JP2008186691A - Usage and system of nonaqueous electrolyte battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a usage and a system of nonaqueous electrolytic battery capable of obtaining a sufficient performance in output under a low-temperature atmosphere. <P>SOLUTION: Charging/discharging operation is performed after a temperature rise in battery by applying a voltage accompanied by a pulsation flow over 100 mV in peak-to-peak value and 1 Hz in frequency, when a battery temperature is lower than a predetermined temperature or a battery impedance is larger than a predetermined setting value. Under this condition, the time can be shortened for rising the temperature, and the increasing impedance can be suppressed when repeatedly performing temperature rise by means of the operation. An especially effective result can be expected when applying a nonaqueous electrolytic material using a lithium titanate to a negative electrode or to a battery system using the nonaqueous electrolytic material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for using a nonaqueous electrolyte battery, and a battery system including the nonaqueous electrolyte battery.

  Non-aqueous electrolyte batteries represented by small and lightweight lithium ion secondary batteries are widely used as power sources for electronic devices such as mobile phones and digital cameras. A general non-aqueous electrolyte battery generally uses a lithium transition metal composite oxide for the positive electrode, a carbon material for the negative electrode, and a carbonate containing a lithium salt for the non-aqueous electrolyte. It is characterized by high energy density.

  In recent years, research on non-aqueous electrolyte batteries using lithium titanate as a negative electrode has been actively conducted, and it is possible to achieve a battery with better charge / discharge cycle performance than conventional lithium ion secondary batteries using a carbon material as a negative electrode. Therefore, it is expected to be applied to, for example, a backup power source for automobiles and the like that are being digitized.

  However, since non-aqueous electrolyte batteries have poor output performance at low temperatures, it is necessary to install a large amount of batteries in order to secure the power necessary for backing up large-scale applied equipment such as automobiles, resulting in a battery system. There was a problem that it was difficult to downsize. Among these, non-aqueous electrolyte batteries using lithium titanate as the negative electrode tend to have a larger negative electrode impedance than lithium ion secondary batteries using carbon materials, depending on the type of non-aqueous electrolyte used. There was a problem in output performance especially at low temperature.

Patent Document 1 states that “secondary batteries are frequently used as a power source for portable devices. In particular, in recent years, power sources for devices that are often used outdoors such as electric tools have been developed. As a secondary battery issue, there is no problem at room temperature, but when charging / discharging in cold temperatures, the resistance increases mainly due to a decrease in the ionic conductivity of the electrolyte and a decrease in the reactivity of the electrode active material. Due to this phenomenon, charging / discharging with a large current cannot be performed, and charging for a long time with a weak current, or a discharge with a large output value cannot be performed and the device does not operate. ” In order to solve the problem (paragraph 0002), “secondary battery, means for charging / discharging the secondary battery, means for controlling charge / discharge of the secondary battery, and means for measuring the temperature of the secondary battery” Charge and discharge system including A is a feature that the temperature of the secondary battery when a charge and discharge less than the proper temperature T _0, that after the temperature of the secondary battery was subjected to pulse discharge conditions to reach T _0, starts charging and discharging (Claim 1) was proposed, and as an example, a nickel-metal hydride battery was charged at 9A for 2s, 2.2s or 2.4s, paused for 2s, and then discharged at 9A for 2s. Further, it is described that pulse charge / discharge is performed in a cycle of resting for 2 seconds, and pulse charge / discharge is performed so as to stop the pulse charge / discharge when the battery temperature reaches a certain temperature.
JP 2006-92901 A

  However, when the method described in Patent Document 1 is applied to a non-aqueous electrolyte battery, the battery temperature can certainly be increased to some extent, but not only does it take a long time to increase the temperature, but also the non-aqueous electrolyte battery. In contrast, non-aqueous electrolytes that when the temperature increase operation by such a prescription is repeated, the impedance (internal resistance) of the battery greatly increases due to deterioration accompanying the deterioration of the battery performance, and the output performance cannot be sufficiently obtained. It turns out that there are problems specific to batteries.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a method of using a nonaqueous electrolyte battery that can obtain sufficient output performance even in a low temperature environment during discharging or charging. Another object of the present invention is to provide a battery system including a nonaqueous electrolyte battery and capable of obtaining sufficient output performance even in a low temperature environment during discharging or charging.

  The present invention is a method of using a nonaqueous electrolyte battery in which a battery is discharged or charged after a voltage with a pulsating flow having a frequency of 1 Hz or more and a PP value (Peak to Peak value) of 100 mV or more is applied.

  The present invention also includes a non-aqueous electrolyte battery, and includes battery temperature measuring means, and pulsating voltage generating means for generating a voltage with a pulsating current having a frequency of 1 Hz or more and a PP value of 100 mV or more. Is a battery system provided with a mechanism capable of applying a voltage accompanied by the pulsating flow to the battery when the temperature is lower than a set temperature.

  The present invention also includes a non-aqueous electrolyte battery, and includes battery impedance measuring means and pulsating voltage generating means for generating a voltage with a pulsating current having a frequency of 1 Hz or more and a PP value of 100 mV or more. Is a battery system including a mechanism capable of applying a voltage accompanied by the pulsating current to the battery when the value of is higher than a set value.

  That is, the present invention relates to a method for using a non-aqueous electrolyte battery or a battery system including a non-aqueous electrolyte battery, and when charging or discharging the battery in order to obtain sufficient output performance even in a low temperature environment. When the battery temperature is lower than the set temperature or when the battery impedance is higher than the set value, a voltage with a pulsating current having a frequency of 1 Hz or more and a PP value of 100 mV or more is applied.

  ADVANTAGE OF THE INVENTION According to this invention, the usage method of the nonaqueous electrolyte battery which can acquire sufficient output performance also in a low temperature environment can be provided. In addition, a battery system including a nonaqueous electrolyte battery and capable of obtaining sufficient output performance even in a low temperature environment can be provided.

  Examples of the “voltage with a pulsating flow having a frequency of 1 Hz or more and a PP value of 100 mV or more” applied include a DC voltage superimposed with an AC wave having a frequency of 1 Hz or more and an amplitude of 100 mV or more. The voltage waveform with respect to the time axis of the voltage accompanied by the pulsating current is not limited, and examples thereof include a sine wave, a rectangular wave, a sawtooth wave, and a triangular wave.

  In the present invention, the output voltage corresponding to the intermediate value of the two peak voltages of the pulsating current applied may be a voltage equal to the open circuit voltage of the battery, or may be higher than the open circuit voltage of the battery. . For example, when a voltage corresponding to the charging voltage of the battery is adopted as the output voltage, the application of the voltage accompanied by the pulsating current can also serve as charging. Further, in the case where float charging is applied to the battery or in the system, when a voltage corresponding to the float charging voltage is adopted as the value of the output voltage, the application of the voltage accompanied by the pulsating current can also serve as the float charging.

  Conversely, even when the battery is in a state that requires charging, a voltage that is higher than the open circuit voltage of the battery is not used as the voltage with the applied pulsating current, and a voltage equal to the open circuit voltage of the battery is used. May be. According to such a configuration, since charging can be performed after the temperature of the electrode has sufficiently increased, charging can be performed without increasing battery impedance, and charging output characteristics, that is, charge acceptance performance is excellent. In addition, the battery can be charged, and the deterioration of the battery accompanying a decrease in performance can be suppressed. When a voltage equal to the open circuit voltage of the battery is to be adopted as the output voltage, the difference from the open circuit voltage of the battery is preferably within 0.1V. By making this difference within 0.1 V, the change in the SOC of the battery due to the application of voltage does not become too large, and the possibility that the battery performance will deteriorate can be reduced.

  The PP value of the pulsating flow to be applied needs to be 100 mV or more. If the PP value is less than 100 mV, it takes time to increase the temperature or decrease the impedance due to the application of the voltage accompanied by the pulsating flow. This is because, as a result, it becomes impossible to take out electric power when necessary.

  It is preferable that the PP value of the pulsating voltage is 1500 mV or less because the battery impedance due to the side reaction in the battery increases and the risk of a decrease in battery life can be reduced.

  The frequency of the applied pulsating voltage must be 1 Hz or more. When the frequency is less than 1 Hz, in a nonaqueous electrolyte battery, the battery impedance increases irreversibly by repeating the pulsating voltage application operation due to side reactions that occur until the battery becomes chargeable / dischargeable. It is because it ends up.

  The frequency of the pulsating voltage to be applied can be arbitrarily selected as long as it is 1 Hz or higher. The frequency of the pulsating voltage is preferably 150 kHz or less because it can reduce the possibility of causing malfunctions due to electromagnetic interference in various control devices. In selecting the frequency of the pulsating voltage, it is preferable to determine in view of the frequency response of the non-aqueous electrolyte battery to be applied or the electrode used in the non-aqueous electrolyte battery, by selecting from this viewpoint, The effect of increasing the battery temperature can be made remarkable.

  For example, FIG. 2 is a board plot showing the frequency dependence of the impedance of the nonaqueous electrolyte battery according to Example 2 described later. Obviously, it can be seen that the impedance rapidly increases in a frequency region lower than 1 Hz. Therefore, the current that flows when a constant pulsating voltage is applied is significantly reduced in a frequency band lower than 1 Hz. Therefore, if a frequency lower than 1 Hz is selected, the time required to raise the battery temperature significantly increases. I can understand.

  The application of the voltage accompanied by the pulsating flow can be continued at least until the temperature of the battery becomes equal to or higher than a preset temperature.

  From this point of view, the battery system of the present invention including battery temperature measuring means may further include a mechanism that does not apply a voltage with a pulsating flow when the battery temperature is equal to or higher than a set temperature. Similarly, the battery system of the present invention including battery impedance measuring means may further include a mechanism that does not apply a voltage accompanied by a pulsating flow when the battery impedance is equal to or lower than a set value.

  The battery system of the present invention may be provided with a battery temperature measuring means and a battery impedance measuring means at the same time and combined with the pulsating voltage generating means.

  The battery system of the present invention may further include a mechanism that prevents normal charge or discharge when the battery temperature is lower than the set temperature value or when the battery impedance is higher than the set value. Good.

  The method of use of the present invention and the battery system of the present invention are a non-aqueous electrolyte battery using a negative electrode active material having a negative electrode working potential of 1 V or more, in particular, electrochemical oxidation-reduction proceeds by a two-phase coexistence reaction and is flat. It is extremely preferable to apply to a non-aqueous electrolyte battery using a negative electrode active material in which a potential change is observed, for example, a non-aqueous electrolyte battery using lithium titanate as a negative electrode active material.

  The reason is that there is very little possibility that lithium is deposited on the negative electrode and the battery performance is deteriorated by applying a voltage with a pulsating flow having a PP value of 100 mV or more.

  In addition, as described above, in terms of problems, the nonaqueous electrolyte battery using lithium titanate for the negative electrode is different from the lithium ion secondary battery using a carbon material, depending on the type of nonaqueous electrolyte used. In addition, since there is a property that a high-resistance film is easily formed on the electrode surface, the negative electrode impedance tends to be large, and the present invention has a big problem in terms of low-temperature output performance. This is because such a big problem can be solved.

Here, the lithium titanate referred to in the present specification is a lithium-titanium composite oxide represented by a basic composition formula of Li ₄ Ti ₅ O ₁₂ and having a spinel crystal structure as a basic skeleton, a part of Ti, or Lithium titanate in which a part of Ti and Li is substituted with other elements such as Mg, Al, Zn, and Co can be preferably used. Moreover, the substance which does not have a spinel type crystal structure, and other impurities may be contained.

  Hereinafter, although the present invention is explained based on one example, the present invention is not limited to the following embodiments.

Example 1
The present embodiment is an example in which the present invention is applied to a battery system in which float charging is performed in a standby state and power is supplied from the battery when discharging is necessary. In this case, the value of the voltage with pulsating current can be equal to the float charging voltage.

  FIG. 1 is a block diagram showing a battery system according to the above embodiment. A battery temperature measuring means 2 is installed in the vicinity of one or a plurality of non-aqueous electrolyte batteries 1, and an output signal P1 from the measuring means 2 is input to the calculation unit 4. In addition to the output signal P1, the calculation unit 4 also receives an output signal P2 from the battery voltage measuring means 3 provided in the battery 1 and a command signal P3 corresponding to the battery discharge request. The calculation unit 4 determines the value of the battery temperature input based on the output signal P1 by comparing with the set temperature value, performs a comprehensive calculation process together with the output signals P2, P3, and switches S1 and Controls the operation of the switch S2. When the calculation unit 4 comprehensively determines that the battery temperature is lower than the set temperature value and a voltage with a pulsating current should be applied to the battery 1 according to the determination result, the calculation unit 4 By controlling S1 and the switch S2 and connecting the output from the pulsating voltage generating means 5 to the battery, a voltage with pulsating current is applied to the battery 1. In addition to the above, the calculation unit 4 operates to disconnect the output from the pulsating voltage generation means 5 when the battery temperature is equal to or higher than the set temperature, and as a result of the large-capacity discharge, the battery voltage is compared to the float charge voltage. Operation that determines that independent charging is necessary in the case of a significant drop and connects the output from the charging means 6 to the battery, and operation that connects the battery terminal to the output terminal at the right end of FIG. 1 according to the discharge command signal P3, etc. Also govern.

  As described above, the example in the case of applying to the battery system that supplies power from the battery when the float charge is performed in the standby state and the discharge becomes necessary has been described. A system that starts charging after the battery temperature and / or battery impedance has entered the set range by applying a voltage with a pulsating flow based on the battery temperature and / or battery impedance determination result, and independent DC in standby mode Float charging is performed from the power supply, but after receiving the discharge command, voltage with pulsating current is applied based on the battery temperature and / or battery impedance judgment result, and the battery temperature and / or battery impedance falls within the set range It can be applied to a system with various specifications such as a system that starts discharging after a long time.

  The impedance measurement method employed by the battery impedance measurement means is not limited as long as it is a measurement method that can reflect the internal resistance of the battery, and can be arbitrarily selected according to the specifications and characteristics of the battery. For example, a current interrupter method, an AC impedance method, a complex impedance method, and the like can be given. As a simple and relatively inexpensive means that can be achieved, an AC impedance method employing an arbitrary frequency (for example, 1 kHz) of 100 mHz to 10 kHz is preferable.

(Example 2)
Next, in the present invention, the reason why the pulsating voltage to be applied must be a frequency of 1 Hz or more and a PP value of 100 mV or more will be described based on experimental data.

Lithium titanate (composition formula: Li _4/3 Ti _5/3 O ₄ ) 85% by mass as a negative electrode active material, 5% by mass of acetylene black as a conductive material, and 10% by mass of PVdF as a binder are solvents. A paste dispersed in N-methyl-2-pyrrolidone (NMP) is prepared, applied to both sides of a 20 μm thick copper foil, dried at 150 ° C. to remove the solvent, and both sides are roll pressed. And compression molded. Thus, the negative electrode provided with the negative mix layer on both surfaces of copper foil was produced.

90% by mass of lithium transition metal composite oxide (composition formula: LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and PVdF5 as a binder A paste in which mass% is dispersed in NMP as a solvent is prepared, applied to both sides of an aluminum foil having a thickness of 20 μm, dried at 150 ° C. to remove the solvent, and both sides are compressed by a roll press. Molded. Thus, the positive electrode provided with the positive mix layer on both surfaces of the aluminum foil was produced.

  A power generating element wound so that a separator, which is a communicating porous body having a thickness of 25 μm and an air permeability of 90 seconds / 100 cc, is positioned between the positive electrode and the negative electrode is 48 mm high, 30 mm wide, and 5.2 mm thick. Was inserted into the battery case container.

  Furthermore, after injecting a non-aqueous electrolyte (electrolyte) into the battery case, the current is 90 mA, the voltage is 4.1 V, the constant current and the constant voltage are charged for 10 hours, the current is 90 mA, and the end voltage is 1.0 V. The charge / discharge consisting of a constant current discharge was repeated 3 cycles. Thus, Example Battery 1 having a rated capacity of 450 mAh was obtained.

The electrolyte solution was prepared by dissolving 1 mol / l LiPF ₆ in a 1: 1: 1 volume ratio of propylene carbonate (PC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC). Then, 3 wt% of vinylene carbonate was added and used.

  A large number of Example batteries 1 were prepared according to the above procedure, and the battery was fully charged by constant current and constant voltage charging with a current of 90 mA, a voltage of 2.5 V, and a charging time of 10 hours.

  The impedance of Example Battery 1 adjusted to a fully charged state in this way was measured with an impedance meter fixed at 1 kHz for AC and found to be 45 mΩ.

  A number of Example batteries 1 adjusted to a fully charged state were divided into seven groups, and the following “temperature increase time test” and “temperature increase cycle test” were performed.

(Temperature rise time test)
Attach a temperature detector to the battery case surface of all batteries, put it in a -20 ° C constant temperature bath for 10 hours or more and confirm that the battery temperature has reached -20 ° C. As it was, an output voltage of 2.5 V accompanied by a pulsating wave with a sine wave superimposed on the DC voltage was applied, and the time until the battery temperature reached −10 ° C. was measured. Here, for each group, the frequency of the voltage accompanying the pulsating current and the PP value were changed as shown in Table 1. The results are shown in Table 1.

(Heating cycle test)
After the battery temperature reached −10 ° C. by the temperature rise time test, the application of the 2.5 V output voltage with pulsation was interrupted, and after 10 hours, the battery temperature reached −20 ° C. again. After confirming, applying the output voltage of 2.5 V accompanied by a pulsating flow was repeated 100 times until the battery temperature reached −10 ° C. again under the same conditions.

  Subsequently, all the batteries were returned to 25 ° C., and the impedance at an alternating current of 1 kHz at 25 ° C. was measured. The results are shown in Table 1 as an increase rate (%) with respect to the impedance value (45 mΩ) before the test.

  As is clear from the results of the temperature rise time test shown in Table 1, the time required for the temperature rise largely depended on the PP value and the frequency. It can be seen that when the frequency is 0.5 Hz, it takes 1 hour or more to raise the temperature, which is a condition that cannot be put to practical use. On the other hand, when the frequency is set to 1 Hz or more, it can be seen that the time required for the temperature rise can be greatly shortened and the condition can be put to practical use. In particular, it can be seen that it is preferable to set the frequency to 60 Hz or more because the time required for temperature increase can be shortened within several minutes. Further, it can be seen that a PP value of 50 mV requires 40 minutes to raise the temperature and is a condition that cannot be put to practical use. On the other hand, it can be seen that by setting the PP value to 100 mV or more, the time required for the temperature increase can be greatly shortened, which is a condition for practical use. In particular, it can be seen that a PP value of 500 mV or more is preferable because the time required for temperature increase can be shortened within several minutes.

  As is apparent from the results of the temperature rise cycle test shown in Table 1, the impedance increase rate greatly depends on the frequency, and when the frequency is set to 0.5 Hz, the impedance increase rate exceeds 20%. It can be seen that the condition is not possible. On the other hand, by setting the frequency to 1 Hz or more, the impedance increase rate could be suppressed to within 10% even after 100 temperature-raising cycles.

  In the battery system of the present invention, the “set temperature” that is a criterion for battery temperature and the “set value” that is a criterion for battery impedance can be set according to the specifications and characteristics of the battery. For example, according to the above embodiment, when the target is to raise the temperature to −10 ° C., the “set temperature” may be set as −10 ° C., and the battery impedance at −10 ° C. Is measured in advance, and the impedance value may be set as the “set value”.

It is a block diagram concerning one example of the battery system of the present invention. It is explanatory drawing which showed the frequency dependence of the impedance of an Example battery.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nonaqueous electrolyte battery 2 Measuring means 4 Calculation part 5 Pulsed voltage generation means

Claims (3)

A method of using a nonaqueous electrolyte battery in which a battery is discharged or charged after applying a voltage with a pulsating flow having a frequency of 1 Hz or more and a PP value of 100 mV or more. A non-aqueous electrolyte battery is provided, and includes a battery temperature measuring means and a pulsating voltage generating means for generating a voltage with a pulsating current having a frequency of 1 Hz or more and a PP value of 100 mV or more, and the battery temperature is lower than a set temperature. A battery system comprising a mechanism capable of applying a voltage accompanied by the pulsating current to the battery. A non-aqueous electrolyte battery is provided, and includes battery impedance measuring means, and pulsating voltage generating means for generating a voltage with a pulsating current having a frequency of 1 Hz or more and a PP value of 100 mV or more. A battery system having a mechanism capable of applying a voltage accompanied by the pulsating current to the battery when the voltage is high.

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