JP4114237B2 - Control device for lithium-ion battery - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a lithium ion battery.
[0002]
[Prior art and its problems]
In a lithium ion battery using copper as a negative electrode current collector, when the cell is deactivated, copper is deposited from the negative electrode of the deactivated cell, and so-called dendrites are generated that extend to the positive electrode and short-circuit the positive and negative electrodes. At this time, depending on the state of copper deposition, the resistance of the dendrite may be large.
[0003]
Since the voltage across the deactivation cell drops to 0 V or near it, it is easy to detect the deactivation state of the cell, but one depletion battery from a battery pack in which many cells are connected in series. Maintenance work of exchanging active cells or short-circuiting both ends of the deactivated cells with jumpers is not easy.
[0004]
An object of the present invention is to completely short-circuit the deactivated cells in the assembled battery without complicated maintenance work.
[0005]
[Means for Solving the Problems]
(1) The invention of claim 1 is an assembled battery control device in which a plurality of lithium ion battery cells using copper as a negative electrode current collector are connected in series, and detects a deactivation state of the cell. Amplitude of repeated elution and precipitation of copper in the negative electrode current collector, and elution and precipitation reaction of copper in the negative electrode current collector follow the active detection means and the cell whose deactivation state is detected by the deactivation detection means. Voltage applying means for applying an AC voltage having a frequency .
(2) According to the lithium ion battery control device of the second aspect, the deactivation detection means determines that the deactivation state occurs when the terminal voltage of the cell becomes a predetermined value or less.
(3) The control device for a lithium ion battery according to claim 3 includes resistance detection means for detecting the internal resistance of the cell, the terminal voltage of the cell becomes a predetermined value or less by the deactivation detection means, and the internal resistance of the cell When the value exceeds a predetermined value, it is determined to be in an inactivated state.
[0006]
【The invention's effect】
(1) According to the present invention, for the set battery cell of the lithium ion battery using the copper anode current collector is connected to a plurality of series, it detects a deactivated state of the cell, loss Since an active voltage was detected, an AC voltage with a frequency at which the copper of the negative electrode current collector was repeatedly eluted and precipitated and a frequency at which the copper elution and precipitation reaction of the negative electrode current collector followed was applied. The generation of dendrites between the positive and negative electrodes of the deactivated cell is promoted, and the deactivated cell can be short-circuited without performing a short-circuiting operation using an external jumper.
(2) According to the invention of claim 2, when the terminal voltage of the cell becomes equal to or lower than a predetermined value, the cell is determined to be in an inactivated state, and an AC voltage is applied to the cell in which inactivation is detected. The same effect as the above effect 1 is obtained.
(3) According to the invention of claim 3, when the terminal voltage of the cell becomes equal to or lower than a predetermined value and the internal resistance of the cell exceeds the predetermined value, the cell is determined to be in an inactive state, and the cell in which the inactivation is detected is AC Since a voltage is applied, in addition to the above effect of claim 1, even when a cell has already been processed, if the processing result is insufficient and the generation of dendrite is not sufficient and the internal resistance is large, Processing is performed again, and the effect that the positive and negative electrodes of the deactivated cell can be completely short-circuited is obtained.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a basic cross-sectional structure of a lithium ion battery according to an embodiment.
The lithium ion battery 1 includes a positive electrode 2 and a negative electrode 3 and a separator 4 that separates them. In the positive electrode 2, an active material 2 b such as lithium cobaltate or lithium manganate is applied to a current collector 2 a such as aluminum. In the negative electrode 3, a coke-based or graphite-based carbon material is applied to a copper foil current collector 3a.
[0008]
FIG. 2 is a diagram showing a change in potential of the positive electrode and the negative electrode with respect to the amount of discharge electricity in the lithium ion battery, and is expressed with reference to the potential of lithium in the solution. In a lithium ion battery, the positive electrode potential decreases and the negative electrode potential increases as the amount of discharge electricity increases. Since the difference between the positive electrode potential and the negative electrode potential is the terminal voltage of the battery cell, the negative electrode potential mainly rises as the battery is discharged. As a result, the terminal voltage decreases and finally becomes 0v.
[0009]
When the battery cell is forcibly discharged by applying a reverse voltage or the like, the terminal voltage decreases. When the terminal voltage becomes about 0.8 V or less and the negative electrode potential becomes the copper elution potential (hatched area in the figure), the elution of copper from the negative electrode current collector 3a starts. In this state, when a forward voltage is applied to the battery cell to increase the terminal voltage, the negative electrode potential decreases, but the copper that has eluted in the solution does not return to its original state, but precipitates in the solution and dendrite grows. When this is repeated, the positive electrode 2 and the negative electrode 3 are short-circuited by the dendrite 5 as shown in FIG. 3, the number of dendrite 5 gradually increases, and finally the positive and negative electrodes are completely short-circuited.
[0010]
By utilizing this property of a lithium ion battery using copper as a negative electrode current collector, dendrites can be forcibly generated in a deactivated cell, and the positive electrode and negative electrode of the deactivated cell are short-circuited by a jumper. Even if maintenance work is not performed, the deactivated cell can be completely short-circuited.
[0011]
Therefore, in this embodiment, for a lithium ion battery using copper as a negative electrode current collector, cell deactivation is detected, and when a deactivation cell is detected, an AC voltage is applied to the battery, thereby negative electrode Promotes the elution and precipitation of copper from the current collector.
[0012]
FIG. 4 is a diagram showing the configuration of one embodiment.
The assembled battery 10 has n lithium ion battery cells using copper as a negative electrode current collector as shown in FIG. 1 connected in series. Voltage sensors V1 to Vn for detecting terminal voltages (hereinafter referred to as cell voltages) vcn (n = 1, 2,...) Are connected to the cells C1 to Cn. In addition, a current sensor I for detecting the charge / discharge current i is connected in series with the assembled battery 10. Further, both ends of each of the cells C1 to Cn are connected to the controller 11.
[0013]
The controller 11 incorporates a microcomputer and its peripheral components, an AC oscillator, an amplifier, and the like, detects the deactivation of each cell C1 to Cn, and applies an AC voltage to the deactivated cell to short-circuit it. .
[0014]
Here, the frequency of the alternating voltage applied to the deactivation cell should just be a frequency which copper elution and precipitation reaction follow, for example, shall be 10 kHz. Further, the amplitude of the AC voltage may be a voltage at which copper elution and precipitation occur as shown in FIG. Furthermore, the application of the AC voltage to the deactivated cell may be performed while the assembled battery 10 is paused, or may be performed in a superimposed manner during normal charging / discharging.
[0015]
The detection of the inactivated cell is determined to be inactivated when the cell voltage vcn falls below the determination reference value vo. Since a lithium ion battery is normally used in the range where the cell voltage VCn is 4.2 to 2.5 v, the determination reference value is set to 1 v, for example.
[0016]
Further, the cell internal resistance rcn is calculated from the cell voltage vcn detected by the voltage sensors V1 to Vn and the charge / discharge current i detected by the current sensor I (vcn / i), and the internal resistance rcn determines the determination reference value ro. If it exceeds, you may make it judge that it is a deactivated state.
[0017]
FIG. 5 is a flowchart showing the processing of the deactivated cell. The operation of the embodiment will be described with reference to this flowchart.
In step 1, it is confirmed whether or not the cell voltage vcn is equal to or lower than the reference value vo. If it is equal to or lower than the reference value vo, it is determined as an inactivated cell and the process proceeds to step 2. Otherwise, the process proceeds to step 5. When the deactivation of the cell Cn is detected, it is checked in step 2 whether or not the cell number n is stored in the memory, that is, whether or not the cell has already been processed. If the cell has been processed, the process proceeds to step 5, and if the cell has not been processed, the process proceeds to step 3.
[0018]
In step 3, an AC voltage is applied to both ends of the cell where deactivation is newly detected for a predetermined time. For example, when the deactivation of the cell C3 shown in FIG. 4 is newly detected, an AC voltage is output from the terminals T3 to T4 of the controller 11 and applied to both ends of the cell C3. Thereby, generation of dendrites between the positive and negative electrodes of the cell C3 is promoted, and the positive and negative electrodes are short-circuited. Next, in step 4, the number of the cell processed this time is stored in a memory, and in step 5, the cell number n is set as the next cell, the process returns to step 1, and the above process is repeated.
[0019]
In this way, the cell voltage is compared with the determination reference value to detect the inactivated state, and when the deactivated cell is detected, an AC voltage is applied to both ends of the cell. The generation of dendrites is promoted, and the deactivated cell can be short-circuited without performing a short-circuiting operation with an external jumper.
[0020]
FIG. 6 is a flowchart showing a modified example of the processing of the deactivated cell. In this modification, the cell deactivation is detected by the cell voltage vcn and the internal resistance rcn.
In step 11, it is confirmed whether or not the cell voltage vcn is equal to or lower than the reference value vo. If it is equal to or lower than the reference value vo, it is determined as an inactivated cell, and the process proceeds to step 12;
[0021]
In step 12, the internal resistance rcn of the deactivated cell Cn is calculated from the cell voltage vcn of the deactivated cell Cn and the charge / discharge current i of the assembled battery 10, and whether or not the internal resistance rcn exceeds the reference value ro. judge. If the internal resistance rcn exceeds the reference value ro, the process proceeds to step 13;
[0022]
In step 13, an alternating voltage is applied to both ends of the cell where deactivation is detected for a predetermined time. In the following step 14, the cell number n is set to the next cell, the process returns to step 11 and the above processing is repeated.
[0023]
According to this modification, since the AC voltage is applied to the cell whose cell voltage is equal to or lower than the deactivation determination reference value and the internal resistance exceeds the reference value, the cell already processed is processed. However, if the treatment result is insufficient and the generation of dendrite is not sufficient and the internal resistance is high, the treatment is performed again, and the positive and negative electrodes of the deactivated cell can be completely short-circuited.
[0024]
In the configuration of the above embodiment, the voltage sensors V1 to Vn, the current sensor I, and the controller 11 constitute deactivation detection means and resistance detection means, and the controller 11 constitutes voltage application means.
[0025]
In addition, this invention is applied to the lithium ion battery which uses copper for a negative electrode collector, and positive electrode collectors other than a negative electrode collector, a positive electrode active material, a negative electrode active material, and the material of a separator are not specifically limited.
[Brief description of the drawings]
FIG. 1 is a diagram showing a basic cross-sectional structure of a lithium ion battery according to an embodiment.
FIG. 2 is a diagram showing a change in potential of a positive electrode and a negative electrode with respect to the amount of discharge electricity in a lithium ion battery.
FIG. 3 is a diagram showing a dendrite generation state of a lithium ion battery.
FIG. 4 is a diagram showing a configuration of an embodiment.
FIG. 5 is a flowchart showing inactive cell processing according to an embodiment;
FIG. 6 is a flowchart showing a modified example of the deactivated cell process.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Lithium ion battery 2 Positive electrode 2a Positive electrode collector 2b Positive electrode active material 3 Negative electrode 3a Negative electrode collector 3b Negative electrode active material 4 Separator 5 Dendrite 10 Battery assembly 11 Controller V1-Vn Voltage sensor I Current sensor

Claims (3)

A control device for an assembled battery in which a plurality of lithium ion battery cells using copper as a negative electrode current collector are connected in series,
Deactivation detection means for detecting the deactivation state of the cell,
For the cell in which the deactivation state is detected by the deactivation detection means, the amplitude at which copper of the negative electrode current collector repeats elution and precipitation, and the frequency at which the elution and precipitation reaction of copper of the negative electrode current collector follow. A control device for a lithium ion battery, comprising: voltage applying means for applying an alternating voltage. In the control apparatus of the lithium ion battery according to claim 1,
The deactivation detecting means determines that the deactivation state is reached when the terminal voltage of the cell becomes a predetermined value or less. In the control apparatus of the lithium ion battery according to claim 1,
Comprising resistance detection means for detecting the internal resistance of the cell;
The deactivation detecting unit determines that the deactivation state is present when the terminal voltage of the cell becomes equal to or lower than a predetermined value and the internal resistance of the cell exceeds a predetermined value.

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