes battery block 10 in the compressed state at a predetermined pressure.
Separator 2 is interposed between stacked battery cells 1, and stacked on facing plane 11A of battery case 11 in a surface contact state, absorbs expansion of battery cells 1 due to an increase in internal pressure, further insulates adjacent battery cells 1, and further insulates heat conduction between battery cells 1. In battery block 10, a bus bar (not shown) of a metal sheet is fixed to electrode terminals 13 of adjacent battery cells 1, and battery cells 1 are connected in series or in parallel. In battery cells 1 connected in series, since a potential difference is generated in battery case 11, battery cells 1 are insulated and stacked by separator 2. Battery cells 1 connected in parallel are stacked while thermally insulated by separator 2 in order to prevent induction of thermal runaway although no potential difference is generated in battery case 11.
The entire separator 2 is made of hybrid material 20 of an inorganic powder and a fibrous reinforcing material, or an elastic sheet is stacked on hybrid material 20. The inorganic powder is preferably a silica aerogel. In hybrid material 20, fine gaps of fibers are filled with fine silica aerogel having low thermal conductivity. The silica aerogel is carried and disposed in the gaps of the fibrous reinforcing material. The hybrid material 20 includes a fiber sheet of a fibrous reinforcing material and a silica aerogel having a nanosized porous structure, and is manufactured by impregnating fibers with a gel raw material of the silica aerogel. A fiber sheet is impregnated with a silica aerogel, then fibers are stacked, a gel raw material is reacted to form a wet gel, and the surface of the wet gel is hydrophobized and dried with hot air to produce the material. The fiber of the fiber sheet is polyethylene terephthalate (PET). However, as the fiber of the fiber sheet, inorganic fibers such as flame-retardant oxidized acrylic fibers and glass wool can also be used.
The fibrous reinforcing material preferably has a fiber diameter of 0.1 to 30 μm inclusive. The fibrous reinforcing material can improve the heat insulation characteristics of hybrid material 20 by making the fiber diameter thinner than 30 μm and reducing the heat conduction by the fiber. Silica aerogel is inorganic fine particles composed of 90% to 98% of air, and has fine pores between skeletons formed by clusters in which nano-order spherical bodies are bonded, and has a three-dimensional fine porous structure.
The hybrid material 20 of a silica aerogel and a fibrous reinforcing material is thin and exhibits excellent heat insulation characteristics. Separator 2 made of hybrid material 20 is set to have a thickness that can prevent induction of thermal runaway of battery cell 1 in consideration of energy generated by thermal runaway of battery cell 1. The energy generated by the thermal runaway of battery cell 1 increases as the charge capacity of battery cell 1 increases. Therefore, the thickness of separator 2 is set to have an optimum value in consideration of the charge capacity of battery cell 1. For example, in a power supply device including a lithium ion secondary battery having a charge capacity of 5 Ah to 20 Ah inclusive as battery cell 1, hybrid material 20 has a thickness of 0.5 mm to 3 mm, optimally about 1 mm to 2.5 mm inclusive. However, the present invention does not specify the thickness of hybrid material 20 within the above range, and the thickness of hybrid material 20 is set to an optimum value in consideration of the heat insulation characteristics of thermal runaway including the fiber sheet and the silica aerogel and the heat insulation characteristics required for preventing induction of thermal runaway of the battery cell.
The hybrid material 20 of separator 2 is a sheet that is pressed against battery cell 1 expanding due to an increase in internal pressure and is thinly deformed. Separator 2 is thinned by the pressurizing force of expanding battery cell 1, and in the state where expanded battery cell 1 is restored to the original state, the state where separator 2 is crushed is restored to the original state to absorb the expansion and contraction of battery cell 1.
The separator 2 made of one hybrid material 20 is not a hybrid material having elasticity in which the entire surface is uniformly deformed. Separator 2 of hybrid material 20 has a Young's modulus different between upper edge part 2a interposed between openings of battery cases 11 of adjacent battery cells 1 and internal region 2b of stack plane 2A of battery cells 1. The Young's modulus of upper edge part 2a along sealing plate 12 is set higher than that of internal region 2b of stack plane 2A in order to suppress deformation of the upper edge part of battery cell 1. In separator 2, upper edge part 2a has rigidity higher than that of internal region 2b, and suppresses deformation of upper edge part 2a to be smaller than that of internal region 2b in a state where battery cell 1 expands due to an increase in internal pressure.
The perspective view of
The high rigidity sheet 21 has a Young's modulus higher than that of low rigidity sheet 22 so that deformation of upper edge part 2a can be suppressed in a state where it is pressurized by battery cell 1 whose internal pressure increases, and the Young's modulus of high rigidity sheet 21 is, for example, 1.5 times or more, preferably 2 times or more of that of low rigidity sheet 22.
In separator 2, in order to make the region provided with through hole 23 a low rigidity region having a small Young's modulus, through hole 23 is provided in a region excluding the outer peripheral edge part of separator 2. Since low rigidity sheet 22 is disposed in through hole 23 provided in the region excluding the outer peripheral edge part, the region excluding the outer peripheral edge part of separator 2 is a low rigidity region having a small Young's modulus. In separator 2 of
In separator 2 of
Since in separator 2 in which through hole 23 is provided in high rigidity sheet 21 and low rigidity sheet 22 is disposed in the through hole, high rigidity sheet 21 and low rigidity sheet 22 can be separately manufactured, there is a feature in which a large amount of high rigidity sheet 21 and low rigidity sheet 22 can be efficiently produced while significantly changing the Young's moduli of high rigidity sheet 21 and low rigidity sheet 22.
Since in separator 2 which is hybrid material 20 of a silica aerogel and a fibrous reinforcing material, the Young's modulus can be adjusted by, for example, the packing density of the silica aerogel, high rigidity sheet 21 can have a higher packing density of the silica aerogel than low rigidity sheet 22 to have a higher Young's modulus.
In separator 2 described above, low rigidity sheet 22 is disposed in through hole 23 of high rigidity sheet 21, so that upper edge part 2a has high rigidity and internal region 2b has low rigidity. However, as illustrated in
In separator 2 illustrated in the sectional view of
In power supply device 100, in order to miniaturize battery block 10 and increase a charge capacity, it is important to thin separator 2 to prevent induction of thermal runaway of battery cell 1. For this reason, elastic sheet 24 laminated on high rigidity sheet 21 has a thickness, for example, between 0.1 mm and 1 mm, inclusive, more preferably between 0.2 mm and 0.5 mm, inclusive, to absorb the expansion of internal region 2b of battery cell 1. The rubber elastic sheet 24A preferably absorbs the expansion of internal region 2b of battery cell 1 and reduces the compressive stress while being thinner than hybrid material 20.
In separator 2 illustrated in the perspective view of
Furthermore, similarly to separator 2 illustrated in the perspective view of
In separator 2 illustrated in
Further, in separator 2 illustrated in the perspective view of
In separator 2 illustrated in
Separator 2 having the structure described above also has a structure in which internal region 2b has low rigidity so as to be capable of absorbing deformation due to expansion of the opposed battery cells, and upper edge part 2a has high rigidity so as to suppress deformation of the upper edge part of the battery cells.
The elastic sheet 24 is a non-foamed rubber elastic body, foamed rubber, or thermoplastic elastomer. In elastic sheet 24, the rubber compressed in the laminated region is pushed out to the non-laminated region due to the incompressibility in which the volume hardly changes by being compressed, and the change in shape and pressure is alleviated at the boundary part between the laminated region and the non-laminated region. As elastic sheet 24, a synthetic rubber sheet is suitable. As the synthetic rubber sheet, any of isoprene rubber, styrene butadiene rubber, butadiene rubber, chloroprene rubber, nitrile rubber, polyisobutylene rubber, ethylene propylene rubber, ethylene vinyl acetate copolymer rubber, chlorosulfonated polyethylene rubber, acrylic rubber, fluororubber, epichlorohydrin rubber, urethane rubber, silicone rubber, thermoplastic olefin rubber, ethylene propylene diene rubber, butyl rubber, and polyether rubber can be used singly or in a laminate of a plurality of synthetic rubber sheets. In particular, the ethylene propylene rubber, the ethylene vinyl acetate copolymer rubber, the chlorosulfonated polyethylene rubber, the acrylic rubber, the fluororubber, and the silicone rubber have excellent heat insulation characteristics, and thus it is possible to realize higher safety by lengthening the time until thermal runaway and thermal melting. When rubber elastic sheet 6 is made of urethane rubber, it is particularly preferable to use thermoplastic polyurethane rubber or foamed polyurethane rubber.
Furthermore, as the thermoplastic elastomer, a thermoplastic polyester, a thermoplastic polyether, and the like are suitable.
In separator 2 of
In the separator, instead of the rubber elastic sheet, a high-rigidity frame-shaped rubber elastic sheet having a high Young's modulus can be laminated on the outer peripheral edge part, and a rubber elastic sheet having a low Young's modulus can be laminated on the inner side of the frame-shaped rubber elastic sheet. Here, polypropylene, polycarbonate, polybutylene terephthalate, or the like can also be used as a resin having a high Young's modulus in addition to the high-rigidity frame-shaped elastic sheet having a high Young's modulus. The high rigidity rubber elastic sheet has a higher Young's modulus than the low rigidity rubber elastic sheet, and suppresses deformation of the upper edge part of the battery cell. As the frame-shaped rubber elastic sheet, a sheet having a high Young's modulus that hardly deforms when the internal pressure of the battery cell increases is preferably used.
When a separator is formed by combining an elastic sheet having high rigidity and an elastic sheet having low rigidity, there is a method of bonding the sheets using an adhesive, a tape, or the like, or a method of combining two sheets by two-color molding.
The separator is stacked at a fixed position of the battery cell with an adhesive layer or a bonding layer interposed therebetween. Separator 2 can also be disposed at a fixed position of a battery holder (not shown) in which battery cells 1 are disposed at fixed positions in a fitting structure.
In power supply device 100 described above, a prismatic battery cell having a charge capacity of 6 Ah to 80 Ah inclusive of battery cell 1 is used, and hybrid material 20 of separator 2 is “NASBIS (registered trademark) manufactured by Panasonic Corporation” which is a hybrid material of a silica aerogel and a fibrous reinforcing material, so that specific battery cell 1 can be forcibly caused to perform thermal runaway to prevent induction of thermal runaway to adjacent battery cell 1.
The power supply device described above can be used as an automotive power supply that supplies electric power to a motor used to drive an electric vehicle. An electric vehicle incorporating the power supply device may be an electric vehicle such as a hybrid car or a plug-in hybrid car that is driven by an engine and a motor, or an electric car that is driven only by a motor. The power supply device can be used as a power supply for any of these vehicles. Power supply device 100 having high capacity and high output to acquire electric power for driving the vehicle will be described below, for example. Power supply device 100 includes a large number of the above-described power supply devices connected in series or parallel, as well as a necessary controlling circuit.
Further,
In the present invention, the application of the power supply device is not limited to a power supply to a motor that allows a vehicle to travel. The power supply device according to the exemplary embodiment can be used as a power supply for a power storage device that stores electricity by charging a battery with electric power generated by photovoltaic power generation, wind power generation, or other methods.
The power storage device illustrated in
Further, although no illustration is given, the power supply device can be used as a power supply for a power storage device that stores electricity by charging a battery using late-night power at nighttime. The power supply device charged by late-night power can be charged with late-night power, which is surplus power at power plants, and output electric power during the daytime, when the electric power load is high, to restrict peak power consumption at a low level in the daytime. The power supply device can also be used as a power supply that is charged with both output power of a solar cell and late-night power. This power supply device can effectively utilize both electric power generated by a solar cell and late-night power, and can efficiently store power in consideration of weather and power consumption.
The power storage device described above can be suitably used for the following applications: a backup power supply device mountable in a rack of a computer server; a backup power supply device used for radio base stations of cellular phones; a power supply for storage used at home or in a factory; a power storage device combined with a solar cell, such as a power supply for street lights; and a backup power supply for traffic lights or traffic displays for roads.
The power supply device according to the present invention is suitably used as a large current power supply used for a power supply of a motor for driving an electric vehicle such as a hybrid car, a fuel cell car, an electric car, or an electric motorcycle. Examples of such a power supply device include power supply devices for a plug-in hybrid electric car that can switch between the EV drive mode and the HEV drive mode, a hybrid electric car, an electric car, and the like. The power supply device can also be appropriately used for the following applications: a backup power supply device mountable in a rack of a computer server; a backup power supply device used for radio base stations of cellular phones; a power supply for storage used at home or in a factory; a power storage device combined with a solar cell, such as a power supply for street lights; and a backup power supply for traffic lights.
Number | Date | Country | Kind |
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2019-122218 | Jun 2019 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2020/016992 | 4/20/2020 | WO | 00 |