JP2011141257A - Device able to simulate micro-short circuit of lithium ion battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device that generates a micro-short circuit simulatively and can be used for development, manufacture, maintenance, or the like, of a device for detecting the micro-short circuit of a lithium ion battery. <P>SOLUTION: The device is configured such that a circuit is prepared by connecting a switch in series to a capacitor and a resistance connected in parallel, and the circuit is connected between positive and negative electrodes of the lithium ion battery, and then an instantaneous discharge of the lithium ion battery for charging the capacitor when closing the switch is turned into the simulative micro-short circuit of the lithium ion battery. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an apparatus for simulating a micro-short generated in a lithium ion battery, and relates to an apparatus that can be applied to development, manufacturing, calibration, and the like of an inspection apparatus used in the manufacturing stage of a lithium ion battery. Is.

  Lithium-ion batteries used in electronic devices such as notebook computers and mobile phones are increasing in capacity with the expansion of needs, and their production volume is also increasing dramatically. On the other hand, the number of product defects caused by the inclusion of fine substances during manufacturing is not small, and if an accident such as a product fires due to a battery, the manufacturer is expensive due to product recovery and compensation problems. May be a serious problem for battery manufacturers. In addition, batteries for electric vehicles, which are expected to increase in demand in the future, require high voltage and high capacity, and in the event of an accident, there is a risk related to human life, so further quality control will be required. .

  Lithium-ion battery defects are caused by micro-shorts between the electrodes caused by fine metal powder mixed between the positive and negative electrodes and partial excessive precipitation of lithium ions due to non-uniform distribution of electrolyte. It is said that this is caused by an increase in leakage current.

  For this reason, battery manufacturers have inspected manufactured lithium ion batteries to avoid shipping products with micro-shorts. Various inspection methods have been devised, but the most common practice is to measure the difference between the voltage after initial charging and the voltage after standing for several weeks, and the voltage drops below the reference value. It is a method of removing what was done.

  This inspection method is disadvantageous in that it takes time to detect a defect, and an apparatus capable of reliably detecting a micro short in a shorter time is desired. In order to devise and commercialize such a device, a sample of a battery with a micro short circuit is required, but this is a defective sample, which may cause an unexpected accident depending on how it is used. It is extremely difficult for outsiders other than battery manufacturers to obtain this. In addition, such a defective sample battery cannot be used as a reference for maintaining the sensitivity and accuracy of the detection device because it cannot continuously generate a micro short circuit at a constant amount.

  The problem to be solved by the present invention is to provide a device for generating a simulated micro short that can be used for development, manufacture, maintenance, etc. of a device for detecting a micro short of a lithium ion battery.

In the present invention, the above-described problems are solved by the following means.
A circuit in which a switch is connected in series to a capacitor and a resistor connected in parallel is connected between the positive and negative electrodes of a lithium ion battery, and the charge accumulated in the capacitor while the switch is open is discharged through the resistor. A device that makes a momentary discharge of the lithium ion battery when the lithium ion battery charges the capacitor when the switch is closed is a simulated micro short circuit of the lithium ion battery.

  A circuit in which a switch is connected in series to a capacitor and a resistor connected in parallel is made into one set, and a plurality of sets of these are connected in parallel and connected between the positive and negative electrodes of a lithium ion battery. When different from each other, there may be a device capable of generating a simulated micro short circuit of lithium ion batteries having different discharge amounts by closing any one of the switches in each group.

  The selected capacitor and one resistor are connected in parallel via a selection switch capable of selecting one or more of a plurality of capacitors each having a different capacitance, and the switch is connected in series to the parallel connected capacitor and resistor. A circuit connected to the lithium ion battery is connected between the positive and negative electrodes, a simulated micro short circuit is generated when the switch is closed, and the discharge amount of the lithium ion battery varies depending on the combination of opening and closing of the selection switch. In some cases, the device can generate micro-shorts.

  A capacitor that is charged by the lithium ion battery when the switch is closed is pre-charged to a voltage equal to or lower than the lithium ion battery voltage before the switch is closed. In some cases, the device can generate micro-shorts.

  A pair of PNP transistors and NPN transistors that form a thyristor connection by connecting a base and a collector to each other, and a switch that turns on the thyristor connection. The emitter of the PNP transistor is the positive electrode of the lithium ion battery, and the NPN transistor Are connected to the negative electrode of the lithium ion battery via a capacitor, and when the pair of PNP transistors and NPN transistors that constitute a thyristor connection are turned on by the switch, the lithium ion battery charges the capacitor. In which the instantaneous discharge of the lithium ion battery is a simulated micro-short of the lithium ion battery, a bias resistor is connected between the emitter and base of the PNP transistor, and the thyristor connection One of the terminals of the switch to be turned on is connected to the base of the PNP transistor and the other is connected to the base of the NPN transistor, and the emitter of the NPN transistor has a voltage obtained by dividing the voltage of the lithium ion battery via a resistor. The capacitor is configured to be pre-charged before being discharged from the lithium ion battery so that the chattering of the switch does not affect the discharge current of the lithium ion battery. In some cases, the device can generate a simulated micro short of an ion battery.

  A simulation of a lithium ion battery, wherein a photoelectric conversion element is employed as a switch for turning on the thyristor connection, and a signal path for controlling the photoelectric conversion element and a discharge path of the lithium ion battery are electrically insulated. In some cases, the device can generate a micro-short.

  The present invention is configured so that a short-circuiting short-circuit current generated by a micro-short of a lithium ion battery can be simulated by a current charged in a capacitor, and the discharge amount can be arbitrarily set. It can be applied to testing and calibration equipment when developing and manufacturing micro-shorts in lithium-ion batteries.

  FIG. 1 shows one embodiment of the present invention. The current discharged from the lithium ion battery when the lithium ion battery 1 charges the capacitor 2 when the switch 4 is closed flows instantaneously as shown in FIG. When the switch 4 is closed, the lithium ion battery 1 is short-circuited by the capacitor 2, and then the current decreases as the capacitor 2 is charged.

  The micro short is an instantaneous short circuit between electrodes generated by fine contaminants inside the lithium ion battery or excessive precipitation of lithium ions. Since the foreign substance which has short-circuited between the electrodes by the energy of the discharge due to the short circuit disappears in a short time, the discharge current flows only instantaneously. Therefore, the discharge current from the lithium ion battery when the lithium ion battery is short-circuited by the capacitor is equivalent to the short-circuit current inside the lithium ion battery generated by forming an instantaneous discharge path.

  The present invention pays attention to this point, the capacitor 2 for short-circuiting the electrodes of the lithium ion battery 1, the switch 4 for enabling short-circuiting arbitrarily, and the resistor 4 for discharging the electric charge of the capacitor charged by the short-circuit. By providing this, it is possible to generate a micro-short of a lithium ion battery in a simulated manner.

  FIG. 6 shows a discharge circuit having the configuration of FIG. 1 as an equivalent circuit of a lithium ion battery. The resistance value of the resistor 3 is sufficiently larger than the equivalent series resistance 7 of the lithium ion battery 1, and the switch of FIG. The electric charge of the capacitor 2 is sufficiently discharged while 4 is open. In a specific embodiment of the present inventor, the resistance 3 is about 100 kΩ to 1 MΩ.

  If the voltage of the lithium ion battery 1 is E [V], the equivalent series resistance 7 is r [Ω], the capacitance of the capacitor 2 is C [F], and the resistance 3 is negligible, the lithium ion battery 1 The discharge current i is expressed by Equation 1.

Formula 1

リチウムイオン電池１の電極間をコンデンサ２で短絡した瞬間は、電池電圧Ｅはすべて等価直列抵抗７に印加され大きな電流が流れる。その後コンデンサ２が充電されると時間ｔと共にコンデンサ２の電圧が上昇し、これに伴って電流が低下していく。

At the moment when the electrodes of the lithium ion battery 1 are short-circuited by the capacitor 2, all the battery voltage E is applied to the equivalent series resistance 7 and a large current flows. Thereafter, when the capacitor 2 is charged, the voltage of the capacitor 2 increases with time t, and the current decreases accordingly.

  The change of current i with respect to time t is determined by a time constant (product of equivalent series resistance r and capacitor capacitance C). Therefore, when the capacitance of the capacitor 2 is changed, the discharge current flowing time, that is, the discharge amount from the lithium ion battery can be changed. The application of this is the embodiment shown in FIGS.

  In the embodiment of FIG. 2, a plurality of discharge circuits composed of a capacitor 2, a resistor 3, and a switch 4 are connected to one lithium ion battery 1, and the capacitors 2 have different electrostatic capacities in each discharge circuit. By selecting a switch to be closed from a plurality of switches 4, simulated micro-shorts with different discharge amounts can be generated.

  The embodiment shown in FIG. 3 has the same function as the embodiment shown in FIG. 2, but separates the switch 5 for selecting a plurality of capacitors 2 having different capacitances from the switch 4 for short-circuiting the lithium ion battery 1. There is a feature.

  In an actual switch, chattering occurs when the contacts come into contact with each other, and a part of the energy of the discharge is digested as a fine spark. When such a phenomenon occurs, a part of the charge that should originally be transferred from the lithium ion battery to the capacitor is consumed by the switch. When the capacitance of the capacitor is large, the amount of electric charge that moves is large, so that the consumption at the switch can be ignored. However, this error becomes very large as the capacitance decreases. Therefore, it is desirable to employ a wet switch (mercury relay) without chattering as a switch for short-circuiting.

  However, mercury relays are large in shape and expensive. Therefore, as in the embodiment of FIG. 2, it is impossible to reduce the size of the device and to make it expensive to use a single type of switch for switching and short-circuiting a plurality of capacitors. In the embodiment shown in FIG. 3, in consideration of this point, the switch 4 to be short-circuited and the switch 5 to be selected are separated. A wet switch without chattering is adopted as the switch 4 to be short-circuited, and an inexpensive and small switch such as a mechanical contact is adopted as the switch 5 to be selected.

  The amount of micro short discharge generated in an actual lithium ion battery is very small, and if this is simulated in an embodiment of the present invention, the capacitance of the capacitor will be 0.1 pF or less. . Such an electrostatic capacity is difficult to realize due to the influence of the stray capacitance 8 of the switch and the wiring shown in FIG.

  Therefore, in the embodiment shown in FIG. 4, the discharge amount of the lithium ion battery 1 can be reduced by charging the capacitor 2 and the stray capacitance 8 to Vo [V] in advance before closing the switch 4. As shown in Formula 2, the discharge current in the case of FIG. 4 is proportional to the difference between the battery voltage and the voltage of the capacitor 2 that has been charged in advance. However, the discharge current can be varied by varying the charging voltage Vo [V].

Formula 2

  In the embodiment of FIG. 4, a voltage obtained by dividing the battery voltage by the voltage dividing resistor 6 is applied to the capacitor 2 as a circuit for charging the capacitor 2 in advance. The gist of the present invention is that the lithium ion battery 1 is connected to the capacitor 2. The capacitor 2 is charged in advance to change the amount of discharge current, and the circuit for charging the capacitor 2 is not limited to the example shown here.

  The method of charging the capacitor in advance is also effective when a semiconductor switch is employed as the switch 4. In FIG. 7, the semiconductor switch is equivalently represented by the switch 4 and the stray capacitance 8. Transistors, MOS-FETs, and the like used as semiconductor switches include feedback capacitance between input and output and output capacitance between switches. In FIG. 7, these are combined to form the stray capacitance 8 existing between the switches.

  The stray capacitance 8 of the semiconductor switch varies depending on the type of semiconductor used, but when the stray capacitance Cs = 1000 pF and the capacitor 2 is C = 10 pF as an example of the MOS-FET for switching, the voltage is divided in FIG. When the resistor 6 is not provided, the voltage Vs between the switch terminals and the voltage Vo of the capacitor 2 are inversely proportional to the respective capacitances as expressed by Equation 3 when the switch is open. Becomes 1/100 of the voltage of the capacitor 2, and even if the switch is open, most of the battery voltage is applied to the capacitor 2, and even if the switch 4 is closed, the discharge from the lithium ion battery 1 to the capacitor 2 Will be very little.

Formula 3

  If the stray capacitance of the semiconductor switch is previously charged with a voltage close to the battery voltage by the voltage dividing resistor 6, the charge charged in the stray capacitance 8 when the semiconductor switch 4 is closed is discharged by the switch, and at the same time, As described above, discharging in proportion to the difference between the voltage E of the lithium ion battery 1 and the voltage Vo of the capacitor 2 is also performed.

  In this way, the method of precharging the capacitor 2 can eliminate the influence of the stray capacitance 8 of the switch and can obtain an arbitrary discharge amount, so that a highly accurate calibration device such as a micro-short detection device is provided. It is a very effective means to do this.

  An embodiment of the present invention using a semiconductor switch will be described with reference to FIG. In this embodiment, a pair of NPN transistor 9 and PNP transistor 10 connected as thyristors operate as switches. It is characterized in that the influence of chattering of the mechanical switch 4 is eliminated by connecting the transistors to thyristors.

  When the switch 4 is open, the PNP transistor 10 is turned off by the bias resistor 11, and the NPN transistor 9 is also kept off because the base current does not flow. When the switch 4 is closed, the base current of the NPN transistor 9 flows through the bias resistor 11, so that the NPN transistor 9 is turned on, and at the same time, the PNP transistor 10 is also turned on to discharge the lithium ion battery 1 to the capacitor 2.

  Since the NPN transistor 9 and the PNP transistor 10 connected to the thyristor continue to be kept on after the switch 4 is opened once the switch 4 is closed, the influence of chattering of the switch 4 can be eliminated. When the capacitor 2 is charged to approximately the voltage of the lithium ion battery 1, the NPN transistor 9 and the PNP transistor 10 are turned off, and thereafter remain off until the switch 4 is closed again.

  Further, in the embodiment shown in FIG. 9, a simulated micro short-circuit can be generated by remote control by using the photoelectric conversion element 12 as the switch 4 of the embodiment using the semiconductor switch. The photoelectric conversion element 12 in FIG. 9 is a photocoupler, and operates in the same manner as when the switch 4 in FIG. 8 is closed when a signal for turning on the LED is applied from the outside. As the photoelectric conversion element 12, other photo MOS switches can be used.

  A very small current instantaneously flows through a current loop formed by the lithium ion battery 1, the NPN transistor 9, the PNP transistor 10, and the capacitor 2 due to a micro short circuit. Therefore, in order to reduce the influence of external noise and accurately reproduce the micro short, the path of the current loop must be made as small as possible. By adopting a photoelectric conversion element as a switch, it is possible to electrically insulate the remote control signal from the current loop path, thereby eliminating noise.

  As described above, when a semiconductor switch is used in the apparatus for generating a simulated micro short circuit according to the present invention, remote control by an external signal becomes possible, and the influence of chattering of a mechanical switch can be eliminated. Enables automatic testing of micro shorts.

  Configuration of the present invention   Embodiment 1 of the present invention for switching the discharge amount of a micro short   Embodiment 2 of the present invention for switching the discharge amount of a micro short   Embodiment of the present invention in which the amount of discharge of a micro short is variable   Discharge current waveform   Equivalent circuit during discharge   Example in consideration of stray capacitance of semiconductor switch   Examples employing semiconductor switches   Example with remote control function by photoelectric conversion

DESCRIPTION OF SYMBOLS 1 Lithium ion battery 2 Capacitor 3 Resistance 4 Switch 5 Selection switch 6 Voltage dividing resistance 7 Equivalent series resistance 8 Floating capacity 9 NPN transistor 10 PNP transistor 11 Bias resistance 12 Photoelectric conversion element

Claims (6)

  A circuit in which a switch is connected in series to a capacitor and a resistor connected in parallel is connected between the positive and negative electrodes of a lithium ion battery, and the charge accumulated in the capacitor while the switch is open is discharged through the resistor. An apparatus for setting a momentary discharge of the lithium ion battery when the lithium ion battery charges the capacitor when the switch is closed as a simulated micro short circuit of the lithium ion battery.   A circuit in which a switch is connected in series to a capacitor and a resistor connected in parallel is made into one set, and a plurality of sets of these are connected in parallel and connected between the positive and negative electrodes of a lithium ion battery. 2. The apparatus according to claim 1, wherein when different from each other, a simulated micro short circuit of a lithium ion battery having a different discharge amount can be generated by closing any one of the switches in each set.   The selected capacitor and one resistor are connected in parallel via a selection switch capable of selecting one or more of a plurality of capacitors each having a different capacitance, and the switch is connected in series to the parallel connected capacitor and resistor. A circuit connected to the lithium ion battery is connected between the positive and negative electrodes, a simulated micro short circuit is generated when the switch is closed, and the discharge amount of the lithium ion battery varies depending on the combination of opening and closing of the selection switch. The apparatus of claim 1 capable of generating a micro-short.   The capacitor charged by the lithium ion battery when the switch is closed is preliminarily charged to a voltage equal to or lower than the lithium ion battery voltage before the switch is closed, thereby eliminating the influence of stray capacitance such as the switch and wiring. The apparatus according to claim 1, wherein a simulated micro short circuit of a lithium ion battery capable of changing a discharge amount of the lithium ion battery can be generated.   A pair of PNP transistors and NPN transistors that form a thyristor connection by connecting a base and a collector to each other, and a switch that turns on the thyristor connection. The emitter of the PNP transistor is the positive electrode of the lithium ion battery, and the NPN transistor Are connected to the negative electrode of the lithium ion battery via a capacitor, and when the pair of PNP transistors and NPN transistors that constitute a thyristor connection are turned on by the switch, the lithium ion battery charges the capacitor. In which the instantaneous discharge of the lithium ion battery is a simulated micro-short of the lithium ion battery, a bias resistor is connected between the emitter and base of the PNP transistor, and the thyristor connection One of the terminals of the switch to be turned on is connected to the base of the PNP transistor and the other is connected to the base of the NPN transistor, and the emitter of the NPN transistor has a voltage obtained by dividing the voltage of the lithium ion battery via a resistor. The capacitor is configured to be pre-charged before being discharged from the lithium ion battery so that the chattering of the switch does not affect the discharge current of the lithium ion battery. A device that can generate a simulated micro-short of an ion battery.   6. A lithium ion battery comprising a photoelectric conversion element as a switch for turning on the thyristor connection according to claim 5 and electrically insulating a signal path for controlling the photoelectric conversion element and a discharge path of the lithium ion battery. A device that can generate a simulated micro-shoot.

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