Battery system

Abstract

To provide a battery system that can apply a uniform pressure to a battery cell and can be miniaturized even when a thickness of the battery cell changes greatly due to charge and discharge.SOLUTION: A battery system includes: a cell stacked body in which a plurality of battery cells are stacked; a pair of end plates disposed at both ends in a stacking direction of the cell stacked body; a gas cushion disposed at least one of between the battery cells and between the battery cells and the end plates; a pipe having a compressor and a relief valve; a pipe connecting the pipe and the gas cushion; and a cushion controller. The gas cushion may be an elastic container filled with gas, and the cushion controller may operate the compressor to introduce the gas into the pipe when a pressure of the gas cushion is less than a preset value, and may open the relief valve to exhaust the gas in the pipe when the pressure of the gas cushion exceeds the preset value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a battery system. [Background technology]

[0002] In recent years, research and development into battery systems that contribute to energy efficiency has been conducted to ensure that more people have access to affordable, reliable, sustainable, and advanced energy. A battery system is a modular combination of multiple battery cells, and generally includes a cell stack in which multiple battery cells are stacked, and a pair of end plates located on both ends of the cell stack in the stacking direction. Battery systems are used in applications requiring high current and high voltage, such as motor drive for electric vehicles and hybrid electric vehicles.

[0003] In battery systems, studies have been conducted to apply pressure in the stacking direction of the battery cells by placing cushioning materials between battery cells or between the cell stack and the end plate.Known cushioning materials include a cushioning material having a deformable chamber and a system that supplies a fluid that deforms the chamber (Patent Document 1), and elastic springs such as leaf springs and liquid springs (Patent Documents 2 and 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-64848 [Patent Document 2] Patent Publication No. 2021-96974 [Patent Document 3] European Patent Application Publication No. 3886202 Summary of the Invention [Problem to be solved by the invention]

[0005] Increasing electrical capacity and miniaturization are key challenges in battery system technology. To improve the electrical capacity of a battery system, it is effective to apply uniform pressure to each battery cell incorporated in the battery system via a cushioning material. Fluid cushions, which are filled with fluid, have high internal pressure uniformity, allowing for highly uniform pressure to be applied to the entire battery cell. Meanwhile, lithium metal batteries, which use lithium ions as a charge transfer medium for battery cells, are being considered. During charging, lithium metal is deposited in the negative electrode layer, and during discharging, the lithium metal migrates as lithium ions to the positive electrode layer. These lithium metal batteries experience significant thickness changes during charging and discharging. Therefore, in order to apply uniform pressure to a lithium metal battery using a fluid cushion, it is necessary to reduce the amount of fluid inside during charging and increase the amount of fluid inside during discharging. However, using a fluid tank to adjust the amount of fluid in the fluid cushion makes it difficult to miniaturize the battery system.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a battery system that can apply uniform pressure to battery cells even when the thickness of the battery cells changes significantly due to charging and discharging, and that can be made smaller, thereby contributing to improved energy efficiency. [Means for solving the problem]

[0007] The inventors discovered that the above problems can be solved by placing a gas cushion between battery cells or between a battery cell and an end plate, connecting the gas cushion to a pipe having a compressor and a relief valve via piping, and controlling the compressor and relief valve based on the pressure of the gas cushion, and thus completed the present invention.

[0008] (1) A battery system comprising: a cell stack in which a plurality of battery cells are stacked; a pair of end plates arranged at both ends of the cell stack in the stacking direction; a gas cushion arranged at least one between the battery cells and between the battery cell and the end plate; a pipe having a compressor and a relief valve; piping connecting the gas cushion and the pipe; and a cushion controller, wherein the gas cushion is an elastic container filled with gas, and the cushion controller operates the compressor to introduce gas into the pipe when the pressure of the gas cushion is less than a preset value, and operates the relief valve to exhaust the gas in the pipe when the pressure of the gas cushion exceeds the preset value.

[0009] According to the battery system (1), the decrease in pressure of the gas cushion caused by a decrease in the thickness of the battery cell due to discharge or the like can be eliminated by introducing gas using a compressor installed in the pipe. Furthermore, the increase in pressure of the gas cushion caused by an increase in the thickness of the battery cell due to charging or the like, which causes the gas cushion to be compressed, can be suppressed by venting the gas using a relief valve installed in the pipe. Therefore, even if the thickness of the battery cell changes significantly due to charging and discharging, uniform pressure can be applied to the battery cell. Furthermore, since a tank for storing gas is not required, miniaturization is facilitated.

[0010] (2) The battery system described in (1), wherein the elastic container is housed in an outer elastic container, and a liquid is filled between the elastic container and the outer elastic container.

[0011] According to the battery system of (2), heat generated by the battery cells can be absorbed by the liquid filled between the elastic container and the outer elastic container, so that the temperature rise of the battery cells due to charging and discharging can be suppressed. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a battery system that can apply uniform pressure to battery cells even when the thickness of the battery cells changes significantly due to charging and discharging, and that can be made smaller. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram illustrating a battery system according to a first embodiment of the present invention. [Figure 2] 1 is a cross-sectional view of a battery cell that can be used in a battery system according to a first embodiment of the present invention. [Figure 3] 2 is a schematic diagram illustrating a charging state of the battery system shown in FIG. 1. FIG. [Figure 4] FIG. 4 is a schematic diagram illustrating a battery system according to a second embodiment of the present invention. [Figure 5] FIG. 5 is a schematic diagram illustrating the charging state of the battery system shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiments described below are merely examples of the present invention, and the present invention is not limited to the following.

[0015] [First embodiment] Fig. 1 is a schematic diagram illustrating a battery system according to a first embodiment of the present invention. Fig. 2 is a cross-sectional view of a battery cell that can be used in the battery system according to the first embodiment of the present invention. Fig. 3 is a schematic diagram illustrating the charging state of the battery system shown in Fig. 1.

[0016] As shown in FIG. 1, the battery system 100 of this embodiment includes a cell stack 1, a pair of end plates 2a, 2b, a gas cushion 3, a pipe 4, piping 5 connecting the gas cushion 3 and the pipe 4, and a cushion controller 6.

[0017] The cell stack 1 is a stack of multiple (two in FIG. 1) battery cells 10. End plates 2a, 2b are arranged at both ends of the stacking direction (X direction in FIG. 1) of the cell stack 1. Gas cushions 3 are arranged between the battery cells 10 and between the battery cells 10 and the end plates 2a, 2b.

[0018] The battery cell 10 is a lithium metal battery that uses lithium ions as a charge transfer medium. As shown in FIG. 2, the battery cell 10 includes an electrode stack 18 in which a positive electrode layer 11 and a negative electrode layer 14 are stacked with a solid electrolyte layer 17 interposed therebetween, and an exterior body 19 that houses the electrode stack 18. The positive electrode layer 11 includes a positive electrode current collector 12 and a positive electrode active material layer 13. The negative electrode layer 14 includes a negative electrode current collector 15 and a metal layer 16. When the battery cell 10 is charged, lithium ions released from the positive electrode active material layer 13 pass through the solid electrolyte layer 17 and are deposited on the surface of the metal layer 16 of the negative electrode layer 14, forming a lithium deposit layer, and the thickness of the negative electrode layer 14 increases. The lithium deposit layer acts as a negative electrode active material layer and is lost by releasing lithium ions during discharge. Therefore, the volume of the battery cell 10 changes during charging and discharging. Therefore, the pressure applied by the battery cell 10 to the gas cushion 3 changes during charging and discharging. The stacking direction of the electrode stack 18 (X direction in FIG. 2) is the same as the stacking direction of the cell stack 1. That is, the multiple battery cells 10 of the cell stack 1 are stacked along the stacking direction of the electrode stack 18. Note that, in the battery cell 10 shown in FIG. 2, one electrode stack 18 is housed in the exterior body 19, but multiple electrode stacks 18 may be housed in the exterior body 19.

[0019] The positive electrode current collector 12 is not particularly limited in material or shape as long as it has the function of collecting current from the positive electrode layer 11. Examples of materials for the positive electrode current collector 12 include aluminum, aluminum alloys, stainless steel, nickel, iron, and titanium, and among these, aluminum, aluminum alloys, and stainless steel are preferred. Examples of the shape of the positive electrode current collector 12 include foil and plate shapes.

[0020] The positive electrode active material layer 13 contains at least one type of positive electrode active material. There are no particular limitations on the positive electrode active material, and any material used in the positive electrode layers of general solid-state secondary batteries can be used. As the positive electrode active material, for example, a layered active material containing lithium, a spinel-type active material, an olivine-type active material, etc. can be used. Specific examples of the positive electrode active material include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), LiNi p Mn q Co r O2(p+q+r=1), LiNi p Al q Co r O2 (p+q+r=1), lithium manganese oxide (LiMn2O4), Li 1+x Mn 2-x-y Examples include heteroelement-substituted Li-Mn spinel represented by MO4 (x+y=2, M=at least one selected from Al, Mg, Co, Fe, Ni, and Zn), lithium titanate (oxide containing Li and Ti), and lithium metal phosphate (LiMPO4, M=at least one selected from Fe, Mn, Co, and Ni).

[0021] The positive electrode active material layer 13 may optionally contain a solid electrolyte in order to improve lithium ion conductivity. It may also optionally contain a conductive additive in order to improve conductivity. Furthermore, it may also optionally contain a binder in order to achieve flexibility. There are no particular restrictions on the solid electrolyte, conductive additive, and binder, and those used in the positive electrode layers of general solid secondary batteries may be used.

[0022] The material of the positive electrode lead wire 11a may be the same as or different from the material of the positive electrode current collector 12. The positive electrode lead wire 11a may be integrally connected to the positive electrode current collector 12.

[0023] The material and shape of the negative electrode current collector 15 are not particularly limited as long as it has the function of collecting current from the negative electrode layer 14. Examples of materials for the negative electrode current collector 15 include nickel, copper, and stainless steel. Examples of the shape of the negative electrode current collector 15 include a foil shape, a plate shape, and the like.

[0024] The metal layer 16 is not particularly limited in material or shape as long as it has the function of densely depositing lithium ions. A metallic lithium layer or a layer of a metal that forms an alloy with lithium can be used as the metal layer 16. Examples of metals that form an alloy with lithium include Mg, Si, Au, Ag, In, Ge, Sn, Pb, Al, and Zn. The metal that forms the metal layer 16 may be in the form of a powder or a thin film. By using the negative electrode layer 14 having this metal layer 16, a uniform lithium deposit layer can be formed on the surface of the metal layer 16.

[0025] The material of the negative electrode lead wire 14a may be the same as or different from the material of the negative electrode current collector 15. The negative electrode lead wire 14a may be integrally connected to the negative electrode current collector 15.

[0026] The solid electrolyte layer 17 contains at least one type of solid electrolyte. The solid electrolyte is not particularly limited as long as it has lithium ion conductivity, and examples thereof include sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, and halide solid electrolytes. Examples of sulfide solid electrolytes include Li2S-P2S5 and Li2S-P2S5-LiI. The sulfide solid electrolyte may have an argyrodite-type crystal structure. Examples of oxide solid electrolytes include NASICON-type oxides, garnet-type oxides, and perovskite-type oxides. Examples of NASICON-type oxides include oxides containing Li, Al, Ti, P, and O (e.g., Li 1.5 Al 0.5 Ti 1.5 Examples of garnet-type oxides include oxides containing Li, La, Zr, and O (e.g., LiLaZrO12 Examples of perovskite oxides include oxides containing Li, La, Ti, and O (for example, LiLaTiO3).

[0027] The exterior body 19 is expandable and contractible in accordance with changes in the volume of the battery cells 10 due to charging and discharging. A laminate film can be used as the material for the exterior body 19. The laminate film can be a three-layer film having an inner resin layer, a metal layer, and an outer resin layer stacked in this order from the inside. The outer resin layer can be, for example, a polyamide (nylon) layer or a polyethylene terephthalate (PET) layer, the metal layer can be, for example, an aluminum layer, and the inner resin layer can be, for example, a polyethylene layer or a polypropylene layer.

[0028] The end plates 2a and 2b act to restrain the cell stack 1 in the stacking direction. The restraining force of the end plates 2a and 2b makes it possible to adjust the surface pressure applied to the cell stack 1 via the gas cushion 3. There are no particular restrictions on the material of the end plates 2a and 2b, and various materials used for end plates in battery systems can be used. The end plates 2a and 2b may be fixed in place with restraining devices such as bind bars.

[0029] The gas cushion 3 is an elastic container 31 filled with a gas 32. The elastic container 31 is made of a contractible elastic body. The elastic container 31 may be made of a material such as rubber, elastomer, or laminate film. The gas 32 may be air or a non-flammable gas (nitrogen, carbon dioxide, etc.).

[0030] The pipe 4 has a compressor 41 and a relief valve 42. In this embodiment, the compressor 41 is disposed at one end of the pipe 4, and the relief valve 42 is disposed at the other end. The pipe 4 is connected to the gas cushion 3 via a piping 5. The pressure of the gas cushion 3 (pressure applied from the gas cushion 3 to the battery cell 10) can be adjusted by adjusting the pressure of the pipe 4 using the compressor 41 and the relief valve 42. The pressure inside the pipe 4 varies depending on conditions such as the usage state (during charging or discharging) and the outside air temperature, but is adjusted to, for example, a range of 0.90 MPa or more and less than 1.0 MPa.

[0031] The cushion controller 6 controls the compressor 41 and the relief valve 42 based on the pressure of the gas cushion 3. When the pressure of the gas cushion 3 is less than a preset value, the cushion controller 6 activates the compressor 41 to introduce the gas 32 into the pipe 4. On the other hand, when the pressure of the gas cushion 3 exceeds the preset value, the cushion controller 6 activates the relief valve 42 to exhaust the gas 32 in the pipe 4. The set value of the pressure of the gas cushion 3 may be set taking into consideration the state (charge state, discharge state) of the battery cell 10 and the outside air temperature.

[0032] A control method when the pressure of the gas cushion 3 falls below a preset value will be described with reference to FIG. 1. The arrows in FIG. 1 indicate the flow of the gas 32 when the pressure of the gas cushion 3 falls below a preset value. When the thickness of the battery cell 10 decreases due to discharge or the like, and the thickness of the gas cushion 3 increases, the pressure of the gas cushion 3 decreases. When the pressure of the gas cushion 3 falls below a preset value, the cushion controller 6 activates the compressor 41. When the compressor 41 introduces the gas 32 into the pipe 4, the pressure in the pipe 4 increases. The increase in pressure in the pipe 4 causes the gas 32 to flow into the gas cushion 3 via the piping 5. This increases the pressure of the gas cushion 3. When the pressure of the gas cushion 3 reaches the preset value, the cushion controller 6 stops the compressor 41.

[0033] A control method when the pressure of the gas cushion 3 exceeds a preset value will be described with reference to FIG. 3. The arrows in FIG. 3 indicate the flow of the gas 32 when the pressure of the gas cushion 3 exceeds a preset value. In a charged battery system 100a, the thickness of the battery cell 10a increases due to charging. The increased thickness of the battery cell 10a presses the gas cushion 3a, causing it to decrease in thickness. The decrease in the thickness of the gas cushion 3a increases the pressure of the gas cushion 3a. When the pressure of the gas cushion 3a increases and exceeds a preset value, the cushion controller 6 activates the relief valve 42. The gas 32 in the gas cushion 3a is released to the outside through the relief valve 42 via the piping 5 and the pipe 4, causing the pressure of the gas cushion 3 to decrease. Therefore, even if the thickness of the battery cell 10a increases, the pressure of the gas cushion 3a does not increase excessively, and a uniform pressure can be applied to the battery cell 10a. When the pressure in the gas cushion 3 drops to a set value, the cushion controller 6 shuts off the relief valve 42 .

[0034] The pressure of the gas cushion 3 can be measured using, for example, a pressure sensor. The pressure of the pipe 4 may be measured as the pressure of the gas cushion 3. The pressure of the gas cushion 3 may be calculated based on, for example, the following formula (1) based on Boyle's law. P×V / T=constant(1) In the formula (1), P represents the pressure of the gas cushion, V represents the volume of the gas cushion, and T represents the temperature of the gas cushion.

[0035] According to the battery system 100 of this embodiment configured as described above, a decrease in pressure of the gas cushion 3 when the thickness of the battery cell 10 decreases due to discharge or the like can be eliminated by introducing the gas 32 using the compressor 41 arranged in the pipe 4. Furthermore, when the thickness of the battery cell 10 increases due to charging or the like and the gas cushion 3 is pressed, an increase in pressure of the gas cushion 3 can be suppressed by exhausting the gas 32 using the relief valve 42 arranged in the pipe 4. Therefore, even if there is a large change in thickness due to charging and discharging of the battery cell 10, a uniform pressure can be applied to the battery cell 10. Furthermore, since a tank for storing the gas 32 is not required, miniaturization is facilitated.

[0036] [Second embodiment] Fig. 4 is a schematic diagram illustrating a battery system according to a second embodiment of the present invention. Fig. 5 is a schematic diagram illustrating the charging state of the battery system shown in Fig. 4. The arrows in Fig. 4 indicate the flow of gas 32 when the thickness of the battery cell 10a decreases. The arrows in Fig. 5 indicate the flow of gas 32 when the thickness of the battery cell 10a increases.

[0037] 4, the battery system 101 of this embodiment is the same as the battery system 100 of the first embodiment, except that the elastic container 31 of the gas cushion 3 is housed in an outer elastic container 33, and a liquid 34 is filled between the elastic container 31 and the outer elastic container 33. For this reason, the same reference numerals are used to designate components common to the battery system 100 of the first embodiment, and descriptions thereof will be omitted.

[0038] The outer elastic container 33 is formed from a contractible elastic body. Examples of materials that can be used for the outer elastic container 33 include rubber, elastomer, and laminated film. Examples of materials that can be used for the liquid 34 include mineral hydraulic oil, phosphate ester hydraulic oil, water, and glycol solvents. The outer elastic container 33 is in contact with the battery cell 10, and is configured so that the heat generated by the battery cell 10 can be absorbed by the liquid 34.

[0039] In the battery system 101 of this embodiment, when the thickness of the battery cell 10 decreases due to discharge or the like and the pressure of the gas cushion 3 falls below a preset value, the cushion controller 6 activates the compressor 41. As shown in Fig. 4, when the compressor 41 introduces the gas 32 into the pipe 4, the gas 32 flows into the gas cushion 3 via the piping 5, and the pressure of the gas cushion 3 increases.

[0040] 5, in the battery system 101a in a charged state, the thickness of the gas cushion 3a decreases due to an increased thickness of the battery cell 10a, and when the pressure of the gas cushion 3a exceeds a preset value, the cushion controller 6 activates the relief valve 42. The gas 32 in the gas cushion 3a is exhausted to the outside from the relief valve 42 via the piping 5 and the pipe 4, and the pressure of the gas cushion 3a decreases.

[0041] According to the battery system 101 of this embodiment configured as described above, similarly to the battery system 100 of the first embodiment, the compressor 41 and the relief valve 42 are arranged in the pipe 4, so that even if there is a large change in thickness of the battery cell 10 due to charging and discharging, it is possible to apply uniform pressure to the battery cell 10. Also, since a tank for storing the gas 32 is not required, it is easy to make the system smaller. Furthermore, since the heat generated by the battery cell 10 can be absorbed by the liquid 34, it is possible to suppress a rise in the temperature of the battery cell 10 due to charging and discharging.

[0042] Although the embodiments of the present invention have been described above, the present invention is not limited to these. For example, in the above embodiments, the gas cushions 3 are disposed both between the battery cells 10 and between the battery cells 10 and the end plates 2a, 2b, but the position of the gas cushions 3 is not limited to this. The gas cushions 3 may be disposed in at least one of the positions between the battery cells 10 and between the battery cells 10 and the end plates 2a, 2b.

[0043] In the above embodiment, the battery cell 10 has been described as a solid-state battery having the solid electrolyte layer 17, but the battery cell 10 is not limited to this. The battery cell 10 may be, for example, a non-aqueous battery that uses an organic electrolytic solution as the electrolyte, or a polymer battery that uses a polymer gel (polymer). [Explanation of symbols]

[0044] 1 Cell stack 2a, 2b End plates 3. 3a Gas cushion 4 Pipes 5 Piping 6 Cushion Controller 10, 10a battery cells 11 Positive electrode layer 11a Positive lead wire 12 Positive electrode current collector 13 Cathode active material layer 14 negative electrode layer 14a Negative lead wire 15 Negative electrode current collector 16 metal layer 17 Solid electrolyte layer 18 Electrode laminate 19 Exterior body 20 End Plate 31 Elastic container 32 Gas 33 Outer elastic container 34 liquid 41 Compressor 42 Relief valve 100, 100a, 101, 101a Battery Systems

Claims

1. a cell stack formed by stacking a plurality of battery cells; A pair of end plates arranged at both ends of the cell stack in the stacking direction; a gas cushion disposed between the battery cells and / or between the battery cells and the end plate; a compressor and a pipe having a relief valve; a piping that connects the pipe and the gas cushion; a cushion controller; The gas cushion is an elastic container filled with gas, The cushion controller operates the compressor to introduce gas into the pipe when the pressure of the gas cushion is less than a preset value, and operates the relief valve to exhaust the gas in the pipe when the pressure of the gas cushion exceeds the preset value.

2. The battery system according to claim 1 , wherein the elastic container is housed in an outer elastic container, and a liquid is filled between the elastic container and the outer elastic container.

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