Battery short-circuit testing method

Abstract

This invention provides a battery short-circuit inspection method that reduces the time required to identify the electrode unit that has experienced a short circuit, prevents overcharging, and allows for inspection without altering the state of foreign matter. [Solution] The battery short-circuit testing method according to the present disclosure is a battery short-circuit testing method comprising a plurality of electrode units, each containing a positive electrode, a negative electrode, a separator, and an electrolyte in an internal space, arranged inside a battery container, and comprising: a splitting step of removing an electrode unit from inside the battery container and splitting the current collector junctions connected in parallel; a cooling step of cooling the electrode unit removed in the splitting step to a predetermined temperature or lower; a measurement step of applying a voltage to the cooled electrode unit and measuring the resistance value of the electrode unit; and a determination step of determining whether the resistance value falls below a threshold.

Description

Technical Field

[0001] The present disclosure relates to a method for inspecting a short circuit of a battery.

Background Art

[0002] In Patent Document 1, in inspecting the presence or absence of a short circuit in an all-solid-state battery, a method of increasing the resistance by freezing the all-solid-state battery and applying a voltage to the all-solid-state battery with increased resistance to measure the current value is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the inspection method disclosed in Patent Document 1, there is a problem that it takes time to identify the electrode that has caused a short circuit in a battery in which a plurality of electrodes are connected in parallel by winding or stacking inside the cell. In addition, there is a risk that the battery may be overcharged due to the application of voltage.

[0005] The present disclosure has been made in view of the above problems, and provides a method for inspecting a short circuit of a battery that can shorten the time required to identify the electrode unit that has caused a short circuit, prevent overcharging, and perform an investigation without changing the state of foreign matter.

Means for Solving the Problems

[0006] A method for inspecting a short circuit of a battery according to one aspect of the present disclosure is a method for inspecting a short circuit of a battery configured by arranging a plurality of electrode units that house a positive electrode, a negative electrode, a separator, and an electrolytic solution in an internal space inside a battery container, The division step involves removing the electrode unit from inside the battery container and separating the current collector junctions that are connected in parallel, A cooling step in which the electrode unit removed in the division step is cooled to a predetermined temperature or lower, A measurement step of applying a voltage to the cooled electrode unit and measuring the resistance value of the electrode unit, The system includes a determination step of determining whether the resistance value falls below a threshold. [Effects of the Invention]

[0007] This disclosure provides a battery short-circuit inspection method that reduces the time required to identify the electrode unit that has short-circuited, prevents overcharging, and allows inspection without altering the state of foreign matter. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view of a battery cell according to an embodiment of the present disclosure. [Figure 2] This is a cross-sectional view of an electrode unit according to an embodiment of the present disclosure. [Figure 3] This is a flowchart showing a short-circuit testing method for a battery according to an embodiment of this disclosure. [Modes for carrying out the invention]

[0009] The following describes specific embodiments of this disclosure in detail with reference to the drawings. However, this disclosure is not limited to the following embodiments. Also, for clarity, the following descriptions and drawings have been simplified as appropriate.

[0010] <Configuration of battery cell and electrode unit> Figure 1 is a cross-sectional view of a battery cell according to an embodiment of the present disclosure. The battery cell 1 comprises an electrode unit 11 and a battery container 12. The battery cell 1 also comprises multiple electrode units 11. These multiple electrode units 11 are electrically connected in parallel to each other via current collector joints 116, to which current collectors 113 drawn out from inside the electrode unit 11 are joined. Furthermore, all current collectors 113 are drawn out to the outside of the battery container 12 via the current collector joints 116, thereby forming a battery cell 1 with the current collectors 113 as either the positive or negative electrode. The battery container 12 is made, for example, a metal can or a laminate film made by bonding metal foil and a resin such as polypropylene. Although Figure 1 shows three electrode units 11 inside the battery container 12, the size, number, and arrangement of the electrode units 11 in the battery cell 1 are appropriately determined according to the size of the battery container 12 or the intended use of the battery cell 1.

[0011] Figure 2 is a cross-sectional view of an electrode unit according to an embodiment of the present disclosure. The electrode unit 11 comprises a positive electrode active material layer 111, a negative electrode active material layer 112, a current collector 113, a separator 114, and an outer casing 115. In the electrode unit 11, the positive electrode active material layer 111 and the current collector 113 constitute the positive electrode, and the negative electrode active material layer 112 and the current collector 113 constitute the negative electrode. The electrode unit 11 also has an internal space V, in which an electrolyte (not shown) is contained.

[0012] Inside the electrode unit 11, a positive electrode active material layer 111, a negative electrode active material layer 112, a current collector 113, and a separator 114 are arranged, allowing the electrode unit 11 to function as a battery. The electrode unit 11 is configured to function as a secondary battery, such as a lithium-ion secondary battery or a nickel-metal hydride battery. In this embodiment, the electrode unit 11 is exemplified as a lithium-ion secondary battery. Note that multiple layers of the positive electrode active material layer 111, negative electrode active material layer 112, current collector 113, and separator 114 may be stacked within the electrode unit 11, and the number of layers is appropriately determined according to the size of the electrode unit 11 and the intended use of the battery cell 1 in which the electrode unit 11 is housed.

[0013] The positive electrode active material layer 111 is formed on the surface of the current collector 113. The positive electrode active material layer 111 faces the negative electrode active material layer 112 with a separator 114 in between. The positive electrode active material layer 111 contains a positive electrode active material and may optionally also contain an electrolyte, a conductive additive, and a binder. Examples of positive electrode active materials include lithium cobaltate, lithium nickelate, or lithium manganeseate.

[0014] The negative electrode active material layer 112 is formed on the surface of the current collector 113. The negative electrode active material layer 112 faces the positive electrode active material layer 111 with a separator 114 in between. The negative electrode active material layer 112 contains a negative electrode active material and may further optionally contain an electrolyte, a conductive additive, and a binder. Examples of negative electrode active materials include carbon, graphite, or lithium titanate.

[0015] The current collector 113 has one or more positive electrode active material layers 111 and negative electrode active material layers 112 formed on its surface. The current collector 113 faces the separator 114 with the positive electrode active material layer 111 or the negative electrode active material layer 112 in between. Examples of materials for the current collector 113 include aluminum and copper. The current collector 113 may be provided extended outside the outer casing 115, as shown in Figure 1, to enable connection to external terminals.

[0016] The separator 114 prevents a short circuit between the positive electrode active material layer 111 and the negative electrode active material layer 112. The separator 114 is placed between the positive electrode active material layer 111 and the negative electrode active material layer 112. The separator 114 is a porous film made of, for example, polyethylene or polypropylene.

[0017] The outer casing 115 holds the positive electrode active material layer 111, the negative electrode active material layer 112, the current collector 113, the separator 114, and the electrolyte. The outer casing 115 is made of, for example, a metal can or a laminate film made by bonding metal foil and a resin such as polypropylene.

[0018] The current collector joint 116 is formed when the current collectors 113 are joined, and the electrode units 11 are connected in parallel.

[0019] The internal space V is formed as a space surrounded by the current collector 113 and the exterior body 115. Examples of the electrolytic solution accommodated in the internal space V include those obtained by dissolving lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, or the like in a solvent such as ethylene carbonate, dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate.

[0020] <Method for Inspecting Short Circuit of Battery> Next, referring to FIG. 3, a method for inspecting a short circuit of a battery according to an embodiment of the present disclosure will be described. FIG. 3 is a flowchart showing the method for inspecting a short circuit of a battery according to an embodiment of the present disclosure.

[0021] First, the battery cell 1 is disassembled, and the electrode unit 11 is taken out from the battery container 12 (step S1). When disassembling, the current collector joint 116 connected in parallel is divided. The disassembly of the battery cell 1 is performed, for example, in a glove box filled with Ar. When the battery cell 1 contains only one electrode unit 11, the processes after step S2 may be directly performed on the battery cell 1 without performing step S1.

[0022] Subsequently, the electrode unit 11 taken out in step S1 is cooled to a predetermined temperature or lower (step S2). The cooling temperature may be a temperature at which the movement of lithium ions in the electrode unit 11 stops and the lithium ions do not start to move due to freezing even when a voltage is applied. For example, -130°C or lower at which the electrolytic solution freezes and the movement of lithium ions is significantly inhibited is preferable. By cooling the electrode unit 11 to the temperature at which the electrolytic solution freezes, the resistance value of the electrode unit 11 that is not internally short-circuited increases significantly, and it becomes easy to distinguish between the electrode unit 11 that is not internally short-circuited and the electrode unit 11 that is internally short-circuited in step S4. For cooling the electrode unit 11, for example, an ultra-low temperature freezer is used. Also, the electrode unit 11 may be cooled using a refrigerant such as liquid nitrogen or dry ice.

[0023] Next, a voltage is applied to the cooled electrode unit 11, and the resistance of the electrode unit 11 is measured (step S3). Here, if the electrode unit 11 has an internal short circuit, the measured resistance will be much smaller than when there is no internal short circuit. The applied voltage should be a voltage that allows the resistance of the electrode unit 11 to be measured, but it is preferable to be 5V or less to prevent the electrode unit 11 from overcharging. By applying a voltage of 5V or less, it is possible to perform a short circuit test of the electrode unit 11 more safely.

[0024] If the resistance value of electrode unit 11 measured in step S3 falls below the threshold (YES in step S4), it is determined that electrode unit 11 is experiencing an internal short circuit, and the process is terminated. On the other hand, if the resistance value of electrode unit 11 measured in step S3 does not fall below the threshold (NO in step S4), it is determined that electrode unit 11 is not experiencing an internal short circuit. In that case, the investigation may proceed to other factors (step S5).

[0025] The threshold resistance value in step S4 should be a value that allows for the distinction between electrode units 11 that have experienced an internal short circuit and those that have not. For example, it could be 100Ω, 1kΩ, 100kΩ, or 1MΩ.

[0026] Furthermore, the electrode unit 11 that was determined to be NO in step S4 may be subjected to further safety tests before the battery cell 1 is reconfigured. Alternatively, the electrode unit 11 may be placed in a different battery container instead of the battery container 12 removed in step S1 to form a new, separate battery cell.

[0027] As described above, the battery short-circuit inspection method according to the embodiment of this disclosure identifies internal short circuits at the electrode unit level rather than at the battery cell level by removing electrode units from the battery cell and performing a short-circuit inspection using resistance for each electrode unit. This reduces the time required to identify the electrode unit that has short-circuited, prevents overcharging, and provides a battery short-circuit inspection method that can be investigated without altering the state of foreign matter. [Explanation of Symbols]

[0028] 1 battery cell 11 Electrode Units 111 Cathode active material layer 112 Negative electrode active material layer 113 Current collector 114 Separator 115 Exterior 116 Current collector joint 12 Battery container V interior space

Claims

1. A method for testing a short circuit in a battery, comprising a plurality of electrode units, each containing a positive electrode, a negative electrode, a separator, and an electrolyte in its internal space, arranged inside a battery container, The division step involves removing the electrode unit from inside the battery container and separating the current collector junctions that are connected in parallel, A cooling step in which the electrode unit removed in the division step is cooled to a predetermined temperature or lower, A measurement step of applying a voltage to the cooled electrode unit and measuring the resistance value of the electrode unit, The system includes a determination step of determining whether the resistance value falls below a threshold. Method for testing a battery for short circuits.

2. In the measurement step, the voltage applied to the electrode unit is 5V or less. The method for testing a short circuit in a battery according to claim 1.

3. In the cooling step, the electrode unit is cooled to -130°C or below. The method for testing a short circuit in a battery according to claim 1 or 2.

4. If the resistance value does not fall below a threshold in the determination step, the system further comprises a reconstruction step in which the electrode unit is placed back inside the battery container and the battery is reconfigured. The method for testing a short circuit in a battery according to claim 1 or 2.

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