KR20240082760A - Apparatus and method for charging and discharging battery cells - Google Patents

Abstract

The battery cell charging and discharging device and charging and discharging method according to the present invention apply specific abnormal behavior judgment criteria for each type of battery cell according to the type of positive electrode active material contained in the battery cell, and determine the abnormal behavior of the battery cell. It is configured to determine, so that the charging and discharging operation is not interrupted unnecessarily during charging and discharging, which has the effect of improving the productivity and quality deterioration of the battery cell.

Description

Battery cell charging and discharging device and charging and discharging method {Apparatus and method for charging and discharging battery cells}

The present invention relates to a device and a charging and discharging method for charging and discharging a plurality of battery cells, and more specifically, to lithium iron phosphate batteries and other batteries that exhibit different voltage behavior during charging and discharging, and to a method for charging and discharging a plurality of battery cells. This relates to a device and method that can charge and discharge various types of batteries by applying behavior judgment standards.

Recently, as the demand for portable electronic products such as laptops, video cameras, and portable phones has rapidly increased, and as the development of electric vehicles, energy storage batteries, robots, and satellites has begun, high-performance secondary batteries capable of repeated charging and discharging have been developed. Research on this is actively underway.

Currently commercialized secondary batteries include nickel cadmium batteries, nickel hydrogen batteries, nickel zinc batteries, and lithium secondary batteries. Among these, lithium secondary batteries have little memory effect compared to nickel-based secondary batteries, so they can be freely charged and discharged. It is receiving attention for its extremely low self-discharge rate and high energy density. In general, these secondary batteries can be divided into cylindrical or square can-type secondary batteries and pouch-type secondary batteries depending on the exterior material or application type.

Generally, secondary batteries are manufactured through a cell assembly process and a cell activation process. Since cells are assembled in a discharged state, they must be activated through primary charging after assembly to function as a battery. This is called the activation process or formation process.

In the activation process, a number of secondary batteries are mounted on a charging and discharging device, and processes such as charging and discharging are performed under the conditions necessary for activation. Due to the nature of secondary batteries, this activation process must be preceded in order to activate the positive electrode active material and create a stable surface film (SEI, Solid Electrolyte Interface) on the negative electrode during the first cycle. During the activation process, SEI is first formed on the surface of the anode due to the reaction between the anode active material and the electrolyte, and the physical and mechanical soundness of this SEI determines the performance of the secondary battery until the life of the secondary battery ends.

Meanwhile, when secondary batteries are charged and discharged during the activation process, various information about product performance can be obtained. For example, a secondary battery charging and discharging device is configured to determine the quality of the product by measuring the capacity, voltage, and current of the secondary battery during charging and discharging. Specifically, the voltage of the secondary battery is measured at a specific point in time, and the quality is determined by determining whether the measurement result deviates from the voltage behavior of a pre-entered good product. And if it is determined to be defective, the charging and discharging operation is set to stop in preparation for the risk of fire or explosion.

Meanwhile, the voltage behavior of secondary batteries varies depending on the type of positive electrode active material included in the secondary battery. For example, the voltage behavior of a secondary battery in which the positive electrode active material is lithium iron phosphate and a secondary battery in which the positive active material is lithium nickel cobalt manganese composite oxide appear different from each other.

However, to date, only a standard for determining good quality of a secondary battery using one type of positive electrode active material is input into one charging/discharging device. Therefore, if two types of secondary batteries with different types of positive electrode active materials are judged to be good quality using this charging and discharging device, the standard for judging good quality for different types of secondary batteries can be applied, so that the battery can be charged or discharged even though it is not actually defective. There may be cases where charging and discharging operations continue to stop. This has a negative impact on production rate and product quality.

Republic of Korea Patent Publication No. 10-2019-0100500

The present invention presents specific abnormal behavior judgment criteria for each type of battery cell according to the type of positive electrode active material contained in the battery cell in the abnormal behavior judgment criteria input to the charging and discharging device, thereby providing a single charging and discharging device. The goal is to provide a technology that can determine abnormal behavior of each type of battery cell.

A battery cell charging and discharging device according to the present invention is a charging and discharging device for charging and discharging a plurality of battery cells, and includes a sensing unit configured to measure the voltage of a battery cell mounted on the charging and discharging device; a memory unit configured to generate a battery cell charge/discharge profile that is a time-voltage graph of a battery cell to be charged and discharged, and to store the generated battery cell charge/discharge profile and a standard charge/discharge profile that is a time-voltage graph of a good battery cell; A control unit configured to compare and analyze the battery cell charge/discharge profile with the standard charge/discharge profile, determine whether the battery cell behaves abnormally, and transmit a control signal to stop charging/discharging for the battery cell determined to behave abnormally. The control unit determines abnormal behavior if condition 1 is satisfied when (i) the positive electrode active material contained in the battery cell is lithium iron phosphate, and (ii) the positive electrode active material contained in the battery cell is not lithium iron phosphate. , if any one or more of Condition 2 and Condition 3 are satisfied, it may be configured to determine abnormal behavior.

[Condition 1]

In the voltage section where the voltage of the battery cell is 3.4V or higher, the difference between the voltage of the battery cell and the voltage of the non-defective battery cell exceeds 60mV.

[Condition 2]

The difference between the voltage of the battery cell and the voltage of a good battery cell exceeds 20mV.

[Condition 3]

In the charge/discharge profile of a battery cell, there is a section where the voltage decreases as time increases.

In one embodiment of the present invention, when the positive electrode active material included in the battery cell is lithium iron phosphate, the control unit controls the battery cell even if there is a section in the charge/discharge profile of the battery cell where the voltage decreases with an increase in time. It may be configured to determine normal.

A charging/discharging device according to an embodiment of the present invention includes a charging/discharging unit electrically connected to a plurality of battery cells and configured to apply current; And it may further include an input unit for inputting the type of positive electrode active material included in the battery cell to be charged and discharged.

In one embodiment of the present invention, the standard charge/discharge profile may be a graph that measures the voltage of good battery cells for each time period for a sample group composed of good battery cells, and corresponds to the average voltage value of the sample group for each time period. .

In one embodiment of the present invention, the control unit matches the charge/discharge profile of the battery cell generated by the memory unit with the charge/discharge profile of the non-defective battery cell to determine the voltage of the battery cell and the voltage of the non-defective battery cell. It can be configured to calculate the difference.

In one embodiment of the present invention, the sensing unit may be configured to measure the voltage of the battery cell while the battery cell is being charged or discharged.

The charging and discharging device according to an embodiment of the present invention may further include a temperature sensor that measures the temperature of the battery cell, wherein the control unit determines the temperature of the battery cell measured by the temperature sensor and the standard charge. If there is a temperature difference when measuring the voltage for generating a discharge profile, it may be configured to correct the voltage difference according to the temperature difference.

In one embodiment of the present invention, the charge/discharge unit is configured to charge/discharge the battery cell under the same charge/discharge conditions as the charge/discharge conditions for a good battery cell when collecting voltage data for acquiring the standard charge/discharge profile. It can be.

The charging and discharging method of a battery cell according to an embodiment of the present invention is (S1) charging or discharging a good quality battery cell, measuring the voltage of the good quality battery cell for each time period, and measuring the standard charge, which is a time-voltage graph of the good quality battery cell. Process of recording discharge profile; (S2) A process of measuring the voltage of the battery cell to be charged and discharged over time while charging or discharging the battery cell to be charged and discharged, and recording a battery cell charge and discharge profile, which is a time-voltage graph of the battery cell to be charged and discharged; (S3) comparing and analyzing the standard charge/discharge profile and the battery cell charge/discharge profile to determine whether the battery cell is behaving abnormally; and (S4) a process of stopping charging and discharging of a battery cell determined to exhibit abnormal behavior. The process (S3) may include (i) when the positive electrode active material contained in the battery cell is lithium iron phosphate, condition 1 If is satisfied, abnormal behavior can be determined. (ii) If the positive electrode active material included in the battery cell is not lithium iron phosphate, abnormal behavior can be determined if any one or more of Conditions 2 and 3 are satisfied.

[Condition 1]

In the voltage section where the voltage of the battery cell is 3.4V or higher, the difference between the voltage of the battery cell and the voltage of the non-defective battery cell exceeds 60mV.

[Condition 2]

The difference between the voltage of the battery cell and the voltage of a good battery cell exceeds 20mV.

[Condition 3]

In the charge/discharge profile of a battery cell, there is a section where the voltage decreases as time increases.

In one embodiment of the present invention, the lithium iron phosphate may be a compound of formula 1 below.

[Formula 1]

Li _1+a Fe _1-x M _x (PO _4-b )X _b

(In Formula 1, M is any one or two or more elements selected from the group consisting of Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn and Y. and, x≤0.5)

In one embodiment of the present invention, the positive electrode active material other than the lithium iron phosphate may be a compound of the following formula (2).

[Formula 2]

LiNi _c Co _d M n _e M _f O ₂

(In Formula 2, M is at least one selected from the group consisting of Al, Ti, Mg, Zr, Y, Sr, and B, 0<c≤0.8, 0<d≤0.35, 0<e≤0.35 , 0≤f≤0.1)

In one embodiment of the present invention, in the process (S3), when the positive electrode active material included in the battery cell is lithium iron phosphate, even if there is a section in the charge/discharge profile of the battery cell where the voltage decreases with increasing time, The battery cell can be determined to be normal.

In one embodiment of the present invention, the (S3) process matches the charge/discharge profile of the battery cell with the charge/discharge profile of the non-defective battery cell to determine the difference between the voltage of the battery cell and the voltage of the non-defective battery cell. It may include a process of calculating .

In one embodiment of the present invention, the (S2) process includes measuring the temperature of a battery cell during charging and discharging; And when there is a difference between the measured temperature and the temperature in the process (S1), it may include a process of correcting the voltage difference according to the temperature difference in the charge/discharge profile of the battery cell.

The battery cell charging and discharging device according to the present invention is configured to determine abnormal behavior of the battery cell by applying specific abnormal behavior determination criteria for each type of battery cell according to the type of positive electrode active material contained in the battery cell, Accordingly, the charging and discharging operation is not interrupted unnecessarily during charging and discharging, which has the effect of improving the productivity and quality deterioration of battery cells.

Figure 1 is a graph showing the corresponding relationship between depth of charge (SOC; State of Charge) and voltage of a lithium iron phosphate battery and an NCM-based composite oxide battery.
FIG. 2 is a diagram showing a standard charge/discharge profile and a charge/discharge profile of the battery cell generated according to an embodiment of the present invention for a battery cell in which the positive electrode active material is lithium iron phosphate.
FIG. 3 is a graph corresponding to the voltage difference (dV) between the standard charge/discharge profile shown in FIG. 2 and the charge/discharge profile of the battery cell over time.
Figure 4 is a standard charge/discharge profile of an NCM-based composite oxide battery according to an embodiment of the present invention.
Figure 5 is a graph corresponding to the standard charge/discharge profile of a battery containing NCM-based composite oxide as a positive electrode active material and the voltage difference (dV) between the charge/discharge profile of the battery cell over time.
Figure 6 is a schematic diagram of a charging and discharging device according to an embodiment of the present invention.
Figure 7 is a flowchart of a method of charging and discharging a battery cell according to another embodiment of the present invention.
Figure 8 is a flowchart showing a process for determining whether a battery cell is behaving abnormally according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, terms or words used in this specification and claims should not be construed as limited to their usual or dictionary meanings, and the inventor should appropriately use the concept of terms to explain his or her invention in the best way. It should be interpreted as meaning and concept consistent with the technical idea of the present invention based on the principle of definability.

Therefore, the embodiments described in this specification and the configurations shown in the drawings are only one of the most preferred embodiments of the present invention and do not represent the entire technical idea of the present invention, and therefore, at the time of filing the present application, various options that can replace them are available. It should be understood that equivalents and variations may exist.

Throughout the specification, when it is said that a part “includes” a certain element, this does not mean that other elements are excluded, but that it may further include other elements, unless specifically stated to the contrary. Additionally, terms such as <control unit> used in the specification refer to a unit that processes at least one function or operation, and may be implemented as hardware, software, or a combination of hardware and software.

Additionally, throughout the specification, when a part is said to be "connected" to another part, this refers not only to the case where it is "directly connected" but also to the case where it is "indirectly connected" with another element in between. Includes.

In addition, in the specification, “the difference between the voltage of a battery cell and the voltage of a non-defective battery cell” described in [Condition 1] and [Condition 2] means the absolute value of the value obtained by subtracting the voltage of the non-defective battery cell from the voltage of the battery cell. do.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings.

<First embodiment>

The first embodiment relates to a charging and discharging device for charging and discharging a plurality of battery cells.

Figure 1 is a graph showing the corresponding relationship between depth of charge (SOC; State of Charge) and voltage of a lithium iron phosphate battery and an NCM-based composite oxide battery. Referring to Figure 1, in a secondary battery in which the positive electrode active material is an NCM-based composite oxide (lithium nickel cobalt manganese composite oxide), as the depth of charge increases, the voltage of the battery increases correspondingly, and the slope of the graph is constant or the slope changes. It shows a small graph reformation.

On the other hand, secondary batteries in which the positive electrode active material is lithium iron phosphate have a different graph shape than NCM-based composite oxide batteries. Specifically, in the case of lithium iron phosphate batteries, in the voltage range of about 3.2V to 3.4V, the voltage change rate with increase in charging depth is 0 or has a plateau range close to 0, but NCM-based composite oxide batteries In the case of , there is no such plateau interval.

Therefore, when activating charge and discharge of lithium iron phosphate batteries and selecting abnormal behavior batteries using a charge/discharge device in which only the abnormal voltage behavior selection criteria applied to NCM-based composite oxide batteries are input, the voltage range of 3.2V to 3.4V In fact, it is not an abnormal behavior, but the charging and discharging device determines it to be an abnormal behavior and stops charging and discharging.

As such, NCM-based composite oxide batteries and lithium iron phosphate batteries exhibit different voltage behavior, so when selecting battery cells showing abnormal voltage behavior, the criteria for selecting each abnormal voltage behavior according to the type of positive electrode active material of the battery are used. must be applied.

The battery cell charging and discharging device according to the present invention is configured to determine abnormal behavior of the battery cell by applying specific abnormal behavior determination criteria for each type of battery cell according to the type of positive electrode active material contained in the battery cell, Accordingly, the charging and discharging operation is not interrupted unnecessarily during charging and discharging, which has the effect of improving the productivity and quality deterioration of battery cells.

Figure 6 is a schematic diagram of a charging and discharging device according to an embodiment of the present invention. Referring to FIG. 6, the charging and discharging device 100 according to an embodiment of the present invention includes a sensing unit 110, a memory unit 120, a control unit 130, a charging and discharging unit 140, and an input unit 150. It can be included.

The battery cell charge/discharge device 100 according to the present invention is a device for activating charge/discharge of a plurality of battery cells (B), and may be an existing charger/discharge device.

The sensing unit 110 is configured to measure the voltage at both ends of each battery cell (B) in real time while the plurality of battery cells (B) mounted on the charging and discharging device 100 are being charged or discharged. It is done. The sensing unit 110 may be configured to transmit measured voltage data to the memory unit 120.

The sensing unit 110 may be configured to measure the voltage of the battery cell (B) at regular time intervals while the battery cell (B) is being charged or discharged, and the time interval is specifically 1 second to 1 second. It may be a regular time interval set in the range of 20 minutes, 1 second to 10 minutes, 5 seconds to 30 minutes, or 10 seconds to 10 minutes.

The memory unit 120 generates a battery cell charge/discharge profile that is a time-voltage graph of the battery cell (B) to be charged/discharged, and generates a standard charge/discharge profile that is a time-voltage graph of the generated battery cell charge/discharge profile and a good battery cell. Can be configured to store profiles.

The memory unit 120 is configured to receive voltage data of the battery cell (B) measured during charging or discharging from the sensing unit 110, generate a graph corresponding to the voltage by time period, and record it. Accordingly, for each battery cell (B) subject to charging and discharging, a time-voltage graph in which the voltage history over time is recorded is generated, and in this specification, this is referred to as the charging and discharging profile of the battery cell.

Additionally, the memory unit 120 also stores voltage data of good quality battery cells measured while charging or discharging the good quality battery cells. The voltage data of the non-defective battery cell may be a time-voltage graph that corresponds to the voltage measured over time while charging or discharging the non-defective battery cell. In this specification, this is referred to as the standard charge/discharge profile of the non-defective battery cell. I decided to do it.

In one specific example, the standard charge/discharge profile may be a graph in which the voltage of a sample group composed of non-defective battery cells is measured for each time period, and the average voltage value of the sample group is corresponded for each time period.

The sample group may consist of 100 to 100,000 good battery cells, and the sensing unit 110, which constitutes the charging and discharging device of the present invention, activates charging for each good battery cell making up this sample group. During discharge, the voltage of each good battery cell can be measured over time.

The memory unit 120 can generate a time-voltage graph for each good battery cell based on the voltage measurement result by the sensing unit 110, and the time-voltage graph for each good battery cell generated in this way is, There may be some differences between them. In order to integrate the time-voltage graphs of good battery cells generated as many as the number of sample groups into one standard charge/discharge profile, the memory unit 120 calculates the average value of the voltage measurement values for each time period and calculates the average voltage value for each time period. It can be configured to generate the corresponding graph as a standard charge/discharge profile and record it.

FIG. 2 is a diagram showing a standard charge/discharge profile and a charge/discharge profile of the battery cell generated according to an embodiment of the present invention for a battery cell in which the positive electrode active material is lithium iron phosphate, and FIG. 4 is a view showing a charge/discharge profile of the battery cell according to an embodiment of the present invention. This is the standard charge/discharge profile of the NCM-based composite oxide battery.

Referring to Figure 2, the standard charge/discharge profile of a lithium iron phosphate battery has a portion (B) in which the voltage slightly decreases over time or there is little change in voltage within the voltage range of 3.2V to 3.4V. In the voltage section above 3.4V, there is a part (A) where the amount of change in voltage over time increases compared to before.

Referring to Figure 4, the standard charge/discharge profile of the NCM-based composite oxide battery has a graph shape close to a linear function (straight line), and the voltage slightly decreases over time or there is almost no change in voltage. It does not contain any part.

The memory unit 120 transmits the standard charge/discharge profile generated as above to the control unit 130, allowing the control unit 130 to compare and analyze the charge/discharge profile of the battery cell and the standard charge/discharge profile to detect abnormalities in the battery cell. Voltage behavior can be determined.

The control unit 130 receives the charge/discharge profile and the standard charge/discharge profile of the battery cell subject to charge/discharge from the memory unit 120, compares and analyzes the charge/discharge profile of the battery cell with the standard charge/discharge profile, and It may be configured to determine whether the cell is behaving abnormally and to transmit a control signal to stop charging and discharging the battery cell determined to be behaving abnormally.

At this time, the control unit 130 determines abnormal behavior if (i) condition 1 is satisfied when the positive electrode active material contained in the battery cell is lithium iron phosphate, and (ii) the positive electrode active material contained in the battery cell is not lithium iron phosphate. In this case, if one or more of Condition 2 and Condition 3 are satisfied, it may be configured to determine abnormal behavior.

[Condition 1]

In the voltage section where the voltage of the battery cell is 3.4V or higher, the difference between the voltage of the battery cell and the voltage of the non-defective battery cell exceeds 60mV.

[Condition 2]

The difference between the voltage of the battery cell and the voltage of a good battery cell exceeds 20mV.

[Condition 3]

In the charge/discharge profile of a battery cell, there is a section where the voltage decreases.

In addition, when the positive electrode active material included in the battery cell is lithium iron phosphate, the control unit 130 controls the battery cell even if the graph of the charge/discharge profile of the battery cell sometimes decreases in the voltage section where the voltage of the battery cell is less than 3.4 V. It may be configured to determine that the cell is normal.

FIG. 3 is a graph corresponding to the voltage difference (dV) between the standard charge/discharge profile shown in FIG. 2 and the charge/discharge profile of the battery cell over time. Specifically, the standard charge/discharge profile is a time-voltage graph of a sample group consisting of a large quantity of good quality battery cells, and the charge/discharge profile of a battery cell is a time-voltage graph of battery cells classified as good quality products. Referring to these drawings, when the positive electrode active material included in the battery cell is lithium iron phosphate, the deviation, which is the voltage difference (dV) between the standard charge and discharge profile and the charge and discharge profile of the battery cell, ranges from 1 second to about 8000 seconds. It is close to 0 in the section, and gradually increases in the subsequent time section, reaching a maximum of about 60 mV around 9729 seconds. And, it can be seen that the voltage section corresponding to the time when the maximum deviation appears is a voltage section of 3.4V or more.

Accordingly, the control unit 130 of the present invention, when the battery cell to be charged and discharged is a lithium iron phosphate battery containing lithium iron phosphate as a positive electrode active material, if the charge and discharge profile of the battery cell satisfies condition 1 above, the above It is configured to judge based on behavior.

Additionally, referring to FIG. 2, when the battery cell is a lithium iron phosphate battery, it includes a portion showing a behavior in which voltage decreases as time increases in a time period of 1 second to 422 seconds. Accordingly, the control unit 130 of the present invention may be configured to determine that the battery cell is normal even if there is a section in the charge/discharge profile of the battery cell where the voltage decreases as time increases.

Meanwhile, the control unit 130 of the present invention is configured to apply a different determination standard from the above to a battery cell containing a positive electrode active material other than lithium iron phosphate.

Figure 5 is a graph corresponding to the voltage difference (dV) between the standard charge/discharge profile of a battery containing NCM-based composite oxide as a positive electrode active material and the charge/discharge profile of the battery cell over time. Referring to FIG. 5, when the positive electrode active material included in the battery cell is an NCM-based composite oxide rather than lithium iron phosphate, the deviation, which is the voltage difference (dV) between the standard charge and discharge profile and the charge and discharge profile of a good battery cell, is the time Even after this has passed, it is very close to 0.

Accordingly, the control unit 130 of the present invention is configured to determine abnormal behavior if the charge and discharge profile of the battery cell satisfies condition 2 above when the positive electrode active material included in the battery cell to be charged and discharged is not lithium iron phosphate. there is.

Also, referring to FIG. 4, the standard charge/discharge profile of the NCM-based composite oxide battery does not include a section in which the voltage decreases with time. Accordingly, the control unit 130 of the present invention is configured to determine that a battery cell in which a section in which the voltage decreases exists in the charge/discharge profile of the battery cell as abnormal behavior when the positive electrode active material included in the battery cell is not lithium iron phosphate. there is.

The control unit 130 of the present invention compares and analyzes the charge/discharge profile of the battery cell and the standard charge/discharge profile, and determines whether condition 1 or condition 2 is satisfied by charging and discharging the battery cell generated by the memory unit. It may be configured to calculate the difference between the voltage of the battery cell and the voltage of the non-defective battery cell by matching the profile with the charge/discharge profile of the non-defective battery cell.

The charge/discharge unit 140 may be configured to be electrically connected to each of the plurality of battery cells (B) accommodated in the charge/discharge device 100 and apply current to charge and discharge the battery cells. The charging/discharging unit 140 may be provided with a charging circuit and a discharging circuit.

The charging circuit supplies power to charge the battery cell in the charging mode, and the charging circuit may be configured to start and stop operation by a control signal from the control unit 130. Additionally, to enable CC-CV (constant current-constant voltage) charging, the charging circuit may include a constant current circuit and a constant voltage circuit.

The discharge circuit functions to discharge the battery cell in a discharge mode. The discharge circuit may also be configured to start and stop operation by a control signal from the control unit 130.

In one embodiment of the present invention, the charge/discharge unit 140 charges and discharges the battery cell under the same charge/discharge conditions as the charge/discharge conditions for a good battery cell when collecting voltage data for acquiring the standard charge/discharge profile. It can be configured to do so.

For example, when measuring the voltage while charging or discharging a good battery cell to obtain a standard charge/discharge profile, if the charging or discharging method was CC charging or CC discharging, the charging or discharging of the battery cell is also as above. Likewise, it can be CC charging or CC discharging, and if the charging or discharging rate (C-rate) is 0.5C, the charging or discharging rate of the battery cell can also be 0.5C.

Since the charge/discharge profile is affected by changes in charge/discharge conditions, the charge/discharge conditions for acquiring the standard charge/discharge profile and the charge/discharge conditions for acquiring the charge/discharge profile of the battery cell must be the same to enable charge/discharge of the battery cell. From the profile, the influence of differences in charging and discharging conditions can be excluded.

The input unit 150 may be configured to input the type of positive electrode active material included in the battery cell to be charged and discharged, and to transmit the input information to the control unit 130. The input unit causes the control unit 130 to determine whether abnormal behavior occurs according to condition 1 above when the positive electrode active material included in the battery cell subject to charging and discharging is lithium iron phosphate, and when the positive electrode active material is not lithium iron phosphate, the above condition is determined. Determine whether abnormal behavior exists based on one or more of conditions 2 or 3.

The charging and discharging device 100 according to an embodiment of the present invention may further include a temperature sensor (not shown) that measures the temperature of the battery cell. Even for the same battery cell, the charge/discharge profile of the battery cell may vary depending on the difference in temperature conditions for measuring the voltage of the battery cell.

Accordingly, in the charging and discharging device 100 according to an embodiment of the present invention, the control unit 130 controls the temperature of the battery cell measured by the temperature sensor and the temperature when measuring the voltage for generating the standard charging and discharging profile. If there is a difference, it may be configured to correct the voltage difference due to the temperature difference.

For example, if the voltage measurement temperature of a battery cell subject to charging and discharging is 25°C, but when measuring the voltage of a good battery cell to generate a standard charging and discharging profile, the temperature is 23°C, the control unit of the present invention measures 2°C. It is configured to correct the voltage difference according to the temperature difference. In this way, through voltage correction according to the temperature difference when measuring voltage, the interference effect due to the temperature difference can be excluded when comparing the charge/discharge profile of the battery cell and the standard charge/discharge profile.

<Second Embodiment>

The second embodiment relates to a method of charging and discharging a battery cell for charging and discharging a plurality of battery cells.

FIG. 7 is a flowchart of a method of charging and discharging a battery cell according to another embodiment of the present invention, and FIG. 8 is a flowchart showing a process of determining whether a battery cell is behaving abnormally according to an embodiment of the present invention.

Referring to these drawings, the method of charging and discharging a battery cell according to the present invention is (S1) measuring the voltage of a good battery cell over time while charging or discharging a good battery cell, and producing a time-voltage graph of the good battery cell. Process of recording a standard charge/discharge profile; (S2) A process of measuring the voltage of the battery cell to be charged and discharged over time while charging or discharging the battery cell to be charged and discharged, and recording a battery cell charge and discharge profile, which is a time-voltage graph of the battery cell to be charged and discharged; (S3) comparing and analyzing the standard charge/discharge profile and the battery cell charge/discharge profile to determine whether the battery cell is behaving abnormally; and (S4) stopping charging and discharging of battery cells determined to exhibit abnormal behavior, wherein the (S3) process satisfies condition 1 when (i) the positive electrode active material included in the battery cell is lithium iron phosphate. (ii) If the positive electrode active material included in the battery cell is not lithium iron phosphate, it can be determined as abnormal behavior if at least one of Condition 2 and Condition 3 is satisfied.

[Condition 1]

In the voltage section where the voltage of the battery cell is 3.4V or higher, the difference between the voltage of the battery cell and the voltage of the non-defective battery cell exceeds 60mV.

[Condition 2]

The difference between the voltage of the battery cell and the voltage of a good battery cell exceeds 20mV.

[Condition 3]

In the charge/discharge profile of a battery cell, there is a section where the voltage decreases as time increases.

As described above, the method of charging and discharging a battery cell according to the present invention is (i) when the positive electrode active material contained in the battery cell is lithium iron phosphate, determines whether the battery cell behaves abnormally according to Condition 1, and (ii) determines whether the battery cell behaves abnormally. If the positive electrode active material included is not lithium iron phosphate, it is determined whether the battery cell is behaving abnormally according to one or more of Condition 2 or Condition 3.

In the charge/discharge method according to an embodiment of the present invention, in the (S3) process, when the positive electrode active material included in the battery cell is lithium iron phosphate, the voltage decreases with time in the charge/discharge profile of the battery cell. Even if a section exists, the corresponding battery cell can be determined to be normal.

The (S1) process is a process for acquiring a standard charge/discharge profile. During charging or discharging of a good battery cell, the voltage of a good battery cell is measured for each time period, and a time-voltage graph corresponding to the voltage measurement value for each time period is created. It includes the process of generating and recording this as a standard charge/discharge profile.

Through the above (S1) process, the standard charge/discharge profile shown in each of FIGS. 2 and 4 can be obtained.

In one specific example, the standard charge/discharge profile may be a graph in which the voltage of a sample group composed of non-defective battery cells is measured for each time period, and the average voltage value of the sample group is corresponded for each time period.

The sample group may be composed of 100 to 100,000 non-defective battery cells, and the time-voltage graphs of each non-defective battery cell constituting the sample group may have slight deviations from each other. In order to integrate the time-voltage graphs of good battery cells generated as many as the number of sample groups into one standard charge/discharge profile, the (S1) process calculates the average value of the voltage measurements for each time period, and calculates the average voltage value for each time period. It may include the process of generating a corresponding graph as a standard charge/discharge profile and recording it.

The (S2) process is a process of collecting voltage behavior data of each battery cell while charging and discharging a plurality of battery cells according to the present invention. While charging or discharging the battery cell to be charged and discharged, the voltage of the battery cell is measured in real time. It may include the process of measuring, generating and recording a charge/discharge profile of the battery cell, which is a graph that corresponds to the voltage measurements over time.

In one specific example, the charging and discharging conditions in the process (S2) may be set to be the same as the charging and discharging conditions of a good battery cell in the process (S1).

In one specific example, the (S2) process includes measuring the temperature of a battery cell during charging and discharging; And when there is a difference between the measured temperature and the temperature in the process (S1), a process of correcting the voltage difference according to the temperature difference in the charge/discharge profile of the battery cell may be further included.

The process (S3) is a process of selecting battery cells that exhibit abnormal voltage behavior by applying appropriate abnormal behavior determination conditions according to the type of positive electrode active material included in the battery cell.

In the charging and discharging method according to an embodiment of the present invention, the lithium iron phosphate may be a compound of the following formula (1).

[Formula 1]

Li _1+a Fe _1-x M _x (PO _4-b )X _b

(In Formula 1, M is any one or two or more elements selected from the group consisting of Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn and Y. and, x≤0.5)

For example, the lithium iron phosphate may be LiFePO ₄ .

In addition, the positive electrode active material other than the lithium iron phosphate may be an NCM-based complex oxide, and specifically, may be a compound of the following formula (2).

[Formula 2]

LiNi _c Co _d M n _e M _f O ₂

(In Formula 2, M is at least one selected from the group consisting of Al, Ti, Mg, Zr, Y, Sr, and B, 0<c≤0.8, 0<d≤0.35, 0<e≤0.35 , 0≤f≤0.1)

In one specific example, the process (S3) includes a charge/discharge profile of the battery cell to determine whether the charge/discharge profile of the battery cell satisfies the abnormal behavior determination criteria according to Condition 1 or Condition 2, and A process of matching the charge/discharge profile of a non-defective battery cell and calculating the difference between the voltage of the battery cell and the voltage of the non-defective battery cell may be further included.

The process (S4) is a process of stopping charging and discharging of the battery cell determined to have abnormal behavior in the process (S3). As the charging and discharging of a battery cell determined to exhibit abnormal behavior is stopped, the risk of explosion or fire that may be caused by continuously charging or discharging a defective battery can be prevented.

The method of charging and discharging a battery cell according to the present invention is configured to determine abnormal behavior of a battery cell by applying specific abnormal behavior determination criteria for each type of battery cell according to the type of positive electrode active material contained in the battery cell. , As a result, the charging and discharging operation is not interrupted unnecessarily during charging and discharging, which has the effect of improving the productivity and quality deterioration of battery cells.

100: Battery cell charging and discharging device
110: Sensing unit
120: memory unit
130: control unit
140: Charge/discharge unit
150: input unit

Claims (15)

A charging and discharging device that charges and discharges a plurality of battery cells,
A sensing unit configured to measure the voltage of a battery cell mounted on a charge/discharge device;
a memory unit configured to generate a battery cell charge/discharge profile that is a time-voltage graph of a battery cell to be charged and discharged, and to store the generated battery cell charge/discharge profile and a standard charge/discharge profile that is a time-voltage graph of a good battery cell;
A control unit configured to compare and analyze the battery cell charge/discharge profile with the standard charge/discharge profile, determine whether the battery cell behaves abnormally, and transmit a control signal to stop charging/discharging for the battery cell determined to behave abnormally. Contains,
The control unit,
(i) If the positive electrode active material contained in the battery cell is lithium iron phosphate, abnormal behavior is determined if condition 1 is satisfied,
(ii) When the positive electrode active material included in the battery cell is not lithium iron phosphate, a battery cell charging and discharging device configured to determine abnormal behavior if any one or more of conditions 2 and 3 are satisfied.
[Condition 1]
In the voltage section where the voltage of the battery cell is 3.4V or higher, the difference between the voltage of the battery cell and the voltage of the non-defective battery cell exceeds 60mV.
[Condition 2]
The difference between the voltage of the battery cell and the voltage of a good battery cell exceeds 20mV.
[Condition 3]
In the charge/discharge profile of a battery cell, there is a section where the voltage decreases as time increases.
In claim 1,
The control unit,
When the positive active material included in the battery cell is lithium iron phosphate, a charging and discharging device for a battery cell configured to determine that the battery cell is normal even if there is a section in the charging and discharging profile of the battery cell where the voltage decreases with increasing time.
In claim 1,
a charging/discharging unit configured to electrically connect to a plurality of battery cells and apply current;
A battery cell charging and discharging device including an input unit for inputting the type of positive electrode active material included in the battery cell to be charged and discharged.
In claim 1,
The standard charge/discharge profile is,
A battery cell charging and discharging device that measures the voltage of good battery cells at different times for a sample group made up of good quality battery cells, and is a graph that corresponds to the average voltage value of the sample group for each time period.
In claim 4,
The control unit,
A battery cell charge/discharge device configured to match the charge/discharge profile of the battery cell generated by the memory unit with the charge/discharge profile of the non-defective battery cell, and calculate the difference between the voltage of the battery cell and the voltage of the non-defective battery cell. .
In claim 1,
The sensing unit is a battery cell charging and discharging device configured to measure the voltage of the battery cell while the battery cell is being charged or discharged.
In claim 1,
It further includes a temperature sensor that measures the temperature of the battery cell,
The control unit is configured to correct the voltage difference according to the temperature difference when there is a difference between the temperature of the battery cell measured by the temperature sensor and the temperature when measuring the voltage for generating the standard charge and discharge profile. Charge/discharge device.
In claim 1,
The charging and discharging unit is,
A battery cell charge/discharge device configured to charge/discharge a battery cell under the same charge/discharge conditions as the charge/discharge conditions for a non-defective battery cell when collecting voltage data for acquiring the standard charge/discharge profile.
(S1) A process of measuring the voltage of a good battery cell over time while charging or discharging a good battery cell, and recording a standard charge/discharge profile, which is a time-voltage graph of the good battery cell;
(S2) A process of measuring the voltage of the battery cell to be charged and discharged over time while charging or discharging the battery cell to be charged and discharged, and recording a battery cell charge and discharge profile, which is a time-voltage graph of the battery cell to be charged and discharged;
(S3) comparing and analyzing the standard charge/discharge profile and the battery cell charge/discharge profile to determine whether the battery cell is behaving abnormally; and
(S4) includes a process of stopping charging and discharging of battery cells determined to exhibit abnormal behavior,
The above (S3) process is,
(i) When the positive electrode active material contained in the battery cell is lithium iron phosphate, if condition 1 is satisfied, abnormal behavior is determined,
(ii) When the positive electrode active material included in the battery cell is not lithium iron phosphate, a method of charging and discharging a battery cell that determines abnormal behavior if any one or more of Conditions 2 and 3 is satisfied.
[Condition 1]
In the voltage section where the voltage of the battery cell is 3.4V or higher, the difference between the voltage of the battery cell and the voltage of the non-defective battery cell exceeds 60mV.
[Condition 2]
The difference between the voltage of the battery cell and the voltage of a good battery cell exceeds 20mV.
[Condition 3]
In the charge/discharge profile of a battery cell, there is a section where the voltage decreases as time increases.

In claim 9,
The lithium iron phosphate is a method of charging and discharging a battery cell, wherein the lithium iron phosphate is a compound of the following formula (1).
[Formula 1]
Li _1+a Fe _1-x M _x (PO _4-b )X _b
(In Formula 1, M is any one or two or more elements selected from the group consisting of Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn and Y. and, x≤0.5)
In claim 9,
A method of charging and discharging a battery cell, wherein the positive electrode active material other than the lithium iron phosphate is a compound of the following formula (2).
[Formula 2]
LiNi _c Co _d M n _e M _f O ₂
(In Formula 2, M is at least one selected from the group consisting of Al, Ti, Mg, Zr, Y, Sr, and B, 0<c≤0.8, 0<d≤0.35, 0<e≤0.35 , 0≤f≤0.1)
In claim 9,
The above (S3) process is,
When the positive active material included in the battery cell is lithium iron phosphate, a method of charging and discharging a battery cell for determining that the battery cell is normal even if there is a section in the charge and discharge profile of the battery cell where the voltage decreases with increasing time.
In claim 9,
The standard charge/discharge profile is,
A battery cell charging and discharging device that measures the voltage of non-defective battery cells at each time period for a sample group composed of non-defective battery cells, and maps the average voltage value of the sample group for each time period.
In claim 9,
The above (S3) process is,
A method of charging and discharging a battery cell comprising matching the charge and discharge profile of a battery cell with the charge and discharge profile of a non-defective battery cell and calculating the difference between the voltage of the battery cell and the voltage of the non-defective battery cell.
In claim 9,
The (S2) process includes measuring the temperature of a battery cell during charging and discharging; and
When there is a difference between the measured temperature and the temperature in the process (S1), the method of charging and discharging a battery cell further includes a step of correcting the voltage difference according to the temperature difference in the charge and discharge profile of the battery cell.

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