Battery system

Abstract

The present invention provides a battery system that can suppress contact between a metal material, primarily composed of aluminum, and the positive electrode mixture layer. [Solution] The battery system 1 includes a battery cell 50A which includes a positive electrode current collector foil 60 and a positive electrode mixture layer 56 which is in contact with the positive electrode current collector foil 60, a pressurizing unit 20 which pressurizes the battery cell 50A, a control unit 30 which controls the pressurizing unit 20, and a sensor unit 40 which detects the internal temperature of the battery cell 50A. The positive electrode current collector foil 60 includes metal layers 62, 63 which contain a metal material mainly composed of aluminum, a resin layer 61 which is laminated on the metal layers 62, 63 and contains a resin material which has a second melting point lower than the first melting point of the preceding material, and protective layers 64, 65 which are interposed between the positive electrode mixture layer 56 and the metal layers 62, 63. When the detected temperature detected by the sensor unit 40 is above the second melting point, the control unit 30 performs a first control which controls the pressurizing unit 20 to increase the pressurizing force applied to the battery cell 50A.

Description

Technical Field

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

Background Art

[0002] A positive electrode for a non-aqueous electrolyte secondary battery including a positive electrode current collector made only of a metal mainly composed of aluminum, a protective layer formed on the positive electrode current collector, and a positive electrode mixture layer containing a lithium-containing transition metal oxide and formed on the protective layer is known (see, for example, Patent Document 1). The protective layer of this positive electrode for a non-aqueous electrolyte secondary battery isolates the positive electrode current collector and the lithium-containing transition metal oxide, suppresses the redox reaction in which aluminum contained in the positive electrode current collector participates, and reduces the amount of heat generated during abnormal occurrence.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the above positive electrode is used in a pressurized battery, if the aluminum constituting the positive electrode current collector melts, the melted aluminum may flow out to the outer peripheral portion of the positive electrode due to the pressure applied to the battery. Then, there is a problem that the melted aluminum in the outer peripheral portion comes into contact with the positive electrode mixture layer, resulting in heat generation.

[0005] The problem to be solved by the present invention is to provide a battery system capable of suppressing the contact between a metal material mainly composed of aluminum and the positive electrode mixture layer.

Means for Solving the Problems

[0006] The present invention solves the above problem by providing a positive electrode current collector foil with a metal layer containing a metal material mainly composed of aluminum and having a first melting point, and a resin layer laminated on the metal layer containing a resin material having a second melting point lower than the first melting point, and by performing a first control that increases the pressure applied to the lithium secondary battery when the detected temperature is higher than or equal to the second melting point. [Effects of the Invention]

[0007] According to the present invention, contact between the molten metal material and the positive electrode mixture layer can be suppressed. Therefore, the occurrence of a reaction between the molten metal material and the positive electrode mixture layer can be suppressed, and heat generation can be suppressed. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing a battery system in the first embodiment of the present invention. [Figure 2] Figures 2(a) and 2(b) are cross-sectional views of battery cells included in a battery stack in a first embodiment of the present invention. Figure 2(a) shows the state of the battery cells before executing the first control, and Figure 2(b) shows the state of the battery cells after executing the first control. [Figure 3] Figure 3 is a cross-sectional view showing an electrode stack included in a battery cell according to a first embodiment of the present invention. [Figure 4] Figure 4(a) is a flowchart showing a pressure control method using a battery system in a first embodiment of the present invention, and Figure 4(b) is a flowchart showing another pressure control method using the same battery system. [Figure 5] Figures 5(a) and 5(b) are enlarged cross-sectional views showing a portion of the electrode stack included in a battery cell in the first embodiment of the present invention. Figure 5(a) shows the state of the electrode stack before executing the first control, and Figure 5(b) shows the state of the electrode stack after executing the first control. [Figure 6]Figure 6 is a cross-sectional view showing a battery cell in a second embodiment of the present invention, Figure 2(a) shows the state of the battery cell before executing the first control, and Figure 2(b) shows the state of the battery cell after executing the first control. [Figure 7] Figure 7(a) is a cross-sectional view showing a battery cell in a third embodiment of the present invention, and Figure 7(b) is a cross-sectional view showing the cross-section obtained when the battery cell is cut along the line VIIb-VIIb in Figure 7(a). [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the drawings.

[0010] <First Embodiment>

[0011] Figure 1 is a schematic diagram showing the battery system 1 in the first embodiment. Figures 2(a) and 2(b) are cross-sectional views of the battery cell 50A included in the battery stack 10 in the first embodiment. Figure 2(a) shows the state of the battery cell 50A before executing the first control, and Figure 2(b) shows the state of the battery cell 50A after executing the first control. Figure 3 is a cross-sectional view showing the electrode stack 52 included in the battery cell 50A in the first embodiment.

[0012] The battery system 1 in this embodiment is mounted on a vehicle. However, this battery system 1 may also be mounted on a machine other than a vehicle. As shown in Figure 1, this battery system 1 comprises a battery stack 10, a pressurizing unit 20, a control unit 30, and a plurality of sensor units 40. The battery stack 10 contains a plurality of (seven in this example) battery cells 50A, and the plurality of battery cells 50A are electrically connected to each other. The plurality of battery cells 50A in this embodiment are stacked along the Z direction in the figure (hereinafter also referred to as the stacking direction). The detailed configuration of the battery cells 50A will be described later. Furthermore, this battery cell 50A corresponds to an example of a "lithium secondary battery" in the present invention.

[0013] The pressing unit 20 applies a pressure P to each battery cell 50A along this stacking direction. The pressing unit 20 in the present embodiment includes a fixed end plate 21, a movable end plate 22, a plurality of shafts 23, and a drive mechanism 24.

[0014] The fixed end plate 21 and the movable end plate 22 sandwich the battery stack 10 from above and below. The fixed end plate 21 is fixed to the shaft 23 and supports the battery stack 10. The movable end plate 22 is not fixed to the shaft 23 and moves in the stacking direction with respect to the fixed end plate 21. By this movement of the movable end plate 22, the pressure P applied by the pressing unit 20 to the battery cell 50A is adjusted.

[0015] The drive mechanism 24 moves the movable end plate 22 along the Z direction. Although not particularly shown, this drive mechanism includes a motor, a motor driver that controls the motor, a conversion mechanism that converts the rotational motion of the motor into a linear motion along the Z direction, and the like. The movable end plate 22 can move along the Z direction by the power transmitted from this conversion mechanism.

[0016] The control unit 30 controls the pressing unit 20. The control unit 30 is composed of a memory such as a ROM or a RAM, and a processor such as a CPU. Although not particularly limited, this control unit 30 may be a battery control unit (BCU). The control unit 30 in the present embodiment can adjust the pressure P applied to the battery cell 50A by controlling the drive mechanism 24. Although details will be described later, the control unit 30 in the present embodiment adjusts the pressure P applied to the battery cell 50A based on the detection value input from the sensor unit 40.

[0017] A plurality (seven in this example) of sensor units 40 each detect the state of each battery cell 50A. The sensor unit 40 in the present embodiment includes at least a temperature sensor capable of detecting the internal temperature T of the battery cell 50A and a displacement sensor capable of detecting the thickness t of the battery cell 50A. The sensor unit 40 outputs the detected value of the internal temperature T of the battery cell 50A and the detected value of the thickness t of the battery cell 50A to the control unit 30.

[0018] As shown in FIG. 2(a), the battery cell 50A includes an exterior body 51 and an electrode laminate 52. The exterior body 51 is not particularly limited and is composed of, for example, a laminate film or the like. The electrode laminate 52 is housed inside the exterior body 51. In the present embodiment, the upper and lower surfaces (both end surfaces in the stacking direction) of the electrode laminate 52 are in contact with the inner surface 51a of the exterior body 51. On the other hand, the side surfaces (outer peripheral surfaces intervening between both end surfaces) of the electrode laminate 52 are separated from the inner surface 51a of the exterior body 51. Therefore, a gap S is formed between the side surface of the electrode laminate 52 and the inner surface 51a of the exterior body 51.

[0019] As shown in FIG. 3, the electrode laminate 52 includes a plurality of negative electrode layers 53, a plurality of negative electrode current collector foils 54, a plurality of electrolyte layers 55, a plurality of positive electrode active material layers 56, and a plurality of positive electrode current collector foils 60 (a first positive electrode current collector foil 60a and a second positive electrode current collector foil 60b).

[0020] The negative electrode layer 53 in the present embodiment contains lithium metal. This lithium metal has a fifth melting point, and this fifth melting point is about 180°C. In the battery cell 50A, during charging, lithium ions move from the positive electrode active material layer 56 through the electrolyte layer 55 to the negative electrode layer 53, and lithium metal is deposited on the negative electrode current collector foil 54. On the other hand, during discharging, the lithium metal in the negative electrode layer 53 moves as lithium ions to the positive electrode active material layer 56 and is occluded in the positive electrode active material layer 56. That is, during discharging, lithium metal is lost from the negative electrode layer 53. Note that the negative electrode layer 53 is not limited to containing lithium metal and may be composed of a negative electrode active material-containing negative electrode active material mixture. Examples of the negative electrode active material are not particularly limited, and carbon-based materials, metal oxide-based materials, and metal-based materials can be exemplified.

[0021] The negative electrode current collector foil 54 is a conductive foil and is not particularly limited, but is composed of, for example, a metal or a conductive resin. As the metal, aluminum, nickel, iron, stainless steel, titanium, or copper can be used. Alternatively, a clad material of nickel and aluminum, or a clad material of copper and aluminum may be used. As the conductive resin, an example is a resin in which a conductive filler is added to a non-conductive polymer material.

[0022] The electrolyte layer 55 contains at least a solid electrolyte. For example, a sulfide solid electrolyte or an oxide solid electrolyte can be used as the solid electrolyte, but a sulfide solid electrolyte is preferred. Furthermore, this electrolyte layer 55 may also contain a polymer electrolyte or a liquid electrolyte.

[0023] The positive electrode mixture layer 56 contains at least a positive electrode active material. While not particularly limited, examples of this positive electrode active material layer include layered rock salt type active materials, spinel type active materials, olivine type active materials, and Si-containing active materials. Examples of layered rock salt type active materials include LiCoO2, LiMnO2, LiNiO2, LiVO2, and Li(Ni-Mn-Co)O2. Examples of spinel type active materials include LiMn2O4 and LiNi 0.5 Mn 1.5 Examples of O4 include olivine-type active materials such as LiFePO4 and LiMnPO4. Examples of Si-containing active materials include Li2FeSiO4 and Li2MnSiO4. Other oxide active materials include, for example, Li4Ti5O 12 Examples include the following. Furthermore, the positive electrode mixture layer 56 may contain a conductive additive and a binder in addition to the positive electrode active material.

[0024] The positive electrode current collector foil 60 includes a resin layer 61, a first metal layer 62, a second metal layer 63, and a pair of protective layers 64 and 65. The resin layer 61 is a plate-shaped resin member and includes a resin material having a second melting point and a thermal conductive material. The second melting point is not particularly limited, but examples include 130°C to 350°C. Examples of such resin materials include polyethylene terephthalate (PET) and polypropylene (PP).

[0025] Furthermore, the second melting point in this embodiment is above the normal operating temperature of the battery cell 50A. The operating temperature of the battery cell 50A is not particularly limited, but is above ambient temperature and below 100°C. As will be described in detail later, the resin layer 61 in this embodiment is set to melt when an abnormality occurs in the battery cell 50A and the battery cell 50A becomes hot. Therefore, by setting the second melting point above the normal operating temperature, the resin layer 61 does not melt during the normal operation of the battery cell 50A, thereby ensuring the performance of the battery cell 50A.

[0026] Furthermore, the thermal conductive material has a higher thermal conductivity than the resin layer. The thermal conductive material is not particularly limited, but may be a particulate material or dispersed in the resin material. Examples of such thermal conductive materials are not particularly limited, but metal chips and the like can be cited. By including such a thermal conductive material in the resin layer 61, the temperature distribution in the resin layer 61 can be suppressed. This improves the responsiveness of the outflow of the resin material, as described later, and suppresses contact between the molten metal material and the positive electrode mixture layer 56.

[0027] In addition, in the present embodiment, the total volume of all the resin layers 61 included in the electrode laminate 52 is larger than the volume of the above-described void S (see FIG. 2(a)). As shown in FIG. 2(b), in such a resin layer 61, the molten resin material can fill the void S. Thereby, even if the metal materials of the first and second metal layers 62 and 63 described later are melted, it is possible to suppress the melted metal material from flowing out to the outer peripheral portion of the electrode laminate 52. As a result, since the contact between the melted metal material and the positive electrode mixture layer 56 can be suppressed, the generation of reaction heat between the metal material and the positive electrode mixture layer 56 can be suppressed.

[0028] In addition, the positive electrode current collector foil 60 in the present embodiment includes a first positive electrode current collector foil 60a and a second positive electrode current collector foil 60b. The second positive electrode current collector foil 60b is disposed above the first positive electrode current collector foil 60a in the electrode laminate 52. And the thickness t2 of the resin layer 61b of the second positive electrode current collector foil 60b is larger than the thickness t1 of the resin layer 61a of the first positive electrode current collector foil 60a (t1 < t2). When the resin layer 61 of the positive electrode current collector foil 60 flows out to the outer peripheral portion of the electrode laminate 52, the molten resin material flows downward (-Z direction) due to gravity. Therefore, by making the resin layer 61a relatively thick and increasing the amount of resin material flowing out from the resin layer 61a, the contact between the melted metal material and the positive electrode mixture layer 56 can be more reliably suppressed. Further, by making the lower resin layer 61b relatively thin, the amount of resin material used can be reduced, and the energy density of the battery cell 50A can be improved.

[0029] A first metal layer 62 is provided on the first main surface 61c of the resin layer 61. The first main surface 61c in the present embodiment is the upper surface of the resin layer 61. The first metal layer 62 is a foil made of a metal material having a first melting point. The above-described second melting point is lower than this first melting point. The first melting point is not particularly limited, but may be 450°C to 700°C. The main component of this metal material is aluminum. That is, this metal material is aluminum or an alloy containing aluminum. The melting point of aluminum is about 660°C.

[0030] A second metal layer 63 is provided on the second main surface 61d of the resin layer 61. In this embodiment, the second main surface 61d is the lower surface of the resin layer 61 and is located on the opposite side from the first main surface 61c. The second metal layer 63 is also a foil made of a metal material mainly composed of aluminum, and this metal material also has the first melting point described above.

[0031] A protective layer 64 is provided on the first metal layer 62. This protective layer 64 is interposed between the positive electrode mixture layer 56 and the first metal layer 62, separating the positive electrode mixture layer 56 and the first metal layer 62. As a result, the protective layer 64 prevents a reaction (specifically, a thermite reaction) between the positive electrode mixture layer 56 and the first metal layer 62. This protective layer 64 contains at least an inorganic compound and a conductive material. The inorganic compound is not particularly limited, but examples include zirconium oxide and hafnium oxide.

[0032] A protective layer 65 is provided beneath the second metal layer 63. This protective layer 65 is interposed between the positive electrode mixture layer 56 and the second metal layer 63, separating them. As a result, the protective layer 65 prevents a reaction between the positive electrode mixture layer 56 and the second metal layer 63. This protective layer 65 is made of the same material as the protective layer 64. However, the protective layer 65 may be made of a different material than the protective layer 64.

[0033] The pressure control method using this battery system 1 will be described below with reference to Figures 4(a), 5(a), and 5(b). Figure 4(a) is a flowchart showing the pressure control method using the battery system 1 in the first embodiment. Figures 5(a) and 5(b) are enlarged cross-sectional views showing a part of the electrode stack 52 included in the battery cell 50A in the first embodiment. Figure 5(a) shows the state of the electrode stack 52 before executing the first control, and Figure 5(b) shows the state of the electrode stack 52 after executing the first control.

[0034] The pressure control method in the first embodiment is not particularly limited, but is performed repeatedly at predetermined intervals while the battery stack 10 is in use. As shown in Figure 4(a), in this pressure control method, first, in step S101, the sensor unit 40 detects the internal temperature T (cell temperature T) of the battery cell 50A. The sensor unit 40 outputs the measured cell temperature T to the control unit 30.

[0035] Next, the control unit 30 compares the cell temperature T measured by the sensor unit 40 with the resin melting point (second melting point) to determine whether the cell temperature T is equal to or greater than the second melting point. The second melting point is stored in the control unit 30 before the pressure control method in this embodiment is executed. Although not particularly limited, when the cell temperature T is equal to or greater than the second melting point, there is a high probability that an abnormality has occurred in the battery cell 50A. When the cell temperature T is 100°C or less, there is no abnormality in the battery cell 50A, and it is highly likely that the battery cell 50A is operating normally.

[0036] In step S102, if it is determined that the cell temperature T is above the second melting point, in step S103, the control unit 30 starts a first control to control the pressurizing unit 20 so that the pressure P applied to the battery cell 50A increases. In this first control, the pressure P is increased by controlling the drive mechanism 24 to move the movable end plate 22 in the -Z direction. In this first control, although not particularly limited, the pressure P is increased from the pressure P1 applied during normal operation to a target pressure P2 that is greater than this pressure P1 (P1 <P2)。

[0037] The target pressure P2 is, for example, 1.5 × P1 or greater. y Less than (1.5 × P1 ≤ P2 ≤ P y ). Here, P y This is the pressure at which deformation begins to occur in a 50A battery cell. Specifically, P y This pressure P is such that a stress equal to the yield point is applied to the 50A battery cell. y This can be calculated by first obtaining the yield point of a 50A battery cell and then basing the calculation on this yield point value.

[0038] In step S103, since the cell temperature T is above the second melting point, at least a portion of the resin layer 61 is melted. As a result, as shown in Figure 5(b), as the pressure P applied to the battery cell 50A increases, the molten resin material flows out to the outer circumference of the electrode laminate 52. Consequently, after the start of the first control, the resin layer 61 has a laminate portion 611 interposed between the first and second metal layers 62 and 63, as well as an outflow portion 612 that has been pushed out from between the first and second metal layers 62 and 63.

[0039] The outlet portion 612 is integrally formed with the laminated portion 611. This outlet portion 612 contains at least a portion of the molten resin material. In this embodiment, the outlet portion 612 covers the outer surfaces of the first and second metal layers 62 and 63, the outer surfaces of the protective layers 64 and 65, and the outer surface of the positive electrode mixture layer 56. Therefore, even if the cell temperature T rises and the metal material contained in the first and second metal layers 62 and 63 melts, the outlet portion 612 can suppress contact between the molten metal material and the positive electrode mixture layer 56.

[0040] Furthermore, during the execution of this first control, the first metal layer 62 and the second metal layer 63 remain separated from each other from the time the pressure P begins to increase until the target pressure P2 is reached, and the laminated portion 611 of the resin layer 61 remains between them. Therefore, even if a short circuit occurs between the positive electrode current collector foil 60 and the negative electrode layer 53, the resistance of the positive electrode current collector foil 60 can be maintained at a high level, thus preventing heat generation due to the short circuit. In order to maintain the laminated portion 611 during pressure increase, the thickness of the resin layer 61 can be set to a certain level or higher, or the resin layer 61 can be made to have a two-layer structure composed of two types of resin materials with different second melting points.

[0041] As shown in Figure 4(a), if it is determined in step S102 that the cell temperature T is below the second melting point, the pressure control in this embodiment is terminated.

[0042] After the start of the first control, the cell temperature T is measured again as shown in step S104. Note that in the flowchart of Figure 4(a), for convenience, the sensor unit 40 measures the cell temperature T in step S101 and then measures it again in step S104, but this is not the only way. The sensor unit 40 may continuously measure the cell temperature T while the pressure control method is being implemented.

[0043] Next, in step S105, the cell temperature T is compared with the first specified temperature T1 to determine whether the cell temperature T is equal to or greater than the first specified temperature T1. This first specified temperature T1 is higher than the second melting point and lower than the first melting point. The first specified temperature T1 is stored in the control unit 30 before the pressure control method in this embodiment is performed.

[0044] In step S105, if it is determined that the cell temperature T is equal to or greater than the first specified temperature T1, in step S106, the control unit 30 interrupts the first control and executes a second control to reduce the pressure applied by the pressurizing unit 20. Although not particularly limited, when the cell temperature T is equal to or greater than the first specified temperature T1, the cell temperature T is higher than when measured in step S101 and may continue to rise. Therefore, in this embodiment, the pressure P is reduced before the cell temperature T reaches the second melting point of the metal material of the first and second metal layers 62, 63. As a result, when the cell temperature T reaches or exceeds the first melting point and the metal material melts, the pressure has been reduced, which can suppress the outflow of the metal material from the first and second metal layers 62, 63.

[0045] Furthermore, if it is determined in step S105 that the cell temperature T is less than the first specified temperature T1, the control unit 30 determines in step S107 whether the pressure P has reached the target pressure P2. If it is determined in step S107 that the pressure P has reached the target pressure P2, the pressure control method is completed. In other words, in this case, the pressure control method is completed when the first control is completed without interruption.

[0046] On the other hand, if it is determined in step S107 that the pressure P is less than the target pressure P2, the process returns to step S103 and continues to increase the pressure P. Then, either the second control to decrease the pressure P is completed in step S106, or the first control is completed in step S107, and the pressure control method is completed.

[0047] In the above embodiment, the pressure reduction control (second control in step S106) is performed by comparing the cell temperature T with the first specified temperature T1. However, the pressure reduction control may also be performed based on the cell thickness, as in the other embodiments described below. Figure 4(b) is a flowchart showing another pressure control method by the battery system 1 in the first embodiment.

[0048] Steps S201 to S203 shown in Figure 4(b) are the same as steps S201 to S203 shown in Figure 4(a), so their explanation is omitted. In step S204, the sensor unit 40 measures the thickness t (cell thickness t) of the battery cell 50A. Here, the cell thickness t is the thickness of the battery cell 50A in the stacking direction.

[0049] Next, in step S205, the cell thickness t measured by the sensor unit 40 is compared with the specified thickness to determine whether the cell thickness t is less than the specified thickness. Here, the specified thickness t is the thickness of the battery cell 50A in which the first and second metal layers 62 and 63 remain separated when the laminated portion 611 of the resin layer 61 melts.

[0050] If, in step S205, it is determined that the cell thickness t is less than the specified thickness, then in step S206, the first control is interrupted and a third control is executed to control the pressurizing unit 20 to reduce the pressure P. This prevents the first and second metal layers 62 and 63 from coming into contact with each other. When this third control is completed, the pressure control method is completed.

[0051] Furthermore, if it is determined in step S205 that the cell thickness t is equal to or greater than the specified thickness, in step S207 the control unit 30 determines whether the pressure P has reached the target pressure P2. If it is determined in step S207 that the pressure P has reached the target pressure P2, the pressure control method is completed. On the other hand, if it is determined in step S207 that the pressure P is less than the target pressure P2, the process returns to step S203 and continues to increase the pressure P. Then, either the third control to decrease the pressure is completed in step S206, or the first control is completed in step S207, and the pressure control method is completed.

[0052] Alternatively, as yet another pressure control method, a pressure reduction control (a fourth control corresponding to the second control in step S106) may be performed before the cell temperature T reaches the fifth melting point (approximately 180°C) of the lithium metal contained in the negative electrode layer 53. In this embodiment, by reducing the pressure applied to the battery cell 50A before the cell temperature T reaches the fifth melting point, when the internal temperature of the battery cell 50A exceeds the fifth melting point and the lithium metal melts, the pressure P is reduced, thus suppressing the outflow of lithium metal. Therefore, contact between the molten lithium metal and other components can be prevented, and thus the generation of heat can be suppressed.

[0053] According to the battery system 1 in the first embodiment described above, contact between the molten metal material and the positive electrode mixture layer 56 can be suppressed. Therefore, the occurrence of a reaction between the molten metal material and the positive electrode mixture layer 56 can be suppressed, and heat generation can be suppressed.

[0054] <Second Embodiment>

[0055] Figures 6(a) and 6(b) are cross-sectional views showing the battery cell 50B in the second embodiment. Figure 6(a) shows the state of the battery cell 50B before executing the first control, and Figure 6(b) shows the state of the battery cell 50B after executing the first control. The battery cell 50B in the second embodiment differs from the first embodiment in that (1) the resin layer 61 further has a covering portion 613 that fills the void S inside the outer casing 51 (see Figure 2(a)). However, the configuration other than the covering portion 613 is the same as that of the first embodiment. Below, only the differences between the battery cell 50B in the second embodiment and the first embodiment will be described, and parts that have the same configuration as in the first embodiment will be denoted by the same reference numerals and their description will be omitted.

[0056] As shown in Figure 6, in the battery cell 50B, a coating portion 613 of the resin layer 61 is formed on the outer periphery of the electrode stack 52. This coating portion 613 is formed integrally with the stack portion 611 (see Figure 5(a)) and covers at least the outer periphery of the positive electrode mixture layer 56 and the outer periphery of the first and second metal layers 62 and 63. In the first embodiment, an outflow portion 612 is formed on the outer periphery of the electrode stack 52 when the first control is executed, whereas in the second embodiment, the coating portion 613 is formed on the outer periphery of the electrode stack 52 before the first control is executed.

[0057] The formation of such a covering portion 613 suppresses contact between the molten metal material and the positive electrode mixture layer 56 when the first and second metal layers 62 and 63 melt, thereby suppressing heat generation. Furthermore, by filling the void S (see Figure 2(a)) with this covering portion 613, the thickness of the laminated portion 611 can be set to be thinner than the thickness of the laminated portion 611 in the first embodiment, thereby improving the volumetric energy density of the battery cell 50B.

[0058] Furthermore, if the covering portion 613 is pre-formed, the resin material flowing out from the laminated portion 611 can flow into minute gaps formed between the outer surfaces of the first and second metal layers 62 and 63 and the inner surface of the covering portion 613. As a result, the outflow portion 612 is more likely to remain between the outer surfaces of the first and second metal layers 62 and 63 and the inner surface of the covering portion 613. Therefore, heat generation can be further suppressed.

[0059] Furthermore, the laminated portion 611 may contain a first resin material having a third melting point, and the covering portion 613 may contain a second resin material having a fourth melting point lower than the third melting point. In other words, the melting point of the covering portion 613 may be lower than that of the laminated portion 611. When the molten first resin material flows out from the laminated portion 611, the covering portion 613 is pressurized outward from the battery cell 50B. At this time, if the covering portion 613 is in a liquid state, the outer casing 51 is less likely to be damaged by the covering portion 613.

[0060] <Third Embodiment>

[0061] Figure 7(a) is a cross-sectional view showing a battery cell in the third embodiment of the present invention, and Figure 7(b) is a cross-sectional view showing the cross-section when the battery cell is cut along the line VIIb-VIIb in Figure 7(a). The battery cell 50C in the third embodiment differs from the first embodiment in that (2) the battery cell 50C is oriented vertically, and (3) the covering portion 613 of the resin layer 61 is not filled in the upper void S1 of the void S (see Figure 2(a)). However, the configuration other than (2) and (3) is the same as that of the second embodiment. Below, only the differences between the battery cell 50C in the third embodiment and the second embodiment will be described, and parts that have the same configuration as in the second embodiment will be denoted by the same reference numerals and their description will be omitted.

[0062] As shown in Figure 7(a), in the third embodiment, the battery cell 50C is oriented vertically. That is, the stacking direction of the negative electrode layer 53, negative electrode current collector foil 54, electrolyte layer 55, positive electrode composite layer 56, and positive electrode current collector foil 60 in the electrode stack 52 of this battery cell 50C is in the X direction, which is perpendicular to the vertical direction (Z direction). By oriented the battery cell 50C vertically in this way, the outflow of metal material from the top of the electrode stack 52 due to gravity can be suppressed.

[0063] As shown in Figures 7(a) and 7(b), the covering portion 613 of the resin layer 61 in this embodiment is not formed on the upper surface side of the electrode stack 52 and does not fill the upper void S1. As described above, since there is little outflow of metal material from the upper part of the electrode stack 52, the amount of resin material used can be reduced by filling the voids other than the upper void S1 with the covering portion 613, without filling the upper void S1 with the covering portion 613. This makes it possible to improve the gravimetric energy density of the battery cell 50C.

[0064] Furthermore, the pressurizing unit 20 in the third embodiment (see Figure 1) is configured to apply pressure to the battery cell 50C along the X direction. In this case, as shown in Figure 7(a), when executing the first control, the pressurizing unit 20 may apply different pressures to the upper part of the battery cell 50C (P3) and the lower part of the battery cell 50C (P4). Specifically, the battery cell 50C has a third main surface 50a, and the third main surface 50a includes a first region 50b located on the upper side (+Z side) of the third main surface 50a and a second region 50c located below the first region 50b (-Z side). When executing the first control, the pressurizing unit 20 applies a first pressure P3 to the first region 50b and a second pressure P4 greater than the first pressure P3 to the second region 50c (P3 <P4)。

[0065] This increases the outflow rate of the resin material in the lower part of the electrode laminate 52, where the outflow rate of metal material is large. As a result, contact between the molten metal material and the positive electrode mixture layer 56 in the lower part of the electrode laminate 52 can be suppressed, thereby suppressing heat generation. [Explanation of Symbols]

[0066] 1…Battery system 10…Battery stack 20... Pressurized section 30…Control Unit 40...Sensor section 50A~50C...Battery cell 51…Exterior 52… Electrode stack 56…Positive electrode mixture layer 60a, 60b... First and second positive electrode current collector foils 61… Resin layer 611...Laminated section 612... Outlet 613... Covering part 62...first metal layer 63…Second metal layer 64,65…protective layer

Claims

1. A lithium secondary battery comprising a positive electrode current collector foil and a positive electrode mixture layer in contact with the positive electrode current collector foil, A pressurizing unit for pressurizing the lithium secondary battery, A control unit that controls the pressurizing section, The lithium secondary battery includes a temperature detection unit for detecting the internal temperature of the battery, The aforementioned positive electrode current collector foil is A metal layer containing a metal material mainly composed of aluminum, A resin layer laminated on the metal layer, comprising a resin material having a second melting point lower than the first melting point of the metal material, It includes a protective layer interposed between the positive electrode mixture layer and the metal layer, The control unit performs a first control to control the pressurizing unit to increase the pressure applied to the lithium secondary battery when the detected temperature detected by the temperature detection unit is equal to or greater than the second melting point.

2. The battery system according to claim 1, After starting the first control, the control unit executes a second control to control the pressurizing unit to reduce the applied pressure if the detected temperature is equal to or greater than a first specified temperature. A battery system in which the first specified temperature is higher than the second melting point and lower than the first melting point.

3. The battery system according to claim 1, The aforementioned resin layer includes a thermal conductive material having a thermal conductivity higher than that of the resin material in the battery system.

4. The battery system according to claim 1, The aforementioned metal layer A first metal layer formed on the first main surface of the resin layer, The resin layer includes a second metal layer formed on a second main surface located opposite to the first main surface and separated from the first metal layer, A battery system in which the first metal layer and the second metal layer are separated when the first control is executed.

5. The battery system according to claim 4, The battery system further includes a thickness detection unit for detecting the thickness of the lithium secondary battery, The control unit, after the start of the first control, executes a third control, which controls the pressurizing unit to reduce the applied pressure if the thickness detected by the thickness detection unit is less than or equal to a predetermined thickness.

6. The battery system according to claim 1, The aforementioned lithium secondary battery is An electrode laminate including the positive electrode mixture layer, The system comprises an outer casing that houses the electrode stack such that a gap is formed between it and the electrode stack, A battery system in which the volume of the resin layer is greater than the volume of the void.

7. A battery system according to any one of claims 1 to 6, The aforementioned resin layer is A laminated portion laminated on the aforementioned metal layer, A battery system including a covering portion that covers the outer surface of the metal layer.

8. The battery system according to claim 7, The aforementioned lithium secondary battery is An electrode laminate including the positive electrode mixture layer, The system comprises an outer casing that houses the electrode stack such that a gap is formed between it and the electrode stack, The aforementioned covering portion is a battery system that fills the aforementioned void.

9. The battery system according to claim 8, The laminated portion includes a first resin material having a third melting point. The covering portion comprises a battery system having a second resin material having a fourth melting point lower than the third melting point.

10. The battery system according to claim 1, The lithium secondary battery is a battery system in which the stacking direction of the positive electrode mixture layer and the positive electrode current collector foil is arranged to be substantially perpendicular to the vertical direction.

11. A battery system according to claim 10, The aforementioned lithium secondary battery is An electrode laminate including the positive electrode mixture layer, The system comprises an outer casing that houses the electrode stack such that a gap is formed between it and the electrode stack, The aforementioned void includes the upper void located above the lithium secondary battery. The aforementioned resin layer is A laminated portion laminated on the aforementioned metal layer, A battery system having a covering portion that fills the portion of the aforementioned void other than the upper void.

12. A battery system according to claim 10, The third main surface of the lithium secondary battery is The first region located on the upper side of the third main surface, A second region located below the first region, The pressurizing unit is a battery system that applies a first pressure to the first region and a second pressure greater than the first pressure to the second region.

13. The battery system according to claim 1, The lithium secondary battery is arranged such that the stacking direction of the positive electrode mixture layer and the positive electrode current collector foil is substantially parallel to the vertical direction. The lithium secondary battery includes a plurality of positive electrode current collector foils, The aforementioned plurality of positive electrode current collector foils are First positive electrode current collector foil, It includes a second positive electrode current collector foil positioned above the first positive electrode current collector foil, A battery system in which the thickness of the resin layer of the second positive electrode current collector foil is greater than the thickness of the resin layer of the first positive electrode current collector foil.

14. The battery system according to claim 1, A battery system in which the second melting point is above the normal operating temperature of the lithium secondary battery.

15. The battery system according to claim 1, The lithium secondary battery includes a negative electrode layer containing a lithium metal having a fifth melting point. The second melting point is lower than the fifth melting point. The control unit performs a fourth control, which controls the pressurizing unit to reduce the applied pressure before the detected temperature reaches the fifth melting point, after the first control has started.

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