JP6475815B1 - Recycling method for lithium ion battery - Google Patents

Abstract

Regeneration processing is performed using a general DC power supply. By charging a target cell B by repeating a charging period T1 in which a base current Ib and a pulse current Ip are overlapped to form a charging current Ic with a pause period T2 interposed therebetween, and the cell temperature T exceeds a set value Ts. The energization is interrupted, and the energization is terminated when the charge voltage Vc reaches the set value Vs or the charge amount Q reaches the predetermined value Qs. [Selection] Figure 3

Description

  The present invention relates to a method for regenerating a lithium ion battery for electrically regenerating and reusing a deteriorated lithium ion battery.

  A method of electrically regenerating a deteriorated lithium ion battery has been proposed (Patent Document 1).

  The conventional regeneration treatment method is based on performing at least one cycle of a potential control step of setting the potential of the negative electrode lower than that of the positive electrode after setting the negative electrode of the lithium ion battery to a potential higher than that of the positive electrode. The potential of the negative electrode is set higher than the potential of the positive electrode in the range of 0.1 to 2 V, and then lower than the potential of the positive electrode in the range of 0.1 to 5 V. And about 10 seconds each with a rest time of 1 second. However, the former holding time may be 0.1 to 30 seconds, and the latter holding time may be pulse-wise controlled by the reverse potential.

JP 2012-169094 A

  According to such a conventional technique, there is a problem that the external power supply for the regeneration process of the lithium ion battery requires a special power supply device that reversely controls the output potential and energizes the charge / discharge current of the battery.

  Accordingly, an object of the present invention is to provide a regeneration processing method for a lithium ion battery in which a general DC power source can be used by adopting a pulsed charging current in view of the problems of the prior art. is there.

  In order to achieve this object, the configuration of the present invention, when regenerating a deteriorated lithium ion battery for each cell, superimposes a DC base current and a square-wave pulse current while interposing a pause period, The charging period is periodically repeated to energize the target cell. When the cell temperature of the target cell exceeds the set value, the energization is interrupted, and when the energization is interrupted, the cell temperature of the target cell is lower than the set value. The energization is resumed after waiting for the voltage to drop below, and the energization is terminated when the charge voltage reaches a predetermined set value based on the rated charge voltage of the target cell or the charge amount of the target cell reaches a predetermined value. The gist.

  The charging voltage can be detected instantaneously by sampling the terminal voltage of the target cell being energized at a frequency of 1 second or less.

  In addition, after energization, the capacity test may be performed after standing for a predetermined time. When the cell temperature exceeds a specified value after standing for a predetermined time, the cell temperature drops below the specified value. The capacity test may be carried out after waiting for this, and the target cell may be forcibly cooled when waiting for the cell temperature to decrease.

  According to the configuration of the invention, it is possible to effectively regenerate a deteriorated lithium ion battery for each cell. The square-wave pulse current is preferably about 0.5 C ± 10%, and the DC base current is preferably set to about 1/10 of the pulse current. However, C here is a so-called C rate, and the current value when the cell to be reproduced, that is, the target cell is discharged from the fully charged state to the fully discharged state in 1 hour is 1C. Therefore, for example, the current value corresponding to 1C of the cell having the rated capacity Qo Ah is Qo A. The pulse current is preferably set to a pulse frequency of about 1 to 20 kHz and a duty of about 25 to 40%. The charging period and the pause period per time are set to about 5 minutes and 1 minute, respectively. Good. However, these reproduction processing parameters are experimentally determined to be optimum values depending on the type and capacity of the target cell.

  On the other hand, the target cell of the lithium ion battery that is being regenerated is constantly detected and monitored, and when the cell temperature exceeds a set value, energization is interrupted to prevent harmful thermal runaway. The cell temperature is preferably detected, for example, the upper surface temperature and / or the terminal temperature of the target cell. Further, when the charging voltage (terminal voltage of the target cell being energized) reaches a set value or the amount of charge of the target cell due to the charging current reaches a predetermined value, the energization is terminated and the regeneration process can be completed. . However, the set value of the charging voltage and the predetermined value of the charge amount for completing the regeneration process can be set to about 10% increase of the rated charge voltage of the target cell and about 10 to 20% increase of the rated capacity, respectively. .

  When the energization is interrupted when the cell temperature exceeds the set value, the process of regenerating the target cell is made safer by resuming energization after waiting for the cell temperature to fall below the predetermined restart temperature lower than the set value. You can continue.

  When the energization is finished and the regeneration process is completed, for example, after standing for a predetermined time of 1 hour or more, a capacity test is performed to confirm the success or failure of the regeneration process. When the cell temperature after standing for a predetermined time exceeds a predetermined specified value, the standing is continued as it is, or waiting for the cell temperature to fall below a specified value by forced cooling of air cooling, for example. In the capacity test, for example, when discharging to a predetermined end-of-discharge voltage with a constant discharge current of 0.2 C, if the capacity of 80% or more of the rated capacity is confirmed, the regeneration process is accepted. Prior to the capacity test, by measuring and recording the cell voltage and internal resistance of the target cell, it is possible to contribute to subsequent claims investigation and the like. Further, the cell temperature during the capacity test may also be measured and recorded.

Block diagram of playback processor Reproduction processing flowchart (1) Reproduction processing flowchart (2) Charging current waveform diagram Reproduction processing result data table (1) Reproduction processing result data table (2)

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  The regeneration processing method of the lithium ion battery is carried out by a regeneration processing apparatus including a microcomputer 11, a DC power source 12, and a transistor switch 13 as main components (FIG. 1).

  The output of the DC power source 12 is grounded via the transistor switch 13 and the target cell B of the lithium ion battery that is the target of the regeneration process. A control signal S from the microcomputer 11 is input to the transistor switch 13, and the transistor switch 13 can arbitrarily control the charging current Ic from the DC power source 12 for the target cell B according to the control signal S. . A current sensor 14 for detecting the charging current Ic is attached between the transistor switch 13 and the target cell B. However, the transistor switch 13 may be replaced with a semiconductor switch element other than the illustrated transistor element.

  In addition to the terminal voltage Vt of the target cell B, the microcomputer 11 receives the charging current Ic from the current sensor 14 and the cell temperature T from the temperature sensor 15. However, the temperature sensor 15 is, for example, a radiation thermometer, and can detect the upper surface temperature and / or the terminal temperature of the target cell B and output it as an electrical signal. Note that the temperature sensor 15 may output the highest temperature among them as the cell temperature T when detecting temperatures at a plurality of locations in the target cell B.

  The procedure of the lithium ion battery regeneration process is, for example, as shown in the flowchart of FIG. However, in the following description, the target cell B is a lithium ion battery cell WB-LYP40AHA (LiFePO4 positive electrode, rated capacity 40 Ah, rated voltage 3.4 V, charging voltage 4.0 V, discharge end voltage 2.8 V, manufactured by Winston Battery, China. ) Is a reproduction target.

  The lithium-ion battery to be regenerated is first subjected to an acceptance test for each cell (step (1) in FIG. 2, hereinafter simply referred to as (1)). That is, the lithium ion battery is checked for the presence or absence of mechanical damage such as cracking or cracking of the battery case, welding or breakage of the terminal, and the defective product is excluded from the object of the regeneration process.

  A lithium-ion battery that has undergone acceptance inspection measures cell voltage and internal resistance for each cell (2), and discharges the cell voltage to a discharge end voltage with a discharge current of 0.2 C, for example, when the cell voltage exceeds a specified discharge end voltage. (3), the process proceeds to the regeneration process (4). In the preliminary measurement in step (2), the discharge process in step (3) is omitted if the cell voltage is lower than the discharge end voltage.

  Details of the reproduction processing in step (4) will be described later. When the regeneration process is completed (4), after standing for a predetermined time of 1 hour or more (5), the cell voltage and the internal resistance are measured and recorded (6), and a capacity test is performed (7). However, in step (5), when the cell temperature T after a predetermined time elapses exceeds a specified value of 35 ° C., for example, the cell temperature T decreases to a specified value or less by natural cooling or forced cooling while standing still. wait. In the capacity test in step (7), for example, the battery is discharged to a discharge end voltage with a discharge current of 0.2 C, and a capacity of 80% or more of the rated capacity is confirmed to determine whether the regeneration process is acceptable. Thereafter, for example, constant current charging is performed at a charging current of 0.2 C for 6 hours, and a charging amount 1.2 times the rated capacity is finish-charged (8), thereby completing a series of processes.

  The reproduction process in step (4) of FIG. 2 is performed according to the program flowchart of FIG. 3, for example, by the reproduction processing apparatus of FIG.

  The program first controls the transistor switch 13 by the microcomputer 11 and starts energizing the charging current Ic from the DC power source 12 to the target cell B (step (1) in FIG. 3, hereinafter, simply (1)). ). The charging current Ic is obtained by superimposing the base current Ib = 0.05C = 2A and the pulse current Ip = 0.5C = 20A (FIG. 4), and charging period T1 = 5 minutes with a pause period T2 = 1 minute. The cycle is repeated. The pulse frequency of the pulse current Ip is 10 kHz, and the duty d is 30%. The horizontal axis in FIG. 4 is time t.

  Subsequently, the program confirms that the cell temperature T of the target cell B does not exceed the set value Ts (2), while the terminal voltage Vt of the target cell B being energized, that is, the charging voltage Vc is a predetermined set value. The energization is continued until Vs = 4.4V is reached (3) or the charge amount Q of the target cell B due to the charging current Ic reaches a predetermined value Qs = 1.2Qo = 48 Ah ((4), (2) (4)), the energization of the charging current Ic is terminated when the condition in any one of steps (3) and (4) is satisfied, and the regeneration process is completed (5). Here, Qo = 40Ah is the rated capacity of the target cell B.

  Note that the terminal voltage Vt of the target cell B being energized, that is, the charging voltage Vc, hardly changes with the progress of regeneration near the rated voltage 3.4 V of the target cell B, but suddenly when the target cell B approaches full charge. There is a tendency to rise. Therefore, the microcomputer 11 samples the terminal voltage Vt at a high frequency of, for example, every 1 second or less, and detects and measures the instantaneous value of the charging voltage Vc for the determination of step (3). Further, the charge amount Q used for the determination in step (4) is, for example, Q = (dIp + (1-d)) as the actual number N of energization cycles up to the present time of the charging period T1 and the suspension period T2 of the charging current Ic. Ib) T1 · N / 60Ah, and the number N of energization cycles can be counted by the microcomputer 11 based on the charging current Ic, for example.

  On the other hand, when the cell temperature T of the target cell B exceeds the set value Ts = 45 ° C. during the energization of the charging current Ic (2), the energization of the charging current Ic is interrupted (6), and the cell temperature T becomes the restart temperature Tr. Wait for the temperature to fall below 40 ° C. (7). When the cell temperature T ≦ Tr (7), the charging current Ic is resumed (1) and the regeneration process is continued ((1), (2), (3)... (2)).

  An example of the reproduction processing result data according to the flowcharts of FIGS. 2 and 3 is as shown in FIGS. In other words, the 12 target cells B (FIG. 5) that have deteriorated to a capacity of 0 Ah and are incapable of discharge in the pre-measurement of the regeneration process are well regenerated to a capacity regeneration rate of 99 to 105.5%. (Fig. 6).

  In the above description, the DC power supply 12 may control the output voltage together with the microcomputer 11 when the target cell B is energized with the charging current Ic including the predetermined base current Ib and the pulse current Ip. Further, the target cell B may be connected in series with a plurality of the same type and the same specification and start energizing the charging current Ic all at once. However, even in this case, the terminal voltage Vt and the cell temperature T of each target cell B are individually measured and monitored, so that each step other than step (1) in FIG. 3 and after step (5) in FIG. Each step is executed for each target cell B. The present invention can be applied to various lithium ion batteries whose positive electrodes are LiFePO4, LiCoO2, LiMn2 O4, LiNix Mny Co2 O2, LiNix Coy Al2 O2, and the like. The regeneration processing apparatus of FIG. 1 can use a general DC power supply 12 and can be applied to regeneration processing of a lead storage battery substantially as it is (see, for example, Japanese Patent No. 3723795).

  The present invention can be widely and suitably applied to lithium ion batteries for all uses including electric vehicles, electric tools, electric bicycles, and the like.

B ... Target cell Ic ... Charging current Ib ... Base current Ip ... Pulse current T1 ... Charging period T2 ... Suspension period T ... Cell temperature Ts ... Set value Tr ... Restart temperature Vc ... Charge voltage Vs ... Set value Q ... Charge amount Qs ... Predetermined value

Patent Applicant BRS Inc.

Claims (5)

When a deteriorated lithium-ion battery is regenerated for each cell, the target cell is energized by periodically repeating a charging period in which a DC base current and a square-wave pulse current are superimposed with a pause period in between. In addition, when the cell temperature of the target cell exceeds the set value, the energization is interrupted, and when the energization is interrupted, the energization is resumed after waiting for the cell temperature of the target cell to fall below a predetermined restart temperature lower than the set value, A method for regenerating a lithium ion battery, wherein energization is terminated when a charging voltage reaches a predetermined set value based on a rated charging voltage of the target cell or a charging amount of the target cell reaches a predetermined value. 2. A method for regenerating a lithium ion battery according to claim 1 , wherein the charging voltage is obtained by sampling the terminal voltage of the target cell being energized at a frequency of 1 second or less to detect an instantaneous value .   3. The method for regenerating a lithium ion battery according to claim 1, wherein after the energization is finished, a capacity test is performed after standing for a predetermined time. 4.   4. The lithium ion battery according to claim 3, wherein when the cell temperature exceeds a specified value after standing for a predetermined time, a capacity test is carried out after waiting for the cell temperature to fall below a specified value. Playback processing method.   5. The method for regenerating a lithium ion battery according to claim 4, wherein the target cell is forcibly cooled when waiting for a decrease in the cell temperature.

Images