Bipolar battery short circuit inspection method

Abstract

To provide a bipolar battery short circuit inspection method that can be performed after injection and can inspect unopposed parts of composite materials.SOLUTION: A bipolar battery short circuit inspection method includes a first step of injecting an electrolyte into a cell to be inspected to impregnate the cell, and then reducing the pressure to seal the cell, a second step of applying pressure to the cell to be inspected, and a third step of measuring the open circuit voltage of the cell to be inspected. When a cell in a layer other than the outermost layer is inspected as the cell to be inspected, the second step is performed by bringing the inside of a cell adjacent to the cell to be inspected to atmospheric pressure.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for short - circuit inspection of bipolar batteries.

Background Art

[0002] As a method for inspecting a short - circuit in a bipolar battery, there is known a method in which the upper and lower surfaces of the bipolar battery before liquid injection are pressurized, a voltage is applied to the positive and negative electrodes at the start of the laminated collector, and the inspection is performed based on the resistance obtained from the current flowing at this time and the applied voltage (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above - mentioned method, for the portions other than the portions where the positive and negative electrode composite materials face each other (hereinafter referred to as non - facing portions of the composite materials), since pressure is not applied during pressurization, inspection cannot be performed. However, there is also a risk of short - circuit occurring in the non - facing portions of the composite materials. For example, when the inside of the cell is depressurized in a charged state and any one of the cells is opened to atmospheric pressure due to the destruction of the sealing material, a pressure corresponding to the difference in internal pressure is applied to the adjacent cell, and there is a risk that foreign matter mixed in the adjacent cell will break through the separator.

[0005] Also, the above - mentioned method is a method performed before liquid injection. However, since the risk of foreign matter mixing exists until after liquid injection, it is desirable to perform a short - circuit inspection after liquid injection.

[0006] An object of the present invention is to provide a method for short - circuit inspection of a bipolar battery that can be carried out after liquid injection and can inspect non - facing portions of the composite materials.

Means for Solving the Problems

[0007] The short - circuit inspection method according to claim 1 includes: a first step of injecting and impregnating an electrolytic solution into the cell to be inspected, then reducing the pressure and sealing it; a second step of applying pressure to the cell to be inspected; and a third step of measuring the open - circuit voltage of the cell to be inspected. When the cells of layers other than the outermost layer are used as the cells to be inspected, the second step is carried out by bringing the inside of the cells adjacent to the cell to be inspected to atmospheric pressure.

[0008] In the short - circuit inspection method according to claim 1, as the first step, an electrolytic solution is injected and impregnated into the cell to be inspected, and then the pressure is reduced and sealed. As a result, due to the natural potentials of the positive and negative electrodes respectively, an inherent voltage caused by the material is generated. Next, as the second step, pressure is applied to the cell to be inspected. As a result, if there is a foreign object mixed in the cell to be inspected, the foreign object will break through the separator of the cell to be inspected and a short - circuit will occur. When a short - circuit occurs, the potential drops more than when no short - circuit occurs. And then, as the third step, the open - circuit voltage of the cell to be inspected is measured. Thereby, the presence or absence of a short - circuit in the cell to be inspected can be inspected.

[0009] By the way, when the cells of layers other than the outermost layer are used as the cells to be inspected, there are adjacent cells to the cell to be inspected. Therefore, if the inside of the adjacent cells is also under reduced pressure, a pressure corresponding to the difference in internal pressure cannot be applied to the cell to be inspected. Therefore, in the short - circuit inspection method according to claim 1, when the cells of layers other than the outermost layer are used as the cells to be inspected, the second step is carried out by bringing the inside of the cells adjacent to the cell to be inspected to atmospheric pressure. Thereby, pressure can also be applied to the cells of layers other than the outermost layer. As a result, for the cells of layers other than the outermost layer, a short - circuit inspection of the non - facing part of the composite material can be carried out after injecting the liquid.

[0010] The short - circuit inspection method of the bipolar battery according to claim 2 is, in claim 1, taking all the cells included in the bipolar battery as the cells to be inspected, and carrying out the second step in order from the cells of the Nth layer (the outermost layer) to the cells of the first layer, so as to carry out it on all the cells.

[0011] In the short-circuit inspection method according to claim 2, all the cells included in the bipolar battery are the inspection targets. Then, the second step is carried out in order from the cell of the outermost Nth layer to the cell of the first layer, so as to be carried out for all the cells. Therefore, the short-circuit inspection can be efficiently carried out for all the cells.

Effects of the Invention

[0012] As described above, according to the present invention, there is provided a short-circuit inspection method for a bipolar battery that can be carried out after liquid injection and can inspect unopposed portions of the laminated material.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0014] Hereinafter, a short-circuit inspection method for a bipolar battery according to an embodiment will be described.

[0015] First, the bipolar battery 10 to be inspected (hereinafter simply referred to as the battery 10) will be described.

[0016] As shown in FIG. 1, the battery 10 includes a plurality of cells 12 stacked in series. The battery 10 may also be called a battery module. Hereinafter, the number of cells 12 included in the battery 10 is assumed to be N.

[0017] Each cell 12 has a current collector 20 on the positive electrode side, a positive electrode 30, a separator 40, a negative electrode 50, and a current collector 20 on the negative electrode side.

[0018] The battery 10 is a bipolar battery. That is, two adjacent cells 12 among the N cells 12 share a current collector 20. For example, the current collector 20 on the negative electrode side of the cell 12 in the k-th layer and the current collector 20 on the positive electrode side of the cell 12 in the k-1-th layer are the same current collector 20.

[0019] The current collector 20 has a negative electrode side foil 22 and a positive electrode side foil 24. The negative electrode side foil 22 is, for example, a copper foil, and the positive electrode side foil 24 is, for example, an aluminum foil.

[0020] The positive electrode 30 is, for example, LFP (lithium iron phosphate). The negative electrode 50 is, for example, graphite. The formation region of the negative electrode 50 in the current collector 20 is slightly larger than the formation region of the positive electrode 30.

[0021] The end portion of the separator 40 is held by a holder 60. In the drawings, the holding structure is simplified.

[0022] Each cell 12 has a liquid injection port 62 for injecting an electrolytic solution 14 into the cell 12. The liquid injection port 62 is connected to the space on the positive electrode 30 side with respect to the separator 40 within the cell 12. The electrolytic solution 14 is, for example, a non-aqueous electrolytic solution.

[0023] Each cell 12 is held by a holder 60 made of a synthetic resin.

[0024] (Short-circuit inspection method) The short-circuit inspection method according to this embodiment includes a first step, a second step, and a third step. In the first step, after injecting and impregnating an electrolytic solution into the cell to be inspected, it is depressurized and sealed (see FIG. 2). In the second step, pressure is applied to the cell to be inspected (see FIG. 3). In the third step, the open-circuit voltage of the cell to be inspected is measured (see FIG. 4).

[0025] By injecting and impregnating in the first step, due to the natural potentials of the positive electrode 30 and the negative electrode 50 respectively, an inherent voltage caused by the material is generated in each cell 12. Therefore, if the battery 10 is a good product, the same voltage is obtained in each cell 12.

[0026] The pressure reduction in the first step is performed, for example, by placing the battery 10 in the chamber 19 and evacuating it. The sealing in the first step is performed by sealing the liquid injection port 62 with the sealing material 70.

[0027] By applying pressure to the cell 12 to be inspected in the second step, if there is a foreign object 80 in the cell 12 to be inspected, the foreign object 80 will break through the separator 40 and cause a short circuit, resulting in a voltage drop. Note that FIG. 3 schematically shows the state of applying pressure to the cells in the N-1th layer.

[0028] In the third step, by measuring the open-circuit voltage of the cell to be inspected, it is possible to inspect whether there is a short circuit in the cell 12 to be inspected. The measurement is performed, for example, by measuring the voltage from a voltage inspection line (not shown) connected to the positive electrode side foil 24 and the negative electrode side foil 22 corresponding to the cell 12 to be inspected.

[0029] However, the implementation content of the second step is different depending on whether the cell 12 to be inspected is the cell 12 in the Nth layer which is the outermost layer or the cell 12 in a layer other than the outermost layer (layers below the N-1th layer).

[0030] The outermost layer cell 12 is adjacent to the outside 90. Therefore, if the battery 10 is placed under atmospheric pressure, a pressure corresponding to the difference between the inside of the decompressed cell 12 and the outside 90 (atmospheric pressure) is applied to the outermost layer cell 12.

[0031] On the other hand, there are other adjacent cells 12 for the cells 12 in layers other than the outermost layer, and they are not adjacent to the outside 90. Therefore, when the cell 12 in a layer other than the outermost layer is the cell 12 to be inspected, the second step is performed by bringing the inside of the cell 12 adjacent to the cell 12 to be inspected to atmospheric pressure. Specifically, the second step is carried out by making a hole in the sealing material 70 of the adjacent cells 12 provided in the first step. As a result, the adjacent cells 12 are opened to the atmosphere, and a pressure corresponding to the difference between the inside of the inspected cell 12 under reduced pressure and the adjacent cells 12 opened to the atmosphere (atmospheric pressure) is applied to the inspected cell 12. In this way, the second step can also be carried out for the cells 12 in layers other than the outermost layer.

[0032] Then, the second step is carried out in order from the cells 12 in the Nth layer, which is the outermost layer, to the cells 12 in the first layer, so as to be carried out for all the cells. As a result, the second step can be efficiently carried out for all the cells 12, and as a result, the short-circuit inspection for all the cells can be efficiently carried out.

[0033] 〔Supplementary Explanation of the Above Embodiment〕 In the above embodiment, the second step is carried out in order from the cells 12 in the Nth layer, which is the outermost layer, to the cells 12 in the first layer. However, the short-circuit inspection method of the present invention is not limited to this.

[0034] Further, in the above embodiment, as shown in FIG. 3, in the second step when the cells 12 in layers other than the outermost layer are used as the inspected cells 12, the adjacent cells 12 whose inside is set to atmospheric pressure are the cells 12 adjacent to the inspected cells 12 on the positive electrode 30 side. However, the present invention is not limited to this.

[0035] Further, in the above embodiment, as shown in FIG. 3, in the second step when the cells 12 in layers other than the outermost layer are used as the inspected cells 12, the adjacent cells 12 whose inside is set to atmospheric pressure are the cells 12 adjacent to the space on the side connected to the liquid injection port 62 in the internal space of the inspected cells 12. However, the present invention is not limited to this.

Explanation of Reference Numerals

[0036] 10 Bipolar battery 12 Cell

Claims

1. A first step of injecting an electrolytic solution into a cell to be inspected, impregnating it, and then sealing it under reduced pressure; A second step of applying pressure to the cell to be inspected; A third step of measuring the open-circuit voltage of the cell to be inspected; comprising: When cells of layers other than the outermost layer are used as the cells to be inspected, the second step is carried out by bringing the inside of the cells adjacent to the cells to be inspected to atmospheric pressure. A method for short-circuit inspection of a bipolar battery.

2. All cells included in the bipolar battery are used as inspection targets, and the second step is carried out for all cells by sequentially carrying out the second step from the cells of the Nth layer, which is the outermost layer, to the cells of the first layer. The method for short-circuit inspection of a bipolar battery according to Claim 1.

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