Measurement unit, measurement device, measurement method, and safety evaluation method

Abstract

To provide a measurement unit capable of evaluating safety of a battery by measuring a voltage change of the battery in which an internal short circuit occurs in a relatively small number of layers.SOLUTION: A measurement unit according to an embodiment of the present disclosure is a unit that measures at least one of a voltage and a current when an electrode layer in a battery is short-circuited, and includes: a base on which the battery is placed; a needle for making a hole in the battery placed on the base; a holder that holds the needle and moves the needle so as to make the hole in the battery placed on the base; a displacement measurement device that measures a displacement amount of the needle with respect to the base; and a first voltage measurement device that measures at least one of the voltage and the current of the battery in which the hole is made.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a unit, a measuring device, a measuring method for measuring state changes in interlayer short circuits (internal short circuits) in batteries having a stacked structure, and a method for evaluating the safety of batteries that have interlayer short circuits, and in particular to measuring the state changes and evaluating the safety by controlling the number of layers that are internally short-circuited. [Background technology]

[0002] In recent years, the use of rechargeable batteries has been increasing in various fields, such as electronic devices, automobiles, and renewable energy. Such batteries may experience internal short circuits due to the intrusion of foreign matter into the battery during manufacturing or the intrusion of foreign matter from the outside during use. A method for evaluating the safety of a battery in the event of an internal short circuit is known (Japanese Patent Laid-Open Publication No. 2023-081127). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-081127 Summary of the Invention [Problem to be solved by the invention]

[0004] In the evaluation method of Patent Document 1, an outer casing containing an electrode group formed by stacking a positive electrode, a negative electrode, and a separator, and a metal piece is pressed with a pressure jig, and the metal piece breaks through the separator, causing an internal short circuit. Because the metal piece has a height (dimension) of 0.3 mm or more in the direction of breaking through the separator, there is a risk that it will break through the relatively large number of stacked layers of positive electrode, negative electrode, and separator, and may not be able to cause an internal short circuit in a relatively small number of layers, such as one or two layers. There is a need to evaluate the safety of batteries that have experienced an internal short circuit in a relatively small number of layers.

[0005] The present disclosure has been made based on the above-mentioned circumstances, and aims to provide a measurement unit that can cause an internal short circuit with a relatively small number of layers and can evaluate the safety of the battery by measuring at least one of the voltage and current of the battery that has been internally short-circuited. [Means for solving the problem]

[0006] A measurement unit according to one embodiment of the present disclosure is a unit that measures at least one of the voltage and current when an electrode layer in a battery is short-circuited, and includes a base on which the battery is placed, a needle for piercing a hole in the battery placed on the base, a holder that holds the needle and moves it to pierce the battery placed on the base, a displacement measuring instrument that measures the amount of displacement of the needle relative to the base, and a first measuring instrument that measures at least one of the voltage and current of the battery in which a hole has been pierced. [Effects of the Invention]

[0007] The measurement unit of the present disclosure can generate an internal short circuit in a relatively small number of layers of a battery, and can measure at least one of the voltage and current of the battery due to this internal short circuit to evaluate the safety of the battery. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic front view showing a measurement unit according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic side view of the measurement unit of FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along line AA in FIG. [Figure 4] FIG. 4 is a schematic front view of a needle provided in the measurement unit of FIG. [Figure 5] FIG. 5 is a schematic side view of the needle of FIG. [Figure 6] FIG. 6 is a schematic front view showing a measuring instrument according to an embodiment of the present disclosure. [Figure 7]FIG. 7 is a schematic front view showing a state in which another battery is connected to a battery to be measured in a measurement method according to an embodiment of the present disclosure. [Figure 8] FIG. 8 is a schematic front view showing a state in which a DC power supply is connected to a battery to be measured by this measurement method. [Figure 9] FIG. 9 is a graph showing the change in voltage of a battery that has been internally short-circuited, measured by this measurement method. [Figure 10] FIG. 10 is a graph showing the change in voltage between the battery shown in the graph of FIG. 9 and a needle that internally shorted the battery. [Figure 11] FIG. 11 is a graph showing the voltage change of a battery that has been internally short-circuited using a measurement method according to one embodiment of the present disclosure, the temperature change of the battery, the voltage change between the internally short-circuited needle and the battery, and the displacement of the needle. [Figure 12] Figure 12 is a graph showing the voltage change of an internally short-circuited battery, the current change between the internally short-circuited battery and a battery connected in parallel to the internally short-circuited battery, the temperature change of the internally short-circuited battery, the voltage change between the internally short-circuited needle and the internally short-circuited battery, the needle displacement amount, and the needle load change, using a measurement method that is another embodiment of the present disclosure. [Figure 13] FIG. 13 is a graph showing the relationship between the amount of energy of a current rushing from an external power source into a battery that has experienced an internal short circuit, and the amount of energy of the internal short circuit alone, and the time since the internal short circuit. [Figure 14] FIG. 14 is a graph showing the relationship between the effective value of the current rushing in from an external power source to a battery with an internal short circuit, the effective value of the current with only an internal short circuit, and the amount of energy in each case. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Description of the embodiments of the present disclosure] (1) A measurement unit according to one embodiment of the present disclosure is a unit that measures at least one of the voltage and current when an electrode layer in a battery is short-circuited, and includes a base on which the battery is placed, a needle for piercing a hole in the battery placed on the base, a holder that holds the needle and moves it to pierce the battery placed on the base, a displacement measuring instrument that measures the amount of displacement of the needle relative to the base, and a first measuring instrument that measures at least one of the voltage and current of the battery in which the hole has been pierced.

[0010] The measurement unit includes a displacement measuring device that measures the displacement of a needle used to puncture a battery placed on a base, thereby controlling the depth to which the needle penetrates the battery. This allows the number of layers penetrated by the needle in the battery's stack, including the positive electrode layer, separator layer, and negative electrode layer, to be controlled, allowing for short-circuiting through a relatively small number of layers in the stack. Furthermore, by controlling the needle's penetration depth, the measurement unit can control the needle's contact with, puncture, and penetration of each of the layers. The measurement unit also includes a measuring device that measures at least one of the voltage and current (hereinafter sometimes simply referred to as "voltage / current") of the punctured battery, allowing for measurement of changes in the voltage / current of the battery that has experienced an internal short circuit.

[0011] (2) In (1) above, the measurement unit may further include a second measuring device that measures at least one of the voltage and current between the battery and the needle, or the first measuring device may be capable of further measuring at least one of the voltage and current between the battery and the needle. That is, the measurement unit may be configured to measure the voltage / current between the needle and the battery in addition to measuring the voltage / current of the battery. By providing multiple measurement targets, safety evaluation of the battery can be performed from multiple perspectives.

[0012] (3) In the above (1) or (2), the displacement measuring device may have a first connector connected to the needle and a second connector connected to the base, thereby enabling the amount of displacement of the needle to be measured easily and accurately.

[0013] (4) In the above (3), the base may have a main body on which the battery is placed, a pair of columns standing on the main body, and a beam spanning the pair of columns at a distance from the surface of the battery placed on the main body, and the second connection part may be connected to the beam part. This can improve the accuracy of the displacement measurement.

[0014] (5) In any of (1) to (4), a control unit may be further provided that controls the start and stop of movement of the needle by the holder, and the control unit controls the movement of the needle based on the measurement value of the measuring device. In this way, the movement and stop of the needle can be easily and accurately performed.

[0015] (6) In any of (1) to (5) above, the needle and the holder may be insulated from each other, thereby suppressing measurement errors of the measuring device due to disturbances.

[0016] (7) In any of (1) to (6), a current wire may be further provided to electrically connect the battery to be punctured and the needle, thereby further suppressing the measurement error due to disturbances.

[0017] (8) A measuring instrument according to one aspect of the present disclosure includes a measuring unit according to any one of (1) to (7) above, and a casing that houses at least a portion of the measuring unit.

[0018] The measuring device includes the measurement unit, so that it can measure the voltage / current of the battery due to an internal short circuit in a relatively small number of layers of the battery. In addition, the measuring device includes a casing that houses at least a part of the measurement unit, so that the measurement can be performed while ensuring safety.

[0019] (9) A measurement method according to one aspect of the present disclosure is a method for measuring at least one of the voltage and current when an electrode layer in a battery is short-circuited, comprising the steps of placing the battery on a base, measuring at least one of the voltage and current of the battery placed on the base, moving a needle toward the battery being measured to make a hole, contacting the needle with the outermost electrode layer in the battery where the hole has been made, and stopping the movement of the needle when it has come into contact with the electrode layer.

[0020] In this measurement method, a needle that has pierced a battery is brought into contact with the outermost electrode layer (the outermost electrode layer) in the battery to stop the movement of the needle, and thus this measurement method can measure the voltage change of the battery caused by a short circuit between one electrode layer (the outermost electrode layer) and the needle.

[0021] (10) In the above (9), the measuring step may further measure at least one of the voltage and current between the needle and the battery, thereby measuring the change in voltage / current in the outermost electrode layer.

[0022] (11) In the above (8) or (9), the method may further include the steps of moving the needle, whose movement has been stopped, again toward the inside of the battery, piercing the outermost electrode layer with the needle that is being moved again, and halting the movement of the needle that has pierced the hole again. In this way, it is possible to measure changes in the voltage / current of the battery due to an interlayer short circuit between the outermost electrode layer and an electrode layer adjacent to the outermost electrode layer.

[0023] (12) In any of (9) to (11), the method may further include a step of connecting another battery to the battery, and the measuring step may measure at least one of the voltage and current of the battery to which the other battery is connected. In this way, the influence of the other battery on the internally shorted battery can be observed.

[0024] (13) In any of (9) to (11), the method may further include a step of connecting a DC power supply to the battery, and the measuring step may measure at least one of the voltage and current of the battery connected to the DC power supply. In this way, the influence of the DC power supply on a battery that has an internal short circuit can be observed.

[0025] A safety evaluation method according to one embodiment of the present disclosure is a method for evaluating the safety of an internally short-circuited battery, the method comprising the steps of: placing a battery on a base; connecting another battery or a DC power source to the battery; moving a needle toward the battery placed on the base; causing an internal short-circuit by puncturing the battery with the moved needle; measuring a current I [A] that rushes into the internally short-circuited battery from the other battery or the DC power source; and calculating an amount of energy Ec [A] applied to the internal resistance of the battery from the following equation 1: 2 s]. Ec = Irms 2 × T (1) Here, "Irms 2 " is the effective value [A] of the current I, and "T" is the total time [s] that the current I flows into the battery.

[0026] This safety evaluation method can predict the possibility that the battery will be damaged by the amount of energy Ec applied to the battery, and therefore can easily and reliably evaluate the safety of the battery.

[0027] [Details of the embodiments of the present disclosure] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0028] [Measurement unit] A measurement unit according to one embodiment of the present disclosure measures at least one of the voltage and current when the electrode layers in a battery are short-circuited. As shown in FIGS. 1, 2, and 3, the measurement unit 1 includes a base 10 on which a battery B is placed, a needle 20 for piercing the battery B placed on the base 10, a holder 30 that holds the needle 20 and moves it so as to pierce the battery B placed on the base 10, a displacement measuring device 40 that measures the displacement of the needle 20 relative to the base 10, and a first measuring device (not shown) that measures at least one of the voltage and current of the pierced battery B. The measurement unit 1 of this embodiment also includes a control unit (not shown) that controls the start and stop of the movement of the needle 20 by the holder 30, and a second measuring device 50 that measures the voltage / current between the needle 20 and the battery B. In this embodiment, the first measuring device and the second measuring device 50 measure voltage. The second measuring device 50 is connected to either the positive or negative terminal B1 of the battery B and the needle 20 (see FIG. 2), and measures the voltage between the needle 20 and the battery B (needle-battery voltage). The first measuring device is connected to the positive and negative terminals B1 of the battery B (not shown), and measures the voltage of the battery B.

[0029] <Battery> Battery B is not particularly limited as long as it has a laminate including a positive electrode layer, a negative electrode layer (hereinafter, these two electrode layers are also simply referred to as "electrode layers"), and a separator layer disposed between these electrode layers for electrical insulation, and an exterior housing that houses this laminate, and examples thereof include lithium batteries, lithium ion batteries, etc. Battery B may contain a liquid electrolyte, or may be an all-solid-state battery that contains a solid electrolyte.

[0030] The laminate may be a laminate of multiple electrode layers and multiple separator layers, or may be a laminate of a pair of strip-shaped electrode layers and one separator layer, which are wound together. The exterior body may be made of a rigid material such as metal or resin, or may be made of a flexible material such as a laminate film. The shape of battery B is not particularly limited and may be, for example, a rectangular parallelepiped, cylindrical, or pouch-like shape.

[0031] <Base> The base 10 of this embodiment includes a main body 11 on which a battery B is placed, a pair of pillars 12 standing on the main body 11, and a beam 13 spanning the pair of pillars 12 at a distance from the surface of the battery placed on the main body 11. The main body 11 is formed in a substantially rectangular shape in a plan view, and the pair of pillars 12 are arranged spaced apart at the centers of two opposing sides of the main body 11. A through-hole 13a is provided in the center of the beam 13 in a plan view, and a needle 20 is inserted through this through-hole 13a. It is preferable that at least the surface of the main body 11 (the surface on which the battery B is placed) is made of an insulator, or that an insulating member is arranged on this surface. The surface of the main body 11 may be provided with a shape or member for fixing the placed battery B.

[0032] <needle> 4 and 5, needle 20 has a cylindrical needle body 21 and an expanded portion 22 that is expanded in plan view. Needle 20 may be one in which needle body 21 and expanded portion 22 are formed integrally, or may be formed separately and fixed together. A portion of needle body 21 is held by holder 30, and the end (tip) on the side not held by holder 30 is formed in a conical or pyramidal shape with a tip angle of 5 degrees to 90 degrees.

[0033] The material of needle 20 is not particularly limited as long as it is conductive, and examples include iron, stainless steel, etc. The diameter of needle body 21 is not particularly limited, and can be, for example, 2 mm or more and 5 mm or less.

[0034] A known thermometer such as a thermocouple may be built into the needle body 21 so that the temperature of the battery B, which changes due to an internal short circuit, can be measured.

[0035] <Holder> Holder 30 is configured to be movable in the axial direction of needle 20, and holds and moves needle 20 to pierce battery B. It is preferable that needle 20 and holder 30 are insulated. Insulating needle 20 from holder 30 can suppress disturbance (noise) to the first measuring device and second voltage measuring device 50 during voltage measurement. The means for insulation is not particularly limited, and an insulating member may be placed in the part of holder 30 that holds needle 20, or an insulating coating may be formed on the holding part.

[0036] <Displacement measuring instrument> Displacement measuring device 40 of this embodiment has a sensor unit 43, and a first connection unit 41 and a second connection unit 42 that are connected at one end to sensor unit 43 and extend in the same direction. Displacement measuring device 40 is a so-called clip-type strain gauge. First connection unit 41 is connected to needle 20, and second connection unit 42 is connected to base 10. Specifically, first connection unit 41 is connected to widening unit 22, and second connection unit 42 is connected to beam 13. Sensor unit 43 is electrically connected to the control unit and transmits the measured displacement amount.

[0037] The central portion of the beam portion 13 and the widened portion 22 may be formed with engaging portions (not shown) that engage with the other ends (tips) of the first connecting portion 41 and the second connecting portion 42. The engaging portions are formed, for example, as notches or hooks, and are formed to hold the tips. The tips may be formed with engaged portions (not shown) that engage with the engaging portions. By engaging the tips with the engaging portions, the widened portion 22 and the beam portion 13 can easily hold the displacement measuring device 40, and the amount of displacement can be measured with high precision.

[0038] The number of displacement measuring devices 40 arranged in the measurement unit 1 may be one, but preferably multiple. By arranging multiple displacement measuring devices 40, the amount of displacement of the needle 20 can be measured with high accuracy. In this embodiment, two displacement measuring devices 40 are provided, and they are arranged so that the first connection portion 41 and the second connection portion 42 face each other.

[0039] The displacement measuring device 40 is preferably disposed in a position close to the tip of the needle 20. For this reason, the position of the widened portion 22 on the needle body 21 of the needle 20 is preferably close to the tip of the needle body 21. By disposing the displacement measuring device 40 in a position close to the tip of the needle body 21, measurement errors due to deformation such as bending of the needle 20 when the needle 20 presses against the battery B can be suppressed.

[0040] The resolution of the displacement measuring device 40 is preferably equal to or less than the thickness of the electrode layer. The upper limit of the resolution is preferably 0.0070 mm / μ, more preferably 0.0050 mm / μ, and even more preferably 0.0025 mm / μ, for example. By having the resolution equal to or less than the upper limit, one electrode layer can be short-circuited. The lower limit of the resolution is not particularly limited and may be, for example, 0.0001 mm / μ.

[0041] <Measuring instrument> The first measuring device is connected to the positive and negative terminals B1 of battery B to measure the voltage of battery B. The second measuring device 50 is connected to either the positive or negative terminal B1 of battery B and the needle 20 to measure the needle-battery voltage. If the first measuring device is capable of measuring voltage in two systems, the second measuring device does not need to be provided. The first measuring device and second measuring device 50 (hereinafter, these two measuring devices will also be simply referred to as "measurements") are not particularly limited, and known voltmeters may be used.

[0042] For the needle-to-battery voltage, if the outermost electrode layer of the laminate housed in battery B is positive, the positive electrode cable of the measuring device is connected to needle 20, and the negative electrode cable of the measuring device is connected to the negative electrode terminal B1 of battery B. If the outermost electrode layer is negative, the negative electrode cable of the measuring device is connected to needle 20, and the positive electrode cable of the measuring device is connected to the positive electrode terminal of battery B. In FIG. 2, both the positive electrode cable and the negative electrode cable are shown as electrode cables 51.

[0043] The measurement unit 1 may include a current wire 60 that electrically connects the needle 20 and the battery B (see FIG. 1). Specifically, the current wire 60 may connect the needle 20 and the surface (outer surface) of the exterior body of the battery B. This can suppress noise caused by the movement of the needle 20, enabling voltage to be measured with high accuracy.

[0044] <Control unit> The control unit instructs the start and stop of movement of the holder 30 and receives the amount of displacement measured by the displacement measuring device 40. It is preferable that the control unit is electrically connected to the measuring device and receives the voltage value measured by the measuring device.

[0045] The control unit preferably controls the movement of the needle 20 based on the measurement value of the measuring device. That is, it is preferable to determine the stop and start of movement of the needle 20 (release of the stop) based on the voltage value measured by the measuring device, and to issue instructions to move and stop the holder 30. The voltage value for controlling the stop and start of movement of the needle 20 may be set to any value.

[0046] [Measuring equipment] As shown in FIG. 6, the measuring device 100 includes a measuring unit 1 and a casing 70 that houses at least a portion of the measuring unit 1. The casing 70 is a rectangular box with one side open and a lid (not shown) that seals the opening. A through-hole (not shown) is provided on the other side of the casing 70 or on the lid, and the holder 30 passes through this through-hole, with a portion of the holder 30 housed within the casing 70. The measuring device does not have to be housed within the casing 70. Operational safety can be improved by internally short-circuiting the battery B within the casing 70. A thermometer may be placed within the casing 70 to measure temperature changes within the casing 70.

[0047] [Measurement method] The measurement method includes the steps of placing battery B on base 10, measuring at least one of the voltage and current of battery B placed on base 10, moving needle 20 toward battery B whose voltage is being measured to make a hole, bringing needle 20 into contact with the electrode layer located at the outermost layer within battery B where the hole has been made, and stopping the movement of needle 20 that has come into contact with the electrode layer. Preferably, at least one of the voltage and current between the needle and the battery is further measured during the measuring step.

[0048] The measurement method may further include a step of moving the stopped needle 20 again toward the inside of the battery B, and a step of stopping the movement of the needle 20 again after the needle 20 has penetrated the electrode layer. The measurement method is preferably performed using a measurement unit 1.

[0049] <Placing step> The placing step may include a step of housing the measurement unit 1, excluding the measuring device, in the casing 70. The placing step also includes a step of connecting the measuring device to each of the positive and negative terminals of the battery B placed on the base 10, and a step of connecting the displacement measuring device 40 to the control unit. It may also include a step of connecting the measuring device to the needle 20 and one terminal B1 of the battery B. If the needle 20 has the thermometer, it may also include a step of connecting the thermometer to the control unit.

[0050] <Measurement process> In the measuring step, measurement of the voltage / current of battery B placed on base 10 is started. In this embodiment, voltage is measured. The above measurement may include measurement of the voltage of battery B and measurement of the voltage between the needle and the battery.

[0051] <Hole drilling process> In the hole-making step, the needle 20 is moved toward the battery B to make a hole. Specifically, a hole is made in the exterior body of the battery B and in the separator layer (outermost separator layer) disposed between the exterior body and the outermost electrode layer.

[0052] The speed of the needle 20 moving toward the battery B is not particularly limited, but the upper limit of the speed may be, for example, 0.10 mm / sec, 0.05 mm / sec, or 0.01 mm / sec. The lower limit of the speed is not particularly limited, but may be, for example, 0.001 mm / sec. By setting the speed within the above range, the accuracy of measuring the displacement of the needle 20 can be improved, and the needle 20 can be easily stopped.

[0053] The piercing step may include a first movement step of bringing the needle 20 close to the battery B, and a second movement step of piercing the exterior body and the outermost separate layer with the needle 20. In the first movement step, the needle 20 may be moved at a relatively fast speed until the distance between the battery B and the tip of the needle 20 becomes, for example, 1 mm or more and 5 mm or less, and in the second movement step after the first movement step, the needle 20 may be moved within the above speed range to pierce the exterior body and the outermost separate layer.

[0054] <Contacting step> In the contacting step, the needle 20 is brought into contact with the outermost electrode layer. A short circuit caused by contact between the outermost electrode layer and the needle 20 changes the battery voltage and the voltage between the needle and the battery. By measuring this change, early symptoms of a short circuit can be observed. A thermometer may be built into the needle 20 to measure the temperature change of the short-circuited battery B.

[0055] <Process to be stopped> In the stopping step, the movement of the needle 20 that has come into contact with the electrode layer is stopped. The movement of the needle 20 may be stopped after a predetermined time has elapsed after the contacting step, or the movement of the needle 20 may be stopped by control of the control unit when the voltage value measured by the measuring device reaches a predetermined value.

[0056] This measurement method can measure the voltage of Battery B when only one of the outermost electrode layers is short-circuited. This measurement method is suitable for evaluating the safety of Battery B because it allows observation of the behavior of Battery B when short-circuited at the smallest unit.

[0057] <Removal process> In the re-moving step, the needle 20, which has stopped moving, is moved again toward the inside of the battery B. That is, the needle 20, which has stopped in contact with the outermost electrode layer, is started to move so as to penetrate the outermost electrode layer. By re-moving the needle 20, the battery voltage and the needle-to-battery voltage change, and this change can be measured.

[0058] <Re-stopping process> In the step of stopping again, the movement of the needle 20 that has penetrated the outermost electrode layer is stopped again. The needle 20 may be stopped when it penetrates the outermost electrode layer, or when it comes into contact with an electrode layer adjacent to the outermost electrode layer.

[0059] This measurement method includes the above-mentioned re-moving step and the above-mentioned re-stopping step, and thus can measure the voltage of battery B when a hole is made in the outermost electrode layer due to contact between needle 20 and the outermost electrode layer and the hole expands, and can also measure the voltage of battery B when the hole is penetrated and a short circuit occurs only between the outermost electrode layer and the electrode layer adjacent to this outermost electrode layer.

[0060] <Process for connecting other batteries> The above-described measurement method is a method for measuring voltage changes due to an internal short circuit in a single battery, but the measurement method may also be used to connect multiple batteries and measure the voltage / current changes when one of the batteries experiences an internal short circuit. Specifically, as shown in FIG. 7, the measurement method may further include a step of connecting another battery Ba to battery B, and the voltage / current of battery B to which the other battery Ba is connected may be measured in the measurement step. The other battery Ba may be connected in parallel to battery B (see FIG. 7) or in series (not shown). The number of other batteries Ba connected to battery B is not particularly limited and may be one or two or more.

[0061] In products that use batteries, batteries may be installed in the form of a battery pack in which multiple batteries are connected in parallel or series, or a battery unit in which multiple battery packs are connected. If an internal short circuit occurs in one of the connected batteries and the voltage drops, current may inrush (enter) from the other batteries, causing the battery with the internal short circuit to experience an event (such as explosion, rupture, fire, smoke, damage, or electrolyte leakage). By connecting another battery (Ba) and intentionally short-circuiting it, and measuring the voltage / current of battery (B), it is possible to observe the signs, occurrence, and progress of the above-mentioned events in battery (B). In the measurement process, it is also recommended to measure the voltage between battery (B) and pin 20, the voltage of the other battery (B), the current between battery (B) and the other battery (B), and the temperature (surface temperature, internal temperature) of battery (B). Increasing the number of measurement targets allows for detailed observation of information related to the above-mentioned events (changes in battery (B)) and improves the ease and accuracy of evaluating the safety of the battery pack, battery unit, or product. A shunt (200) is recommended for measuring the current between battery (B) and the other battery (B).

[0062] The internal short circuit of battery B may be contact between the outermost electrode layer of battery B and needle 20, or a short circuit between needle 20 and the outermost electrode layer (positive electrode layer or negative electrode layer) of battery B and the adjacent electrode layer (negative electrode layer or positive electrode layer) (a short circuit between a single positive electrode layer and a single negative electrode layer), or a short circuit between needle 20 and three or more electrode layers.

[0063] <Process for connecting the DC power supply> As shown in Figure 8, this measurement method may further include a step of connecting a DC power supply 300 to battery B, and the measuring step may measure the voltage / current of battery B connected to DC power supply 300. If an internal short circuit occurs in one or some of the batteries in a product equipped with the battery pack or battery unit, and high output is required from the product, a large current may inrush from the other batteries into the battery with the internal short circuit, causing the above-mentioned event and potentially damaging the battery pack, battery unit, or product. The safety of battery B, the battery pack, the battery unit, or the product can be evaluated (CISC test) by connecting DC power supply 300 to battery B and injecting a constant current into battery B that has been intentionally short-circuited internally, thereby measuring the voltage / current (Constant-current Inrush during Internal Short Circuit: CISC).

[0064] In this measurement method (CISC test), the battery B and the DC power supply 300 are preferably connected in parallel, and the power supply control unit 400 is electrically connected to the battery B and the DC power supply 300. When the power supply control unit 400 detects a voltage drop due to an internal short circuit in the battery B, it instructs the DC power supply 300 to supply current. The DC power supply 300 may supply current immediately after the internal short circuit in the battery B occurs. Specifically, the DC power supply 300 injects current several milliseconds to several hundred milliseconds after the internal short circuit in the battery B occurs. The current value to be supplied to the battery B is not particularly limited and may be determined taking into consideration the maximum current value, wiring resistance, etc. of the product in which the battery B is installed. The lower limit of the current value may be, for example, 1 A, 10 A, or 100 A. The upper limit of the current value may be, for example, 3000 A.

[0065] In the CISC test, it is preferable to provide a diode 310 in the wiring to protect the DC power supply 300 from reverse current. It is also preferable to provide a switch 320 for stopping the CISC test in an emergency.

[0066] By connecting a DC power supply 300 to battery B and measuring the voltage / current of battery B that has been intentionally short-circuited internally, the safety of battery B, the battery pack, the battery unit, or the product can be evaluated.

[0067] [Safety assessment method] The safety evaluation method is a method for evaluating the safety of a battery that has undergone an internal short circuit, and includes the steps of placing the battery on a base, connecting another battery or a DC power source to the battery, moving a needle toward the battery placed on the base, causing an internal short circuit by having the needle puncture the battery, measuring a current I [A] that rushes into the internally short-circuited battery from the other battery or the DC power source, and calculating the amount of energy Ec [A] applied to the internal resistance of the battery from the following formula 1: 2 s]. Ec = Irms 2 × T (1) Here, "Irms 2 " is the effective value [A] of the current I, and "T" is the total time [s] that the current I flows into the battery.

[0068] This safety assessment method evaluates safety based on the amount of energy Ec applied to an internally shorted battery B by another battery Ba or a DC power source 300. The current I that rushes into the internally shorted battery B from another battery Ba or the DC power source 300 can have a complex current waveform, making it difficult to calculate the amount of heat (Joule heat) generated in battery B. This safety assessment method evaluates the amount of energy Ec applied to battery B even when the rush current has a complex current waveform, making it possible to quantitatively evaluate the possibility of damage to battery B.

[0069] First, calculate the effective value Irms [A] of the inrush current I [A] flowing through the internally shorted battery B using the following equation 2.

number

[0070] Expanding the above equation 2 gives the following equation 3, where the left side is the product of the square of the effective value and time.

number

[0071] When the resistance (internal resistance) inside the internally shorted battery B is expressed as R, the following equation 4 is obtained. (Irms 2 ×R) / (R×T)=(Ws×T) / R=J / R ···(4) Here, "Ws" is the power [W] due to the inrush current I, and "J" is the heat generation amount [J] of the inrush current I.

[0072] From the above, the amount of energy Ec (Equation 1 above) applied to resistance R when an internal short circuit occurs in Battery B can be used as a quantitative evaluation of the state after an internal short circuit occurs in Battery B. As an example, Figures 13 and 14 show the results of a CISC test in which multiple laminate cell batteries (maximum capacity 5.0 Ah) with NCM811 positive electrodes and graphite negative electrodes were used, and inrush currents I of 1 A to 200 A were passed through each of the laminate cell batteries using a DC power source.

[0073] In FIG. 13, the circles indicate damaged batteries, and the two-dot chain line is an approximation of the damaged batteries. By cutting off the inrush current before it reaches this two-dot chain line (below the two-dot chain line in FIG. 13), it is possible to prevent the above-mentioned battery damage (event).

[0074] In FIG. 14, the circles indicate damaged batteries, and the two-dot chain line is an approximation of the damaged batteries. By cutting off the inrush current before it reaches this two-dot chain line (to the left of the two-dot chain line in FIG. 14), damage to the battery can be prevented.

[0075] This safety evaluation method calculates the amount of energy Ec applied to battery B that has experienced an internal short circuit until the above-mentioned event occurs. If the current (energy) rushing into battery B is cut off before the amount of energy applied to battery B reaches the calculated Ec, the above-mentioned event in battery B can be prevented.

[0076] In this safety evaluation method, the amount of energy Ec may be calculated from the behavior (measurement) of the actual current I due to an internal short circuit of battery B, or may be calculated by simulation, and the calculation result from the measured value of the measurement may be compared with the calculation result of the simulation. By using the amount of energy Ec calculated by the simulation, the number of measurements (number of tests) can be reduced, allowing for efficient evaluation. Furthermore, the accuracy of the amount of energy Ec calculated by the measurement can be improved.

[0077] This safety evaluation test method simulates the situation of battery B used as part of the battery pack, battery unit, or product, and causes an internal short circuit in this battery B, making it possible to evaluate the safety of battery B in the event of an internal short circuit under conditions and environments equivalent to those in which it is actually used.

[0078] [Other embodiments] The above-described embodiments do not limit the configuration of the present invention. Therefore, the above-described embodiments may include omissions, substitutions, or additions of components based on the description in this specification and common general technical knowledge, and all of these should be construed as belonging to the scope of the present invention.

[0079] In the above embodiment, the displacement measuring device is described as a clip-type strain gauge, but the displacement measuring device is not particularly limited as long as it can measure the displacement amount of a needle.

[0080] The base is not limited to the above-mentioned configuration and shape as long as it can accommodate the battery and can be configured to measure the amount of needle displacement. [Example]

[0081] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0082] [Example 1] A battery with an initial voltage of 4.2 V and the measurement unit 1 were prepared, and the battery was placed on the base 10. The measurement unit 1, excluding the voltage meter, was placed inside the casing 70. The needle 20 was moved to pierce the battery and contact the outermost electrode layer. The displacement measurement device 40 had a resolution of 0.0025 mm. The control unit was set to stop needle 20 movement when the needle-to-battery voltage reached 4.0 V, restart needle 20 after a predetermined time had elapsed when the needle-to-battery voltage reached 4.0 V, and stop needle 20 movement again when the needle-to-battery voltage reached 4.05 V. Figure 9 shows the change in battery voltage due to the contact, and Figure 10 shows the change in needle-to-battery voltage. Figure 9 shows that the battery voltage dropped due to a short circuit caused by contact between the outermost electrode layer and needle 20. Figure 10 also shows that the needle-to-battery voltage dropped when the needle 20 resumed movement (restart). In FIG. 10, the waveform of the needle-battery voltage is disturbed before the contact between the battery exterior and the needle 20, but this disturbance is noise (spatial noise) caused by the movement of the needle 20.

[0083] [Example 2] A battery with an initial voltage of 4.2 V and measurement unit 1 were prepared, and the battery was placed on base 10. Measurement unit 1, excluding the voltage meter, was placed inside casing 70, and a hole was pierced with needle 20, which contacted the outermost electrode layer. A thermometer was built into needle 20, and the temperature of the battery was measured along with the voltage change. The control unit was configured to stop needle 20 movement when the needle-to-battery voltage reached 4.0 V, restart needle 20 after a predetermined time had elapsed when needle-to-battery voltage reached 4.2 V, stop needle 20 movement again when needle 20 contacted the electrode layer adjacent to the outermost electrode layer, and move needle 20 away from the battery after a predetermined time had elapsed since the re-stop. The results are shown in Figure 11. While there was no significant change in the battery temperature due to a short circuit between the outermost electrode layer and needle 20, it was clear that a short circuit between the outermost electrode layer and the adjacent electrode layer (interlayer short circuit) caused a sudden rise in the battery temperature. The temperature of the battery is restored when the battery voltage and the voltage between the needle and the battery become approximately 0 V. The battery voltage is restored to approximately 3.7 V when the needle 20 moves away from the battery.

[0084] [Example 3] As batteries to be subjected to an internal short circuit, a battery (test battery) with a reduced charge capacity and an initial voltage of 3.67 V, a battery (parallel battery) with an initial voltage of 3.67 V electrically connected in parallel to the test battery, and a measurement unit 1 were prepared. Also prepared were a voltage meter for measuring the voltage of the parallel battery and a current meter for measuring the current of the test battery. The test battery was placed on a base 10, and the measurement unit 1, excluding the voltage meter, was placed inside a casing 70. A hole was pierced in the test battery with a needle 20 to contact the outermost electrode layer.

[0085] The control unit is set to stop the movement of the needle 20 when the needle-battery voltage is 2.5V, to restart the movement of the needle 20 when a predetermined time has passed since the movement of the needle 20 was stopped and the battery voltage was at the initial voltage (3.67V), and to stop the movement of the needle 20 again when the battery voltage dropped by 0.15V (to 3.52V).

[0086] A shunt was placed on the wire connecting the negative terminals of the parallel battery and the test battery, and the current between the test battery and the parallel battery was measured with the current measuring device ("6 - Current Between Battery" in FIG. 12). The voltage of the parallel battery was also measured ("8 - Voltage Between Parallel Battery" in FIG. 12). A thermometer was built into the needle 20 to measure the temperature inside the test battery ("3 - Battery Temperature" in FIG. 12). Two thermometers were placed near the point of the test battery where the needle 20 was to puncture the test battery to measure the change in the surface temperature of the test battery ("1 - Battery Surface Temperature" and "2 - Battery Surface Temperature" in FIG. 12). A thermometer was placed inside the casing 70 to measure the change in temperature inside the casing 70 ("4 - Temperature Inside Casing" in FIG. 12). The load of the needle 20 on the test battery was measured ("5 - Load" in FIG. 12) and the displacement of the holder 30 was measured ("10 - Holder Displacement" in FIG. 12). These measurements, along with the voltage of the test battery ("7-Battery Voltage" in Figure 12), the needle-to-battery voltage ("9-Needle-to-Battery Voltage" in Figure 12), and the displacement of needle 20 ("11-Needle Displacement" in Figure 12) are shown in a graph in Figure 12.

[0087] Figure 12 shows that after the needle 20 was resuspended, a difference occurred between the displacement of the needle 20 and the displacement of the holder 30. This is thought to be because the displacement of the holder 30 includes various displacements due to factors such as thermal expansion of the battery, base 10, and needle 20, making it difficult to measure the displacement with high accuracy. For this reason, it is preferable to measure the displacement of the needle 20 directly, and even more preferably at a location as close to the battery as possible. The needle-to-battery voltage is disturbed between 500 and 1400 seconds and between 1800 and 2400 seconds, and observing such disturbances is significant for evaluating batteries with internal short circuits. Note that the inter-battery current reached 0 A before 2600 seconds because the test battery was disconnected from the parallel battery. [Industrial Applicability]

[0088] The measurement unit of the present disclosure can easily and accurately measure voltage changes due to internal short circuits in a battery, and is therefore suitable for use in evaluating battery characteristics at battery development and manufacturing sites. [Explanation of symbols]

[0089] 1 measuring unit 10 Foundations 11 Main unit 12 Pillar section 13 Beam section 13a Through hole 20 needles 21 Needle body 22 Widening section 30 Holder 40 Displacement measuring instrument 41 First connection part 42 Second connection part 43 Sensor section 50 Second voltage measuring instrument 51 Electrode cable 60 Current Line 70 Casing 100 Measuring Machine 200 flow diverter 300 DC power supply 310 Diode 320 Switch 400 Power supply control unit B,Ba battery B1 terminal

Claims

1. A unit for measuring at least one of a voltage and a current when an electrode layer in a battery is short-circuited, a base on which the battery is placed; a needle for piercing the battery placed on the base; a holder that holds the needle and moves it so as to puncture the battery placed on the base; a displacement measuring device for measuring the displacement of the needle relative to the base; a first measuring device for measuring at least one of the voltage and current of the punctured battery; A measuring unit comprising:

2. a second meter for measuring at least one of the voltage and current between the battery and the needle; or 2. The measuring unit of claim 1, wherein the first measuring device is further capable of measuring at least one of a voltage and a current between a battery and the needle.

3. 2. The measuring unit according to claim 1, wherein the displacement measuring device has a first connection part connected to the needle and a second connection part connected to the base.

4. The above base is a main body on which the battery is placed; A pair of pillars standing on the main body; a beam portion that is spaced apart from a surface of the battery placed on the main body and that is bridged across the pair of columns, The measuring unit according to claim 3 , wherein the second connection portion is connected to the beam portion.

5. a control unit that controls start and stop of movement of the needle by the holder; The measuring unit according to claim 1 , wherein the control unit controls the movement of the needle based on the measurement value of the first voltage measuring device.

6. 2. The measuring unit according to claim 1, wherein the needle and the holder are insulated.

7. The measuring unit according to claim 1 , further comprising a current wire electrically connecting the punctured battery and the needle.

8. A measurement unit according to any one of claims 1 to 7; a casing that houses at least a portion of the measurement unit; A measuring machine comprising:

9. A method for measuring at least one of a voltage and a current when an electrode layer in a battery is short-circuited, comprising: placing the battery on a base; measuring at least one of the voltage and current of the battery placed on the base; moving a needle towards the battery being measured to puncture it; contacting the needle with an outermost electrode layer in the battery that has been perforated; stopping the movement of the needle that has contacted the electrode layer; A measurement method comprising:

10. 10. The measuring method according to claim 9, wherein the measuring step further comprises measuring at least one of a voltage and a current between the needle and the battery.

11. a step of moving the needle, which has stopped moving, again toward the inside of the battery; piercing the outermost electrode layer with the re-moving needle; re-stopping the re-movement of the piercing needle; The measurement method of claim 9 further comprising:

12. further comprising the step of electrically connecting another battery to the battery; 12. The measuring method according to claim 9, wherein the measuring step measures at least one of the voltage and current of the battery to which the other battery is connected.

13. further comprising the step of connecting a DC power source to the battery; 12. The measuring method according to claim 9, wherein the measuring step measures at least one of the voltage and current of the battery connected to the DC power supply.

14. A method for evaluating the safety of a battery that has experienced an internal short circuit, comprising: placing the battery on a base; connecting another battery or a DC power source to the battery; moving a needle toward the battery placed on the base; a step of causing an internal short circuit by the moved needle piercing the battery; measuring a current I [A] flowing into the internally shorted battery from the other battery or the DC power source; From the following formula 1, the amount of energy Ec [A ２ s]; A safety evaluation method comprising: Ec = Irms ２ × T ・・・・(1) Here, "Irms ２ " is the effective value [A] of the current I, and "T" is the total time [s] that the current I flows into the battery.

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