KR20200054013A - Method for Detecting Battery Having Disconnection of Terminal - Google Patents

Abstract

The present invention provides a method for detecting a disconnected battery, which is a method for detecting a disconnected battery in which at least one of a positive electrode terminal extending from a positive electrode and a negative electrode of a secondary battery including a positive electrode, a negative electrode, and a separation film. After the complete discharge from a state of charge (SOC) 0 to SOC 2 in a state where no current is applied, based on the open circuit voltage (OCV) Vrest after rest of one or more minutes, the method for detecting a disconnected battery determined whether the disconnected battery is provided.

Description

Method for Detecting Battery Having Disconnection of Terminal}

The present invention relates to a method for detecting a disconnected battery in which the terminal is disconnected, and in particular, a method for detecting a battery in which the terminal is disconnected without disassembly and precision transmission equipment of the battery.

2. Description of the Related Art A secondary battery having high applicability according to a product family and having electrical characteristics such as high energy density has been widely applied to portable vehicles as well as electric vehicles (EVs) or hybrid vehicles driven by electric driving sources. This secondary battery is attracting attention as a new energy source for eco-friendliness and energy efficiency improvement, in that not only does not generate any by-products due to the use of energy, as well as a primary advantage that can dramatically reduce the use of fossil fuels.

In particular, among the currently applied secondary batteries, lithium secondary batteries developed in the early 1990s have higher operating voltage and significantly higher energy density than conventional batteries such as Ni-MH, Ni-Cd, and sulfuric acid-lead batteries using aqueous electrolyte solutions. It is spotlighted as an advantage.

In general, a lithium secondary battery is built in a battery case in a structure in which an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode is stacked or wound, and is formed by injecting a non-aqueous electrolyte therein.

At this time, the electrode terminals are formed to protrude from the positive electrode and the negative electrode, and they are connected in series or in parallel to form a battery module or battery pack, and they are used as a vehicle battery or power storage device.

On the other hand, in general, the determination of the quality pass or fail of the battery is DCIR (Direct Current Internal Resistance), which measures resistance by passing a constant current for about 10 seconds to 30 seconds from the shipping charge SOC 30 to SOC 60 together with the charge and discharge capacities. ) Method.

However, disconnection of the electrode terminals may occur in the process of manufacturing the secondary battery. According to the method, as shown in FIG. 1, the resistance in SOC 30 is very low, and the difference between the voltage between the normal battery and the disconnection battery is identified. It does not appear as clearly as possible, so it is not easy to distinguish the existing method.

That is, in the case of the single-wire battery, the contact resistance of the electrode terminal and the current collector to which the electrode terminal protrudes increases, but the difference is so small that it is impossible to discriminate by the method.

Nevertheless, when the electrode terminals are disconnected, a problem such as a significant decrease in performance occurs when assembling a battery module or a battery pack containing them. As a transmissive device, it was inevitable to select a very inefficient method in terms of process and cost, such as using CT or X-ray.

Therefore, when a disconnection occurs in the electrode terminal of the battery in the actual mass production process, there is a high need for a method that can distinguish between a normal battery and a single-cell battery in a non-destructive manner, but does not require additional process and cost.

The present invention aims to solve the problems of the prior art as described above and the technical problems requested from the past.

Specifically, the present invention is a non-destructive detection method capable of detecting a battery with a disconnected electrode terminal using an existing charging / discharging device without disassembling the assembled secondary battery or using precision transmission equipment. to provide.

According to an embodiment of the present invention for achieving this object,

The present invention is a method for detecting a disconnection battery in which at least one of a positive electrode terminal extending from a positive electrode and a negative electrode terminal extending from a negative electrode of a secondary battery including a positive electrode, a negative electrode, and a separator is disconnected.

Based on the open circuit voltage (OCV) V _rest after rest of at least 1 minute in a state where no current is applied after completely discharging from SOC (State of Charge) 0 to SOC 2, it is possible to determine whether a single-wire battery is present. do.

Specifically, the single-wire battery detection method,

(i) a discharge process of completely discharging the target secondary battery;

(ii) after the discharging step, an unattended step of restoring the target secondary battery for 1 minute or more in a non-current state; And

(iii) a detection step of determining whether a single-cell battery is present by measuring the voltage V (o) _rest of the target secondary battery after the leaving step;

Including,

In the detection process, the voltage V (b) _rest and the V (o) _rest of the target cell are restrained for at least 1 minute in a state in which no current is applied after the discharging process of the reference battery without disconnection at the positive and negative terminals. Perform by comparison.

Here, V (b) _rest and V (o) _rest are OCV values, respectively.

The inventors of the present application, according to the above method, do not require disassembly of a secondary battery or a precision transmission device, and SOC, which is a region with high current and high resistance from sudden IR-drop (voltage drop) occurring in the conventional charging and discharging process It was confirmed that, at a voltage around 0, the difference between the normal battery and the disconnected battery, which is recovered after the rest, can be used to determine whether the battery is disconnected by a simple method without increasing the process cost.

As described above, according to the single-wire battery detection method according to the present invention, even after assembly of the secondary battery, the secondary battery is not disassembled or a precision transmission equipment is used, and the non-destructive method is used using an existing charge / discharge device. It is possible to detect the secondary battery with the electrode terminal disconnected by the method, which is efficient in terms of cost and process.

1 is a graph of resistance according to SOC (state of charge);
2 is a flowchart of a single wire battery detection method according to an embodiment of the present invention;
3 is a discharge graph according to Experimental Example 1;
4 is a photograph of a negative terminal of a reference battery according to Experimental Example 1;
5 is a photograph of the negative terminal of the target cell 1 according to Experimental Example 1;
6 is a photograph of the negative terminal of the target cell 2 according to Experimental Example 1;
7 is a photograph of the negative terminal of the target cell 3 according to Experimental Example 1;
8 is a photograph of the negative terminal of the target cell 4 according to Experimental Example 1;
9 is a photograph of the negative terminal of the target cell 5 according to Experimental Example 1.

According to one embodiment of the invention,

A method of detecting whether at least one of a positive electrode terminal extending from a positive electrode of a secondary battery including a positive electrode, a negative electrode, and a separator and a negative electrode terminal extending from a negative electrode is disconnected,

Based on the open circuit voltage (OCV) V _rest after at least 1 minute rest in a state where no current is applied after completely discharging from SOC (State of Charge) 0 to SOC 2, it is determined whether a single-wire battery is present. A single cell detection method is provided.

Here, SOC is a term indicating the state of charge of the battery, and the state in which the battery is fully charged (fully charged) is SOC 100, the state of charge of 50% is SOC 50, and the state in which the fully discharged (fully discharged) is expressed is SOC 0. .

That is, the present invention performs a complete discharge to SOC 0, for example, SOC 0 to SOC 2, which is a region having a very large resistance, and then rests the battery to return to the voltage of the actual battery. In this case, it is possible to discriminate whether or not the difference between the voltage at the time of full discharge and the voltage after rest (ΔV) is different between the normal battery and the single-cell battery.

Specifically, a secondary battery has a difference between a voltage in a current flowing state during discharge and a voltage (OCV) in a non-applied state of the current. When the current is applied, the current I and resistance R ), That is, due to the voltage drop (IR-drop).

Therefore, in the case of a secondary battery having a different resistance, even if the battery is discharged to the same voltage, the OCV is different due to a difference in the resistance (R) value of each secondary battery.

At this time, a normal battery having no disconnection in the positive electrode terminal and the negative electrode terminal, and a disconnection battery having a disconnection in at least one of them, there is a difference only in the contact resistance, so it is not easy to distinguish according to the difference in resistance.

However, if the difference is determined by performing a rest after discharging to the vicinity of SOC 0, as shown in FIG. 1, in the SOC, the difference is remarkable, so that the difference between the normal battery and the single-cell battery is distinguished. It becomes possible.

Thus, the inventors of the present invention, after repeated in-depth research, in the phenomenon that the OCV value is changed when performing rest after discharging to the vicinity of SOC 0, which is a region having a large resistance, the SOC is shown in FIG. 1. As the resistance was very large, it was confirmed that the difference between the voltage change between the normal battery and the single-cell battery was prominent, and the secondary battery was disassembled and observed along with the change in the voltage graph. It was confirmed that this is possible.

Specifically, the single-wire battery detection method,

(i) a discharge process of completely discharging the target secondary battery;

(ii) after the discharging step, an unattended step of restoring the target secondary battery for 1 minute or more in a non-current state; And

(iii) a detection step of determining whether a single-cell battery is present by measuring the voltage V (o) _rest of the target secondary battery after the leaving step;

It may include.

The full discharge of the discharge process may be performed from 2.5V to 3.0V, and in detail, it may be performed up to a voltage appropriately selected according to the positive electrode material and the negative electrode material.

The leaving step is to leave the secondary battery in a non-current state at room temperature (24 to 26 degrees Celsius), where the SOC is maintained near SOC 0 in a fully discharged state.

The neglect process may be performed with a time sufficient for the voltage to return to the voltage of the actual secondary battery, and thereafter, errors may be reduced in detecting whether a disconnection occurs, and more clear detection may be performed, for example, 1 minute or more. It may be, and may be performed in more than 10 minutes in detail. However, it is not necessary to perform too long inefficiently, and it is sufficient to perform within 1 hour.

On the other hand, as described above, in the case of a normal battery and a single-cell battery, since there is a difference in the OCV after the stand-off process of the rest after full discharge, it is possible to detect whether there is a disconnection.

Specifically, in the detection process, the voltage V (b) _rest that is _rested for 1 minute or more in a non-current state after the discharge process with respect to a reference cell previously identified as a normal cell having no disconnection at the positive and negative terminals. Measurement, and can be performed by comparing the V (o) _rest of the target cell. That is, there is no disconnection of the terminal, and the voltage V (b) _rest , which has been _rested for 1 minute or more in the current unapplied state after the discharge process of the reference battery, which is proved to be a normal battery, is first measured, and thereafter, V of the target battery After measuring (o) _rest , the V (b) _rest value and the V (o) _rest value can be compared and examined to determine whether the target battery is a normal battery or a single-cell battery from the difference.

At this time, the detection process is determined based on the size of V (o) _rest -V (b) _rest , which may vary depending on the size of the current in the discharge process.

Therefore, in order to detect a single-wire battery, the user can arbitrarily set the current of the discharge process. Accordingly, a specific discharge current to be used for the detection method is more easily determined, and for the reference battery previously identified as a normal battery, based on the voltage change graph obtained by performing the above process once, the same discharge is applied to the target batteries afterwards. By performing the detection method step by step with a current value, it is possible to determine whether a plurality of batteries are disconnected. In this way, it is possible to quickly determine whether the battery is a single-wire battery by using an existing charging / discharging method without disassembling the battery or using a precision transmission device. Alternatively, the graph of voltage change of the reference battery can be based on this by referring to the existing literatures that disclose the same manufactured batteries.

Meanwhile, the discharging process may be performed with a constant current. At this time, when discharging is performed at a high C-rate, the resistance value in the vicinity of SOC 0 increases, resulting in a more rapid voltage drop, and thus, the actual secondary The error between the voltage of the battery and the voltage to be measured increases, and after applying no current, the OCV varies more greatly depending on the resistance value.

Therefore, the larger the discharge current, the clearer the distinction between the normal battery and the single-cell battery. Specifically, the discharge current of the discharge process can be largely set, but is not limited, for example, 1C or more, in detail, It may be 1C to 5C, more specifically 2C to 3C, and most specifically 3C.

From this, the detection process, as described above, when the discharge process is performed at 3C or more, specifically 3C to 5C, and more specifically, 3C, the voltage after the stand-off process of the reference and target cells (after rest) If the difference, V (o) _rest -V (b) _rest is greater than or equal to 0.05V, that is, V (o) _rest -V (b) _rest ≥ 0.05V, the target cell can be determined as a single cell. Can be.

More specifically, when the discharge process is performed at 3C or more, specifically 3C to 5C, and more specifically, 3C, the voltage difference after the neglecting process (after rest) of the reference cell and the target cell, V (o ) _rest -V (b) When _rest ≥ 0.07V, the target cell can be determined as a single cell.

In addition, prior to the discharging process of step (i), a charging process for charging the secondary battery may be further included.

The charging may be performed through a constant current-constant voltage charging process, such as a normal charging process of a secondary battery, wherein the current value and the voltage value may be appropriately set according to the battery.

The constant current section is performed by charging a constant current appropriately selected from the above range, and charging is performed with a constant voltage appropriately selected from the above range.

In this case, the time point of changing from the constant current section to the constant voltage section may be a time point when the set charging voltage is reached.

Charging of the secondary battery performed in this way may be performed up to full charging of SOC 98 to SOC 100.

Meanwhile, the charging process and the discharging process may be performed repeatedly, and the number of times is not limited, but the present invention has the purpose of detecting whether a wire is disconnected and can be performed only once.

Meanwhile, for a clearer understanding of the present invention, FIG. 2 is a flowchart illustrating an inspection procedure of a single-wire battery detection method according to the present invention.

Referring to FIG. 2, in step P1, the SOC of the target cell is about 100%, and is fully charged until SOC 98 to 100 are reached. Then, in step P2, the target cell is discharged, and the battery is completely discharged until the SOC reaches 0%, for example, SOC 0 to 2. In step P3, the target battery is left for at least 1 minute while no current is applied. Subsequently, the voltage (OCV, V (b)) when the voltage (OCV, V (o) _rest ) of the target cell is measured in step P4 and the reference cell that is identified as the normal cell in step P5 is performed in the same manner as described above. _rest ).

Thereafter, the difference value varies according to the discharge current performed in the process P1, but when the discharge current is performed at 3C or more, specifically 3C to 5C, and more specifically, 3C, the V (o) _rest -If V (b) _rest ≥ 0.05V, the target cell is judged to be a single-cell cell, and the inspection is terminated (process P6-1), V (o) _rest -V (b) _rest <0.05V, subject The battery is judged to be a normal battery, and the inspection is ended (step OCP6-2).

In the above, the V (b) _rest of the reference battery may be used as it was previously performed, or may be set with reference to the literature, or newly performed the above steps P1 to P4 on the reference battery before the inspection of the target battery You can also get the value.

In addition, the determination of the disconnection battery in step P6 may be different depending on the discharge current performed in P1, and the lower the discharge current, the difference in voltage magnitude determined by the disconnection battery, that is, V (o) _rest -V (b) _{Since the rest} value becomes small, the value can be set according to the discharge current.

On the other hand, the type of the secondary battery is not particularly limited, but as a specific example, a lithium ion (Li-ion) secondary battery having the advantages of high energy density, discharge voltage, output stability, lithium polymer (Li-polymer) ) It may be a secondary battery, or a lithium secondary battery such as a lithium-ion polymer secondary battery.

Since the specific configuration and structure are disclosed in the art, a detailed description is omitted in the present specification, and the present invention can be applied to all secondary batteries having a general structure disclosed in the art.

Hereinafter, description will be made with reference to examples according to the present invention, but this is for easier understanding of the present invention, and the scope of the present invention is not limited thereto.

<Production Example>

LiNi _1/3 Mn _1/3 Co _1/3 O ₂ positive electrode active material: conductive material (Super-P): binder (PVdF) in a weight ratio of 96: 2: 2 is added to the solvent NMP to make a slurry, and this is aluminum A positive electrode was prepared by coating on a foil with 70 μm, drying and pressing at 130 degrees Celsius.

Artificial graphite negative electrode active material: Artificial graphite conductive material (Super-P): Binder (PVdF) was added to NMP as a solvent in a weight ratio of 95: 2.5: 2.5 to prepare a negative electrode mixture slurry, which was then made to 70 μm on copper foil. A cathode was prepared by coating, drying and pressing at 130 degrees Celsius.

The positive electrode and the negative electrode, a polyethylene membrane (Celgard, thickness: 20 μm) as a separator, and a liquid electrolyte in which LiPF ₆ is dissolved in 1M in a solvent in which ethylene carbonate, dimethylene carbonate, and diethyl carbonate are mixed in a 1: 2: 1 ratio. Using, to prepare a secondary battery.

<Experimental Example 1>

The secondary batteries were sampled, and five were extracted to be used as target cells, and an experiment was performed to measure whether or not there was a disconnection.

In addition, among the secondary batteries made in the same manner as above, a secondary battery without disconnection was set as a reference battery.

After charging the reference battery and 5 target cells to SOC 100 at 1C up to 4.2V by the method of constant current-constant voltage (CC-CV), and completely discharging it to SOC 0 at 3C by the method of constant current (CC) , Was rested without current applied.

Then, the voltage change was measured from the discharge process of the reference and target cells to the rest.

The voltage at the time of full discharge is V _0, the voltage after 1 minute of rest is V _1.rest (reference battery: V (b) _1.rest , the target battery: V (o) _1.rest ), the voltage after 10 minutes of rest is V _{Let 10.rest} (reference battery: V (b) _10.rest , target battery: V (o) _10.rest ).

In addition, the batteries were disassembled to check whether the electrode terminals were disconnected.

The results are shown in FIGS. 3 to 9 and Table 1 below.

Decomposition V ₀ (V) V _1.rest V (o) _1.rest -V (b) _1.rest (V) V _10.rest V (o) _10.rest -V (b) _10.rest (V) Reference battery No disconnection 2.99986 3.28937 - 3.31923 - Target battery 1 No disconnection 2.99985 3.28679 -0.00258 3.31697 -0.00226 Target battery 2 There is disconnection 2.99991 3.36204 0.07267 3.39723 0.078 Target battery 3 There is disconnection 2.99978 3.38403 0.09466 3.42056 0.10133 Target battery 4 There is disconnection 2.99985 3.39182 0.10245 3.43357 0.11434 Target battery 5 There is disconnection 2.99995 3.38612 0.09675 3.42562 0.10639

First, FIGS. 4 and 5 are photographs in which the reference battery and the target battery 1 are disassembled to confirm the negative terminal. 4 and 5, it is confirmed that both the reference battery and the target battery 1 have the foil of the negative electrode tab in good contact with the welding portion of the lead portion, so that no disconnection occurs. In addition, referring to Table 1 and FIG. 3 (FIG. 3 is a graph showing a voltage change pattern in the discharge test of the reference cell and the target cells 1 to 5), the target cell 1 is V (o) _rest -V ( b) As the value of _rest became less than 0.7, it was confirmed that no disconnection occurred even by the detection method of the present invention, which was verified to be consistent with the result confirmed through the disassembly of the target cell 1 in FIG. 5.

On the other hand, Figures 6 to 9 is a photograph confirming the negative terminal by disassembling the target cells 2 to 5. Referring to these FIGS. 6 and 9, it is confirmed that the foils of the negative electrode tabs completely or partially separated from the welding portion of the lead part in the target cells 2 to 5, resulting in complete or partial disconnection.

In addition, referring to Table 1 and FIG. 3 (FIG. 3 is a graph showing a voltage change pattern in the discharge test of the reference cell and the target cells 1 to 5), the target cells 2 to 5 are V (o) _rest − As the value of V (b) _rest becomes 0.7 or more, it is confirmed that there is a disconnection even by the detection method of the present invention, which is consistent with the results confirmed through the decomposition of the target cells 2 to 5 of FIGS. 6 to 9. It was verified.

Accordingly, when the inspection was performed according to the present invention, it was confirmed that the normal battery and the single-cell battery were clearly separated only by the existing charge / discharge test, and that the battery could be reliably detected if the battery was disassembled and confirmed. do.

Although described above with reference to the drawings and examples according to the present invention, those skilled in the art to which the present invention pertains will be able to perform various applications and modifications within the scope of the present invention based on the above.

Claims (11)

A method for detecting a disconnection battery in which at least one of a positive electrode terminal extending from a positive electrode of a secondary battery including a positive electrode, a negative electrode, and a separator and a negative electrode terminal extending from a negative electrode is disconnected,
Based on the open circuit voltage (OCV) V _rest after 1 minute or more of rest in a state where no current is applied after completely discharging from SOC (State of Charge) 0 to SOC 2, it is determined whether a single-wire battery is present. Single-cell detection method. According to claim 1,
The single-wire battery detection method,
(i) a discharge process of completely discharging the target secondary battery;
(ii) after the discharging step, an unattended step of restoring the target secondary battery for 1 minute or more in a non-current state; And
(iii) a detection step of determining whether a single-cell battery is present by measuring the voltage V (o) _rest of the target secondary battery after the leaving step;
A single-wire battery detection method comprising a. According to claim 2, The detection step, the voltage of the reference battery without disconnection to the positive electrode terminal and the negative electrode terminal, the voltage V (b) _rest rested for 1 minute or more in the current unapplied state after the discharge process, and the target cell V (o) _rest is performed by comparing the one-wire battery detection method. The method of claim 3, wherein the detection process is determined based on the size of V (o) _rest -V (b) _rest , the size of which varies depending on the size of the current in the discharge process, and When the discharge process is performed at 3C or more, when V (o) _rest -V (b) _rest ≥ 0.05V, the target cell is determined as a single cell, and the single cell detection method. The method according to claim 4, wherein when the discharge process of the reference battery and the target battery is performed at 3C or more, when V (o) _rest -V (b) _rest ≥ 0.07V, the target battery is determined as a single-cell battery, disconnection. Battery detection method. According to claim 2,
The discharge process is performed with a constant current, a single-wire battery detection method. The method of claim 1 or 2,
The full discharge is performed to 2.5V to 3.0V, single-cell detection method. The method of claim 2, further comprising a charging process for charging a secondary battery prior to the discharging process. The method of claim 8, wherein the charging is performed through a constant current-constant voltage charging process. 10. The method of claim 9, wherein the change from the constant current section to the constant voltage section is made at the time when the set charging voltage is reached. The method of claim 8, wherein the charging is a full charge of SOC 98 to SOC 100.

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